Evaporated Milk For Recipes Ii
Casein May be defined as the major protein which is precipitated at pH 4.6 and is exclusive to milk. It is present in spherical bodies as micelles which vary in size with negative surface charge. The caseins of milk may be sub-divided into five main classes αs1 αs2 β gamma and k-caseins. In milk casein is present in combination with calcium in the form of calcium caseinate or more precisely calcium hyhdrogen caseinate. Whey proteins Are those in the whey fraction after the precipitation of casein at pH 4.6. These are the alpha-lactalbumin beta-lactoglobulin immunoglobulins lactoferrin transferrin proteose-peptone fractions etc. Most of these are globular proteins subject to heat denaturation. α-lactalbumin exists in variants A and B forms and is susceptible to denaturation by unfolding of the tertiary structure. β-lactoglobulin is identical to blood globulin and insoluble in water and is responsible for the transfer of antibodies.
Short and medium chain fatty acids with 4-12 carbon atoms which occur at comparatively higher concentration in milk fat reported to have antibacterial and fungistatic activity. Milk fat plays another important role in preventing tooth decay by forming a protective coat over the surface of enamel. It is composed of triglycerides of fatty acids. A fatty acid molecule is composed of hydrocarbon chain and carboxyl group. Triglycerides are of two types simple and complex. In simple all the three fatty acids are of same nature whereas complex triglycerides on hydrolysis give glycerol and different fatty acids. The milk fat exists in the form of small globules of sizes ranging from 2 to 10 microns with different glycerides of low melting points in suspension.
Milk fat varies in amount and composition according to the breed species feed and lactation time of which feed being a major factor. Fat is distributed in globules as triglycerides (98-99 %) fat globule membrane in combination with phoshpholipids and lipoprotein (0.2 to 1.0 %) and also as free fatty acids cholesterol and phospholipids in the serum. Phospholipids These contain phosphorus in their molecules in addition to the fatty acids and glycerol; they also contain a nitrogenous base. Principally milk phospholipids are the Lecithin Cephalin and Sphingomyelin. Though fat-soluble they are hydrophilic and imbibe large quantity of water and swell. They are used as antioxidants for fat rich dairy products. Vitamins Various vitamins present in milk are as follows.