Broad bean and pea by-products as sources of fibre-rich ingredients: potential antioxidant activity measured in vitro.

ABSTRACT

BACKGROUND: By-products generated during the processing of plant food can be considered a promising source of dietary fibre as a functional compound. The dietary fibre composition, soluble sugars and antioxidant activity of the extractable polyphenols of pea and broad bean by-products have been analysed in this study. RESULTS: Total dietary fibre using AOAC methods plus hydrolysis (broad bean pod 337.3 g kg⁻¹; pea pod 472.6 g kg⁻¹) is higher (P < 0.05) in both by-products than with the Englyst method (broad bean pod 309.7 g kg⁻¹; pea pod 434.6 g kg⁻¹). The main monomers are uronic acids, glucose, arabinose and galactose in broad bean pods. However, pea pods are very rich in glucose and xylose. The soluble sugars analysed by high-performance liquid chromatography in both by-products have glucose as the most important component, followed by sucrose and fructose. The ferric reducing antioxidant power (broad bean pod 406.4 µmol Trolox equivalents g⁻¹; pea pod 25.9 µmol Trolox equivalents g⁻¹) and scavenging effect on 2,2-diphenyl-1-picrylhydrazyl radical (EC50 of broad bean pod 0.4 mg mL⁻¹; EC50 of pea pod 16.0 mg mL⁻¹) were also measured. CONCLUSIONS: Broad bean and pea by-products are very rich in dietary fibre, particularly insoluble dietary fibre and their extractable polyphenols demonstrate antioxidant activity. Therefore they might be regarded as functional ingredients.