Modeling the UV-C Inactivation Kinetics and Determination of Fluence Required for Incremental Inactivation of Cronobacter spp.

ABSTRACT: A study was undertaken to model the UV-C inactivation kinetics and determine the fluences required for the incremental inactivation of several strains of Cronobacter spp. suspended in clear phosphate-buffered saline (PBS). In total, 13 strains of Cronobacter spp. were individually suspended in PBS and treated with UV-C doses of 0, 2, 4, 6, 8, and 10 mJ cm-2 with a collimated beam device emitting UV-C at 253.7 nm. The log reduction from each treatment was identified using the plate count method and plotted against the UV-C dose and then curve fitted using several mathematical models. The UV-C dose required for incremental inactivation of each isolate was determined using both linear and nonlinear regression. For the 13 strains tested, a UV-C dose of 10 mJ cm-2 inactivated between 3.66 ± 0.101 and 5.04 ± 0.465 log CFU mL-1. The survival behavior of all strains was best fitted to the Weibull+tail model, with correlation coefficients between 97.17 and 99.71%, and was used to determine the fluences required for incremental inactivation. The UV-C fluences needed to inactivate 1 log (D10-value) of Cronobacter spp. in buffer were between 3.53 and 5.50 mJ cm-2, whereas a fluence greater than 6.57 mJ cm-2 was required to achieve a 4-log inactivation. A clear understanding of the UV-C dose-response of several strains of Cronobacter spp. lays the foundation to design effective UV-based disinfection systems.

The use of high pressure processing to compensate for the effects of salt reduction in ready-to-eat meat products.

Sodium chloride is an essential ingredient in meat products, where it is not only used as a flavoring agent but also to achieve desired textural properties and as an antimicrobial to improve its safety and extend shelf-life. Although NaCl plays this multi-functional role in meat products, excessive sodium intake is linked to various negative health consequences such as cardiovascular disease and obesity. Sodium chloride added to ready-to-eat meat products is the largest contributor of sodium. Thus, there is an increased interest in the development of meat products with reduced sodium levels. Strategies to reduce sodium include identification of alternatives to sodium, considering safety and functionality, and including technological innovations and alternative food processing strategies. Several studies have shown that high pressure processing (HPP) can partially compensate for the loss in functional and sensory properties of meat products as a result of NaCl reduction. This review summarizes these studies to date and will highlight the ability of HPP to enhance the safety, shelf-life and quality of sodium-reduced meat products.

Effect of cranberry pomace on the physicochemical properties and inactivation of Salmonella during the manufacture of dry fermented sausages.

The effect of cranberry pomace (CP) incorporation on S. enterica serovars inactivation, starter culture population, and physicochemical properties of sausages during the manufacture of dry fermented sausages (DFS) was studied. Sausages containing a five-strain cocktail of S. enterica serovars at 7-log CFU/g, with different levels of CP (control, 0%; low, 0.55%; medium, 1.70%; high, 2.25% wt/wt), or liquid lactic acid (0.33% vol/wt, LA) were subjected to typical fermentation and drying conditions. A significant (P < 0.05) reduction in initial pH was observed in all CP treatments on day 0 as a result of CP native acidity. All treatments except low CP showed a significantly lower pH than the control throughout the study. Water activity (aw) was not significantly affected by CP level during fermentation. However, sausages containing medium and high CP levels showed a significantly lower final product aw than the control. DFS with CP exhibited a significantly (P < 0.05) faster and greater Salmonella inactivation during the first 5 days; reduction rate and level directly correlated to CP level. In the presence of medium and high levels of CP, Staphylococcus spp. growth was suppressed, while Lactobacillus spp. and Pediococcus spp. exhibited a stimulatory response. All treatments except low CP had no significant effect on product chemical composition, and Moisture Protein ratio (MPr). Low CP level yielded DFS with a slightly higher (P < 0.05) moisture content and MPr. Medium and high CP levels resulted in darker, duller and redder DFS with a softer texture. Findings suggest that low CP levels can be utilized by DFS manufacturers as a natural functional ingredient to further minimize the risk associated with Salmonella during DFS production without altering final product characteristics.

Use of 2-hydroxy-4-(methylthio)-butanoic acid to inhibit Salmonella and Listeria in raw meat for feline diets and palatability in domestic cats.

While the raw pet food market continues to grow, the risk of bacterial contamination in these types of diets is a major concern, with Salmonella enterica and Listeria monocytogenes being the most frequently associated pathogens in raw pet food product recalls. dl-Methionine is included in some commercial feline kibble and canned diets to improve protein quality; however, an alternative to this is a liquid methionine supplement, 2-hydroxy-4-(methylthio)-butanoic acid (HMTBa), which is also an organic acid. 2-Hydroxy-4-(methylthio)-butanoic acid has previously demonstrated similar efficacy to formic acid against pathogens in a liquid environment and may be a good candidate to inhibit S. enterica and L. monocytogenes in raw ground meat. First, the minimum inhibitory concentration and minimum bactericidal concentration of HMTBa against these pathogens under laboratory growth conditions were determined by measuring growth of pathogens over 36 h when exposed to 10 concentrations of HMTBa (0.10% to 1.00%) mixed with tryptic soy broth. 2-Hydroxy-4-(methylthio)-butanoic acid included at ≥0.50% was bactericidal to S. enterica and L. monocytogenes (P < 0.05). Next, five levels of HMTBa (0.50% to 1.25%) were included in raw ground meat mixtures inoculated with cocktails of S. enterica or L. monocytogenes, and contamination levels were determined at four timepoints: immediately, and after refrigerated storage (4 °C) at 24, 48, and 72 h after removal from freezer (24 h at -20 °C). 2-Hydroxy-4-(methylthio)-butanoic acid included as 1.25% of the meat mixture reduced S. enterica and L. monocytogenes compared with the control (P < 0.05); however, it did not result in total kill of either of these pathogens. Following this, feeding behaviors of seven domestic cats were assessed when offered a raw chicken diet treated with or without 1.25% HMTBa for 5 d each, after which a 2-d 2-choice preference test was conducted. Cats demonstrated a preference for raw diets without HMTBa, but still readily consumed diets with 1.25% HMTBa, suggesting that such a diet was still palatable to them.