Effects of fermentation and extrusion on the proximate composition and organoleptic properties of sorghum-soya blend

Abstract

The effect of extrusion and fermentation on the proximate composition and organoleptic properties of six combinations (100:0, 90:10, 80:20, 70:30, 60:40 and 50:50) of sorghum - soya blend were investigated. A total number of 19 microorganisms were isolated during the fermentation of sorghum-soya extrudates; these comprise of twelve (12) bacteria, four (4) yeast and three (3) moulds. They include Flavobacterium rigense, Micrococcus icristinae, Enterobacter cloacae, Enterobacter spp., Corynebacterium cystitidis, C. pilosun, Staphylococcus albus, Brevibacterium spp., Bacillus subtilis, B. cereus, B. brevis, B. megaterium, Candida famata, Saccharomyces cerevisiae, Geotrichum candidium, C. utilis, Aspergillus niger, A. fumigatus and Rhizopus stolonifer. The pH and the total titratable acidity (TTA) significantly varied during fermentation. The proximate composition of the raw flour blend, unfermented and fermented extrudates was assessed. The crude protein and moisture contents increased in the extruded and fermented samples whereas; extrusion and fermentation reduced the ash and carbohydrate contents. Crude fibre and fat contents varied among all the samples. The sensory evaluation of the unfermented extrudates indicated a good preference for the product in term of colour, texture, aroma and overall acceptability.

Keywords: Fermentation, extrusion, sorghum-soya blend, proximate, orgnoleptic

African Journal of Biotechnology, Vol 13(40) 4008-4018