Physicochemical and functional properties of dietary fiber-rich by-products from different pulses: a comparative study

Pulse hulls, the primary by-product of pulse processing, are increasingly being recognized as promising sources of dietary fiber, yet their nutritional composition and functional properties remain underexplored. This study comparatively investigated the proximate composition, physicochemical and functional properties, and antioxidant activities of pulse hulls from six commonly consumed pulses: chickpea, red lentil, yellow pea, cowpea, black bean, and faba bean. All the studied samples were rich in dietary fiber (49.11 – 65.43%), while low in protein (3.94 – 13.91%), ash (2.23 – 5.03%), and fat (0 – 0.71%). Scanning electron microscopy revealed distinct surface morphologies across samples. Variations in compositional profiles and microstructures resulted in versatile functional properties. Chickpea hull displayed the highest water holding (5.91 g/g), oil holding (1.48 g/g), and swelling (4.17 mL/g) capacities; red lentil hull exhibited the highest glucose adsorption (308.01 mg/g) and exceptional cholesterol binding (135.19 mg/g) capacities, while cowpea hull exerted the greatest sodium cholate binding capacity (29.89 mg/g). Colored hulls (red lentil, faba bean, black bean, cowpea) demonstrated significantly higher total phenolic content (8.54 – 35.70 mg gallic acid equivalent (GAE)/g) compared to the light-colored chickpea and yellow pea hulls (< 1 mg GAE/g), with red lentil hull showing the highest value. Antioxidant activities assessed by DPPH, NO, and ORAC assays positively correlated with phenolic content (r = 0.992, 0.906, and 0.936, respectively, p < 0.05). These findings highlight the potential applicability of pulse hulls as antioxidant and fiber-rich ingredients for functional food applications.