INTERACTIONS OF SULFUR-DIOXIDE, LACTIC-ACID, AND TEMPERATURE DURING SIMULATED CORN WET-MILLING

Response surface methodology was used to investigate the interactions of lactic acid, sulfur dioxide (SO2), and steeping temperature and the ir effects on corn wet milling yields. A regular dent coin hybrid and a more vitreous dent corn hybrid were laboratory batch steeped. Kernel absorption of SO2 was higher for the more vitreous dent corn hybrid. Absorption also increased with lactic acid use and at lower steeping t emperatures. Lactic acid concentrations in steepwater remained constan t over time, but kernels absorbed more steepwater at higher temperatur es. When wet milled on a laboratory scale, vitreous corn was more resi stant to grinding and less millable. Significant first-order response surface models of starch, germ, fines, gluten, and steep solids yields were predicted as functions with nonlinear influences of lactic acid and SO2. Higher starch yields were obtained when steeping at 43 degree s C than at 57 degrees C; higher yields were predicted with moderate l actic acid and high SO2 concentrations. Steeping temperature interacti ons with lactic acid and SO2 during the steeping period limited its in tegration as a second-order modeling factor for starch, germ, and fine s fractions. For all treatments, gluten recovery and steepwater solubl es responses were predicted by lactic acid concentrations. Lactic acid , which influenced all significant fraction yield models, affected SO2 absorption.