THERMOSTABILITY AND ORANGE JUICE CLOUD DESTABILIZING PROPERTIES OF MULTIPLE PECTINESTERASES FROM ORANGE

Abstract

ABSTRACT Three forms of pectinesterase, accounting for 95% of the activity in Navel orange, showed considerable differences in heat stability and orange juice cloud destabilizing properties. Pectinesterase I and II (isoenzymes) and a so‐called high molecular weight pectinesterase were rapidly inactivated at 70°C, 60°C, and 90°C, respectively. In chilled juices (5°C) the high molecular weight pectinesterise was the only enzyme which rapidly produced methanol and destabilized the cloud. Although this enzyme represents only 5% of the total pectinesterase activity in Navel orange, it is thought that it is largely responsible for gelation which may occur in concentrates produced by the cut‐back process.