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Thermal separation of β-lactoblobulin and α-lactalbumin in bovine Cheddar cheese whey

Authors: R.J. Pearce


Studies on the solubility of purified β-lactoblobulin and α-lactalbumin as a function of temperature, pH and protein concentration indicated that α-lactalbumin aggregated more extensively under certain conditions than β-lactoblobulin and that both the aggregates were totally resolubilized by readjustment of the pH and temperature. The investigation was extended to fresh Cheddar cheese whey, concentrated whey an protein enriched whey under similar conditions to establish the feasibility of separating whey proteins on the basis of differences in solubility. The conditions for maximum precipitation of α-lactalbumin in whey and optimum separation of the proteins were about 65°C in the pH range 4.1 to 4.3 for several minutes. Total depletion of α-lactalbumin was attained by treatment of whey with a protein content increased by a factor of 2 to 5 by ultrafiltration. After this heat treatment, immunoglobulins, bovine serum albumin and some unidentified highly aggregated material coprecipitated with the α-lactalbumin, thus resulting in a supernatant fraction enriched in β-lactoglobulin. The aggregation behaviour of α-lactalbumin under these experimental conditions is discussed with respect to the known denaturation states of the protein and the mechanisms of folding and unfolding. It is suggested that this behaviour of the major whey proteins may form the basis for a process for manufacturing enriched α-lactalbumin and enriched β-lactoglobulin fractions as the separate functional properties may offer advantages over the natural mixture.

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