Unlocking value from waste: a comparative study of orange peel extraction methods using choline chloride-based natural deep eutectic solvents

Abstract

Green chemistry is a fundamental aspect of the food industry in the extraction of bioactive compounds from plant byproducts, through the utilization of sustainable methodologies, such as ultrasound-assisted extraction (UAE), enhancing food safety. Conventional solvents are being replaced by green alternatives, including natural deep eutectic solvents (NADES), which are nontoxic and biodegradable. The objective of this study is to compare UAE with heating-stirring (HS) methods for the extraction of bioactive compounds from orange peels using NADES. The antioxidant capacity (AC) of the extracts will be compared by three methods [oxygen radical absorbance capacity (ORAC), DPPH, and ferric ion reducing antioxidant power (FRAP)], also the phenolic profile will be studied, and the stability of the extracted compounds will also be assessed. The AC results demonstrated that UAE yielded higher than HS with ChChl/Fruc and ChChl/LA. The FRAP revealed differences among NADES, with ChChl/LP/MA exhibiting the highest. ORAC method identified ChChl/LP/MA and ChChl/LA as the most efficient. The UAE showed higher extraction yield compared to HS, particularly for caffeic acid and hesperidin, where ChChl/Fruc and ChChl/LA where the best NADES. Concerning stability, HS yielded a more stable AC than UAE, except ChChl/Fruc. UAE demonstrated superior stability for phenolic compounds in ChChl/LP/MA and ChChl/Gly, whereas HS showed greater efficacy for ChChl/LA. In conclusion, the selection of extraction methods and solvents has a impact on the yield, stability, and AC of bioactive compounds. It is evident that the selection of NADES and extraction methods should be tailored to achieve an optimal balance between yield, AC, and long-term stability of the bioactive compounds.