Factors affecting the adhesion of flour particles to stainless-steel surfaces and vacuum dry-cleaning.

Recent outbreaks and recalls linked to flour-based products have highlighted the need for improved cleaning methods in low-moisture environments. The factors affecting adhesion forces of flour particles, and the vacuum cleaning methodologies to overcome these forces, need to be better understood. The objectives of this study were to: (1) Measure electrostatic charge build-up in flour under different environmental conditions (20, 40, 60% relative humidity at room temperature), (2) quantify how powder size (US standard No. 60 - 80 or 80 - 100 mesh), electrostatic charge (charged and uncharged), and relative humidity impact the force required to remove the powder from an electropolished 304 stainless steel coupon (8 × 8 × 0.2 cm), and (3) determine the most effective vacuum nozzle angle (0, 45, 90° relative to the surface) for cleaning. Chargeability (nC) of flour samples was assessed using Faraday cup electrometry, while the surface adhesion force of the flour particles was measured using a custom-built impact tester. The surface cleanliness after vacuum treatments was assessed using ATP (adenosine triphosphate) swabs and a luminometer. Charged flour samples at 20% relative humidity (RH) exhibited a significantly higher charge compared to those at 40 and 60% RH. Within the 60 - 80 mesh range, charged flour showed higher adhesion rates than uncharged samples at both 20 and 40% RH. However, in the 80 - 100 mesh range, charged flour did not show a significant difference in adhesion when compared to uncharged samples at any RH level. Additionally, at 60% RH, surface residues measured by ATP were significantly lower for vacuum angle 90° than for 0° across both 60 - 80 mesh and 80 - 100 mesh size ranges of wheat flour. The vacuum cleaning treatment proved capable of overcoming the increase in adhesion from triboelectric forces, however trace flour residues were still detected on stainless steel surfaces post vacuuming, indicating that vacuuming alone may be insufficient.

A decision analysis of cancer patients and the consumption of ready-to-eat salad.

Listeria monocytogenes is a foodborne pathogen of concern for cancer patients, who face higher morbidity and mortality rates than the general population. The neutropenic diet (ND), which excludes fresh produce, is often utilized to mitigate this risk; however, an analysis weighing the theoretical listeriosis risk reduction of produce exclusion aspects of the ND and possible negative tradeoffs has never been conducted. Consequently, this work constructed decision analytic models using disability-adjusted life years (DALYs) to compare the impacts of the ND, such as increased neutropenic enterocolitis (NEC) likelihood, with three alternative dietary practices (safe food handling [SFH], surface blanching, and refrigeration only) across five age groups, for cancer patients who consume ready-to-eat salad. Less disruptive diets had fewer negative health impacts in all scenarios, with median alternative diet DALYs per person per chemotherapy cycle having lower values in terms of negative health outcomes (0.088-0.443) than the ND (0.619-3.102). DALYs were dominated by outcomes associated with NEC, which is more common in patients following the ND than in other diets. Switchover point analysis confirmed that, because of this discrepancy, there were no feasible values of other parameters that could justify the ND. Correspondingly, the sensitivity analysis indicated that NEC mortality rate and remaining life expectancy strongly affected DALYs, further illustrating the model's strong dependence on NEC outcomes. Given these findings, and the SFH's ease of implementation and high compliance rates, the SFH diet is recommended in place of the ND.

Food Safety Research and Extension Needs for the U.S. Low-Moisture Food Industry.

