Microwave-assisted deep eutectic solvent extraction of phenolic antioxidants from onion ( Allium cepa L.) peel: a Box–Behnken design approach for optimization

Abstract

Valorization of onion peel waste, considered to be a rich source of polyphenolic compounds, by employing green extraction techniques is the need of the hour. The aim of the present study was to optimize the microwave-assisted extraction of bioactive phenolic compounds from onion peel wastes employing ChCl:Urea:H ₂O deep eutectic solvent. Microwave power (100–200–300 W), time (5–15–25 min) and liquid to solid ratio (40:1–50:1–60:1) were studied as the major parameters affecting the extraction efficiency. A Box–Behnken design was adopted including 17 experiments with five centre points. The optimum conditions determined were 100 W microwave power, 15.03 min irradiation time and 54.97 mL g ⁻¹ liquid to solid ratio. Under the MAE optimized conditions, the recovery of TPC and FRAP were 80.45 (mg GAE g ⁻¹ dw) and 636.18 (µmol AAE g ⁻¹ dw), respectively. Morphology of onion peels before and after DES extraction were also studied to gain an insight in the effect of microwave irradiations on the biomass.

Electronic supplementary material

The online version of this article (10.1007/s13197-019-03891-7) contains supplementary material, which is available to authorized users.