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Effect of Lactic Acid on Protein Solubilization and Starch Yield in Corn Wet-Mill Steeping: A Study of Hybrid Effects

¹Research Chemist, USDA, ARS, Southern Regional Research Center, 1100 Robert Lee Blvd., New Orleans, LA 70124. E-mail: odailey@srrc.ars.usda.gov Phone: 504-286-4514. Fax: 504-286-4367. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.

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.