W. Blel

Role of mechanical vs. chemical action in the removal of adherent Bacillus spores during CIP procedures.

This study was designed to evaluate the respective roles of mechanical and chemical effects on the removal of Bacillus spores during cleaning-in-place. This analysis was performed on 12 strains belonging to the Bacillus cereus group (B. cereus, Bacillus anthracis, Bacillus thuringiensis) or to less related Bacillus species (Bacillus pumilus, Bacillus licheniformis, Bacillus sporothermodurans, Bacillus subtilis). Adherent spores were subjected to rinsing-in-place (mechanical action) and cleaning-in-place (mechanical and chemical actions) procedures, the latter involving NaOH 0.5% at 60°C. Results revealed that mechanical action alone only removed between 53 and 89% of the attached spores at a shear stress of 500 Pa. This resistance to shear was not related to spore surface properties. Conversely, in the presence of NaOH at a shear stress of 4 Pa, spores were readily detached, with between 80 and 99% of the adherent spores detached during CIP and the chemical action greatly depended on the strain. This finding suggests that chemical action plays the major role during CIP, whose efficacy is significantly governed by the spore surface chemistry.

Effect of a new regeneration process by adsorption-coagulation and flocculation on the physicochemical properties and the detergent efficiency of regenerated cleaning solutions

Reprocessing soiled cleaning-in-place (CIP) solutions has large economic and environmental costs, and it would be cheaper and greener to recycle them. In food industries, recycling of CIP solutions requires a suitable green process engineered to take into account the extreme physicochemical conditions of cleaning while not altering the process efficiency. To this end, an innovative treatment process combining adsorption-coagulation with flocculation was tested on multiple recycling of acid and basic cleaning solutions. In-depth analysis of time-course evolutions was carried out in the physicochemical properties (concentration, surface tension, viscosity, COD, total nitrogen) of these solutions over the course of successive regenerations. Cleaning and disinfection efficiencies were assessed based on both microbiological analyses and organic matter detachment and solubilization from fouled stainless steel surfaces. Microbiological analyses using a resistant bacterial strain (Bacillus subtilis spores) highlighted that solutions regenerated up to 20 times maintained the same bactericidal efficiency as de novo NaOH solutions. The cleanability of stainless steel surfaces showed that regenerated solutions allow better surface wettability, which goes to explain the improved detachment and solubilization found on different types of organic and inorganic fouling.