Milk and Milk Products

1. Milk and Milk Products Chapter 23

2. Consumption Trends Using USDA food disappearance data Overall milk consumption has declined since 1970 Fat-reduced milk use has increased Record high levels of cheese

3. Nutritive Value 2005 Dietary Guidelines for Americans 3 cups of milk recommended daily Major source of Calcium Complete protein Vitamin D – when fortified Riboflavin Niacin value Other nutrients

4. Composition of Whole Milk 88 percent water 3.3 percent protein 3.3 percent fat 4.7 percent carbohydrate 0.7 percent ash (minerals)

5. Protein in Milk Casein 80 percent of milk protein A phosphoprotein Precipitates if Acidic Rennet added Whey Lactalbumin and lactoglobulin Coagulated by heat Byproduct of cheese making

6. Fat Milk is an emulsion Milk fat droplets are dispersed in the milk serum Fat in milk called Milk fat Butter fat Cream Milk fat is composed of Triglycerides – primary type Phospholipids Sterols – cholesterol

7. Carbohydrate Lactose A disaccharide If hydrolyzed produces Glucose Galactose Least soluble of common sugars Lactose intolerance Role of enzyme called lactase

8. Minerals and Vitamins Minerals Calcium, phosphorus, magnesium, and sodium Vitamins Fat soluble A, D, E, K Low-fat milk is fortified with Vitamin A Water soluble Milk is fortified with Vitamin D

9. Color White appearance because of Colloidally dispersed casein micelles Calcium phosphate salts Yellow pigments Carotenes Riboflavin Greenish-yellow fluorescent color in liquid whey Riboflavin

10. Flavor Slightly sweet (lactose) Heat processing Minimal impact on flavor Tends to disappear on storage Off-flavors From feed, bacteria, chemical changes, absorption of foreign flavors Light exposure

11. pH Fresh milk pH about 6.6 Acidity increases on standing with loss of carbon dioxide Acidity increases by action of lactic acid producing bacteria

12. Sanitation and Grading Grade A Pasteurized Milk Ordinance Grading Determined by sanitary codes

13. Bovine Somatotropin rBST Naturally occurring protein hormone Artificially synthesized via use of genetic engineering Increases milk production Approved by FDA Has been controversial

14. Pasteurization Required for Grade A fluid milk Milk sold in interstate commerce Involves heating of milk to destroy pathogenic bacteria Risks associated with raw milk

15. Homogenization Division of fat globules into small particles Prevents separation into a “cream” layer Because of increased dispersion of fat, homogenized milk Has richer flavor Increased viscosity Is whiter

16. Fortification Vitamin D Not naturally present in significant levels in milk Added to milk because of relationship between vitamin D, calcium, and phosphorus in body Vitamin A Fat reduced milk is fortified with vitamin A to replace vitamin A lost in with removal of cream

17. Types of Milk Fluid Milk Whole 3.25% milk fat Fat-reduced 2% 1% Non-fat Flavored milk

18. Types of Milk Concentrated Fluid Milk Evaporated 60% water removed Sweetened Condensed 15% sugar added Concentrated to 1/3 former volume

19. Types of Milk Dry Milk Whole or low-fat dry milk Dried buttermilk Nonfat dry milk powder Regular Instant

20. Type of Milk Products Cultured Milk Products Addition of bacteria cultures Lactose fermented to lactic acid Yogurt Buttermilk Low fat cultured milk Originally – milk remaining after cream removed to churn butter that cultured Acidophilus milk Kefir

21. Type of Milk Products Filled milk Substitute produced from Nondairy fat such as soybean oil combined with water Nonfat milk solids Emulsifier, color, flavoring Imitation milk Contains no milk per se May contain casein (milk protein)

22. Types of Cream Products Fluid Cream Heavy (not less than 36% fat) Light (30 to 36% fat) Half and half (10.5 to 18% fat) Fat content must be 30% or higher to whip Sour Cream

23. Types of Sour Cream Dried Nondairy products Whipped topping Coffee whiteners May contain casein or whey

24. Heat in Food Preparation Proteins coagulate Calcium is less dispersed Fat globules coalesce Surface films may form Sugars and protein may brown Maillard type

25. Coagulation Acid Casein is highly susceptible Casein particles unstable at pH of 4.6 Enzyme Rennet Optimum temperature 104°F/40°C to 108°F/42°C

26. Coagulation Phenolic compounds Found in fruits and vegetables Salts Salts in milk Sodium chloride

27. Curdling In Cooking Too hot – too long High salt Phenolic compounds Potatoes Acidic ingredients Tomato soup Higher fat milk is more stable than low fat milk Non fat dry milk has limited stability Fresh milk is less likely to curdle than “older milk”

28. Freezing Protein film is weakened Fat globules coalesce Dispersion of protein and calcium phosphate affected

29. Whipping of Cream Temperature and Viscosity Cold cream whips better than warm Fat content 30% fat minimum is needed Amount whipped Other substances Sugar increases time to whip Sugar decreases volume and stiffness Acidity has no effect

30. Whipping of Other Milk Products Evaporated milk Nonfat dry milk

31. Care of Milk Fresh milk Cleanliness Cold temperature Prevention of contamination Protect from light exposure Canned milk Once opened refrigerate

32. Cheese Composition Varies with type of cheese and method of coagulation Concentrated dairy food One pound may contain the protein and fat of one gallon of milk Nutritive value Most high in Protein Calcium and phosphorus Vitamin A Sodium

33. Cheese Manufacture Curd formation Starter culture Coagulating enzyme Cutting curd to release whey Heating curd Draining, knitting, salting, and pressing curd Curing or ripening

34. Ripening Process from the time of precipitation the curd to the desired end product Aging may be brief or extended During ripening of cheese Changes in flavor, aroma, texture, and composition Flavor varies with type of organism Swiss Cheese develops holes Lactose converted to other compounds

35. Grades USDA Grades U.S. Grade AA and A USDA Quality Approved

36. Types of Cheese Vary by moisture Soft Semihard Hard Vary by kind and extent of ripening Unripened Mold ripened Bacterial ripened

37. Types of Cheese Products Cold-pack cheese Process cheese Process cheese foods and spreads Low-fat cheese

38. Cheese Storage Store cold Wrap to prevent drying Mold Freezing

39. Cheese in Cooked Foods Grate, and melt at moderate temperature Well ripened and process cheese preferable Mild cheese more likely to become stringy Melted or heated too hot Fat may separate Cheese becomes tough and rubbery