The microbiological quality of Slovenian raw milk from vending machines and their hygienic-technical conditions

The purpose of this paper is to study the microbiological quality of raw milk delivered by 17 vending machines (VM) owned by different Slovenian milk producers.

For the determination of hygiene-technical conditions of VM, an observation list that included criteria for estimation of hygiene-technical suitability was made. A total of 51 milk samples were collected in three different seasons. The swabs and the cleaning liquid (eluates) of dispensing nozzles and chambers were also sampled. The main groups of microorganisms were determined by colony count technique according to international standards in all collected samples.

The aerobic colony count was higher than 100,000 CFU/mL in 20 (39.2 per cent) of milk samples. Its mean value was 4.8 log10 CFU/mL. The mean values of Enterobacteriaceae, psychrotrophic microorganisms, lipolytes, proteolytes, yeasts and moulds together, coagulase-positive staphylococci and somatic cell count were 3.3 log10 CFU/mL, 4.1 log10 CFU/mL, 3.2 log10 CFU/mL, 3.9 log10 CFU/mL, 2.2 log10 CFU/mL, 2.8 log10 CFU/mL and 5.3 log10 cells/mL, respectively. E. coli was found in 33.3 per cent of milk samples, while Listeria monocytogenes and antibiotics were not detected. The inner surface contamination of the dispensing nozzles and chambers was estimated in the range from 1.8 log10 CFU to 6.0 log10 CFU/cm². The presence of detergents and disinfectants in supply valve eluates was determined in more than one-third of the samples. The hygienic-technical conditions of observed VM show some deviations from specified hygienic-technical requirements which could influence the safety of raw milk.

The data about construction and the cleaning practice of VM, included in the experiment, were not available during the inspection facility.

In the paper the pathogenic and also the spoilage microorganisms in milk in the combination with hygienic conditions of inside surfaces of VM were studied.