CORRELATION ANALYSIS OF FACTORS AFFECTING THE BACTERIAL CONTAMINATION OF MILK

When analyzing raw milk properties, we should take into account the complexity and ambiguity of the “bacterial contamination” criterion. The authors evaluated the infl uence of physico-chemical and microbiological parameters of milk on its contamination over a year period. Milk testing protocols for 2020 were used as a source of information. The values of acidity, the number of mesophilic aerobic and facultative anaerobic microorganisms (CMAFAnM), the number of somatic cells, the proportion of protein and fat, and the density of milk were studied. To assess the infl uence of environmental parameters, the authors took ionto account the values of air temperature and humidity at the moment of sampling. Sampling was carried out according to GOST 26809.1-2014 “Milk and dairy products. Acceptance rules, sampling methods, and sample preparation for analysis”. The research was carried out on three dairy farms of the Knyaginino district of the Nizhny Novgorod region. They included a dairy farm with tie-up housing for 200 heads with milking in a linear type milk pipeline; a dairy farm with loose housing for 400 heads with milking in a herringbone type milk pipeline; a dairy farm with combined (tie-up and loose) housing for 450 heads with milking in a linear-type milk pipeline. The lowest indicator of QMAFAnM (total viable content) was noticed in March, and the highest – in November. The correlation analysis showed that the greatest infl uence of the studied factors on the level of bacterial contamination is exerted by the number of somatic cells (Pearson correlation coeffi cient R = 0.71 with a confi dence probability P = 0.0619). The authors suppose that this situation may result from improper hygienic condition of the udder, equipment, and premises. There was a weak infl uence on the level of bacterial contamination of milk density (R = –0.18 at P = 0.096) and ambient air temperature (R = –0.18 at P = 0.095), which may be result from insuffi cient cooling of milk before transportation.

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