Probabilistic Models to Predict Listeria monocytogenes Growth at Low Concentrations of NaNO2 and NaCl in Frankfurters

Eunji Gwak,Mi Hwa Oh,Beom Young Park,Heeyoung Lee,Soomin Lee,Jimyeong Ha,Jeeyeon Lee,Sejeong Kim,Kyoung Hee Choi 한국축산식품학회 2015 한국축산식품학회지 Vol.35 No.6

This study developed probabilistic models to describe Listeria monocytogenes growth responses in meat products with low concentrations of NaNO2 and NaCl. A five-strain mixture of L. monocytogenes was inoculated in NBYE (nutrient broth plus 0.6% yeast extract) supplemented with NaNO2 (0-141 ppm) and NaCl (0-1.75%). The inoculated samples were then stored under aerobic and anaerobic conditions at 4, 7, 10, 12, and 15°C for up to 60 d. Growth response data [growth (1) or no growth (0)] for each combination were determined by turbidity. The growth response data were analyzed using logistic regression to predict the growth probability of L. monocytogenes as a function of NaNO2 and NaCl. The model performance was validated with the observed growth responses. The effect of an obvious NaNO2 and NaCl combination was not observed under aerobic storage condition, but the antimicrobial effect of NaNO2 on the inhibition of L. monocytogenes growth generally increased as NaCl concentration increased under anaerobic condition, especially at 7-10°C. A single application of NaNO2 or NaCl significantly (p<0.05) inhibited L. monocytogenes growth at 4-15°C, but the combination of NaNO2 or NaCl more effectively (p<0.05) inhibited L. monocytogenes growth than single application of either compound under anaerobic condition. Validation results showed 92% agreement between predicted and observed growth response data. These results indicate that the developed model is useful in predicting L. monocytogenes growth response at low concentrations of NaNO2 and NaCl, and the antilisterial effect of NaNO2 increased by NaCl under anaerobic condition.

Probabilistic Models to Predict Listeria monocytogenes Growth at Low Concentrations of NaNO₂ and NaCl in Frankfurters

Gwak, Eunji,Oh, Mi-Hwa,Park, Beom-Young,Lee, Heeyoung,Lee, Soomin,Ha, Jimyeong,Lee, Jeeyeon,Kim, Sejeong,Choi, Kyoung-Hee,Yoon, Yohan Korean Society for Food Science of Animal Resource 2015 한국축산식품학회지 Vol.35 No.6

This study developed probabilistic models to describe Listeria monocytogenes growth responses in meat products with low concentrations of NaNO₂ and NaCl. A five-strain mixture of L. monocytogenes was inoculated in NBYE (nutrient broth plus 0.6% yeast extract) supplemented with NaNO₂ (0-141 ppm) and NaCl (0-1.75%). The inoculated samples were then stored under aerobic and anaerobic conditions at 4, 7, 10, 12, and 15℃ for up to 60 d. Growth response data [growth (1) or no growth (0)] for each combination were determined by turbidity. The growth response data were analyzed using logistic regression to predict the growth probability of L. monocytogenes as a function of NaNO₂ and NaCl. The model performance was validated with the observed growth responses. The effect of an obvious NaNO₂ and NaCl combination was not observed under aerobic storage condition, but the antimicrobial effect of NaNO₂ on the inhibition of L. monocytogenes growth generally increased as NaCl concentration increased under anaerobic condition, especially at 7-10℃. A single application of NaNO₂ or NaCl significantly (p<0.05) inhibited L. monocytogenes growth at 4-15℃, but the combination of NaNO₂ or NaCl more effectively (p<0.05) inhibited L. monocytogenes growth than single application of either compound under anaerobic condition. Validation results showed 92% agreement between predicted and observed growth response data. These results indicate that the developed model is useful in predicting L. monocytogenes growth response at low concentrations of NaNO₂ and NaCl, and the antilisterial effect of NaNO₂ increased by NaCl under anaerobic condition.

