Food Chemistry

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Folate content in processed legume foods commonly
consumed in Egypt
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Folic acid and folate
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Folate is a water soluble B-vitamin , which is
essential for the biosynthesis of purines and
pyrimidines, as well as amino acid
interconversions, all of which are part of one
carbon metabolism. In this respect, folate plays
an important role as one-carbon donor and
acceptor Different forms of folate the
unsubstituted dihydro and tetrahydro forms, are
chemically unstable. They are easily split
between the C-9 and N-10 bond to yield a
substituted pteridine and p-aminobenzoylglutamate,
which have no biologic activity. Substituting
a carbon group at N-5 or N-10 decreases the
tendency of the molecule to split however, the
substituted forms are also susceptible to
oxidative chemical rearrangements and,
consequently, loss of activity.   The chemical
lability of all naturally occurring folates
results in a significant loss of biochemical
activity during harvesting, storage, processing,
and preparation. Half or even three-quarters of
initial folate activity may be lost during these
processes Insufficient dietary folate May
cause colon cancer, neural tube defects and
cardiovascular disease
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Legumes are reported to be good dietary sources
of folate, but since they are processed before
consumption, they are subjected to treatments
which can affect the folate content. Faba beans
are a common food in Egypt and are frequently
consumed in the traditional diet as bean stew
(foul), germinated and blanched as soup (nabet)
and deep-fried as paste balls (falafel). The most
frequently used method for industrial faba bean
processing is canning (foul).
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Food Proccessing
1- industrial canning Industrial canning
comprises several steps A-soaking B-Blanching is
commonly used to reduce enzyme activity, which
can cause undesirable changes in colour, flavour,
odour or nutritive value during frozen storage of
vegetable C- Retorting
2- germination Including soaking and
incubation
3-house hold cooking Traditional Egyptian faba
bean foods (foul, nabet and falafel)
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3-house hold cooking
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Food analysis Folates were quantified by HPLC
based on fluorescence detection also folate
content has been quantified by microbiological
assay using cryo-protected and chloramphenicol-res
istant Lactobacillus Rhamnosus on 96- well
microtiter plates Folate data determined by
HPLC are usually expressed as the sum of all
quantified individual folate forms and are
commonly 20-50 lower than the total folate
content determined by microbiological assay
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1- Effect of industrial canning on folate
content in faba beans and chickpeas Industrial
canning (soaking, blanching and
Retorting) Industrial canning comprises several
steps which affect the folate content
differently. The data (Table 1) indicated that
the final canned faba bean and chickpea products
can be considered a good folate source, as either
no losses or folate retention of 70
during processing were observed. This confirms
findings by Jiratanan and Liu (2004), who
reported that thermal processes did not affect
the folate content in green beans. The increase
of the folate content in both legumes during
soaking is probably due to enzymatic de novo
synthesis from initiated germination. blanching
according to common practice reduced the folate
content in faba beans and chickpeas by only 10
and 20, respectively, probably by leaching into
the blanching water
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Retorting using Tetra Recart packages resulted in
folate losses of 15-20 in faba beans and 30-43
in chickpeas. The folate lost from the faba beans
and chickpeas during retorting was recovered in
the canning medium, confirming that leaching was
the main cause, In Egypt the canning medium is
habitually consumed with the beans, so the
leached folate is not lost from consumption.
The folate retention in chickpeas was lower
than that in faba beans, which can possibly be
attributed to the outer shell of faba beans
reducing losses. A change in retorting
conditions from 121 oC for 11 min to 128 oC for 5
min had no effect on the folate content in faba
beans. On the other hand, the folate losses in
chickpeas after the retorting conditions were
changed in the present study were as high as 40
. Addition of EDTA to the canning medium did not
affect the folate content in either legume
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2-Effect of Germination on folate content in
faba beans and chickpeas
Germination resulted in an up to 2.4-fold
increase in the folate content of faba beans and
chickpeas The increased folate content during
germination might be due to de novo synthesis of
folate, which is accelerated during germination
because of increased demand for methyl groups. In
the present study, 5-CH3-H4folate was the
predominant folate form in germinated faba beans
and chickpeas, amounting to gt80 of the folate
content.
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3-Effect of Household cooking on folate content
in faba beans The extent of folate retention
during household cooking depends on the method of
food preparation, as shown in this study. The
high folate content in bean stew and nabet beans
was due to soaking and germination (Fig. 2).
After boiling of the germinated faba beans
(nabet), only 68 of the folate content was
retained in the beans, but approx. 90 of the
lost folate was found in the cooking medium,
which is also consumed. Our findings confirm that
folate losses during boiling are mainly due to
leaching and not to degradation Therefore, as the
cooking medium is consumed as soup, no losses
need to be accounted for.
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