Thermal inactivation of Salmonella during hard and soft cookies baking process.

This study validated a simulated commercial baking processes for hard and soft cookies to control Salmonella, and determined D- and z-values of 7-serotype Salmonella (Newport, Senftenberg, Tennessee, Typhimurium, and three isolates from dry pet food) cocktail in cookie doughs. Cookie doughs were prepared using flour mist-inoculated with the Salmonella cocktail. Hard and soft cookies were baked at 185 °C for 16 min and 165.6 °C for 22 min, respectively, followed by 30 min of ambient air cooling. D-values of the cocktail in cookie doughs were determined using thermal-death-time disks. Studies were designed as randomized complete blocks with three replications as blocks (α = 0.05). Salmonella populations decreased by > 5 log CFU/g in hard and soft cookies at 11.5 and 20.5 min of baking, respectively. Salmonella was not detected in hard cookies at the end of baking (as determined by enrichment), whereas in soft cookies, 0.6 log CFU/g Salmonella was present at the end of baking and cooling. Salmonella D-values in hard cookie dough at 60, 65 and 70 °C were 59.6, 28.1 and 11.9 min, respectively; while in soft cookie dough they were 62.3, 28.6 and 14.4 min, respectively. The Salmonella z-values in hard and soft cookie doughs were 14.5 and 15.8 °C, respectively.

Shiga Toxin-Producing Escherichia coli in Wheat Grains: Detection and Isolation by Polymerase Chain Reaction and Culture Methods.

Shiga toxin-producing Escherichia coli (STEC) are major foodborne pathogens and seven serogroups, O26, O45, O103, O111, O121, O145, and O157, often called top-7 STEC, account for the majority of the STEC-associated human illnesses in the United States. Two Shiga toxins, Shiga toxins 1 and 2, encoded by stx1 and stx2 genes, are major virulence factors that are involved in STEC infections. Foodborne STEC infections have been linked to a variety of foods of both animal and plant origin, including products derived from cereal grains. In recent years, a few STEC outbreaks have been linked to contaminated wheat flour. The microbiological quality of the wheat grains is a major contributor to the safety of wheat flour. The objective of the study was to utilize polymerase chain reaction (PCR)- and culture-based methods to detect and isolate STEC in wheat grains. Wheat grain samples (n = 625), collected from different regions of the United States, were enriched in modified buffered peptone water with pyruvate (mBPWp) or E. coli (EC) broth, and they were then subjected to PCR- and culture-based methods to detect and isolate STEC. Wheat grains enriched in EC broth yielded more samples positive for stx genes (1.6% vs. 0.32%) and STEC serogroups (5.8% vs. 2.4%) than mBPWp. The four serogroups of top-7 detected and isolated were O26, O45, O103, and O157 and none of the isolates was positive for the Shiga toxin genes. A total of five isolates that carried the stx2 gene were isolated and identified as serogroups O8 (0.6%) and O130 (0.2%). The EC broth was a better medium to enrich wheat grains than mBPWp for the detection and isolation of STEC. The overall prevalence of virulence genes and STEC serogroups in wheat grains was low. The stx2-positive serogroups isolated, O8 and O130, are not major STEC pathogens and have only been implicated in sporadic infections in animals and humans.

Evaluation of thermal inactivation parameters of Salmonella in whole wheat multigrain bread.

This study was conducted to validate a simulated commercial whole wheat multigrain bread baking process at 375 °F (190.6 °C) oven temperature for 35 min to inactivate Salmonella, and to determine the thermal inactivation parameters of a 7-serovar Salmonella cocktail in whole wheat multigrain bread dough. A ≥5-log CFU/g reduction in Salmonella population was achieved by 15 min, and no viable Salmonella was detected after enrichment plating by 16 min. The aw of the bread crumb (0.96) after baking and 60 min of cooling was similar to that of pre-baked bread dough, whereas the aw of bread crust decreased to 0.81 at the end of baking and cooling. The D-values of the Salmonella cocktail in bread dough were 59.6, 20.0 and 9.7 min at 50, 52 and 55 °C, respectively; and the z-value was 6.5 °C.

