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.