Cereal Chem 54:150 - 160. | VIEW
Effect of Pentosans on the Retrogradation of Wheat Starch Gels.
S. K. Kim and B. L. D'Appolonia. Copyright 1977 by the American Association of Cereal Chemists, Inc.
The effect of wheat-flour pentosans (water-soluble and water-insoluble) on the process of aging of wheat starch, starch-amylose, and starch-amylopectin gels stored at 21 and 30 C was examined with an Instron Universal Testing Instrument. Kinetic studies indicated that the basic mechanism of retrogradation of starch is instantaneous nucleation followed by rod-like growth of crystals. Pentosans had a definite effect in retarding the retrogradation of starch gels upon aging, and the effect exerted by the water-insoluble pentosans was more pronounced than that exerted by water-soluble pentosans. The water-soluble pentosans slowed down the rate of retrogradation by affecting the amylopectin fraction of starch, while the water- insoluble pentosans retarded the extent of retrogradation by affecting both amylose and amylopectin. The rate of retrogradation of the starch-amylopectin gels containing water-soluble pentosans over the first day of storage was faster than the overall rate of retrogradation, indicating more crystallization of material over the first day of storage. The crystallization of starch gels was thus characterized by the retrogradation of amylose and amylopectin over the first day of storage; therafter, the amylopectin alone controlled the retrogradation process. Neither storage temperature nor pentosans caused changes in the basic mechanism of the retrogradation of starch gels upon aging, suggesting that pentosans influence the extent of the retrogradation simply by reducing the amount of starch components available for crystallization. The pasting properties of starch, starch-amylose, and starch-amylopectin slurries in the presence and absence of pentosans indicated that pentosans did not exhibit any effect on starch gelatinization. However, pentosans decreased the rate of setback. The effect of pentosans on the rate of setback of starch, starch-amylose, and starch-amylopectin gels was in good agreement with the effect of pentosans on the firming rate of starch gels.