Effect of heat treatment on the industrial quality of two varieties of Mexican wheat

Two Mexican wheat varieties conditioned to three initial moisture levels (1 7, 25 and 37% dry basis) were dried with air at 40, 60, 80 and 100 degreesC for 60 min periods in a laboratory scale fluidised bed system. Drying kine tics and activation energy was determined. Weight per hectolitre, wheat har dness, total protein content, dough mixing time and loaf volume were analys ed. The results showed that the initial moisture content and drying velocit y lowered the activation energy necessary to extract water from the grain. The effect of temperature and moisture content in the grain were the most i mportant factors to control damage during drying. The hard wheat variety wa s less susceptible to heat damage than the soft variety, probably due to it s higher protein content and harder texture. Weight per hectolitre. wheat h ardness and drying did not considerably modify total protein content. Conve rsely, mixing time and loaf volume showed changes directly related to heat treatment severity. Fluidised bed drying at 40 and 60 degreesC of both vari eties at 17% initial moisture content showed an improving effect on loaf vo lume.