Historically, low-moisture foods were considered to have minimal microbial risks. However, they have been linked to many high-profile multistate outbreaks and recalls in recent years, drawing research and extension attention to low-moisture food safety. Limited studies have assessed the food safety research and extension needs for the low-moisture food industry. The objectives of this needs assessment were to explore the food safety culture and education needs, identify the food safety challenges and data gaps, and understand the barriers to adopting food-safety-enhancing technologies in the U.S. low-moisture food industry. This needs assessment was composed of two studies. In Study 1, food safety experts from the low-moisture food industry upper management participated in online interviews and a debriefing discussion session. In Study 2, an online anonymous survey was disseminated to a different group of experts with experience in the low-moisture food industry. The qualitative data were analyzed using deductive and inductive coding approaches, while the quantitative data were analyzed via descriptive analysis. Twenty-five experts participated in the studies (Study 1: n = 12; Study 2: n = 13). Common commodities that participants had worked with included nuts and seeds, spices, flour, and dried fruits and vegetables. A food safety culture conceptual framework was adapted, which included three main components: infrastructure conditions (foundation), individual's food safety knowledge, attitudes, and risk perceptions; and organizational conditions (supporting pillars). Major barriers to establishing a positive food safety culture were identified to be limited resources, difficulties in risk communication, and difficulties in behavioral change. For continual improvement in food safety performance, two major themes of food safety challenges and data gaps were identified: cleaning, sanitation, and hygienic design; and pathogen reduction. Participants perceived the main barriers discouraging the low-moisture food industry from adopting food-safety-enhancing technologies were: (1) budgetary priorities, (2) operation constraints, (3) technology validation, (4) consumer acceptance, and (5) maintaining desired product characteristics such as quality and sensory functionality. The findings of this needs assessment provide guidance for the food industry, academia, and government agencies about the direction of future research and the development of targeted extension programs that might help improve food safety in the low-moisture food industry.

Demonstration of Inappropriate Validation Method for a Cracker Baking Process Using Predictive Modeling.

Validation of baking processes for the inactivation of Salmonella is complicated by the combined effects of product heating and drying. The goal of this study was to quantitatively evaluate a previously disseminated approach to validating baking processes utilizing a predictive model developed using only isothermal and single-moisture inactivation data for the initially formulated dough. A simple cracker dough was formulated using flour inoculated with a five-strain cocktail of Salmonella. Side-by-side isothermal and baking experiments were performed to estimate Salmonella inactivation kinetics and to quantify survivors in a dynamic environment, respectively. Isothermal, single-moisture inactivation experiments were performed with cracker dough (water activity, aw = 0.956 ± 0.002; moisture content = 0.50 ± 0.01 dry basis) at three temperatures (56, 60, or 63°C) with ≥6 time intervals. Baking experiments were performed in a convection oven at 177°C with samples pulled every 30 s up to 360 s, with an endpoint product aw (25°C) of 0.45. The Salmonella isothermal, single-moisture inactivation kinetics in cracker dough resulted in D60°C and z-values of 4.6 min and 4.9°C, respectively; this model was then integrated over the dynamic product temperature profiles from the baking experiments. In the baking experiments, an average of 5-log reductions of Salmonella was achieved by 150 s of treatment; however, >100-log reductions were predicted by the dough-based models at that time point. This fail-dangerous overestimation of Salmonella lethality in crackers explicitly demonstrated that single-level moisture-based prediction models are inappropriate for describing inactivation in a process with both dynamic temperature and moisture, and that model-based validations must incorporate moisture/aw. Furthermore, end-users should exercise caution when utilizing unvalidated models to validate preventive control processes.

Effect of Air Temperature and Velocity on Listeria monocytogenes Inactivation During Drying of Apple Slices.

A wide range of drying parameters and methods are used by industry to produce dried apples. To ensure end-product safety and regulatory compliance, it is essential to evaluate the effectiveness of such industrial practices on microbial inactivation. Therefore, the objective of this study was to evaluate the effects of drying air temperature and velocity on Listeria monocytogenes inactivation during drying of apple slices. Apples (cv. Gala) were cored, sliced as rings (∼6 mm thick), and surface-inoculated with broth-grown culture of an 8-strain cocktail of L. monocytogenes to achieve an inoculation level of 8.6 ± 0.3 log CFU/g. Apple rings were dried in batches using dry air in a pilot-scale impingement oven at 60 or 80 °C air temperature and 0.7 or 2.1 m/s air velocity, and sampled every 30 min for bacterial enumeration, water activity (aw), and moisture content analysis. L. monocytogenes reduction increased (P < 0.05) with higher air velocity or higher drying air temperature. By the end of drying, in which the standard moisture content for dried apple slices of <24% wet basis was reached, L. monocytogenes was reduced by 1.8 ± 0.3 and 2.8 ± 0.7 log CFU/g at 0.7 and 2.1 m/s air velocity, respectively, after 180 min at 60 °C. When using 80 °C drying temperature, L. monocytogenes reduction was 5.2 ± 0.5 log CFU/g at both air velocities after 150 min. Therefore, process conditions should be considered in the validation of fruit drying processes, instead of solely relying on product endpoint properties, such as moisture content.

