Occurrence and control challenges of biofilm-forming bacteria in industrial fresh produce processing

Microbial contamination remains a major challenge in industrial fresh produce processing, despite rigorous washing and sanitation procedures, and contribute to product spoilage and losses. The objective of this study was to characterize cultivable bacteria associated with industrial-scale processing of frozen fresh vegetables and to assess their biofilm-forming capability as well as their tolerance to commonly used disinfectants and to heat treatment under industry relevant conditions. Equipment surfaces, wash water and products were collected from operating commercial processing facility. A total of 153 bacterial isolates were identified by Sanger sequencing. Among these isolates, 27% were classified as strong producers of biofilm, 32% as moderate producers and 41% as weak producers. Susceptibility testing of strong biofilm-producing isolates showed that approximately 13% were susceptible to both sodium hypochlorite (70 ppm) and peracetic acid (0.05% w/v), 7% were susceptible to only one of the two disinfectants, and 80% did not achieve a more than 3-log reduction in viable counts under the conditions tested. In contrast, heat treatment representative of commercial blanching was effective at eliminating all tested strong biofilm producers in the planktonic state. Overall, these finding highlight the prevalence of biofilm-forming bacteria in industrial fresh produce processing environments and illustrate limitations of commonly used disinfectant against established biofilms. The results underscore the importance of optimizing sanitation strategies and biofilms-control approaches under industrial processing conditions. IMPORTANCE: Biofilms formed by bacteria in produce-processing environments pose a persistent challenge to sanitation and can contribute to product spoilage and losses. This study demonstrates that a substantial proportion of bacteria isolated from an industrial frozen fresh vegetable producing facility are capable of forming biofilms and exhibit limited susceptibility to commonly used disinfectants under industry-relevant conditions. The observation that heat treatment was effective against all tested isolates between biofilm-associated and free-living bacterial tolerance. By focusing on native bacterial isolates recovered directly from an operating processing facility, this work provides practical insight into biofilm persistence and sanitation limitations in industrial fresh produce processing. These findings are relevant for optimizing hygiene strategies and improving microbial control in commercial produce-processing environments.