Dietary fibre profiling of various edible parts of winged bean (Psophocarpus tetragonolobus L.): Pods, whole seeds, endosperms, seed coats, and cooked seeds

Abstract

This study aimed to identify the dietary fibre profiles of various winged bean components (green pods, whole seeds, endosperms, seed coats, and canned whole seeds). Soluble dietary fibre (SDF), insoluble dietary fibre (IDF) (hemicellulose, cellulose, and lignin), total dietary fibre (TDF), and oligosaccharide components (raffinose, stachyose, and verbascose), were analyzed. The various winged bean components had a higher IDF content than SDF content (21.12–50.11% and 0.83–1.25%, respectively), with the highest TDF content observed in the seed coat (51.81%). Raffinose was the most dominant oligosaccharide component in green pods (2.7 mg/g), while verbascose was the most dominant component in all seed form samples, including seed coats (1.41–3.65 mg/g). The IDF in all samples was dominated by cellulose (5.07–39.34%), followed by hemicellulose (1.5–27.19%), and lignin (0.09–0.98%). Seed dehusking led to significant decreases in all types of dietary fibre analyzed, except for stachyose. Soaking and sterilization processes resulted in an increase in SDF, but decreased IDF, stachyose, verbascose, and hemicellulose compared to raw whole seeds. Principal component analysis (PCA) revealed that raw whole seeds still exhibit similarities in dietary fibre composition with canned seeds, but differ from green pods, endosperms, and seed coats. These findings imply that all edible parts of winged beans offer a large quantity of dietary fibre, especially whole seeds, which have potential benefits as prebiotic sources to improve health.