On food and cooking the science and lore of the kitchen ( PDFDrive ) 44

Cold milk fat and freezing water both form large, solid, jagged crystals that pierce, crush, and rend the thin veil of phospholipids and proteins around the globule, just a few molecules

different story It is fatal to the fat globule membrane Cold milk fat and freezing water both form large, solid, jagged crystals that pierce, crush, and rend the thin veil of phospholipids and proteins around the globule, just a few molecules thick If you freeze milk or cream and then thaw it, much

of the membrane material ends up floating free in the liquid, and many of the fat globules get stuck to each other in grains of butter Make the mistake of heating thawed milk or cream, and the butter grains melt into puddles

of oil

Milk Proteins: Coagulation

by Acid and Enzymes

Two Protein Classes: Curd and Whey There

are dozens of different proteins floating

around in milk When it comes to cooking

behavior, fortunately, we can reduce the

protein population to two basic groups: Little

groups are distinguished by their reaction to acids The handful of curd proteins, the

caseins, clump together in acid conditions and form a solid mass, or coagulate, while all the

rest, the whey proteins, remain suspended in the liquid It’s the clumping nature of the

caseins that makes possible most thickened milk products, from yogurt to cheese The

whey proteins play a more minor role; they influence the texture of casein curds, and

stabilize the milk foams on specialty coffees The caseins usually outweigh the whey

proteins, as they do in cow’s milk by 4 to 1 Both caseins and whey proteins are

unusual among food proteins in being largely tolerant of heat Where cooking coagulates the proteins in eggs and meat into solid masses, it does not coagulate the proteins in milk and cream — unless the milk or cream has

become acidic Fresh milk and cream can be boiled down to a fraction of their volume