Effect of Processing on Chemical Composition of Red Kidney Bean (Phaseolus vulgaris L.) Flour

Abstract

Proximate, mineral and amino acid compositions of raw and processed red kidney bean (Phaseolus vulgaris L.) flour were investigated on dry weight bases with a view to finding alternative and cheaper sources of protein to solve the problem of malnutrition due to inadequate protein in nutrition which is a prevalent problem in developing world, especially in Nigeria. Processing methods (cooking, boiling, roasting, sprouting and fermenting) were adopted using the standard analytical techniques. The processing methods showed deviations in nutrient content from the raw seeds. Crude fat was reduced by some processing methods particularly cooking and boiling while crude protein was enhanced in this order: Roasting > fermenting > boiling > sprouting > cooking. Processing significantly affected the mineral content of the red kidney bean flour (p<0.05). Boiling and roasting reduced the content of magnesium by 4.7 and 10.3%, respectively. All the processing methods reduced calcium content. Processed red kidney bean seed flour was found to be a good source of essential minerals, while harmful heavy metals such as lead and cadmium were not detected. The amino acid profile revealed cooking, roasting, sprouting and fermenting to have enhanced Total Amino Acid (TAA), while Total Essential Amino Acid (TEAA) and Total Sulphur Amino Acid (TSAA) were reduced by all the processing methods. After processing of the red kidney bean seed sufficient amount of essential amino acids were retained to meet FAO dietary requirement, but supplementation may be done for raw in Ile, Met + Cys, Thr and Val; boiled (Ile, Met + Cys and Thr); cooked (Met Cys and Val); roasted (Ile, Met + Cys and Val); sprouted and fermented (Met + Cys, Thr and Val).