Authors:IGO MJ; HEDEEN N, SCHAFFNER DW. Pages: 6 - 13 Abstract: ABSTRACTOutbreaks from improperly cooled foods continue to occur despite clearly described Food Code cooling guidelines. It is difficult for regulators to enforce these guidelines because they are typically in an establishment for less than the 6 h needed to document proper cooling. Prior research proposed using a novel method to estimate cooling rates based on two time-temperature points, but this method has not yet been validated. Time-temperature profiles of 29 different foods were collected in 25 different restaurants during cooling. Cooling curves were divided into two categories: typical (21 foods) and atypical (eight foods) prior to further analysis. Analysis of the typical cooling curves used simple linear regression to calculate cooling rates. The atypical cooling profiles were studied using Monte Carlo simulations of the cooling rate. Almost all linearized typical cooling curves had high (>0.90) R2 values. Six foods with typical cooling profiles that did not pass Food Code cooling times were correctly identified by the two-point model as having slow cooling rates. Three foods that did not pass Food Code cooling times were identified by the two-point model as having marginal cooling rates. Ten of 12 foods identified by the two-point model as having acceptable cooling rates met Food Code cooling times. Most (six of eight) foods that were considered to have atypical cooling curves failed to meet the Food Code cooling times. The two-point model was also able to determine whether these foods would fail based on Food Code guidelines depending upon the simulation criteria used. Our data show that food depth has a strong influence on cooling rate. Containers with a food depth ≥7.6 cm (3 in.) were more likely to have cooling rates slower than the U.S. Food and Drug Administration Model Food Code cooling rate. This analysis shows that the two-point method can be a useful screening tool to identify potential cooling rate problems during a routine restaurant inspection visit.HIGHLIGHTSContainers with food depth ≥7.6 cm were likely to have slow cooling rates.Most (21 of 29) foods had linearized cooling rates with high (>0.90) R2 values.Most (15 of 17) slow cooling foods were identified by the two-point method.All (12 of 12) fast cooling foods were identified by the two-point method.The two-point method can be used to identify potential cooling rate problems. PubDate: Fri, 07 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-257 Issue No:Vol. 84, No. 1 (2020)
Authors:RIVAS L; DUPONT P, GILPIN B, et al. Pages: 14 - 22 Abstract: ABSTRACTA pilot survey was performed to determine the prevalence of Campylobacter jejuni and Campylobacter coli on three age classes (lamb, hogget, and mutton) of ovine carcass trim postdressing and prechill. Sampling of hogget carcasses was undertaken 6 months before sampling of lamb and mutton carcasses. A total of 120 trim samples were collected from 11 processing plants across New Zealand. All samples were enriched and screened using PCR for the presence of C. jejuni and C. coli, and isolation was attempted for all screen-positive samples. Enumeration of Campylobacter from lamb trim samples showed that Campylobacter bacteria were present in very low numbers (<10 CFU/g). The overall prevalence of Campylobacter for ovine trim based on PCR detection was 33% (39 of 120 samples), with prevalences for hogget, lamb, and mutton carcass trim of 56% (28 of 50), 11% (4 of 35), and 20% (7 of 35), respectively. Whole genome sequencing was performed on a selection of C. jejuni and C. coli isolates, and the data were used to subtype using multilocus sequence typing (MLST) and whole genome MLST. Twenty-five MLST sequence types (STs) were identified among 44 isolates, including ST42, ST50, ST3222, and ST3072, which have been previously reported to be associated with ruminant sources. Four novel STs were also identified. Whole genome MLST analysis further discriminated isolates within a single ST type and demonstrated a genetic diversity among the ovine isolates collected. Genes associated with the oxacillinase class of β-lactamase enzymes were identified in 41 of 44 Campylobacter isolates. This study provides preliminary data that can be incorporated into existing source attribution models to assist in determining the potential contribution of ovine sources to the burden of campylobacteriosis in New Zealand.HIGHLIGHTSCampylobacter prevalence for ovine carcass trim based on PCR detection was 33%.Enumeration of Campylobacter bacteria was <10 CFU/g on lamb trim.Twenty-five multilocus sequence types (STs) were identified among 44 isolates.Whole genome sequence analysis discriminated isolates within a single ST. PubDate: Fri, 07 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-220 Issue No:Vol. 84, No. 1 (2020)
