Phytate reduction in whole grains of wheat, rye, barley and oats after hydrothermal treatment

Whole grains of different cereals have traditionally been prepared with water and heat prior to dehulling, but knowledge of the effect on nutritional properties is limited. The aim of the present study was to investigate if phytate reduction occurred during hydrothermal treatment of whole grains. Wheat, rye, hulled and dehulled barley, hulled oats and naked oats were incubated with either water or acetate buffer (pH 4.8) at 55 degrees C for 24h with the exception of oats, which were incubated at 37 degrees C. Phytate in wheat, rye and barley was reduced by 46-77 % when water was used and by 84-99 % when acetate buffer was used. The phytate reduction in oats was considerably less, 8-26 %, but, after grinding and soaking, phytate was reduced by 72-77 % in dehulled oats and by 88-91% in naked oats. Citric acid and citrate buffer was used for pH adjustment in some experiments, and their use resulted in less phytate reduction than when acetate and lactic acid were used. Wet-steeping of naked oats and naked barley in water al 53-57 degrees C for 20-30 min reduced the bacterial counts by 99.97 %, and the addition of acid prevented bacterial growth during the incubations. It was concluded that cereals with reduced phytate content and good hygienic quality can be developed and produced using hydrothermal treatment of whole grains. (C) 1997 Academic Press Limited