Influence of ultrasound pretreatment on enzymolysis kinetics and thermodynamics of sodium hydroxide extracted proteins from tea residue

Abstract

The effect of ultrasound pretreatment using Single Frequency Counter Current Ultrasound (SFCCU) on the enzymolysis of tea residue protein (TRP) extracted with sodium hydroxide was investigated. The concentration of TRP hydrolysate, enzymolysis kinetics and thermodynamic parameters after SFCCU pretreatment were determined and compared with traditional enzymolysis. The results indicated that both ultrasound assisted and traditional enzymolysis conformed to first-order kinetics within the limits of the studied parameters. Temperature and sonication had affirmative effect on the enzymolysis of TRP with temperature yielding greater impact. Michaelis constant (K_M ) in ultrasonic pretreated enzymolysis decreased by 32.7% over the traditional enzymolysis. The highest polypeptide concentration of 24.12 mg ml⁻¹ was obtained with the lowest energy requirement at improved conditions of 50 g L⁻¹ of TRP, alcalase concentration of 2000 U g⁻¹, time of 10 min and temperature of 50 °C for the ultrasonic treated enzymolysis. The values of reaction rate constant (k) for TRP enzymolysis increased by 78, 40, 82 and 60% at 20, 30, 40 and 50 °C, respectively. The thermodynamic properties comprising activation energy (Ea), change in enthalpy (∆H) and entropy (∆S) were reduced by ultrasound pretreatment whereas Gibbs free energy (∆G) was increased.

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