Effects of Elevated Hydrostatic Pressure against Mesophilic Background Microflora and Habituated Salmonella Serovars in Orange Juice

Abstract

With recent improvements in the commercial feasibility of high pressure pasteurization units, the technology is gaining rapid acceptability across various sectors of food manufacturing, thus requiring extensive validation studies for effective adoption. Various times (1 min to 10 min) and intensity levels (0 MPa to 380 MPa) of elevated hydrostatic pressure were investigated for decontamination of mesophilic background microflora and inoculated Salmonella in orange juice. Results were analyzed by GLM procedure of SAS using Tukey- and Dunnett-adjusted ANOVA, additionally the Kmax and D-values were calculated using best-fitted (maximum R2) model obtained by GInaFit software. At 380 MPa, for treatments of 1 min to 10 min, D-value of 1.35, and inactivation Kmax of 3.34 were observed for Salmonella serovars. D-values were 5.90 and 14.68 for treatments of 241 MPa and 103 MPa, respectively. Up to 1.01 and >7.22 log CFU/mL reductions (p < 0.05) of habituated Salmonella serovars at planktonic stages were achieved using application of pressure at 380 MPa for 1 min and 10 min, respectively. Mesophilic background microflora counts were reduced (p < 0.05) by 1.68 to 5.29 log CFU/mL after treatment at 380 MPa for 1 min and 10 min, respectively. Treatments below two minutes were less efficacious (p ≥ 0.05) against the pathogen and background microflora, in vast majority of time and pressure combinations.

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

“…The standard deviations of both neutralized and non-neutralized samples were ranging from 0.0 to 0.3. In addition to pH, temperature is another critical factor associated with pressure-based pasteurization validation studies [20]. In the current study, as discussed in the Section 2.2., the trials were conducted under precise control of temperature using a chamber that is covered by a steel jacket, mechanically connected to a circulating water bath with refrigeration.…”

“…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.…”

“…While an array of studies [12][13][14][15][16][17] are available investigating effects of nisin on enhancing the efficacy of thermal and nonthermal pasteurizations, there are limited studies to discuss the efficacy of this antimicrobial under elevated hydrostatic pressure and under precise control of temperature and intrinsic (e.g., water activity, nutrients, pH) and other extrinsic (e.g., relative humidity, presence of gases, activity and presence of competitor microorganisms) factors. This is primarily due to the fact that precision in controlling and monitoring the temperature of the pressure-based treatments has been a major challenge for academic and industrial high-pressure research in the last several decades [18][19][20].…”

“…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].…”

“…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]. Our study investigates synergism of nisin with high-pressure and thermal-assisted high-pressure pasteurizations of L. monocytogenes to assure microbial safety and economic feasibility of the pressure-based inactivation of this microbial pathogen of public health significance.…”