Green extraction of pectin from apple pomace using ultrasound-assisted deep eutectic solvents: Process optimization,...

This study explores the valorization of apple pomace (AP), a byproduct rich in pectin, yet often underutilized, by introducing a novel extraction technique that synergizes ultrasound assistance with deep eutectic solvents (UAE-DES). Through the application of response surface methodology (RSM), the study systematically optimized the process to enhance both the yield and functional attributes of the extracted pectin. The UAE-DES method demonstrated exceptional synergy, achieving a pectin yield of 25.06%, which markedly exceeded the yields from traditional DES (12.85%) and aqueous extraction methods (10.38%). Notably, the DES maintained its efficacy over four recycling cycles, sustaining a significant yield of 15.82%, underscoring its potential for sustainable applications. Furthermore, this environmentally friendly method uniquely altered the characteristics of pectin, resulting in a low molecular weight (142 kDa), a high degree of esterification (95.59%), and an increased galactose content (18.01 mol%). Structural analyses, including FTIR and SEM, confirmed the distinct modifications induced by the UAE-DES treatment. These structural changes directly contributed to enhanced functional performance, as evidenced by pronounced shear-thinning behavior, strong gelation capacity (G' > G" at 3% w/v), and significant antioxidant activity. This research demonstrates that UAE-DES is not just as an alternative extraction method, but as a powerful tool for producing high-value, functionality-specific pectin from apple by-products, emphasizing its dual benefits in sustainability and product quality.