1. MILK
MILK PRODUCTS

2. COMPOSITION OF MILK
Water %
Total milk solids %

3. CARBOHYDRATE – 5% Lactose – main CHO
Low solubility, may precipitate out as grainy substance during heat treatments
Converts to lactic acid with souring or fermentation – lactose stays in whey
Part of milk solids non fat
Less sweet than sucrose

4. FAT 3-4% for whole milk, varies according to state law
Primarily triglycerides, then phospholipids, sterols
Mix of unsaturated, monounsaturated, polyunsaturated
High level of short chain – contribute to milk flavor and low melting point of butter
Fat globules less dense than water  less stable
Milk is an emulsion
“Creaming” process – fat rises to the top

5. PROTEINS

6. CASEIN Primary proteingroup of similar proteins – micellular proteins
Colloidally dispersed, poorly hydrated, calcium sensitive, excellent emulsifiers
Can be separated by acidification to bring to isoelectric point (4.6)
Rennin- enzyme also precipitates casein clotting, clabbering, curdling when milk sours

7. WHEY Lactalbumin and lactoglobulin
More hydrated than casein, denatured and precipitated by heat >600C or 1400F forms scum on bottom of pan  scorches
Not precipitated with acid or rennet
Lactose precipitates with the whey
Enzymes – lipase, protease, alkaline phosphatase
Casein and whey part of milk solids non fat

8. VITAMINS Fat soluble - naturally in fat component in whole milk
High in vitamin A, some D
Fair source of water soluble vitamins (B), excellent riboflavin
Small amounts of vitamin C
Fortified with Vitamin A and D

9. MINERALS
Calcium
Phosphorus
Magnesium
Potassium
Sodium
Chloride
Sulfur

10. PIGMENTS
Fresh whole milk  ivory caused by refraction of light in dispersed particles
Skim milk  bluish cast
Carotene and riboflavin yellow tinge
Riboflavin  green tone

11. FLAVOR OF MILK
Mouthfeel due to emulsified fat, colloidally dispersed proteins, lactose, milk salts
Fresh milk contains acetone, actealdehyde, methyl ketones, and short chain fatty acids to provide aroma
Normally a mild sweet flavor
Heat processing changes flavor
Affected by physical condition of cow and composition of the feed

12. OFF FLAVORS Main cause  pasture weeds
Old or moldy feed rancid or bitter flavors
Oxidation of fat  oxidized phospholipids
 fishy odors
Exposure to sunlight changes riboflavin and milk proteins

13. CLASSIFICATION OF MILK

14. SOLUTION Sugar - lactose Water-soluble vitamins thiamin & riboflavin
Mineral salts, and minerals

15. COLLOIDAL DISPERSION
Casein bound to calcium phosphate in micelle - too big to dissolve
Whey proteins

16. EMULSION
Unstable due to large droplet phase of fats, temporary

17. MILK PROCESSING

18. SANITATION AND QUALITY
PHF
Grade A Pasteurized Milk Ordinance
USDA, US Public Health Service (FDA) and state departments of agriculture regulate milk and milk products
Voluntary

19. GRADES Grade A – available to consumer – fluid milk
Grade B & C higher bacterial count, safe, wholesome
Grade US extra and US standard used for dried milk
Grades based on bacterial count of fresh milk
Given on a voluntary fee for service basis

20. PASTEURIZATION
Treating with heat to kill pathogens and inactivate spoilage enzymes; some spoilage organisms may survive so cool promptly and hold under refrigeration
Destroys lipase which catalyzes hydrolytic rancidity
Process is time/temperature dependent
Alkaline phosphatase - same heat denaturation curve as milk pathogens; presence indicates inadequate pasteurization

21. TIME/TEMPERATURES
Use high temperature, short time (H.T.S.T.) 162F, 72C for 15 seconds
Low temperature longer time
Ultra-high temperature (U.H.T.) - growing, 280F for 2-4 sec. May develop cooked flavor, use in shelf stable products, often used with cream, eggnog, half and half

