Food Fats and Oils: Extraction, Composition, Utilisation PDF

The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. 13 Table of Contents Chapter 2..........

The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. 13 Table of Contents Chapter 2.......................................................................................................... 15 INDUSTRIAL PRODUCTION OF FATS AND OILS.....................................................15 2.1. Factors Affecting Extracted Oil Quality......................................................15 2.2. Oil Extraction............................................................................................. 15 2.2.1. Criteria for Evaluating an Oil Extraction Process.................................15 2.3. Vegetable Oil Extraction............................................................................16 2.3. 1. Pretreatment of oilseeds....................................................................16 2.3.2. Oil extraction from pre-processed oilseeds.........................................20 2.4. Miscella distillation and meal desolventisation..........................................26 2.4.1. Miscella distillation..............................................................................26 2.4.2. Meal desolventisation..........................................................................27 2.4.3. Toaster desolventisation.....................................................................27 2.4.4. Flash desolventization and cooling......................................................31 2.4.5. Vacuum stripping................................................................................ 31 2.4.6. The vapour desolventizer....................................................................32 2.4.7. The Crown Iron Works’ Down Draft Desolventizer (DDD)....................33 2.5. Extraction of Palm (Elaeis guineensis) Mesocarp Oil, Palm Kernels, and Palm Kernel Oil................................................................................................. 34 2.5.1. Oil yield................................................................................................... 34 2.5.2. Bunch sterilisation............................................................................... 35 2.5.3. Bunch stripping and fruit digestion.....................................................36 2.5.4. Clarification......................................................................................... 36 2.5.5. Separation of nuts from palm press fibre............................................37 2.5.6. Extraction of kernels from nuts...........................................................37 2.5.7. Extraction of palm kernel oil (see section 2.2. above).........................37 2.6. Recovery of Animal Fats............................................................................ 37 2.6.1. Raw material sources..........................................................................37 2.6.2. Rendering Product Specifications........................................................39 2.6.3. Basic principles affecting rendering quality.........................................40 2.6.4. Fat recovery processes........................................................................41 2.6.5. Inedible raw materials.........................................................................41 2.6.6. Edible fat rendering............................................................................. 42 The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 14 2.7. Marine Oils................................................................................................. 43 2.7.1. Raw materials...................................................................................... 43 2.7.2. Production........................................................................................... 49 2.7.3. Harvesting........................................................................................... 52 2.7.4. Raw material quality...........................................................................54 2.7.5. Cooking............................................................................................... 54 2.7.6. Pressing............................................................................................... 54 2.7.7. Separation of press liquor...................................................................54 2.7.8. Stick water evaporation.......................................................................55 2.7.9. Drying and processing of the presscake..............................................55 2.7.10. Grinding............................................................................................. 55 2.7.11. Cooling and stabilisation...................................................................55 2.7.12. Packaging of fish meal......................................................................55 2.7.13. Oil polishing....................................................................................... 55 2.7.14. Other marine oil production processes..............................................57 2.7.15. Enzymatic hydrolysis.........................................................................58 2.7.16. Autolytic silage production................................................................59 2.7.17. Dry rendering.................................................................................... 60 2.7.18. Solvent extraction.............................................................................61 2.7.19. Acid-alkali aided process...................................................................61 2.8. Marine oils produced for the omega-3 market...........................................61 2.8.1. Krill...................................................................................................... 62 2.8.2. Fish livers............................................................................................ 63 2.9. Refining of fish oil...................................................................................... 64 2.10. Hardened edible oils and fats from fish oils.............................................69 2.11. Single cell oils.......................................................................................... 69 2.12. REFERENCES............................................................................................ 71 Chapter 2 The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 15 INDUSTRIAL PRODUCTION OF FATS AND OILS 2.1. Factors Affecting Extracted Oil Quality The quality of oil from the extraction process depends on the handling of the oil-bearing material prior to processing. Four basic considerations serve to guide any good fat recovery operation and process selection. These are: Time Raw material quality usually falls with time. Temperature Unless placed under strict control, temperature accelerates raw materials deterioration. As is found in most chemical reactions, every 10oC rise in temperature doubles raw material hydrolysis. Particularly harmful to the quality of oleaginous (oil-bearing) material and also to the product and by-product, is the temperature range in which lipolytic and proteolytic organisms thrive. Microorganisms and enzymes Poor harvesting schedules, handling and storage of oleaginous materials, their products and by- products can lead to loss of quality. Unhygienic handling may result in infection of oleaginous material by spoilage microorganisms. Over ripening of fruits or bruising may bring endogenous oil and enzyme together, resulting in hydrolysis of the former and the development of off-flavours. Moisture Raw materials for oil extraction, if not properly dried, will undergo deterioration during storage due to microbial infection. Excessive moisture may also impair oil extraction. 2.2. Oil Extraction 2.2.1. Criteria for Evaluating an Oil Extraction Process “On delivery of the raw material to the processing unit with all the care and dispatch that economics will permit, the extraction procedure itself should meet, as much as possible, the following criteria (Rose, 1954): i. The process should deliver the theoretical yield of the products as determined in the raw material. ii. The process should yield product quality equivalent to that known to be present in the raw materials received. iii. The process must be sufficiently flexible to handle economically and efficiently, all the classification of raw material to which it will be applied. iv. The process must adequately maintain its efficiency and quality under variable load conditions from day to day and season to season, as the supply of raw material varies. v. The process must be inherently self-contained and clean, producing no nuisance and preferably no process discharge that is not a saleable product. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 16 vi. The process should require a minimum of labour and of electrical, chemical and thermal energy. vii.The process should be as simple as possible mechanically, to the end that capital investment, repair, replacement, taxes and insurance costs are kept at a minimum.” 