Effects of cooking methods on the iron and zinc contents in cowpea (Vigna unguiculata) to combat nutritional deficiencies in Brazil.

BACKGROUND: Because iron deficiency anemia is prevalent in developing countries, determining the levels of iron and zinc in beans, the second most consumed staple food in Brazil, is essential, especially for the low-income people who experience a deficiency of these minerals in their diet. OBJECTIVES: This study aimed to evaluate the effect of cooking methods by measuring the iron and zinc contents in cowpea cultivars before and after soaking to determine the retention of these minerals. METHODS: The samples were cooked in both regular pans and pressure cookers with and without previous soaking. Mineral analyses were carried out by Spectrometry of Inductively Coupled Plasma (ICP). RESULTS: The results showed high contents of iron and zinc in raw samples as well as in cooked ones, with the use of regular pan resulting in greater percentage of iron retention and the use of pressure cooker ensuring higher retention of zinc. CONCLUSIONS: The best retention of iron was found in the BRS Aracê cultivar prepared in a regular pan with previous soaking. This cultivar may be indicated for cultivation and human consumption. The best retention of zinc was found for the BRS Tumucumaque cultivar prepared in a pressure cooker without previous soaking.

Iron and zinc retention in common beans (Phaseolus vulgaris L.) after home cooking.

BACKGROUND: According to the World Health Organization (WHO), iron, iodine, and Vitamin A deficiencies are the most common forms of malnutrition, leading to severe public health consequences. The importance of iron and zinc in human nutrition and the number of children found to be deficient in these nutrients make further studies on retention in cooked grains and cooked bean broth important. OBJECTIVES: This work aimed to evaluate iron and zinc retention in six common bean (Phaseolus vulgaris L.) cultivars under the following conditions: raw beans, regular pot cooking, pressure cooking, with and without previous water soaking, and broth. DESIGN: Determination of iron and zinc content in the raw, cooked bean grains and broth samples was carried out by Inductively Coupled Plasma (ICP) Optical Emission Spectrometry (Spectro Analytical Instrument - Spectroflame P). All experiments and analyses were carried out in triplicate. RESULTS: Overall, regardless of the cooking method, with or without previous water soaking, the highest zinc concentration was found in the cooked bean grains. However, pressure cooking and previous water soaking diminished iron retention in the cooked grains, while increasing it in the bean broth. CONCLUSION: The common bean was confirmed to be an excellent source of iron and zinc for human consumption, and it was suggested that beans should be consumed in a combined form, i.e. grain with bean broth.