TOTAL BACTERIA COUNTING PROFILE OF RAW MILK IN MINAS GERAIS STATE ACCORDING TO THE STORAGE SYSTEM

Abstract Text: The microbial contamination of milk is influenced by several factors and it is one of the major hindering problems for milk quality improvement in Brazil. The objective of the present work was to evaluate total bacteria counting of milk collected in different storage systems. A total of 1,080 samples of milk from three regions of Minas Gerais State (Triângulo Mineiro, Sul, and Leste) were analyzed for total bacteria counting, during a 12-month period. The samples were randomly selected from three storage systems, individual bulk tank milk, collective bulk tank milk, and cans. The last two storage systems are exceptionally allowed in Brazil under specific conditions. Each storage system was represented by 360 samples, which were preserved with azidiol, and sent to the laboratory for analysis in up to 72 hours, using insulated boxes with reusable ice. All samples were evaluated by flow cytometry in the official federal net of laboratories for milk quality analysis in Brazil. Data were analyzed using general linear model and Tukey test for pairwise comparison. Collection system was the major factor correlated to the milk quality, with average countings of 5.38, 5.89, and 5.75 log CFU/mL for milk stored in bulk tank milk, collective bulk tank milk, and can, respectively. Non-compliance to the current standard of 600,000 CFU/mL was found in 47.6% of the samples, with 32.2%, 61.1%, and 49.7% non-compliant samples from bulk tank milk, collective bulk tank milk, and can, respectively. Considering recommended international standards, only 18.1% of the samples were in the range of up to 100,000 CFU/mL, comprising 28.6%, 8.3%, and 17.2 % for, respectively bulk tank milk, collective bulk tank milk, and can storage.  Milk quality was correlated to the seasonal variation (p<0.05), with 53% of the samples above the limit of 600,000 CFU/mL during the rainy season. Regional differences were also observed. It is concluded that collecting systems, and regional and seasonal differences must be considered for strategic action by the dairy industries towards microbial quality improvement of raw milk.

Keywords: Brazil, Microbial contamination and Milk quality