The tannin content of a number of foods and diets commonly consumed in India has been determined. Most of the tannin in legumes resides in the seed‐coat. Decortication of seeds reduced tannin to a low level with a significant increase in ionisable iron. Germination of the legumes also resulted in a decrease in tannin and an increase in ionisable iron. Diets consumed in different parts of the country had tannin contents ranging from 1.5 to 2.5 g. Much of this appeared to be contributed by spices. A high level of tannin in these foods is associated with low ionisable iron. It is suggested that besides phytates, tannin may be an important factor responsible for the low absorption of iron from habitual diets in India.
Effect of simple domestic processing on ionisable iron from cereals and legumes was investigated using an in vitro method. Two-fold increase was observed when legumes and cereal were germinated for different periods. In the case of legumes, increase was observed only with the whole grain, whereas no such changes were observed with decorticated legume. The ionisable iron from bread was higher (nearly twice) when compared with that from chapathi, prepared from the same wheat. The total iron was higher in the parboiled rice than in the raw rice. The percentage ionisable iron was lower in the parboiled rice than in the raw rice. The actual amount of ionisable iron, however, was the same in both the rice samples. Fermentation of rice and legume (pulse) mixture and cooking did not result in any change in the ionisable iron. Cooking of rice or wheat as used in Indian homes did not influence ionisable iron.
An in vitro method for the determination of availability of nonheme iron from foods and diets was investigated. Food was extracted with pepsin-HCl at pH 1.35 and subsequently the pH was adjusted to pH 7.5 and filtered. Ionizable iron was determined in the pH 7.5 filterate by the alpha, alpha-dipyridyl method. The percent iron absorption from the same diets observed in the adult males. Ionizable iron at pH 7.5 was shown to increase in presence of ascorbic acid and meat extract while it decreased in presence of phytate and tannins, similar to the effects of these factors on iron absorption in human subjects. Based on these observations it is proposed that ionizable iron at pH 7.5 determined as described in this study can be used as a reliable measure of bioavailability of nonheme iron in foods.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.