2.3. Vegetable Oil Extraction Vegetable oils are of two types, seed oils, such as soybean, palm kernel, and coconut oils, and mesocarp (fruit coat, pulp) oil, for example olive oil and palm oil. Extraction of crude oil from vegetable raw material is done by mechanical pressing and/or solvent extraction. Both processes can be applied separately or in combination. Residual oil contents of 3-25% in expeller cakes are achieved by mechanical pressing compared with residual oil content of 0.5- 1.0% in extracted meal from solvent extraction. The solid, often protein rich component remaining after solvent extraction serves (after adequate treatment) as a high-grade animal feed. By modifying the process, these products can be turned into ingredients with high protein solubility for human consumption. 2.3. 1. Pretreatment of oilseeds 2.3.1.1. Shelling, cracking, dehulling The seed is usually enclosed in a shell or a tough outer covering (endocarp, as in the case of palm nuts), or a pod which encloses the seeds as in soybeans and groundnuts, which have to be broken in order to release the seeds. Some oilseeds, such as soybeans have a seed coat or hull (which constitutes about 8% of the soybean), which must be removed before oil extraction in a process known as dehulling. The hard covering of palm nuts is cracked open to release the seeds (kernels). Manual removal of the pods enclosing the seeds, dehulling, and cracking are slow, and these are no longer practiced. Breaking of the endocarp and pods and the separation of the oilseeds, as well as dehulling are performed mechanically. In the processing of certain soft oilseeds by the use of expellers, dehulling may be omitted in order to improve the efficiency of extraction, or some seeds are left in the pods and pressed (as in the case of groundnuts) to aid oil extraction when using a small expeller (without this, peanut butter, and not oil would be produced). The resulting groundnut cake, in this case, is of low quality, being of high fibre content. In the case of soybeans, the seeds are dehulled in order to obtain a high protein meal of high digestibility after solvent extraction. 2.3.1.2. Cleaning The processing steps involved in oil extraction are determined by the nature of the oil- bearing material. Oilseeds require several preliminary steps. The prime task of any seed preparation plant is to process seeds in such a way that, under normal circumstances, the expeller or solvent extraction plant can remove the oil in an economical way. The basic technological steps for processing soybeans in today’s modern and highly efficient oil mills are shown in Figure 2.1. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 17 Figure 1.1. Soybean preparation for oil extraction (Keller, 2011) It is very important that care be taken in the handling and shipment of oilseeds, due to their susceptibility to microbial infection resulting in the build-up of free fatty acid and/or rancidity. Infestation by pests can also lead to losses and contamination. Oilseeds are usually screened to remove stones, straw dust and other impurities. The first step of the cleaning is the removal of tramp metal by means of a rotary type magnet separator. This is followed by screening in which the first on-stream cleaner should be provided with a rough scalping screen or perforated metal sheet to separate oversize trash and below that a second sieve to get rid of the sand. To separate light-weight particles, mainly hulls and dust, the second sieve must also be provided with an aspiration channel. As an average one can estimate 1% impurities will be obtained in this cleaning section. In small mills tramp iron is removed manually or by magnetic separators. Screening to remove other extraneous material is carried out by shaking the oilseeds manually or mechanically in a sieve. Figure 2.2. Size reduction and heat treatment of oilseeds prior to oil extraction (Lurgi, 1987) 2.3.1.2. Size reduction First the oilseeds are passed through roller mills for preliminary size reduction (Figure 2.2). This is done by cracking rolls. Most cracking rolls comprise an integral feeder with a The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 18 permanent magnet and two pairs of corrugated rolls arranged one on top of the other so that the first set of rolls feeds the second set. Milled oilseed is cooked to break down the walls of the oil-bearing cells followed by drying to reduce moisture content. It is further passed through plain roller mills for further size reduction, before extraction. In small-scale facilities, smaller equipment is employed for crushing and cooking. Usually, a hammer or attrition mill will suffice for size reduction while a shallow open pan with a mechanical stirred, or a cabinet dryer, will suffice for cooking of ground oilseed and drying to suitable moisture content. Size reduction exposes more surface for the subsequent heat treatment (scorching or cooking), which serves to break down the cell walls and facilitate oil extraction. 2.3.1.3. Conditioning Oilseeds such as soybeans, which have high phosphatide content, may be subjected to an additional conditioning treatment, such as the Lurgi Alcon Process (Lurgi, 1987). In this process (Figure 2.3), moisturising media (preferably steam) are added to the oilseed flakes from the roller mills in the conditioner until the moisture content is above 15%. The temperature rises to approximately 100oC. The conditioning parameters are then kept constant for a period of approximately 15 minutes. Simultaneously, an agglomeration effect arises, which increases the bulk density. The phospholipases are inactivated by this treatment; the phosphatides in the extracted crude soybean oil thereby remain hydratable, and the conditions for physical refining are created by the low residual phosphatide content of approximately 10- 15 ppm in the degummed oil (Figure 2.3). Advantages claimed for the process are as follows: i. Higher bulk density ii. Larger extraction capacity iii. Higher percolation speed iv. Lower hexane retention v. Better hydration of phosphatides vi. Higher yield of lecithin vii. Lower residual phosphatide content in crude oil viii. Crude oil suitable for physical refining ix. Better meal quality The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Figure Utilisation. Copyright 2.2. Process for © 2022 byconditioning additional Fred O.J. Oboh. All rights of soybean reserved. flakes before Amazon Kindle Paperback. ISBN: 9798361143030. extraction185pp. (Lurgi, 1987).  F.O.J. Oboh. Industrial production of fats and oils 19 2.3.1.4. Expanding This process, was introduced by the Anderson International Corp, and has been in use since the 1960s. It is similar to the Alcon Process and achieves similar results (Boeck, 2011). The expander consists of a cylindrical horizontal housing, with a rotating shaft which has a screw- like shape. Figure 2.3. Annular gap expander with hydraulic cone (Boeck, 2011). The product - typically cracked and flaked soybeans - is introduced at one end and the motor- driven worm shaft conveys the product to the other end. Here it has to pass through a die plate or a narrow annular gap. This reduction in free cross-sectional area leads to a considerable pressure build-up and high shear forces within the product layer. Shearing generates heat in the product. The temperature increase may be supported by additional injection of sparge steam through special pins bolted onto the housing extending into the product. During the expanding process the temperature may rise above 150°C starting from ambient temperature. Due to a very short retention time of the product in the expander (approximately 1 minute), this heat treatment has hardly any negative impact on the protein quality. It may actually be advantageous, for the following reasons (Boeck, 2011): i. The stabilization of rice bran by lipase inactivation ii. Inactivation of anti-nutritional factors (e.g., gossypol in cottonseed meal) iii. Reduction of pathogenic microbial count iv. Increase in the content of ruminally non-degraded protein. Oil yield is improved due to the following: i. Upon discharge of the pressurized product into the atmosphere, there is an intense flash evaporation of the water in the seed, which destroys some of its cellular structure thereby The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 20 giving access to the oil droplets within the seed and improving the oil yield in the subsequent oil separation process. ii. The flash evaporation also creates new capillaries in the product to improve diffusion and mass transfer processes during solvent extraction, and to make the product more porous, as it expands at discharge from the machine. iii. The product becomes more porous and its density decreases due to flash evaporation, with the bulk density of the expanded product being considerably higher than the bulk density of the flakes at feed point. This effect is widely used to increase the capacity of existing extractors. Thus, at identical extraction times, the mass flow rate can be increased using expanders. iv. The porous product structure helps to maintain high percolation rates and thus high oil yields. v. The solvent carryover to the subsequent desolventizing step is considerably less, compared with the processing of conventional flakes, which leads to additional steam savings. Major disadvantages in the use of expanders are as follows: i. First, the high frictional forces in the expander lead to both high electricity consumption and wear on the internal worm parts and the die plates, which add to the operating costs. ii. The flash evaporation together with the high product temperature requires good aspiration and cooling systems since free moisture and excessive temperature are critical for solvent extraction. iii. The system is also limited in its application to low oil content products. Seeds with a high oil content (i.e., >40%), such as rapeseed (canola) and sunflower seed, typically do not allow for a sufficient pressure build-up in the units to gain similar effects as seen with soybeans. 