Synergistic effects of combined ultrasound and peroxyacetic acid treatments against Cronobacter sakazakii biofilms on fresh cucumber

- 60 min US + 200 ppm PAA has additional 1.63 log-reduction of C. sakazakii biofilms in cucumber.
- 60 min US + 150-200 ppm PAA has 1.03-1.08 log-synergistic values of C. sakazakii biofilms in cucumber.
- Hunter colors, moisture contents, and texture in cucumber did not differ compared with US or PAA alone.
- 60 min US + 150-200 ppm PAA enhance the microbial safety of produces without changes in food qualities.

This study investigated the synergistic effects of combined ultrasound (US; 37 kHz, 380 W for 10-60 min) and peroxyacetic acid (PAA; 50-200 ppm) on reducing Cronobacter sakazakii biofilms on cucumbers. US was not sufficient to eliminate C. sakazakii biofilms (0.04-0.60 log-reduction), whereas PAA (200 ppm) significantly (p < 0.05) reduced biofilm formation on cucumber (0.89-1.88 log reduction). Furthermore, the combination of 60 min US and 200 ppm PAA resulted in an additional 1.63 log-reduction of C. sakazakii biofilms (3.51 log-reduction = 1.88 + 1.63 log). Synergistic reduction of C. sakazakii biofilms was observed in most combined treatment, although the most synergistic reduction values were <1.0 log10  CFU/cm2. The highest synergistic value of reduction in cucumber was 1.03-1.08 log10  CFU/cm2 when treated with a combination of 60 min US and 150-200 ppm PAA. In addition, the Hunter color(“L”, “a”, and “b”), moisture contents(%), and texture(hardness and chewiness) after combined treatment with 60 min US and 200 ppm PAA did not differ significantly from those of cucumbers exposed to a single treatment. These results indicate that combined treatment with 60 min US and 150-200 ppm PAA could be a useful approach to reduce C. sakazakii biofilms on fresh-produce and could help enhance their shelf-life during transportation and storage.