Batch steeping of corn: Effects of adding lactic acid and sulfur dioxide at different times on starch yields, protein contents, and starch pasting properties

The effect of adding lactic acid and sulfur dioxide at different times from the start of batch steeping on corn starch yields was studied. Five commer cial hybrids were steeped with 0.5% lactic acid or 0.2% sulfur dioxide adde d over the first 15 hr of steeping and wet-milled following a 100-g corn we t-milling procedure. No significant differences were observed In starch yie lds when lactic acid was added to the steep solution (SO2 and water) from 0 hr (start of steeping) to 15 hr. Addition of SO2 to the steep solution (la ctic acid and water) resulted in significantly higher average starch yields when SO2 was added between 5 and 15 hr compared with addition at 0 ht (SO2 and lactic acid for full 24 hr of steeping). Based on the results of the f irst experiment, a second experiment was done in which one of five original hybrids was steeped for 24 hr, during which lactic acid or SO2 was added u ntil 23.9 hr (i.e., 5 min before milling) after the start of steeping. Simi lar results were found in the second experiment. Residual protein in starch samples did not exceed 0.85%. Steep-water protein content decreased with d elays (16-20 hr) in adding either chemical to the steep solution. A signifi cant effect on starch pasting: properties of chemicals and duration of chem icals in steepwater was observed. Testing these findings using a larger sca le (1,000 g) corn wet-milling procedure produced results similar to those o btained with the 100-g corn wet-milling procedure.