Post-Harvest Seaweed Review PDF

Seaweeds Seaweeds or benthic algae are naturally abundant in Philippine waters and have become an essential part of the Filipino diet for many years. Seaweeds have also been utilized as medicine, fertilizer and animal feeds. Seaweeds are generally classified into four major classes on the basis of t...

Seaweeds Seaweeds or benthic algae are naturally abundant in Philippine waters and have become an essential part of the Filipino diet for many years. Seaweeds have also been utilized as medicine, fertilizer and animal feeds. Seaweeds are generally classified into four major classes on the basis of their pigments: Chlorophyceae - green algae Cyanophyceae - blue-green algae Phaeophyceae - brown algae Rhodophyceae - red algae Fish Processing Technology in the Tropics J. Espejo-Hermes (2004) 153 Minor Aquatic Products The green and blue-green algae usually grow in fresh water while the brown and red algae (usually referred to as seaweeds) are found almost exclusively in marine habitats. The brown and red algae are of commercial value to the fishing industry. Fig. 28 shows some of the common seaweeds of the Philippines. 13.1.1 Nutritive Value of Seaweeds The main components of seaweeds are carbohydrates, such as saccharides and cellulose, proteins and minerals. Seaweeds also contain lipids and vitamins. Their carbohydrates consist of large amounts of mucopolysaccharides. The protein content of some seaweeds can be high; for instance, in dried laver (Porphyra tenera), where the protein content can reach 34-40% which is comparable to the protein content of soybean. Seaweeds are also relatively rich in vitamins and minerals (Table 14). Almost all kinds of seaweeds have high levels of vitamins A, B1 (thiamine), B2 (riboflavin), C (ascorbic acid) and niacin. Furthermore, seaweeds contain 7-34% by volume of minerals; among these are calcium, sodium, magnesium, potassium, phosphorus, sulphur, iodine and iron. Table 14. Nutritional Value of Edible Fresh Seaweeds Scientific Name (Local Name) Component Protein (%) Moisture (%) Fat (%) Ash (%) Ca (mg) K (%) Iron (mg) Vit. B2 (mg) Acanthophora specifira (kulot) 0.26 96.26 0.11 0.85 123.96 1.92 16.81 0.01 Caulerpa racemosa (lato) 0.10 96.70 0.10 1.00 29.00 - 18.00 0.01 Enteromorpha intestinalis (lumot) 0.26 95.49 0.01 1.76 123.61 6.27 - - Hydroclathrus clathratus (balbalulang) 0.40 88.30 0.30 6.40 649.00 - 44.50 Tr Gelidiella acerosa (kulot) 1.84. 82.16 0.26 3.33 415.61 27.54 - 0.07 Gracilaria verrucosa (gulaman-dagat) 0.94 90.70 0.07 1.88 131.06 9.72 - 0.03 Halymenia durvillaei (gayong-gayong) 0.26 96.46 0.11 0.59 90.03 21.95 0.65 0.21 Source: Espejo-Hermes (1985); FNRI (1997) 154 Minor Aquatic Products Fig. 28. Common Seaweeds in the Philippines 155 Minor Aquatic Products 13.1.2 Uses of Seaweeds 13.1.2.1 Food For some thousands of years, seaweeds have been highly valued and widely consumed as a direct human food in the oriental countries. In the Philippines during the pre-Spanish era, the coastal inhabitants used to gather seaweeds to supplement their daily diet. The development of transportation in the mid-Spanish period marked the commercialization of seaweeds as food or as agar source (Velasquez, 1977). Edible seaweeds are consumed mainly as vegetable salad. Among the species commonly used as food are kulot, Acanthopora spicifera; lato, Caulerpa racemosa, pupuklo, Codium muelleri; gulaman-dagat, Gracilaria spp; and balbalulang, Hydroclathrus clathratus (Bersamin et al., 1970). 13.1.2.2 Animal Feeds Meals from brown seaweeds (Ascophyllum and Laminaria) are rich sources of minerals, vitamins and trace elements for animals. Incorporation of seaweed meal in sheep feeds has been reported to improve the fertility though with less marked effect than with supplement of herring meal. Ten to 20 percent of seaweed meal mixed in the conventional feeds is found applicable. Seaweed meal supplement in poultry rations could improve feed consumption, body weight and pigmentation in broiler chicks (Pantastico and Alejar, 1976). The use of algae as fresh food for fry and fingerlings of prawns and fishes has been studied at the Aquaculture Department of SEAFDEC (Pantastico et al., 1990). Sargassum seaweeds from the Philippines are exported for animal feed. 13.1.2.3 Fertilizers Seaweeds have been applied for centuries to the land as a direct and simple means to fertilize the soil. Brown algae such as Macrocystis and Ascophyllum are mainly used as fertilizer. Their value as a fertilizer derives not so much from their nitrogen, phosphorus and potassium contents but rather from their unusual properties as a soil conditioner and growth promoter. Liquid seaweed manures also appear to promote resistance to plant diseases and plant pests, induce fruit bearing and increase germination rates. Aqueous extracts from Sargassum polycystum and Hydroclathrus clathratus increased the growth of plants such as corn and mung beans (Montaño and Tupas, 1987). A foliar spray from seaweeds could also increase the growth and yield of legume plants (Tupas and Montaño, 1987). A concentration of 5000 ppm foliar 156 Minor Aquatic Products spray on the crops during the second and fourth week of growth was used. In 1988, Guerrero reported on the efficiency of Algafer LPF (liquefied plant food) Plus, a foliar fertilizer derived from seaweeds. Algafer contains growthpromoting plant hormones (auxin and gibberellin) and some micronutrients. Tests on field crops showed yield increase from 18-40% of the original harvest. Algafer is a complete fertilizer due to its NPK (nitrogen, phosphorus and potassium) content of 11-3-4. The by-products or water extracts from the extraction of seaweed named Algro contain growth-promoting hormones which can be used as fertilizers (Montaño, 1996). Seaweeds such as Sargassum, Eisenia and Ecklonia are also used. They are simply dried, ground and used as potassium fertilizer. 13.1.2.4 Commercial Use The main commercial value of seaweeds lies in the products derived from them (phycocolloids) which have the ability to form gels and colloidal suspensions. The principal colloidal products made from seaweeds are agar, alginates or alginic acid and carrageenan. These products are used in foods, pharmaceutical and industrial materials. Agar (Gulaman) Agar is extracted from red algae, particularly from Gelidium, Pterocladia and Gracilaria. Locally, Gracilaria is the principal source of agar. Agar is insoluble in cold water but soluble in boiling water. Other properties of agar include (Renn, 1990): λ gel formation at low concentrations λ low reactivity with other molecules λ low degree of hysteresis (melting-gelling point difference) λ resistance to common microbial degradation λ ability to retain significant amounts of water Agar consists mainly of non-digestible carbohydrates hence it provides the human body with practically no calories when served without sugar. A bar of gulaman consists of 74.5% carbohydrates; 17% moisture; 2.6 % protein; 0.3% fat and 4.7% ash. It is rich in minerals, especially iodine. The industrial uses of agar include the following: thickener, emulsifier, gel-forming agent, absorbent, lubricant, inert carrier and as bacteriological culture media. 157 Minor Aquatic Products Agars are usually classed into food grade, microbiological grade and sugar-reactive agars. Although the local production of agar as food (gulaman bars) has been a traditional industry, several institutions (UP Marine Science Institute, Industrial Technology and Development Institute of the Department of Science and Technology, and Xavier University) in the country have developed better processing methods to produce microbiological grade agar from local Gracilaria (Montaño, 1996). Sugar-reactive agars applicable to bakery and confectionery products can be extracted from Gracilaria lemanaeformis, G. fisheri, G. firma and G. eucheumoides (Montaño et al., 1995). Alginates Alginate is the general term designating the water-loving (hydrophilic) derivatives of alginic acid. Sources of alginates are Macrocystis and Laminaria. Locally, Sargassum seaweeds are good sources of alginates. Highest alginate yield of 21-23% was obtained from Sargassum spp. gathered from Calatagan, Batangas during the months of September to October. This yield coincided with the maximum growth of the plants at 89-98 cm (Ang, 1984). One of the most important uses of alginates as stabilizer is to give smooth body and texture to ice cream. They also have innumerable uses in food, pharmaceutical, cosmetic and industrial fields. The alginate products include sodium, ammonium and calcium alginate. Carrageenan The name "carrageenan" was originally applied to the polysaccharide from red seaweeds such as Chondrus crispus (Irish moss) and Gigartina stillata. However, the name also refers today to the extracts from other red seaweeds such as Eucheuma and Iridea. An estimated 70-80% of the world's production of carrageenan is derived from Eucheuma. Presently, the Philippines ranks as the fourth largest carrageenan producer in the world. The country has developed processing technologies to produce Philippine natural-grade (PNG) carrageenan and refined carrageenan. At present, there are nine processors of semi-refined carrageenan and two processors of refined carrageenan in the country (Philippine Daily Inquirer, 1997). Evaluation of physico-chemical properties of Philippine semi-refined carrageenan showed that it could be used in food formulations if proper control of the unit processes and operations involved in its manufacture are applied (Montaño et al., 1985). Carrageenan is used primarily in non-settling chocolate milk drinks and other foods as well as in various pharmaceutical products such as hand lotions 158 Minor Aquatic Products and toothpaste. Very recent developments showed that carrageenan plays a role in health maintenance by lowering the glucose level in the blood, which is significant for diabetic individuals. Additionally, carrageenan has the potential to eliminate poisons from the body system such as saxitoxin (red tide toxin) by binding with the toxin (Montaño, 1996). Other new applications of carrageenan in the industry include: λ as an additive in bakery products (fortifies fiber in bread; replaces potassium acid tartrate or cream of tartar in meringue) λ as a base for candy products (pastilles, fruit-flavored candy gels), air deodorizer, soap, shampoo and suppositories λ as a fat substitute in foods (e.g., in locally made sausages, "longganisa" 13.2 Fish Oils Fish oils are obtained from certain species of fish or from the waste materials from the processing of fish. Some of the bony fishes such as mackerel and herring have practically all of their fat distributed in their muscle tissue but very little in their relatively small livers, while sharks, rays and skates, in general, have large oily livers that may comprise 10-15 % or more of their body weights (Brody, 1965). A developing industry in the country is the extraction of fish oils from carp for the production of health soap and other cosmetic products. 13.2.1 Composition of Fish Oils Fish oils are mainly esters of fatty acids and glycerol or triglycerides, which as the name implies are three fatty acids attached to a glycerol molecule (Fig. 30). The general characteristics of fish oils: λ 25% of saturated fatty acids such as palmitic acid (C16H32O2 ), stearic acid (C18H36O2 ) and myristic acid (C14H28O2 ) occur widely in fish oils; 75% are highly unsaturated fatty acids with oleic acid (C18H34O2 ) as the major component Fig. 30. Diagrammatic Structure of a Triglyceride 164 Minor Aquatic Products λ the unsaturated fatty acids of fish oils vary substantially in chain length. Most of the unsaturated fatty acids belong to the C16, C18, C20 and C22 series λ unsaponifiable components (Vitamins A and D, cholesterol, ethers and hydrocarbons) vary considerably λ relatively high amount of cholesterol in fish liver oils; fish body oils have a low cholesterol content λ higher complexity in glyceride structure (the fatty acid components of fish oils are highly unsaturated and long chain) compared to that of land animal fats and vegetable fats 13.2.2 Extraction of Fish Oils 13.2.2.1 Fish Body Oil Wet Reduction Process Fish body oils are generally extracted from whole fish or fish offal by the wet reduction method. This method is suitable for the extraction of oil from herring or from canning offal which have high oil content. The basic steps in the wet reduction process consist of grinding, cooking with live steam, and pressing which are usually carried out simultaneously with fish meal production. When small fish are used, grinding is omitted. The pressing operation separates the cooked fish from the press-liquor. The press-liquor is used for the manufacture of fish body oils and fish solubles as well as for the recovery of suspended solids in the liquor (Windsor and Barlow, 1981; Brody, 1965). Solvent Extraction This process is relatively expensive because of the solvents used for extraction. Besides, the extracted oil is darker in color than oils produced by the wet-reduction process regardless of the raw material quality. Dry Reduction Process The dry reduction process is applied principally to the processing of nonoily types of fish. If there is enough oil to make oil recovery feasible, the oil is extracted from the raw fish using a hydraulic press. 