Comparison of conventional heat treatment with selected non-thermal technologies for the inactivation of the commercial protease Protamex™

Preparation of protein hydrolysates for food use requires the elimination of residual enzyme activity after the hydrolysis reaction, which is usually achieved by thermal inactivation. However, precise data on inactivation of commonly used enzymes is still not readily available. Sodium-caseinate hydrolysates were produced with the commercial protease Protamex™. A conventional thermal method to terminate enzymatic hydrolysis was evaluated and complete inactivation of Protamex™ was attained at 95 °C for 20 s. High intensity light pulses (HILP), Pulsed Electric Fields (PEF), and ultrasound (US) were evaluated as methods to terminate enzymatic hydrolysis. HILP was effective in inactivating Protamex™ in solutions with high optical transmittance particularly in the UV region. A 90% reduction in Protamex™ activity was achieved after a 1 min treatment with no significant temperature increase. A PEF treatment (18.2 kV/cm, 500 pulses) gave a 70% decrease in Protamex™ activity in a hydrolysate solution while sample temperatures remained below the range for thermal inactivation. Thermosonication did not decrease enzyme activity at temperatures <60 °C and at temperatures >60 °C any inactivation observed was most likely due to thermal effects. Despite the promising results, further optimisation would be required before these technologies could be considered as alternatives to conventional heat treatments.