Listeriosis Risk Model for Cancer Patients Who Consume Ready-to-Eat Salad.

The foodborne pathogen Listeria monocytogenes generally infects immunocompromised individuals, such as cancer patients, more frequently and with higher morbidity and mortality than the general population. Because of the anticipated risk associated with L. monocytogenes and other pathogens in produce, immunocompromised individuals are often placed on neutropenic diets that exclude fresh produce, though these risks have not been quantified. Therefore, this study developed a data-driven risk model for listeriosis in cancer patients who consume ready-to-eat (RTE) salads, consisting of leafy greens, cucumbers, and tomatoes, as influenced by kitchen-scale treatments and storage practices. Monte Carlo simulations were used to model the risk of invasive listeriosis during one chemotherapy cycle. Refrigerating all salad components decreased the median risk by approximately one-half log. For refrigerated salads with no treatment, the predicted median risk was ≤ 4.3 × 10-08. When salad ingredients were surface blanched with greens rinsed, the predicted risk decreased to 5.4 × 10-10. Predicted risk was lowest (1.4 × 10-13) for a blanched "salad" consisting of solely cucumbers and tomatoes. Interestingly, rinsing, as recommended by FDA, only decreased the median risk by 1 log. A sensitivity analysis revealed that the highly variable dose-response parameter k strongly influenced risk, indicating that reducing uncertainty in this variable may improve model accuracy. Overall, this study demonstrates that kitchen-scale pathogen reduction approaches have high risk reduction efficacy and could be considered as an alternative to diets that exclude produce when making risk management decisions.

Effect of Lactose and Milk Protein on Thermal Resistance of Enterococcus faecium NRRL B-2354 and Salmonella in Dairy Powders.

ABSTRACT: Microbial challenge studies using nonpathogenic surrogates provide a practical means for validating thermally based pathogen controls for low-moisture foods. Because the relative thermal resistance, or kill ratio, of Enterococcus faecium NRRL B-2354 (a nonpathogenic surrogate) to Salmonella is greatly influenced by food composition, this study assessed relative thermal resistance of a five-strain Salmonella cocktail and E. faecium in skim milk powder (SMP), lactose-free skim milk powder (LSMP), 90% milk protein isolate (MPI), and lactose powder (LP). The impact of sugar composition (lactose versus glucose-galactose) on resuscitation of bacterial survivors, by using SMP and LSMP, was also determined. Dairy powders were inoculated with agar-grown cultures, mixed, preequilibrated at 0.25 water activity (aw), ground to achieve homogeneity, reequilibrated, and subjected to isothermal treatment. After enumeration on nonselective differential media, log-linear and Bigelow models were fit to the survivor data via one-step global regression. The aw changes and glass transition temperature were assessed at elevated temperatures by using uninoculated, equilibrated powder samples. Estimated D90°C-values were approximately two times higher for E. faecium (P < 0.05) than for Salmonella in SMP, LP, and MPI, but statistically similar (P > 0.05) in LSMP. Addition of sugars to recovery media did not influence survivor resuscitation from heat-treated SMP and LSMP, confirming that microbial inactivation was impacted primarily by the thermal treatment, not the recovery step. Thermally induced changes in aw were seen only for LP and MPI, with the glass transition temperature observed only for SMP and MPI. In conclusion, rather than always requiring greater lethality of E. faecium than Salmonella, these findings suggest that sufficient pathogen controls for low-moisture foods can also be validated by thoroughly documenting the appropriate kill ratios of E. faecium to Salmonella.

Interlaboratory Evaluation of Enterococcus faecium NRRL B-2354 as a Salmonella Surrogate for Validating Thermal Treatment of Multiple Low-Moisture Foods.

ABSTRACT: This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was ∼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision.

Survival of Escherichia coli O157:H7 during Moderate Temperature Dehydration of Plant-Based Foods.

