METHOD FOR MEASURING THE EFFICIENCY OF CLEANING AND DISINFECTION PROCESSES ON OPEN SURFACES

This paper describes a method for measuring the efficiency of cleaning and disinfection processes on open surfaces (which cannot be cleaned in situ by fluid flowing in a closed circuit). A robot was used for ensuring reproducibility of operations. Representative dairy soils (rennet curd of 45% fat ultrafiltration retentate, saint-paulin cheese solubilized in 2% trisodium citrate) were spread over a plate including 16 samples of the studied surface material. The latter was AISI 304L stainless steel, with a roughness R(a) of 0.25 or 0. 73 mum. Microbial tracers were added to the soils for separate quantification of cleaning (thermophilic bacterial spores of Bacillus thermophilus var calidolactis) and disinfection (mixed culture of 2 mesophilic vegetative bacteria: Lactococcus lactis subsp lactis, Leuconostoc mesenteroides). Disinfection tracers formed a biofilm in 18 h at 20-degrees-C. A multifactorial experimental design with 6 blocks including 2 repetitions was used. It enabled to show the influence and interactions of experimental factors such as application time, product concentration, soil type and weight, surface type and roughness, etc. The method was validated with a combined detergent-disinfectant. The method can be used in dairy and non-dairy contexts, since it can be applied to any representative soils and mirroorganisms (whether or not they form a biofilm), to any detergents and/or disinfectants, and with any experimental design.