Highly clean recovery of natural antioxidants from lemon peels: Lactic acid‐based automatic solvent extraction
Gizem Toprakçı, İrem Toprakçı, Selin Şahin
Abstract
INTRODUCTION: Food industry generates large amounts of waste by-products rich in natural antioxidants. On the other hand, application of advanced processes for the recovery of these fine chemicals is another popular topic of recent years. OBJECTIVE: The purpose of this study is to propose a green extraction method by application of deep eutectic solvent-based automated solvent extraction (AMSE) from lemon peels. METHODS: The primary polyphenols (hesperidin, naringin, and p-coumaric acid) and the total polyphenols of the lemon peel extract were quantified and used as response for the optimisation of the AMSE conditions. The Box-Behnken design type of the response surface method (RSM) was chosen for optimisation study. Scavenging activity of the lemon peel extract against 2,2-diphenyl-1-picrylhydrazil (DPPH) free radical was also measured in vitro. RESULTS: The optimum conditions for the highest total phenolic (7.47 mg-gallic acid equivalent [GAE]/g-lemon peel [LP]), naringin (5.05 mg/g-LP), p-coumaric acid (3.27 mg/g-LP), and hesperidin (0.07 mg/g-LP) yields were obtained by 1.5 h of extraction time, 46% water (v/v), and 5 g of peel. The antioxidant activity changed between 37.31% and 94.10% in the peels. CONCLUSIONS: Extraction time was the most effective process factor for the total phenolic and p-coumaric acid yields, while water addition was statistically very important (p < 0.0001) for the naringin and hesperidin yields in the current AMSE system. The second-order models generated for the selected systems represent the data satisfyingly based on the high coefficients of determination (> 0.99), statistically significant p-values (<0.0001), coefficient of variation values (< 10%), and non-significant lack-of-fit values (p > 0.05).