2.3.2. Oil extraction from pre-processed oilseeds These steps are followed by oil extraction using an expeller and/or solvent. Expellers for oil extraction from oleaginous material operate continuously and automatically. The expeller consists of a screw or worm, which pushes the oil rich material forward continuously in a horizontal barrel or cage, exerting at the same time, sufficient pressure to force oil through openings in the cage (Figure 2.5). Expellers are commercially available with capacities from a few kg/hr to several tons/hour. Modern units reach 800 tons per day with installed motors of up to 630 kW (www.desmetballestra.com) The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 21 A B C The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 22 D Figure 2.4. Expellers A, B, C, and D A. Small oil expeller with capacity up to 150 kg seed/hr (Fellows and Axtell, 2012). B. Medium capacity100 series Sterling, 75-100 TPD, prepress, 15- 20TPD full press C. High capacity 800 series Sterling, prepress 650- 800 TPD, full press, 120-150 TPD ([email protected] www.Rosedowns.co.uk, www.desmetballestra.com) D. Inside view of a modern high-capacity screw press (HF Press+LipidTech) revealing the worm and cage (Boeck, 2011) 2.3.2.1. Pressing of pre-processed oilseeds A screw press consists of a continuous screw auger designed to take feed material and subject it to gradually increasing pressure as it is conveyed through a barrel cage composed of bars surrounding the screw and oriented parallel to the screw axis. The bars are separated by spacers decreasing in size towards the solid discharge end which allow the oil to drain. In operation, the meats or flakes fall into a rapidly rotating feed screw, which feeds them into the pressing cage to expel entrapped air and squeeze out the easily removed oil. A plug of compressed oil-lean solids, the cake, forms at the discharge end. Increasing pressure down the length of the barrel is achieved by increasing the root diameter of the screw, decreasing the pitch of the screw flights, and controlling the opening for the discharge cake by means of a choke. This design causes the material to be rammed against the plug (Ward, 1976; Bredeson, 1977; Johnson, 2002). Oil yield from the screw press depends on, and can be maximized by appropriate seed preparation. The mechanical seed preparation is primarily important to gain access to the oil droplets within the cellular structure of the seed. However, total destruction of the cell walls leads to a ground product which lacks sufficient structure to allow for pressure build-up and oil separation. The classical flaking step gives the compromise between easy access to the oil and a product matrix that permits pressing. A similar phenomenon limits processing of dehulled seed. A certain amount of hull in sunflower and rapeseed (canola), or groundnut (peanuts) pods The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 23 adds to the structure and is necessary for an economical pressing plant operation (Johnson, 2002; Fellows and Axtell, 2012). The seed is usually flaked to a thickness of 0.38 – 0.50 mm, before cooking at 115 oC over a 60-min period prior to full (hard) pressing. Initial stages of cooking should be done with moist heat by injecting steam or spaying water into the top deck of the cooker/dryer, with moisture content maintained at 10%. Cooked flakes are dried in lower trays and should leave the cooker/dryer at less than 2.5% moisture (Bredeson, 1978). Appropriate grinding, an important factor for a successful pressing operation, is provided by shaft geometries comprising of several high-pressure and high-shear force zones over the length of the shaft in combination with mixing rings of various shapes. These features constitute a grinding unit, thus making upstream mechanical seed preparation less critical. The thermal seed preparation (cooking) serves to adjust temperature and water content. The temperature appears to be of secondary importance, but it is linked to the drying efficiency of the cooker/ dryer unit. The water content has a very strong impact on the friction between seed product and press internals, and consequently on the pressure build-up and with that, on de-oiling (Boeck, 2011). The pressing process is either used in combination with solvent extraction (pre-pressing), or as a true mechanical oil extraction process (hard- or full-pressing). Full (high-pressure) pressing reduces the oil content to 3-15%. Pre-pressing (low-pressure pressing) leaves residual oil content of 15-18% in the pre-press cake (Johnson, 2002). The expeller is the ideal oil extraction equipment for small and medium scale operations. Capacities range from less than 100 kg to over 100 tons per day of oilseed with residual oil content in cake of 3 to over 25%. They are also suitable for large mills, where they are used alone or in combination, to pre-press oilseeds prior to solvent extraction or for full pressing at a higher pressure. Large pre-press expellers can process over 600 tons of oilseeds per day (Figure 2.5). A pre-press is usually followed by cooking and drying of the cake followed by a complete press at a higher pressure in another expeller or by solvent extraction. The cake from a pre-press operation is milled before extraction with solvent. Residual oil content of 0.5% to 1% in the extracted meal can be obtained by solvent extraction. Table 2.1. Major sources of edible fats and oils and methods of processing (Adapted from Johnson, 2002) Source Oil content (% Prevalent method of recovery dry wt.) Soybean 19 Direct solvent extraction Corn (germ) 40 Wet and dry milling and prepress, followed by solvent extraction Tallow (edible tissue) 70-95 Wet or dry rendering Canola 42 Prepress followed by solvent extraction Coconut (copra) 66 Full pressing. May be followed by solvent extraction of oilseed cake. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 24 Cottonseed 15-25 Full pressing or prepressing before, or direct solvent extraction. Lard (from edible tissue) 70-95 Wet or dry rendering Oil palm mesocarp (wet) 56 Complete (high pressure) pressing Palm kernel 46-57 Full pressing. May be followed by solvent extraction of the kernel cake. Groundnut (peanut) 38-50 Full press, or prepress followed by solvent extraction The mode of extraction of oil from an oilseed depends to a large extent on its texture and its oil content. Hard kernels such as palm kernels require seed preparation and pressing equipment which are somewhat different from those required by soft oilseeds, for example groundnuts and sunflower seeds. Another consideration is oil content. Usually, high oil content seeds require a pre-pressing stage prior to final pressing or solvent extraction. On the other hand, materials of low oil content, for example soybean, rice bran, dry-milled corn germ, or expeller press-cake may be subjected to a straight solvent extraction (Table 2.1). It is possible to eliminate the pre- pressing stage prior to solvent extraction by employing direct solvent extraction of high oil content material using a combination of percolation and immersion extractors, such as in the Direx Process (Bernadini, 1977). 2.3.2.2. Solvent extraction Oil extraction with expellers leaves 3-15% residual oil in the solids, the process uses considerable horse power, there is considerable wear and maintenance, and it takes several machines for high capacity. In comparison, solvent extraction with hexane (the primary solvent used worldwide) will remove all but about 0.5-1.0% of residual oil, uses less horse power, and requires less maintenance. It is relatively efficient and reliable, and this is one reason why solvent extraction is the primary means of separating large tonnages of oil from protein meal. Hexane has about the best characteristics of the many solvents tried over the years for the following reasons (Anderson, 2011): i. It has a boiling point of 69°C and is a liquid in all but the most extreme climates of the world. ii. Due to its fairly high volatility and a low sensible heat of 335 kJ/kg, it is relatively easy to remove from the solids and oil with low energy use. iii. It forms an azeotrope in the presence of water or steam, with a slightly reduced boiling temperature of 61.6°C resulting in a vapour coming off at about 95% by weight hexane and 5% by weight water. The azeotrope is convenient for efficient removal of the solvent from solids (or “meal”) using direct steam contact. iv. The solvent has a long record of use without as much human skin irritation or the immediate or severe toxicity of many competitive solvents. