Influence of heat processing on the bioaccessibility of zinc and iron from cereals and pulses consumed in India

Influence of heat processing on the bioaccessibility of zinc and iron from food grains consumed in India was
evaluated. Cereals – rice (Oryza sativa), finger millet (Eleusine coracana), sorghum (Sorghum vulgare), wheat (Triticum
aestivum), and maize (Zea mays), and pulses – chickpea (Cicer arietinum) – whole and decorticated, green gram
(Phaseolus aureus) – whole and decorticated, decorticated black gram (Phaseolus mungo), decorticated red gram
(Cajanus cajan), cowpea (Vigna catjang), and French bean (Phaseolus vulgaris) were examined for zinc and iron
bioaccessibility by employing an in vitro dialysability procedure. Both pressure-cooking and microwave heating were
tested for their influence on mineral bioaccessibility. Zinc bioaccessibility from food grains was considerably reduced
upon pressure-cooking, especially in pulses. Among cereals, pressure-cooking decreased zinc bioaccessibility by 63%
and 57% in finger millet and rice, respectively. All the pressure-cooked cereals showed similar percent zinc
bioaccessibility with the exception of finger millet. Bioaccessibility of zinc from pulses was generally lower as a result of
pressure-cooking or microwave heating. The decrease in bioaccessibility of zinc caused by microwave heating ranged
from 11.4% in chickpea (whole) to 63% in cowpea. Decrease in zinc bioaccessibility was 48% in pressure-cooked
whole chickpea, 45% and 55% in pressure-cooked or microwave-heated whole green gram, 32% and 22% in pressurecooked
or microwave-heated decorticated green gram, and 45% in microwave-heated black gram. Iron
bioaccessibility, on the other hand, was significantly enhanced generally from all the food grains studied upon heat
treatment. Thus, heat treatment of grains produced contrasting effect on zinc and iron bioaccessibility.
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