Sanitizer applicability in a laboratory model strawberry hydrocooling system

• Survival of Lactobacillus on hydro and forced-air cooled strawberries was examined.
• Efficacy of antimicrobial compounds in reducing Lactobacillus levels was evaluated.
• Hydrocooling reduced Lactobacillus survival compared to forced-air cooling.
• HOCl and PAA reduced strawberry surface contamination during hydrocooling.

After harvest, strawberries are cooled to 2–5 °C, typically by forced-air cooling. Hydrocooling is an alternative method that ensures faster cooling and with the addition of various sanitizers can reduce the risk of microbial cross contamination. In this study, the effect of forced-air cooling and hydrocooling on the survival of Lactobacillus plantarum, a non-pathogenic, potential surrogate bacterium, was evaluated. Further, the efficacy of three antimicrobial compounds, sodium hypochlorite (HOCl, 100 μL/L), aqueous chlorine dioxide (ClO2, 5 μL/L) and peroxyacetic acid (PAA, 80 μL/L) in reducing Lactobacillus levels during strawberry hydrocooling was also investigated. The results indicated that the Lactobacillus population on forced-air cooled strawberries was not significantly different from untreated strawberries. Compared to forced-air cooling, hydrocooling significantly reduced Lactobacillus survival on inoculated intact strawberries, even in the absence of a sanitizer. The addition of ClO2 resulted in the least reduction in initial Lactobacillus levels (∼1 log CFU/mL), similar to those on strawberries hydrocooled without antimicrobials. The addition of HOCl or PAA to the hydrocooling water resulted in respective reductions of 2.5 log CFU/mL and 4.0 CFU/mL in the initial Lactobacillus levels, which continued to decrease throughout the sampling period. The results from this study indicate that antimicrobials HOCl and PAA are both effective in reducing surface contamination on strawberries during hydrocooling.