Prevalence of Enterohemorrhagic Escherichia coli O26, O45, O103, O111, O121, O145, and O157 on Hides and Preintervention Carcass Surfaces of Feedlot Cattle at Harvest.

Cattle hides are a main source of enterohemorrhagic Escherichia coli (EHEC) contamination of beef carcasses. The objectives of this study were to (1) determine the prevalence of "top 6" non-O157 plus O157:H7 EHEC (EHEC-7) on feedlot cattle hides and their matched preintervention carcasses; (2) assess the agreement among detection methods for these matrices; and (3) conduct a molecular risk assessment of EHEC-7 isolates. Samples from 576 feedlot cattle were obtained at a commercial harvest facility and tested for EHEC-7 by a culture-based method and the polymerase chain reaction/mass spectrometry-based NeoSEEK(™) STEC Detection and Identification test (NS). Prevalence data were analyzed with generalized linear mixed models. The cumulative prevalence of EHEC-7 in hide samples as detected by NS was 80.7%, with a distribution of 49.9%, O145; 37.1%, O45; 12.5%, O103; 11.0%, O157; 2.2%, O111; 2.0%, O121; and 0.2%, O26. In contrast, the cumulative prevalence of EHEC-7 in hide samples by culture was 1.2%, with a distribution of 0.6%, O157; 0.4%, O26; 0.2%, O145; and 0%, O45, O103, O111, and O121. The cumulative prevalence of EHEC-7 on matched preintervention carcasses as detected by NS was 6.0%, with a distribution of 2.8%, O157; 1.6%, O145; 1.2%, O103; 1.1%, O45; 0.2%, O26; and 0.0%, O111 and O121. Although the culture-based method detected fewer positive hide samples than NS, it detected EHEC in five hide samples that tested negative for the respective organism by NS. McNemar's chi-square tests indicated significant (p<0.05) disagreement between methods. All EHEC-7 isolates recovered from hides were seropathotype A or B, with compatible virulence gene content. This study indicates that "top 6" and O157:H7 EHEC are present on hides, and to a lesser extent, preintervention carcasses of feedlot cattle at harvest. However, continued improvement in non-O157 detection methods is needed for accurate estimation of prevalence, given the discordant results across protocols.

Survivability and thermal resistance of Salmonella and Escherichia coli O121 in wheat flour during extended storage of 360 days.

Foodborne pathogens like Salmonella and Escherichia coli O121 can endure the harsh low water activity (aw) environment of wheat flour for elongated periods of time and can proliferate when hydrated for baking or other purposes. This study determined the survivability and thermal tolerance (D- and z-values) of Salmonella and Escherichia coli O121 in wheat flour and muffin batter (prepared from inoculated flour on the days of analyses) during the storage period of 360 days. The Salmonella and E. coli O121 studies were conducted as two independent experiments. Both studies were designed as randomized complete block with three replications as blocks. All experimental data were analyzed using one-way ANOVA and Tukey's test in Minitab® software, and P ≤ 0.05 was considered significant. The wheat flour was spray inoculated individually with 7-isolate Salmonella or 3-isolate E. coli O121 cocktail and then dried back to the original aw levels. On each analysis day, inoculated wheat flour (~5 g) or muffin batter (~2.5 g) was placed inside the TDT disks, heat treated at set temperatures in hot water baths, and sampled at predetermined time intervals for determining the survival microbial population. The population of E. coli O121 and Salmonella cocktails in wheat flour at day 1 were 7.6 ± 0.18 and 7.8 ± 0.07 log CFU/g, respectively, which decreased to 2.0 ± 0.40 and 2.8 ± 0.59 log CFU/g on day 360, respectively. The D-values of Salmonella and E. coli O121 cocktails in inoculated flour and muffin batter prepared from inoculated flour (on the day of analysis) were determined on days 1, 30, 90, 180, 270, and 360 [given enough surviving bacterial population (~3 to 4 log CFU/g) was present in the flour]. The population of Salmonella and E. coli O121 in wheat flour decreased by 5.0 and 5.6 log CFU/g, respectively, during the storage period of 360 days. The D70°C, D75°C, and D80°C values of Salmonella in wheat flour remained similar during the storage period. Whereas, for E. coli O157:H7 in wheat flour, the D70°C value decreased from 20.3 ± 2.82 to 7.1 ± 2.82 min, and D75°C decreased from 10.2 ± 2.14 to 2.7 ± 0.27 min, during the storage period of 180 days. The z-values of Salmonella or E. coli O157:H7 remained similar during the storage period. The D- and z-values from this research can be employed for validation of thermal process to ensure safety of wheat flour.