Authors:LI H; ZHU Q, CHANG R, et al. Pages: 23 - 30 Abstract: ABSTRACTIn order to reduce the health risks associated with red meat as listed by the World Health Organization, the work presented in this article aimed to elucidate the interaction between 5′-CMP–supplemented feed and N-glycolylneuraminic acid (Neu5Gc) in experimental animals in vivo. 5′-CMP was added to the diet of 90-, 180-, and 270-day-old Xiang pigs, and after 30 days, the Neu5Gc contents, physicochemical parameters, and free amino acid contents of muscle and internal viscera were measured by high-performance liquid chromatography coupled with fluorescence detection. The mechanism by which 5′-CMP affects Neu5Gc contents was investigated using molecular docking. Results show that 5′-CMP significantly decreased the Neu5Gc content in 180-day-old Xiang pigs (P < 0.05) but had no effect on the Neu5Gc contents in 90- and 270-day-old Xiang pigs. Umami amino acids were significantly increased in 180-day-old Xiang pigs. In the 90- and 270-day-old pigs, histidine increased by 10.38 and 17.87%, respectively. The other free amino acids were either reduced or not affected. Moreover, the 5′-CMP–supplemented diet did not affect the physicochemical parameters of the longissimus muscle in the Xiang pigs. 5′-CMP could occupy almost all the sialyltransferase active-site residues but not His302 and showed inhibition of the sialyltransferase activity. The results provided an experimental basis for the subsequent reduction of Neu5Gc in red meat before slaughter.HIGHLIGHTSIntervention with 5′-CMP to modify Neu5Gc contents in Xiang pigs of different ages is discussed.This study aims to discover an effective method for reducing the risk of chronic disease.The inhibition mechanism of 5′-CMP on sialyltransferase and CMAH was explored by molecular docking.The addition of 5′-CMP to feed did not affect the processed-meat characteristics of Xiang pigs.5′-CMP provides a novel tactic for reducing Neu5Gc content in red meat before slaughter. PubDate: Fri, 07 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-191 Issue No:Vol. 84, No. 1 (2020)
Authors:MOHAMMAD Z; BECK S, KING M, et al. Pages: 31 - 38 Abstract: ABSTRACTThe aim of this study was to compare the effectiveness of a quantitative real-time PCR (qPCR) molecular method and the Crystal Diagnostic Xpress (CDx) immunoassay for detecting Salmonella and Shiga toxin–producing Escherichia coli (STEC) in air samples collected from abattoirs in Texas. The 70 air samples were collected from two small and two large meat processing plants in the spring and summer with a wetted wall cyclone air sampler. The samples were divided equally into two parts: one part was used for the qPCR assay, and the other part was enriched for 18 and 36 h and evaluated with the CDx immunoassay. All samples for which positive results were obtained were confirmed by plating and by biochemical and serological tests as recommended by AOAC International to verify results of rapid methods. With the qPCR and CDx assays and 36 h of enrichment, 37.5 and 57.1% of the samples, respectively, were positive for Salmonella (P < 0.05) and 65.0 and 60.7%, respectively, were positive for STEC (P > 0.05). Air samples required longer enrichment for the CDx immunoassay than recommended by the manufacturer for food samples. Recovery of Salmonella and STEC increased 16 and 47%, respectively, when enrichment was extended from 18 to 36 h. The prevalence of Salmonella and STEC obtained with both methods was affected by the size of the processing plant and the processing stage. Detection rates for samples from larger plants were higher for both pathogens. Significantly higher prevalence was obtained for samples from the stunning and dehiding areas than for those from the fabrication rooms and chillers. Salmonella detection was higher with the CDx assay than with the qPCR assay, but no differences were found for the detection of STEC by the qPCR and CDx assays. These results highlight the importance of method adjustments when testing matrices other than foods. More research is needed to understand the dynamics of pathogen dispersal in aerosols and how this affects the effectiveness of current rapid detection methods.HIGHLIGHTSAir in beef slaughtering establishments can harbor pathogenic bacteria.Air samples required longer enrichment than was recommended for food samples.Salmonella and STEC were detected in air samples at beef slaughter establishments.The qPCR and CDx assays were equally effective for detecting Salmonella and STEC in air.Detection rates for pathogens in the air are enhanced by using two methods simultaneously. PubDate: Thu, 20 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-19-616 Issue No:Vol. 84, No. 1 (2020)
Authors:KUMAR N; MOHAN K, GEORGES K, et al. Pages: 39 - 46 Abstract: ABSTRACTThe study used PCR to determine the molecular basis of the antibiotic resistance and virulence profiles of isolates of Salmonella by targeting genes encoding for carriage and persistence in the poultry. Of a total 1,503 cecal samples collected from poultry, 91 (6.1%) were positive for Salmonella. Ten different serotypes were detected from Salmonella isolates. The study was also conducted to determine the occurrence of 13 virulence and 12 resistance genes in isolates of Salmonella. All 46 isolates of Salmonella tested were positive for one or more of the 12 virulence genes detected, ranging from 0.0% (viaB) to 100.0% (invA, mgtB, pipA, and spi4D) (P < 0.05). Occurrence of virulence genes varied significantly (P < 0.05) by serotype but not by animal species. Only 4 (33.3%) of 12 resistance genes assayed were detected: strA, ampC, cmy2, and qnrB. Overall, the occurrence of detected resistance genes was 71.7% (33 of 46), and 87.1 and 40.0% of the isolates from chickens and ducks, respectively, were positive (P = 0.0009). The occurrence of resistance genes ranged from 2.2% (cmy2) to 50.0% (qnrB) in isolates positive for resistance gene. The findings provide evidence that poultry from “pluck shops” are colonized by Salmonella pathogens that harbor virulence and antimicrobial resistance genes; this may have clinical and therapeutic consequences, if the genes detected are expressed. Although