Antioxidant Potential, Antinutrients, Mineral Composition and FTIR Spectra of Legumes Fermented with Rhizopus oligosporus

Abstract

Research background. Legumes are superior sources of macro- and micronutrients which can be further enhanced by fermentation. This can assist in addressing the food security concerns. The present study aims to determine the effect of fermentation by Rhizopus oligosporus on nutritional and antinutritional composition of some commonly consumed legumes. Experimental approach. Chickpea (kabuli and desi), pigeon pea and soybean were fermented with Rhizopus oligosporus (at 34 °C for 52 h), dried at 45 °C for 16–18 h and milled. Antioxidant potential, phenolic composition, antinutrients, mineral composition and FTIR spectra of fermented and unfermented flour samples were evaluated. Results and conclusions. Fermentation significantly (p<0.05) enhanced the total phenolic and flavonoid contents, and antioxidant properties (radical scavenging activity, reducing power, ferric reducing antioxidant power and metal chelation) of kabuli and desi chickpeas, and soybean. Although fermented pigeon pea exhibited excellent antioxidant properties, the effect of fermentation on such properties was either minimal or insignificant. Additionally, quantification of specific phenolics using HPLC showed higher mass fractions of certain compounds such as chlorogenic, p-hydroxybenzoic, gallic and vanillic acids in fermented legumes. Mass fraction of phytic acid in all the fermented legumes was reduced (p<0.05), while trypsin inhibition increased (p<0.05). In kabuli and desi chickpeas, and pigeon pea, saponin mass fraction increased (p<0.05) while it decreased in soybean. Tannin mass fraction increased (p<0.05) in desi chickpea, pigeon pea and soybean and decreased (p<0.05) in kabuli chickpea. Furthermore, fermentation enhanced the content and estimated bioavailability of minerals. FTIR spectrum of fermented and unfermented legumes showed the presence of several functional groups and modifications in the molecular structure after fermentation. Novelty and scientific contribution. To our knowledge, this is the first study where legume (kabuli and desi chickpeas, pigeon pea and soybean) fermentation by Rhizopus oligosporus has been assessed for nutritional and antinutritional profile and FTIR spectra. We concluded that the treatment resulted in an optimal balance of nutrients and antinutrients. The process proved to be a potential tool for tackling the concerns of nutritional security, and thus can be proposed for the development of novel legume-based functional foods.