THE EFFECTS OF WATER-SOLUBLE ARABINOXYLAN ON GELATINIZATION AND RETROGRADATION OF STARCH

The effects of soluble pentosans, in the form of the main water-soluble arabinoxylan from rye grain, on the gelatinization and retrogradation of starch were studied. Five different starches, waxy, amylomaize, wheat, maize and potato starches and wheat flour were used. The water contents of the samples varied from 46.5 to 50%. Differential scanning calorimetry (DSC) showed that the arabinoxylan had a negligible effect on the gelatinization. However, the arabinoxylan did affect the retrogradation. The recrystallization process is particularly sensitive to the water content in the sample. The maximum extent of recrystallization occurs when the starch concentration is between 50 and 60%. The effects of the arabinoxylan are probably caused by the water absorption ability of the arabinoxylan, i.e. control of the water availibility of the starch which thereby, increases the retrogradation. The effects of arabinoxylan addition are, however, dependent on the initial starch concentration. The results of the rheological measurements agreed with the DSC measurements because potato starch gels (42.6-42.8% on dry matter basis (d.b.)), with added (2% d.b.) arabinoxylan, were more rigid after seven days of storage than pure potato starch gels.