Non-starch polysaccharides of tomatoes II. Influence of thermal processing

A series of samples was taken from different stages of an industrial production process for tomato puree and was analysed for the contents and composition of the non-starch polysaccharides (NSP). The NSP were fractionated into the pectins, hemicelluloses and cellulose groups. All fractions were methanolysed to give their sugar and uronic acid percentages and were characterized for the maxima of their molar mass distributions. During the hot-break of tomatoes, the pectins and cellulose were reduced considerably by enzymatic degradation, owing to the action of tomato polygalacturonases and cellulases. Anion exchange chromatography of the pectins showed a simultaneous demethylation by pectinmethylesterases. Keeping the tomato pulp for 10 min at 100 degrees C caused additional NSP losses by hydrolysis and/or beta-elimination. The hemicelluloses were affected only to a minor extent and showed no essential alterations. Some of the pectins were removed by squeezing off some liquid serum from the pulp, but a tomato puree with the desired high-molecular pectins was left behind. However, a substantially improved texture quality is expected when the loss of NSP is avoided by a more effective deactivation of the enzymes.