The effect of moderate-temperature (≤60 °C) dehydration of plant-based foods on pathogen inactivation is unknown. Here, we model the reduction of E. coli O157:H7 as a function of product-matrix, aw, and temperature under isothermal conditions. Apple, kale, and tofu were each adjusted to aw 0.90, 0.95, or 0.99 and inoculated with an E. coli O157:H7 cocktail, followed by isothermal treatment at 49, 54.5, or 60.0 °C. The decimal reduction time, or D-value, is the time required at a given temperature to achieve a 1 log reduction in the target microorganism. Modified Bigelow-type models were developed to determine D-values which varied by product type and aw level, ranging from 3.0-6.7, 19.3-55.3, and 45.9-257.4 min. The relative impact of aw was product dependent and appeared to have a non-linear impact on D-values. The root mean squared errors of the isothermal-based models ranged from 0.75 to 1.54 log CFU/g. Second, we performed dynamic drying experiments. While the isothermal results suggested significant microbial inactivation might be achieved, the dehydrator studies showed that the combination of low product temperature and decreasing aw in the pilot-scale system provided minimal inactivation. Pilot-scale drying at 60 °C only achieved reductions of 3.1 ± 0.8 log in kale and 0.67 ± 0.66 log in apple after 8 h, and 0.69 ± 0.67 log in tofu after 24 h. This illustrates the potential limitations of dehydration at ≤60 °C as a microbial kill step.

Kitchen-Scale Treatments for Reduction of Listeria monocytogenes in Prepared Produce.

ABSTRACT: Listeriosis, a foodborne illness caused by Listeria monocytogenes, has relatively low incidence, but a substantial mortality rate, particularly in immunocompromised populations. Because of the known risk of L. monocytogenes and other pathogens in produce, immunocompromised individuals are often placed on neutropenic diets that exclude fresh produce. Therefore, this study aimed to evaluate several kitchen-scale treatments as potential interventions to reduce L. monocytogenes in prepared produce. Cucumbers, apples, and celery were dip inoculated with a three-strain cocktail of L. monocytogenes and dried for 24 h. Inoculated products were subjected to the following treatments as applicable: commercial sanitizer soak (90 s, with agitation), tap water rinse (15 s), tap water soak (90 s, with agitation), surface blanching (25 s), tap water rinse (15 s) followed by peeling, and surface blanching (25 s) followed by peeling. In addition, inoculum uptake in celery and the impact of two types of peelers (mechanical crank and manual) were assessed. Treated samples were plated on differential media and incubated for 48 h at 37°C. L. monocytogenes populations were then enumerated and compared with the untreated control (in log CFUs per gram). All treatments lacked efficacy for celery, with reductions significantly less (P < 0.05) than in other products, likely because of inoculum internalization. The sanitizer soak, tap water rinse, and tap water soak did not differ in efficacy (P > 0.05), which was low for cucumbers (<1.5 log CFU/g), apples (<1.3 log CFU/g), and celery (<0.7 log CFU/g). The two types of apple peelers did not differ in efficacy (P > 0.05). Surface blanching and surface blanching followed by peeling were the most effective treatments for both cucumbers and apples (P < 0.05), with average reductions of 4.2 to 5.1 and 3.5 to 5.9 log CFU/g, respectively.

Process Humidity Affects Salmonella Lethality at the Surface and Core of Impingement-Cooked Meat and Poultry Products.

ABSTRACT: Recent revisions to U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) compliance and safe harbor guidelines for ready-to-eat meat and poultry products addressed process humidity requirements. Given the lack of prior data for impingement-cooked products, the present study was conducted to evaluate the impact of process humidity on Salmonella lethality at the product core and surface and compliance of the results with FSIS lethality performance standards. Whole muscle beef strips, ground beef patties, whole muscle chicken breast fillets, and breaded ground chicken patties were inoculated with an eight-serovar cocktail of Salmonella. Beef and chicken samples were cooked in a pilot-scale moist-air impingement oven to a core temperature of 70.0 and 72.8°C, respectively, immediately quenched in liquid nitrogen, and dissected to obtain core and surface samples. Variables included oven temperature (218 and 232°C), air velocity (0.7 and 2.8 m/s), and oven humidity (0.7, 15, 30, or 70% moisture by volume [%, v/v]). Additional treatments were performed to examine the impact of supplemental critical control processes such as increased endpoint temperature, postoven carryover time, and pre- or postoven steam treatments. Salmonella reductions of >7 log units were reliably achieved in chicken patties regardless of the processing variables; however, none of the treatments reliably ensured >6.5-log reductions of Salmonella in ground beef. A majority of whole-muscle samples failed to meet the required performance lethality when processed at 0.7% (v/v) humidity; however, Salmonella inactivation was significantly improved (P < 0.05) at oven humidities of ≥30% (v/v). Dry oven conditions achieved greater Salmonella lethality at the core than at the surface for multiple products (P < 0.05). The efficacies of minimal and supplemental critical controls were dependent on product, process, and humidity (P < 0.05). Overall, process humidity and product variability should be considered in regulatory requirements and process validations.

