Thermal Treatment Can Modify the Susceptibility of Whey Protein Concentrate to Enzymatic Hydrolysis

Abstract

Susceptibility to enzymes hydrolysis is used as an index of flexibility since partial unfolding of protein molecules generally results in increased hydrolysis rate. Two set of experiments were performed on the effect of thermal treatment in the temperature range of 60-85°C on the susceptibility of whey protein concentrate to enzymatic hydrolysis by Proteinase K at 37°C and pH 7.5 and 8.0. Heat treatment in a certain time-temperature combination results in a significant increase in degree of hydrolysis, as monitored by OPA-NAC technique.
The time-dependent changes in the degree of hydrolysis were described by a fractional conversion model, which enables calculations of activation energy.
Whey proteins concentrate seems to be heat-sensitive for enzymatic hydrolysis, confirming that during heat treatment at neutral/alkaline pH the substrate is changing, since the dimmer dissociates with the exposure of hydrophobic residues.