Effect of cooking and concentration of inhibitors on Iron and zinc content of bio-fortified beans

Masters Thesis

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.

Building Nutritious Food Basket (BNFB) project