Exploration of microwaves for biorefining of phenolic antioxidants from Citrus reticulata peels: Spectrophotometric and spectroscopic analyses

Abstract

Citrus industries discard an enormous waste as a by-product during juice processing, which is attracting researchers due to its functional/nutraceutical properties. To utilize the functional potential of kinnow peels, bioactives have been extracted using several green extraction techniques. In the present research, the microwave-assisted technique has been used to extract bioactive phytochemicals (phenolic and total antioxidants) from kinnow peels. Process variables, such as microwave power, solvent concentration, liquid to solid ratio (LSR), and time, were studied to maximize the extract yield of phenolic and antioxidant compounds from kinnow peels. Maximum phenolic content (2.48 mg GAE/g peels) with antioxidant activity of 63.20% and 6.38 mmol Fe2+/100 g peels for DPPH and FRAP assays, respectively, was observed at 300 W, 80% ethanol, and LSR of 50 ml/g after 6 min extraction time. The presence of phenolic and antioxidant compounds was confirmed by FT-IR and GC-EI MS techniques. Novelty impact statement Microwave-assisted extraction has emerged as an efficient non-contact heating extraction technique. But there is inadequate data on the valorization of kinnow processing by-products using microwave-assisted extraction. The present research has been conducted to investigate the effect of process parameters of microwave-assisted technique on the extraction of phenolic and antioxidant compounds from kinnow peels. This study could encourage the scale-up process for the value addition of agro-industrial waste by efficient extraction of bioactive compounds from citrus processing by-products.