Sustainable utilization of fruit and vegetable waste for the extraction of phenolics, antioxidants, and other valuables

This work portrays a sustainable utilization of fruits and vegetable waste (FVW) and aims in extraction of valuables. The waste chosen for the study are papaya peel, pea pod, mustard oil cake, banana peel, orange peel, pomegranate peel, pineapple peel, used coffee bean, onion peel, and apple peel. The extraction of bioactive components was done with methanol by percolation method at room temperature. The extraction was also done using microwave extractor and bath ultrasonicator. The extracts were analyzed for total phenolic content (TPC) using Folin-Ciocalteu method in terms of mg/ml of gallic acid equivalents (GAE). Total phenolic content was found to be highest in apple peels (0.171 mg/ml), papaya peels (0.166 mg/ml), onion peel (0.146 mg/ml), and pomegranate (0.126 mg/ml). The extracts were analyzed for their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC) assays. Pomegranate peel showed 51.05% degradation in comparison to pure ascorbic acid which is a super antioxidant showing 90% degradation of DPPH (0.2 mM). Total protein content was determined by Biuret method. Anthrone reagent was used to determine the amount of carbohydrate in each sample quantitatively. The results underscore the immense potential for sustainability and innovation within the domain of food waste utilization for extraction of valuables.

Graphical Abstract