Attachment of Shiga Toxin-Producing Escherichia coli (STEC) to Pre-Chill and Post-Chill Beef Brisket Tissue.

Shiga toxin-producing Escherichia coli (STEC) has caused numerous foodborne illness outbreaks where beef was implicated as the contaminated food source. Understanding how STEC attach to beef surfaces may inform effective intervention applications at the abattoir. This simulated meat processing conditions to measure STEC attachment to adipose and lean beef tissue. Beef brisket samples were warmed to a surface temperature of 30 °C (warm carcass), while the remaining samples were maintained at 4 °C (cold carcass), prior to surface inoculation with an STEC cocktail (O26, O45, O103, O111, O121, O145, and O157:H7). Cocktails were grown in either tryptic soy broth (TSB) or M9 minimal nutrient medium. Loosely and firmly attached cells were measured at 0, 3, 5, and 20 min and 1, 3, 8, 12, 24 and 48 h. TSB-grown STEC cells became more firmly attached throughout storage and a difference in loosely versus firmly attached populations on lean and adipose tissues was observed. M9-grown STEC demonstrated a 0.2 log10 CFU/cm2 difference in attachment to lean versus adipose tissue and variability in populations was recorded throughout sampling. Future research should investigate whether a decrease in intervention efficacy correlates to an increase in firmly attached STEC cells on chilled carcasses and/or subprimals, which has been reported.

Investigating Salmonella enterica, Escherichia coli, and Coliforms on Fresh Vegetables Sold in Informal Markets in Cambodia†.

ABSTRACT: Vegetables in Cambodia are commonly sold in informal markets lacking food safety standards and controls. Current data on microbial contamination of vegetables in Cambodian informal markets are limited. The purpose of this study was to investigate Salmonella enterica and indicator organisms (Escherichia coli and coliforms) on the surface of fresh vegetables sold in informal markets in Cambodia. Samples of loose-leaf lettuce, tomatoes, and cucumbers were collected from 104 vendors at four informal markets in Battambang and Siem Reap provinces during the rainy and dry seasons. Detection methods for S. enterica were adapted from the U.S. Food and Drug Administration's Bacteriological Analytical Manual. Coliform and E. coli populations were quantified by plating onto E. coli/coliform count plates. S. enterica was most prevalent on lettuce during the dry season (56.5%, 95% confidence interval [CI] [41.0, 70.8]) than during the rainy season (15.4%, 95% CI [7.5, 29.1]), whereas no significant seasonal differences were apparent for tomatoes and cucumbers. Regardless of season, levels of S. enterica were highest on lettuce (5.7 log CFU/g, 95% CI [5.5, 5.9]), relative to cucumbers (4.2 log CFU/g, 95% CI [3.8, 4.6]) and tomatoes (4.3 log CFU/g, 95% CI [4.1, 4.6]). For E. coli, prevalence was higher during the rainy season (34.0%, 95% CI [25.4, 43.8]) than during the dry season (9.1%, 95% CI [4.9, 16.5]), with the highest prevalence estimated on lettuce. Coliform levels on lettuce and tomatoes were greater during the rainy season (6.3 and 5.3 log CFU/g, 95% CI [5.7, 6.8] and [4.7, 5.8], respectively) than during the dry season (5.2 and 3.9 log CFU/g, 95% CI [4.7, 5.7] and [3.4, 4.4], respectively). These results indicate seasonal patterns for microbial prevalence in lettuce and an overall high level of bacterial contamination on raw vegetables sold in Cambodian informal markets.

