Microwave-Assisted Extraction of Pectin from Pickled Cabbage Waste: Process Optimisation, Characterisation and Application in Low-Sugar Jam

This study optimised pectin extraction from pickled cabbage waste using microwave-assisted extraction (MAE), characterised the extracted pectin, and explored its potential for low-sugar jam production. The Box–Behnken design concluded that the optimal conditions are 539 W (microwave power), 116 s (time), and pH 1.5, yielding a pectin yield of 22.53 ± 2.63%. The physicochemical analysis revealed that the microwave-extracted pectin (MEP) was low methoxyl and had a high molecular weight (1.20 ± 0.004 MDa). It was composed of galacturonic acid, arabinose, rhamnose, xylose and glucose. FTIR, 1H NMR and SEM results also confirmed structural characteristics of MEP. MEP was confirmed to have remarkable technological properties, including an emulsion activity of 53.43 ± 2.19% and good stability over 30 days at 4 °C and 24 °C. Moreover, it has an oil-holding capacity of 1.18 ± 0.51 g oil/g pectin and an elevated water-holding capacity (9.36 ± 3.25 g water/g pectin). The application of MEP as a stabiliser in low-sugar jam enhanced viscoelastic characteristics of jam, like apple pectin, and G′ > G″ confirmed the improved shelf-life stability at 25 °C. This study emphasised that microwave-assisted extraction can be a sustainable, time- and energy-saving method for the valorisation of pickled cabbage waste, and highlighted the effect of MEP on the characteristics of low-sugar jam.