Effect of chemical pretreatments and lactic acid on the rate of water absorption and starch yield in corn wet-milling

The relative effectiveness of dehulling, potassium hydroxide dipping (alkal i concentrations 0.2, 05, and 1.0 %), and ethyl oleate spraying (aqueous em ulsion 1%, v/v) to increase the rate of water absorption by dent and flint corn during steeping was compared with untreated corn samples. These pretre atments increased the water absorption rate of both hybrids when compared w ith the untreated control samples. To evaluate the observed increase, the d iffusion coefficients of pretreated and untreated corn samples were estimat ed. Corn grains steeped in SO? aqueous solution and variable lactic acid co ncentrations (0.2, 0.5, and 1.0%, v/v) were performed. Absorption rates for lactic acid concentrations were approximate to 0.5% higher than those stee ped only in SO2 solution. This effect was more marked for dent than for fli nt corn. Corn samples pretreated with potassium hydroxide had lower starch yields than the control. However, the presence of lactic acid in steepwater increased the starch yield of dent and flint corn, particularly for the sa mples treated with alkaline solution. This procedure was particularly benef icial for flint corn. An effective release of the starch granules was achie ved within 24 hr of steeping.