Cleaning performance of stainless steel surfaces fouled with preheated starch-protein binary mixtures: Mechanical properties, removal mechanisms, and in-place cleaning

Abstract

In the food industry, deposits are often composed of multiple components and micro-structures for which removal may diverge from conventional cleaning protocols. Incomplete removal of those deposits may compromise hygiene of manufacturing lines and impact product quality. Here, we investigated the cleaning performance of model foulants made from mixtures of starch and protein adhered to stainless steel surfaces, assessing their viscoelastic properties, removal mechanisms, and cleaning effectiveness in response to different standard chemical treatments (pH 7 and pH 13) and cleaning temperatures (20 and 40 °C). Deposits displayed distinct viscoelastic behaviours under mechanical stress, affecting their removal mechanisms, especially during in-place cleaning. Young's modulus data correlated with the cleaning efficiency of the model foulants. Notably, a decrease in deposit hardness was associated with easier detachment from the metal surface for starch-rich deposits (P0 and P30, 100% and 70% starch gel respectively). In contrast, protein-rich deposits, particularly P80 (80% protein gel-20% starch gel), required greater removal forces. This was especially evident in the absence of chemical treatment, where P80 demanded more effort to be removed compared to all other deposits. The use of chemical treatment reduced the mechanical stress and removal work needed for cleaning, alkaline treatment being effective for most deposits. Alkaline cleaning was efficient at removing protein and starch-based foulants, especially for the sole protein or sole starch-containing deposits. However, P80 exhibited similar removal levels at both pH 7 and pH 13. Therefore, this research underscores the intricate removal mechanisms for starch-protein mixtures compared to single deposits, highlighting how variations in deposit composition over time during industrial processing can impact the efficiency of current Clean-in-Place (CIP) protocols.