Degradation of α-Lactalbumin and β-Lactoglobulin by Actinidin

Abstract

Susceptibility of the two major whey proteins, β-lactoglobulin and α-lactalbumin, to enzymatic degradation by actinidin as a function of pH and temperature was examined by a response surface methodology in order to elucidate the enzymatic action of the protease for controlled modification of these whey proteins. Pure whey protein fractions and commercial spray-dried whey were degraded by actinidin. The simultaneous effects of pH and temperature, in a range of 2.3 to 5 and 41 to 58°C respectively, on whey proteins degradation were studied, demonstrating a clear interrelationship between these two variables. With commercial whey, extended proteolysis of both β-lactoglobulin and α-lactalbumin was observed at pH 4.0 and temperature of 41.6°C; after an incubation time of 120 min, a degradation of 43.6% was obtained for the former, and 89.1% for the latter. Assays on pure proteins showed a complete degradation of α-lactalbumin and a 65.3% of degradation for β-lactoglobulin; therefore, the former appeared to be more susceptible to actinidin proteolysis.

Keywords:

• Actinidin
• α-Lactalbumin
• β-Lactoglobulin
• Whey proteins

Acknowledgments