Microbial and Physicochemical Characterization of Maize and Wheat Flour from a Milling Company, Lesotho

Abstract

Maize meal flour and wheat flour are the most widely consumed cereals in Lesotho. The present study was undertaken to investigate the physicochemical and microbiological quality of special, super and extra super brands of maize meal flour; cake, white wheat and whole brown wheat brands of wheat flour produced by a mill company in Maseru, Lesotho. Three samples of each flour were collected on each of five sampling trips during January to May 2012, making a total of 90 samples, and were analysed physico-chemically for ash, fat, protein, moisture content and pH. Microbiologically, total plate count, total coliforms, Bacillus cereus, Salmonella spp, E. coli, yeasts and moulds were also determined. A series of biochemical tests were done to characterize the isolated micro-flora. Moisture content (9.89±0.76% to 13.31±0.64%) and pH (5.83±0.06 to 6.40±0.12) of the flours were within recommended legal limits. However, fat content (33% (n=90)) in maize samples exceeded the maximum recommended limit. The fat content (2.00±0.08% to 5.29±0.10%) of all maize meal brands was significantly higher (P<0.05) than that of wheat flour (0.90±0.03% to 1.87±0.02%). Protein content in maize meal was significantly lower than that of wheat flour, ranging from 7.01±0.91% to 9.64±0.09%. Ash content for the samples ranged from 0.29-1.21%. Statistically, bacterial counts in the different brands of flours showed significant differences (p < 0.05). In a more qualitative assessment, microbes of the genera Escherichia, Klebsiella, Aerobacter, Enterobacter, Salmonella, Bacillus, Aspergillus, Penicillium, Fusarium, Candida, Saccharomyces and Rhodotorula were identified in the flours. Pathogens (Bacillus cereus and Salmonella spp) and indicator organisms (coliforms and E. coli) were above World Food Programm (WFP) recommended limits. This study highlighted the need for stringent cleaning and sanitation regimes to be fully implemented in such companies for consumer safety and public health protection.