Twinned nanoporous gold with enhanced tensile strength

Gwak, Eun-Ji,Jeon, Hansol,Song, Eunji,Kang, Na-Ri,Kim, Ju-Young Elsevier 2018 Acta materialia Vol.155 No.-

<P><B>Abstract</B></P> <P>Enhancing tensile strength is crucial to increasing the applicability of nanoporous materials including nanoporous gold (np-Au) that show mechanical weakness because of their nanoporous structure despite other superior characteristics. We fabricated twinned and textured np-Au foils with an average twin spacing of 7.9 nm. The foils exhibit an ultimate tensile strength (UTS) of 87.5 MPa when the loading axis is normal to the twin boundaries. This UTS value is approximately three times greater than that for np-Au with rare twins of 27.4 MPa. The high UTS can be ascribed to the twin boundaries acting as effective barriers to dislocation slip, resulting in the strain-hardening of the load-bearing ligaments.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

가상환경 데이터 및 정적 장애물 추적을 활용한 자율주행 차량 속도 추정에 관한 연구

송은지(Eunji Song),곽석우(Seoku Gwak),안승윤(Seungyun An),황성호(Sung-Ho Hwang) 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11

Mathematical Model for Predicting the Growth Probability of Staphylococcus aureus in Combinations of NaCl and NaNO2 under Aerobic or Evacuated Storage Conditions

Jeeyeon Lee,Eunji Gwak,Jimyeong Ha,Sejeong Kim,Soomin Lee,Heeyoung Lee,Mi-Hwa Oh,Beom-Young Park,Nam Su Oh,Kyoung-Hee Choi,Yohan Yoon 한국축산식품학회 2016 한국축산식품학회지 Vol.36 No.6

The objective of this study was to describe the growth patterns of Staphylococcus aureus in combinations of NaCl and NaNO2, using a probabilistic model. A mixture of S. aureus strains (NCCP10826, ATCC13565, ATCC14458, ATCC23235, and ATCC27664) was inoculated into nutrient broth plus NaCl (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and NaNO2 (0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm). The samples were then incubated at 4, 7, 10, 12 and 15°C for up to 60 d under aerobic or vacuum conditions. Growth responses [growth (1) or no growth (0)] were then determined every 24 h by turbidity, and analyzed to select significant parameters (p<0.05) by a stepwise selection method, resulting in a probabilistic model. The developed models were then validated with observed growth responses. S. aureus growth was observed only under aerobic storage at 10-15°C. At 10-15°C, NaCl and NaNO2 did not inhibit S. aureus growth at less than 1.25% NaCl. Concentration dependency was observed for NaCl at more than 1.25%, but not for NaNO2. The concordance percentage between observed and predicted growth data was approximately 93.86%. This result indicates that S. aureus growth can be inhibited in vacuum packaging and even aerobic storage below 10°C. Furthermore, NaNO2 does not effectively inhibit S. aureus growth.

Kinetic Behavior of Salmonella on Low NaNO₂ Sausages during Aerobic and Vacuum Storage

Ha, Jimyeong,Gwak, Eunji,Oh, Mi-Hwa,Park, Beomyoung,Lee, Jeeyeon,Kim, Sejeong,Lee, Heeyoung,Lee, Soomin,Yoon, Yohan,Choi, Kyoung-Hee Korean Society for Food Science of Animal Resource 2016 한국축산식품학회지 Vol.36 No.2

