Numerical simulation and experimental validation of bacterial detachment using a spherical produce model in an industrial-scale flume washer

Abstract Thorough and proper washing of fresh produce is critical for ensuring their microbiological safety. Using spherical produce models (40 mm diameter), the effect of the separation distance (40 mm–200 mm) between adjacent models placed in the flow in an industrial flume washer, on bacterial detachment was investigated. The fluid flow in the flume washer was numerically simulated, and the shear stress on the surface of the produce models was calculated. The numerical simulation indicated that varying the center-to-center distance between produce models from 40 mm to 200 mm increased the average shear stress on the produce models from 264 mPas to 469 mPas. The corresponding experimental data of the number of bacteria that survived on the surface of the produce models after 60 s of washing ranged from 8.6 × 103 CFU/cm2 to 2.7 × 102 CFU/cm2. An empirical model, which incorporated the effect of calculated shear stress on the kinetics of bacteria removal, was developed to predict the number of bacteria that survived on the surface of the produce after washing. The findings in this study are useful for fresh-cut produce processors in optimizing product loading rate without compromising food quality and safety during flume washing.