Physicochemical and functional properties of pulp and pectin from agro-waste of three Cucurbitaceae species

Cucurbita pepo L., Citrullus lanatus T. and Cucumis melo L. belong to the family Cucurbitaceae and are cultivated for their seeds. The fruit pulp and peel are discarded as agro-waste after seed removal. This study evaluated the physicochemical and functional properties of the pulp and pectin extracts from the Cucurbitaceae species. Proximate, antioxidant, total polyphenol and flavonoid contents were determined. The purity, structural and sugar constituents of the extracted pectin were analysed using spectrophotometric techniques (NMR, FTIR and LCMS). Results showed that the pulp wastes had high carbohydrate content (28.4 to 69.7%) and demonstrated high antioxidant activities (40 to 50%, 63 to 85% and 0.2 to 0.4 mg mL−1 for DPPH, ABTS and FRAP respectively). Cucurbita pepo L. had the highest pectin yield (13.9%), and the purity of the pectin extracts ranged from 60.4 to 75.2% for total carbohydrate and 3.3 to 4.4 % for protein. The pectin extracts showed structural similarities. LCMS fingerprints of the pectin extracts showed that the monosaccharides comprised of mannose, rhamnose, galacturonic acid, glucose, galactose, xylose, arabinose and fucose. The polymers demonstrated high water absorption capacities (309 g/100 g to 604 g/100 g) and can be applied as thickeners in food systems.