there is a need for prudent use of antimicrobial agents in poultry production systems, there should be constant monitoring for the prevalence of resistance in Salmonella isolates using phenotypic methods. The importance of monitoring the occurrence of resistance genes in the pathogens in Trinidad cannot be ignored.HIGHLIGHTSSalmonella with virulence and antimicrobial resistance genes colonize poultry from pluck shops.Most of the isolates of Salmonella tested were positive for 13 virulence genes.Salmonella with virulence genes may play an important role in causing severe infection.Of tested resistance genes, only strA, ampC, cmy2, and qnrB were found, at a prevalence of 71.7%.Salmonella Molade isolates had identical resistance patterns, with the exception of qnrB. PubDate: Thu, 20 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-203 Issue No:Vol. 84, No. 1 (2020)
Authors:CASULLI KE; DOLAN KD, MARKS BP. Pages: 47 - 57 Abstract: ABSTRACTPrior 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.HIGHLIGHTSSalmonella inactivation under dynamic conditions was modeled in pistachios.Product temperature, moisture, and process humidity affected Salmonella lethality.Including all three variables in inactivation models improved model accuracy.The best-fitting model was conservative when validated at the pilot scale.More validation data are needed prior to using this model at the commercial scale. PubDate: Thu, 20 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-221 Issue No:Vol. 84, No. 1 (2020)
Authors:WAMBUI J; GHIELMETTI G, MORACH M, et al. Pages: 58 - 62 Abstract: ABSTRACTClostridium estertheticum and C. estertheticum–like spp. are obligate anaerobic psychrophiles causing “blown pack” spoilage of chilled vacuum-packed meat. The present study aimed at detecting and isolating these spoilage bacteria in fecal samples of cattle of different ages at the slaughterhouse level. One hundred two swab fecal samples were obtained and enriched anaerobically in prereduced peptone-yeast-glucose-starch (PYGS) medium for 3 weeks at 4°C and then screened for C. estertheticum and C. estertheticum–like spp. by using a 16S rRNA gene–based real-time PCR (RT-PCR) assay. The RT-PCR–positive samples were further enriched for 3 weeks in prereduced PYGS medium and then subjected to an ethanol (50%, v/v) and lysozyme (4 mg/mL) treatment. Isolation was carried out anaerobically on Columbia agar with 5% defibrinated sheep blood at 4°C for 3 weeks. Isolated strains were identified morphologically and by the 16S rRNA gene. Forty (39%) of 102 samples were RT-PCR positive. The frequency of positive samples was the following: 9 (45%) of 20 in calves (aged ≤160 days), 23 (43%) of 54 in young cattle (aged 161 to 1,000 days), and 8 (29%) of 28 in cows or bulls (aged >1,000 days). Six strains were isolated from 6 of 40 RT-PCR–positive samples. Of these, five were from the calves (n = 1) and young cattle (n = 4). The six isolates were identified as C. estertheticum (n = 1), Clostridium frigoriphilum (n = 1), and C. estertheticum–like spp. (n = 4). The present findings confirm that feces of cattle are an important source of psychrophilic Clostridium spp. The fecal carriage among livestock animals at slaughter is strongly correlated with the risk of carcass contamination. Therefore, the maintenance of slaughter hygiene is of central importance.HIGHLIGHTSPsychrophilic Clostridium spp. were detected by PCR in 40 of 102 cattle fecal samples.Isolates included C. estertheticum, C. frigoriphilum, and C. estertheticum–like spp.Frequency of detection (43%) and isolation (6%) was highest in cattle aged ≤1,000 days. PubDate: Thu, 20 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-259 Issue No:Vol. 84, No. 1 (2020)
Authors:ZHANG Q; SONG X, SUN W, et al. Pages: 63 - 72 Abstract: ABSTRACTA total of 115 isolates of lactic acid bacteria were screened from traditional fermented foods in Guizhou Province, People's Republic of China. The cholesterol removal rates of 86 isolates ranged from 7.29 to 25.66%, and 18 isolates showed a cholesterol removal rate of more than 15%. According to the results of physiological and biological tests, 13 isolates were selected to determine the fermentation performance; 9 isolates—MT-4, MT-2, PJ-15, SR2-2, SQ-4, SQ-7, ST2-2, ST2-6, and NR1-7—had high tolerance of bile salt and acid and had a survival rate of more than 96% under pH 3.0 and 0.3% bile salt. ST2-2, SR2-2, NR1-7, SQ-4, and MT-4 had high survival rate in different concentrations of NaCl and NaNO2 under different temperatures. According to BLAST comparison results of the 16S rRNA sequence in the GenBank database and the genetic distance of the 16S rRNA sequence with an ortho-connected algorithm, SR2-2, NR1-7, and ST2-2 were identified as Lactobacillus plantarum, MT-4 was identified as Lactobacillus pentosus, and SQ-4 was identified as Lactobacillus paraplantarum. Moreover, strains SQ-4 and MT-4 were added to fermented beef. Results showed that the fermented beef had delicious taste and was popular to consumers because of its proper pH, pleasant colors, high viable cell count, and suitable content of bound and immobilized water. These results provide a basis for the development of new starter formulation for the production of high-quality fermented meat products.HIGHLIGHTSA total of 115 LAB isolates were obtained from traditional fermented products in Guizhou, China.Five strains had high tolerance to acid and bile salt and a high survival rate in NaCl and NaNO2.Lactobacillus pentosus MT-4 and L. paraplantarum SQ-4 could be potential meat starters. PubDate: Thu, 20 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-225 Issue No:Vol. 84, No. 1 (2020)
