Influence of germination and fermentation on bioaccessibility of zinc and iron from food grains

Abstract

Food grains such as green gram, chickpea and finger millet are often subjected to traditional processing involving germination and fermentation. This study was designed to assess the effect of germination of these grains on the bioaccessibility of zinc and iron. The effect of fermentation of a cereal-pulse combination as encountered in the preparation of breakfast dishes - idli, dosa and dhokla - on the same was also evaluated. Bioaccessibility measurement was made employing an in vitro simulated digestion method. Zinc bioaccessibility was significantly decreased by germination (48 h) of finger millet (38%) and green gram (44%), while iron bioaccessibility was increased by 62% (green gram), 39% (chickpea) and 20% (finger millet), concomitant with a reduction in tannin content. A fermented batter of rice+black gram - 2:1 (idli) and 3:1 (dosa) - had higher bioaccessibility values for zinc (71 and 50%, respectively), while iron bioaccessibility values were increased in these cases of fermentation to an even greater extent, namely 277 and 127%, respectively. Zinc and iron bioaccessibility was not improved by fermentation of the combination of chickpea, green gram, black gram and rice (1:1:0.5:0.5; dhokla). A fermentation of cereal-legume combinations of idli and dosa batter significantly reduced both phytate and tannin, while in the case of dhokla batter there was a continued significant presence of phytate associated with additional legumes - chickpea and green gram. Germination of food grains improved the bioaccessibility of iron but not that of zinc. Fermentation of a batter of cereal-pulse combination in the preparation of idli and dosa enhanced the bioaccessibility of both zinc and iron, but not that of the combination used for the preparation of dhokla.