Sanitation in dairies

The project started with an industry survey of commercial cleaning and sanitation agents used in the Nordic countries. Based on this survey a list of priorized disinfectants was included. The variation in testing procedures and scientific data acheived for these agents raised the motivation to prepare a harmonized testing procedure for agents used in the dairies. Traditional cultivation was selected as a routine method. The cultivation method assessed the viable bacteria, which were able to form colonies on agar plates. Staining procedures were developed and swabbing techniques using novel swabbing detergents were evaluated in pilot and process scales. The microscopical technique using DNA and metabolic stains enabled the distinction of dead and viable cells left on the surfaces. Furthermore, methods such as impedance, contact agar, agar moulding and ATP were used in the assessments. The results obtained in the experiments on cleaning of closed systems showed that treatment with a potassium hydroxide based cleaning agent containing chelating agent was the most efficient agent in removing soil and biofilm from surfaces. The results from the tests using low pressure cleaning of open systems indicated that the low pressure application system is not effective in removing all the biofilm unless the foaming agent itself is very effective. Therefore, the foaming agent must remain in contact with the surface for a sufficient length of time without drying. The suitability of a cleaning agent is dependent on the consistency of the soil and the type of bacteria to be removed from the surface. The testing of six disinfectants selected by the dairy partners, Valio Ltd. and Norwegian Dairies, was performed using tests proposed by CEN (prEN 1040 and 1276). The PrEN 1040 did not differentiate between the six disinfectants, whereas high levels of interfering substances e.g. skimmed milk and hard water used in PrEN 1276 reduced the efficacy of the majority of the disinfectants to variable degrees. Staphylococcus aureus and Pseudomonas aeruginosa were the most resistant to all disinfectants tested. Salmonella infantis was the most difficult to kill of the four "industrial" strains. The results also showed that Pseudomonas fragi dried on surfaces was more resistant to the disinfectants than were cells in suspension. The aim of fogging or disinfection testing in industrial scale was to study the efficacy of the disinfection on the exposed surfaces at different places in the room. Fogging may be defined as "chemical disinfection by means of automatic spraying of the disinfectant into a closed room". Controlled experiments with fogging were carried out at two cheese producing dairies. Neither of the fogging trials showed clear reduction of the microbial load. The experiments at both dairies clearly demonstrated the need for thorough control and follow up of fogging. Critical points were the quality and the amount of the fog, the disinfectant concentration and the rinsing. The use of fogging also increased the humidity in the room, which may increase corrosion and damage on the electrical equipment. Conclusion of the fogging experiments was that the effect was questionable, especially in critical points and also in dry rooms.