Predicting the impact of temperature and relative humidity on Salmonella growth and survival in sliced chard, broccoli and red cabbage.

This study assessed the fate of a Salmonella enterica cocktail (S. Typhimurium, S. Enteritidis, S. Newport, S. Agona and S. Anatum; initial counts 3.5 log CFU/g) in minimally processed sliced chard, broccoli and red cabbage at 16 conditions of different temperature (7, 14, 21 and 37 °C) and relative humidity (RH; 15, 35, 65 and 95%) over six days (144 h). Linear regression was used to estimate the rate change of Salmonella in cut vegetables as a function of temperature and relative humidity (RH). R2 value of 0.85, 0.87, and 0.78 were observed for the rates of change in chard, broccoli, and red cabbage, respectively. The interaction between temperature and RH was significant in all sliced vegetables. Higher temperatures and RH values favored Salmonella growth. As temperature or RH decreased, the rate of S. enterica change varied by vegetable. The models developed here can improve risk management of Salmonella in fresh cut vegetables.

Ozone and photodynamic inactivation of norovirus surrogate bacteriophage MS2 in fresh Brazilian berries and surfaces.

This study assessed the efficacy of ozone (bubble diffusion in water; 6.25 ppm) and photodynamic inactivation (PDT) using curcumin (75 µM) as photosensitizer (LED emission 430-470 nm; 33.6 mW/cm2 irradiance; 16.1, 20.2, and 24.2 J/cm2 light dose) against the Norovirus surrogate bacteriophage MS2 in Brazilian berries (black mulberry and pitanga) and surfaces (glass and stainless steel). Contaminated berries and surfaces were immersed in ozonized water or exposed to PDT-curcumin for different time intervals. Transmission electron microscopy was used to assess the effects of the treatments on MS2 viral particles. The MS2 inactivation by ozone and PDT-curcumin varied with the fruit and the surface tested. Ozone reduced the MS2 titer up to 3.6 log PFU/g in black mulberry and 4.1 log PFU/g in pitanga. On surfaces, the MS2 reduction by ozone reached 3.6 and 4.8 log PFU/cm2 on glass and stainless steel, respectively. PDT-curcumin reduced the MS2 3.2 and 4.8 log PFU/g in black mulberry and pitanga and 2.7 and 3.3 log PFU/cm2 on glass and stainless steel, respectively. MS2 particles were disintegrated by exposure of MS2 to ozone and PDT-curcumin on pitanga. Results can contribute to establishing effective practices for controlling NoV in fruits and surfaces, estimated based on MS2 bacteriophage behavior.

Transfer of MS2 bacteriophage from surfaces to raspberry and pitanga fruits and virus survival in response to sanitization, frozen storage and preservation technologies.

This study assessed the norovirus (NoV) surrogate bacteriophage MS2 transfer from stainless steel, glass and low-density polypropylene surfaces to raspberry and pitanga fruits. The effect of sodium hypochlorite (100 ppm, 1 min) on MS2 survival on whole fruits, the MS2 survival in sanitized fruits and derived pulps during frozen storage, and in response to preservation technologies (heat, organic acids and salts) was also assessed. The highest (p < 0.05) viral transfer (%) was observed from glass and stainless steel (∼90%) to raspberry, and from glass and polypropylene (∼75%) to pitanga, after 60 min of contact. Sodium hypochlorite reduced (p < 0.05) MS2 titer by 3.5 and 3.8 log PFU/g in raspberry and pitanga, respectively. MS2 decreased (p < 0.05) up to 1.4 log PFU/g in frozen stored sanitized fruits (whole fruits and pulps) after 15 days, with no further changes after 30 days. Thermal treatments reduced MS2 titer (p < 0.05) in both fruit pulps. MS2 inactivation was higher in pitanga pulp. The addition of ascorbic acid, citric acid, sodium benzoate, or sodium metabisulfite had little effect (<1 log PFU/g) on MS2 concentration in either fruit. These results may inform NoV risk management practice in processing and handling of fruits.