scholarly journals Exponentially Increased Thermal Resistance ofSalmonellaspp. andEnterococcus faeciumat Reduced Water Activity

2018 ◽  
Vol 84 (8) ◽  
pp. e02742-17 ◽  
Author(s):  
Shuxiang Liu ◽  
Juming Tang ◽  
Ravi Kiran Tadapaneni ◽  
Ren Yang ◽  
Mei-Jun Zhu
Keyword(s):  
Relative Humidity ◽  
Thermal Resistance ◽  
Silicon Dioxide ◽  
Linear Relationship ◽  
Water Activity ◽  
Enterococcus Faecium ◽  
Content Type ◽  
Low Moisture Foods ◽  
Log Linear ◽  
Insight Into

ABSTRACTSalmonellaspp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters ofSalmonellaspp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (aw, treatment temperature) plays an important role in the sharply increased thermal resistance ofSalmonella entericaserovar Enteritidis PT 30 and its potential surrogateEnterococcus faeciumNRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding aw,80°Cvalues for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model (R2, 0.83 to 0.97). Reductions in the aw,80°Cvalues of bacterial cells exponentially increased theD80°C(the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values forS. Enteritidis andE. faeciumon silicon dioxide. The log-linear relationship between theD80°Cvalues for each strain in silicon dioxide and its aw,80°Cvalues was also verified for organic wheat flour.E. faeciumshowed consistently higherD80°Cvalues thanS. Enteritidis over the aw,80°Crange tested. The estimated zaw(the change in aw,80°Cneeded to changeD80°Cby 1 log) values ofS. Enteritidis andE. faeciumwere 0.31 and 0.28, respectively. This study provides insight into the interpretation ofSalmonellathermal resistance that could guide the development and validation of thermal processing of low-moisture foods.IMPORTANCEIn this paper, we established that the thermal resistance of the pathogenS. Enteritidis and its surrogateEnterococcus faecium, as reflected byDvalues at 80°C, increases sharply with decreasing relative humidity in the environment. The log-linear relationship between theD80°Cvalues of each strain in silicon dioxide and its aw,80°Cvalues was also verified for organic wheat flour. The results provide new quantitative insight into the way in which the thermal resistance of microorganisms changes in low-moisture systems, and they should aid in the development of effective thermal treatment strategies for pathogen control in low-moisture foods.

Influence of low water activity on the thermal resistance of Salmonella Enteritidis PT30 and Enterococcus faecium as its surrogate in egg powders

2020 ◽  
pp. 108201322093787
Author(s):  
Marco E Pérez-Reyes ◽  
Xu Jie ◽  
Mei-Jun Zhu ◽  
Juming Tang ◽  
Gustavo V Barbosa-Cánovas
Keyword(s):  
Thermal Resistance ◽  
Linear Relationship ◽  
Water Activity ◽  
Enterococcus Faecium ◽  
Salmonella Enteritidis ◽  
Thermal Treatments ◽  
Thermal Death ◽  
Industrial Food Production ◽  
Log Linear ◽  
The Impact

Egg powders are increasingly popular ingredients, due to their functionality and compactness, in industrial food production and preparation at homes. However, there is a lack of studies that evaluate the thermal resistance of Salmonella Enteritidis PT30 and its potential surrogate Enterococcus faecium NRRL B-2354 in egg powders. This study examined the log-linear relationship between the thermal resistance of Salmonella Enteritidis (D-value) and the water activity (aw) of egg powders. The changes of aw in the egg powders with temperature were measured using a Vapor Sorption Analyzer and a high-temperature cell. The D80 ℃-value of S. Enteritidis PT30 and E. faecium inoculated in the egg powders preconditioned to three aw levels (0.3, 0.45, and 0.6) at 20 ℃ were determined using aluminum thermal death test cells. The aw values increased (P < 0.05) in all three egg powders when the temperature of the samples was raised from room temperature to 80 ℃. The D80 ℃-values ranged from 5.3 ± 0.1 to 25.9 ± 0.2 min for S. Enteritidis while 10.4 ± 0.4 to 43.8 ± 0.4 for E. faecium in samples of the three different aw levels. S. Enteritidis PT30 showed a log-linear relationship between D80 ℃-values and aw80 ℃ for the egg powders. This study contributes to our understanding of the impact of aw on the development of thermal treatments for low-moisture foods.

