Tannins in Foods: Nutritional Implications and Processing Effects of Hydrothermal Techniques on Underutilized Hard-to-Cook Legume Seeds-A Review

Abstract

Tannins, water-soluble phenolic compounds, have been reported to have the ability to form complexes with nutritionally important nutrients such as protein and mineral elements thereby making them unavailable for absorption and utilization. Toxicity of tannin has been demonstrated in experimental animals although no deleterious effect of ingestion of legume tannin on human physiology has been reported. This report highlights the processing effects of soaking and hydrothermal techniques on some underutilised hard-to-cook legume crops and the importance of tannin in legume nutrition. Soaking and hydrothermal processing reduce the tannin content of processed legume seeds and hence improve the availability of protein and mineral elements. In view of the recent findings of the health benefits, classification of tannin which is traditionally regarded as an antinutrient should be reconsidered. Provision of these information will enhance knowledge of legume nutrition and economic utility. Increasing consumption of underutilized nutritionally important legume seeds, it is hoped, will alleviate the problem of protein energy malnutrition in many developing nations.

Keywords: hydrothermal techniques; legume seeds; nutritional implication; tannin.