Milk.ppt

Chapter 8 Milk and Milk Products
Milk
Milk should contain
% milk-solid-not-fat
% milk fat
Milk is ...
a true solution for salts, lactose, water-soluble vitamins
milk is a colloidal dispersion for proteins and some Ca phosphate
a dilute emulsion for fat globules
Milk
pH of milk: at 25oC
when heated, pH decreases, H+ are liberated when Ca phosphate precipitates
Freezing Point: slightly lower than water
Lower surface tension than water due to presence of milk fat, protein, free fatty acids, & phospholipids: easy to ponents of milk varies with the feed, breed, nutrition & the physiological condition of the cow
ponentsof Milk
Water: 87%, aw =
Proteins: caseins, whey proteins, enzymes
Lipids: mainly triglycerides
Carbohydrates: mainly lactose, also glucose, galactose, & other harides
Salts (<1%),
Trace elements,
Vitamins
Milk Proteins - Caseins
Phosphoproteins, account for 80% of total milk proteins
Four groups: alfas1-, alfas1, Beta-, & Kappa-caseins
Present in milk as micelles, stabilized by Kappa-caseins & Ca phosphate
Easily precipitated by adding acid to pH -
Milk Proteins - Caseins
Acid precipitates caseins
Rennin casein: enzyme rennin coagulates caseins, when Kappa-casein is destroyed by rennin (enzyme from the stomach lining of calves), other caseins react with Ca to form a coagulum
Caseinates: salts of caseins, highly soluble, used as emulsifier, binder, thickening, foaming & gelling
Milk Proteins -  Whey proteins
Not precipitated by acid, but easily denatured by heat (>60C)
Four Fractions: -lactoglobulins (50%), -lactalbumins (25%), serum albumin & immunoglobulins
rich in sulfur-containing amino acids
Milk Proteins -  Whey proteins
Use of whey protein products:
Dried Whey: puddings, cakes, baked products
Whey protein concentrates: binder in sausage (up to %)
Ultra Filtered Skim Milk : coffee whiteners
Cheese Whey: animal feed
Milk Proteins - Enzymes
Most of the enzymes are inactivated by pasteuriz