Suppressive Mechanism of Benzalkonium Chloride-Bactericidal Activity in the Presence of Oil

Cleaning and sterilization are critical Prerequisite Programs in sanitation management based on HACCP. Most food factories clean and sanitize equipment daily after production using detergents containing benzalkonium chloride (BAC). However, in factories that produce oil and fat-rich foods, it has been discovered that microbes can persist on production equipment. Insufficient cleaning protocols may result in secondary contamination of the final products. Unfortunately, there are limited cleaning agents available that are effective in sterilizing microbes in the presence of oil. Moreover, there is a lack of research on the bactericidal mechanisms and bacterial dynamics in oily environments. In this study, we aimed to reduce bacterial contamination on equipment in such factories by hypothesizing that oil diminishes BAC's bactericidal activity. We conducted lab-scale experiments simulating actual factory conditions to examine the effects of oil on BAC's efficacy. Additionally, we investigated the effect of nonionic surfactants, which are known to enhance BAC's bactericidal activity in oil-free conditions, in the presence of oil. The results showed that BAC's bactericidal activity was significantly reduced in the presence of oil. However, the activity was restored by adding an appropriate amount of secondary alcohol ethoxylate (sec-AE). Microscopic observations revealed that bacteria tended to accumulate at the water/oil interface, suggesting that the oil interface might inhibit BAC from effectively attacking the bacteria. The addition of sec-AE appeared to disperse the bacteria into the water layer, thus restoring BAC's bactericidal activity in the presence of oil. These findings are crucial for improving daily cleaning and sterilization processes in food factories operating in high-oil environments to prevent secondary contamination and enhance food safety.