HEAT-INDUCED GELATION OF THE MIXTURES OF ALPHA-LACTALBUMIN AND BETA-LACTOGLOBULIN IN THE PRESENCE OF GLUTATHIONE

The optimum conditions for obtaining the maximum gel strength upon heating mixtures of alpha-lactalbumin and beta-lactoglobulin were investigated at different concentrations of glutathione (reduced type) and NaCl. Gel strength was determined after heating at 80-degrees-C for 15 min at pH 6.3 and a protein concentration of 8%. Maximum gel strengths for mixtures of alpha-lactalbumin and beta-lactoglobulin in the ratio of 2:8, 5:5, and 8:2 were obtained at glutathione and NaCl concentrations of 0 mm and 86 mm, 43 mm and 116 mm, and 45 mm and 83 mm, respectively, Multiple regression analysis indicated that both glutathione and NaCl contributed significantly (p less-than-or-equal-to 0.01) to gel formation. The promotion of gel formation with glutathione was postulated to result from glutathione reacting with intramolecular disulfide bonds in the alpha-lactalbumin and beta-lactoglobulin, thereby resulting in conformational changes. It was postulated that alpha-lactalbumin and beta-lactoglobulin were interacting in the gelation of the mixed proteins.