Authors:SCHWAN CL; DESIREE K, BELLO NM, et al. Pages: 73 - 79 Abstract: ABSTRACTThe 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.HIGHLIGHTSS. enterica prevalence was higher on food contact surfaces in the dry season.S. enterica prevalence was similar regardless of market location.Sixteen S. enterica serotypes were detected.S. enterica subsp. enterica serotype Rissen was the most prevalent serotype. PubDate: Thu, 27 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-112 Issue No:Vol. 84, No. 1 (2020)
Authors:HORTON BC; GEHRING KB, SAWYER JE, et al. Pages: 80 - 86 Abstract: ABSTRACTManaging the presence of Salmonella in ground beef has been an ongoing challenge for the beef industry. Salmonella prevalence can vary regionally, seasonally, and within the animal, making the development of interventions difficult. The objective of this study was to assess the efficacy of an autogenous Salmonella vaccine in mitigating Salmonella in lymph nodes (LNs) of feedlot cattle. An autogenous vaccine was developed using the most common Salmonella enterica serovars (Salmonella Kentucky, Salmonella Anatum, Salmonella Muenchen, Salmonella Montevideo, and Salmonella Mbandaka) identified from cattle managed at a South Texas feedlot with historically high Salmonella prevalence. Fifty-five heifers were selected for even distribution across five groups: (i) BASE, which received no autogenous vaccinations and were harvested after the stocker stage, (ii) CNTRL, which received no autogenous vaccinations, (iii) FARM, which received autogenous vaccinations at the ranch only, (iv) SPLIT, which received autogenous vaccinations at both the ranch and feedlot, and (v) YARD, which received vaccinations at the feedlot only. One heifer each from the BASE and CNTRL groups did not complete the study. All treatment groups except BASE were harvested after reaching market weight. Left and right superficial cervical and subiliac LNs from each carcass were collected and analyzed for Salmonella presence, and positive samples were serotyped. No salmonellae were recovered from LNs derived from BASE, FARM, SPLIT, or YARD groups. Cattle in the BASE group were expected to have a low occurrence of Salmonella based on previous research. However, the percentage of Salmonella-positive animals in the CNTRL group was 20.0% (2 of 10), which is lower than expected based on historical data from the same feeding location. There could be several causes of decreased Salmonella presence in the LNs of control cattle, creating an opportunity for future investigation into the development of preharvest interventions to combat Salmonella in feedlots.HIGHLIGHTSAn autogenous vaccine using five Salmonella serovars was developed.No salmonellae were recovered from the lymph nodes (LNs) of vaccinated cattle.Twenty percent of untreated experimental cattle had Salmonella-positive LNs.Serovars recovered from control cattle differed from those used in the vaccine.Untreated cattle housed adjacent to treated cattle had Salmonella-negative LNs. PubDate: Thu, 27 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-171 Issue No:Vol. 84, No. 1 (2020)
Authors:SAMELI N; SKANDAMIS PN, SAMELIS J. Pages: 87 - 98 Abstract: ABSTRACTThe ability of the enterocin A-B-P–producing Enterococcus faecium KE82 adjunct strain to inactivate Listeria monocytogenes during protected designation of origin Galotyri processing was evaluated. Three trials were conducted with artisan cheeses made from traditionally “boiled” (85°C) ewe's milk. The milk was cooled at 42°C and divided in two treatments. A1 milk was inoculated with Streptococcus thermophilus ST1 and Lactococcus lactis subsp. cremoris M78, and A2 was inoculated with the basic starter ST1+M78 plus KE82 (step 1). All milks were fermented at 20 to 22°C for 24 h (step 2), and the curds were drained at 12°C for 72 h (step 3) and then salted with 1.5 to 1.8% salt to obtain the fresh Galotyri cheeses (step 4). These fresh cheeses were then ripened at 4°C for 30 days (step 5). Because artificial listerial contamination in the dairy plant was prohibited, samples of A1 and A2 cheese milk (200 mL) or curd (200 g) were collected after steps 1 through 5, inoculated with L. monocytogenes 10 (3 to 4 log CFU/mL or g), incubated at 37, 22, 12, and 4°C for predefined periods, and analyzed for microbial levels and pH. L. monocytogenes levels declined in all cheese curd portions contaminated after steps 2 through 5 (pH 4.36 to 4.84) when stored at 4 or 12°C for 15 days. The final net reductions in Listeria populations were 2.00-, 1.07-, 0.54-, and 0.61-log greater in the A2 than in the A1 curd portions after steps 2, 3, 4, and 5, respectively. In step 1, conducted to simulate the whole cheese milk fermentation process, L. monocytogenes levels declined by 1.47 log CFU/mL more in the A2 than in the A1 milk portions after 72 h at 22°C; however, slight growth (0.6 log CFU/mL) occurred during the first 6 h at 37°C. E. faecium KE82 was compatible with the starter culture and enhanced inactivation of L. monocytogenes during all steps of Galotyri cheese processing. The antilisterial effects of the combined acid and enterocin were the weakest in the fermenting milks, the strongest in the unsalted fermented curds, and declined again in the salted fresh cheeses.HIGHLIGHTSL. monocytogenes survived but did not grow during all cheese postfermentation steps.E. faecium KE82 enhanced listerial inactivation by 0.5 to 2 log CFU/g.L. monocytogenes viability loss due to KE82 depended on the cheese processing step.Maximum antilisterial effects of the acid plus enterocin were found in fresh fermented curds.Slight listerial growth and weak KE82 effects were found early in cheese milk fermentation. PubDate: Thu, 27 Aug 2020 00:00:00 GMT DOI: 10.4315/JFP-20-278 Issue No:Vol. 84, No. 1 (2020)
