Enzymolysis kinetics, thermodynamics and model of porcine cerebral protein with single-frequency countercurrent and pulsed ultrasound-assisted processing

• KM value in this ultrasound enzymolysis decreased by 9% over the traditional one.
• The ultrasound pretreated cerebral protein increased k significantly (P < 0.05).
• Significant reduction in Ea, ΔH, ΔS was observed by treated protein (P < 0.05).
• A general kinetic equation for treated protein enzymolysis model was DH=5.78ln1+3.4946e0s0+0.1219t.

The present work investigated the enzymolysis kinetics, thermodynamics and model of porcine cerebral protein (PCP) which was pretreated by single-frequency countercurrent and pulsed ultrasound. The kinetic constants for ultrasonic pretreated and traditional enzymolysis have been determined. Results showed that the value of KM in ultrasonic PCP (UPCP) enzymolysis decreased by 9% over that in the traditional enzymolysis. The values of reaction rate constant (k) for UPCP enzymolysis increased by 207%, 121%, 62%, and 45% at 293, 303, 313 and 323 K, respectively. For the thermodynamic parameters, ultrasound decreased activation energy (Ea), change in enthalpy (ΔH) and entropy (ΔS) by 76%, 82% and 31% in PCP, respectively. However, ultrasound had little change in Gibbs free energy (ΔG) value in the temperature range of 293–323 K. Therefore, a general kinetic equation for the enzymolysis model of UPCP by a simple empirical equation was suggested. The experimental values fits with the enzymolysis kinetic model with a low average relative error (4%) confirmed that the kinetic model was accurate to reflect the enzymolysis process. The positive effect of single-frequency countercurrent and pulsed ultrasound in this study and application of the kinetic model may be useful for the release of bioactive peptides from meat processing by-products.