Dried milk products lactose crystallization

Even though liquid whey has been successfully commercialized in the form of alcoholic and nonalcoholic beverages, these are still a rarity in most countries. Most whey is converted to whey solids as ingredients for human food or animal feeds by traditional processes such as spray drying, roller drying, concentration to semisolid feed blocks, or production of sweetened condensed whey. Jelen (1979) reported other traditionally established processes including lactose crystallization from untreated or modified whey, production of heat-denatured whey protein concentrate, or recovery of milk fat from whey cheese in whey butter. ... 

The most stable form is a-lactose monohydrate, C12H22O11 H2O. Lactose crystallizes in this form from a supersaturated aqueous solution at T < 93.5 °C. The crystals may have a prism-or pyramid-like form, depending on conditions. Vacuum drying at T > 100 °C yields a hygroscopic a-anhydride. Crystallization from aqueous solutions above 93.5 °C provides water-free P-lactose (P-anhydride, cf. Formula 10.10). Rapid drying of a lactose solution, as in milk powder production, gives a hygroscopic and amorphous equilibrium mixture of a- and P-lactose. 

Ethanol and methanol (preferred with less than 3% moisture) have been used to extract lactose from skim milk or whey powders (Kyle and Henderson 1970). The dried lactose powder that crystallized from the alcoholic extract was believed to be anhydrous a-lactose, but other work indicates that the product is a mixture of anhydrous a- and /3-lactose (Lim and Nickerson 1973). 

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