Effects of supplementing lauric arginate and sorbic acid in a commercial coating on pathogen survival and quality of fresh peaches

Abstract

Commercial coatings for stone fruits improve the quality but have limitations in controlling incident foodborne pathogens during storage. The aim of this study was to evaluate the pathogen survival and quality of fresh peaches sprayed with a commercial stone fruit coating, supplemented with low level (0.05% v/v lauric arginate – LAE and 0.5% w per v sorbic acid) and high level (0.1% v/v LAE and 1.0% w per v sorbic acid) antimicrobials. The alkaline coating was adjusted to pH 6.0 based on an observed partial synergistic effect between LAE and sorbic acid. Fresh peaches were inoculated with Salmonella or Listeria monocytogenes cocktails and then sprayed with the coating. The fruits in open trays were stored in a walk-in refrigerator set at 0 °C and 85% relative humidity for 20 days or at 21 °C for 5 days. Quality evaluation followed the same protocol using uninoculated peaches. Gradual reductions in viable bacteria were observed for both pathogens. After storage at 0 °C, the control, low-level, and high-level antimicrobial treatments achieved a respective reduction of 0.41 ± 0.54, 1.20 ± 0.71, and 2.17 ± 0.53 log CFU per fruit for Salmonella, while the log reductions (2.34–2.66 log CFU per fruit) were similar for L. monocytogenes. Pathogen counts were similar in the coated peaches throughout storage at 21 °C. The antimicrobials in the coating reduced native fungi in peaches by 0.5–1.0 log CFU per fruit after storage at either temperature and did not significantly impact the total soluble solids, titratable acidity, pH, and weight loss of the peaches during storage. The results demonstrate that LAE and sorbic acid are options to control Salmonella in fresh peaches, but additional strategies are needed to inhibit L. monocytogenes.