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 25 v. It is immiscible with water, allowing fairly simple processes to keep it in the system, while water passes through the extraction process as moisture in the seed, meal, oil, or air. It is highly capable of mixing with the pre-processed oil-bearing material, and dissolving and washing the desired oils out of the fibrous or solid material. vi. Being a non-polar solvent, it selectively dissolves the oil, leaving the hydrophilic contents (such as proteins, sugars and some gums), which are undesired in the oil largely undisturbed in the meal. vii. It has a relatively tolerable odour and a low tendency to cause discomfort when one is subjected to a brief exposure. Flake thickness (Coats and Wingard, 1950; Myers, 1977; Fawbush, 1981) and solvent temperature (Wingard and Phillips, 1951) have profound effects on extraction rate, and empirical relationships have been observed between these factors and extraction time. The moisture content of the flakes also affects the rate of solvent extraction, and a moisture content of 9-11% is recommended (Johnson, 2002). The extractor is an enclosed vessel designed to wash, extract, and drain flakes. Countercurrent flow of the solvent and flakes serves to reduce the amount of solvent used in extractors, with the new flakes making contact with the oldest solvent, and progressing through the process until nearly oil-free flakes contact the fresh solvent. Two principal types of extractors have been employed over the years. These are as follows (Johnson, 2002): The immersion extractor The immersion extractor immerses and soaks the material in the solvent (rather like the operation of a laboratory Soxhlet extractor). The percolation extractor In the percolation extractor, the solvent percolates by gravity through a bed of material. The solvent flows over the surface of the particles and diffuses through the material. Miscella flows in successive passes, through the bed, while the solvent spray and the bed move in opposite direction to each other. Generally, more solvent usage is required by immersion extractors. Few immersion extractors remain in use, and percolation extractors now dominate (Johnson, 2002). The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 26 Figure 2.6. Diagram of percolation extractor (Anderson, 2011) A percolation-type extractor (Figure 2.6) is commonly used for the removal of oil from oilseeds, such as soybeans, canola, sunflower kernels, corn germ, palm kernels, copra, linseeds, cottonseeds, castor beans and groundnuts, as well as residues and expeller cakes of these oilseeds from mechanical pressing, rice bran, and fish meal. In this type, the extraction solvent drains down through a porous bed of material and through a screen which supports the material. As the solvent (usually hexane) passes down through the bed of oil-bearing material, the oil is dissolved in the solvent and carried away. When properly carried out, the extraction process results in a very good separation of the edible oil from the solids or nutritious meal fraction. Figure 2.7 shows a simple diagram of this, a simple straight-line extractor in which the solids are going from left to right in a machine, and the solvent is entering at the right end of the machine. The fresh solvent is first passed through the solids which have already been fairly well extracted. The solvent is then reused in multiple stages towards the left end, passing through the bed repeatedly, picking up oil and becoming a more concentrated miscella. This oil-rich miscella still has sufficient solvent content to extract effectively, further to the left, where the solids contain more oil. Finally, the miscella exits at the left end of the machine. The flow of the solids from left to right is opposite to the flow of the solvent from right to left The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 27 (countercurrent or counter-flow). Virtually all commercial extractors make some attempt to use this basic flow method (Johnson, 2002; Anderson, 2011). Figure 2.7. Diagram of the Crown Iron Works countercurrent flow extractor (Anderson, 2011) Flakes are conveyed to the extractor, where they are extracted for 30-60 minutes. Generally, less than 1% residual oil in the extracted material is achieved, with a lower content (about 0.5%) for soybeans (Johnson, 2002). 2.4. Miscella distillation and meal desolventisation 2.4.1. Miscella distillation The miscella contains 22-30% oil, and the solvent is separated from the oil by distillation and stripping columns by heating the miscella under vacuum in a two-stage evaporator. The first stage concentrates the oil to about 90% and uses reclaimed heat from heated solvent vapours from meal desolventisation. Steam is used to heat the second stage, where the oil is concentrated to >99%. A combination of heat, vacuum (450-500 mmHg absolute pressure), and steam sparging in a disc- and- doughnut stripping column serves to evaporate most of the remaining solvent. The vapour mixtures of water and solvent from individual distillation stages are condensed or further utilized in heat exchange (Johnson, 2002). 2.4.2. Meal desolventisation The de-oiled oilseed material from the solvent extraction process may be in the form of flakes, cake particles or expanded pellet particles soaked with solvent. The de-oiled oilseed material typically contains 55-70 wt % dry solids, 25-35 wt % residual solvent, 5-10 wt % moisture, and less than 1.0 wt % residual oil. The de-oiled oilseed material is normally at atmospheric pressure, with a temperature of 55-60°C. In many cases this material contains The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 28 anti-nutritional factors that can inhibit digestion. This de-oiled oilseed material has no commercial value, is unsafe to transport, and requires further processing (Kemper, 2011). Residual solvent is recovered from this solvent –laden flakes material (i.e., the marc), which generally contains 25-35 wt% holdup (i.e., solvent which will not drain), which must be expelled, recovered and recycled. The solvent is recovered from the meal by heating (toasting). Greater solvent holdup increases the energy required for desolventizing the meal. Depending on the feed material, harmful substances are simultaneously inactivated during the process. Toasting is required for meals for use as animal feed for the following reasons (Johnson, 2002; Kemper, 2011): i. To efficiently denature trypsin inhibitors (e.g., protease inhibitors in soybean which affect protein digestibility) ii. To denature the enzyme urease in soybean meal iii. To bind gossypol to protein in cottonseed meal iv. To improve protein digestibility. In the process of doing these, the protein undergoes considerable denaturation, with accompanying loss of water solubility. Depending on the method used, meals with various degrees of protein solubility and digestibility can be produced. There are two potential processing paths for the de-oiled oilseed material coming from the solvent extraction process. These are as follows: i. Over 95% of the de-oiled oilseed material is processed by the desolventizing, toasting, drying and cooling process path to produce protein-rich meal for animal feed ingredient applications. ii. Less than 5% of the de-oiled oilseed material is processed by the flash desolventizing and cooling process, or the low temperature desolventisation path to produce protein concentrates, protein isolates and soy flour for human and specialty animal feed applications. 2.4.3. Toaster desolventisation Meal desolventizing, toasting, drying, and cooling achieve the following results: i. Solvent is removed from the de-oiled oilseed material and recovered for re-use ii. De-oiled oilseed material is toasted to reduce anti-nutritional factors iii. De-oiled oilseed material is dried to within trading limit moisture requirements iv. The de-oiled oilseed material is cooled to near ambient temperature to remain flowable during storage and transport. The resultant desolventized, toasted, dried and cooled product is commonly referred to as oilseed meal (Kemper, 2011). The desolventizing, toasting, drying, and cooling processes can be accomplished in a single vessel referred to as a Desolventizer/Toaster/Dryer/Cooler (DTDC). The typical Crown-Schumacher counter-flow desolventizer/toaster/dryer/cooler consists of four trays (Figure 2.8): The top tray is for pre-desolventizing, the second for desolventizing-toasting with injection of steam through its perforated bottom (achieving The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 29 countercurrent use of steam relative to solvent evaporation). The third tray is for drying with hot air blown through its perforated bottom and the fourth tray is for cooling by blowing cold air through its perforated bottom (Kemper, 2011). Figure 2.8 Typical Crown / Schumacher Counter Flow Desolventizer/Toaster/Dryer (Kemper, 2021) More commonly, the desolventizing and toasting processes are combined in one vessel, referred to as a DT (desolventizer/toaster), and the drying and cooling processes are combined in a separate vessel referred to as a DC (dryer/ cooler). The desolventizing takes place in