Prevalence of Salmonella enterica Isolated from Food Contact and Nonfood Contact Surfaces in Cambodian Informal Markets.

ABSTRACT: The lack of hygiene and sanitation practices and insufficient infrastructure in Cambodian informal markets may increase the risk of food contamination, specifically raw vegetables, which in turn may increase the chances of contracting a foodborne disease. The aims of this study in informal markets in Cambodia were (i) to quantify the prevalence of Salmonella enterica based upon differences in season of the year (rainy versus dry), surface types (food contact surfaces versus nonfood contact surfaces), and location of vendors within the market (inside versus outside) and (ii) to characterize S. enterica serotype prevalence. A total of 310 samples were screened for S. enterica prevalence following the U.S. Department of Agriculture guidelines, and results were confirmed by PCR assay. Whole genome sequencing was used to determine the serotype for each isolate in silico using SeqSero 1.0 on draft genomes. A total of 78 samples were confirmed positive for S. enterica. During the dry season, S. enterica was more prevalent on food contact surfaces than on nonfood contact surfaces (estimated probability of detection [confidence interval]: 0.41 [0.25, 0.59] and 0.17 [0.08, 0.32], respectively; P = 0.002), but no differences were apparent in the rainy season. No differences in S. enterica prevalence were found based on location within the market (P = 0.61). Sixteen S. enterica serotypes were detected across multiple surfaces. The most common S. enterica serotypes were Rissen (18 isolates), Hvittingfoss (11), Corvallis (10), Krefeld (8), Weltevreden (6), and Altona (6). Accurate data on the prevalence of S. enterica in informal markets are crucial for the development of effective surveillance and implementation of suitable intervention strategies at the domestic level, thus preventing foodborne illness.

Draft Genome Sequences of Salmonella enterica subsp. diarizonae Serotype IIIb_61:I,v:1,5,(7) Strains Isolated from Wheat Grains.

Salmonella enterica subsp. diarizonae serotypes are primarily involved in reptile-associated salmonellosis in humans. Here, we report the draft genome sequences of three S. enterica subsp. diarizonae strains belonging to the serotype IIIb_61:1,v:1,5,(7), isolated from wheat grains collected at the time of harvest. Strains of serotype IIIb_61:1,v:1,5,(7) have been isolated from feces of reptiles, cattle, and sheep and from infections in humans.

Validation of post-harvest antimicrobial interventions to control Shiga toxin-producing Escherichia coli (STEC) on market hog carcass surfaces.

