Drying kinetics of hydrated and gelatinized corn starches in the presence of sucrose and sodium chloride

Drying behavior of the hydrated corn starch, hydrated starch/sucrose, and h ydrated starch/sodium chloride mixture and their gels were investigated. Dr ying data were obtained on slabs of samples in a laboratory tunnel dryer at 40 to 70 degrees C. The rate-of-drying curves for hydrated starches with o r without sucrose showed that the moisture movement may be the result of ca pillary action rather than diffusion. In the hydrated starches containing s odium chloride, case-hardening was the controlling mechanism. In gelatinize d samples, however, diffusion was the main mechanism. The effective diffusi vity was estimated by the methods of slopes. Gelatinization of starch reduc ed the moisture diffusivity significantly. The presence of sucrose or sodiu m chloride decreased the coefficient significantly in hydrated starch, but their effect was small in gelatinized samples.