Total phosphorus, phytate phosphorus contents and the correlation of phytates with amylose in selected edible beans in Sri Lanka

Abstract

Phytate a major anti nutritional factors in legumes and it accounts for larger portion of the total phosphorus, while limiting the bioavailablity of certain divalent cations to the human body. Legumes of eleven varieties cultivated in Sri Lanka, Mung bean (MI5, MI6), Cowpea (Waruni, MICP1, Bombay, Dhawala, ANKCP1), Soybean (MISB1, Pb1) and Horse gram (ANKBlack, ANKBrown) were analyzed for phosphorus content and phytate content. Total phosphorus content was quantified by dry ashing followed by spectrophotometrical measurement of the blue colour intensity of acid soluble phosphate with sodium molybdate in the presence of ascorbic acid while phytate phosphorus using anion exchange chromatographic technique followed by spectrometrical measurement of the digested organic phosphorus and amylose content by Simple Iodine-Colourimetric method. Where the least value for phosphorus was observed 275.04 ±1.44 mg.100g-1 in ANKBlack (Horse gram) and the highest in MISB1 (Soyabean) with 654.94 ±0.05 mg.100g-1. The phytate phosphorus content (which is a ratio of phyate to total phosphorus) was highest in Dhawala (Cowpea). The phytate phosphorus (which is a ratio of phyate to total phosphorus) was highest in Dhawala with 67.42% and least in Bombay (Cowpea) with 24.87%. The amylose content of the legumes was least in Pb1 with 8.71 ±0.13 mg.100mg-1 and the highest in MI6 22.58 ±0.71 mg.100mg-1. The correlation between phyate and total phosphorus was significant (p <0.05) and positive (r = 0.62). Similarly the correlation coefficient for phytate phosphorus and total phosphorus was significant (p <0.05) and positive (r = 0.63). Amylose content of legumes was significantly correlated negatively (p <0.05) with the total phytates content (r = -0.82).