Simplified short-time method for the esterification of milk proteins

beta -Lactoglobulin, alpha -lactalbumin and beta -casein at protein concentration of 5\% or higher were esterified using methanol, ethanol, propanol and isopropanol and different levels of hydrochloric acid in the range 10-80 molar ratio (MR, mole acid/mole carboxyl group) when performing the reaction at 4 degreesC for up to 10 h. The reaction product was recovered either by centrifugation of filtration. Esterifications can reach high yields after 6 h reaction. The electrophoretic patterns of esterified proteins indicated a reduction of the negative charges of the proteins and the absence of molecular weight changes. The extent of esterification was dependent on the alcohol used, methanol being the most reactive in the esterification process. It was also dependent on the protein nature of the substrate, alpha -lactalbumin being the most resistant to the nucleophilic attack of the alcohols.