Ra. Buffo et al., OPTIMIZATION OF SULFUR-DIOXIDE AND LACTIC-ACID STEEPING CONCENTRATIONS FOR WET-MILLING OF GRAIN-SORGHUM, Transactions of the ASAE, 40(6), 1997, pp. 1643-1648
Influence of sulfur dioxide (SO2) and lactic acid (LA) on grain sorghu
m steeping efficiency in terms of wet-milling characteristics was inve
stigated using response surface analysis. Tested ranges of concentrati
ons 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 re
covery values were highly correlated to each other (r = 0.74). Correla
tions of these attributes with fiber/germ yield were strongly negative
(r = -0.96 and r = -0.70 for starch and protein recover): respectivel
y). A model comprised of the linear and quadratic terms of SO2 and LA
concentrations and the interaction between SO2 and LA was fitted to da
ta for each dependent variable. The model satisfactorily explained sta
rch yield (R-2 = 0.84), starch recovery (R-2 = 0.65) and fiber/germ yi
eld (R-2 = 0.71). Lactic acid was the factor that consistently influen
ced all significant surfaces (P < 0.01 for starch yield and starch rec
overy, and P < 0.05 for fiber/germ yield). Maximum stationary points f
or 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.