Techniques to evaluate cleanliness and disinfection in dairies

Abstract

Cleaning and disinfection operations in dairies require fast and efficient verification methods. Through these operations, the cross-contamination of cheeses is prevented throughout production steps and especially during curd formation. Cleanliness and disinfection plans begin with the selection of detergents and disinfectants and culminate in the choice of microbiological control technique most suitable for industrial dairies. In both stages it is necessary to consider the application methods and procedures of the program, which in this case include the application time of detergents, disinfectants and rinse water. Numerous Ŗsampling toolsŗ are marketed for microbiological control of surfaces. The more applicable are printing techniques, such as those utilising contact agar plates, dipslides or Petrifilm™, in addition to sowing in a plate of the final rinse water or ATP (Adenosine Triphosphate)-bioluminescence, which gives an indirect reading of the number of bacteria on the surface because the result is expressed in Relative Light Units (RLUs). Each of these methods provides a different reading and interpretation of Colony Forming Units (CFU/cm2), so the choice of method should be based on the surfaces and microbiota to be tested. Although there are studies supporting the compatibility of the contact agar plates and dipslide printing methods, which are very similar techniques, these techniques are different from the luminescence technique or rapid kits for protein detection. These techniques are appealing because they are simple tests that can be applied to surfaces and provide immediate feedback to workers, and they have higher sensitivity than the printing techniques. Thus, the choice of verification method for testing cleanliness and disinfection operations should be considered prior to implementation in dairies. Similarly, the results of the test should be interpreted according to the technique and tested surfaces used. In terms of guidelines regarding microbiological criteria for foodstuffs, the European Community (EC) has established that the total viable count and total Enterobacteriaceae count on cleaned and disinfected surfaces in meat establishments should be ≤ 10 CFU/cm2 and ≤ 1 CFU/cm2, respectively. The suitability of the technique should be established in trials that involve the sampling of various surfaces in the particular processing environment following specific sanitation procedures. Many of the methods are still under evaluation at present, and much experimental validation is still needed before they can be applied for quality control in dairies. Therefore, the aim of this chapter is to review the most appropriate methods for the microbiological control of surfaces in dairies, as well as the interpretation of results.