Fermentation and milk

1. Fermentation and milk review

2. 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 bi-product might be ethyl alcohol (yeast), lactic acid (some bacteria) or acetic acid (different bacteria)

3. Why ferment? • Preservative • Easier to eat • Flavor

4. 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.

5. 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

6. 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

7. 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

8. 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

9. beverages • Use yeast • Pasteurization • Inoculation • Incubation • The flavor depends upon what is fermented and the period of incubation

10. 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

11. Fermented products • Cheese • Pickles • Sausage • Beverages • Tempeh

12. chocolate • Brain pop

13. milk • A solution, a colloid, and emulsion • A solution • Vitamins and minerals • Carbohydrates • A colloid • Proteins • An emulsion • Fats

14. 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

15. 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

16. 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,

17. 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

18. processing • To increase shelf life • Pasteurization • Homogenization • Fortification – vitamin D • Restoration Vitamin A in low fat products

19. 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