Ultrasonic cleaning applications in dairies: Case studies on cheese moulds and milk transportation crates

Purpose - The purpose of these studies was to investigate the cleaning and hygiene of plastic cheese moulds and plastic transportation crates and to assess the suitability of ultrasonication for cleaning these dairy devices on a pilot scale and to optimise these cleaning procedures. Design/methodology/approach - The contamination load in the various process lines was monitored by use of chemical methods, i.e. EDTA titration and COD measurement for organic residues and various microbiological techniques for microbial contaminants. Ultrasonication cleaning procedures for cheese moulds were planned among parameters applicable to the process environment. The Taguchi method design of experiments was also used for the cleaning of milk transportation crates. Findings - Ultrasonication was found to be a suitable cleaning method for both cheese moulds and transportation crates. Acceptable cleaning results were achieved using short cleaning procedures with a temperature under 60 degrees C. Various types of cleaning agents can be used together with ultrasonication and the plastic materials in the utensils tolerated ultrasonication. The quality and the efficacy of the cleaning liquid used in the ultrasonic bath in the dairy plant were rapidly diluted due to the accumulation of organic soil. To ensure the effectiveness of cleaning, the quality of cleaning liquid should be measured frequently and threshold limits for changing the cleaning liquid should be set. The COD measurement proved to be practical for monitoring the organic load of the cleaning liquid and traditional culturing, as well as commercial culturing applications, e.g. Petrifilm AC and DryCult TPC can easily be used for monitoring the level of microbial contamination. Research limitations/implications - No major limitations, apart from the required investments, were found for applying the ultrasonication in the cleaning of dairy devices, e.g. plastic cheese moulds and plastic milk transportation crates. Originality/value - The work is of value in highlighting the potential use for ultrasonication in improving the cleaning procedure of returnable milk transportation crates made of plastic.