22. STERILIZATION Only occurs with ultra-high temperatures for 2-6 seconds
Can be aseptically packaged; no refrigeration until opened

23. HOMOGENIZATION
Prevents creaming; maintains more uniform composition, optional process
Mechanically reduces size, increases number of fat
globules permanently emulsifies fat globules
Characteristics:
Whiter milk
More viscous, creamy milk
More bland - fat globules smaller
Less stable to light
Increased chance of rancidity

24. FORTIFICATION Whole milk - optional addition of A & D
Lowfat milk, nonfat, low-fat chocolate - Must be fortified for A
Addition of D optional but routinely practiced
To increase viscosity, appearance, and nutritive value of lowfat milk, nonfat milk solids may be added – states protein fortified or fortified with protein

25. BLEACHING
FDA - benzoyl peroxide or benzoyl peroxide with potassium alum, calcium sulfate, and magnesium carbonate to be used as a bleaching agent in milk to remove pigments such as carotenoids and chlorophylls
Vitamin A or precursors may be destroyed  sufficient A added into milk or curd (for cheesemaking)

26. TYPES OF MILK

27. FLUID Must be free of pathogenic bacteria
Fat content and % of MSNF subject to FDA regulations
Flavored – same nutrients as milk to which flavor added
Certified milk – limited distribution due to cost, sanitary standards very high
Eggnog- mixture of dairy ingredients (cream, milk) egg yolk containing ingredients, nutritive carbohydrate sweeteners.

28. OTHER FLUID MILK
Canned whole milk – homogenized, sterilized, canned aseptically
Frozen whole milk – homogenized, pasteurized, fat separates when thawed, protein denatured by freezing
Skim or nonfat – as much fat as possible removed, minimum of MSNF, fortified with vitamin A. Optional: vitamin D, emulsifiers, stabilizers
Low-fat milk – some fat removed, named according to fat remaining, minimum MSNF, fortified with vit. A. Optional: Vit. D, emulsifiers, stabilizers
Labeled with protein fortified if MSNF >10%

29. CONCENTRATED MILKS

30. EVAPORATED MILK Concentrated through process of evaporation
Evaporated in a vacuum chamber
Whole or nonfat – 60% of H2O removed
Homogenized, fortified, canned, sterilized
Increasingly less stable with progression of concentration and heat  may coagulate  prevent by forewarming
Maillard reaction  light tan color
Reconstitute 1:1 ratio

31. CONDENSED MILK Similar in content and use to evaporated milk
NOT sterilized
Perishable at temperatures above 450F

32. SWEETENED CONDENSED MILK
Concentrated whole or nonfat milk
60% of H2O removed
Sweetened with sucrose or dextrose prior to concentration
40-45% sugar level, may cause grittiness
Pasteurized, not sterilized due to high concentration of sugar
Used in pie filling – thickening occurs because concentrated proteins coagulate from the effect of added acid

33. DRIED MILK Processed from whole or nonfat milk (more common)
Condensed 2/3 of H2O removed
Sprayed into heated vacuum chamber  less than 5% moisture level
Most nonfat fortified
“Instant” or “agglomerated” – some moisture added back pourable, dispersible, in cold H2O
May also dry buttermilk, whey

34. CULTURED AND FERMENTED MILK AND MILK PRODUCTS

35. CULTURED/FERMENTED
Cultured products fermented by addition of bacterial cultures-Streptococci and Lactobacilli
Ferment lactose  lactic acid; create low pH to coagulate casein
Acidified products – souring milk with acid, with or without microorganisms
Cultured and acidified products contain different amounts of lactic acid  different flavors

36. BUTTERMILK
Traditionally liquid left after churning butter, differs from nonfat milk due to content of phospholipids and proteins from fat globule, NFDM solids added
Cultured buttermilk – pasteurized lowfat or nonfat milk with Lactobacilli and Streptococci added
Acidified buttermilk – lactic acid producing bacteria not compulsory
Smooth cultured flavor, high acid content useful in cooking

37. SOUR CREAM Traditionally heavy cream soured
Pasteurized, homogenized fresh light cream
Coagulated similar to buttermilk
Flavors, stabilizers added
Proteolytic bacterial enzyme activity may cause bitter flavor after 3-4 weeks

