Optimization of the extraction process for fermented Rhus verniciflua stokes using response surface methodology

Extraction conditions for extraction yield (Y 1 ), total phenolic content (TPC, Y 2 ), and inhibition rate in human gastric carcinoma cells (Y 3 ) were optimized using response surface methodology for fermented Rhus verniciflua stokes (FRV). Optimal extraction conditions for effective use of FRV as a biofunctional material in food and pharmaceutical industries were investigated. Independent variables were extraction temperature (X 1 =25-105°C), extraction time (X 2 =4-20 h), and the solvent to solid ratio (X 3 =10-30 mL/g). A second order polynomial model satisfactorily fitted experimental data with coefficient of determination (R 2 ) values of 0.9613, 0.9851, and 0.8038, respectively, for Y 1 , Y 2 , and Y 3 . Optimal conditions for the highest extraction yield of 2.37%, a total phenol content (TPC) value of 113.75 mg of tannic acid equivalents (TAE)/g, and an inhibition rate of 72.61% were derived at X 1 =89.95°C, X 2 =9.25 h, and X 3 =25 mL/g.