Although swine are less associated with STEC foodborne disease outbreaks, the potential for swine to serve as a source of STEC infections in human beings cannot be disregarded. This study compared eight USDA-approved antimicrobial intervention technologies to quantify their ability to reduce STEC contamination on market hog carcasses. Hogs were harvested to provide skin-on carcass sides, and eight sides (per three replications) were inoculated with a 7-strain STEC cocktail (ca. 5 log CFU/cm2 across all external and body cavity surfaces). Each side was randomly assigned to a final pre-chill wash treatment administered in a commercial Chad carcass cabinet using a low-volume spray [3% lactic acid (lLA; 130 °F), 400 ppm peracetic acid (lPAA), or acidified 400 ppm peracetic acid (laPAA)] or a high-volume wash [ambient water (hAW), 400 ppm PAA (hPAA), 400 or 600 ppm hypobromous acid (hDBDMH), or 71 °C water (hHW)] treatment according to a randomized complete block study design. Post-treatment (after a 10-min hanging drip) and post-chilling (18 h at 2 °C) STEC reductions were compared for external skin-on surfaces and internal body cavity lean surface tissue. Post-treatment color changes were determined for lean, adipose, and skin carcass surfaces before and after chilling. When applied to the external, skin-on surface, the hHW, hPAA, and hDBDMH600 deluge washes were significantly (P ≤ 0.05) more effective than the other intervention technologies, achieving STEC reductions of 3.8, 3.4, and 3.2 log CFU/cm2, respectively. In comparison, the hAW control reduced STEC by 1.7-log CFU/cm2 on the external, skin-on surface. The carcass interventions were less effective at reducing STEC populations attached to interior body cavity (diaphragm region), with post-chill populations reduced by 0.9-2.2 log cycles, while the hAW control wash achieved a 0.6-log reduction. None of the treatments negatively impacted instrumental carcass color. While all market hog carcass interventions reduced STEC populations, larger reductions were observed when applied to the external, skin-on surface, with the largest reductions achieved by the hHW, hPAA, and hDBDMH600 deluge washes. These data equip pork processors with the information necessary to support decision-making when selecting an intervention technology.

Genotypic and Phenotypic Characterization of Antimicrobial Resistance Profiles in Non-typhoidal Salmonella enterica Strains Isolated From Cambodian Informal Markets.

Non-typhoidal Salmonella enterica is a pathogen of global importance, particularly in low and middle-income countries (LMICs). The presence of antimicrobial resistant (AMR) strains in market environments poses a serious health threat to consumers. In this study we identified and characterized the genotypic and phenotypic AMR profiles of 81 environmental S. enterica strains isolated from samples from informal markets in Cambodia in 2018-2019. AMR genotypes were retrieved from the NCBI Pathogen Detection website (https://www.ncbi.nlm.nih.gov/pathogens/) and using ResFinder (https://cge.cbs.dtu.dk/services/) Salmonella pathogenicity islands (SPIs) were identified with SPIFinder (https://cge.cbs.dtu.dk/services/). Susceptibility testing was performed by broth microdilution according to the Clinical and Laboratory Standards Institute (CLSI) standard guidelines M100-S22 using the National Antimicrobial Resistance Monitoring System (NARMS) Sensititre Gram Negative plate. A total of 17 unique AMR genes were detected in 53% (43/81) of the isolates, including those encoding tetracycline, beta-lactam, sulfonamide, quinolone, aminoglycoside, phenicol, and trimethoprim resistance. A total of 10 SPIs (SPI-1, 3-5, 8, 9, 12-14, and centisome 63 [C63PI]) were detected in 59 isolates. C63PI, an iron transport system in SPI-1, was observed in 56% of the isolates (n = 46). SPI-1, SPI-4, and SPI-9 were present in 13, 2, and 5% of the isolates, respectively. The most common phenotypic resistances were observed to tetracycline (47%; n = 38), ampicillin (37%; n = 30), streptomycin (20%; n = 16), chloramphenicol (17%; n = 14), and trimethoprim-sulfamethoxazole (16%; n = 13). This study contributes to understanding the AMR genes present in S. enterica isolates from informal markets in Cambodia, as well as support domestic epidemiological investigations of multidrug resistance (MDR) profiles.

Identification, Shiga toxin subtypes and prevalence of minor serogroups of Shiga toxin-producing Escherichia coli in feedlot cattle feces.

