SOME MICROBIOLOGICAL STUDIES ON CASSAVA FLOUR

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Date
1987-06
Authors
YOBE, VIVIAN NGOZI
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Abstract
ined from parts of Nigeria were analysed for total aerobic bacteria, aerobic spore formers, lactose ana non-lactose fermenting Enterobacteriaceae, xerophillc and hydrophilic moulds and yeasts. The flour samples were observed to be highly contaminated by the various groups of microorganisms enumerated, The range of counts obtained for the different groups of microorganims were aerobic plate count (1.1x104 -2.8x10 cfu/g), aerobic spore count (<1.3x113 -2.9x106 cfu/g), lactose fermenters (<1.0x103 -6.6x106 cfu/g), non-lactose fermenters (<1.0x103-3.8x105 cfu/g), xerophilic moulds (<1.0x102-1.6x105 cfu/g), hydrophilic moulds (<1.0x102-6.4x105 cfu/g), yeasts (1.0x102-1.9x106 cfu/g). The fungal isolates from the cassava flour samples were identified. The predominant generation of moulds were Aspergillus and Penicillium. Sixty percent of the total number of samples were contaminated by A. flavus which was the most predominant species of Aspergillus. The second most predominant fungus, A. niger, was isolated from 43% of the total number of samples. PeniciIlium spp. occurred in 48% of all the samples examined. Other species of fungi isolated from cassava flour were Sporcndonema sebi, Curvularia lunata, Aureobasidium pullulans (a yeast-like mould), Rhiiopus stolonifer, R. oryzae, pigmented and non-pigmented yeasts. Thirteen out of 60 A. flavus strains isolated from cassava flour produced aflatoxins in yeast extract broth medium containing 20% sucrose. Ten of the aflatoxigenic strains produced aflatoxins B1, B2, G1, G2 while three produced aflatoxins B1 and B2 only. The amount of aflatoxins produced were relatively high and ranged from 3.0-14.2 ug/ml (B1,) 0.9-11.9 Ug/ml (B2), 0-12.5 ug/ml (G1) and 0-9.2 ug/ml (G2). Aflatoxin producing strains of A. flavus were isolated from cassava flour samples obtained from different geographical areas-of Nigeria. The results are discussed in relation to possible sources of microbial cohtamination of cassava flour and the need for improvement in overall sanitation during production and sale- of the product.
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A THESIS Submitted to the Fostgraduate School AHMADU BELLO UNIVERSITY, ZARIA in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Dcpartmentof Microbiology Faculty of Science, Ahmadu Bello University, Zaria, NIGERIA.
Keywords
MICROBIOLOGICAL,, CASSAVA FLOUR
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