Abstract: An enzymatic hydrolysis method was proposed to extract phenolic components from distiller’s grains. The extraction process was optimized by quadratic rotation-orthogonal composite experimental design method. The extraction yield of total phenolic acids was investigated with respect to variable parameters including enzyme dosage (X1), reaction time (X2), pH (X3) and material-to-liquid ratio (X4). A regression model was established as Y＝1.28321＋0.04783X1＋0.03728X2＋0.12048X3＋0.05152X4－0.05027X12＋0.01514X22＋0.00099X32－0.03790X42＋0.02000X1X2＋0.03000X1X3＋0.00250X1X4. The optimal extraction conditions were enzyme dosage 10 mL/100 g, pH 6.6, and material-to-liquid ratio 1:25, and hydrolysis time 150 min. Under these conditions, the predicted and actual yields of total phenolic acids were 1.50% and 1.51%, showing a relative error of 0.67%. HPLC analysis indicated that an obvious increase of tran-ferulic acid after enzymatic hydrolysis was observed.

Key words: distiller, s grains, phenolic acids, enzymatic hydrolysis, extraction, optimization