CHARACTERIZATION OF RESIDUAL PECTINS FROM RASPBERRY JUICES

The influence of different manufacturing steps, like enzymic mash treatment, water extraction of pomace and juice enzymation, on the amount and composition of colloids of clear raspberry juices is investigated. The colloid concentrations were in a range between 1.09 and 4.20 g/l. The kinetics of the enzymic degradation of the raspberry pectins with two commercial pectinases and a mixture of purified pectinesterase and polygalacturonase were monitored. The residual pectins of raspberry juice produced with enzymic mash and juice treatment were further characterized. An arabinogalactan type II with a Ara/Gal ratio of 0.59 and an apparent molecular mass of 40 000 Da was found as well as several populations of rhamnogalacturonans with a broad range of apparent molecular masses. Compared with apple juice, the residual rhamnogalacturonans from raspberry juice contain higher moieties of arabinose as highly branched arabinans and lower amounts of galactose. Also, 1,4-linked galactan chains were found in small amounts. The isolated polymers are involved in clarification and filtration problems of raspberry juices and concentrates.