Optimization of phenolics extraction from sesame seed cake

Sesame seed cake is considered to be a by-product of the oil industry, being commonly used as cattle feed in several producing countries. However, this residue can be recovered and value added. The main phenolics found in sesame seed are lignans, which are important bioactive compounds of this seed. The main lignans in defatted sesame were identified as sesaminol triglucoside, sesamolinol diglucoside and sesaminol diglucoside. The objective of this study was to optimize the extraction of total phenolics and lignans from sesame seed cake. A second-order polynomial model was set up to predict the responses using response surface methodology (RSM). The independent variables analyzed were temperature (25-90 °C), solid/solvent ratio (0.03-0.11 g/mL) and ethanol concentration (0-95%). Response variables were the concentrations of total phenolics (TP), sesamin (SES), sesaminol triglucoside (ST) and antioxidant activity (ABTS). The extracted amount of TP ranged between 129.7 and 355.3 mg GAE/100 g, SES from 3.2 to 25.7 mg SES/100 g, ST from 208.1 to 537.5 mg SE/100 g and the ABTS of the extracts was between 8460 and 24311 μM TE. Among the analyzed compounds, ST is presented in the highest quantity in sesame cake. Solid to liquid ratio and ethanol concentration were the most important factors affecting extraction, whereas temperature showed reduced influence. The model obtained to describe the effect of these factors on the extraction of ST was satisfactorily validated.