165 Minor Aquatic Products 13.2.2.2 Liver Oil Direct Steaming Process This is the simplest process for the extraction of liver oils. Basically, it involves direct heating of livers with steam at low pressure, piped into the cooker. The process results in the rupture of the liver cells, which releases the oil. Heating at 85oC to 89oC is continued until the livers disintegrate and release the oil. The supernatant oil is skimmed off, filtered and transferred into a settling tank or, preferably, centrifuged to remove suspended solids and moisture. If the livers are heated in a steam-jacketed kettle, instead of by direct steam, they should be mechanically stirred to facilitate disintegration; heating temperature should only be between 70oC and 75oC. Solvent Extraction Method The process involves an initial step of autoclaving the material which tends to break it up, as well as reduces its moisture content, followed by a drying step. The disintegrated and dehydrated product allows better penetration and wetting by the solvents. It also allows, subsequently, better recovery of the solvent from the solid particles. For economic reasons, the solvent and oil solution should be as concentrated as possible before it is subjected to distillation. The advantage of employing the solvent extraction method is that the liver tissues tend to disintegrate and coagulate uniformly, resulting to better recovery of oil. The disadvantages of all solvent extraction methods are as follows: λ Dark reddish color, increased viscosity and foreign odors are imparted to the extracted oils by the solvents. λ Alkali refining treatment is required since the free-fatty acids in the oils remain untouched. λ Solvents must be free from impurities such as peroxides which tend to hasten the oxidation of the acids, thereby shortening their keeping qualities. λ Occurrence of oxidation and loss of Vitamin A due to elevated temperature for prolonged periods required for the complete removal of solvents. λ Cost of production is relatively higher than other methods. 166 Minor Aquatic Products Enzyme Digestion Method The livers are minced or disintegrated and digested by commercial proteolytic enzymes such as pepsin and biophrase from Bacillus subtilis. The digested liquor is first passed through a continuous solid separator and then passed through a centrifuge. The yield of liver oils using this method is high. Alkali Digestion Method The recovery of oil and subsequently Vitamin A is high using this method. The livers are first ground in a meat chopper and digested at 40-50oC by autolytic enzymes after the addition of water until the solids of the liver are liquefied. The calculated minimum amount of caustic soda solution (sodium hydroxide) added is between 1-2% for shark livers, the digestion is continued at 40- 80oC. The pH of the alkali-digested liquor should be adjusted to approximately 9 with hydrochloric acid or sodium hydroxide solution. The digest is then centrifuged. Acid Ensiling Method The livers are washed, cut into pieces and put in bottles. Formic acid is added and the mixture is incubated at room temperature for four days with agitation once a day (Sumpeno and Sutijana, 1990). After fermentation, the liver mixture is centrifuged and the supernatant layer is carefully decanted. Anhydride sodium sulfate crystals are added to the supernatant layer, then filtered. 13.2.3 Uses of Fish Oils 13.2.3.1 Fish Oils in Nutrition Human and Animal Foods Fish oils are utilized as hardened oils in margarine and shortening. Fish oils are normal constituents of many animal feeds, which often contain fish meal as protein source. 13.2.3.2 Medical and Pharmaceutical Fish oils are the common sources for the medicinal fat-soluble Vitamins A, D, and E. Fish oils contain particularly high amounts of Vitamin A as shown in several species of fish analyzed locally (Table 15). Fish oil, with its high level of unsaturated fatty acids has been known to reduce blood cholesterol levels (refer to Chapter 1 for more information). Fish oils are converted into capsules (as a source 167 Minor Aquatic Products of squalene and omega-3-fatty acids) or incorporated in the manufacture of health soaps and other cosmetic products. Table 15. Vitamin A Potency of Fresh Liver Oils in Selected Philippine Fishes Fish Common and Scientific Names Oil Content (%) Vitamin A International Units/ per g oil Threadfin bream (Nemipterus spp) 13.28 24,870 Trevally/Jack (Caranx spp) 5.88 86,740 Milkfish (Chanos chanos) 7.62 18,085 Spanish mackerel (Scomberomorus commerson) 11.33 6,249 Tenpounder (Elops hawaiiensis) 30.86 22,969 Rabbitfish/Siganid (Teuthis spp) 6.62 43,666 Adapted from Bersamin et al. (1975) 13.2.3.3 Industry The industrial uses of fish oils generally include soaps and detergents, painting materials, floor covering and oil cloth, printing inks, factices in rubber manufacture, lubricants, insecticides and cosmetics. 13.2.4 Technical Problems in Fish Oil Production Fish oils may deteriorate before and during processing or during storage. These deteriorative changes may be chemical (rancidity) or biochemical (enzymatic) in nature or microbial causing fermentation or putrefaction of the liver tissue proteins. Spoilage of fish oils manifests itself by the formation of rancid odors and flavors. Oxidative rancidity is largely responsible for loss of Vitamin A potency, and the development of off-flavors. Harmful effects may result when animals ingest deteriorated fish oils (Stansby, 1967). The deterioration of fish oils can be controlled by using antioxidants, employing inert atmosphere such as nitrogen gas in packaging of the product and/ or inactivation of enzymes by heat. Naturally-occurring antioxidants, which are 168 Minor Aquatic Products present in animal and vegetable tissues, such as tocopherols, phosphatides and ascorbic acid, may be used. 13.2.5 Shark Oil Processing The process of extracting shark liver oils as described below makes use of the direct steam process. Shark liver contains considerable amounts of oil. The process shown below is based on the Mindanao Marine Products method in Ozamis City (Fig. 31). Materials and Equipment shark liver steam kettle generator metal cylinder perforated metal tube Procedure (UP ISSI, 1974) 1. Place the shark liver in a perforated metal tube. 2. Encapsulate the metal tube with the liver in a high conductive metallic cylinder, preferably stainless steel or copper. 3. Place the metallic cylinder in a steam kettle generator (capacity around 210 liters) with water the amount of which is proportional to the cylinder capacity. The steam will heat the liver through the perforations by induction. 4. Drain the oil from the cylinder from time to time. 13.2.6 Squalene Squalene is an acyclic hydrocarbon (C30H62) found in shark liver. Dr. Mitsumaru Tsujimoto at the Tokyo Industrial Testing Station in 1906 coined the name "squalene" after discovering its abundance in deep-sea sharks belonging to the Squalidae family. Species of sharks belonging to the family Squalidae contain high amounts of unsaponifiable substances, mostly in the form of squalene (Kreuzer and Ahmed, 1978; Sumpeno and Sutijana, 1990). Squalene is important commercially in the production of health products and cosmetics such as skin rejuvenators. It is believed that regular use of squalene supplements in the diet can make the body healthy by supplying the cells with oxygen. It is also claimed to promote better bowel movement, suppress stress hormones, counteract low density lipoprotein (bad cholesterol) and improve skin and hair growth. 169 Minor Aquatic Products Fig. 31. Shark Oil Processing 170 Minor Aquatic Products The procedure presented below is based on a laboratory scale but can be modified for commercial scale operation. Materials and Equipment shark liver formic acid sodium sulfate crystals (anhydride) petroleum benzene ethanol distilled water potassium hydroxide solution (28 N) nitrogen gas filter paper separatory funnel Erlenmeyer flask centrifuge column chromatography (fluorisil beads) vacuum dryer plastic bottles Procedure (Sumpeno and Sutijana, 1990) 1. Cut shark livers (1 cm3 size) and put in plastic bottles (200 g each). Add 0.5-4% formic acid with 0.5% gradual increment in triplicates. 2. Incubate the liver-acid mixture at room temperature for 4 days. 3. Centrifuge the fermented mixture at 2000 rpm for 10 minutes. 4. Decant the supernatant layer carefully and put in a flask containing 10 g of anhydride sodium sulfate crystals. Filter. 5. Put 5 g of liver oil in a flask then add 3 ml of potassium hydroxide solution and ethanol. Heat in a water bath for 30 minutes with frequent mixing. Cool the mixture to 40oC. 6. Add 50 ml petroleum benzene, 20 ml ethanol and 40 ml distilled water. Transfer the mixture into a separatory funnel. 7. Mix rigorously for about 10 minutes then allow the mixture to settle. 8. Transfer the upper layer into another separatory funnel containing 20 ml distilled water. Re-extract the bottom layer with 50 ml petroleum benzene. 9. Add the upper layer of the re-extracted portion to the upper layer of the first extraction. Discard the bottom layer. 10. Wash the extract twice with 20 ml distilled water, then treat the washed extract with mild alkali. Wash the extract with 20 ml distilled water until an alkali-free extract is obtained. 11. Transfer the extract in a flask containing 1.5 g anhydride sodium sulfate crystals. Filter using filter paper. 171 Minor Aquatic Products 12. Put the filtrate through a column chromatograph containing fluorisil beads. (The height of the column is 10 cm with a diameter of 1 cm; adjust the eluent velocity to about 1 ml/min.). 13. Evaporate the eluent in a vacuum chamber. Remove the remaining solvent using nitrogen gas. 13.3 Shark Fin Sharks are threatened species due to their low reproductive rate, hence their harvest should be regulated. Shark fins are one of the world's most expensive fishery products. The dried fins can fetch around US\$50-\$100 per kilogram (Subasinghe, 1992b). The most important marketing centers for shark fins are Hongkong and Singapore. The commercial value of shark fins depends on their natural color, size, thickness and the content of fin rays or fin needles. Majority of sharks have commercially valuable fins. The most important species are hammerhead shark (Sphyrna spp.), Mako shark (Isurus spp.), and blue shark (Prionace glauca). Other sources of commercial fins are thresher shark (Alopias vulpinus), white or black tipped shark (Carcharhinus spp.), white shark (Carcharodon carcharias), sharp nosed or yellow dog shark (Scoliodon spp.), tiger shark (Galeocerdo cuvier) and shovel nose or guitar fish (Rhinobactus spp). Fig. 32 illustrates the shark fins with commercial value. The most valuable are the first dorsal fin, the pair of pectoral fins and the lower part of the tail. There are several market forms of shark fins: fresh, chilled, frozen and dried or processed (including dried prepared fins, wet fin needles and fin nets). 13.3.1 Processing Fresh/Chilled/Frozen Fins The fins are cut off from the body as soon as the shark is captured. Fins from sharks over 1.2-1.5 m in length are used for processing. Care should be taken to reduce the amount of meat left on the fin by removing the fin just where the strands of fin rays start. Half-moon cut pectoral and dorsal fins (Fig. 33) are highly preferred by processors because very little meat is retained resulting to a more desirable finished product (Lai, 1983). 