EFFECT OF GERMINATION TIME ON ANTI-NUTRIENTS AND PHYTOCHEMICAL PROPERTIES OF BLACK- EYED BEAN (Vigna Unguiculata)

Abstract

Vigna unguiculata (black- eyed bean) also known as cowpea, is a widely cultivated legume in Asia, Central and South America, and Africa. It is a staple food that provides human nutrition with large amounts of proteins, carbohydrates, dietary fibers, vitamins of the β complex, essential minerals, and a small quantity of lipids. High protein and carbohydrate contents with relatively low-fat and a complementary amino acid pattern to cereal grains make black- eyed bean an essential nutritional food in the human diet. The main aim of this research work was to determine the effect of germination time on black- eyed bean’s anti nutritional and phytochemical properties. Black-eyed was bought from the local market of Dharan, Nepal and then cleaned and steeped in water for 12 hours at 28 ± 3ºC, followed by draining and germination for consecutive 5 days at ambient temperature (28 ± 3℃, 90% RH). Then, the germinated legumes were dried in a cabinet dryer at 50 ± 5ºC for 16-18 hours, and dried samples were then taken for quantitative analysis of different components (protein, tannin, phytate, oxalate, flavonoid, total phenolic content and DPPH radical scavenging activity). The mean value of proximate composition of Black- eyed bean were found to be 27.0%, 0.86%, 3.41%, 4.42% and 64.25% on dry weight basis for protein, fat, ash, fiber and carbohydrate content respectively. The mean value of phytate, oxalate, flavonoid and tannin content in raw Black- eyed bean were found to be 819.8 mg/100g, 170.54 mg/100 g, 105.56 mg/100 g, and 199.9 mg/100 g based on dry weight respectively. Germination time showed significant reduction (p< 0.05) in phytate, tannin and flavonoid content of black- eyed bean for consecutive five days of germination. Germination time also showed a significant reduction (p< 0.05) in oxalate content in the first 3 days of germination, but there was no significant difference in oxalate content of black- eyed bean in third, fourth and fifth days of germination. Significant reduction (p<0.05) of TPC in black- eyed bean i.e., by 72.26 % was also found after consecutive five days of germination i.e., from 732.2 mg GAE/100g to 203.1 mg GAE /100g based on dry matter. The increase in germination time from day 1 to day 5 of black- eyed bean showed a significant increase (p< 0.05) in protein content from 27.03 to 39.54%. Germination time also showed significant increment (p<0.05) in DPPH radical scavenging activity of black-eyed bean i.e., from 41.6% to 74.55% respectively. Hence, germination was considered an effective method for reducing antinutritional factors and increasing the antioxidant and nutritional properties.