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Infection with human norovirus (HuNoV) is considered a common cause of foodborne illness worldwide. Foodborne HuNoV outbreaks may result from consumption of food contaminated by an infected food handler in the foodservice environment, in which bare-hand contact, lack of hand washing, and inadequate cleaning and disinfection are common contributing factors. The goal of this study was to examine cross-contamination of a HuNoV surrogate, murine norovirus (MNV-1), during common procedures used in preparing fresh produce in a food service setting, including turning water spigots, handling and chopping Romaine lettuce, and washing hands. MNV-1 transfer % was log-transformed to achieve a normal distribution of the data and enable appropriate statistical analyses to be performed. MNV-1 transfer coefficients varied by surface type, and a greater affinity for human hands and chopped lettuce was observed. For example, greater transfer was observed from a contaminated stainless steel spigot to a clean hand (24% or 1.4-log transfer %) compared to transfer from hand to spigot (0.6% or -0.2-log transfer %). During the chopping of Romaine lettuce, MNV-1 was transferred from either a contaminated cutting board (25% or 1.4-log transfer %) or knife (~100% or 2.0-log transfer %) to lettuce at a significantly greater rate (p>0.05) than from contaminated lettuce to the board (2.1% or 0.3-log transfer %) and knife (1.2% or 0.06-log transfer %). No significant difference (p>0.05) in MNV-1 transfer coefficients was observed between bare hands and Romaine lettuce during handling. For handwashing trials, only one hand was inoculated with MNV-1 prior to washing. The handwashing methods included rubbing hands under tap water for at least 5s (average 2.8-log reduction) or washing hands for at least 20s with liquid soap (average 2.9-log reduction) or foaming soap (average 3.0-log reduction), but no statistical difference between these reductions was achieved (p>0.05). Despite the reductions of MNV-1 observed, residual virions were detected on both hands after washing in every replicate trial. This observation reveals that virions are transferred from one hand to the other during washing with and without soap. Each transfer scenario was repeated at least 9 times, and the data gathered indicate that MNV-1 transfers readily between common surfaces during food preparation. These data are important for the development of quantitative risk analyses, and will assist in the development of appropriate intervention strategies for enteric viruses in food preparation.

In published data the thermal destruction of Salmonella species in peanut butter deviates from pseudo-first-order kinetics. The reasons for such deviation are unknown. This study examined both the method used to measure the thermal destruction rate and the method of growth of the microorganisms to explain variations in destruction kinetics. Growth on a solid matrix results in a different physiological state that may provide greater resistance to adverse environments. In this study, Salmonella Tennessee and Oranienburg were grown for 24 h at 37°C under aerobic conditions in broth and agar media to represent planktonic and sessile cell growth, respectively. Peanut butter was held at 25°C and tested for Salmonella levels immediately after inoculation and at various time intervals up to 2 weeks. Thermal resistance was measured at 85°C by use of a newly developed thin-layer metal sample holder. Although thermal heat transfer through the metal device resulted in longer tau values than those obtained with plastic bags (32.5 ± 0.9 versus 12.4 ± 1.9 s), the bags have a relative variability of about 15 % compared with about 3 % in the plates, allowing improved uniformity of sample treatment. The two serovars tested in the thin-layer device showed similar overall thermal resistance levels in peanut butter regardless of growth in sessile or planktonic states. However, thermal destruction curves from sessile cultures exhibited greater linearity than those obtained from planktonic cells (P = 0.0198 and 0.0047 for Salmonella Oranienburg and Salmonella Tennessee, respectively). In addition, both Salmonella serovars showed significantly higher survival in peanut butter at 25°C when originally grown on solid media (P = 0.001) with a1-log loss over 2 weeks as opposed to a 1- to 2-log loss when grown in liquid culture. Consequently, the use of cells grown on solid media may more accurately assess the survival of Salmonella at different temperatures in a low-water-activity environment such as peanut butter.

High pressure processing (HPP) inactivation data were obtained for hepatitis A virus (HAV) suspended in buffered growth medium containing salt at either 15 or 30 g/liter. Pressures between 300 and 500 MPa were applied for treatment times of 60 to 600 s. In medium containing 15 g/liter salt, the HAV titer was reduced by approximately 1 and 2 log 50% tissue culture infectious dose units (TCID50) per ml after 600 s of treatment with 300 and 400 MPa, respectively. Under the same treatment conditions but in medium containing 30 g/liter salt, HAV was reduced by0.50 log TCID50/ml. HAV was inactivated by3 log TCID50/ml after treatment with 500 MPa for 300 and 360 s in medium containing 15 and 30 g/liter salt, respectively. Weibull and log-linear models were fitted to inactivation data. Individual Weibull curves generally provided a good fit at each pressure and salinity, but the curve shapes were qualitatively inconsistent between treatments, making interpolation between pressures difficult and unreliable. High variability was observed in the inactivation data, but the log-linear model described the entire data set and interpolated between specific treatment conditions. Therefore, this model was evaluated by using high pressure to treat HAV artificially inoculated into Pacific oyster (Crassostrea gigas) homogenate adjusted to 15 or 30 g/liter salinity. The log-linear model generally provided fail-safe predictions at pressuresor = 375 MPa and may aid shellfish processors wishing to incorporate HPP into an oyster processing regime. Additional inactivation data with greater reproducibility should be collected to enable expansion of the model and to increase the accuracy of its predictions.

The overall safety of a food product is an important component in the mix of considerations for processing, distribution, and sale. With constant commercial demand for superior food products to sustain consumer interest, nonthermal processing technologies have drawn considerable attention for their ability to assist development of new products with improved quality attributes for the marketplace. This review focuses primarily on the nonthermal processing technology high-pressure processing (HPP) and examines current status of its use in the control and elimination of pathogenic human viruses in food products. There is particular emphasis on noroviruses and hepatitis A virus with regard to the consumption of raw oysters, because noroviruses and hepatitis A virus are the two predominant types of viruses that cause foodborne illness. Also, application of HPP to whole-shell oysters carries multiple benefits that increase the popularity of HPP usage for these foods. Viruses have demonstrated a wide range of sensitivities in response to high hydrostatic pressure. Viral inactivation by pressure has not always been predictable based on nomenclature and morphology of the virus. Studies have been complicated in part from the inherent difficulties of working with human infectious viruses. Consequently, continued study of viral inactivation by HPP is warranted.