• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.666-672
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• 1995

This study was carried out to characterize thermolabile pectinesterase (TLPE) and thermostable pectinesterase (TSPE) separated from crude PE of Valencia orange in order to investigate the preventive measures of cloudy juice clarification. The TLPE was observed to be mixture of several isoenzymes with the same molecular weight of 36 KD (37.5 KD) but different isoelectric point of pH 8.4, 8.7, 8.9, 9.8 and ${\geq}10$ which were unstable at $70^{\circ}C$, and the TSPE also was found to be mixture of two or three isoenzymes with the same molecular weight of 53 KD (50 KD) but different isoelectric point of pH 8.7, 9.2 and ${\geq}10$ which had slightly different stability from one another at $70^{\circ}C$. The TLPE and the TSPE had the optimum reaction pH of 7.0 and $7.0{\sim}8.5,\;appK_{M}$ of 1.1 and 1.7 mg/ml, appVmax of 0.53 and $1.01\;{\mu}mol/min/{\mu}g$, and the turnover number of 19.000 and 54,000 mol/mol/min toward Kodak pectin, respectively. The TSPE had higher storage stabiblity and cloud loss effect on orange juice than the TLPE. Above all, the crude PE was most effective on orange juice cloud loss among the PEs used.