172 Minor Aquatic Products Freshly cut fins have to be cleaned well by scrubbing away any dirt or adhering materials and washing them thoroughly in fresh or seawater. If shark fins are to be marketed in the fresh or wet form, cleaned fins may be kept in ice for many days. The fins may be re-iced if needed. Fresh fins can keep longer if frozen. Fig. 32. Shark Fins with Commercial Value (Source: Subasinghe, 1992b) 173 Minor Aquatic Products Dried Fins The cleaned fresh fins may be dried under the sun. Some processors recommend the sprinkling of salt on the cut ends of the fins. However, excess salt has to be washed away before sun drying. Drying of fins can be started on board the boat, if the fishing operations are long. During the drying process, particularly when using trays or mats, the fins must be turned regularly to attain uniform drying and to prevent curling or burning. Drying of shark fins may take seven to 14 days, depending on the thickness of the fin. This drying period can result to satisfactorily dried fins with moisture content of 10-15 per cent. The Codex Standards requires moisture content not exceeding 18 per cent. Shark fins which are properly dried will produce a characteristic sound when tapped against each other. Grading of Dried Fins Traditionally, shark fins are marketed as fin sets. The grading of fin sets is based on species or the color of the skin such as black or white. In general, white Fig. 33. Methods of Cutting Shark Fin (Source: Subasinghe, 1992b) 174 Minor Aquatic Products fins fetch a higher price than black fins. The fins can be further graded according to size. Moisture content, smell and the type of cut can also influence the grading of dried fins. When shark fins are marketed in big quantity, the traders expect the shipment to have around 50 % pectoral fins, 25 % dorsal fins and around 25% caudal fins. Shark fins from the ventral and anal portions, and from small sharks are sold as mixed dried fins. Modern day exports are chiefly graded by the type, size and color, either black or white. The size of a fin is measured either on the length of the base of the fin or the distance between the center of the base and the tip of the fin. Based on the size, fins are graded as extra-large (40 cm and above), large (30-40 cm), medium (20-30 cm), small (10-20 cm), very small (4-10 cm) and mixed or assorted. Packaging and Storage Dried fins are packed as per requirements of the purchaser, either in cartons, wooden cases or gunny sacks. The use of gunny sacks is preferred by buyers as it allows the product to "breathe" Airtight packaging tends to develop a high humidity within the container which can result in the quality deterioration of the dried fins. In general, higher-grade fins are packed in 25-kg bags while the mixed or lower grades are shipped in 50-kg sacks. Processed Fins Softening The processing of fins starts with the softening of fins by soaking in water for eight to 10 hours. If the starting material is frozen, proper thawing of the fins must be done before soaking in water. Sun dried fins must be soaked for 16-24 hours. After the initial soaking, the fins are further soaked in warm water (80- 90oC), until the scales and skin are loose or soft. Cooking or water bath heating of the fins must not be done so as not to damage the texture of the fin rays. Descaling, Skinning and Removal of Meat After softening, the fins are transferred to a bucket of chilled water; the scales and the skin are then carefully removed using a wire brush. The fins are washed again in fresh water. Careful removal of the meat attached to the fin and the cartilaginous base plate are done and the fins are washed thoroughly in running water. 175 Minor Aquatic Products Bleaching The mere washing of the fins to remove blood in the cartilaginous base sometimes poses a problem to the processor. Treatment of the fins with 3% hydrogen peroxide for approximately 30 minutes (the duration of treatment depends on the type of bleaching agent used) is recommended by some processors to bleach the blood at the base of the fin. Thorough washing of the treated fins must be done afterwards to remove any residual bleach. Drying The fins are dried under the sun on racks for four to six days. The fins must be turned over regularly to attain uniform drying and to prevent curling. Too high temperatures could result to burning and browning of the fins. For proper control of drying, a mechanical dryer may be used. At this stage, the fin retains its original shape. Removal of varying amounts of base cartilage and cartilaginous tissue between the two layers of fin rays from the larger, more valuable fins is often done by the processors. Complete separation of the two layers of fin rays into two bundles prior to sun drying of the fin could also be done. Fin Needles Further processing of the processed fins into fin needles or fin nets is often included. The processed fins are initially softened by soaking in water for up to 12 hours, then boiled in water for about five to 10 minutes. Boiling is done to ease the removal of bundles of needles which now stand prominently as a result of expansion due to absorption of water, and to remove the membranous sheath covering the bundles of needles. Subsequently, the fins are put in chilled water and the base of the fin strands are kneaded and softened by hand to separate the fin needles from the membrane. All remaining membrane tissue is removed from the fin needles. The fin needles may be removed in the wet form as wet fin needles or may be further processed to fin nets. Fin Nets Fins nets are normally processed from small fins, lower-grade fins and fin assortments. Wet fin needles are first washed then arranged into fin nets at around 100 grams each and sun dried. Bleaching of the wet fin nets prior to sun drying may be done. The process may be carried out by putting the fin nets for 20 minutes in a special chamber where sulphur is burned beneath the trays. Bleaching by this method also helps to protect the product from insect attack. Sun drying of the fin nets follows. 176 Minor Aquatic Products 13.3.2 Defects in Dried Shark Fins Defects in dried shark fins include blemishes, defective cuts, burns, curling and insect infestation. Bad handling and delay in the removal of the fins cause blemishes. Defective cuts occur when the cutting of fins is not done properly (crude cutting) thus resulting to excess flesh remaining on the fins. Burns are due to prolonged exposure to the sun or improper control of temperatures when using mechanical dryers. The fins may attain deep and hard furrows. Curling of dried fins can also occur when the fins are exposed to uneven drying. During storage, mites may attack dried fins. 13.4 Jellyfish Jellyfish, which are close relatives of corals and sea anemones, seasonally appear in swarms in many tropical and temperate waters. The body of most jellyfish is a hemispherical saucer-shaped transparent bell or "umbrella" with a slight bluish tinge, bounded with many fine marginal tentacles (Fig. 34). The mouth of the jellyfish is found on the under surface of the "umbrella" which is protected by four oral arms. The water content of jellyfish is around 96-97%, hence it easily spoils. At the early stage of decomposition of jellyfish, the body surface becomes slimy and the transparent body develops a slightly pinkish color which is often accompanied by a slight off-odor. Processing of jellyfish needs to be carried out soon after landing because the previously mentioned changes set in within a few hours after catching. If possible, processing must commence while the jellyfish is still alive. For short-term preservation of jellyfish after landing, the use of sea water containing 1-2% alum (potassium aluminum sulfate) is recommended by some processors. There are at least five commercially exploited jellyfish species in the East and Southeast Asian regions (Subasinghe, 1992b). It is believed that the Chinese pioneered the processing of jellyfish for food. Among the jellyfish consuming countries are China, Korea and Japan. 177 Minor Aquatic Products Fig. 34. Structure of a Jellyfish (Source: Subasinghe, 1992b) 13.4.1 Processing The traditional (Chinese) processing method consists of a step-wise lowering of the water content of the jellyfish using a mixture of salt and alum. For processing, only the "umbrella" is used; although in the case of big jellyfish, the oral arms (legs) are also processed separately, resulting in products with lower commercial value. The average yield of "umbrellas" from whole jellyfish is around 60-65 % (Subasinghe, 1992b). Preparation of Raw Material Prior to processing, the oral arms and intestines are separated from the "umbrella". The "umbrellas" are cleaned, uncurled and flattened. The edges are trimmed using bamboo knives to avoid damage to the surface of the "umbrella", then they are washed and again cleaned in a dilute (3 percent) salt solution or seawater before processing. Any stains or remaining mucus during this process must be removed completely. First Salting The cleaned "umbrellas" are sprinkled with salt containing 10% alum (about 1 kg of salt/alum mixture for 8-10 kg material). The salted "umbrellas" are piled in cement tanks (1-1.5 m deep) and are left for a day in the tanks. During this process, the jellyfish lose about 35-40% of their water content. In the "wet" method, a solution of salt/alum is used with the addition of bleaching powder to improve the color of the jellyfish. The pH is then maintained between 3.5-4.5 by the addition of lime. 178 Minor Aquatic Products Second Salting The "umbrellas" are strewn with salt containing 8% alum, around 1 kg salt/alum mixture for 10 kg jellyfish. The salted product is piled in a fresh tank and left for three to four days. Third Salting The salted jellyfish is again salted with 6-7% alum, piled in a fresh tank and then left for five to six days. The oral arms (commonly known as legs) of large animals are treated this way since they too have a commercial value, although lower than that of "umbrellas". Fourth Salting The tanks are either drained or the salt water is pumped out after the third salting. Saturated salt solution (20-25o Baume) is filled into the tanks, then the jellyfish is left in this medium for four to five days. Piling-Dehydration The salted "umbrellas" are piled to a height of 60-70 cm on a slightly sloping draining board or a tabletop covered with a vinyl sheet. Salt (3-10% of the weight of the jellyfish) is sprinkled on the surface of individual jellyfish during the piling process. Excess water is allowed to drain from the piles, which may last for four to six days. The bottom piles of "umbrellas" must be transferred to the top to facilitate proper drainage of water and to prevent water clogging at the bottom of the pile. The finished product will have around 60-65% moisture. Packaging and Storage The finished product is graded based on diameter, packed in double-vinyl sheets and put into wooden crates, then stored at 2-5oC. Storage of the product above 20oC leads to softening, while storage at below 0oC can result to loss in texture. Alum when used in excessive amounts can lead to the development of a commercially unacceptable white color during extended storage. Allowance for weight loss (due to moisture loss) during storage must be made before packaging. 13.4.2 Grading of Jellyfish The commercial grading of jellyfish is based on the diameter of the discs. Jellyfish with a diameter of 33 cm and above are classified as Grade I, 25-33 cm as Grade II, 17-25 cm as Grade III, and others as off-grade or small pieces. The quality of the finished product also depends on the number of times alum is added 179 Minor Aquatic Products (twice or thrice), color, origin, etc. Processed jellyfish from China are packed in wooden containers (cases or casks) lined with polyethylene bags each weighing 20-50 kg net. Jellyfish in India intended for export are classified as Grade A (around 45 cm diameter), Grade B (30 cm), Grade C (below 20 cm), and off grade. The products are packed in vinyl or high -density polythene lined wooden boxes of 50- kg net capacity. Weight allowance of 5-10 kg is added to the products to compensate for weight loss during transportation, thereby ensuring a minimum net weight of 50 kg at the destination. Jellyfish are sold retail in dried or soaked form. Table 16 shows the proximate composition of fresh and processed jellyfish. Table 16. Composition of Fresh and Processed Jelly Fish Jellyfish Sample Composition (%) Moisture Protein Salt Alum Ash Fresh 96-97 1-1.5 2-2.5 - 2-3.0 Processed 65-75 4-6 16-24 0.7-3.0 17-25 adapted from Subasinghe (1992b) 13.4.3 Use of Jellyfish Jellyfish is an important article in the conventional Southeast Asian or Chinese diet. There are two main types of jellyfish in the market, the "white" type, which is widely distributed in the region, and the "red" type, which is quite rare and of higher commercial value. Processed jellyfish is soaked in water to soften it, cut into strips and scalded. The final product will have a crunchy and elastic texture when prepared in this manner. The strip curls are usually marinated in a seasoned mixture made of sesame oil, soy sauce, vinegar and sugar. In some Japanese cuisine, marinated jellyfish is a significant component in serving grated vegetables such as cabbage, radish, and cucumber or with items such as sea urchin or herring roe. Jellyfish is usually sliced into flower-like or leaf-like shapes in some Chinese preparations. 