Milk

Acid Curd

-acid added to milk causes proteins to reach isoelectric point; they no longer repel, so stick together and curdle-form curd -bacteria can also be added b/c produces acid=curdling; (cheese)

3 Ways to curdle milk

-add acid, add bacteria, add chymosin (rennin)

Sources of off flavors

-animal's diet spoilage of microorganisms -fat rancidity (hydrolytic and oxidative) -sunlight catalyzed riboflavin + methionine rxn -head: cooked flavor of milk comes from the sulfur compounds in beta lactoglobin

instant dried milk

-evaporated 60% of water off, then sprayed into chamber where remaining water is instantly dried off -instantized = when milk is spray dried, its spray dried into large particles rather than small, which improves the ease of reconstituting it in water

Cultured buttermilk

-fermented milk product; bacteria (cultured) produces lactic acid = sour taste

beta lactoglobulin

-in whey protein -amino acids that contain sulfur; contribute to flavor of milk, including off flavor when milk is heated!

Milk Fat, cream-foaming

-milk fat arranged in large globules that are surrounded by a heavy duty phospholipid membrane -agitation (beating, whipping) damages the globule membrane, allowing air to be incorporated; this causes the globules to stick together and creates whipped cream and butter

Casein

-protein in milk -cause white color -contain phosphorous -arranged micelles; -kappa casein keeps micelles dispersed (also has alpha, beta, and gamma casein)

Casein Micelle

-proteins arranged in dispersed "droplets" with hydrophobic groups inside micelle and hydrophilic groups outside of micelle; micelles dispersed in water

Chymosin

-rennin; enzyme that cleaves off hydrophilic hairs of kappa casein, destabilizing the micelle and causing micelles to clump together and form a curd

Sunlight and Milk's flavor

-sunglight induces the riboflavin to react with methionine (amino acid) to produce off spoiled flavor

sweetened condensed milk

evaporated milk with added sugar -spoils less easily than evaporated milk b/c of sugar

evaporated milk

high heat, evaporates milk to remove about 60% of water; flavor develops from heated beta lactoglobulin (sulfur) and from maillard rxn -then homogenized, canned, sterilized

Kappa Casein

keeps micelle dispersed -on outside of micelle, contains "pink hairs" that are hydrophilic and keep proteins dispersed rather than "clumped" in curds

Milk Fat & Flavor

oleic acid is main contributor; main unsaturated fat in milk

Whey proteins

proteins left after making a casein curd -when curds form, the liquid squeezed out contains whey proteins -contains: beta lactoglobulin and lipase enzyme