Lactose Crystallization in Dry Products of Milk. II. The Effects of Moisture and Alcohol

Summary The effects of moisture and 95 per cent ethanol on the crystallization of lactose in dry products of milk have been studied. Results indicated a moisture level of about 6.5 to 7.0 per cent for spray-process dry whole milk and 7.5 to 6.0 per cent for both spray and roller-process nonfat dry milk solids. Below these critical moisture levels, very little crystallization took place, while, above these levels, crystallization of the lactose proceeded rapidly and extensively. For spray-process dry whole milk, it has been found that treatment with methanol and 95 per cent ethanol caused very little of the lactose to crystallize as the α-monohydrate. Increasing the water content of the alcohol increased crystallization. It is suggested that the freeing of the fat in spray-process dry whole milk by 95 per cent ethanol results from coagulation of the milk proteins and not from crystallization of the lactose as the monohydrate.