Chemical characterization of winged bean (Psophocarpus tetragonolobus (L.) DC. seeds and safety evaluation of its fatty oil

Abstract

One of the reasons for “underutilization” of the tropical legume winged bean (Psophocarpus tetragonolobus (L.) DC.) is the presence of certain anti-nutrients in its seeds. This may be one of the impediments for the adoption and routine cultivation of this plant. The natural-variation of P. tetragonolobus manifests in its seed-coat colour. The present paper characterizes and evaluates the physico-chemical properties of the seed-oil extracted from white, light-brown, dark-brown seeds of P. tetragonolobus. The refined seed-oils of these lines are suitable and comparable with soybean seed-oil. Additionally, as compared to soybean oil, the oil of P. tetragonolobus is thermally stable due to the presence of saturated (21.2–22.7%), monounsaturated (39.3–40.2%) and polyunsaturated (37.0–38.2%) fatty acids. Variation in acid value (0.4 to 0.6 mg/g), free fatty acid (0.2–0.3%), saponification value (172.2–173.5 mg/g), iodine value (118.9–121.5 g/100 g), refractive index (1.44–1.48) and density (0.91–0.92) was reported upon analysis. Safety evaluation of this refined oil on 4-weeks feeding trial on albino mice revealed non-significant changes in terms of body weight, organ weight, haematological and serum biochemical changes. Furthermore, the seed-cake of P. tetragonolobus contained proteins to a range of (34.7–35.6%), carbohydrates (21.4–23.1%), polyphenols (0.45–0.49%), L-DOPA (0.35–0.38%) and phytic acid (0.18–0.2%). These values are closely comparable with the soybean seed-cake.