Dipping fresh-cut apples in citric acid before plasma-integrated low-pressure cooling improves Salmonella and polyphenol oxidase inactivation.

BACKGROUND: Ready-to-eat fruit and vegetable products have gained tremendous popularity in recent years. The main challenges associated with these minimally processed products are their short shelf life and high food safety concerns. In this study, our goal was to develop an integrated process to both reduce the Salmonella population by >5 log CFU g-1 ) and to reduce polyphenol oxidase activity, followed by quickly cooling the product. We compared the effect of a sequential treatment of dipping in citric acid (CA) followed by cold plasma (CP) treatment on the inactivation of Salmonella Typhimurium, polyphenol oxidase (PPO) activity, browning, total phenolic content and the moisture loss of cut apples during the plasma-integrated low-pressure cooling (PiLPC) process. RESULTS: The greatest inactivation of Salmonella (5.68 log CFU g-1 ) and the highest PPO inactivation (78%) were observed after dipping cut apples in 5% CA, followed by 3 min of CP treatment. The color of cut apples remained relatively unchanged, with a fresh-like appearance during 7 days of storage at 4 °C after this combined treatment. Although the low-pressure cooling time was increased when samples were pre-dipped in CA, related to those undipped, the moisture loss was reduced by more than 50% during the PiLPC process. No significant reduction in phenolic content was observed during the PiLPC when the samples were pre-dipped in 5% CA. CONCLUSION: These results indicate the potential of this integrated process for the inactivation of endogenous food enzymes and bacterial pathogens in fresh-cut apples. © 2021 Society of Chemical Industry.

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.