Fermentation of Food Products PDF

Fermentation in Food Products Fermentation is the oldest method of food preservation. The principle of fermentation is the breakdown of CHO by bacteria and yeast to produce acids, alcohols, with some aldhydes, ketones and flavorings under anearobic conditions. Products produced by ferment...

Fermentation in Food Products Fermentation is the oldest method of food preservation. The principle of fermentation is the breakdown of CHO by bacteria and yeast to produce acids, alcohols, with some aldhydes, ketones and flavorings under anearobic conditions. Products produced by fermentation help preserves food against microbial degradation. A starter culture is a concentrated number of organisms desired to start the fermentation.  Fermentation Process Glycolysis: the oxidation of glucose to generate pyruvate & energy  Fermentation Process C6H12O6----Anaerobic---> 2CH3CH2OH + 2CO2 + energy glucose ethanol CH3CH2OH + O2 - ---------> CH3COOH + H2O + energy ethanol acetic acid  Benefits of fermentation 1. Preservation due to acid production. 2. Add flavors (soya). 3. Change chemical properties of the food as in sugar to ethanol, ethanol to acetic acid. 4. Fermented foods can be more nutritious than unfermented food. Fermentation microorganisms produce vitamins in food. 5. Fermentation can enzymatically split polymers like cellulose into simple sugars that are digestible by humans  How we can control the fermentation process? Fermentation can be controlled by: 1. pH: adding acid or formed during fermentation quickly to prevent undesirable spoilage. 2. Salt content: lactic acid bacteria used in pickles, olives..etc are more tolerant to salt (10-18%). Many of undesirable bacteria cannot tolerate salt (maximum 2.5%). Salt in solution is called “brine” 3. Temperature: depending on the temp. various microorganisms dominate fermentation. In Sauerkraut, 3 types of microorganisms are used and the action of each one depends on the temp. Uses of Fermentation  Vegetables Fermentations: -Starch and CHO in vegetables will be changed into lactic acid due to certain types of Lactic acid producing bacteria. This is done by the presence of bacteria present on the surface of the Vegetables. - Most of the lactobacilli are homo fermentative ( 1mole glucose give 2 mole lactic acid) bacteria and some of them are heterofermentative ( 1mole glucose give 1 mole lactic + 1 mole ethanol + 1 mole CO2) 1. Sauerkraut: 1.Sound heads of cabbage are prepared by washing and removing the outer leaves and any defective leaves. 2. The core is removed and the leaves are shredded. 3. About 2.25% salt is added uniformly to layers of shredded cabbage. 4. Sugar content in the brine is about 3-6% ( from cabbage), and the amount of sugar influences the fermentation and the final acidity. 5. Temperature of 18-22ºC are desirable for a good fermentation. Sequence of lactic bacterial fermentation – 1. Initially, Leuconostoc mesenteroides converts sugar in cabbage/brine to lactic acetic, alcohol, CO2 and organic flavor compounds. 2. Lactobacillus brevis and Pediococcus cerevisiae take over and produce acids. 3. Lactobacillus plantarum continues the fermentation process. Resulting acidity is not less than 1.5% (as lactic).  Brine salted vegetables 1- Similar to Sauerkraut method of fermentation 2- 15-20% salt concentration is preferred.( salt stock pickle method) 3- The salt concentration does not fall below 12% 4- The fermentation process relies on the rapid colonization of Lactic acid bacteria and the process takes 12 days at 30 C ( preserved by salt not lactic acid) 2. Cucumber pickles 1. Fresh cucumbers are packed with acetic acid (0.6%). Various spices are added to give the characteristic flavor. 2. Salt is added to reach 45-60 ºSalometer (11.25- 15.90% salt). 3. The microorganisms involved are the same lactic bacteria as in sauerkraut. 4. The final acidity of the product is about 0.6-1.2% (as lactic) which is formed in about 7-14 days. 3. Olives – (green and ripe) 1. Olives are brined and fermented in a manner similar to cucumbers. Before brining, the olives are soaked in a 1.25-2.0% lye solution to destroy bitter glucosides (oleuropein). 