Impact of the residues of detergents and disinfectants used in dairy farms on the results of inhibitor tests for raw milk

The aim of the study was to determine the impact of residues of detergents and disinfectants on the results of most commonly used inhibitor tests for raw milk. Microbiological test (Delvotest SP-NT) and three rapid tests (Charm 3 MRL BL/TET2, Charm ROSA MRL BL/TET and Penzym) were used in the study. Three concentrations (recommended by the manufacturer, 10 times lower and twice higher) of 36 detergents and disinfectants in raw milk were investigated. All methods did not detect concentrations of detergents and disinfectants of alkaline and acid origin 10 times lower than recommended by the manufacturer. 39% of the investigated substances of alkaline origin were detected by Delvotest SP-NT and Penzym; Charm tests showed non-typical results only. Delvotest SP-NT did not detect substances of acid origin; Penzym detected 50% of these substances, Charm tests showed only non-typical results. Delvotest SP-NT and Penzym appeared to be more sensitive to the substances used for teat hygiene and disinfection. The scope of rapid tests (receptor or enzymatic) does not cover the detection of detergent and disinfectant residues in milk. However, according to the non-typical results of the test, it is possible to suspect the presence of these substances in milk. McNemar’s and Cochran’s Q tests were used for statistical analysis of the data.