Effect of Ultra-High-Temperature Steam Injection on Model Systems of α-Lactalbumin and β-Lactoglobulin

Abstract

Model systems of proteins of milk serum were heated to 143 ± 1 C by steam injection, held for 8 to 10 s and vacuum cooled. α-Lactalbumin was more resistant to heat denaturation when processed alone than when mixed with β-lactoglobulin according to electrophoretic and densitometric quantification. Variants A and B of β-lactoglobulin were sensitive to ultra-high-temperature processing. A new component with mobility intermediate between α-lactalbumin and β-lactoglobulin formed after ultra-high-temperature processing. Analysis of the new component indicated that it was a protein complex of α-lactalbumin and β-lactoglobulin. β-Lactoglobulin was the major source of available sulfhydryls. The experimental sulfhydryl value for a mixture of α-lactalbumin and β-lactoglobulin was 17% lower than calculated from the composition of the mixture. This was possibly because sulfhydryl groups are involved in the heat-induced complex. © 1978, American Dairy Science Association. All rights reserved.