180 Minor Aquatic Products 13.5 Fish Protein Concentrate Fish protein concentrate (FPC) is defined as a powdered form of fish suitable for human consumption, wherein the protein is more concentrated than in the raw material (Windsor and Barlow, 1981). Raw Material The raw material is fresh fish of all kinds or sizes. Unutilized or underutilized species of fish can well be used for FPC preparation. The raw material must be handled and stored according to the standards used for fresh fish for ordinary consumption. 13.5.1 Types of FPC The Food and Agriculture Organization (FAO) of thee United Nations classifies FPC into three types. λ Type A. A completely odorless and tasteless powder with a total fat content of 0.75%. This type is usually prepared from white fish, which are very low in fat content and is extracted by solvent for several times. The high cost of solvents, such as ethyl and isopropyl alcohol, make the manufacture of this type not economical. λ Type B. A powder with no specific limits with regard to odor and flavor, but with a definite fishy flavor (Fig. 35). In the manufacture of this type, almost any process which produces a stable protein concentrate can be considered and solvent extraction is not necessary. Type B FPC has 70-75% protein, 10% moisture and a maximum of 10% fat. The proximate composition of Type B FPC prepared from local species of fish using different solvents for extraction is shown in Table 17. λ Type C. Ordinary fish meal produced under satisfactorily hygienic conditions. 13.5.2 Methods of FPC Preparation The preparation of Type A and Type B FPC can be classified into three main categories: λ Chemical. Solvents such as ethanol and isopropanol are used. Sodium citrate and sodium chloride (table salt) solutions can be used as well. The choice of extractant is dependent on cost and availability. 181 Minor Aquatic Products λ Enzymatic. This process makes use of proteolytic enzymes, such as bromelin, papain and other bacterial and fungal proteases, in digesting fish protein. The finished product has better functional properties (in terms of solubility, emulsifying property, water holding capacity and others) than the FPC produced using chemical and physical methods. However, the dried product is hygroscopic in nature and will need suitable protection to prevent reabsorption of moisture on storage. λ Physical. This method involves physical processes such as pressing to separate the water and oil from whole fish. 13.5.3 Processing Steps Raw Material The cost of fish is the main consideration in the cost of the finished FPC. Inexpensive fish, which are not in demand for direct use as food, are suitable for the manufacture of Type B FPC. The ideal species of fish for processing are lean fish (Espejo-Hermes, 1985). Cleaning Whole fish is washed thoroughly in running water. Steaming Steaming is done for 15-30 minutes depending on the size of the raw material. Fig. 35. Fish Protein Concentrate (Type B) (Source: Espejo-Hermes, 1985) 182 Minor Aquatic Products Table 17. Proximate Composition of FPC from Various Species of Fish extracted with a) 0.1M citrate buffer b) salt solution and c) water Fish Common Name/Scientific Name Composition Protein Moisture Ash Fat Flesh only a) Shortfin/round scad (Decapterus macrosoma) 81.50 8.00 6.30 4.20 Milkfish (Chanos chanos) 76.02 4.83 3.27 15.84 Mudfish (Ophicephalus striatus) 80.21 8.75 4.40 7.60 Catfish (Clarias batrachus) 75.14 8.01 2.92 14.10 Tilapia (Oreochromis mossambica) 89.14 5.69 5.29 1.49 b) Shortfin/round scad (Decapterus macrosoma) 77.30 8.10 6.51 8.09 Frigate tuna (Auxis thazard) 76.96 7.64 3.40 12.00 Whole fish a) Hairtail (Trichiurus haumela) 67.09 9.79 16.68 5.55 Threadfin bream (Nemipterus ovenii) 67.78 6.04 22.09 9.20 Whiting (Sillago sihama) 61.44 6.46 21.31 10.83 Indian oil sardine (Sardinella longiceps) 61.61 10.50 15.13 7.83 b) Ponyfish/slipmouth (Leiognathus spp.) 69.72 6.66 18.18 5.44 Anchovy (Stolephorus spp.) 74.71 5.43 11.30 8.56 c) Lizardfish (Saurida tumbil) 73.52 4.99 8.56 2.93 Ponyfish/slipmouth (Leiognathus spp.) 68.19 7.99 16.60 7.30 Adapted from: Espejo-Hermes et al., 1981 183 Minor Aquatic Products Deboning The flesh is separated from the bones and visceral organs. If the fish are small, this step can be omitted. However, deboning is considered necessary in order to reduce the bone content of the finished product, hence lowering the fluoride level. Mincing The flesh or the whole fish is minced manually or by mechanical means. Mincing can be done with deboning if a meat-bone separator is used. Extraction One of the following solvents may be employed for extraction: water/ aqueous extraction (for every cup of minced flesh, add 2 cups water) or salt extraction (5% brine solution) using 1½ cups water per cup of minced flesh. Extraction is done by boiling the fish: solvent mixture. The extraction process removes lipids and water which otherwise would shorten the keeping quality of the processed FPC if present in high quantity. Pressing The boiled mixture is pressed manually using cheese or muslin cloth. A mechanical press may also be used. Pressing the mixture while still hot will efficiently remove the lipid and water content in the pressed cake. Drying The pressed cake is dried under the sun or in a solar drier. Grinding The dried cake is ground using a corn grinder, pulverizer, or mortar and pestle. Packaging The powdered FPC can be packed in polyethylene bags, bottles, etc. Storage The FPC is stored in a cool, dry place. Properly prepared FPC can keep up to a year or more. 184 Minor Aquatic Products 13.5.4 Manufactured Products FPC is not eaten per se. The product is added to food products, which are low in protein. Local recipes like guisado, okoy, palabok sauce and others can be fortified with FPC. It can also be added to snack food items such as kroepeck, polvoron, and crackers. Sometimes, FPC becomes unpalatable when added to soups due to its grainy or sandy texture. FPC is particularly beneficial in enhancing the diet of growing children and pregnant or nursing mothers. 13.5.4.1 FPC Kroepeck Kroepeck is a dried product traditionally made from ground rice with shrimp or fish added to it (Orejana et al., 1976). The addition of FPC to kroepeck increases the protein content of the product relative to its high carbohydrate content. The procedure presented below makes use of flour and cornstarch instead of rice due to wide variability in the type of rice which can affect the quality of the finished product (Espejo-Hermes,1985). Materials and Equipment flour, 2 c baking pan cornstarch, 2 c steamer salt, 2 tbsp measuring spoons FPC, 4 tbsp measuring cups pepper, 1½ tsp (ground) drying trays water, 4 c knife Procedure 1. Combine all dry ingredients. Add water and blend well. 2. Place 3 tablespoons of the mixture on a greased pan. 3. Steam for 2 minutes or until it becomes translucent. 4. Cut into strips and carefully remove from the pan. 5. Arrange the slices on drying trays. 6. Dry under the sun or in a solar dryer. 7. Deep fat fry. 185 Minor Aquatic Products 13.5.4.2 Okoy (Sprouted Mung Beans with FPC) Materials and Equipment sprouted mung beans (toge), ½ kg measuring spoons flour, 1 c measuring cups pepper, 1½ tsp (ground) frying pan salt, 1½ tbsp mixing bowl water, ½ c cooking oil FPC, ¼ c Procedure 1. Clean the sprouted beans well. 2. Mix sprouted beans with FPC, pepper, salt and flour. 3. Add water into the mixture. Blend well. 4. Mold into desired size and shape. 5. Deep fat fry. 13.5.4.3 Molido (Candied Camote with FPC) Materials and Equipment sweet potato (cooked minced camote), 1½ c sugar, 1 c FPC, 2 tbsp measuring cups vanilla, 1 tsp pan evaporated milk, ¼ c cooking pan measuring spoons drying tray Procedure 1. Gently heat milk and dissolve sugar in it. 2. Add vanilla, FPC and camote. Mix well. 3. Continue stirring until mixture thickens. 4. Place in a greased pan (fill pan up to 1 cm thick). 5. Cut into small rectangular pieces (3 x 1 cm). 6. Dry under the sun until hard. 186 Minor Aquatic Products 13.5.4.4 FPC Noodles Materials and Equipment flour, 1½ c mixing bowl salt, 1½ tsp measuring spoons FPC, 1 tbsp measuring cups water, 1/3 c noodle maker Procedure 1. Mix flour, salt and FPC. 2. Add water, stir until thoroughly blended. 3. Knead. 4. Flatten with a rolling pin, then pass through a noodle maker. 13.5.4.5 Palabok Sauce Materials and Equipment garlic, 1 head (minced) salt, 1 tsp shrimp, ½ c (shelled) atsuete, 1 tbsp kinchay, ½ c flour, 4 tbsp pepper, 1/8 tsp (ground) oil, 1 tbsp water, ¾ c measuring spoons FPC, 1 tbsp + 1 tsp measuring cup bean curd (tokwa), ½ c (cubed) cooking pot shrimp juice, ½ c mixing bowl rice noodle (bijon), ¼ kg Procedure 1. Heat oil. Sauté garlic until brown. 2. Add tokwa and shrimps. 3. Add some shrimp juice, cover and boil. 4. Add kinchay, garlic, salt and pepper. 5. Set the shrimp mixture aside. 6. Soak atsuete in ¼ cup water. Squeeze out the color. 7. Add the color to remaining shrimp juice and transfer mixture to a pan. 8. Add FPC to the mixture. 187 Minor Aquatic Products 9. Dissolve flour in ½ cup water. Add to the mixture. 10. Bring to a boil, stirring constantly. 11. Season with salt and pepper. 12. Use as topping for cooked bijon. 13.5.4.6 FPC Sauce Materials and Equipment FPC, 2 tsp garlic, 2 tsp (minced) cooking oil, 1 tbsp pepper, 1/8 tsp onion, 1 tbsp. (chopped) water, 1 c salt, 1 tsp measuring spoons flour, 2 tsp measuring cups cooking pan Procedure 1. Heat oil. Sauté garlic and onion. 2. Add FPC, then the water. Let boil. 3. Dissolve flour in a little amount of water and add to the boiling FPC broth. Season. 4. Allow to boil for about 5 more minutes or until sauce thickens slowly. 5. Use as sauce for noodles, boiled vegetables or rice. 13.5.4.7 Fish Crackers Materials and Equipment flour, 1 c measuring spoons salt, 1 tsp measuring cups pepper, ½ tsp rolling pin FPC, 1 ½ tbsp knife paprika powder, ½ tsp mixing bowl water, 1/3 c 188 Minor Aquatic Products Procedure 1. Mix all dry ingredients. 2. Add water. Stir and knead until dough is thoroughly blended. 3. Roll with a rolling pin until dough is very thin (about 1/5 cm). 4. Cut into rectangular pieces (1½ x 5 cm). 5. Deep fat fry until golden brown. 13.5.4.8 FPC Polvoron Materials and Equipment flour, 2 c measuring spoons sugar, 1 c measuring cups shortening, ¼ c molders vanilla, 1 tsp Japanese paper FPC, 1-2 tbsp cooking pan Procedure 1. Sift flour and sugar. 2. Toast the flour until golden brown. 3. Sift again to remove the lumps, then set aside. 4. Melt shortening, then add the vanilla extract. 5. Mix well the toasted flour, FPC, sugar and shortening. 6. Mold with the use of polvoron molders. 7. Wrap each mold in Japanese paper. 13.5.5 Quality Problem Rancidity FPC with high fat content is susceptible to rancidity. The oxidized fat imparts unacceptable flavor, and hence the product becomes undesirable. 