THE INFLUENCE OF EXTRUSION PROCESSING ON IRON DIALYZABILITY, PHYTATESAND TANNINS IN LEGUMES

Iron dialyzability, chemical forms of iron, tannin content, and phytic acid degradation in boiled low impact and high impact extruded navy b eans, chickpeas, cowpeas and lentils were determined. In boiled legume s, the dialyzable iron was 1.2-2.7% of total iron. Dialyzable, soluble and ionic iron were highest in low impact, extruded legume flours. Lo wer forms of inositol phosphates (inositol tri-, tetra- and penta-phos phates) increased to 51-71% of total phytate in legumes processed by b oiling or extrusion compared to 21-33 % in raw legumes. Tannin content was lower in extruded products compared to boiled or raw legumes. The influence of extrusion processing on iron dialyzability varied with p rocessing conditions. Results suggest that the degradation of phytate and changes in tannin content may not be responsible for the increase in iron dialyzability and solubility associated with low impact extrus ion processing.