Development of a detergent with excellent sterilizing effect for fried product manufacturing equipment

Thick fried tofu is a popular Japanese dish made by frying fresh tofu in vegetable oil. Immediately after frying, it is general accepted that little microorganisms remain at the surface of the product. However, microbial contamination of 10⁵ CFU/g including spoilage bacteria were detected in some commercial thick fried tofu. One of the possible causes is microbial contamination of the factory production equipment downstream of frying.

 Our surveillance revealed that microorganisms ranging 6~14×10⁵ CFU/100 cm² were detected in the post-frying cooling machine and the following conveyor. After cleaning the equipment with a conventional detergent containing benzalkonium chloride and a common nonionic surfactant, the viable counts remained unchanged (4~18×10⁵ CFU/100 cm²). This fact suggested that the detergency against microorganisms was insufficient and that microorganisms might remain and accelerate food spoilage.

In this study, therefore, we formulated a new detergent by selecting a nonionic surfactant that can easily demonstrate the bactericidal effect of benzalkonium chloride. When the equipment was cleaned with the new formulation, microbial residues were reduced to 2×10³ CFU/100cm² (99.9% removal rate compared to the conventional detergent). The detergent also had excellent cleaning performance for oil dirt and was found to be effective in cleaning equipment at factories that produce fried products such as thick fried tofu. The detergent with excellent sterilization performance is expected to contribute to the SDGs by extending the shelf life of food and reducing food loss.