Interactions of Carvacrol, Caprylic Acid, Habituation, and Mild Heat for Pressure-Based Inactivation of O157 and Non-O157 Serogroups of Shiga Toxin-Producing Escherichia coli in Acidic Environment

Abstract

The current study investigated synergism of elevated hydrostatic pressure, habituation, mild heat, and antimicrobials for inactivation of O157 and non-O157 serogroups of Shiga toxin-producing Escherichia coli. Various times at a pressure intensity level of 450 MPa were investigated at 4 and 45 °C with and without carvacrol, and caprylic acid before and after three-day aerobic habituation in blueberry juice. Experiments were conducted in three biologically independent repetitions each consist of two replications and were statistically analyzed as a randomized complete block design study using ANOVA followed by Tukey- and Dunnett’s-adjusted mean separations. Under the condition of this experiment, habituation of the microbial pathogen played an influential (p < 0.05) role on inactivation rate of the pathogen. As an example, O157 and non-O157 serogroups were reduced (p < 0.05) by 1.4 and 1.6 Log CFU/mL after a 450 MPa treatment at 4 °C for seven min, respectively, before habituation. The corresponding log reductions (p < 0.05) after three-day aerobic habituation were: 2.6, and 3.3, respectively at 4 °C. Carvacrol and caprylic acid addition both augmented the pressure-based decontamination efficacy. As an example, Escherichia coli O157 were reduced (p < 0.05) by 2.6 and 4.2 log CFU/mL after a seven-min treatment at 450 MPa without, and with presence of 0.5% carvacrol, respectively, at 4 °C.

Augmenting the Pressure-Based Pasteurization of Listeria monocytogenes by Synergism with Nisin and Mild Heat

“…Temperature values of the experiments were controlled by a water jacket made from stainless steel, covering the treatment chamber. The jacket was mechanically linked to a refrigerated circulating water bath (VWR International, Radnor, PA, USA, Model refrigerated 1160s), and temperature values were recorded by a t-type thermocouple (Omega Engineering Inc., Norwalk, CT, USA) as further detailed in our open access recent publications [20,21,25]. Pressure treatments occurred inside the PULSE tubes without disk (Pressure BioScience Inc., Easton, MA, USA) that contained 1.5 mL of inoculated PBS with or without presence of the antimicrobial.…”

“…The inactivation K max of the treatments were 1.26, 9.78, 2.35, and 2.10 ( Figure 4A-D). Both linear and nonlinear inactivation indices could provide adaptable information for stakeholders' assimilation, however, it is important to note that inactivation indices would need to be utilized and adapted with caution after studying the pathogen-product specific relationship to assure the most generalizable linear or nonlinear model had been selected [20][21][22].…”

“…High-pressure pasteurization is a nonthermal processing that is gaining further popularity in food manufacturing due to its ability to preserve the fresh-like qualities of the product while eliminating the microbial pathogens and spoilage microorganisms. Manufacturers currently rely on treatments typically lasting for 3 min at intensity levels up to 87,000 pound-force per square inch (600 MPa) [20,21]. Utilization of the treatments with intensity levels of less than 600 MPa could be of great importance to the manufacturers since low-intensity treatments could minimize the cost of the operation and provide a competitive market for pressure-treated products that currently have slightly higher operational costs relative to traditional heat-treated products [20].…”

Fate and Biofilm Formation of Wild-Type and Pressure-Stressed Pathogens of Public Health Concern in Surface Water and on Abiotic Surfaces

“…A four-strain mixture of L. monocytogenes (ATCC®numbers 51772, 51779, BAA-2657, and 13932), six-strain mixture of E. coli O157:H7 (ATCC®numbers BAA-460, 43888, 43894, 35150, 43889, 43890), and five-strain mixture of non-typhoidal Salmonella enterica serovars (ATCC®numbers 13076, 8387, 6962, 9270, 14028) were used in this study. The strains are selected based on preliminary data and their epidemiological and public health significance that are elaborated in detail in our recent open access publications [13][14][15][16]. These strain mixtures were used for inoculation of Cumberland river (Nashville, TN) water samples that were autoclaved for 15 min at 121 • C (MLS3781L-PA model, PHC Corporation of North America, Wood Dale, IL, USA).…”

“…While the effects of an array of stressors are investigated and reviewed in the literature [12], there is currently a knowledge gap for the assimilation of the effects of sub-lethal exposure to elevated hydrostatic pressure on the fate and biofilm formation of an array of microbial pathogens. This is of particular importance since the utilization of elevated hydrostatic pressure is gaining increasing importance and momentum in food manufacturing [13][14][15][16]. Information about the survival and biofilm formation of the pressure-stressed phenotype of the main microbial pathogens is critical to assure existing validation studies conducted using wild-type phenotypes are capable of controlling the pressure-stressed phenotypes of the pathogens as well.…”