Fate of Salmonella and Enterococcus faecium during Pilot-Scale Spray Drying of Soy Protein Isolate.

ABSTRACT: Outbreaks and recalls associated with microbial contamination of powdered foods have raised concern for the safety of the spray-drying process and its products. However, little research on the fate of bacteria during the spray-drying process has been done, leaving much unknown about the risks of contamination in spray dryers. Therefore, quantifying the contamination levels of Salmonella and Enterococcus faecium (as a surrogate) in various locations within a pilot-scale spray dryer can help illustrate the distribution of bacterial contamination, including in the final product. A 10% (w/w) dispersion of water and soy protein isolate was mixed with tryptic soy broth containing yeast extract inoculated with Salmonella enterica serovar Enteritidis phage type 30 (PT30) or E. faecium strain NRRL B-2354. This dispersion was spray dried using a pilot-scale tall-form cocurrent spray dryer at an inlet air temperature of 180, 200, or 220°C. After drying, samples of powder from eight locations within the system were collected or surface swabbed, plated, and enumerated. Spray drying achieved 2.40 to 4.15 and 2.33 to 2.83 log reductions in the concentrations of Salmonella and E. faecium, respectively, in the final powder product accumulated in the dryer's collectors. Salmonella and E. faecium were found in various concentrations in all locations within the spray dryer after a complete drying cycle. Differences in inlet air temperature between 180 and 220°C had no significant effect on the inactivation levels. As a surrogate, E. faecium was more resistant to spray drying than Salmonella. Overall, spray drying is capable of significant bacterial reduction in the final powder product, which can be combined with other hurdle technologies. However, adequate cleaning and sanitization procedures must be taken into consideration to prevent cross-contamination.

Modeling the Effects of Product Temperature, Product Moisture, and Process Humidity on Thermal Inactivation of Salmonella in Pistachios during Hot-Air Heating.

ABSTRACT: Prior efforts to model bacterial thermal inactivation in and on low-moisture foods generally have been based on isothermal and iso-moisture experiments and have rarely included dynamic product and process variables. Therefore, the objective of this study was to test appropriate secondary models to quantify the effect of product temperature, product moisture, and process humidity on thermal inactivation of Salmonella Enteritidis PT30 on pistachios subjected to dynamic dry- or moist-air heating. In-shell pistachios were inoculated with Salmonella Enteritidis PT30, equilibrated in controlled-humidity chambers (to target water activities [aw] of 0.45 or 0.65), and in some cases, subjected to a presoak treatment prior to heating in a laboratory-scale, moist-air convection oven at multiple combinations (in duplicate) of dry bulb (104.4 or 118.3°C) and dew point (∼23.8, 54.4, or 69.4°C) temperatures, with air speed of ∼1.3 m/s. Salmonella survivors, pistachio moisture content, and aw were quantified at six time points for each condition, targeting cumulative lethality of ∼3 to 5 log. The resulting data were used to estimate parameters for five candidate secondary models that included combinations of product temperature, product moisture, aw, and/or process dew point (coupled with a log-linear primary model). A model describing the D-value as a function of temperature and dew point fit the data well (root mean squared error [RMSE] = 0.86 log CFU/g); however, adding a term to account for dynamic product moisture improved the fit (RMSE = 0.83 log CFU/g). In addition, product moisture content yielded better model outcomes, as compared with aw, particularly in the case of the presoaked pistachios. When validated at the pilot scale, the model was conservative, always underpredicting the experimental log reductions. Both dynamic product moisture and process humidity were critical factors in modeling thermal inactivation of Salmonella in a low-moisture product heated in an air-convection system.

Influence of physical variables on the transfer of Salmonella Typhimurium LT2 between potato (Solanum tuberosum) and stainless steel via static and dynamic contact.

