EFFECTS OF DIFFERENT FERMENTATION METHODS ON THE NUTRITIONAL COMPOSITION OF CASSAVA AND BAMBARA GROUNDNUT FLOUR BLENDS

Abstract

In an attempt to improve the nutritional qualities of cassava flour, the effects of different fermentation methods on the nutritional composition of cassava and bambara groundnut flour blend, as well as the biological evaluation of the protein quality of the blend products were investigated. Forty-four growing albino rats were used to assess the quality of cassava-bambara groundnut composite flours using five treatment diets of fermented cassava flour containing different levels of bambara groundnut flour substitution (10, 20, 30, 40 and 50%) in a 28-day feeding experiment to assess the protein quality on the growth response. The results of total bacterial mean count of cassava significantly increased in submerged culture more than in solid state fermentation during the entire fermentation period, the bacterial population increased from 2.52 × 105 to 4. 00 × 105 cfu/g while the bacteria population on submerged fermentation increased from 2.60 × 105 to 4.50 × 105 cfu/g. A total number of thirty-two (32) microorganisms were isolated during the fermentation of cassava-bambara blend; These comprised of the twenty-four bacteria and seven fungi species. They include Lactobacillus sp., Staphylococcus aureus, Bacillus sp., Proteus vulgaris, Rhizopus sp., Aspergillus flavus, Mucor mucedo, Penicillium sp.,, Saccharamyce sp., Candida sp., and Fusarium sp. The pH and the total titratable acidity (TTA) significantly varied during fermentation. The moisture content (%) of solid (SSF) and submerged fermentation (SMF) of Cassava-Bambara groundnut flour blends revealed that 10% bambara groundnut flour blends had the lowest moisture (5.20 %) in SSF and 6.00 % in SMF while the highest moisture content (9.90%) was recorded in 50% BAM of SSF and 11% in 50% BAM submerged fermentation. The crude protein and moisture contents increased in the fermented samples while the ash, carbohydrate, crude fiber and fat contents varied among all the samples. However, rats fed with 50% BAM obtained from both solid state and submerged fermentation showed an increase of 84 g and 90 g in body weight respectively. Also, rats fed with 100% bambara groundnut flour obtained from SMF had the least body weight (55g). The sensory evaluation indicated that there was significant difference in the taste, aroma, colour and overall acceptability in both SSF and SMF of the sample blends. The blend (100% CAS) from SMF recorded significantly high values in terms of taste (6.50), colour (6.17) and overall acceptability (6.41) while 10% BAM SMF recorded significantly highest value in terms of aroma. The PCV for the experimental rats ranged from 28.00 ± 0.00 % to 48.00 ± 0.00% with the rat fed with 10 % bambara solid state fermentation having the lowest PCV and rat fed with 50% BAM SSF having the highest PCV (48.00%). The RBC for the experimental rats ranged from 3.45 ± 0.01 to 4.84 ± 0.01 with the rat fed with 40%BAM SSF having the lowest RBC and rat fed with 10% Bambara SMF having the highest RBC. The kidney tissue of experimental albino rat fed with 50% Bambara groundnut flour, 40% Bambara groundnut flour, 30% Bambara groundnut flour, 20% Bambara groundnut flour and 10% Bambara groundnut flour showed normal nephrons architecture with properly formed bowman capsule. It is evident from the composition of the developed products that protein-energy malnutrition and micronutrient deficiency problems can be averted through dietary diversification.