DETERMINATION OF RESIDUAL PECTIN METHYLESTERASE ACTIVITY IN FOOD-PRODUCTS

A method for the determination of a low level of pectin methylesterase activity from vegetable products is described, The method is based on an affinity chromatography technique that employs a resin-bound pecti n methylesterase inhibitor, purified from kiwi fruit, which selectivel y binds the pectin methylesterase. The resin has the capacity to conce ntrate the enzyme, allowing measurement of enzyme activities too low t o be determined by commonly employed techniques and commensurate with those found in pasteurized food products, The enzyme is eluted from th e resin at alkaline pH (9.5) and assayed by a pH-stat method. Depulped orange juices containing different amounts of pectin methylesterase w ere prepared and used to determine enzyme recovery. The results show a recovery of 90% with a standard deviation of 6.8%.