Effect of germination on tannin,mineral, and trace element composition of groundnut varieties

Groundnut varieties were analyzed for their tannin, ionizable iron, soluble zinc, phytate phosphorus, total iron, total phosphorus, total zinc, copper, magnesium, and manganese contents in ungerminated seed and after 0, 24, 48, and 72 h of germination. Tannin content varied between 100 and 623 mg/100 g; ionizable iron ranged from 136–2178 µg/100 g; phytate phosphorus ranged from 415–655 mg/100 g; soluble zinc varied between 776 and 951 µg/100 g of kernels. Soaking groundnuts overnight in water resulted in a decrease in content of most of the minerals, trace elements, tannins, and soluble zinc. As the germination period increased from 0 to 24, 48, and 72 h, ionizable iron (50%) and soluble zinc (95%) increased substantially. Ionizable iron as percent of total iron increased from 10% in ungerminated kernels to 23% in 72-h germinated kernels. Soluble zinc as percent of total zinc also increased from 18% in ungerminated groundnuts to 31% in 72-h germinated ones. There was a negative correlation between tannin content and ionizable iron content of ungerminated and germinated kernels (r=?0.5203). Germination decreased the antinutritional factors, such as tannin, and increased the bioavailable forms of iron and zinc, namely ionizable iron and soluble zinc contents of groundnut kernels.