Effect of Malting on the Chemical Composition of Cowpea (Vigna unguiculata) and Soybeans (Glycine max) Seeds

Abstract

Objective: To produce cowpea and soybean malts of acceptable diastatic quality and evaluate changes in chemical composition of the malted cowpea and soybean. Materials and Methods: Malts of cowpea and soybean were produced by steeping in clean tap water for 4 hours, air rested for 2 hours and re-steeped in water for 4 hours. The out-of-steep grains were germinated in the dark for 72 hours and oven dried at 50 °C. The malts were analyzed for diastatic activity and their contents of moisture, protein, sugar, fat, peroxidation products, phytate, tannin and trypsin inhibitor. Results: After malting, the diastatic activity of cowpea increased from 28.87 to 63.33 °L while soybean’s increased from 27.33 to 30.00 °L. The moisture, protein and sugar contents also increased while the fat content decreased, TBA content increased in cowpea (0.002 to 0.003 mg/100g) but remained unchanged in soybean. Phytate and tannin contents decreased in cowpea but increased in soybean, while the activity of trypsin inhibitor increased in cowpea, but decreased in soybean. Conclusion: Cowpea and soybean malts of acceptable diastatic and nutritional quality were produced by the two-step wet steep malting process. The malts could be resourcefully applied to increasing nutrient density in foods particularly when used to as enrichment agents. However, cowpea malts may not be suitable for storage because of the increased TBA content.

Key words: cowpea, soybean, malting, chemical composition.