Monitoring bioaccessibility of iron and zinc in pearl millet grain after sequential milling.

The present study was to understand the effect of
sequential milling on the distribution of inhibitory factors
and their relation to iron–zinc bioaccessibility in the two
pearl millet cultivars differing in grain shape and size. The
studies revealed that the yield of decorticated grain and
bran fractions differed between the cultivars. The initial
bran fractions had lower iron content, which increased on
increase of decortication duration (2.33–25.14 mg/100 g),
while zinc did not follow this pattern. Among the inhibitory
factors, polyphenols and phytic acid were low in the
initial stages of milling and subsequently increased as the
milling duration increased. Microscopic studies further
confirmed that iron–zinc and inhibitory factors coexist in
the same tissues of the grain. The b- carotene was more
concentrated in the middle layers of the pericarp. It was
observed that iron bioaccessibility was the highest in the
4 min milling bran (7.7%, 3.34%) and final decorticated
grain fractions (13.79%, 18.45%) of both the cultivars. Iron
bioaccessibility could not be related to any particular
inhibitory factors, in bran insoluble fibre and phytic acid
were prominent while in decorticated grain galloyls, catechols
and phytic acid were the maxima. In both the cultivars,
zinc bioaccessibility was high in fractions with low
phytic acid and insoluble fibre. The data presented suggest
that 6 min decortication that removed around 10–15% of
the bran had the highest iron and zinc bioaccessibility. The
iron-rich bran fraction after appropriate processing can also
be used in speciality food and thereby addresses the
problem of micronutrient deficiency.