Reduction of Listeria monocytogenes and Salmonella Typhimurium on Blueberries through Brief Exposure to Antimicrobial Solutions Coupled with Freezing

This study evaluated the efficacy of different brief-exposure antibacterial washes (≤3 min) coupled with frozen storage against Listeria monocytogenes and Salmonella Typhimurium on blueberries. Inoculated berries where treated with sodium hypochlorite (NaOCl, 200 ppm), chlorine dioxide (15 ppm), ozone (3 and 5 ppm), or lactic acid (2%) for short exposure times (10 s, 1 min, or 3 min), and antibacterial effectiveness was determined with or without an additional freezing hurdle (−12°C, 1 week). Wash treatments alone resulted maximum log reductions from 1.0 to 2.8, while the additional freezing step increased this to a range from 3.7 to 6.6. The greatest reduction of L. monocytogenes (6.6 log) and Salmonella Typhimurium (5.3 log) was observed after freezing combined with 3 min of exposure to 2% lactic acid or 200 ppm of NaOCl, respectfully. After treatment, no residue was measured by the methodologies used. However, lactic acid treatment resulted in changes of color and aroma. In conclusion, wash treatments of blueberries using short exposure times had antimicrobial effectiveness (1.0 to 2.8 log reductions) and can be enhanced by coupling with freezing.