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause illnesses in humans ranging from mild to hemorrhagic enteritis with complications of hemolytic uremic syndrome and even death. Cattle are a major reservoir of STEC, which reside in the hindgut and are shed in the feces, a major source of food and water contaminations. Seven serogroups, O26, O45, O103, O111, O121, O145 and O157, called 'top-7', are responsible for the majority of human STEC infections in North America. Additionally, 151 serogroups of E. coli are known to carry Shiga toxin genes (stx). Not much is known about fecal shedding and prevalence and virulence potential of STEC other than the top-7. Our primary objectives were to identify serogroups of STEC strains, other than the top-7, isolated from cattle feces and subtype stx genes to assess their virulence potential. Additional objective was to develop and validate a novel multiplex PCR assay to detect and determine prevalence of six serogroups, O2, O74, O109, O131, O168, and O171, in cattle feces. A total of 351 strains, positive for stx gene and negative for the top-7 serogroups, isolated from feedlot cattle feces were used in the study. Of the 351 strains, 291 belonged to 16 serogroups and 60 could not be serogrouped. Among the 351 strains, 63 (17.9%) carried stx1 gene and 300 (82.1%) carried stx2, including 12 strains positive for both. The majority of the stx1 and stx2 were of stx1a (47/63; 74.6%) and stx2a subtypes (234/300; 78%), respectively, which are often associated with human infections. A novel multiplex PCR assay developed and validated to detect six serogroups, O2, O74, O109, O131, O168, and O171, which accounted for 86.9% of the STEC strains identified, was utilized to determine their prevalence in fecal samples (n = 576) collected from a commercial feedlot. Four serogroups, O2, O109, O168, and O171 were identified as the dominant serogroups prevalent in cattle feces. In conclusion, cattle shed in the feces a number of STEC serogroups, other than the top-7, and the majority of the strains isolated possessed stx2, particularly of the subtype 2a, suggesting their potential risk to cause human infections.

Draft Genome Sequences of 81 Salmonella enterica Strains from Informal Markets in Cambodia.

Salmonella enterica is an important global pathogen due to its contribution to human morbidity and death. The presence of S. enterica in Southeast Asian informal markets is amplified by cross-contamination between market surfaces and food products. Here, we describe the draft genome sequences of 81 Salmonella enterica isolates from informal markets in Cambodia.

Thermal inactivation of Escherichia coli O157:H7 in blade-tenderized beef steaks cooked on a commercial open-flame gas grill.

Beef subprimals were inoculated on the lean side with ca. 4.0 log CFU/g of a cocktail of rifampin-resistant (Rif(r)) Escherichia coli O157:H7 strains and then passed once through a mechanical blade tenderizer with the lean side facing upward. Inoculated subprimals that were not tenderized served as controls. Two core samples were removed from each of three tenderized subprimals and cut into six consecutive segments starting from the inoculated side. A total of six cores were also obtained from control subprimals, but only segment 1 (topmost) was sampled. Levels of E. coli O157:H7 recovered from segment 1 were 3.81 log CFU/g for the control subprimals and 3.36 log CFU/g for tenderized subprimals. The percentage of cells recovered in segment 2 was ca. 25-fold lower than levels recovered from segment 1, but E. coli O157:H7 was recovered from all six segments of the cores obtained from tenderized subprimals. In phase II, lean-side-inoculated (ca. 4.0 log CFU/g), single-pass tenderized subprimals were cut into steaks of various thicknesses (1.91 cm [0.75 in.], 2.54 cm [1.0 in.], and 3.18 cm [1.25 in.]) that were subsequently cooked on a commercial open-flame gas grill to internal temperatures of 48.8 degrees C (120 degrees F), 54.4 degrees C (130 degrees F), and 60 degrees C (140 degrees F). In general, regardless of temperature or thickness, we observed about a 2.6- to 4.2-log CFU/g reduction in pathogen levels following cooking. These data validate that cooking on a commercial gas grill is effective at eliminating relatively low levels of the pathogen that may be distributed throughout a blade-tenderized steak.

Hyperspectral imaging of common foodborne pathogens for rapid identification and differentiation.