2.The organisms involved are the same lactic bacteria as in the sauerkraut. The final acidity is 0.18-1.27% (as lactic) and minimum is 0.6% for good flavor.  Advantages of vegetables fermentation 1- Extending the product shelf life ( preservation) 2- It makes the food easier to be digested. 3- The fact that the vegetables are not cooked which means it is more nutritious 4-Make the food safer to be consumed. 5- Add variety to table 4. Yogurt 1. To make yogurt, the milk is standardized to 10.5-11.5% solids, heated to about 90ºC for 30- 60 minutes, and then cooled to 40-45ºC. 2. The milk is then inoculated with a mixed culture of Streptococcus thermophilus and Lactobacillus bulgaricus (1.1). 3. The inoculated milk is incubated at 42ºC for 3- 6 hours, and cooled to 5-10ºC to stop fermentation. 4.The final acidity is 0.9-1.2% (as lactic), which is about pH 4.4. 5. Swiss cheese – (Emmental) Starter culture: Regular lactic culture plus Propionic acid bacteria (Propionibacterium sp.) and (Streptococcus thermophilus). 6. Blue-veined cheese Starter culture is regular lactic culture plus dried spores of the mold, Penicillium roqueforti. 7. Italian cheese There are several kinds of Italian cheeses on the market. The following are the major varieties. - Mozzarella – a soft, unripened cheese - Romano, Provolone, and Parmesan (Grana) are very hard cheeses. Starter cultures used are a regular lactic culture plus S. thermophilus and L bulgaricus 8. Latin American White cheese Queso Blanco is the most common variety in America and it is unripened, soft cheese. - For curd formation, natural microflora or organic acids (vinegar, lemon juice, or glacial acetic acid) are used in conjunction with rennet in some cases. 9. Vinegar – Vinegar is produced by an alcoholic fermentation followed by oxidation of the alcohol to acetic acid. Vinegar can be produced from any food product that can be fermented by yeast to ethanol. Bringing together the alcohol, air and Acetobacter.  10. Bread Making In breadmaking, fermentation involves two microrganisms: Yeast and bacteria Bread is leavened with yeast saccharomyces cerevisea to perform leavening function due to carbon dioxide production.  10. Bread Making Yeast also produce many other chemical substances that flavor the baked product and change the dough physical properties such as bread volume, develop structure and texture, imparts flavor to the bread, Enhance nutritive value  10. Bread Making  Bacteria: Roles of Lactic acid bacteria, mainly Leuconostoc mesenteroids 1- Produce Lactic acid 2- Produce Flavors compounds  10. Bread Making  During fermentation, dough conditioning Improving dough characteristics (quality)) take place ( yeast and water): Dough conditioning is due to the action on the gluten development due to proteolytic enzymes and low pH. (shorten kneading time and soften dough)= gluten degradation.  10. Bread Making Dough conditioners: - Ammonium salt (Ammonium sulfate, or [(NH4)2SO4], (as N source for yeast) to stimulate the yeast - Sugars to activate the yeast.  10. Bread Making In dough formation, it is very important Gas production is increased with increasing yeast activity, Adding sugars and amylase. Gas production is decreased by low amount of yeast, high and low temp. and salt addition. 11-Fermented Meat 27  1.Intr oduction Me at is the fle s h (mus cle tis s ue ) of war m- bloode d animals , but fe r me nte d s pe cialtie s fr om poultr y ( s aus age s as we ll as cur e d and s moke d fe r me nte d poultr y) ar e available. What is fe r me nte d s aus age ? A sausage is fermented if -its pH below 5.6 and D-lactic acid content above 0.2% -its color is heat-stable -its texture is no longer crumble -its aroma is typical -lactic acid bacteria predominate -Enterobacteriaceae counts are low 28 T able. 2 Clas s ification of fe r me nte d s aus age s 29  3. T he fe r me ntation pr oce s s Fe r me ntation pr oce s s : two type s - foods fr om a comminute d matr ix (cooke d or r aw me at pr oducts which have be e n pr e par e d by cut, s hr e dde d, gr ound, and mince d me at. - whole me at pr oducts. 