Application of response surface methodology for obtaining lettuce (Lactuca sativa L.) by-products extracts with high antioxidative properties

The main objective of the present work was to optimize the extraction conditions for simultaneous maximization of total reducing (TRC) and antioxidant (AC) capacities for lettuce (Lactuca sativa L.) by-products extracts, using response surface methodology. For this, a design of experiments (DOE) with different combinations of solvents (water, methanol and acetone) extraction temperatures (30–60 °C) and time (10–60 min) on the TRC and AC was applied. Higher and consistent fittings using second order polynomial models of the experimental data with regard to TRC (R2 = 0.529, plack of fit > 0.05) and AC (R2 = 0.900, plack of fit > 0.05) were obtained with methanol. The optimum extraction conditions based on combination responses for TRC and AC were: 30% methanol (v/v), 60 °C and 60 min. A close agreement between experimental and predicted values was found when applying these conditions. Furthermore, when aqueous extracts were prepared (e.g. 45 °C, 10 min), these presented similar TRC and AC properties to those obtained by the above optimum extraction conditions, having the advantage of applying mild extraction conditions and avoiding the use of organic solvents in their preparation.

► Fresh-cut lettuce products as ready-to-eat vegetables have been in great demand. ► However, in their preparation 50% of the collected material is rejected. ► These by-products can lead to extracts with biological activity. ► Extraction conditions were optimized by response surface methodology. ► Extracts with antioxidative properties were obtained.