Authors:JUÁREZ ARANA CD; MARTÍNEZ PENICHE RA, MARTÍNEZ M, et al. Pages: 99 - 105 Abstract: ABSTRACTConsumption of seeds has increased in recent years due to their high nutrient content. However, Salmonella outbreaks associated with the consumption of low-water-activity food items have also increased, although these food items do not support microbial growth. The main goal of this study was to quantify microbial indicators and to determine the prevalence and content of Salmonella in chia, amaranth, and sesame seeds obtained from Mexican retail outlets. In addition, the behavior of this pathogen on seeds was evaluated. One hundred samples of each product (chia, amaranth, and sesame seeds) were collected from Queretaro City markets. Aerobic plate count, coliforms, and Escherichia coli bacteria were quantified, and the presence and number of Salmonella pathogens were also determined. Chia, amaranth, and sesame seeds (1 kg each) were inoculated with a cocktail of five Salmonella strains (∼6 log CFU mL−1) and stored at ambient temperature, and then populations of Salmonella were quantified. The median aerobic plate count contents in chia, amaranth, and sesame seeds were 2.1, 2.4, and 3.8 log CFU g−1, respectively, and the content of coliforms on the seeds ranged from 0.48 to 0.56 log most probable number (MPN) per g. E. coli was present at low concentrations in the three types of seeds. Salmonella was detected in chia (31%), amaranth (15%), and sesame (12%) seeds, and the population ranged from 0.48 to 0.56 log MPN g−1. Salmonella levels decreased through 240 days of storage, showing inactivation rates of 0.017, 0.011, and 0.016 log CFU h−1 in chia, amaranth, and sesame seeds, respectively. The high prevalence of Salmonella in the seeds highlights potential risks for consumers, particularly given that seeds are generally consumed without treatments guaranteeing pathogen inactivation.HIGHLIGHTSThe microbial indicator content on seeds showed high dispersion.E. coli was present on seeds at low concentrations (median 0.48 log MPN g−1).On average, the prevalence of Salmonella on seeds was 19.3%.Salmonella survived at least 240 days in chia, amaranth, and sesame seeds. PubDate: Thu, 03 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-19-595 Issue No:Vol. 84, No. 1 (2020)
Authors:MAHONEY NE; CHENG LW, PALUMBO JD. Pages: 106 - 112 Abstract: ABSTRACTAlmonds rejected as inedible are often used for production of almond oil. However, low-quality almonds are frequently contaminated with aflatoxins, and little is known regarding transfer of aflatoxins to almond oil during processing. In this study, oil was produced from reject almonds by hexane extraction. Of 19 almond samples that were naturally contaminated with aflatoxins, 17 oil samples contained measurable amounts of aflatoxins, and aflatoxin content of contaminated oil was correlated with aflatoxin content of the nuts. However, oil aflatoxin levels were not correlated with the oxidation level of the oil as measured by percent free fatty acids and peroxide value. Adsorbents used in oil refining were tested for their ability to remove aflatoxins from contaminated oil. Fuller's earth and bentonite were the most effective, removing 96 and 86% of total aflatoxins from contaminated oil samples, respectively. Treatment with diatomaceous earth, in contrast, had no effect on aflatoxin levels in oil. These results show that oil refining steps using mineral clay adsorbents may also function to remove aflatoxins from contaminated oil.HIGHLIGHTSAflatoxin present in contaminated almonds can contaminate oil from those nuts.Aflatoxin in oil correlated with aflatoxin in nuts, but not with oil quality.Mineral clay adsorbents were effective in removing aflatoxin during oil refining. PubDate: Thu, 03 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-229 Issue No:Vol. 84, No. 1 (2020)
Authors:BELIAS A; STRAWN LK, WIEDMANN M, et al. Pages: 113 - 121 Abstract: ABSTRACTA comprehensive understanding of foodborne pathogen diversity in preharvest environments is necessary to effectively track pathogens on farms and identify sources of produce contamination. As such, this study aimed to characterize Listeria diversity in wildlife feces and agricultural water collected from a New York state produce farm over a growing season. Water samples were collected from a pond (n = 80) and a stream (n = 52). Fecal samples (n = 77) were opportunistically collected from areas <5 m from the water sources; all samples were collected from a <0.5-km2 area. Overall, 86 (41%) and 50 (24%) of 209 samples were positive for Listeria monocytogenes and Listeria spp. (excluding L. monocytogenes), respectively. For each positive sample, one L. monocytogenes or Listeria spp. isolate was speciated by sequencing the sigB gene, thereby allowing for additional characterization based on the sigB allelic type. The 86 L. monocytogenes and 50 Listeria spp. isolates represented 8 and 23 different allelic types, respectively. A subset of L. monocytogenes isolates (n = 44) from pond water and pond-adjacent feces (representing an ∼5,000-m2 area) were further characterized