SEMIAUTOMATED SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF PECTINESTERASE ACTIVITY IN NATURAL AND PROCESSED JUICES

An automated method for the determination of pectinesterase (PE) activity in food based on the absorbance decrease of a Bromothymol Blue (BTB) solution due to the a-Dpolygalacturonate residues formed in the pectin demethoxylation catalysed by pectinesterase is presented. The approach used is a semiautomatic flow injection (FI) approach. The method exhibits a linear range between 0.1–1.5 U/mL, with a precision, expressed as RSD, of 4.3% and a sampling frequency of 8h-1. The usefulness of the method was tested by determining PE activity in natural and manufactured juices and also applying the standard addition method, with recoveries between 84.8 and 102.6 %.