No abstract

Control of on sprouts is crucial for food and consumer safety. In this study, natural microflora on soybean seed was assessed and effects of gaseous chlorine dioxide (ClO) and biocontrol on the survival of on soybean sprouts were evaluated. Sprouts were dip-inoculated with prior to the application of the biocontrol ( and ). After inoculation with, the sprouts were treated with ClO at 0.4 mg/L for 1 h (90% R.H., 13°C). and were recovered on Pseudomonas Agar F (PAF) and xylose lysine tergitol-4 (XLT-4) media, respectively. strains reduced by <1 log colony forming units (CFU)/g of sprouts, whereas on soybean sprouts was reduced from 2.55 to 5.35 logs CFU/g by ClO. Gaseous ClO treatment reduced by 3.90 (0 h), 4.47 (24 h), and 3.61 log CFU/g (168 h). It was concluded that ClO and biocontrol treatment can enhance sprout safety.

The antimicrobial activity of a new nisin-based organic acid sanitizer (NOAS), developed in our laboratory, was tested against viable aerobic mesophilic bacteria and Salmonella populations inoculated on produce surfaces. The activity of NOAS was compared with 200 ppm of chlorinated wash water and a bioluminescence ATP technique to determine the efficacy of treatments compared with plate count methods. The activity of the 10% final concentration of NOAS against viable populations of 109 CFU/mL Salmonella in phosphate-buffered saline (PBS), sterile deionized distilled water, and buffered peptone water was tested in vitro and on grape tomatoes inoculated with Salmonella at 2.5 log CFU/g. A similar batch of inoculated tomatoes were treated with 200 ppm of total available chlorinated water. All treatments for inactivation of viable Salmonella in vitro was tested up to 30 min and 5 min for the attached populations on tomatoes. Inactivation of viable Salmonella at 109 log CFU/mL by 10% the NOAS solution averaged &gt;107 log CFU/mL in PBS, sterile deionized distilled water, and buffered peptone water. Similarly, Salmonella bacteria inactivated on tomato surfaces by the NOAS solution was significantly (P &lt; 0.05) greater than numbers on chlorinated washed tomatoes, and surviving bacterial populations on NOAS and chlorine-treated tomatoes were &lt;1 and 4 CFU/g, respectively. A significant linear correlation coefficient (r2 = 0.99) between the bioluminescence ATP assay and aerobic plate counts of inoculated and untreated grape tomatoes were recorded but not with NOAS and chlorine-treated tomatoes, as bacterial populations were less than the minimum baseline for determination. Also, the results indicated that the NOAS solution is a better alternative antimicrobial wash solution than 200 ppm of chlorinated water. HIGHLIGHTS

Occurrences and contamination of Salmonella enterica on produce are a significant food safety issue. The objective of this research was to evaluate the effects of low‐dose gamma radiation on survival and reductions of S. enterica on postharvest carrot and tomato. Irradiation treatments of 0–1 kGy were applied on produce, following pathogen inoculations in replicated experiments. The effects of temperatures (5 and 20°C) and storage times (0, 3, and 7 days) on pathogen reductions were determined. The mean Salmonella populations in untreated control produce varied from 7.12 ± 0.05 to 7.54 ± 0.12 log Cfu/g of produce. Pathogen reductions by gamma radiation were significant (p < .05) and varied with storage times (0–7 days). Salmonella populations were reduced on carrot by 4.3 logs (5°C) and 3.7 logs (20°C) at 1 kGy treatment. On tomato, pathogen reductions at 1 kGy did not differ significantly (p > .05) and were 5.6 and 5.8 logs at 5 and 20°C, respectively. Linear decreases in Salmonella populations occurred as radiation dosage increased. Injury of bacterial cells from radiation treatment was comparatively greater at 1 kGy than other treatments. Low‐dose gamma radiation treatment resulted in significant Salmonella reductions on produce and enhanced postharvest safety of carrot and tomato.

Assessment of pathogen survival is important for food safety. Listeria monocytogenes causes significant produce and food contamination worldwide. The objective of this research was to assess survival and reduction of L. monocytogenes on postharvest carrot and tomato subjected to low-dose radiation at different storage temperatures and times. Radiation levels of 0, 0.25, 0.50, 0.75, and 1 kGy were applied on produce inoculated with L. monocytogenes. Gamma radiation reduced Listeria populations by 5.9 logs on carrot and 3.9 logs on tomato at 3 days of storage (5 °C), while reductions were 4.4 and 4.0 logs on carrot and tomato, respectively; at 7 storage days (5 °C). At 20 °C, Listeria reductions were 2.8 logs on carrot and 4.2 logs on tomato (3 storage days) and pathogen decreases were 2.2 logs on carrot and 2.9 logs on tomato (7 storage days). Although pathogen reductions by radiation treatment varied with storage temperatures and days, the linear decreases were significant as the dosage increased from 0.25 to 1.0 kGy, implying that treatments were efficacious for pathogen inactivation. As low dose gamma radiation (1 kGy) showed substantial reduction of Listeria monocytogenes on fresh carrot and tomato, thus, use of low dose low dose gamma radiation can improve the post-harvest safety of carrot and tomato.