Effect of lactic acid on protein solubilization and starch yield in corn wet-mill steeping: A study of hybrid effects

To better understand the role of lactic acid (LA) in corn wet-milling, steeping studies were performed on different yellow dent corn hybrids using four different solutions containing LA, sulfur dioxide (SO2), a combination of LA and SO2, or no added chemicals, Although there was variation in protein solubilization among the hybrids, protein release was consistently higher when LA was included in the steepwater than when it was excluded (both with and without SO2),. Several groups have reported that starch recoveries are improved when steepwater contains LA. To explore the relationship between protein solubilization and starch yield as effected by LA, several yellow dent hybrids were steeped in 0.20% SO2 and 0.50% LA-0.20% SO2 solutions and milled to recover starch by a 100-g laboratory corn wet-milling procedure. In all instances, both starch yields and protein solubilization were enhanced in solutions containing LA. These results support the hypothesis that direct dissolution of the endosperm, protein matrix by LA contributes to the improved starch recoveries.