Optimization of Selected Parameters Influencing the Total Phenolic Content Determination of Sesame Oil

Abstract

Antioxidant activity of sesame {Sesamum indicum L.) oil can be assessed by determining its total phenolic content (TPC) using Folin-Ciocalteu reagent (FCR) method. Objective of this study was to optimize V, volume of FCR, C, concentration of sodium carbonate (SC) solution and t, incubation time, used for the determination of TPC of sesame oil since a standard method is not available for the said purpose. Methanol-water (80:20 v/v) extracts of freshly produced sekku-based sesame oil was used. TPC procedure adopted was as follows: 1 ml of the said extract was diluted with 5 ml of distilled water; V ml of FCR and 2 ml of C g/100 ml of SC solution were added; mixture was diluted with 1.5 ml distilled water and vortexed at 1600 rpm for 30 seconds; kept in dark for t h. Absorbance at 765 nm was measured using a UV-VIS Spectrophotometer (DR 6000™, HACH). Optimization of the parameters were carried out using a full factorial design of experiment with V = 0.5, 1.0 and 1.5 and C = 7.5, 10 and 20. Contour plot obtained with the resulting regression model featured a saddle point in the area enclosed by V ^ 1.0 to 1.5 and C ^ 15 to 20 for all t studied, and therefore this area shall be avoided in the TPC determination of sesame oil. Optimum values of V, C and t. suggested by the results of this study are 0.5 ml, 20 g/100 ml, and 1.5 h.