Hyperspectral imaging (HSI) provides both spatial and spectral information of a sample by combining imaging with spectroscopy. The objective of this study was to generate hyperspectral graphs of common foodborne pathogens and to develop and validate prediction models for the classification of these pathogens. Four strains of Cronobacter sakazakii, five strains of Salmonella spp., eight strains of Escherichia coli, and one strain each of Listeria monocytogenes and Staphylococcus aureus were used in the study. Principal component analysis and kNN (k-nearest neighbor) classifier model were used for the classification of hyperspectra of various bacterial cells, which were then validated using the cross-validation technique. Classification accuracy of various strains within genera including C. sakazakii, Salmonella spp., and E. coli, respectively, was 100%; except within C. sakazakii, strain BAA-894, and E. coli, strains O26, O45, and O121 had 66.67% accuracy. When all strains were studied together (irrespective of their genus) for the classification, only C. sakazakii P1, E. coli O104, O111, and O145, S. Montevideo, and L. monocytogenes had 100% classification accuracy, whereas E. coli O45 and S. Tennessee were not classified (classification accuracy of 0%). Lauric arginate treatment of C. sakazakii BAA-894, E. coli O157, S. Senftenberg, L. monocytogenes, and S. aureus significantly affected their hyperspectral signatures, and treated cells could be differentiated from the healthy, nontreated cells.

Validation of a nut muffin baking process and thermal resistance characterization of a 7-serovar Salmonella inoculum in batter when introduced via flour or walnuts.

This study was conducted to validate a commercial nut muffin baking process and to compare the survival of a 7-serovar Salmonella cocktail when contaminated via inoculated flour or walnuts. Enriched wheat flour or walnut pieces were mist inoculated with the Salmonella cocktail and dried back to the pre-inoculation weight, resulting in a Salmonella population level of 6.9 and 8.4 log CFU/g, respectively. Nut muffin batters were prepared separately using inoculated flour or walnuts, followed by baking at 375 °F (190.6 °C) oven temperature for 21 min and post-bake ambient air-cooling (B + C). During baking, >5-log CFU/g reductions in the Salmonella population in nut muffins was achieved in 17 min, and Salmonella was not detected by direct plating (<0.2 log CFU/g detection limit) but was recovered by enrichment at the end of 21 min of baking and B + C. In a separate baking study using an extended baking time (24 min) at 375 °F, Salmonella was detected after 24 and 22 min using enrichment plating of nut muffins prepared from inoculated flour and walnuts, respectively. The D-values of the Salmonella cocktail in nut muffin batters prepared from inoculated flour were 24.0, 4.0 and 0.6 min at 60, 65 and 70 °C; whereas, corresponding D-values in batters prepared from inoculated walnuts were 22.0, 3.6 and 1.7 min. The z-values of the Salmonella cocktail in nut muffin batters were 6.1 and 9.0 °C for inoculated flour and walnuts, respectively. This simulated commercial nut muffin baking study utilizing an oven temperature of 190.6 °C for at least 17 min validates that the process will eliminate Salmonella populations by ≥5 log CFU/g if pre-baking contamination occurs via flour or walnut ingredients.

Validation of a Sequential Hide-On Bob Veal Carcass Antimicrobial Intervention Composed of a Hot Water Wash and Lactic Acid Spray in Combination with Scalding To Control Shiga Toxin-Producing Escherichia coli Surrogates†.