30  A. Fe r me ntation of a Comminute d me at matrix a ) Variables in sausage production Variables include: The particle size of the comminuted meat and fatty tissue (1 and 30 mm) The selection of additives (curing salt, nitrate, ascorbic acid, sodium glutamate and glucono-∂-lactone -source glucose. The temperature /humidity (below 2to 3℃, the temperature is raised usually to ＞ 20℃ and ＞ 28℃, but maximum higher temperatures (32 to 38℃). The diameter of the sausages The nature of the casings smoking Heating after fermentation Dipping in antifungal preparations ( sorbic acid) pH-4.8 to 5.4 31 T able. 3 32 Spe cie s Employe d in Me at Starte r Culture s Bacteria: Lactic Acid Bacteria such as Lactobacillus acidophilus, Lb. plantarum etc, Lactococcus lactis, Pediococcus acidilactici, Lactobacillus paracasei Fungi: P. camemberti Yeasts: Debaryomyces hansenii 33 b) Saus age s as Pos s ible Pr obiotics contain the probiotic bacterial strain which effective in the intestines. probiotic bacteria supports survival and metabolic activity in the intestinal tract. probiotic food should have been performed to substantiate any health claim lactobacilli and bifidobacteria (probiotic strains) had been used for sausage production Lactobacillus paracasei are used for the production of moist type of fermented sausage 34 b) Sausages as Possible Probiotics large reduction of pH-∠5.0 extended ripening―＞ 1 month drying, or excessive heating in these condition all strains of bacteria damaged or killed. 35  B. Fe r me ntation of Whole Me at Pr oducts (HAM) curing by salting (with or without the use of nitrite and/or nitrate) to achieve a water activity of ∠0.96 (equivalent to 4.5% sodium chloride) temperatures (50C)―the salt will diffuse to the deepest part of meat overcoming the food poisoning through Clostridium botulinum contamination. after equilibrating the salt concentration and flavor development, the temperature is raised to 15 to 250C to ripen the ham. optimum flavor has no changed at least 6 to 9 months, maximum 18th month. at the end of ripening step, the moisture has been reduced by 25% and salt 4.5 to 6%) 36 1. Composition and changes during fermentation growth of LAB and concomitant (associated with) acidification of the product. reduction of nitrates to nitrites and formation of nitrosomyoglobin solubilization and gelification of miofibrillar and sarcoplasmic proteins degradation of proteins and lipids dehydration 37 2) Acidification, Dehydration, and Microbial Antagonism isoelectric point of meat proteins (pH 5.3 to 5.4) increase the ionic strength (from salt) sodium chloride and lactate in fermented sausages develop taste of the product. acidification and drying are importance for inhibition of the growth of pathogens. low pH and water activity exert an inhibitory effect towards pathogens. lactic and acetic acids are the major fermentation products the dry matter content 50-75% the water activity values.86-.92 depend on ripening 38 3) Proteolytic and Lipolytic Degradation during fermentation Peptides and amino acids accumulate to levels of about 1% dry matter Peptides and amino acids act as flavor enhancers and synergists. excess proteolysis may result in bitter and metabolic off-flavor amino acids and peptides are utilized by microorganisms for the conversion to flavor volatiles the bioactive peptides is influenced by lactic fermentation fat content 40-60% of dry matter long chain fatty acids are released from triglycerides and phospholipids free fatty acids are found 5% of the total fatty acids. polyunsaturated fatty acids is higher than saturated fatty acids. 39 4) Generation of Flavor volatiles Routes: by lipolysis and hydrolysis of phospholipids, followed by oxidation of free fatty acids. microorganisms produce organic acids: convert amino acids and peptides to flavor-active alcohols, aldehydes, and acids modify products of lipid oxidation (small aldehydes, substituted alkenals, ketones..etc) aroma is determined by the addition of spices, smoking, or surface- ripening with yeasts or molds. 40 T able. 4 Me chanis ms for ge ne r ation of flavor compounds 41 Product Dive rs ity and Se ns ory Prope r tie s The main desirable effects of starter micro-organisms on flavor and taste of fermented meats are formation of lactic acid breakdown of lipids degradation of peptides and amino acids formed by meat proteases Indirect effects are: consumption of oxygen reduction of nitrate protein degradation by mold proteases 42