several stages mainly by adding live steam. Harmful substances, e.g., urease in soybeans can be inactivated simultaneously by wetting and a prolonged retention time. The meal is dried and cooled in separate downstream equipment. The conventional desolventizer/ toaster (DT) is usually composed of about six stacked trays (Figure 2.9), all with indirect heating (Johnson, 2002). The trays of the DT are designed with an upper plate, lower plate, and structural members between, designed to hold pressurized steam. The DT has four different types of trays: pre-desolventizing trays, countercurrent trays, a sparge tray, and a steam drying tray. The first two employ live steam injection through nozzles within the sweep arms to evaporate the greater part of the solvent. Meal advances down through the trays by agitating sweeps anchored to a central rotating shaft, with controlled levels in each tray. The lower four trays function essentially as toasting/drying sections, where the meal is held at a minimum temperature of 100 oC. Drying at normal DT conditions to less than 17% moisture is considered detrimental to the available lysine content of the meal, but meal should not leave the DT at more than 22% moisture content, as this results in prohibitive drying energy requirements (Johnson, 2002). The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 30 Figure 2.9. A conventional desolventizer/toaster (Kemper, 2011) Dryer/ Coolers (DCs) are vertical, cylindrical vessels with horizontal trays (Figure 2.10). The desolventized and toasted meal enters at the top, and is supported by the tray. The meal is mixed above each tray, and conveyed downward from tray to tray, by agitating sweeps anchored to a central rotating shaft. The trays of the DC are designed with an upper plate, lower plate, and structural members between, designed to distribute low pressure air vertically into the meal layer supported above. The DC has two different types of trays, air drying trays and air-cooling trays (Kemper, 2011). The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 31 Figure 2.10. Desmet Ballestra Dryer/ Cooler (Kemper, 2011) The air-drying trays are designed with a plurality of apertures across their entire upper surface to evenly introduce hot air into the meal. The size and quantity of apertures is calculated based upon the designed air flow rate to provide a pressure drop of 0.02-0.03 bar. These apertures are generally small round holes, with some DCs also using narrow slots. The DC many have from 1 to 6 air dryer trays. The number of air-drying trays is determined to allow adequate hot air to pass through the meal to remove moisture to the target value (Kemper, 2011). According to Kemper (2011), a consideration of the following factors is essential in determining the optimum DT and DC configuration for a given process application: i. Determining all input parameters and calculating the mass and heat balance of both the DT and the follow-on DC. ii. The mass and heat balance of the DC will determine the maximum allowable DT exit moisture, which will minimize meal drying energy. This moisture is generally in the range of 18-19%. With the DT exit moisture determined, the amount of direct steam introduced into the meal can be calculated. iii. The DT diameter is generally determined by the direct steam flow rate per unit area. It is important to have a sufficiently high direct steam flow rate per unit area for adequate solvent stripping. iv. The number of countercurrent trays is determined by the residence time needed to balance meal quality with residual solvent objectives. By calculating the total DT heat demand and subtracting the heat supplied by live steam, the total heat supplied by indirect steam can be determined. v. The total heat supplied by indirect steam less the heat supplied by countercurrent tray indirect steam will provide the amount of indirect steam heat needed to be supplied by the pre- The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 32 desolventizing trays. With this data in hand, the diameter and quantity of pre-desolventizing trays can be selected. Major manufacturers of DTs utilize process simulation tools to assist processors in optimizing the DT configuration for a given application (Kemper, 2011). 2.4.4. Flash desolventization and cooling Desolventisation of oilseed meals is also undertaken in such a manner that their proteins retain their solubility and other functional properties, and other heat sensitive constituents are not rendered inactive. Research has demonstrated that dry heating/desolventisation has a reduced effect on protein denaturation, thereby preserving the solubility of the protein (Figure 2.11). An approach to such desolventisation is to quickly flash off the solvent to minimize time at higher temperatures. This is accomplished in a pneumatic conveying desolventizer using super-heated solvent vapors, with residence time limited to a few seconds (Figure 2.12A). Once most of the solvent is gone, the product is no longer thermally protected by the solvent. To prevent denaturation a further step operating under vacuum is necessary for final desolventisation of the meal. This is referred to as the flash desolventizing and cooling process. In this process, the de-oiled oilseed material is fed into a high-velocity stream of solvent vapours superheated to approximately 150°C. The material enters the tube at approximately 55-60°C with 25-35% solvent and 8 to 10% moisture. The superheated solvent vapours convey the material in a loop-shaped tube at approximately 20 m/sec velocity. Specific heat in the superheated solvent vapour stream is given up to provide the latent heat for the solvent and some moisture in the material stream to evaporate. The turbulent superheated vapour flow elevates the temperature of the flakes to 77-88oC (well above 69oC, the boiling point of hexane), in less than 3 seconds. Approximately 3 seconds after entering the tube, the de-oiled oilseed material exits the tube at approximately 100-105°C with 1-2% liquid solvent and 6 to 8% moisture remaining (Kemper, 2011). The flakes enter the flash desolventizer at low moisture for a very short period and no steam is injected into the vapour stream, thus, little denaturation of the protein occurs. The greater proportion of the hexane is removed as the flakes travel through the tube to the cyclone separator. The substantially desolventized product is separated from the vapours in a high efficiency cyclone separator, and then fed to a vacuum stripper (Johnson, 2002; Kemper, 2011). 2.4.5. Vacuum stripping Its solvent level of 1-2% is too high to safely handle this flash desolventized material. Therefore, it is further conveyed into a flake stripper vessel and contacted with superheated steam to strip out the remaining solvent down to less than 2000 ppm remaining. In more recent installations, the flake stripper vessel is maintained under approximately 0.5 barg vacuum to help reduce residual solvent down to less than 500 ppm remaining. The flake stripper vessel may be a vertical tray type vessel (Figure 2.12B), a horizontal conveyor type vessel, or a horizontal paddle mixer type vessel. To maintain the PDI (Protein Dispersibility Index) of the meal as high as possible, none of the superheated steam should condense. Therefore, it is critical that this flake stripper vessel is traced with hot water and is very well insulated. For protein isolates and specialty flour applications, the desired PDI is as high as The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 33 possible (85-90 PDI). In these cases, heated surfaces in the flake stripper are maintained at 90-100°C. For protein concentrate applications, the desired PDI is usually around 70. In this case moisture is sprayed into the flake stripper and/or the heated surfaces are operated at higher temperature (Kemper, 2011). The temperature of the flash desolventized material exiting the flake stripper is typically 90-100°C. This temperature is reduced to within 10-20°C ambient, by passing air through the material in a dilute-phase pneumatic transport system in small-capacity plants, and in a DC (see above) in large-capacity plants. The cooled product is commonly referred to as white flakes (Kemper, 2011). The product is conveyed at high velocity, so a higher degree of flake breakage occurs than in the The Down Draft Desolventizer (DDD) (Figure 2.12 C). For white flakes going into specialty soy flour applications, the air used in the cooling process must be filtered through a biological filter to remove any bacteria. For white flakes going into a protein concentrates or protein isolates process, this is not critical as any bacteria will be eliminated downstream. For protein concentrates applications, the integrity of the flake shape is important and fine material needs to be screened away. For specialty flour applications and protein isolates applications, maintaining the shape of the flash desolventized material is not important, as size reduction is a normal process step downstream. The superheated solvent stream drops in temperature to approximately 110°C after the material is discharged and then proceeds to a blower to restore the velocity and a heater to re- warm the superheated solvent vapours to 150°C