Experimentally Implementing the Linear Nonisothermal Equation for Simultaneously Obtaining D- and z-Values of Salmonella Senftenberg in Skim Milk with a Differential Scanning Calorimeter.

Abstract: For bacteria with log-linear thermal inactivation kinetics in food, D-values are obtained in multiple isothermal inactivation experiments at different temperatures, and the z-value is obtained from these D-values. In a previous work, the cumulative lethality integral was mathematically solved in closed form when temperature in the food increased linearly with time. The solution revealed that each nonisothermal experiment could yield both D- and z-values, eliminating the need for getting multiple D-values to get a z-value.

Comparison of Commercial Test Kits for Detection of Salmonella and E. coli O157:H7 in Alfalfa Spent Sprout Irrigation Water.

Background: Sprout growers in the United States are required to test spent sprout irrigation water (SSIW) or in-process sprouts for Escherichia coli O157:H7 and Salmonella species. Pathogen screening kits are commercially available; however, few have been validated for analysis of sprouts or SSIW.

Objective: This study evaluated AOAC-certified test kits (lateral flow devices [LFDs], enzyme immunoassays [EIAs], and molecular assays) in comparison with culture methods described in the U.

Population Dynamics of Listeria monocytogenes, Escherichia coli O157:H7, and Native Microflora During Manufacture and Aging of Gouda Cheese Made with Unpasteurized Milk.

Abstract: Cheeses made with unpasteurized milk are a safety concern due to possible contamination with foodborne pathogens. Listeria monocytogenes and Escherichia coli O157:H7 have been implicated in several outbreaks and recalls linked to Gouda cheese made with unpasteurized milk. The U.

Short communication: Long-term -20°C survival of Listeria monocytogenes in artificially and process-contaminated ice cream involved in an outbreak of listeriosis.

Listeria monocytogenes was linked to an outbreak of foodborne illness associated with in-process contaminated ice cream in the United States from 2010 to 2015 that sickened 10 individuals and led to 3 deaths. Ice cream obtained from the outbreak was used in this study to examine the population dynamics of L. monocytogenes as in-process contaminants compared with artificially inoculated cells.

Effects of Package Atmosphere and Storage Conditions on Minimizing Risk of O157:H7 in Packaged Fresh Baby Spinach.

Packaged fresh spinach has been associated with outbreaks of illness caused by O157:H7. The purpose of this study was to assess the behavior of O157:H7 in packaged baby spinach in response to storage conditions of temperature and package atmosphere and including effects of inoculation level, spinach leaf damage (cut leaves), internalized or leaf surface contamination, exposure to hypochlorite sanitizer, and package size. Behavior of O157:H7 inoculated at 2 and 4 log CFU/g on spinach packaged in polymer bags composed of a two-layer laminate (polypropylene and polyethylene) and stored under atmospheres of 20% O-3% CO and 0% O-15% CO (aerobic and anaerobic, respectively) was assessed at 5, 7, 12, and 15°C for up to 14 days.

Metagenomics of pasteurized and unpasteurized gouda cheese using targeted 16S rDNA sequencing.

Background: The microbiome of cheese is diverse, even within a variety. The metagenomics of cheese is dependent on a vast array of biotic and abiotic factors. Biotic factors include the population of microbiota and their resulting cellular metabolism.

Growth Kinetics in Milkshakes Made from Naturally and Artificially Contaminated Ice Cream.

This study assessed the growth of in milkshakes made using the process-contaminated ice cream associated with a listeriosis outbreak in comparison to milkshakes made with artificially contaminated ice cream. For all temperatures, growth kinetics including growth rates, lag phases, maximum populations, and population increases were determined for the naturally and artificially derived contaminants at 5, 10, 15, and 25°C storage for 144 h. The artificially inoculated presented lower growth rates and shorter lag phases than the naturally contaminated populations at all temperatures except for 5°C, where the reverse was observed.

Quantitation of viable Coxiella burnetii in milk using an integrated cell culture-polymerase chain reaction (ICC-PCR) assay.

The obligate intracellular pathogen Coxiella burnetii has long been considered the most heat resistant pathogen in raw milk, making it the reference pathogen for determining pasteurisation conditions for milk products. New milk formulations and novel non-thermal processes require validation of effectiveness which requires a more practical method for analysis than using the currently used animal model for assessing Coxiella survival. Also, there is an interest in better characterising thermal inactivation of Coxiella in various milk formulations.

Thermal resistance of Listeria monocytogenes Scott A in ultrafiltered milk as related to the effect of different milk components.

Pasteurization parameters for grade A milk are well established and set by regulation. However, as solids levels increase, an increased amount of heat is required to destroy any pathogens present. This effect is not well characterized.

Modification of the submerged coil to prevent microbial carryover error in thermal death studies.

A submerged coil unit generates death rate data for foodborne pathogens through precise computer-controlled sequential sampling rather than the usual manually timed, labor-intensive single sampling associated with other approaches. Our work with Yersinia pseudotuberculosis and Listeria monocytogenes Scott A using the submerged coil unit indicated non-log-linear death rates with large degrees of tailing. Varying degrees of cell adhesion to the surface of the exit port resulted in carryover that was likely the primary cause of these non-log-linear kinetics.