Effect of Alcohols on Lactose Solubility

Abstract

In tests of effects of high (70-90% vol/vol) and low (2 and 5% vol/vol) alcohol concentrations, solubility of lactose decreased with increased alcohol concentration and decreased as alcohol chain length increased. Since lactose has lower solubility in alcohol, crystallization would be expected to be speeded by increased supersaturation. Composition of precipitates formed by the action of ethanol changed with time; .alpha.-lactose precipitated more rapidly at first, then .beta.-lactose. Time of crystallization was related directly to the percentage of .beta.-lactose (and the relation was inverse for total alpha). The percentage of .alpha.-hydrate increased with time and with water content. Agitation during crystallization increased production of .beta.-lactose. Composition of the lactose precipitate varied greatly with concentration of alcohol (ethanol). When ethanol concentration was low, only .alpha.-hydrate was precipitated; at higher concentrations stable anhydrous .alpha.-lactose also was precipitated, with the percentage of total alpha decreasing while the percentage of .beta.-lactose increased. Crystal shape changed from prisms initially to partially or fully developed tomahawks as time went by or as the percentage of ethanol decreased, and crystal color increased with crystallization time and as ethanol percentage decreased. Choosing longchain alcohols and controlling suitable parameters enabled recovery of greater amounts and more desirable forms of lactose. Solubility is an important characteristic of lactose since it influences recovery of lactose from whey, the type of lactose crystals produced, and the tendency of crystals to form in food containing lactose.