before the tube approaches the material inlet point of the loop. Excess solvent and water vapours created in the tube leave through an automated pressure control valve to a condenser (Kemper, 2011). Figure 2.11. Dry heating/desolventizing (Crown Iron Works Company www.crownton.com) The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 34 2.4.6. The vapour desolventizer As in flash desolventisation, superheated hexane also furnishes the required heat energy in vapour desolventizing. Flakes are contacted with the hot hexane vapour in a horizontal drum equipped with an agitator/ conveyor (Johnson, 2002). Figure 2.12A. The flash desolventizer Figure 2.12B. The vacuum stripper/cooler Figure 2.12C. The Down Draft Desolventizer Figure 2.12 A: The Flash Desolventizer, B: The Vacuum Stripper/Cooler and C: The Down Draft Desolventizer (Crown Iron Works Company, www.crownton.com ) 2.4.7. The Crown Iron Works’ Down Draft Desolventizer (DDD) The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 35 The Crown Iron Works’ Down Draft Desolventizer (Figure 2.12C) is an indirect contact dryer that gently moves the product over a series of heated trays to maintain flake integrity during desolventisation. The process is ideal for temperature-sensitive products where strict control of residence time is required. The flakes are turned over every few minutes to prevent overheating and the gentle motion minimizes the breakage of soft or irregularly shaped products. The DDD is also ideal for larger particles that require extended residence time for drying. The solvent vapors are scrubbed to remove the fines and then sent to the standard First Stage Evaporator for heat recovery. Larger flakes are often preferred for manufacturing protein concentrates. The gentle conveying motion of the mechanical conveyor uses minimal horsepower to move the solids. Utilizing the concepts of shallow bed depths and multiple bed turnovers, the DDD is compact in design and offers an indirect heating system for desolventizing flakes meant for high PDI or NSI (Nitrogen Solubility Index) meal. Advantages listed by the manufacturer are as follows (Crown Iron Works Company www.crownton.com): i. Gentle handling throughout the process produces a final product with a maximum content of whole flakes, and a minimum of fines. ii. Low capital investment. iii. Lower installation costs. iv. Low installed horsepower, less than 20 hp for a 100-ton-per-day system v. Plug flow minimizes variation in residence time. vi. Higher attainable PDI than with conventional systems vii. Minimizes breakage of material where size and shape are required to be maintained. 2.5. Extraction of Palm (Elaeis guineensis) Mesocarp Oil, Palm Kernels, and Palm Kernel Oil 2.5.1. Oil yield Oil palm fruits (Figure 2.13) contain two distinct types of oil: red palm oil which is extracted from the fleshy fruit layer (or mesocarp), and pale-yellow palm kernel oil, which is extracted from the kernel. Palm oil and palm kernel oil have very different chemical and physical properties and they are described separately in this section. The fruit pulp contains 40 - 62% oil, and palm kernels contain 46 - 48% oil, which is chemically similar to coconut oil. Yields are more than 6 tonnes/ha, making the oil palm (Elaeis guineensis) the highest-yielding oil plant. Typically, for tenera fruit, 100 kg of fresh fruit yields 21 kg of red palm oil and 6 kg of palm kernel oil. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 36 Figure 2.13. Oil palm fresh fruit bunch. Fruits: tenera (t), dura (d), pisifera (p) (Fellows and Axtell, 2012). The extraction of palm oil (Fig. 2.14) is carried out soon after harvesting the fruit bunches, with as little delay as possible in order to prevent deterioration of the oil. For the extraction of palm oil from palm fruits, the fruit bunches are first subjected to pre- processing which consists of two steps, bunch sterilisation, and bunch stripping and digestion. 2.5.2. Bunch sterilisation Sterilisation of fresh fruit bunches is carried out to obtain the following: i. Inactivate fruit enzymes. ii. Loosen fruits from the bunch. iii. Soften fruits in readiness for digestion. iv. Coagulate mesocarp protein. v. Hydrolyse and decompose mucilaginous material. vi. Partly dehydrate nut and shrink kernel in preparation for cracking. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 37 Figure 2.14. Steps in the processing of oil palm (Elaeis guineensis) fruits (Johnson, 2002) 2.5.3. Bunch stripping and fruit digestion The sterilised fruit bunches are stripped to remove the fruits, which are then digested, i.e., processed to ensure the efficient extraction of oil at the press and also efficient separation of fibre and nuts after pressing. This is achieved by mechanical stirring of the fruits in order to detach the mesocarp from the endocarp (nut). This operation is carried out in a digester. The digested mass is pressed in a hydraulic or screw press. In modern mills, pressing is done using a continuous screw press. Crude oil from the press is screened to remove the larger solid particles and then clarified. 2.5.4. Clarification The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 38 The clarification process is undertaken to separate the oil from water, solid fruit particles and dirt. The first stage of the process involves a simple decantation of oil from the water phase (sludge). Hot water is added to the sludge in order to recover more oil and the decanted oil is screened. In larger mills complete separation of oil from sludge is carried out by centrifugation. Finally, the oil is vacuum-dried. 2.5.5. Separation of nuts from palm press fibre The pressed digested mass is processed to separate the nuts from fibre. In small mills this is achieved by drying and manual separation or mechanically by the use of a motorised device. This device, the separator, has the advantage of being able to separate nuts from wet fibre. The separated fibre can then be pressed to give more oil. In modern mills, separation is pneumatic, the fibre being carried away in a current of air. 2.5.6. Extraction of kernels from nuts In small mills, nuts are sundried and cracked using a modified hammer mill, which breaks the shell but leaves the kernel intact. In larger mills, artificial drying of the nuts is followed by hauling them against a cracking ring in a centrifugal device. In smaller mills, separation of shell from kernel is done manually (i.e., picking by hand) and /or by density differential in a water-clay suspension. Larger facilities employ density differential separation in centrifugal devices known as hydrocylones. 2.5.7. Extraction of palm kernel oil (see section 2.2. above). 2.6. Recovery of Animal Fats Animal fats are a by-product of the livestock and meat processing industry. Since the non- edible part of the meat must be disposed of, there will always be a rendering industry making available, animal fat for edible, inedible, and oleochemical applications. The volume of inedible animal fat raw material is relatively inflexible, being linked inextricably with the production and consumption of edible products. This places a limitation on its end use competitiveness with vegetable and marine sources, where supplies can be developed in line with, and are sensitive to demand. This situation is further compounded by the fact that in the animal by-product economy, the recovery of fats may not be the principal source of process revenue. Revenue from proteins, minerals and other products must therefore be given due consideration (Tables 2.2 and 2.3). The principal inedible fat of animal origin is beef tallow. This account will therefore focus on this material. 2.6.1. Raw material sources The division of a steer with a live-weight of about 420 kg is shown in Table 2.2, which also gives corresponding values for sheep and lambs. Value for sheep and lambs vary for different breeds and live weights. Table 2.2. Breakdown of slaughtered steer, sheep, and lamb (Anon, 1985) Parts Steer Sheep Lamb Carcass and other 62-64 61-63 62-64 edible products (%) The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 39 Edible raw fat (%) 3-4 4-5 5-6 Blood (%) 3-4 4-4.5 3.5-6 Inedible raw material 8-10 7-8 6-7 (%) Shrinkage (%) 2-10 1-1.5 0.5-1 Stomach and - 9.5 5.5 intestines (%) Paunch and manure 8 - - Pelt and wool (%) - 11 15 Hide (%) 7 - - The general sources of raw materials are: i. Dead stock: Fallen animals, due to age, disease, accident, weather, exposure etc. ii. Slaughter by-product: These include viscera, trimmings, heads, feet, catch basin skimming, and condemned carcasses. Inedible offal can account for 8-10% of the live weight of a steer. iii. Wholesale cutting and boning: These include the trimmings from bones, trimming from operations producing canned and boneless products, prime cuts, or special products for hotel, restaurant and retail trade. iv. Retail markets: This includes fat and bone scrap trimmings from retail store operations. v. Hotel and restaurant scrap: This comprises the scrap, both raw and cooked, from the operation of pubic restaurants. The source, quality, conditions and nature of the raw materials vary widely. Quality is only ensured through the careful selection and prompt and controlled handling of materials throughout processing. Uniformity is maintained either by specialising in only one raw material or by conducting a well-planned and balanced broad operation utilising all the sources mentioned above (Rose, 1954). Larger scale rendering operations would have advantages over small scale operations due to economies of scale arising from product uniformity and quality control, the ability to benefit from raw materials supply, material selection and segregation, and proper process handling. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 40 Table 2.3. Utilisation of animal by-products (Anon, 1985) By-Product Processed By-Product Use Inedible raw material, mixed, Meat and bone meal Livestock and poultry feed condemned material and whole Inedible fat See below condemned animals. Inedible raw fat. Inedible fat Lubricants, soap, candles, glycerine, adhesives for feeds Inedible raw blood Blood meal Livestock and poultry feeds, Blood albumen fertilisers. Leather preparation. Mordant. Edible raw blood Plasma and red corpuscles Adhesives for sausages, etc. Medical purposes. Fortified red wine, sausages and black pudding. Edible raw fat Edible fat Frying purposes Oleo oil Shortening. Oleo stearin Candy, chewing-gum Cracklings Pet foods or meat meal Raw bone classified as edible Edible fat Shortening Bone pieces Bone gelatine Bone meal Raw bone classified as inedible Inedible fat See above Bone pieces Bone glue Bone meal Cattle feet Neatsfoot oil Fine lubricants Glues, gelatine, meal. Pig skin Tanned skin Leather products Gelatine Jellied food products Glands, stomachs Pharmaceutical Medicine Intestines Sausage casing Sausage skins Livers, hearts, kidneys Edible products Direct consumption or in sausages Horns and hoofs Extracted protein Foaming fire extinguishers 2.6.2. Rendering Product Specifications The products of animal fat rendering, in addition to fat, include proteins, minerals and other products. Of advantage to the processor is the fact that generally, those process principles that produce high yield and quality of fat products also seem to produce the highest value in protein and mineral products (Rose, 1954). Generally, for the fat, protein, and mineral products, the characteristics desired are as follows (Table 2.4): The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 41 Table 2.4. Desirable rendering edible products (Rose, 1954) Product Fat Protein Minerals Yield Maximum Maximum Maximum Contamination by other None Permissible but desired Desired low, no market components of the raw low as they have no value material. market value Chief chemical Triacylglycerols Animal protein Animal phosphates component upon which value is based Secondary components Free fatty acids, non-fats Minerals, vitamins. Biological value over influencing value mineral phosphates Colour Light Light White Odour Good Good Neutral or bland Texture Uniform Uniform Uniform Composition Uniform Uniform Uniform Biological value High High High Palatability High High High Storage stability High High High 2.6.3. Basic principles affecting rendering quality As is the case with other oleaginous materials, five basic factors serve to guide any good fat recovery operation and the selection of a process for it (see section 2.1.). These are as follows: i. Time ii. Temperature iii. Bacteria iv. Enzymes v. Moisture. These factors militate against any attempt to produce top quality animal fat. An adequate fat recovery method must adequately control all five. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 42 2.6.4. Fat recovery processes Fat recovery from oil bearing material of animal origin follows a series of basic operations common to all fat recovery processes. These include: i. Preparation of material. ii. Cooking (and dehydration in some processes, e.g., in edible fat dry rendering). iii. Separation of fat from solid residue. iv. Processing of fat to finished product. v. Processing of residue to a feed product. The various fat recovery processes are as follows: 2.6.5. Inedible raw materials Inedible offal can represent 8-10% of the liveweight of a steer; also condemned meat, carcases and “fallen” animals can be processed due to the high sterilisation temperature achieved. 2.6.5.1. Rendering process for inedible fat Inedible rendering consists mainly of the separation of three main constituents: i. Fat ii. Water iii. Fat-free dry substances. Although a number of different methods are available for rendering inedible raw materials, in all cases, the materials are cooked (during this operation, the materials are also sterilised) and then separated, purified and processed into the commercially required forms. Rendering processes for inedible tallow are as follows: 2.6.5.2. Conventional batch rendering (CBR) In this process, the material is heated indirectly by steam in a cooker fitted with a strainer in the bottom. The solids are then defatted further by means of a pusher or basket centrifuge, or a screw press. If necessary, further defatting can be achieved by solvent extraction. The separated fat is then clarified, usually by means of a high-speed centrifugal separator. A disadvantage of this system is the long cooking time (over 2.5 hr), which could result in burning and discolouration. Also, since the type of processing is not usually a completely closed system, oxidation and rancidity are more likely to occur (Anon, 1985). 2.6.5.3. The continuous method This is a variation of the CBR, which involves the continuous flow of material in and out of the cooker. The advantage of this is that although the process is carried out at atmospheric pressure, cooking time is considerably reduced. A drawback of the method however, is that sterilisation temperature is not reached (Anon, 1985). 2.6.5.4. The semi-continuous method The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 43 This is essentially a wet rendering process. Crushed material is charged to one of two pressure cookers, re-cycle water is added and heating is carried out for 55 min. The relatively high-water content eliminates the likelihood of burning and discolouration. From the alternate cookers the material is discharged into a buffer tank; from then onwards the process is operated on a continuous basis. From the buffer tank the material is fed to a decanter centrifuge where the bulk of the solids are separated and discharged to a continuous dryer. After drying the material is ground to produce a low fat, high protein meal. The liquid from the decanter centrifuge, which contains fat, water and fines, is fed to a high- speed centrifuge, which separates the three streams. Process water is recycled; fat is discharged either as final product or to a second (polishing) separator. Fines are added to material entering the dryer. Compared with conventional batch rendering, the semi-continuous process increases digestibility of raw protein, and available lysine is increased. This method yields a meal of fat content as low as 6% w/w, and a raw protein digestibility of up to 90% (Anon, 1985). 2.6.6. Edible fat rendering Raw material for the production of edible fat must be fit for human consumption, and have a fat content of 65-90%, the remainder being made up of proteinaceous dry solids and water. As a rule, fats of low free fatty acid (FFA) content are of higher quality and stability to oxidative and hydrolytic deterioration. Therefore, processing conditions must be such as would not result in increase in FFA. Sterilisation is not necessary as the raw material has been passed as fit for human consumption (Anon, 1985). There are three main methods for the extraction of edible fat. These are: i. The wet rendering system which uses pressure cookers ii. Dry rendering involving the use of atmospheric batch cookers iii. The continuous low temperature rendering system in which heating, separation and cooling are all carried out on a continuous basis. 2.6.6.1. Wet batch rendering In the wet batch system, the cooker is filled with pre-cut raw material and live steam is injected raising the temperature to 140oC at the corresponding pressure. The heat treatment is maintained for three to four hours, after which the pressure is slowly released and the fat run into a receiver. The fat is purified further by settling out the water and fines either by gravity or by centrifugal force. The proteinaceous solids are discharged from the cooker for pre-pressing prior to further fat removal by solvent extraction and drying. The wet rendering process is used for the production of edible fats. Its drawback is that while producing a fat of good quality, it is only capable of producing a protein of comparable quality at relatively high cost and low efficiency (Anon, 1985). 2.6.6.2. Dry rendering This process employs a basic dehydration step with several modifications of auxiliary equipment required to remove the fat retained in the dehydrated product after draining the free run tallow. Heating is carried out indirectly with steam; water is driven off for a period of 1.5 to 2 h at atmospheric pressure. The fat is then separated from the greaves in the same manner The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 44 as wet rendering. The residual fat is removed by the use of a hydraulic press or an expeller, by solvent extraction, or by centrifugation, after adequate pretreatment. (Rose, 1954) 2.6.6.3. Continuous low temperature rendering In this process, heating, separation and cooling are all carried out on a continuous basis. 