This study evaluated the growth kinetics of Salmonella spp. in processed meat products formulated with low sodium nitrite (NaNO₂). A 5-strain mixture of Salmonella spp. was inoculated on 25-g samples of sausages formulated with sodium chloride (NaCl) (1.0%, 1.25%, and 1.5%) and NaNO₂ (0 and 10 ppm) followed by aerobic or vacuum storage at 10℃ and 15℃ for up to 816 h or 408 h, respectively. The bacterial cell counts were enumerated on xylose lysine deoxycholate agar, and the modified Gompertz model was fitted to the Salmonella cell counts to calculate the kinetic parameters as a function of NaCl concentration on the growth rate (GR; Log CFU/g/h) and lag phase duration (LPD; h). A linear equation was then fitted to the parameters to evaluate the effect of NaCl concentration on the kinetic parameters. The GR values of Salmonella on sausages were higher (p<0.05) with 10 ppm NaNO₂ concentration than with 0 ppm NaNO₂. The GR values of Salmonella decreased (p<0.05) as NaCl concentration increased, especially at 10℃. This result indicates that 10 ppm NaNO₂ may increase Salmonella growth at low NaCl concentrations, and that NaCl plays an important role in inhibiting Salmonella growth in sausages with low NaNO₂.

Kinetic Behavior of Salmonella on Low NaNO2 Sausages during Aerobic and Vacuum Storage

Jimyeong Ha,Eunji Gwak,Mi Hwa Oh,Beomyoung Park,Jeeyeon Lee,Sejeong Kim,Heeyoung Lee,Soomin Lee,Yohan Yoon 한국축산식품학회 2016 한국축산식품학회지 Vol.36 No.2

Abstract This study evaluated the growth kinetics of Salmonella spp. in processed meat products formulated with low sodium nitrite (NaNO2). A 5-strain mixture of Salmonella spp. was inoculated on 25-g samples of sausages formulated with sodium chloride (NaCl) (1.0%, 1.25%, and 1.5%) and NaNO2 (0 and 10 ppm) followed by aerobic or vacuum storage at 10°C and 15°C for up to 816 h or 408 h, respectively. The bacterial cell counts were enumerated on xylose lysine deoxycholate agar, and the modified Gompertz model was fitted to the Salmonella cell counts to calculate the kinetic parameters as a function of NaCl concentration on the growth rate (GR; Log CFU/g/h) and lag phase duration (LPD; h). A linear equation was then fitted to the parameters to evaluate the effect of NaCl concentration on the kinetic parameters. The GR values of Salmonella on sausages were higher (p<0.05) with 10 ppm NaNO2 concentration than with 0 ppm NaNO2. The GR values of Salmonella decreased (p<0.05) as NaCl concentration increased, especially at 10oC. This result indicates that 10 ppm NaNO2 may increase Salmonella growth at low NaCl concentrations, and that NaCl plays an important role in inhibiting Salmonella growth in sausages with low NaNO2.

Mathematical Model for Predicting the Growth Probability of Staphylococcus aureus in Combinations of NaCl and NaNO₂ under Aerobic or Evacuated Storage Conditions

Lee, Jeeyeon,Gwak, Eunji,Ha, Jimyeong,Kim, Sejeong,Lee, Soomin,Lee, Heeyoung,Oh, Mi-Hwa,Park, Beom-Young,Oh, Nam Su,Choi, Kyoung-Hee,Yoon, Yohan Korean Society for Food Science of Animal Resource 2016 한국축산식품학회지 Vol.36 No.6

The objective of this study was to describe the growth patterns of Staphylococcus aureus in combinations of NaCl and $NaNO_2$, using a probabilistic model. A mixture of S. aureus strains (NCCP10826, ATCC13565, ATCC14458, ATCC23235, and ATCC27664) was inoculated into nutrient broth plus NaCl (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and $NaNO_2$ (0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm). The samples were then incubated at 4, 7, 10, 12 and $15^{\circ}C$ for up to 60 d under aerobic or vacuum conditions. Growth responses [growth (1) or no growth (0)] were then determined every 24 h by turbidity, and analyzed to select significant parameters (p<0.05) by a stepwise selection method, resulting in a probabilistic model. The developed models were then validated with observed growth responses. S. aureus growth was observed only under aerobic storage at $10-15^{\circ}C$. At $10-15^{\circ}C$, NaCl and $NaNO_2$ did not inhibit S. aureus growth at less than 1.25% NaCl. Concentration dependency was observed for NaCl at more than 1.25%, but not for $NaNO_2$. The concordance percentage between observed and predicted growth data was approximately 93.86%. This result indicates that S. aureus growth can be inhibited in vacuum packaging and even aerobic storage below $10^{\circ}C$. Furthermore, $NaNO_2$ does not effectively inhibit S. aureus growth.