Scalding of hide-on bob veal carcasses with or without standard scalding chemical agents typically used for hogs, followed by an 82.2°C hot water wash and lactic acid spray (applied at ambient temperature) before chilling, was evaluated to determine its effectiveness in reducing Shiga toxin-producing Escherichia coli surrogate populations. A five-strain cocktail of rifampin-resistant, nonpathogenic E. coli surrogates was used to inoculate hides of veal carcasses immediately after exsanguination (target inoculation level of 7.0 log CFU/100 cm2). For carcasses receiving no scalding treatments, spraying with 82.2°C water as a final wash resulted in a 4.5-log CFU/100 cm2 surrogate reduction, and an additional 1.2-log CFU/100 cm2 reduction was achieved by spraying with 4.5% lactic acid before chilling. Scalding hide-on carcasses in 60°C water (no chemicals added) for 4 min in a traditional hog scalding tank resulted in a 2.1-log CFU/100 cm2 reduction in surrogate levels, and a subsequent preevisceration 82.2°C water wash provided an additional 2.9-log CFU/100 cm2 reduction. Spraying a 4.5% solution of lactic acid onto scalded, hide-on carcasses (after the 82.2°C water wash) resulted in a minimal additional reduction of 0.4 log CFU/100 cm2. Incorporation of scalding chemicals into the scald water resulted in a 4.1-log CFU/100 cm2 reduction (1.9 log CFU/100 cm2 greater than scalding without chemicals) in the surrogate population, and the first 82.2°C wash provided an additional 2.5-log CFU/100 cm2 reduction. Application of antimicrobial interventions did not affect the carcass temperature decline during chilling, the pH decline, or the color characteristics of the ribeye or the flank of the bob veal carcasses.

Evaluation of post-fermentation heating times and temperatures for controlling Shiga toxin-producing Escherichia coli cells in a non-dried, pepperoni-type sausage.

Coarse ground meat was mixed with non-meat ingredients and starter culture (Pediococcus acidilactici) and then inoculated with an 8-strain cocktail of Shiga toxin-producing Escherichia coli (ca. 7.0 log CFU/g). Batter was fine ground, stuffed into fibrous casings, and fermented at 35.6°C and ca. 85% RH to a final target pH of ca. pH 4.6 or ca. pH 5.0. After fermentation, the pepperoni-like sausage were heated to target internal temperatures of 37.8°, 43.3°, 48.9°, and 54.4°C and held for 0.5 to 12.5 h. Regardless of the heating temperature, the endpoint pH in products fermented to a target pH of pH 4.6 and pH 5.0 was pH 4.56±0.13 (range of pH 4.20 to pH 4.86) and pH 4.96±0.12 (range of pH 4.70 to pH 5.21), respectively. Fermentation alone delivered ca. a 0.3- to 1.2-log CFU/g reduction in pathogen numbers. Fermentation to ca. pH 4.6 or ca. pH 5.0 followed by post-fermentation heating to 37.8° to 54.4°C and holding for 0.5 to 12.5 h generated total reductions of ca. 2.0 to 6.7 log CFU/g.

Validation of the baking process as a kill-step for controlling Salmonella in muffins.

This research investigates the potential risk of Salmonella in muffins when contamination is introduced via flour, the main ingredient. Flour was inoculated with a 3-strain cocktail of Salmonella serovars (Newport, Typhimurium, and Senftenberg) and re-dried to achieve a target concentration of ~8logCFU/g. The inoculated flour was then used to prepare muffin batter following a standard commercial recipe. The survival of Salmonella during and after baking at 190.6°C for 21min was analyzed by plating samples on selective and injury-recovery media at regular intervals. The thermal inactivation parameters (D and z values) of the 3-strain Salmonella cocktail were determined. A ≥5logCFU/g reduction in Salmonella population was demonstrated by 17min of baking, and a 6.1logCFU/g reduction in Salmonella population by 21min of baking. The D-values of Salmonella serovar cocktail in muffin batter were 62.2±3.0, 40.1±0.9 and 16.5±1.7min at 55, 58 and 61°C, respectively; and the z-value was 10.4±0.6°C. The water activity (aw) of the muffin crumb (0.928) after baking and 30min of cooling was similar to that of pre-baked muffin batter, whereas the aw of the muffin crust decreased to (0.700). This study validates a typical commercial muffin baking process utilizing an oven temperature of 190.6°C for at least 17min as an effective kill-step in reducing a Salmonella serovar population by ≥5logCFU/g.