2.7. Marine Oils 2.7.1. Raw materials Practically all marine fish species as well as most other marine animal life may, in principle, be converted into fish oil and meal. The type of products known as non-food products are mainly fish meal and fish oil; included also are different types of ornamental fish, fish waste, dead fish, seaweeds and algae unfit for human consumption, as well as frozen fish roes. Table 2.5. World Fisheries and Aquaculture Production, Utilisation and Trade (FAO, 2020) a Category 1986-1995* 1996-2005* 2006-2015* 2016 2017 2018* Production 6.4 8.3 10.6 11.4 11.9 12.0 (million tonnes, live wt.) Capture Inland Marine 80.5 83.0 79.3 78.3 81.2 84.4 Total capture 86.9 91.4 89.8 89.6 93.1 96.4 Aquaculture Inland 8.6 19.8 36.8 48.0 49.6 51.3 Marine 6.3 14.4 22.8 28.5 30.0 30.8 Total 14.9 34.2 57.7 76.5 79.5 82.1 aquaculture Total world 101.8 125.6 149.5 166.1 172.7 178.5 fisheries and aquaculture Utilisationb 71.8 98.5 129.2 148.2 152.9 156.4 Human consumptionc Non-food uses 29.9 27.7 20.3 17.9 19.7 22.2 Population 5.4 6.2 7.0 7.5 7.5 7.6 (billions)d Per capita 13.4 15.9 18.4 19.9 20.3 20.5 apparent consumption (kg) * Average per year from, for example, 1986-1995. a Excludes aquatic mammals, crocodiles, alligators, and caimers, seaweeds and other aquatic plants. Total may not match due to rounding. The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 45 b Utilisation data for 2014-2018 are provisional estimates. c The term “food fish” refers to fish destined for human consumption, thus excluding fish for non-food uses. The term consumption refers to apparent consumption, which is the average food available for consumption, which, for a number of reasons (for example, waste at the household level) is not equal to food intake. d Source of population figures: UN Department of Economic and Social Affairs (DESA), 2019. Global fish production is estimated to have reached about 179 million tonnes in 2018 (Tables 2.5 and 2.6), with a total first sale value estimated at USD 401 billion, of which 82 million tonnes, valued at USD 250 billion came from aquaculture production. Of the overall total, 156 million tonnes were used for human consumption, equivalent to an estimated annual supply of 20.5 kg per capita, The remaining 22 million tonnes were destined for non-food uses, mainly to produce fish oil and fishmeal (about 15 million tonnes), with the balance largely used for ornamental purposes, fingerlings, bait, pharmaceuticals, and as raw material for direct feeding in aquaculture (Anon, 2018; FAO, 2020). Table 2.6. Marine Capture Production: Major Species and Genera (FAO, 2020) 2004-2013 2015 2016 2017 2018 2018 share (% (average per of total) year) (Thousand tonnes, live wt) Finfish Anchoveta, 7,276 4310 3192 3923 7045 10 Engraulis ringens Alaska pollock, 2897 3373 3476 3489 3397 5 Gadus chalcogrammus Skipjack tuna, 2494 2822 2862 2785 3161 4 Katsuwonus pelamis Atlantic 2162 1512 1640 1816 1820 3 herring, Clupea harengus Blue whiting, 1182 1414 1190 1559 1712 2 Micromestistious poutassou European 1084 1176 1279 1437 1608 2 pilchard, Sardina pilchardus Pacific club 1483 1457 1565 1513 1557 2 mackerel, Scomber japonicus Yellowfin tuna, 1239 1377 1479 1513 1458 2 tunnus albacares Scads nei, 1199 1041 1046 1186 1336 2 Decapterus spp. Atlantic cod, 948 1304 1329 1308 1218 2 The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 46 Gadus morhua Largehead 1326 1272 1234 1221 1151 2 hairtail, Trachiurus lepturus Atlantic 751 1247 1141 1218 1047 1 mackerel, Scomber scombrus Japanese 1347 1336 1128 1060 957 1 anchovy, Engraulis japonicus Sardinellas 899 1057 1106 1138 887 1 nei*, Sardinella spp. Others 41187 41936 42343 43444 43572 61 Finfish total 67474 66634 66012 68613 71926 100 Crustaceans Natantian 784 825 879 975 850 14 decapods nei, Natantia Gazami crab, 383 561 523 513 493 8 Portunus trituberculatus Akiami paste 585 544 486 453 439 7 shrimp, Acetes japonicus Antarctic krill, 156 251 274 252 322 5 Euphausia superba Marine crab 265 360 343 343 314 5 nei, Brachyura Blue swimming 175 237 259 302 298 5 crab, Portunus pelagicus Argentine red 57 144 179 244 256 4 shrimp, Pleoticus muelleri Southern rough 314 368 314 268 248 4 shrimp, Trachypenaeus curvirostris Others 2, 735 2, 819 2, 722 2, 659 2, 776 46 Crustaceans 5, 454 6, 109 5, 979 6, 027 5, 997 100 total Molluscs Jumbo flying 823 1004 747 763 892 15 squid, Dosidicus gigas Marine 802 759 674 648 664 11 The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 47 molluscs nei, Mollusca Various squids 641 693 629 655 570 10 nei, Loliginidae, Ommastrephidae Common squids 248 358 319 311 369 6 nei, Loligo spp. Cuttlefish, 301 405 379 395 348 6 bobtail squids nei, Sepiidae, Sepiolidae Cephalopods 382 388 394 433 322 5 nei, Cephalopoda Yesso scallop, 309 243 224 247 316 5 Patinopecten yessoensis Others 3110 3279 2361 2560 2478 42 Molluscs total 6, 616 7, 129 5, 728 6, 012 5, 959 100 Other animals Jellyfishes nei, 312 355 293 263 264 50 Rhopilema spp. Aquatic 25 121 119 120 116 22 invertebrates nei, Invertibrata Sea cucumbers 22 31 34 38 48 9 nei, Holothuroidea Chilean sea 38 32 30 31 32 6 urchin, Loxechinus albus Cannonball 6 42 25 27 16 3 jellyfish, Stomolophus meleagris Sea urchins nei, 34 33 28 30 25 5 Strongylocentr otus spp. Others 22 22 25 27 16 3 Other animals 459 636 554 556 531 100 total Total all 80, 002 80, 507 78, 272 81, 208 84, 412 species *Nei: not enough information Ocean fish can be divided into two groups, pelagic and demersal, depending on the specific ocean depth where they are found. The pelagic fish are usually found in the middle, and at the surface layers of the ocean. Pelagic fish include many of the fatty fish, such as herring, The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 48 mackerel, salmon, tuna, sardines and anchovies. Some of these fish reach 20% total muscle fat. The demersal fish are usually found at or near the bottom of the sea on the continental shelves. They include cod, haddock, whiting, ocean perch, and flat fish such as flounder and halibut. These fish usually have less than 5% oil in the muscle (Potter, 1950; Watt, 1950) (Table 2.7). Table 2.7. Lipid content of common varieties of fish (Watt. 1950) Fish Lipid content Fish Lipid content (% wet wt) (% wet wt) Alewives (river herring) 4.9 Salmon (chum, keta) 5.2 Blue fish 4.0 Salmon (coho, silver) 8.4 Cod (tomcod and lingcod) 0.4 Salmon (pink, humpback) 6.2 Flounder (fluke sole) 0.6 Salmon (sockeye, red, blue 9.6 back) Haddock 0.3 Salmon (Atlantic) 13.4 Halibut 5.2 Sardines 11.0 Herring (Atlantic) 12.0 Tuna (blue fin, yellow fin) 11.4 Mackerel (Atlantic) 12.0 Trout (brook) 2.1 Pilchards 8.6 Pollack 0.8 Whiting 1.0 Rosefish 0.8 Salmon (Chinook, King) 16.5 The actual composition of edible fish muscle will vary according to the maturity of the fish, the availability of its food, and the season of the year. The various types and average composition of most fish is given in Table 2.8 as follows (FAO, 1986): Gadoids These are the cod-like fishes. They consist of a number of fish species which are classified as lean. A characteristic of this group is the location of most of their fat in the liver. Fishmeal made from these species of fish is called white fishmeal. Clupeids The clupeids consist of the herrings; these provide the largest single source of raw material for production of fish meal and oil. They may be classified as fatty although the fat content may vary from 2% to 30%, depending on species and season. The fat is not, as in lean fish, concentrated in the liver, but is generally distributed throughout the body. Scombroids This consists of the fatty fish species the mackerels. Elasmobranchs The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 49 The sharks and the rays belong to this group. They are not specially caught for meal and oil production, although some species provide raw material as trash fish and as offal from processing. Salmonids The salmons and other closely related fish are generally not harvested for fishmeal production, but offal from salmon is used. However, one species, the capelin, has become a considerable source of material for meal and oil. Crustaceans The carapaces and shells of members of this group, as well as small crustaceans that are unmarketable for direct human consumption are used for meal and oil production. Table 2.8. Composition of whole fish (FAO, 1986)* The Chemistry and Technology of Food Fats and Oils. Their Extraction, Composition, Modification and Utilisation. Copyright © 2022 by Fred O.J. Oboh. All rights reserved. Amazon Kindle Paperback. ISBN: 9798361143030. 185pp.  F.O.J. Oboh. Industrial production of fats and oils 50 Fish species Protein Fat Ash Water Gadoids Blue whiting. North 17.0 5.0 4.0 75.0 Sea Sprat. Atlantic 16.0 11.0 2.0 71.0 Hake. South Africa 17.0 2.0 3.0 79.0 Norway pout 16.0 5.5 3.0 73.0 Clupeids Anchoveta 18.0 6.0 2.5 78.0 Herring. spring 18.0 8.0 2.0 72.0 Herring. winter 18.2 11.0 2.0 70.0 Pilchard. South 18.0 9.0 3.0 69.0 Africa Anchovy. South 17.0 10.0 3.0 70.0 Africa Scombroids Mackerel, spring, 18.0 5.5 1.6 75.0 North