Modification of pectin by pectinmethylesterase and the role in stability of juice beverages

The colloidal stability of juices and pectin stabilized juice drinks depends in part on the charge and charge properties of pectins. The effect of pectinmethylesterases (PMEs) from Valencia juice sacs on the rate of clarification of citrus juice and modification of pectin are described in this study. Partially purified PME extracts that contained peptides at 36,000 and 27,000 daltons are more likely to cause clarification of citrus juices than PME extracts that contained peptides at 36,000 and 13,000 daltons. In the presence of active PME, cations enhance clarification and increase particle size of citrus juices. PME extracts that contained 36,000 and 13,000 peptides de-esterified commercial pectin in the presence of sodium chloride at pH 7.5, without loss of molecular weight. Based on elution from ion exchange, pectins of greater charge density are created at longer reaction times with PME, but some pectin chains remained unmodified.