Microbiological survey of milk and dairy products from a small scale dairy processing unit in Maroua (Cameroon)

In the African context, the production of milk and dairy products is affected by the application of improper procedures during milking and processing, leading to microbial spoilage of milk, especially in local small scale processing plants. The aim of this survey was to identify potential hazards and evaluate the microbial contamination of milk and dairy products in a small scale dairy processing unit located in Cameroon. During a 6 week period, raw and pasteurized milk samples were evaluated for Total Aerobic Bacterial Count e TBC, Total Coliforms, Escherichia coli and Coagulase Positive Staphylococci e CPS; dairy products (yoghurt, soft cheese, mozzarella and ricotta) were also submitted to the count of Total Coliforms, E. coli and CPS. Contamination levels of raw milk samples varied widely; about half of the samples complied with threshold values for TBC (<6.3 Log CFU/ml), while high coliforms counts (>5.0 Log CFU/ml) were detected in some samples. In pasteurized milk, high residual counts were observed, indicating an insufficient efficacy of thermal treatment applied at the small scale unit; residual values >3 Log CFU/ml were detected for TBC, in some cases associated with high counts for the other parameters. Among dairy products, mozzarella and soft cheese resulted the most contaminated by coliforms (mean value 2.7 Log CFU/g), while low contamination levels were detected for ricotta and yoghurt. Some samples of mozzarella also harboured high counts (>3 Log CFU/g) of E. coli. Based on microbiological outcomes and milk production flow characterisation, Preventive and Corrective Measures were defined for milking and processing phases (thermal treatment, packaging and storage), focussing on training of farmers and dairy employees to improve the hygiene of the local milk and dairy production chain.