Distilled Spirit Extraction of Phenolic Antioxidants from Fruit and Vegetable Residues

Abstract

There is a growing interest in natural antioxidants due to their potential in improving the quality of food and cosmetic‎products and their health-promoting properties. Distilled spirits contain high amount of ethanol and may be‎an alternative to the food-grade solvents, while agricultural by-products contain phenolic substances that may have‎antioxidant properties. This study was therefore conducted to find out if gin, vodka, and tequila flavored spirit, alcoholic‎beverages with about 40% ethanol, can extract the phenolic compounds from agricultural by-products, and‎to determine if the extracts possess the antioxidant activity. Peels of ripe banana (Musa acuminata), ripe mango‎(Mangifera indica), calamansi (Citrofortunella microcarpa), squash (Cucurbita maxima), ripe pineapple (Ananas‎comosus), purple yam (Dioscorea alata), and sweet potato (Ipomea batatas) were collected, dried, and ground.‎The phenolic substances in the plant materials were extracted with alcoholic beverages or 40% ethanol. The total‎phenolic content (TPC) of the extracts was determined by means of UV-Vis spectroscopy using Folin-Ciocalteau‎reagent and gallic acid as reference compound. The antioxidant activity of the extracts was evaluated through the‎2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Butylated hydroxyanisole (BHA) served‎as positive control in the DPPH assay. Non-linear regression was applied to the DPPH assay data to estimate the‎values of median effective concentration (EC50). All three alcoholic beverages were able to extract the phenolic‎materials from the plant samples. However, the ability of vodka and gin to extract the phenolic substances was either‎statistically comparable or better than 40% ethanol. The results of the DPPH scavenging assay showed that the‎M. indica peel had the strongest activity, while C. microcarpa had the weakest scavenging activity. At 1000-ppm‎level, the antioxidant activity of the M. indica peel was comparable with that of BHA, regardless of the solvent‎used for extraction. Therefore, the M. indica peel can be a source of natural antioxidants and potential substitute to‎synthetic antioxidants. Both gin and vodka can be used as a substitute for food-compatible solvents.