EFFECT OF PARTICLE SIZE ON THE WATER SORPTION PROPERTIES OF CEREAL FIBERS1

Abstract

AbstractSix particle size fractions were prepared by grinding and sieving stabilized hard red wheat bran, oat fiber, and corn bran. Water adsorption indices (WAI's) and effective diffusion coefficients (Deff) were measured for all size fractions. WAI's of wheat bran decreased with particle size. WAI's of oat bran increased as particle size decreased and the WAI's of corn bran fractions did not vary as much as the other fibers. The Deff's of wheat increased, of oat decreased, and of corn were about the same as the particle size decreased. The wheat Deff was less than that of corn which was less than that of oats. Monolayer moisture content and bulk moisture content at high Aw were determined from moisture sorption isotherms measured on the smallest particles. There was no difference in the monolayer moistures but both corn and wheat brans adsorbed much more water at high Aw than did the oat bran. Effect of particle size on water sorption and, by inference, some types of functionality cannot be generalized and must be determined for each type of fiber.