Assessing the Microbiological Level and the Incidence of Water-soaking on the Proximate Composition of two Cultivars of Cowpea (Vigna unguiculata L.) Grains Grown in Côte d’Ivoire.

ABSTRACT

Aims: This study was undertaken to assess the influence of seed treatment (soaking in water) on nutritional and microbiological composition of two cowpea cultivars. Place and Duration of Study Laboratory of Food Biochemistry and Tropical Products Technology, and the laboratory of Biotechnology and Food Microbiology, University of Nangui Abrogoua, Abidjan, between October 2010 and December 2011. Study Design: Method based on AOAC tests and AFNOR for microbiological analysis. A two-way analysis of variance and t-test were used. Methodology: The proximate composition of soaked and non soaked cowpea grains was determined and microbiological (bacteriological and mycological) analysis of these grains was also performed. Results: The major components were 28% and 26.25% protein, 48.35% and 47.99% carbohydrate, 41.66% and 40.05% starch for the RC (red cultivar) and WC (white cultivar) respectively. Lipids are less represented in the 2 cultivars (2.5%). There were significant reductions in the contents of the major components as a result of the treatment. Plain water soaking brought about a significant decrease in the proximate composition causing a mean reduction of 3.14% and 10.02% protein, 28.23% and 29.30% carbohydrate, 29.47% and 28.94% starch, 18.80% and 22.02 % energy for the RC and WC respectively. The mean decrease for mineral was 23.13% and 47.66% iron, 2.32% and 8.15% calcium, 9.30% and 2.10% phosphorus for the RC and WC respectively. In general the highest reduction was observed in the WC variety. Mean count (Log10 cfu/g) of total aerobic miroflora, coliforms, mould and yeast were 6.29 and 6.43; 2.04 and 2.58; 4.41 and 4.78 for the RC and WC respectively. Five genera of mould were isolated Aspergillus, Mucor, Penicillium, Botrytis and Geotrichum. The predominant fungi belonged to Aspergillus genus. Conclusion: The cultivar types of cowpea and the preparation methods could affect the nutrient availability of this product. Cold water soaking has a great influence on the properties of cowpea grains.