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

2019 ◽  
Vol 82 (7) ◽  
pp. 1110-1115 ◽  
Author(s):  
NURUL HAWA AHMAD ◽  
CEMRE ÖZTABAK ◽  
BRADLEY P. MARKS ◽  
ELLIOT T. RYSER
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Enterococcus Faecium ◽  
Thermal Inactivation ◽  
Experimental Conditions ◽  
Time Points ◽  
Test Cells ◽  
Low Moisture Foods ◽  
Differential Medium ◽  
Resistance To Heat

ABSTRACTDry inoculation (DI) methods using a dry carrier have gained considerable interest for assessing thermal inactivation of Salmonella and other microorganisms in low-moisture foods. However, the effect of carrier residues on microbial resistance to heat remains largely unknown. This study aimed to determine the effect of talc powder on thermal resistance of Enterococcus faecium NRRL-B2354 (a Salmonella surrogate) in almond meal at 0.45 water activity (aw). Whole almonds were either immersed in an E. faecium suspension for wet inoculation (WI) or mixed with inoculated talc powder for DI. Two additional experimental conditions, inoculation of WI almond meal with added uninoculated talc (WT) and inoculated talc powder alone, were conducted. After WI, DI, and WT, the almonds were equilibrated to 0.45 aw, ground into a meal, and reequilibrated to 0.45 aw. Isothermal treatments were performed by heating almond meal (about 1 g) in aluminum test cells in a water bath at 80°C, with samples collected at more than five sequential time points from triplicate isothermal runs. E. faecium was enumerated by immediately cooling, diluting, and plating the samples on a nonselective or differential medium. E. faecium was more thermally resistant in DI (D80°C: 63.5 ± 1.9 min) compared with WI almond meal (D80°C: 40.5 ± 1.0 min; P &lt; 0.05), but the resistance in WT almond meal (46.9 ± 0.9 min) was between and different from (P &lt; 0.05) both DI and WI. E. faecium was less resistant in talc powder alone (20.6 ± 1.1 min) compared with all other almond meal samples. Overall, residual talc affected the thermal resistance of E. faecium. Therefore, when determining thermal resistance or validating commercial processes, carriers such as talc should not be used for inoculation of low-moisture foods without first knowing their impact on the target organism.HIGHLIGHTS

Development of a Dry Inoculation Method for Thermal Challenge Studies in Low-Moisture Foods by Using Talc as a Carrier for Salmonella and a Surrogate (Enterococcus faecium)

2015 ◽  
Vol 78 (6) ◽  
pp. 1106-1112 ◽  
Author(s):  
ELENA ENACHE ◽  
AI KATAOKA ◽  
D. GLENN BLACK ◽  
CARLA D. NAPIER ◽  
RICHARD PODOLAK ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Water Activity ◽  
Enterococcus Faecium ◽  
Thermal Inactivation ◽  
Death Time ◽  
Significant Difference ◽  
Growth Method ◽  
Low Moisture Foods ◽  
Inoculum Preparation

The objective of this study was to obtain dry inocula of Salmonella Tennessee and Enterococcus faecium, a surrogate for thermal inactivation of Salmonella in low-moisture foods, and to compare their thermal resistance and stability over time in terms of survival. Two methods of cell growth were compared: cells harvested from a lawn on tryptic soy agar (TSA-cells) and from tryptic soy broth (TSB-cells). Concentrated cultures of each organism were inoculated onto talc powder, incubated at 35°C for 24 h, and dried for additional 24 h at room temperature (23 ± 2°C) to achieve a final water activity of ≤0.55 before sieving. Cell reductions of Salmonella and E. faecium during the drying process were between 0.14 and 0.96 log CFU/g, depending on growth method used. There was no difference between microbial counts at days 1 and 30. Heat resistance of the dry inoculum on talc inoculated into a model peanut paste (50% fat and 0.6 water activity) was determined after 1 and 30 days of preparation, using thermal death time tests conducted at 85°C. For Salmonella, there was no significant difference between the thermal resistance (D85°C) for the TSB-cells and TSA-cells (e.g. day 1 cells D85°C = 1.05 and 1.07 min, respectively), and there was no significant difference in D85°C between dry inocula on talc used either 1 or 30 days after preparation (P &gt; 0.05). However, the use the dry inocula of E. faecium yielded different results: the TSB-grown cells had a significantly (P &lt; 0.05) greater heat resistance than TSA-grown cells (e.g. D85°C for TSB-cells = 3.42 min versus 2.60 min for TSA-cells). E. faecium had significantly (P &lt; 0.05) greater heat resistance than Salmonella Tennessee regardless what cell type was used for dry inoculum preparation; therefore, it proved to be a conservative but appropriate surrogate for thermal inactivation of Salmonella in low-moisture food matrices under the tested conditions.