13.6 Sea Cucumber Sea cucumber is very popular in China and among the Chinese communities in many Southeast Asian countries. The sea cucumber fishery used to 189 Minor Aquatic Products be an important source of income for many fishers in some Indo-Pacific countries such as the Philippines, Indonesia, Fiji, Papua New Guinea, Tonga, Maldives and others. Resources have been heavily depleted due to overfishing. Sea cucumbers (sea slugs or trepang) or bêche-de-mer (French) have a cylindrical, elongated body and come in different colors, from pitch black to light yellow or white or with a blend of colors (Fig. 36). Locally, sea cucumbers are known as "balatan" in Tagalog or "balat" in Visayan. All these terms mean sea cucumber but commonly refer to the dried form of the holothurian (Darvin and Landez, 1992). Sea cucumbers range from 20-70 cm in length when fully grown and their weight may range from 2-5 kg. The thick body wall, with a moisture content of about 80%, accounts for nearly 50% of the weight of the animal. There are around 500 species of sea cucumber but only a few (around 10-17) are valuable commercially. The common species are teat fish (Holuthuria nobilis), sandfish (Holothuria scabra), black fish (Actinopyga miliaris), lolly fish (Holothuria atra), deep-water red fish (Actinopyga echinites), and prickly red fish (Thelenota ananas). Sandfish and teatfish are the most valuable species due to their thick body walls (Subasinghe, 1992b). Fig. 36. Sea Cucumbers 190 Minor Aquatic Products 13.6.1 Harvesting/Post-Harvesting Sea cucumbers are collected by hand from shallow waters. In deeper waters, they are gathered by skin divers operating from boats. Fork-ended rods are often used to pick the animals. Skiff trawls can be used in areas where high concentrations of bêche-de-mer are found. Fishing with a barbed weighted spear attached to a string is being discouraged because the spear can damage the body wall causing it to break during processing. Efficient handling practices are required to reduce losses during processing and improve the market value of sea cucumber. Bêche-de-mer must be kept alive in seawater until processing. When handled carelessly, sea cucumbers tend to eviscerate. The body of the animals may be deformed or "melted", and tends to stick together when exposed to the sun. Collection of sea cucumber must be regulated to avoid over-exploitation of immature animals. Sedentary animals must be allowed to grow to reach a size where they can reproduce before capture. Under-sized raw material often results to a finished product which does not meet the size requirement and hence cannot be marketed. Some countries, particularly those in the South Pacific Region, impose regulations regarding the minimum size for collection (Table 18). In Papua New Guinea (PNG), the Coastal Fisheries Development Project through the Extension Section of the Division of Fisheries and Marine Resources in Morobe Province Table 18. Minimum Size of Sea Cucumber for Collection Species Common and Scientific Names Minimum Length (cm) PNG\* Tonga Sandfish (Holothuria scabra) 22 16 Black fish (Actinopyga miliaris.) 22 - Black teat fish (Holothuria nobilis) 15 26 Deep water red fish (Actinopyga echinites) 15 12 Elephant trunkfish (Holothuria fuscopunctata) 32 35 Prickly red fish (Thelenota ananas) 32 30 Lollyfish (Holothuria atra) - 16.5 White teat fish (Holothuria fuscogilva) 35 32 \*computation based on the projected shrinkage after processing 191 Minor Aquatic Products recommends the minimum sizes for collection (Espejo-Hermes, 1996). In the Kingdom of Tonga, the minimum size for collection is strictly regulated (Fisheries Act, 1989). 13.6.2 Processing The processing of sea cucumber consists basically of two steps: cooking and drying. The methods in the processing of sea cucumbers in the Pacific Islands were introduced by Chinese people and have not changed much over the years. The processing steps described are applicable to all species except sandfish (SPC, 1993; Subasinghe, 1992; Conand, 1990; Van Eys and Philipson, 1989). Sandfish are gutted before cooking, while teatfish and several other species are cooked whole (Figs. 37 and 38). Cleaning Prior to cooking, freshly eviscerated sea cucumbers are cleaned by lightly brushing the surface with coconut husk or any other suitable material to remove sand and other material adhering to the surface. The animals are washed in clean seawater and any water remaining in the belly cavity is gently squeezed out. Gutting Depending on the method employed, the sea cucumbers can be gutted before or after the first boiling. The internal organs must be cut and removed making sure that no stubs are left at the ends. The tissue lining the inner walls of the body cavity must not be removed. First Boiling The cleaned sea cucumbers are sorted by species and by size, then immersed in boiling water. It is important that the water is brought to the boil before the animals are put into the boiler. The sea cucumbers must be completely submerged in the boiling water. A wire-mesh basket could be used to take out the sea cucumber for inspection, which is done frequently during boiling and for easier removal of the sea cucumber after boiling. The animals must be stirred continuously; a wooden spatula or paddle is suitable for stirring. The cooking time depends upon the size of the animals. Sea cucumbers, such as sandfish and other species with similar texture, are ready for the next stage of processing when the cooked material bounces like a rubber ball when dropped on to a hard surface. 192 Minor Aquatic Products Fig. 37. Sandfish Processing (Source: Subasinghe, 1992b) 193 Minor Aquatic Products Fig. 38. Teatfish Processing (Source: Subasinghe, 1992b) 194 Minor Aquatic Products In general, the sea cucumbers are ready when they have started to swell up. The animals are then taken out of the boiling water and put into cold seawater to cool. They will burst if left boiling for too long. Descumming (Sandfish) The removal of calcareous (lime) covering or the chalk-like material in the outer skin of sandfish is necessary to get an acceptable finished product. Descumming of sandfish is carried out after the first boiling by burying them in a shallow, flat- bottomed pit (20-30 cm deep) at an appropriate spot in a clean, sandy beach. The pit, usually measuring 100 x 75 cm, is excavated in areas far from tidal water inflow. The sea cucumbers are packed densely at the bottom of the pit and covered with moist or damp material (e.g., jute sack or cloth). This will facilitate bacterial decomposition of the product. The pit is then covered with sand. The animals are removed from the pit after 15-18 hours and washed in clean seawater, scrubbing away the outer tegument and ventral milky white pigmented layers. Slitting After the sea cucumbers have been taken out and cooled off in seawater, the animals are placed on a flat board with the belly side down. A neat cut along the back is made using a sharp knife. The cut must be clean; around 2-3 cm of the mouth and anus must be left intact to properly close the animals. This will prevent the body from opening up completely. Second Boiling After gutting or descumming, the sea cucumbers are again boiled with continuous stirring for 15-30 minutes or depending on the size of the animals. During the second boiling, the sea cucumbers will shrink slightly and gradually become hard and rubbery. The hardness of the animal will be the measure of the correct cooking time. After cooking, the animals are removed and put into seawater to cool. Smoke Drying Smoke drying of the sea cucumbers can be carried out using a copra dryer. Good drying materials for the fire are coconut husks or mangrove wood. If wood is used, branches with leaves must be thrown over the fire to prevent the fire from getting too hot; this will create the necessary smoke. The animals are opened up and short sticks (not more than 2.5 cm. long) are inserted across the cut to keep the sides apart. The animals are then placed on 195 Minor Aquatic Products the trays with their split sides down so the inner part of the body is exposed to the heat source. The trays must be moved regularly every few hours to result in uniform drying. Halfway through the drying process, the sticks are removed and the animals are tied with string or vines to restore their uniform cylindrical shape. Drying of the sea cucumbers can be completed after 24-48 hours. The dryness of the product can be judged by placing a finger inside the product. It should be completely dry to the touch. Sun drying The sea cucumbers are brushed to remove soot, ash or dirt that have accumulated during the smoking. The animals are then put out in the sun and wind for a few days to dry out completely. Sun drying must be carried out on raised platforms or racks to avoid contamination with sand which can reduce the quality and marketability of the product. The final product must be hard as wood with a moisture content of 15- 20%. In general, the finished product weight is around 4-10% of the original weight. Dried sea cucumber can shrink up to 35-50% of the original length. The dried product must be inspected thoroughly and, if found to be somewhat soft and damp, must be further smoked or dried. Packaging and Storage The finished product can be packed in clean, dry copra sacks or in carton boxes lined with polythene. The packed product must be stored in a cool, dry place. Dried sea cucumbers are hygroscopic; they tend to absorb moisture from the atmosphere. If the product is to be kept for a long time in humid conditions, re-drying is required to prevent moisture build-up and eventual decomposition. Exposure of the packed product to direct sunlight or heat must be avoided to prevent moisture loss. Grading Sea cucumbers are graded according to species, size and quality. The grades according to species are: high value, medium value and low value species; according to size, they are categorized as: extra large (XL), large (L), medium (M), small (S) and extra small (XS). Each grade corresponds to a range of length or weight. 196 Minor Aquatic Products In the South Pacific region, sea cucumbers are graded according to length. Minimum size limits for exported species are well established in some South Pacific countries. The minimum legal dried length for some species of sea cucumbers in Papua New Guinea and the Kingdom of Tonga are given in Table 19. The current size limit for all species intended for export is 7.6 cm in Fiji and 15 cm in Queensland, Australia. Table 19. Size Limit of Dried Sea Cucumber Species Common and Scientific Names Minimum Length (cm) Papua New Guinea Tonga Sandfish (Holothuria scabra) 8 7 Black fish (Actinopyga miliaris.) 11 - Black teat fish (Holothuria nobilis) 7 13 Deep water red fish (Actinopyga echinites) 5 6 Elephant trunkfish (Holothuria fuscopunctata) 12 15 Prickly red fish (Thelenota ananas) 11 12 Lollyfish (Holothuria atra) - 8 White teat fish (Holothuria fuscogilva) 17 16 Quality grading of dried sea cucumber is based on appearance, odor, color and moisture content. The product's general appearance affects the grade and depends on the care that was taken in the various stages of processing. Sea cucumbers which have been improperly gutted, still contain sand, or are overcooked, not properly cut or not smoked and dried long enough, or that have been stored in a damp place are down-graded. A uniform shape is preferred to a shrunken, uneven appearance. The customers prefer a cylindrical-shaped sea cucumber with pleasant smell. 197 Minor Aquatic Products 13.7 Fish Meal Fish meal is a dried fishery product from excess catch, waste materials from fish processing plants, rejects and market surpluses. Fish meal contains high amounts of easily digestible proteins, minerals, vitamins and almost all the necessary trace elements and essential amino acids. It is an essential ingredient in ready-mixed poultry and hog feeds. Raw Material Almost all species of fish can be used in the preparation of fish meal. Other raw materials which can be utilized in fish meal production include: fish waste (consisting of the head, tail, fins and viscera), scrap fish that do not command a good price in the market, and dried fish which are un-marketable due to poor quality. 13.7.1 Methods of Processing 13.7.1.1 Wet Reduction Process This process is generally applied to fatty fish and combines meal manufacture and oil production. The basic steps involved are: steaming or cooking, drying and grinding. The wet reduction process differs from dry reduction because in the former, cooking or steaming is followed by pressing (these steps are omitted in the dry reduction process) to leach out the liquid from the cooked materials. A semi-dry solid known as the press cake is obtained, then subsequently dried and ground. The pressed liquid contains much of the oil and water-soluble components (Brody, 1965; Windsor and Barlow, 1981). Oil and protein can be recovered from the liquor/liquid waste. 