Salmonella inactivation and rapid cooling of fresh cut apples by plasma integrated low-pressure cooling.

Fresh food products, including fruits, vegetables, raw meat, and poultry, have been associated with safety concerns and quality issues, owing to their susceptibility to rapid deterioration and microbial contamination. This research aimed to develop an integrated process to simultaneously cool and decontaminate high moisture food products. Cold plasma (CP), a novel decontamination technology, was integrated with vacuum cooling to develop a plasma integrated low-pressure cooling (PiLPC) process. To evaluate the rapid cooling and microbial inactivation efficacies of the PiLPC process, fresh cut Granny Smith apples andSalmonella entericaserovarTyphimurium ATCC 13311 were used as the model food and microorganism, respectively. The influence of process parameters including treatment time, pressure, and post-treatment storage, on the inactivation ofSalmonellaon fresh-cut apples was investigated.Inactivation ofSalmonellaincreased with treatment time, with a maximum reduction of 3.21 log CFU/g after 5 min of CP treatment at atmospheric pressure. Inactivationof Salmonellaafter CP treatment at 200 mbar was not significantly different from that at atmospheric pressure for the same treatment time. CP treatment of 3 min at 200 mbar followed by a post-treatment storage of 3 days at 4 °C reduced the totalSalmonellapopulation on cut apple slices by > 6 log CFU/g. The temperature of the cut apples was reduced from room temperature to 2 °Cin 3 to 9 min depending on the sample surface area to volume ratio, when the pressure was reducedto 7 mbar. However, this PiLPC process resulted in moisture loss in cut apples. The results of this study indicate the potential of the PiLPC process for rapid cooling and microbial inactivation of fresh food products in a single process.

Influence of water activity on the heat resistance of Salmonella enterica in selected low-moisture foods.

Low-moisture foods (LMF with water activity, aw < 0.85) including pet foods and black pepper powder have consistently been associated with foodborne disease caused by Salmonella enterica. Increased heat resistance and prolonged survival at low-moisture conditions, however, remain major challenges to achieve effective inactivation of Salmonella in low-moisture foods. At low water activity (aw) conditions, heat resistance of Salmonella is greatly enhanced when compared to high aw conditions. This study aimed to quantify the effect of aw on the heat resistance of Salmonella enterica in pet food pellets and black pepper powder. Pet food pellets were inoculated with two strains of heat resistant S. enterica and black pepper powder was inoculated with a 5-strain cocktail of Salmonella. Both inoculated food samples were equilibrated at 0.33, 0.54, and 0.75 aw in controlled humidity chambers. Inoculated pet food pellets and black pepper powder in closed aluminum cells were heat treated at specific temperatures for selected times. The results showed that the Weibull model fitted well the inactivation data. At a specific temperature, the rate of inactivation increased with the increase in the aw from 0.33 to 0.75, and the 3-log reduction times decreased for Salmonella in both food samples with the increase in aw. Water adsorption isotherms of pet food pellets and black pepper powder at initial and treatment temperatures were developed to understand the change in aw during heat treatments. The change in aw during heat treatment was dependent on the type of food matrix, which possibly influenced the thermal inactivation of Salmonella in pet food pellets and black pepper powder. The quantitative analysis of heat reduction of Salmonella with respect to aw aids in selection of the appropriate initial aw to develop effective heat treatment protocols for adequate reduction of Salmonella in pet foods and black pepper powder.