Preparation and Properties of an Alcohol-Precipitated Whey Protein Concentrate

Abstract

Aqueous methanol, ethanol, n-propanol, and n-butanol were investigated for precipitating whey proteins from liquid and dried whey to prepare a whey protein concentrate. Ethanol was more satisfactory than the other alcohols; methanol and n-propanol whey protein concentrates were slightly less soluble in water and neutral buffer than ethanol whey protein concentrate, and n-butanol whey protein concentrate contained gross amounts of lactose and was practically insoluble in water.The 72% ethanol treatment precipitated 45 to 60% of the whey proteins and produced a whey protein concentrate with ∼ a fourfold protein enrichment on a solids basis compared to whey. Minimum coprecipitation of minerals and lactose with the protein concentrate was produced by treating calcium-free acid whey with 72% (w/w) ethanol at 0 to 5 C. Ethanol extraction of freeze-dried whey was less satisfactory than liquid whey treatments because of substantial coextraction of proteins with the lactose and minerals. Fifty to 70% of the freeze-dried whey protein concentrate was resolubilized at pH 6.6, whereas it was totally soluble at pH 8 to 9. The protein concentrate, which exhibited normal zonal electrophoretic properties at pH 8.6, contained 2 to 3 times as much bovine serum albumin and proportionately less α-lactal-bumin than control whey proteins. Pre-treatments to remove calcium and other minerals from whey and use of ≥ 72% (w/w) ethanol during preparation improved the solubility of the protein concentrates. Possible mechanisms for ethanol-induced whey protein denaturation and precipitation are presented.