13.7.1.2 Dry Reduction Process The species of fish usually processed in this manner are those with low fat content. Fish meal manufactured by this method contains all the water-soluble compounds, and a large percent of oil which lowers the quality of the meal. This process involves drying, grinding and packaging. The percentage yield and composition of fish meal produced by the dry reduction and the wet reduction process are shown in Table 20. 198 Minor Aquatic Products Table 20. Percentage Yield and Proximate Composition of Meal Prepared from Milkfish Offal by Wet and Dry Reduction Percentage (%) Reduction Methods Wet Dry Yield 24.2 31.0 Moisture 8.8 6.2 Protein 42.4 48.9 Fat 25.0 30.1 Ash 19.0 16.6 Adapted from Santos et al., 1978 13.7.2 Composition of Fish Meal The chemical composition of fish meal varies with the species as well as the actual raw material used, e.g., waste, scrap fish, and rejects, and the method employed for preparation (Table 21). λ Protein. Protein content usually ranges from 55-70% by weight. Most meals contain between 60-65% protein. Local meal must contain at least 45% protein (Bureau of Animal Industry Administrative Order No. 40). λ Fat. Fat content may vary from 5-10%, but preferably should not be more than 8%. Fish meals with high fat content are more susceptible to rancidity. λ Ash. Fish meal with about 18% ash is considered satisfactory. λ Moisture. An average of 8% is preferred with an allowable range of 6-10%. Fish meal with 12% moisture will be susceptible to mold growth. Heating will occur if the moisture content is less than 6%. λ Crude Fiber. The crude fiber content is less than 1%. Fish meal is regarded as a low fiber food. Table 21. Composition of Fish Meal from Varying Raw Materials Using Wet Reduction Process Raw Material Percentage (%) Protein Moisture Fat Ash Lizardfish offal 53.5 6.6 5.4 30.5 Milkfish offal 45.1 10.5 15.2 11.8 By-catch fish 54.5 10.4 6.4 26.6 Source: Espejo-Hermes (1985) 199 Minor Aquatic Products 13.7.3 Nutritional Value λ Protein. Fish meal contains high-quality protein. The protein content of fish meal consists of 10 essential amino acids and 11 disposable amino acids in sufficient amounts. Fish meal protein is nutritionally valuable because of its high lysine content. λ Vitamins. Fish meal is a good source of vitamins which are important in animal nutrition. The B-vitamins in fish meal include the following (Windsor and Barlow, 1981): Vitamins Parts per million Riboflavin 4.8-7.3 Folic acid NA-0.5 Niacin 50-126 Pantothenic acid 8.8-30.6 Choline 4,400 B12 0.06-0.25 Biotin 0.08-0.42 Fish meal, however, cannot be considered a reliable source of vitamins A and D because it is affected by the high temperature used in processing (particularly in the wet reduction process) and also due to the onset of lipid oxidation in the manufactured meal. λ Fats. The presence of high amounts of fat in fish meal in general lowers the nutritional value of the meal to be used for feeding purposes. λ Minerals. The main minerals found in fish meal are calcium and phosphorous as well as other minerals such as iron, magnesium, potassium, sodium and iodine. 13.7.4 Fish Meal in Animal Nutrition Poultry, Hog and Cattle Protein and calcium phosphate in fish meal are suitable for brood or adult chickens. The recommended levels of meal should not be more than 10% of total ration for hens and not more than 5% of total ration for chickens. Fish meal as a stock feed supplement must be used at relatively low levels so that no objectionable fish odors and flavors are imparted to the animal tissues. High levels usually affect the taste of products such as eggs, meat or milk. 200 Minor Aquatic Products Fish meal has similar nutritional effects in both pigs and poultry. It is effective in preventing osteomalacia (softening of the bones). The optimum amount of fish meal to be fed to pigs is between 10-15% of the total amount of feed. The effect of fish meal in cattle is similar to that for pigs. The ideal amount is considered to be between 5-10% of the total amount of feed. The approximate amount of fish meal supplement is 1 kg per day for every 500 kg live weight. Fish Cultured species of fish have an essential requirement for fish protein in the diet in order to maintain adequate health and growth. The amount of fish meal used varies between 10% and 70%, depending upon the type of diet required and cost of feeds. Fish meal with low fat is preferred for fish feeding. 13.7.5 Preparation of Fish Meal Materials and Equipment fish of any species boiler or steamer drying trays mechanical press Procedure Ideally, fresh raw materials should be used in the production of high quality fish meal. Other raw materials which can be used include offal from fish processing operations, damaged fish, as well as fish with very low market value, such as very small tilapia. Boiling/Steaming Depending on the species and size, the fish are boiled or steamed until cooked. Pressing The cooked fish are drained first before pressing. Much of the liquid from the cooked fish can be separated simply by draining and this is normally achieved by transferring the cooked mass on a strainer. Draining will remove the liquid mixture of oil and water containing dissolved and suspended solids before pressing. A good pressing procedure using a mechanical press will efficiently reduce the moisture and oil content, which will result to a shorter drying period, good quality meal and 201 Minor Aquatic Products longer shelf life. Pressing is found to be difficult when poor quality (spoiled) raw material is used. Drying The pressed cake together with the concentrated stickwater is dried under the sun or in a mechanical dryer. The cake is usually dried from about 50% moisture content to about 10%. The low moisture content makes the meal more stable against bacterial or enzymatic attacks. Also, drying reduces the bulk of the product thereby making handling, storage and transport easier. Grinding The dried meal is ground to a homogenous product with improved appearance, which can be easily weighed, packaged, transported and readily mixed in feeds. Various types of mills, such as a hammer mill, are available and are suitable for grinding fish meal. Packaging The ground meal is packed in plastic film bags or sacks (Fig. 39). The most suitable bags depend on the material, the mode, condition and distance of transport and the preferences of the users. Sacks are the most commonly used bulk containers for fish meal. Fig. 39. Fish Meal (Source: Espejo-Hermes, 1985) 202 Minor Aquatic Products 13.7.6 Problems in Fish Meal Manufacture Reducing Odor During Processing Unpleasant odors are produced during fish meal manufacture. One of the major causes of these odors is the inclusion of spoiled raw materials. Reduction of odors can be achieved by using only fresh raw materials, maintaining cleanliness of the processing machinery and factory, and installation of suitable filters and treatment of effluent air. Risk of Salmonella Contamination Fish meal is susceptible to the growth of Salmonella which is very harmful to man. The main source of these bacteria is contamination due to poor sanitation in the plant. Possible carriers of Salmonella are birds and rodents, which might have access to the raw material or meal. Strict observance of proper hygiene in the plant is therefore recommended in order to minimize the risk of contamination (Windsor and Barlow, 1981). Quality It is impossible to produce high quality fish meal from low grade (spoiled) fish. Hence, the use of only fresh materials is of primary importance in fish meal manufacture to ensure high quality and nutritional feeds. 13.8 Fish Silage Fish silage is the liquid product made from minced fish or fish offal, usually prepared through the addition of acid or fermentable sugars, which favors growth of lactic acid bacteria to prevent bacterial spoilage. It is normally used as a component of animal feed. Raw Material Almost any species of fish can be used to make fish silage, though cartilaginous species such as sharks and rays tend to liquefy slowly and are best mixed with other species. 203 Minor Aquatic Products 13.8.1 Types of Silage 13.8.1.1 Acid Preserved Silage Adding acid, either inorganic (sulfuric, phosphoric, hydrochloric acid) or organic (formic acid, propionic acid), initiates the process, in order to lower the pH sufficiently to prevent microbial spoilage. The silage liquefies due to degradation of tissue structures by enzymes naturally present in the fish. If inorganic acids are used, the pH of the silage must be stabilized at pH 3.5 - 4.0 with formic acid and pH 4.5 with propionic acid. Such moderately acid silage can be added in animal rations and feed without neutralization with calcium hydroxide. Occasionally, acid mixtures are used for fish silage production (Disney et al., 1978; Raa and Gildberg, 1982). 13.8.1.2 Microbial Silage (Fermented Silage) Fermentation is initiated by mixing minced or chopped fish with a fermentable sugar, which favors growth of lactic acid bacteria. These bacteria may be naturally present in the fish and ferment the available sugars to organic acids, thereby lowering the growth of spoilage and pathogenic organisms (Windsor and Barlow, 1981). Microbial ensilage of herring using a starter culture of Lactobacillus plantarum with 15% molasses showed an increase in crude protein higher than the uninoculated sample after 21 days of fermentation (Lopez, 1990). 13.8.2 Composition of Fish Silage Fish silage has the same composition as that of the raw material from which it is made, except for the slight dilution effected through the addition of an acid or carbohydrate source. Table 22 shows the proximate composition of locally produced silages. The composition of de-oiled silages and white fish offal silage usually ranges from 14.5%-17% protein and 0.5%-2.0% oil. 204 Minor Aquatic Products Table 22. Proximate Composition of Silages Made from Varying Raw Materials Raw Material Composition (%) Protein Fat Moisture Ash Sardine/herring Offal 13.5 8.7 75.4 2.6 Lizard Fish Offal 15.1 3.5 72.7 5.4 Anchovy 11.8 1.4 81.2 3.0 Slipmouth 16.7 1.6 78.0 4.0 Mackerel 16.9 12.0 70.2 2.1 Roundscad 17.3 2.6 73.8 3.6 Source: Espejo-Hermes (1985) 13.8.3 Uses of Silage Pig Nutrition Fish silage-fed pigs have shown better growth efficiencies than control animals. Poor meat (in terms of odor and palatability) may result when oily fish such as sardine/herring is used as the silage raw material, but not when fish offal from lean fish is used. Good feed conversion ratios using 20% and 30% fish silage in the diets of pigs have been reported. Poultry Nutrition Inclusion level of neutralized silage (acid silage) corresponding to 30% of the total protein in the diet for chicken, and 12 to 23% for broilers have been shown to result in similar growth rates and overall performances as in diets composed of other protein sources. Fish Nutrition Silage-based moist pellets have been found to be an excellent diet for salmonid fish in Norwegian fish farms. In diets of carps, silage has been shown to be a good source of protein if the raw material was boiled prior to ensilage. 205 Minor Aquatic Products 13.8.4 Fish Silage Production and Storage Mincing The raw material is minced by using a grinder to produce particles not greater than 10-mm diameter. The type of grinder will depend upon the type of raw material. Mixing with Acid/Carbohydrate Source The minced mass is mixed with an acid (for acid ensilaging) or carbohydrate source (for microbial ensilaging). If formic acid is used, the suitable level of addition is between 2.5% and 3.5% by weight. In general, however, the greater the bone contents of the raw material, the higher the level of acid required. It is very important that the acid and fish are mixed well because untreated material will spoil. The acidity of the mixture must be below pH 4 to prevent bacterial spoilage. For small-scale manufacture of fish silage, oil drums can be used and hand stirring will be adequate; for large-scale production, a heavy-duty mechanical mixer is required. Mixtures of inorganic acids (sulfuric, phosphoric and hydrochloric) and organic acids (formic and propionic acid) can well be used (Raa and Gildberg, 1982). Approximately 3% of a 3:1 (volume/volume) mixture of sulfuric and formic acid has been shown to preserve fish offal equally well as 4% (volume/weight) of pure sulfuric acid. For bacterial silages, addition of at least 10% molasses is required to produce stable silage. Good silage can also be produced by using 20% dry mixture of malt meal and oatmeal. Ragi, a fermented rice, can readily be added to silage. Other carbohydrate sources such as tapioca and cereal meals can be used; similarly, starter cultures of lactic acid bacteria produced commercially can be employed. Liquefaction The mixture is placed in an oil drum and agitated periodically to hasten the liquefaction process (Fig. 40). The mince tends to "stiffen" slightly on addition of the acid, but autolysis proceeds, the rate being dependent on the nature of the raw material, type of acid or carbohydrate source used, pH and temperature of the mixture. Fatty fish tend to liquefy faster, while fish offal and fresh fish liquefy more rapidly than stale fish. The warmer the mixture, the faster the process. Heating above 40oC should be avoided in order not to inactivate the enzymes present. About 80% of the protein in the silage usually solubilizes after one week of storage at 23 to 30oC. 206 Minor Aquatic Products Storage Fish silage is stable for years if the correct pH is maintained. However, during storage, changes in proteins and fatty acids occur. The proteins become more soluble and there is an increase in the amount of free fatty acids in any fish oil present, but feeding trials have not shown any detrimental effect nutritionally. 