by pulsed-field gel electrophoresis (PFGE); these 44 isolates represented 22 PFGE types, which is indicative of considerable diversity at a small spatial scale. Ten PFGE types were isolated more than once, suggesting persistence or reintroduction of PFGE types in this area. Given the small spatial scale, the prevalence of L. monocytogenes and Listeria spp., as well as the considerable diversity among isolates, suggests traceback investigations may be challenging. For example, traceback of finished product or processing facility contamination with specific subtypes to preharvest sources may require collection of large sample sets and characterization of a considerable number of isolates. Our data also support the adage “absence of evidence does not equal evidence of absence” as applies to L. monocytogenes traceback efforts at the preharvest level.HIGHLIGHTSThere is considerable Listeria diversity in the farm environment investigated.Listeria subtypes were reintroduced or persisted over the growing season.Four L. monocytogenes PFGE types were shared between feces and pond samples. PubDate: Fri, 11 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-179 Issue No:Vol. 84, No. 1 (2020)
Authors:ACUFF JC; WATERMAN K, RAMAKRISHNAN J, et al. Pages: 122 - 127 Abstract: ABSTRACTBacterial exposure to stress, such as reduced water activity (aw), can increase thermal resistance. Pathogen thermal resistance studies on low-aw foods use a variety of methods to inoculate food, as well as strategies to reduce aw, which can influence observations. This study investigated effects of culture preparation method and osmolyte-induced aw on thermal resistance of two Shiga toxin–producing Escherichia coli (STEC) strains (O121:H19 and O157:H7) challenged with isothermal conditions, determining D- and z-values for each isolate (56, 59, and 62°C). Tryptic soy broth (TSB) and agar (lawn cultures) were compared. D-values of broth cultures were significantly and consistently larger than those of lawn cultures, and O121 was significantly more resistant than O157, but only at 56°C (P < 0.05). To compare potential effects of aw on STEC thermal resistance, cells were suspended in osmolyte solutions with varying aw: high (TSB, aw 0.99), intermediate (61% glycerol or 26% NaCl, aw 0.75), and low (82% glycerol, aw 0.5). In most instances, STEC strains in high-aw broth exhibited greater heat resistance compared to reduced-aw solutions, with the exception of the glycerol intermediate-aw solution (aw 0.75). Magnitudes varied with strain and temperature. The z-values of lawn cultures were significantly lower than those of broth cultures (P < 0.05), but there were few differences between high-aw and reduced-aw samples. There were no significant differences of z-values based on strain type. These results highlight that thermal resistance can be affected by culture preparation and that osmolyte-induced changes to aw influence thermal inactivation of STEC by varying magnitudes. These results emphasize the challenges of extrapolating results from laboratory inactivation kinetic experiments to determine the inactivation of low-aw foods, especially those considered dry in nature.HIGHLIGHTSBroth-grown STEC had higher thermal resistance compared to plate-grown STEC.STEC O121 exhibited greater thermal resistance than O157 in various conditions.Osmolyte type and concentration variably affected STEC thermal resistance. PubDate: Fri, 11 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-122 Issue No:Vol. 84, No. 1 (2020)
Authors:SALAZAR-LLORENTE E; MORALES M, SORNOZA I, et al. Pages: 128 - 138 Abstract: ABSTRACTBacterial foodborne diseases are among the most important public health issues worldwide, but in Ecuador, reports on the microbiological quality of food are scarce. In this cross-sectional study, 450 samples of high-demand Ecuadorian food, including bolon, encebollado, sauces, ceviche, fruit, fruit juice, fruit salad, cheese, raw chicken, and ground beef, were collected from popular street markets in the cities of Guayaquil, Quito, and Cuenca. Populations of total aerobic mesophilic bacteria, total coliforms, fecal coliforms, Escherichia coli, Salmonella enterica, and Listeria monocytogenes were examined on composited samples by plate count following the local regulations (Norma Tecnica Ecuatoriana, Instituto Ecuatoriano de Normalización) for each kind of food. The individual and interaction effects of the city and food type on the levels of each bacterial group were assessed by two-way analysis of variance. Selected colonies from each culture were identified using Biolog OmniLog ID and sequencing of the V3 to V4 region on the 16S rRNA gene. Average total aerobic mesophilic bacteria, total coliform, fecal coliform, and E. coli levels were 5.10 ± 0.12, 2.50 ± 0.16, 1.09 ± 0.12, and 0.83 ± 0.12 log CFU/g or mL, respectively, with significant variations among the cities. The prevalence of Salmonella in chicken and sauces and L. monocytogenes in cheese and fruit salad was greater than 20%. Opportunistic pathogens including Klebsiella pneumoniae, Staphylococcus sciuri, and Enterococcus spp. were frequently identified in the samples from all three cities. High prevalence of spoilage microorganisms such as Bacillus amyloliquefaciens and biocontrol bacteria such as Lactococcus lactis was also observed. This is the first report on the microbiological quality of food from Ecuador.HIGHLIGHTSMicrobiological quality of 10 Ecuadorian food groups was examined.Prevalence of indicator microorganisms showed high levels of contamination in selected food groups.Foodborne pathogens were detected at high frequency in selected food groups.Significant intercity difference was observed for food microbiological quality. PubDate: Fri, 11 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-271 Issue No:Vol. 84, No. 1 (2020)
