A new test method for in-place cleanability of food processing equipment

A practical and quantitative method for assessing complex food equipment cleanability is described. After soiling a positive displacement pump by a composite model food made of custard and Bacillus cereus spores isolated from a food processing line, a mild cleaning-in-place procedure was carried out using basic detergents such as sodium hydroxide and nitric acid. After cleaning, surfaces potentially in contact with the contaminated food were overlaid with nutrient agar containing a tetrazolium salt. Residual contaminants appeared as small red colonies and contamination levels could be defined. A non-parametric statistical analysis was performed to compare the different areas in the pump and three cleanability levels were defined. Geometry appeared to be one of the main factors in hygiene, emphasised by the way the equipment is connected to the CIP circuit.

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