KINETIC STUDIES OF AN AMYLASE USED COMMERCIALLY FOR THE CLARIFICATION OF APPLE JUICE

Abstract

The effect of substrate and enzyme concentrations on the degradation of soluble corn starch with a commercial amylase (Rohalase HT) recommended for apple juice clarification was studied. The reaction was conducted at 50C at different pH values (3.6-5.6). Starch solutions containing from 2.48 to 14.85 mg/mL were used as substrate in the experiments. Influence of Ca 2+ on amylase activity was also determined. Obtained results showed that amylase exhibits an optimal activity pH value of 4.6, following a Michaelis-Menten type kinetics (K m = 8.11 mg/mL and ν max = 2.19 U/mg enzyme). The activity of amylase decreased significantly when CaCl 2 was added to the amylase solution (final amylase concentration in reaction mixture: 5-10 mM). An empirical equation relating the rate of product of hydrolysis formation (dC m /dt) with starch (C st ) and amylase (C e ) concentrations was obtained: dC m /dt = 1.18 × C 0.77 e × C1.03st × [1-exp(-0.11 × t)]. Cette etude evalue l'effet des concentrations en substrat et en enzyme sur la degradation d'amidon de mais soluble avec une amylase commerciale recommandee pour la clarification de jus de pomme. Les resultats indiquent que l'amylase a une activite optimale a pH 4,6, suit des cinetiques de type Michaelis-Menten (K m = 8.11 mg/mL et ν max = 2.19 U/mg enzyme). L'addition de CaCl 2 reduit significativement l'activite de l'enzyme.