Production of Dietary Fiber from Legume Processing Waste

Abstract

This study evaluated the isolation of dietary fibre from husks obtained after boiling cowpeas (Vigna unguiculata), white beans (Phaseolus vulgaris), and lentils (Lens culinaris) using homogenisation and control methods. Legumes were boiled until the husks separated and then soaked in cold water for husk removal. The moisture content of fresh husks ranged from 77.4% to 86%, while water activity (aw) values were between 0.95 and 0.96. Dietary fibre production using the homogenisation method was successful only for white beans, yielding 15.83 g of dietary fibre. Colour analysis showed that the dried white bean sample had the highest L* value (80.07), indicating the lightest colour, while cowpea and lentil samples exhibited lower and similar L* values. All samples had low a* values, reflecting greenish tones, whereas positive b* values indicated yellow hues, especially in lentils. Green lentils demonstrated the highest water-holding capacity (4.24 g/g), while cowpeas had the lowest (1.78 g/g). In contrast, cowpeas showed the highest oil-holding capacity (1.97 g/g), whereas lentils had the lowest (1.18 g/g). Total phenolic content varied significantly among samples: cowpeas had the highest value (78.52 mg GAE/100 g), followed by lentils (49.85 mg GAE/100 g), while white beans showed very low phenolic content (3.05 mg GAE/100 g). Principal component analysis (PCA) was applied to evaluate physicochemical properties. The PCA score plot revealed clear grouping of samples according to their characteristics. White bean samples differed from cowpea and lentil samples along principal component 1, while lentil samples were separated from the others along principal component 2.