Authors:NIU L; WU Z, YANG L, et al. Pages: 139 - 146 Abstract: ABSTRACTUVC light-emitting diodes (UVC-LEDs) are a novel eco-friendly alternative source of UV light. This study evaluated the inactivation and membrane damage of spoilage yeast Saccharomyces cerevisiae by UVC-LEDs and their application in orange juice pasteurization. The results demonstrated that the antimicrobial effect of UVC-LED treatment against S. cerevisiae was enhanced by increased radiation dose. When the dose of UVC-LED radiation was 1,420 mJ/cm2, the population of S. cerevisiae in yeast extract peptone dextrose broth was reduced by 4.86 log CFU/mL. Through scanning electron microscopy and fluorescent staining, the structure and function of plasma membrane was observed to be severely damaged by UVC-LED treatment. The inactivation efficacy of UVC-LEDs against S. cerevisiae in orange juice also increased with increasing radiation dose. Radiation at 1,420 mJ/cm2 greatly reduced S. cerevisiae in orange juice by 4.44 log CFU/mL and did not induce remarkable changes in pH, total soluble solids, titratable acidity, and color parameters. However, the total phenolic content in orange juice was found to be significantly decreased by UVC-LEDs. These findings contribute to a better comprehension of UVC-LED inactivation and provide theoretical support for its potential application in fruit and vegetable juice processing.HIGHLIGHTSUVC-LED treatment inactivated S. cerevisiae in a dose-dependent manner.UVC-LED treatment induced release of intracellular nucleic acids and proteins.The cell membrane is one target for inactivation of S. cerevisiae by UVC-LED treatment.UVC-LEDs induced no remarkable changes in orange juice quality, with the exception of TPC. PubDate: Fri, 11 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-200 Issue No:Vol. 84, No. 1 (2020)
Authors:SEYEDABADI E; ARAN M, MOGHADDAM R. Pages: 147 - 151 Abstract: ABSTRACTOne of the most important products grown in Iran is walnut (Juglans regia L.), but it can be threatened by storage pests such as insects. Ozonation is an environmentally friendly method for killing pest insects; accordingly, ozone efficacy in the control of a pest species of walnut, Indian meal moth (Plodia interpunctella (Hübner)), was assessed in this research. The selected walnut samples were infested with larvae of Indian meal moth and then subjected to various combinations of ozone concentration (3, 4.5, and 6 ppm) and exposure time (20, 30, 40, and 50 min). After exposure to the treatment combinations, larval mortality rates and changes to the sensory properties (color, taste, smell, crispness, stiffness, and overall acceptability), indicating consumer preference, of the walnuts were evaluated. Our results revealed enhanced mortality rates of P. interpunctella with an increase in both ozone concentration and exposure time: 99% mortality was recorded at the concentration and exposure time of 6 ppm and 50 min, respectively. Sensory assessments of the samples showed that ozone treatments had no significant impacts on the color, taste, crispness, stiffness, and overall acceptability of the product. Also, few changes were recorded for its smell, which could be improved over time after being exposed to the air. We conclude that application of higher ozone concentrations might provide acceptable levels of insect pest control for stored walnuts with no associated reduced trade-off for their quality attributes.HIGHLIGHTSVarious ozone treatments were used against Plodia interpunctella in walnut storage.The quality degradation of walnuts was assessed in terms of sensory properties.High mortality rate and almost no quality change were achieved by ozone application.High ozone concentration and low exposure time was the most appropriate treatment. PubDate: Fri, 11 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-331 Issue No:Vol. 84, No. 1 (2020)
Authors:ESHETEA BB; ADDY N, EWING L, et al. Pages: 152 - 159 Abstract: ABSTRACTKitfo is a version of beef tartar widely consumed in the Ethiopian community. It is made from raw minced beef and a blend of powdered spice and butter. Although previous studies have shown that kitfo contains several bacteria that are of public health concern, the status of their antibiotic resistance is not known. In this study, the antibiotic resistance of bacterial isolates from 26 retail kitfo samples obtained from the Washington metropolitan area was analyzed. Characterization and antibiotic sensitivity of the isolates were determined by the Vitek 2 system and pulsed-field gel electrophoresis was used to delineate the intraspecies variations. Of the isolates, 59% were resistant to two or more antibiotics. Acinetobacter calcoaceticus and Pseudomonas luteola were multidrug resistant to the classes of β-lactam, cephalosporins, and nitrofurantoin. The antibiotic susceptibility profile of the isolates was cefazolin (59%), cefoxitin (50%), ampicillin (32%), and nitrofuran (18%). Most isolates (75%) were Enterobacteriaceae, whereas only 3.8 and 2.6% were Pseudomonadaceae and Moraxellaceae, respectively. Of the Enterobacteriaceae, Enterobacter cloacae, Escherichia coli, and Klebsiella spp. were the most predominant. All isolates except Klebsiella spp. showed high genetic variation (>65%). This study implicates for the first time kitfo as a potential reservoir of antibiotic-resistant bacteria.HIGHLIGHTSFifty-nine percent of the isolates were resistant to two or more antibiotics.Acinetobacter calcoaceticus and Pseudomonas luteola were multidrug resistant.Higher prevalence was seen of cefazolin- and cefoxitin-resistant Enterobacter and A. calcoaceticus.P. luteola resistant to cefepime (fourth-generation cephalosporin) was isolated. PubDate: Fri, 11 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-230 Issue No:Vol. 84, No. 1 (2020)