13.8.5 Problems in Fish Silage Production Storage Fish silage preparation normally takes one to five days and storage tanks are needed. Transport Fish silage is bulky and therefore costly to transport. The cost of transport of raw material to the plant can be eliminated or greatly reduced by making silage close to the fish landings or to the end user's place (Windsor and Barlow, 1981). Marketing The product is not well known by nutritionists and farmers. Hence, some marketing effort is necessary to promote silage. Fig. 40. Fish Silage (Source: Espejo-Hermes, 1985) 207 Minor Aquatic Products 13.8.6 Fish Silage versus Fish Meal There are some advantages of fish silage over fish meal. Technology-wise, fish silage production is simple and requires little capital to operate. Its production is also more environment-friendly due to less pollution generated and less energy used. Nutritionally, fish meal has higher protein content and higher content of specific amino acids per given weight (except for glycine) than silage (Table 23). This could be due to the effect of the acids used, which destroy certain amino acids (Santos et al., 1978). However, in terms of net protein utilization (NPU), Flores (1973) found that it is higher in fish silage than in fish meal (Table 24). Table 23. Amino Acid Composition of Fish Silage and Fish Meal Prepared from Milkfish Offal Amino Acid Amino Acid Content (mg/g Protein) Silage Fish Meal Dry Reduction Wet Reduction Lysine\* 43.9 67.2 55.8 Histidine 21.8 27.8 19.6 Arginine 44.2 59.0 46.0 Aspartic Acid 60.0 91.1 74.7 Threonine\* 26.5 41.6 35.5 Serine 29.1 45.1 36.9 Glutamic Acid 86.4 126.1 111.5 Proline 53.1 57.1 44.9 Glycine 99.1 95.1 76.1 Alanine 55.8 67.1 57.9 Cystine - - trace Valine\* 29.8 51.8 39.4 Methionine\* 0.9 0.8 10.4 Isoleucine\* 22.2 39.5 34.7 Leucine\* 38.9 69.3 58.4 Tyrosine 8.8 16.4 17.2 Phenylalanine\* 26.3 37.8 32.1 Tryptophan\* - - - \*Essential amino acids (EAA) Source: Santos et al. (1978) 208 Minor Aquatic Products Table 24. Comparison Between the Pepsin Digestibility of Fish Silage and Fish Meal Prepared from Milkfish Offal Samples Pepsin Digestibility % protein Solubility % protein % NPU of Total protein Fish Silage 1.1 18.3 36.9 Fish Meal 1.8 15.8 33.3 Source: Flores (1973) 13.9 Shells and Shellcraft Shells are produced by molluscs as an outer skeleton, largely composed of a limy material, calcium carbonate. Molluscs are soft-bodied invertebrate animals which secrete this shell-building material. There are three major classes of molluscs well-known to many people: the univalves (Gastropoda) which include the snails, conches and periwinkles; the cephalopods (Cephalopoda), the squids, cuttlefish, nautiluses and octopuses; and the bivalves (Bivalvia), the clams, mussels, oysters and scallops. The shells produced by representatives of all three groups are potential raw materials for local trade. Various items such as buttons, necklaces, lampshades, flowers and other ornamental objects are made from the inedible shells (Fig. 41). Shells which are not suitable for ornamental objects due to their poor quality find their way into lime making. Fig. 41. Ornamental Objects from Shells (Source: Espejo-Hermes, 1985) 209 Minor Aquatic Products The Philippines has over 4,000 species of marine shellfish, almost the same number again in forest snails and river univalves. In Luzon, the common species are the marble cone, textile cone, the ricine drupe, the grossularia drupe, the lambis scorpion conch, and many other western Pacific species. In the central Philippines, around Cebu, Leyte, Romblon and Negros, the Pacific species are mingled with many species of a more westerly distribution range. Around the island of Palawan and the Sulu Archipelago, the fauna has much closer affinities with that of the Indonesian islands of Kalimantan, Sulawesi and Mollucas than with that of the northern Philippines. The region of Zamboanga and Cuyo Islands provide the fabulous imperial volute and the scarlet and orange aulica volute. Other shells such as the noble cone are endemic to these waters. Fisheries for cephalopods and culture and/or gathering of other edible molluscs are conducted in many parts of the country. 13.9.1 Methods of Cleaning and Preserving Shells The attractiveness of a shell will depend largely upon how well the molluscs have been cleaned and preserved. There are six easy ways to clean shelled molluscs (Abbott, 1972). 13.9.1.1 Freezing The most commonly adopted method for removing meat from the shells is freezing. The molluscs are placed in plastic bags, sealed or tied shut, then the bags are placed in the lower part of the refrigerator for a couple of hours. After this treatment, the bags are placed in the freezer for two or three days. When thawing the contents, the bag is put back in the lower part of the refrigerator for half a day, then soaked in cold water. The process is done gradually to prevent fine cracks from developing in the enamel of large, glossy shells. When completely thawed usually over a period of 24 hours, most soft tissues of univalves will come out completely by pulling it in an unwinding, corkscrew fashion using a fork or bent safety pin. 13.9.1.2 Boiling Live Shells in Fresh or Salt Water Bivalves are boiled for one or two minutes, univalves for six to 10 minutes depending on their size. The pot is allowed to stand for one hour, or one-third cold water is added to bring the temperature down gradually. 210 Minor Aquatic Products 13.9.1.3 Preserving The best preservative for shells is 70% ethyl alcohol. Isopropyl alcohol can be used in 50% concentration. A 5-6% formalin mixture (one part of 40% formalin with eight parts of water) can be well used if it has been buffered with 2 tablespoons of baking soda per liter formalin. This is done to prevent etching away of the shells as formalin shows acidic reaction. 13.9.1.4 Salting This is employed in an emergency situation. The live univalves may be packed in table salt in cardboard or in wooden boxes. A supersaturated salt solution can also be used as a preliminary bath, after which the molluscs will have to be soaked and cleaned by hand. 13.9.1.5 Rotting Out Fine shells can be buried in soft sand in the shade for rotting. Ants or blowflies can also readily clean out the meat; however, this procedure should be employed some distance from residential places because of odors. 13.9.1.6 Bleaching Live or smelly shells can be dumped or soaked in a 50% solution of chlorine bleach. This will dissolve away the flesh and the outer organic growths. The exteriors of shells can be bleached by giving them an overnight soak in full strength bleach. When the shell is dried, picking at the surface or giving it a sharp, quick rap with an old dentist tool will chip off the white encrustation. Brushing with warm water and detergent will be sufficient in most cases. Baby oil when used sparingly will give some shells a lighter color. 13.9.2 Shellcraft Making 13.9.2.1 Button Making In the manufacture of shell buttons, the following shells are used: gold-lip shell (Pinctada maxima), black-lip pearl oyster (Pinctada margaritifera), species of top shell commonly known as trocas (Trochus maximus, Trochus obeliscus, Trochus noduliferus, Trochus niloticus), and turban shell or green shell (Turbo marmoratus). Most of these shells are found in the Sulu Archipelago, and along the 211 Minor Aquatic Products coasts of Cebu, Bohol, Leyte, Mindoro, Palawan, Pangasinan, Ilocos Sur, Ilocos Norte, Cagayan, Quezon and the Bicol Region. The first button manufacturing company in the Philippines was established in 1911 and thus stimulated shell gathering on a commercial scale (Matic, 1970). Materials and Equipment sea shells cutter bleaching solution grinder cooking box driller sorting machine turner Procedure (Garcia, 1959) 1. Cutting. Cut the shells according to the growth of the shells. Different cutters are provided for different sizes of buttons. Grade the cut shells according to size and thickness. 2. Grinding. Transfer the sorted shells to the grinder to remove the outer covering. 3. Turning. Place the ground buttons on the turner to smoothen the edges of the cut shells. Sort the shells again. 4. Drilling. First soak the buttons in water to facilitate drilling. 5. Bleaching. Dip the drilled buttons in a solution of concentrated acids and other chemicals like muriatic acid, sulfuric acid, sodium hydroxide, soda and pumice stone. Leave the buttons in bleaching solution until they become white. 6. Cooking. Transfer the bleached buttons to the cooking box (wooden) lined with pumice stones along the sides. This box continuously turns causing the buttons to shake and rub against the walls of the cooking box. This motion makes the buttons very shiny and smooth. 7. Sorting and packing. Sort the buttons manually as to class (first, second, etc.). Pack the finished buttons in carton boxes for storage or distribution. 13.9.2.2 Kapiz Shell Lamination Kapiz, window-pane oyster (Placuna placenta), also known as "lampirong" in Visayan, is probably one of the most valuable mollusc shells in the Philippines. Its light and translucent appearance and versatile use make it attractive for shellcraft and ornamental decorations. It is utilized as window-pane material 212 Minor Aquatic Products and in the manufacture of shellcraft products like lampshades, lantern shields, screens, trays, place cards, picture frames, pearl essence for pearl beads, and other novelties for homes and offices. In marketing kapiz, the right valves are called flat (landay) and the left valves, bent (lacon). Shells that square above 80 mm are classified as "head" while those that square 75 to 79 mm are classified as "first-flat" and "first-bent", shells that are 70 to 75 mm square are "second" and those that square from 60 to 70 mm are "third". All shells that square less than 60 mm are graded as "fourths" (Magsuci et al., 1980). The kapiz industry is quite old, but still a cottage industry for many people living near the coastal areas. The meat of kapiz is edible and contains higher protein (23.3%) than mussel and oyster meats. The dried kapiz meat is used as a component for poultry and shrimp feeds due to its high protein and calcium content. (Darvin, 1992) Minced Fish Processing Minced fish processing aims for the maximum utilization of fish flesh for direct human consumption. Processing into mince is often done for fish which have low market value, are seasonal and are caught in abundance. Minced fish can offer opportunities for utilization of fish in products of various shapes and sizes. Minced fish is made by passing a whole gutted fish body, fillet, fish frame or other parts of the fish over a drum having small perforations, around 1-7 mm in diameter. Pressure applied to the fish forces the soft meat portions through the holes while the bones, fins, skin and scales remain on the outside of the perforated drum. These machines are commonly termed as meat-bone separators or deboners (Connell and Hardy, 1982; Wheaton and Lawson, 1985). Deboners are undoubtedly efficient in recovering in minced form even the edible flesh, which remains on the skeleton after the usual process of industrial preparation. Minced products are manufactured and consumed in most of the Southeast Asian nations. The products include fish jelly products, fish and prawn sausages and burgers. These are mainly eaten as is or in soups, and cooked with noodles, rice and vegetables (Ng et al., 1991). They can be made from minced meat and/or surimi. 