Recovering antioxidant compounds from the juçara residue by a green approach

Juçara (Euterpe edulis) is a native palm from the Brazilian Atlantic Forest that produces phenolic-rich fruits. The fruits are used to obtain pulp, a functional ingredient employed in food preparations. However, for some purposes, juçara pulp needs to be refined, giving rise to a residue rich in antioxidant compounds and lipids. Thus, the objective of this work was to evaluate glycerol as green solvent in the microwave-assisted solid-liquid extraction of antioxidant compounds from juçara residue, as glycerol can be directly employed in food and cosmetic formulations because it is a substance generally recognized as safe. For that, an experimental design varying the glycerol concentration (0-100%), microwave exposure time (2-18 min) and temperature (53-187 °C) was adopted. The total phenolic compounds (TPC) and antioxidant capacity by DPPH^• were evaluated as responses. It was observed that the independent variables influenced the evaluated responses, mainly glycerol concentration and temperature (p<0.05). The TPC ranged from 1052 to 5329 mg GAE/100 g and antioxidant capacity from 29 to 191 µmol Trolox/g. The highest values were found at 187 °C, 50% glycerol for 10 min. All models were significant as the calculated F-values (117 and 38 for TPC and DPPH^•, respectively) were higher than the listed F-value (F_9,7=3.68) at α=0.05. Also, it was not observed lack of fit for those responses. The R² values of the models were higher than 0.98, accounting for, at least, 98% of data variability. Thus, using glycerol as a green solvent coupled with microwave-assisted extraction favored the recovery of antioxidant compounds from the juçara residue, presenting itself as a sustainable approach for adding value to the fruit production chain.