Authors:NGUYEN PT; JUÁREZ O, RESTAINO L. Pages: 160 - 168 Abstract: ABSTRACTArcobacter species are gram-negative rods that have been implicated in food- and waterborne illness. Although various cultural isolation methods have been proposed, the current procedures are unable to fully suppress the growth of background microbiota present in food samples, which inhibits Arcobacter isolation. The purpose of this study was to develop a selective enrichment broth and chromogenic plating medium to detect three Arcobacter species that have been recognized as emerging foodborne pathogens: Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii. The developed Nguyen-Restaino-Juárez (NRJ) Arcobacter detection system consists of a selective enrichment broth (NRJ-B) and a selective-differential plating medium (NRJ-M). The protocol of the detection method was determined by evaluating the growth of A. butzleri, A. cryaerophilus, and A. skirrowii under various temperatures (30, 35, and 42°C) and incubation (aerobic, microaerophilic, and anaerobic) conditions. Additionally, 47 Arcobacter strains and 39 non-Arcobacter strains were tested in inclusivity and exclusivity evaluations of NRJ-B and NRJ-M. Overall, the study determined that the optimal growth conditions of Arcobacter species using the NRJ Arcobacter detection system were aerobic incubation at 30°C. NRJ-B supported good growth of A. butzleri, A. cryaerophilus, and A. skirrowii while effectively suppressing the growth of non-Arcobacter strains after 48 h. Furthermore, NRJ-M yielded 97.8% inclusivity and 100.0% exclusivity using the tested strains and resulted in salmon-pigmented Arcobacter colonies (1.0 to 1.5 mm in diameter) after 72 h. The novel protocol is the first to develop a chromogenic plating medium for the isolation of Arcobacter species. This simple and accurate test method would greatly contribute to understanding the distribution of pathogenic Arcobacter species in food samples.HIGHLIGHTSThe chromogenic plating medium yielded 97.8% inclusivity and 100.0% exclusivity.Arcobacter species are differentiated by C2 esterase activity resulting in salmon colonies.Detection system provides a cost-effective procedure for Arcobacter detection. PubDate: Fri, 25 Sep 2020 00:00:00 GMT DOI: 10.4315/JFP-20-245 Issue No:Vol. 84, No. 1 (2020)
Authors:REMFRY SE; AMACHAWADI RG, SHI XX, et al. Pages: 169 - 180 Abstract: ABSTRACTShiga toxin–producing Escherichia coli (STEC) are major foodborne human pathogens that cause mild to hemorrhagic colitis, which could lead to complications of hemolytic uremic syndrome. Seven serogroups, O26, O45, O103, O111, O121, O145, and O157, account for the majority of the STEC illnesses in the United States. Shiga toxins 1 and 2, encoded by stx1 and stx2, respectively, and intimin, encoded by eae gene, are major virulence factors. Cattle are a major reservoir of STEC, but swine also harbor them in the hindgut and shed STEC in the feces. Our objectives were to use a culture method to isolate and identify major and minor serogroups of STEC in finisher pig feces. Shiga toxin genes were subtyped to assess public health implications of STEC. Fecal samples (n = 598) from finisher pigs, collected from 10 pig flows, were enriched in E. coli broth and tested for stx1, stx2, and eae by a multiplex PCR (mPCR) assay. Samples positive for stx1 or stx2 gene were subjected to culture methods, with or without immunomagnetic separation and plating on selective or nonselective media, for isolation and identification of stx-positive isolates. The culture method yielded a total of 178 isolates belonging to 23 serogroups. The three predominant serogroups were O8, O86, and O121. The 178 STEC strains included 26 strains with stx1a and 152 strains with stx2e subtypes. Strains with stx1a, particularly in association with eae (O26 and O103), have the potential to cause severe human infections. All stx2-positive isolates carried the subtype stx2e, a subtype that causes edema disease in swine, but is rarely involved in human infections. Several strains were also positive for genes that encode for enterotoxins, which are involved in neonatal and postweaning diarrhea in swine. In conclusion, our study showed that healthy finisher pigs harbored and shed several serogroups of E. coli carrying virulence genes involved in neonatal diarrhea, postweaning diarrhea, and edema disease, but prevalence of STEC of public health importance was low.HIGHLIGHTSSwine harbor Shiga toxin–producing Escherichia coli (STEC) and shed them in the feces.Swine STEC could be a source of foodborne infections in humans.Culture method identified major and minor serogroups of STEC.Major serogroups of STEC included O8, O86, and O121.A majority of the STEC possessed Shiga toxin 2e, which is not a major public threat. PubDate: Thu, 01 Oct 2020 00:00:00 GMT DOI: 10.4315/JFP-20-329 Issue No:Vol. 84, No. 1 (2020)
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