Bacterial cross-contamination between foods and contact surfaces can increase food safety risk; however, these processes are not well described in terms of fundamental variables. The objective was to determine the effect of sliding speed (3.75, 5.00, or 7.75 mm/s), contact time (5 or 40 s), normal pressure (~1217 to 8869 Pa), and number of sequential contacts on bacterial transfer to/from potato samples and stainless steel surfaces. Potato samples (~11 g, 3 × 3 × 1 cm) were either pulled across a stainless steel plate inoculated with Salmonella Typhimurium LT2 (~6.23 Log CFU/cm2) (dynamic contact) or placed on the inoculated plate for multiple sequential contacts on uninoculated squares (static contact). Salmonella on the potato and steel plate then were quantified by plating on modified trypticase soy agar. Bacterial transfer increased with increasing sliding speed (P = 0.0098) in dynamic tests and with contact time (P < 0.0001) in static tests. Salmonella on the inoculated potatoes decreased (P < 0.0001) from ~6.5 to ~5.5 Log CFU after 18 sequential static contacts with stainless steel. Reporting transfer results based on fundamental variables will improve the overall impact of bacterial transfer research on equipment design, cleaning/sanitation strategies, and overall food safety.

Reproducibility of Salmonella Thermal Resistance Measurements via Multilaboratory Isothermal Inactivation Experiments.

ABSTRACT: Isothermal inactivation experiments often are used to investigate the thermal resistance of pathogens, such as Salmonella, in foods; however, little is known about the reproducibility of such experimental methodologies. The objective of this study was to quantify the reproducibility of Salmonella isothermal resistance results via a six-laboratory comparison. Inoculation was performed at a single location and then distributed to each laboratory for isothermal analysis. Salmonella Agona 447967 was inoculated into oat flour, re-equilibrated to a water activity (aw) of 0.45, and then packaged and distributed to each laboratory. Before conducting the inactivation trials, each laboratory was required to verify the inoculated product's aw, enumerate Salmonella population levels, and verify that the isothermal treatment medium was at the target temperature (80°C). All laboratories were required to process at least three replications, collect at least six sample time points with three subsamples at each sampling point, enumerate survivors using an identical plating methodology and media, and verify that the temperature did not substantially change during isothermal treatment. The log-linear model was fit to the Salmonella survivor data, and the resultant D-values were statistically compared via Welch's t test (α = 0.05). Two significant differences in thermal inactivation kinetics were identified as potentially resulting from suspected methodology deviations. Two of the inoculated batches distributed for analysis yielded significantly lower D-values, which likely resulted from a deviation in the inoculation procedures. One laboratory yielded significantly lower D-values, which was likely the result of temperature deviations. Overall, excluding the D-values resulting from deviations, the inactivation results were reproducible, yielding D-values of 30.2 ± 3 min. These results indicate that isothermal inactivation results can be reproducible but that even minor methodology deviations can substantially affect measured Salmonella thermal resistance.

Thermal Resistance of Foodborne Pathogens and Enterococcus faecium NRRL B-2354 on Inoculated Pistachios.

ABSTRACT: Process control validations require knowledge of the resistance of the pathogen(s) of concern to the target treatment and, in some cases, the relative resistance of surrogate organisms. Selected strains of Escherichia coli O157:H7 (five strains), Listeria monocytogenes (five strains), and Salmonella enterica (five strains) as well as Salmonella Enteritidis phage type (PT) 30 and nonpathogenic Enterococcus faecium NRRL B-2354 were inoculated separately (as individual strains) onto inshell pistachios. The thermal tolerance of each strain was compared via treatment of inoculated pistachios to hot oil (121°C) or hot water (80°C) for 1 min. Survivor curves in hot oil or hot water (0.5 to 6 min, n = 6 to 15) were determined for one or two of the most resistant strains of each pathogen, as well as E. faecium NRRL B-2354 and Salmonella Enteritidis PT 30, and the Weibull model was fit to the data. A pilot-scale air-impingement oven was used to compare the thermal tolerance of E. faecium NRRL B-2354 and Salmonella Enteritidis PT 30 on pistachios with or without a brining pretreatment and at either dry (no steam) or 30% humidity (v/v) oven conditions. No significant difference in the time to a 4-log reduction in hot oil or hot water was predicted for any of the strains evaluated, on the basis of the 95% confidence interval. In the pilot-scale oven, E. faecium NRRL B-2354 was more thermally resistant than Salmonella in a broad set of differing treatments, treatment times, and temperatures. Salmonella is a suitable target pathogen of concern in pistachios for thermal processes because no other pathogen tested was more thermally resistant under the conditions evaluated. E. faecium NRRL B-2354 was at least as thermally resistant as Salmonella under all conditions evaluated, making it a good potential surrogate for Salmonella on pistachios.

