Sustainable Approach for Utilization of Mango Peel Wastes for Pectin Extraction by Natural Deep Eutectic Solvents

Sequential ultrasound- and microwave-assisted natural deep eutectic solvents (NADES) were used for the extraction of pectin from mango peels in this study. The two different NADES composed of proline: malonic acid (Pro: MA) and choline chloride: tartaric acid (ChCl: TA) which resulted in higher pectin yield were selected for further optimization studies. The processing conditions such as sonication duration, microwave intensity, microwave processing duration, and liquid-solid ratio were optimized using Box-Behnken design. The optimized conditions are sonication duration (7.5 min), microwave intensity (40 W/g), microwave processing duration (5 min), and liquid-solid ratio (65%). The physicochemical and technofunctional properties of pectin extracted using NADES were compared with conventional acid-extracted pectin. The moisture and ash content of NADES-extracted pectin were within the specified limit provided by the International Pectin Producers Association. The NADES-based extracted pectin contains galacturonic acid content higher than 65%, as mentioned by the Joint FAO/WHO Expert Committee on Food Additives and the European Commission. The higher anhydrouronic acid content of pectin (88.8 +/- 0.21%-90.82 +/- 0.11%) represents the superior purity of pectin. The higher degree of esterification (> 50%) indicates the extracted pectin is a high ester pectin. The similarity of FT-IR spectra at 800-1300 cm(-1) with the "fingerprint zone" of carbohydrates indicates that extracted pectin is functional pectin. The results showed that ultrasound- and microwave-assisted NADES are efficient systems for extracting pectin with a high degree of esterification from mango peels.