Effects of gamma irradiation on the survival of Pseudomonas fluorescens inoculated on romaine lettuce and baby spinach

- Survival of Pseudomonas fluorescens to gamma irradiation (D10) was assessed in broths, on romaine lettuce and baby spinach.
- At doses of 0.25, 0.50, 0.75, 1.0 kGy, D10 values were 0.09-0.12 kGy in broths and 0.04-0.06 kGy on spinach and on lettuce.
- Low irradiation doses are needed to inactivate P. fluorescens on produce.

Irradiation of fresh fruits and vegetables has been utilized as a post-harvest intervention measure to inactivate microbial pathogen on produce. The objectives of this research were to determine the survival (D10 values) of Pseudomonas fluorescens (Pf) strains 2-79, Q8R1, Q287, surface inoculated on baby spinach and romaine lettuce; and Pf strains suspended in buffer peptone water (BPW). Gamma irradiation doses of 0 (control), 0.25, 0.50, 0.75 and 1.0 kGy were applied on P. fluorescens inoculated on produce and stored for 24 h at 4 °C. On spinach and romaine lettuce, the D10 values of P. fluorescens ranged from 0.04 ± 0.01 to 0.05 ± 0.02 and from 0.05 ± 0.03 to 0.06 ± 0.03 kGy, respectively. Pf had high sensitivity to irradiation and its populations varied on spinach and on romaine lettuce. These results indicate that low irradiation values are required to inactivate Pf on produce resulting with low bacterial survival.