Influence of Water Activity on Thermal Resistance of Microorganisms in Low-Moisture Foods: A Review

2016 ◽  
Vol 15 (2) ◽  
pp. 353-370 ◽  
Author(s):  
Roopesh M. Syamaladevi ◽  
Juming Tang ◽  
Rossana Villa-Rojas ◽  
Shyam Sablani ◽  
Brady Carter ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Influence Of Water ◽  
Low Moisture Foods

scholarly journals Increased Water Activity Reduces the Thermal Resistance of Salmonella enterica in Peanut Butter

2013 ◽  
Vol 79 (15) ◽  
pp. 4763-4767 ◽  
Author(s):  
Yingshu He ◽  
Ye Li ◽  
Joelle K. Salazar ◽  
Jingyun Yang ◽  
Mary Lou Tortorello ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Thermal Resistance ◽  
Water Activity ◽  
Salmonella Enterica ◽  
Morphological Changes ◽  
Peanut Butter ◽  
Content Type ◽  
The Difference ◽  
Scanning Electron

ABSTRACTIncreased water activity in peanut butter significantly (P< 0.05) reduced the heat resistance of desiccation-stressedSalmonella entericaserotypes treated at 90°C. The difference in thermal resistance was less notable when strains were treated at 126°C. Using scanning electron microscopy, we observed minor morphological changes ofS. entericacells resulting from desiccation and rehydration processes in peanut oil.

Improving design of thermal water activity cell to study thermal resistance of Salmonella in low-moisture foods

LWT ◽  
2018 ◽  
Vol 92 ◽  
pp. 371-379 ◽  
Author(s):  
Ravi Kiran Tadapaneni ◽  
Jie Xu ◽  
Ren Yang ◽  
Juming Tang
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Thermal Water ◽  
Low Moisture Foods

scholarly journals Restricted Gene Flow among Hospital Subpopulations of Enterococcus faecium

mBio ◽  
2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Rob J. L. Willems ◽  
Janetta Top ◽  
Willem van Schaik ◽  
Helen Leavis ◽  
Marc Bonten ◽  
...  
Keyword(s):  
Population Structure ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Enterococcus Faecium ◽  
Population Genetic ◽  
Effective Control ◽  
Phylogenomic Analysis ◽  
Content Type ◽  
Sequence Types ◽  
Insight Into

ABSTRACT Enterococcus faecium has recently emerged as an important multiresistant nosocomial pathogen. Defining population structure in this species is required to provide insight into the existence, distribution, and dynamics of specific multiresistant or pathogenic lineages in particular environments, like the hospital. Here, we probe the population structure of E. faecium using Bayesian-based population genetic modeling implemented in Bayesian Analysis of Population Structure (BAPS) software. The analysis involved 1,720 isolates belonging to 519 sequence types (STs) (491 for E. faecium and 28 for Enterococcus faecalis). E. faecium isolates grouped into 13 BAPS (sub)groups, but the large majority (80%) of nosocomial isolates clustered in two subgroups (2-1 and 3-3). Phylogenetic and eBURST analysis of BAPS groups 2 and 3 confirmed the existence of three separate hospital lineages (17, 18, and 78), highlighting different evolutionary trajectories for BAPS 2-1 (lineage 78) and 3-3 (lineage 17 and lineage 18) isolates. Phylogenomic analysis of 29 E. faecium isolates showed agreement between BAPS assignment of STs and their relative positions in the phylogenetic tree. Odds ratio calculation confirmed the significant association between hospital isolates with BAPS 3-3 and lineages 17, 18, and 78. Admixture analysis showed a scarce number of recombination events between the different BAPS groups. For the E. faecium hospital population, we propose an evolutionary model in which strains with a high propensity to colonize and infect hospitalized patients arise through horizontal gene transfer. Once adapted to the distinct hospital niche, this subpopulation becomes isolated, and recombination with other populations declines. IMPORTANCE Multiresistant Enterococcus faecium has become one of the most important nosocomial pathogens, causing increasing numbers of nosocomial infections worldwide. Here, we used Bayesian population genetic analysis to identify groups of related E. faecium strains and show a significant association of hospital and farm animal isolates to different genetic groups. We also found that hospital isolates could be divided into three lineages originating from sequence types (STs) 17, 18, and 78. We propose that, driven by the selective pressure in hospitals, the three hospital lineages have arisen through horizontal gene transfer, but once adapted to the distinct pathogenic niche, this population has become isolated and recombination with other populations declines. Elucidation of the population structure is a prerequisite for effective control of multiresistant E. faecium since it provides insight into the processes that have led to the progressive change of E. faecium from an innocent commensal to a multiresistant hospital-adapted pathogen.