Microstructural effect on time-dependent plasticity of nanoporous gold

Kang, Na-Ri,Gwak, Eun-Ji,Jeon, Hansol,Song, Eunji,Kim, Ju-Young Elsevier 2018 International journal of plasticity Vol.109 No.-

<P><B>Abstract</B></P> <P>Annealed, prestrained, and ball-milled nanoporous gold (np-Au) samples were prepared. Since the microstructures of the precursor alloys, such as the crystallographic orientation and grain size, were mostly preserved during the dealloying process, prestrained np-Au is believed to have higher initial dislocation density, and ball-milled np-Au is believed to have higher densities of initial dislocation and grain boundary comparing to annealed np-Au. The time-dependent deformation behavior of np-Au samples with various microstructures was characterized with two parameters; creep strain exponent <I>n</I> and activation volume <SUP> V ∗ </SUP> using spherical nanoindentation creep tests. We found that primary mechanism of time-dependent plasticity for annealed and prestrained np-Au samples is dislocation slip and that for ball-milled np-Au sample is grain boundary sliding. In dislocation slip-dominant time-dependent deformation in np-Au, a higher initial dislocation density lowers <I>n</I> and <SUP> V ∗ </SUP> . In grain boundary sliding-dominant time-dependent deformation in np-Au, the values of <I>n</I> and <SUP> V ∗ </SUP> are similar to those for dislocation slip-dominant time-dependent deformation; however, the creep strain rate in quasi-steady-state is higher than that for dislocation slip-dominant time-dependent deformation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three nanoporous gold (np-Au) samples with different microstructure were fabricated. </LI> <LI> Time-dependent plasticity was characterized by spherical nanoindentation creep test. </LI> <LI> Primary mechanism of time-dependent plasticity was found to be dependent on the microstructure of np-Au. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Probabilistic Models to Predict the Growth Initiation Time for Pseudomonas spp. in Processed Meats Formulated with NaCl and NaNO₂

Jo, Hyunji,Park, Beomyoung,Oh, Mihwa,Gwak, Eunji,Lee, Heeyoung,Lee, Soomin,Yoon, Yohan Korean Society for Food Science of Animal Resource 2014 한국축산식품학회지 Vol.34 No.6

This study developed probabilistic models to determine the initiation time of growth of Pseudomonas spp. in combinations with $NaNO_2$ and NaCl concentrations during storage at different temperatures. The combination of 8 NaCl concentrations (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and 9 $NaNO_2$ concentrations (0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm) were prepared in a nutrient broth. The medium was placed in the wells of 96-well microtiter plates, followed by inoculation of a five-strain mixture of Pseudomonas in each well. All microtiter plates were incubated at 4, 7, 10, 12, and $15^{\circ}C$ for 528, 504, 504, 360 and 144 h, respectively. Growth (growth initiation; GI) or no growth was then determined by turbidity every 24 h. These growth response data were analyzed by a logistic regression to produce growth/no growth interface of Pseudomonas spp. and to calculate GI time. NaCl and $NaNO_2$ were significantly effective (p<0.05) on inhibiting Pseudomonas spp. growth when stored at $4-12^{\circ}C$. The developed model showed that at lower NaCl concentration, higher $NaNO_2$ level was required to inhibit Pseudomonas growth at $4-12^{\circ}C$. However, at $15^{\circ}C$, there was no significant effect of NaCl and $NaNO_2$. The model overestimated GI times by $58.2{\pm}17.5$ to $79.4{\pm}11%$. These results indicate that the probabilistic models developed in this study should be useful in calculating the GI times of Pseudomonas spp. in combination with NaCl and $NaNO_2$ concentrations, considering the over-prediction percentage.