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Bio-fortified foods usually have high nutrient contents and have potential to improve
nutritional status of vulnerable groups; however, increased levels of nutrients do not
necessarily translate to enhanced bioavailability due to presence of dietary anti-nutritional
factors. The study aimed to determine the effect of cooking and dietary anti-nutritional
factors on the content of zinc and iron of bio-fortified beans as compared to non-biofortified
varieties. Three bio-fortified bean varieties (Selian 13, 14 and 15) and a non-biofortified
variety (JESCA) which was a benchmark were analyzed by atomic absorption
spectrophotometry for the content of iron, zinc and dietary anti-nutritional factors before
and after cooking. Determination of anti-nutritional factors (phytic acid) was through
phytate precipitation, polyphenols by Follin-Ciocalteu reagent spectrophotometer method
and for tannins by the Follin-Dennis reagent titration and spectrophotometric method.
Results showed that bio-fortified beans contained a higher concentration of both iron and
zinc. Iron and zinc contents are expressed in mg/100g. JESCA contained 6.95 of Fe and
2.37 of Zn; Selian 13 had 15.21 of Fe and 4.07 of Zn; Fe and Zn content of Selian 14 was
10.23 and 5.2, respectively and Selian 15 contained 17.02 of Fe and 4.92 of Zn. There was
a significant increase (p<0.05) in iron concentration in the bio-fortified bean varieties
Selian 13 and 15 and of zinc concentration in the bean variety Selian 14. Cooking of beans
at 100 ºC, in distilled water for 35-50 minutes reduced dietary anti-nutritional factors in
beans by 64.9 – 97.9%. Bio-fortified beans had higher iron and zinc content and exhibited
higher nutrient retention upon cooking. Beans can serve as a vehicle for bio-fortification
of iron and zinc, and thus serve as an intervention for reducing micronutrient deficiencies.
This study which only highlighted processes and findings before intake has shown that
bio-fortification has the potential to enhance bioavailability but this is not guaranteed
without taking into account other factors, therefore recommending further studies in
animals and humans. The use of bio-fortified beans as a source of iron should be
accompanied with information on handling, storage and preparation. |
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