ABSTRACT

Cassava fufu flours were produced following 72 h fermentation, of two cassava varieties (TME 419 and Umucass 45) by lactic acid fermentation and natural fermentation (0-72 h). Two starter cultures (L. plantarum, L. fermentum and their combination) were used to initiate lactic acid fermentation. At 24 h intervals the pH, titratable acidity (TTA), microbial load (Starter culture count, total LAB count of natural fermenting mash, yeast/mould count, microbial quality) and molecular characterization of natural fermentation isolates were determined. The wet mash samples were dried and milled to flour and analyzed for chemical, functional and sensory properties of the flours. The results revealed that the percentage titratable acidity of the cassava varieties increased from 0.23 – 1.18% as fermentation progressed in relation to decrease in pH (5.22 -3.70). Samples (419 LP+LF and 45LP) gave the highest starter culture count of 5.62 log CFU/g at 48 h and showed a decrease at 72 h of fermentation. The sequencing of PCR of 16s rRNA gene, identified the bacterial isolates as Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus pentosus, Lactococcus lactis and Saccharomyces cerevisae. The cassava flour samples were safe for consumption since potential pathogens were not detected. The fresh cassava carotenoid content of Umucass 45 had the highest carotenoid value (11.7mg/g) which showed significant difference (p < 0.05) from other samples. The sugar and starch contents showed similar trends. Sugar content ranged from (4.93 – 2.20), with unfermented sample having the highest value. The proximate composition of the products ranged from; Moisture (8.58 – 11.14%), Ash (1.30 – 2.54%) crude protein (1.38 – 5.73%), crude fibre (0.70 – 1.76%), fat (0.52 – 0.93%) and carbohydrate (81.09 – 84.84%).  Functional properties increased in bulk density (0.66 – 0.79 g/ml), oil absorption (1.25 – 1.36 g/ml), water absorption (2.98 – 3.52 g/ml), swell index (2.73 – 3.45 g/ml), while a decrease in gelatinization temperature (70.10 – 67.45⁰c) was observed. Fermentation reduced significantly, the anti-nutritional factors: HCN (48.03 - 3.16mg/100g), phytate (5.12 – 0.23 mg/100g), tannin (2.22 – 0.20 mg/100g), alkaloid (3.84 – 0.06 mg/100g). Amino acid profile revealed that fermentation led to significant improvement of   protein quality of the flour products. The highest essential amino acid leucine (6.36 g/100g) and non-essential amino acids glutamic acid (7.64 g/100g) were recorded for flour from yellow cassava. Minerals of samples ranged from 28.42 – 31.10 mg/100g for calcium; 15.30 – 21.67 mg/100g magnesium; 35.29 – 46.31 mg/100g potassium; 13.07 – 18.33 mg/100g phosphorus; 0.67 – 1.75 mg/100g zinc; and 1.25 – 3.52 mg/100g iron respectively. The Gas Chromatograph Mass Spectrometer (GCMS) profile of samples detected the presence of alcohol (penatdecanol) and acids (hexadecanoic acid) indicating the flour products contain different flavor compounds, due to different microorganisms present during processing. Sensory evaluation, showed that starter culture and natural fermented flours were not significantly different (p > 0.05) in odour mould-ability, hand feel and overall acceptability but showed significant difference (P < 0.05) in appearance and acceptable. The flours had good functional and sensory properties. Fermentation either natural or with starter cultures can enhance the nutritive value of cassava tubers for sustainable local technologies and utilization of the value-added product for human nutrition.