DEGRADATION OF WATER-SOLUBLE FIBER POLYSACCHARIDES IN CARROTS AFTER DIFFERENT TYPES OF PROCESSING

The molecular weight distribution and the viscosity of water-soluble p olysaccharides isolated from carrots were investigated after different types of heat-treatment, commonly used when preparing food. The mater ials studied were blanched, boiled, microwaved and canned. Freezing, w ithout any heat-treatment, was used as a reference process. The water soluble polysaccharides were isolated using two different procedures, i.e. before and after enzymic digestion of protein and starch. Only mi nor differences in molecular weight distribution between frozen and bl anched materials could be detected by gel-filtration. However, when th e carrots were further heat-treated, i.e. boiled, microwaved and canne d, there was an increase in both the high molecular and the low molecu lar weight fractions of soluble polysaccharides (especially pectic sub stances) isolated after digestion of protein and starch. This indicate d a solubilization of originally insoluble material, as well as a degr adation of the soluble high molecular weight material. On the other ha nd, in the polysaccharide fraction isolated directly, i.e. without any degradation of protein and starch, there was an increase only in the low molecular weight fraction and only when the materials were microwa ved and canned. The viscosity of polysaccharides isolated without degr adation of protein and starch could be correlated with the extent of d egradation of the polysaccharides, and thus also with the degree of he at-treatment, in the following order: freezing, blanching, boiling, an d canning. However, the viscosity of soluble fibre isolated after degr adation of protein and starch was similar and low for all materials st udied.