Optimization of Sulfur Dioxide and Lactic Acid Steeping Concentrations for Wet-Milling of Grain Sorghum

Authors

R. A. Buffo, Department of Food Science & Technology
Curtis L. Weller, University of Nebraska-LincolnFollow
A. M. Parkhurst, University of Nebraska-LincolnFollow

Date of this Version

1997

Comments

Published in Transactions of the ASAE VOL. 40(6):1643-1648. Copyright © 1997 American Society of Agricultural Engineers. Used by permission.

Abstract

Influence of sulfur dioxide (SO₂) and lactic acid (LA) on grain sorghum steeping efficiency in terms of wet-milling characteristics was investigated using response surface analysis. Tested ranges of concentrations in steeping water were 0.050 to 0.278% and 0 to 0.282% for SO₂ and LA, respectively. Measured wet-milling variables were steeping solids yield, starch yield, protein yield, fiber/germ yield, starch recovery, protein recovery and protein content of starch. Starch and protein recovery values were highly correlated to each other (r = 0.74). Correlations of these attributes with fiber/germ yield were strongly negative (r = –0.96 and r = –0.70 for starch and protein recovery, respectively). A model comprised of the linear and quadratic terms of SO₂ and LA concentrations and the interaction between SO₂ and LA was fitted to data for each dependent variable. The model satisfactorily explained starch yield (R² = 0.84), starch recovery (R² = 0.85) and fiber/germ yield (R² = 0.71). Lactic acid was the factor that consistently influenced all significant surfaces (P < 0.01 for starch yield and starch recovery, and P < 0.05 for fiber/germ yield). Maximum stationary points for starch yield and recovery, and a minimum stationary point for fiber/germ yield were observed at similar combinations of SO₂ (0.191-0.209%) and LA (1.387-1.415%) concentrations.