Different types of Fermented products, Lecture notes of Food Science and Technology

Download Different types of Fermented products and more Lecture notes Food Science and Technology in PDF only on Docsity! Fermented Products Miss Kulsoom Ibrahim Learning Objectives: The students might be able to know about: ● Fermented products ● and its manufacturing process ❏ These properties enable the dough to stretch and retain sufficient amounts of gas to produce loaves with good volume and a fine, soft open structure. ❏ The gas is a combination of air incorporated during mixing and kneading and CO2 produced from the fermentation of sugars by yeasts. ❏ The yeasts used are normally strains of Saccharomyces cerevisiae,commonly known as baker’s yeast. ❏ The metabolic activity of the yeasts helps to chemically ripen the gluten, enabling the dough to expand evenly and retain the gases during baking. The yeasts contribute to the flavor and provide an appealing aroma. Wine Steps of wine making Wine can be produced from any fruit juice with sufficient levels of fermentable sugars, in most cases wine is a beverage obtained by full or partial alcoholic fermentation of fresh, crushed grapes or grape juice (must), with an aging process. Wine making involves a series of steps. Yogurt ❏ Yogurt is a coagulated milk product obtained by lactic acid fermentation through the action of Streptococcus thermophilus and Lb. delbrueckii subsp. Bulgaricus. ❏ Yogurt is prepared using either whole or skim milk ❏ The concentrated milk is pasteurized at 82°C–93°C for 30–60 min and cooled to the starter incubation temperature of 40°C–45°C. ❏ Yogurt starter is then added at a level of around 2% by volume and incubated for 3–5 h, or until the titratable acidity of the final product reaches 0.85%–0.90% or a pH of 4.4–4.6 . ❏ The yogurt is then cooled to 5°C to inhibit further acid production. ❏ The symbiotic growth of the two organisms is better observed when they exist in a 1:1 ratio and these results in lactic acid production and acetaldehyde at a rate greater than that produced by either when growing alone. ❏ Streptococci produce lactic acid, formic acid, and carbon dioxide. Formic acid stimulates the growth of lactobacilli. The lactobacilli liberate some amino acids needed for the growth of the streptococci, and produce acetaldehyde and more lactic acid to bring the pH to 4.4–4.6. ❏ Acetaldehyde is the compound that contributes mostly to the typical flavor of yogurt, while diacetyl, and ethanol are produced in lower concentrations. Yogurt flavor continuously changes during manufacture and storage. ❏ Flavor changes may vary depending on the cultures, mix formulation, and incubation and storage conditions. Vinegars are produced from two- stage fermentation: ❏ initially an anaerobic, alcoholic fermentation of sugars by yeasts, ❏ And then by oxidation of the ethanol to acetic acid by bacteria. This second reaction is known as acetification. Acetification is also a common cause of spoilage of alcoholic beverages. Acetification can be described by the equation: C2 H5 OH+ O2 CH3 COOH+ H2 O Specific vinegar-making yeast strains, usually Saccharomyces cerevisiae are often used. In addition to ethanol, the fermentation also yields CO2, some higher acids, and small amounts of glycerol and acetic acid. In contrast to the alcoholic fermentation, acetification is a highly aerobic process, where bacteria oxidize ethanol to acetic acid. Small quantities of acetaldehyde, ethyl acetate, are produced during this reaction. Commercial acetic acid bacteria are members of the genera Acetobacter and Gluconobacter. These bacteria are strict aerobes that are often found naturally in association with yeasts on plants. Pic kles  Chemical pickling (brining): In chemical pickling, food is placed in an edible liquid that inhibits or kills bacteria and other micro-organisms. A number of pickling agents can be used like brine, vinegar, alcohol, and vegetable oil (olive or mustard oil). The chemical pickling process could also involve heating or boiling so that the food being preserved becomes saturated with the pickling agent. Common chemically pickled foods include cucumbers, peppers, corned beef, herring, and eggs, as well mixed vegetables such as chopped pickled vegetables and spices. Fermentation pickling: In fermented pickling, the food itself produces the preservation agent, typically by a process that produces lactic acid. Fermented pickles include sauerkraut, kimchi, and curtido (fermented cabbage, onions, carrots, oregano- Central American cuisine). Some chemically pickled cucumbers are also fermented. In commercial pickles, a preservative like sodium benzoate or EDTA may also be added to increase shelf life. References 1. C.S. Pederson. Microbiology of Food Fermentations, 2nd ed. Westport, CT:Avi Publishing Co., 1979. 2. H.A. Dirar. The Indigenous Fermented Foods of the Sudan. Wallingford, Oxon: CAB International 1994, p. 552. 3. K.H. Steinkraus. Lactic acid fermentation in the production of foods from vegetables, cereals and legumes.Antonie van Leeuwenhoek 49: 337–348, 1983. 4. Y. Motarjemi, M.J. Nout. Food fermentation: a safety and nutritional assessment. Joint FAO/WHO Workshop on Assessment of Fermentation as a Household Technology for Improving Food Safety. Bull. World Health Organisation 74(6): 553–559, 1996. 5. A.M. Hamstra. Consumer acceptance of food biotechnology. SWOKA Research Report 137, The Hague, The Netherlands, 1993. 6. L. Axelsson. Lactic acid bacteria: classification and physiology. In: Lactic Acid Bacteria: Microbiology and Functional Aspects, S. Salminen,A. von Wight, Eds., New York: Marcel Dekker, 1998, pp. 1–72. 7. A. Hurst, D.L. Collins-Thompson. Food as a bacterial habitat. In: Advances in Microbial Ecology,Vol. 3, M. Alexander, Ed., New York: Plenum Publishing Corporation, 1979, pp. 79–134. 8. D.M. Wheater,A. Hirsch,A.T.R. Mattick. Possible identity of “Lactobacillin” with hydrogen peroxide produced by Lactobacilli. Nature (Lond.) 170: 623–624, 1952.