Monetizing the Impact of Food Safety Recalls on the Low-Moisture Food Industry.

ABSTRACT: New Food Safety and Modernization Act rules require that food producers implement and validate processes that sufficiently reduce the risk of known hazards, such as those posed by microbial pathogens. Investments in food safety technology choices are ultimately business decisions, and current decision-making methods make it difficult to quantify financial value associated with food safety risk reduction. Predicted financial loss is a tangible way to quantify how a recall might affect the manufacturer. The hypothesis of this study was that class I recalls of low-moisture foods due to the presence of microbial pathogens have a significant negative economic impact on the affected manufacturers, which can be quantified in terms of loss in market capitalization. Financial impacts of the recalls were analyzed over a 10-year period by computing the cumulative abnormal return (CAR) in stock values over a recall event period for 22 low-moisture foods made by publicly held companies. Abnormal returns were aggregated over an event window (0 to 20 days) to compute the CAR, which was multiplied by prerecall market capitalization to compute monetary losses due to the recall event. The CARs for a 20-day postrecall period were -26.5 to 8.4%, with a mean of -5.1%. These CARs translated to a median loss in corporate value due to a recall of $243 million for the recall events analyzed in this study. If implementation of a food safety technology could reduce risk of a recall by fivefold, the mean annual economic benefit would be >$2 million in reduced risk for companies such as those included in the study. Such analyses can positively impact business decisions to invest in food safety technologies.

Effect of Food Structure, Water Activity, and Long-Term Storage on X-Ray Irradiation for Inactivating Salmonella Enteritidis PT30 in Low-Moisture Foods.

Recent outbreaks and recalls of low-moisture foods contaminated with Salmonella have been recognized as a major public health risk that demands the development of new Salmonella mitigation strategies and technologies. This study aimed to assess the efficacy of X-ray irradiation for inactivating Salmonella on or in almonds (kernels, meal, butter), dates (whole fruit, paste), and wheat (kernels, flour) at various water activities (aw) and storage periods. The raw materials were inoculated with Salmonella Enteritidis PT30, conditioned to 0.25, 0.45, and 0.65 aw in a humidity-controlled chamber, processed to various fabricated products, and reconditioned to the desired aw before treatment. In a storage study, inoculated almond kernels were stored in sealed tin cans for 7, 15, 27, and 103 weeks, irradiated with X ray (0.5 to 11 kGy, targeting up to a ∼2.5-log reduction) at the end of each storage period, and plated for Salmonella survivors to determine the efficacy of irradiation in terms of D10-value (dose required to reduce 90% of the population). Salmonella was least resistant (D10-value = 0.378 kGy) on the surface of almond kernels at 0.25 aw and most resistant (D10-value = 2.34 kGy) on the surface of dates at 0.45 aw. The Salmonella D10-value was 61% lower in date paste than on whole date fruit. Storage of almonds generally had no effect on the irradiation resistance of Salmonella over 103 weeks. Overall, these results indicate that product structure (whole, meals, powder, or paste), water activity (0.25 to 0.65 aw), and storage period (0 to 103 weeks) should be considered when determining the efficacy of X-ray irradiation for inactivating Salmonella in various low-water-activity foods.

Effect of Talc as a Dry-Inoculation Carrier on Thermal Resistance of Enterococcus faecium NRRL B-2354 in Almond Meal.

HIGHLIGHTS: E. faecium was more thermally resistant in dry- than in wet-inoculated almond meal. Presence of talc affected thermal resistance of E. faecium in almond meal. Use of dry inoculum carriers for thermal validation studies requires further work.

Relationships of Water Activity and Moisture Content to the Thermal Inactivation Kinetics of Salmonella in Low-Moisture Foods.

HIGHLIGHTS: Water affects thermal inactivation kinetics of Salmonella in low-moisture foods. Water activity and moisture content are both feasible predictors of heat resistance. Sorption state of food materials may affect Salmonella heat resistance.