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Fermentation and milk review fermentation • Cellular respiration is aerobic (requires oxygen) to convert glucose to carbon dioxide and water, to produce energy • Fermentation is anaerobic (no oxygen) releases carbon dioxide to produce energy. Depending on the organism, the other biproduct might be ethyl alcohol (yeast), lactic acid (some bacteria) or acetic acid (different bacteria) Why ferment? • Preservative • Easier to eat • Flavor pasteurization • The process that uses heat to kill bacteria. In milk, this makes it safe to drink, with a longer shelf life. • For fermented products, this kills the undesirable micro-organisms that will spoil the fermented foods • The organism that is used for fermentation is then added. Bacterial fermentation • Bacteria used for fermentation are indigenous, or the culture is added • Lactic acid- produce lactic acid, used to produce yogurt, sour cream, cheese, dill pickles, sauerkraut • Acetic acid- used to make vinegar • Carbon dioxide- Gouda, Edam, and Swiss cheese Pickling • Brine pickling- a high salt solution several weeks until pH is lowered • Fresh-pack pickling- placed in brine for a few hours, then drained and placed in boiling vinegar and spices Sauerkraut • Bacteria is on the cabbage, when washed and chopped this increases the fermenting bacteria, stored at 21 OC • Salt- releases fluid to promote bacterial growth, inhibits growth of undesirable bacteria • pH is lowered during fermentation yeast • Fermentation produces ethyl alcohol • Best temperature 27 OC – temperatures too high will kill the yeast • While sugar is needed, too much sugar will slow fermentation • Salt- too much inhibits carbon dioxide production, too little weakens gluten beverages • • • • • Use yeast Pasteurization Inoculation Incubation The flavor depends upon what is fermented and the period of incubation Coffee and tea • Coffee – cherries are either fermented wet or dry – The fleshy part is removed – Then beans are roasted • Tea – The leaves are rolled to encourage fermentation, weaken the cell walls – Then dried Fermented products • • • • • Cheese Pickles Sausage Beverages Tempeh chocolate • Brain pop milk • A solution, a colloid, and emulsion – A solution • Vitamins and minerals • Carbohydrates – A colloid • Proteins – An emulsion • Fats Milk proteins: colloid • • • • 80% is casein micelles Stable at normal pH Coagulate (clump) at pH of 4.6 forming curds Precipitate when heated (the bottom or float to the top forming skin) • Whey- the solution left (and the 20% proteins) after casein coagulates • Responsible for the Tyndall effect and why milk is white • Enzymes-most are denatured during pasteurization emulsion • Fat globules surrounded by a membrane of phospholipids and proteins • 400 different fatty acids, but little cholesterol • Creaming: When fats rise to the top of fresh milk carbohydrates • Lactose: milk sugar- reacts with proteins when heated gives flavor and color • Lactose intolerance- when person does not have lactase (the enzyme that breaks down lactose) – Results in gas, bloating, pain, Vitamins and minerals • Minerals- as salts – Helps prevent milk from curdling – Calcium and magnesium keeps casein micelles stable – The enzyme Rennin- used in cheese making coagulates more when fewer salts are present • Vitamins- four main ones – – – – Riboflavin- light sensitive Thiamin Niacin Vitamin A- fat soluble processing • • • • • To increase shelf life Pasteurization Homogenization Fortification – vitamin D Restoration Vitamin A in low fat products Milk products • • • • • UHT- ultra High temperature Evaporated (uses carrageenan to stabilize) Sweetened condensed Dry milk Fermented milk products – – – – Buttermilk (uses acid to coagulate casein) Yogurt Sour cream Cheeses
