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Effect of Alcohols on Lactose Solubility

Department of Food Science and Technology, University of California, Davis 95616

ABSTRACT

In tests of effects of high (70 to 90% volume/volume) and low (2 and 5% volume/volume) 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 (therefore, the relation was inverse for total alpha). However, 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 whereas 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 long-chain alcohols and controlling suitable parameters enabled recovery of greater amounts and more desirable forms of lactose.