Effects of Fermentation and Extrusion on the Proximate Compositions and Organoleptic Properties of Sweet Potato (Ipomoea batatas) and Beniseed (Sesamum indicum) Blends

Abstract

Fermentation and extrusion have been proven to increase the nutritional value of foods by reducing the water-binding capacity of cereal flour. Thus, the effect of fermentation and extrusion on the microbiological qualities, proximate compositions and organoleptic properties of orange flesh potato and beniseed blends were investigated using standard methods. The blended samples were prepared in four combinations (A=100 g sweet potato; B = 70 g sweet potato + 30 g beniseed; C= 60 g sweet potato + 40 g beniseed, D = 50 g sweet potato + 50 g Beniseed) and separated into four batches (i.e. first batch = preconditioned and fermented; second batch = extruded; third batch = fermented and extruded; and fourth batch = unfermented/unextruded). The blended samples were fermented for 72 hours using solid state fermentation. The bacteria isolated include Bacillus subtilis, Lactobacillus plantarum, Lactococcus lactis and Staphylococcus aureus while fungi include Mucor mucedo, Aspergillus niger, Penicillium chrysogenium, Aspergillus flavus, Geotrichum spp, Mucor mucedo and Alternaria alternate. The results of the proximate composition of the fermented and extruded blends showed a significant difference as compared with the unfermented and unextruded blends. The moisture content was highest in fermented extruded 50% sweet potato + 50% beniseed (18.61%) and least in the unfermented unextruded 50% sweet potato + 50% beniseed (4.0%). Fermentation also helps to increase the protein content and the highest was observed in composite bleed containing 50% sweet potato + 50% beniseed which increased from 2.88% to 8.75%. Extrusion also increased the protein content. The highest protein content was observed in the composite blend that was extruded and fermented (18.61). The carbohydrate content was highest in the unfermented unextruded 50% sweet potato + 50 beniseed (84.04%). The crude fat content was highest in the fermented unextruded 100% sweet potato blends (21.50%) and least in fermented extruded 50% sweet potato + 50 beniseed (2.0%). The sensory evaluation of the samples showed a good preference for the fermented-extruded samples. Findings from this research have established that orange flesh potato and beniseed blends can be fermented and extruded to produce food of enhanced nutritional value.