10.1 Fish Mince Trimmings from manual or machine filleting operations were the original source of fish mince. These trimmings were used in fish sticks (fingers) and portions, which could be battered. The main difference between fish mince and surimi is that there is no separation of the sarcoplasmic proteins (albumin, myoglobin, and enzymes) and lipids in fish mince (Hall and Ahmad, 1997). The presence of Fish Processing Technology in the Tropics J. Espejo-Hermes (2004) 111 Minced Fish Processing enzymes, haem pigments and lipids makes the fish mince unstable during frozen storage. Best quality mince can be prepared using only single species. In this case, less stable fish minces cannot "contaminate" the better-quality material. 10.2 Surimi Surimi (Fig. 23) or minced fish paste is a Japanese term for a semi-processed frozen minced fish protein, where the minced meat has undergone leaching by water, and additives such as sugars and polyphosphate have been added. The manufacture of products from minced and washed fish evolved around 1100 AD in Japan. In 1959, a team of Japanese scientists from Nishiya discovered a particular method of stabilizing the muscle proteins of surimi during frozen storage. They found that by washing out water soluble components from the minced fish and adding cryoprotectants such as sugars and polyphosphates, the functional properties could be lengthened throughout the freezing and frozen storage process (Okada, 1992). 10.2.1 Raw Material (Fish) Technically, any fish can be utilized for surimi production. However, white-fleshed marine fish such as Alaska pollock (Theragra chalcogramma) and blue whiting (Micromesistius poutassou) are the most common and preferred raw materials for surimi manufacture. The imposition of restrictions in the harvest of these temperate species is slowly changing the trend to the use of tropical trawl Fig. 23. Frozen Surimi (Source: Tan et al., 1988) 112 Minced Fish Processing by-catch such as threadfin bream (Nemipterus spp.), big-eye snapper (Priacanthus spp.), barracuda (Sphyraena spp.), croaker (Pennahia spp.), fusilier (Caesio spp.), and lizardfish (Saurida spp.) as raw materials for surimi. However, even this trawl by-catch is dwindling, so cultured species such as carp and tilapia will be potentially important as raw materials for surimi production. 10.2.2 Cryoprotective Agents Cryoprotective additives in the form of carbohydrates such as sucrose and sorbitol are commonly added to surimi before freezing to reduce protein denaturation brought about by the freezing procedure. Cryoprotectants bind with the protein molecules resulting in increased hydration of the protein molecules, slower ice crystal growth and incomplete freezing of water, hence lessening the degree of denaturation (Matsumoto and Noguchi, 1992). Sucrose and sorbitol are cheap, easily available, and have a low tendency to impart browning (Maillard reaction) to surimi-based products. These carbohydrates, however, give a strong sweet taste, which may be unacceptable in some surimi-based products. Other non-sweet additives such as lactitol, lactose and polymers (polydextrose and maltodextrins) could be potential replacements (Villasenor, 1995). Some hydroxycarboxylic acids (malonic, maleic, lactic, malic, gluconic and glycolic acids) and amino acids and their salts (glutamic acid, aspartic acid and sodium glutamate) could also serve as cryoprotectants in surimi. 10.2.3 Polyphosphates Food grade polyphosphates such as sodium tri-polyphosphate and sodium pyrophosphate are used widely in the manufacture of surimi. The addition of phosphates in minced meat is believed to enhance the water-holding capacity of frozen surimi resulting in a smoother paste during processing into fish jelly products (Tan et al., 1988). However, Matsumoto and Noguchi (1992) claimed that phosphates act mainly to intensify the cryoprotective effect of sugars rather than giving any direct cryoprotective effect of their own. It is recommended that the polyphosphate levels in surimi should not exceed 0.3%. 10.3 Processing of Surimi Raw Materials Only fresh fish must be used for surimi processing. Good quality frozen surimi is only obtained from fresh fish. Any species of fish with good gel-forming 113 Minced Fish Processing ability and white meat color can be used. Low price and availability are the prerequisites for suitable raw material for surimi production. The raw material must be kept at low temperatures before processing (Miyake et al., 1985; Tan et al., 1988 and 1994). Meat-Bone Separation The fish are beheaded, gutted and washed in chilled water before passing the fish through a deboning machine. Deboning can be done by using a belt-drumtype deboner, an auger-screen machine or hydraulic ram type equipment. The beltdrum-type compresses the fish against a steel plate drum in a rotating motion. Drum perforations range from 1 to 5 mm and the machine can process 0.2 kg to 3.5 tons of fish per hour. In the auger-screen machine, an auger rubs along the inside of a drum with much smaller holes (about 0.5-1.5 mm) to move and crush the material. The most advantageous deboner is the hydraulic-ram type. The heat build-up in the fish flesh is decreased in this machine since the flesh is squeezed through a screen in an automatic batch-type system (Villaseñor, 1995). Leaching Leaching or washing is one of the most significant steps in surimi production because it improves gel-forming capacity. Leaching is done to attain the following: λ increase in the elasticity (gel-forming property) of kneaded products λ removal of fat, skin and blood thus improving the color and appearance of the meat λ removal of off-odors λ production of a bland tasting meat, thereby making product formulation easier by adding flavors to suit consumer taste λ improved resistance to damage during freezing On the other hand, leaching removes the water-soluble proteins and the natural flavors of the meat. The leaching process involves the following: λ washing the meat 2-3 times with 4-5 times its volume of chilled water (10-15oC) with 0.2-0.3% salt. Salt is added during washing to facilitate the removal of water from the minced meat. For fish with considerable dark meat such as sardines, sodium bicarbonate is added during leaching to adjust the pH of the meat thereby improving the gel-forming ability. 114 Minced Fish Processing λ stirring the mixture λ separating skin, fat and blood by allowing the meat to settle λ decanting water and fat λ passing the meat through a nylon mesh or a rotary sieve The leaching process may utilize simple equipment such as pails and nylon mesh or more sophisticated equipment such as stainless-steel tanks, rotary sieves, pump, strainer, washing shower and others depending on the scale of production. De-watering or Dehydration The water is removed from meat tissues after leaching or washing. The water content of the meat after leaching should be 85% by weight. Dewatering can be done using either a continuous operation with a screw press, hydraulic press, or a centrifuge. For a small-scale operation, a cheese cloth or nylon mesh can be employed. Very high-quality surimi is produced when the temperature of the meat does not rise during the pressing operation. Straining This step removes the remaining scales, connective tissues, and small bones. A strainer with a forced cooling system will be most efficient in removing these residues. Mixing After straining, the meat is mixed well with additives such as sugar and polyphosphates using a mixer, grinder or silent cutter. The recommended level of sugar in surimi is 3-5% while polyphosphate level should not exceed 0.3%. The mixture is then packed in 10- kg polyethylene bags and quick-frozen in a contact or air blast freezer at -30oC. 10.4 Quality Assessment of Surimi The quality of surimi is based mainly on its gel strength and color. These factors depend on fish species, freshness, processing method and control, moisture content, control of freezing and storage temperature as well as handling and distribution conditions. Gel strength can be measured objectively by using a rheometer or a tensiometer and by sensory evaluation, folding and teeth-cutting tests (Tan et al. 1988). The degree of whiteness of the surimi (as required for fish 115 Minced Fish Processing balls and fish cakes) can be measured using a whiteness meter. Good quality surimi has the capacity to absorb water 30% or more of its own weight, and results in cooked products of acceptable firmness with a springy, gel-like texture. 10.5 Manufactured Products Minced fish and/or surimi can be utilized in imitation products (crab legs, scampi, shrimp dumplings, etc.) or in traditional foods such as fish/shrimp/squid balls, nuggets, sausages, burgers and others. Minced fish products are classified as intermediate moisture food (IMF) because of their high moisture content which shortens their keeping quality. The shelf life of these products range from three days at room temperature to six months when vacuum packed (Ng et al., 1991). For export purposes, these products must be frozen to lengthen their keeping time. 10.5.1 Fish Balls Fish balls are a favorite food in the Philippines and are sold in many public places such as markets and parks. Fish balls are usually sold frozen in supermarkets and are retailed by ambulant vendors in fried form. Materials and Equipment Per kg mixture minced fish or frozen surimi (940 g) knife cornstarch (30 g) bowls salt (20 g) mincer baking powder (10 g) plastic bags monosodium glutamate (5 g) Procedure (Marfori et al., 1991) 1. Use fresh fish for minced fish or frozen surimi. If frozen surimi is used, temper (controlled thawing at -9oC) and pass through a silent cutter. Add water equal to 30% of the weight of the frozen surimi. 2. Mix minced fish with salt to make a paste, then add other ingredients. 3. Form into balls manually or use fish ball forming machine. 116 Minced Fish Processing 4. Set the balls by placing them in water (40-45oC) for 20-30 minutes. 5. After setting, cook product in boiling water or steam. 6. Cool after cooking and pack in plastic bags. 7. Store in a chiller or freeze. 10.5.2 Fish Burger Minced meat from tuna and tuna-like species is a suitable raw material for this product. Materials and Equipment minced fish, 2 c knife salt, 2 tsp. chopping board bread crumbs, ½ c (soaked in ¾ c water) mixing bowl onion, 2 tbsp (minced) burger press garlic, 1½ tsp. (minced) frying pan black pepper, 1 tsp. (ground) polyamide/ flour, 4 tbsp polyethylene bags bread crumbs for coating cooking oil Procedure (Espejo-Hermes and Tumonde, 1993) 1. Mix well the minced fish and salt. 2. Add soaked bread crumbs, onion, garlic, black pepper and flour to the fish:salt mixture. 3. Moisten hands with water, take 2-3 tablespoons of fish mixture and press to shape burger (alternatively, a burger press can be used). Continue with the rest of the mixture. 4. Coat burgers with bread crumbs. 5. Heat cooking oil in pan and fry burgers until brown. 6. For longer shelflife, pack fried burgers in polyamide/polyethylene bags and freeze. 117 Minced Fish Processing 10.5.3 Surimi-Shrimp Value Added Products Surimi can be mixed with shrimps to produce shrimp analogues that can compete reasonably with traditional shrimp products which are expensive. 10.5.3.1 Nuggets Nuggets consist of surimi paste, shredded meat (shrimp) and ingredients. They usually come in bite-sized rectangular shapes. Nuggets are yellowish in color and crunchy when fried. Materials and Equipment Per kg mixture frozen surimi (466 g) commercial batter mix shrimp meat (200 g) bowls iced water (100 g) spatula onions, chopped (85 g) silent cutter breadcrumbs (57 g) molders cooking oil (10 g) polyethylene bags/ wheat flour (45 g) polystyrene trays/ salt (9 g) paperboard boxes sugar (6 g) garlic, chopped (6 g) Procedure (Abella et al., 1995) 1. Pre-cool silent cutter with ice. Cut tempered surimi into cubes. Grind. 2. Add salt. Continue grinding until mixture becomes sticky. 3. Add onions, and garlic. Mix thoroughly. 4. Add one half of iced water. Continue mixing for about 2 minutes. 5. Add flour, oil, breadcrumbs and sugar. Mi