Effects of Inoculation Procedures on Variability and Repeatability of Salmonella Thermal Resistance in Wheat Flour

2016 ◽  
Vol 79 (11) ◽  
pp. 1833-1839 ◽  
Author(s):  
IAN M. HILDEBRANDT ◽  
BRADLEY P. MARKS ◽  
ELLIOT T. RYSER ◽  
ROSSANA VILLA-ROJAS ◽  
JUMING TANG ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Wheat Flour ◽  
Thermal Inactivation ◽  
Culture Method ◽  
Isothermal Treatment ◽  
Inactivation Kinetics ◽  
Inoculation Methods ◽  
Low Moisture Foods ◽  
D Values

ABSTRACT Limited prior research has shown that inoculation methods affect thermal resistance of Salmonella in low-moisture foods; however, these effects and their repeatability have not been systematically quantified. Consequently, method variability across studies limits utility of individual data sets and cross-study comparisons. Therefore, the objective was to evaluate the effects of inoculation methodologies on stability and thermal resistance of Salmonella in a low-moisture food (wheat flour), and the repeatability of those results, based on data generated by two independent laboratories. The experimental design consisted of a cross-laboratory comparison, both conducting isothermal Salmonella inactivation studies in wheat flour (~0.45 water activity, 80°C), utilizing five different inoculation methods: (i) broth-based liquid inoculum, (ii) lawn-based liquid inoculum, (iii) lawn-based pelletized inoculum, (iv) direct harvest of lawn culture with wheat flour, and (v) fomite transfer of a lawn culture. Inoculated wheat flour was equilibrated ~5 days to ~0.45 water activity and then was subjected to isothermal treatment (80°C) in aluminum test cells. Results indicated that inoculation method impacted repeatability, population stability, and inactivation kinetics (α = 0.05), regardless of laboratory. Salmonella inoculated with the broth-based liquid inoculum method and the fomite transfer of a lawn culture method exhibited instability during equilibration. Lawn-based cultures resulted in stable populations prior to thermal treatment; however, the method using direct harvest of lawn culture with wheat flour yielded different D-values across the laboratories (α = 0.05), which was attributed to larger potential impact of operator variability. The lawn-based liquid inoculum and the lawn-based pelletized inoculum methods yielded stable inoculation levels and repeatable D-values (~250 and ~285 s, respectively). Also, inoculation level (3 to 8 log CFU/g) did not affect D-values (using the lawn-based liquid inoculum method). Overall, the results demonstrate that inoculation methods significantly affect Salmonella population kinetics and subsequent interpretation of thermal inactivation data for low-moisture foods.

Survival and Thermal Resistance of Salmonella Enteritidis PT 30 on Almonds after Long-Term Storage

2019 ◽  
Vol 82 (2) ◽  
pp. 194-199 ◽  
Author(s):  
PICHAMON LIMCHAROENCHAT ◽  
MICHAEL K. JAMES ◽  
BRADLEY P. MARKS
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Salmonella Enteritidis ◽  
Thermal Treatments ◽  
Long Term Storage ◽  
Group I ◽  
Log Linear ◽  
Term Storage ◽  
Salmonella Survival

ABSTRACT Salmonella survival and thermal resistance on the surface of almond kernels were evaluated after periods of storage. Almond kernels were inoculated with Salmonella Enteritidis PT 30 and equilibrated to 0.45 water activity. Samples were separated into two groups (I and II) and stored in sealed metal cans at room temperature. Group I samples (stored 7, 15, 27, and 68 weeks) were re-equilibrated in controlled humidity chambers to 0.45 water activity before performing the thermal treatments after each storage period, but group II samples (stored 70 and 103 weeks) were thermally treated immediately after the cans were opened. For thermal treatments, individual almond kernels were vacuum sealed in thin plastic bags, heated isothermally in a water bath (80°C) for nine intervals, immediately cooled in an ice bath, and assayed for surviving Salmonella. Log-linear and Weibull models were fit to the inactivation data. Salmonella population decreased (P &lt; 0.05) more than 2 log CFU/g during the long-term storage. Salmonella survival in group II at 70 weeks (7.3 log CFU/g) was higher (P &lt; 0.05) than in group I (which had been re-equilibrated multiple times) at 68 weeks (6.2 log CFU/g). However, the thermal resistance of Salmonella Enteritidis PT 30 did not decrease (P &gt; 0.05) for up to 68 weeks of storage, and the log-linear model best described the thermal inactivation data. Overall, the results suggest that re-equilibrating almonds (group I) multiple times may have increased the rate of reduction of Salmonella populations during long-term storage. However, Salmonella thermal resistance on almonds appears to be essentially unaffected by long-term storage, which is important information for designing and conducting validation studies for pathogen control processes.

Sign in / Sign up

Export Citation Format

Share Document