DIETARY FIBRES OF APPLE AND APRICOT PASTES: EFFECT OF HEATING ON PLANT CELL WALLS

Abstract

Fruit pieces prepared from pastes are now commonly added to breakfast cereals, snack bars and “healthy” confectionery. The objective was to determine the cell wall composition of heat-treated apple paste and apricot paste. The cell walls of apple paste and apricot paste were isolated and sequentially fractionated separately using HEPES, CDTA, Na₂CO₃, 1M KOH, 4M KOH leaving a final residue. The monosaccharide composition of the fractions was consistent with the presence of cellulose, pectic polysaccharides, xyloglucans, heteroxylans and galactoglucomannans. The heat treatment during the apple paste and the apricot paste production did not change the overall amounts of neutral monosaccharides. Heat treatment resulted in the considerable solubilization of pectic polymers in water-soluble and CDTA-soluble fractions compared to Na₂CO₃, KOH and final residue fractions of the fruit pastes. During heat treatment, tissue softening occurs due to the disruption of the constituent cell wall matrix.