38. YOGURT
Culture pasteurized dairy product with lactobacillus bulgaricus and streptococcus thermophilis
National Yogurt Association seal for live and active bacteria; at least 100 million bacteria/gram at time of manufacture
Yogurt with viable strains of bacteria eaten in sufficient quantities some will survive passage through stomach and release lactase in the intestine

39. OTHER PRODUCTS
Acidophilus milk - pasteurized low-fat or nonfat milk with Lactobacillus Acidophilus added, Bacteria can live in intestine and produce number of B vitamins
Reduced Lactose milk - pasteurized milk treated with lactase
sweeter than regular milk
Kefir– fermented dairy products, kefir grain yields bacteria added to milk
Koumiss – milk heated before fermentation
Ferments to yield soft curd with yeasty sour curd with mild alcoholic flavor

40. MILK SUBSTITUTES
Imitation milk – combination of several nondairy ingredients; nutritionally inferior
Substitute milk – nutritionally equivalent; reduced calories or fat, usually milk derivatives ( casein, casein salts, whey)
Filled milk – substitute milk with milkfat replaced with vegetable oil

41. CREAMS

42. DESCRIPTION High fat component separated from milk
Federal standards must have at least 18% milkfat
Yellow, fat-soluble pigments visible

43. TYPES Light coffee cream – 18-30% Light whipping cream – 30-36%
Heavy cream – 36% butterfat, minimum
Half and half – cream diluted with nonfat milk 10.5%

44. PRINCIPLES OF USING MILK AND MILK PRODUCTS

45. EFFECTS OF HEAT Prolonged heating adversely affects:
Flavor – dependent on length of time of heating and temperature reached
Due to production of sulfur compounds from denaturation of whey proteins
Due to caramelized flavor from Maillard reaction
Odor
Cooking properties

46. HEAT AND MILK PROTEINS
Heated milk forms precipitate on bottom and sides of pan – coagulated whey proteins
Precipitated proteins tend to scorch
One whey protein component produces a low volume in yeast breads made with unheated milk- scalded milk greater volume in yeast breads
Heated in uncovered pan forms “skin” – coagulated proteins, fat, minerals because milk drying out on top
Prevents steam from escaping  boil over

47. HEAT AND MILK PROTEINS Casein changes little under normal heating
May not take place until milk has been boiled for 14 hours
Temperatures above boiling  cleavage of peptide and phosphate bonds
In concentrated milks coagulation greater due to protein concentration
Unstable emulsion like soured milks accelerate coagulation with heat

48. HEAT AND MILK MINERALS Decreases dispersion of calcium phosphate
Precipitates and becomes enmeshed in whey proteins on bottom of pan

49. EFFECT OF ACID Normal pH = 6.5-6.7 Add acid  pH decreases
Below 5.1 casein destabilizes
At pH 4.5 casein salts formed  milk curdles
Coagulum traps whey which is released when curd is cut, stirred, or heated
Curd is soft, fragile
Cheese from acid coagulation is low in calcium compared to whey
Cream of tomato soup – separates milk proteins
Acids in fruits curdle milk in smoothies
Add lemon juice to sauce at end of cooking

50. EFFECT OF ENZYMES Coagulate proteins
Clabbered by rennin – stomach of milk-fed calves – extract is rennet, now use pepsin from hog stomachs
Genetically engineered rennet from genetically modified Aspergillus mold
Clots are tough, rubbery, contain most of calcium
Add to warm milk for optimal activity

51. EFFECT OF ALKALI Baking soda, for example
Stabilizes colloidal dispersions

52. EFFECT OF POLYPHENOLIC COMPOUNDS
Tannins
Astringent compounds found in fruit, vegetables, plant foods
Produce curdling especially if soured or destabilized by heat
Potatoes cause curdling in scalloped dishes

53. EFFECT OF SALT In high concentration will destabilize a gel
Influences coagulation of casein
Ham added to milk-based dish high sodium content curdles surrounding liquid