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Effect of water activity on inactivation of Listeria monocytogenes and lactate dehydrogenase during high pressure processing.
Int J Food Microbiol. 2008 May 10; 124(1):21-6.IJ

Abstract

The aim of this study was to investigate the effect of water activity (aw) on the inactivation of Listeria monocytogenes and lactate dehydrogenase (LDH) during high pressure processing (HPP). For microbial inactivation lyophilized cells of L. monocytogenes 19,115 were left dry or were suspended in 10 ml of 0.1% peptone water, 10 ml of glycerol, or mixtures of glycerol and peptone water. All samples of various aws were high pressure (HP) processed at ambient temperature at 600 MPa for 300 s. Following HPP, samples were serially diluted in 0.1% peptone and spread-plated on Tryptic Soy agar supplemented with Yeast Extract. For enzyme inactivation, 4.2 mg of lyophilized LDH was suspended in 2 ml of 100 mM phosphate buffer (pH 7.4), 2 ml of peptone water or glycerol, or in 2 ml mixtures of glycerol and peptone water. A lyophilized sample with no added liquid was also included. All enzyme samples were subjected to HPP as described above. After HPP, LDH was diluted to 0.28 microg/ml in 100 mM phosphate buffer (pH 7.4). LDH activity was assessed by measuring the change in concentration of beta-NADH as a function of time. Dynamic light scattering analysis (DLS) was performed to examine the size distribution, polydispersity, and hydrodynamic radius of LDH before and after HPP. No significant difference in CFU/g was observed between lyophilized cells not subjected to HPP and lyophilized cells subjected to 600 MPa for 300 s (P<0.05). However, lyophilized cells that were suspended in 100% to 60% peptone water showed a approximately 7.5-log(10) reduction when subjected to HPP. Survival of L. monocytogenes following HPP significantly increased (P<0.05) when the peptone water concentration was decreased below 60% (aw approximately 0.8). DLS results revealed that LDH suspended in buffer underwent aggregation following HPP (600 MPa, 300 s). Inactivation rate constants obtained using a first-order kinetic model indicated that untreated and HP processed lyophilized LDH had similar activities. When LDH was subject to HPP in solutions containing glycerol, enzyme activity decreased as the water content increased (r2=0.95). Lyophilization completely protected L. monocytogenes and LDH from inactivation by high pressure. Furthermore, enzyme activity and cell survival increased as water activity was decreased. We postulate low aw results in protein stabilization, which prevents protein denaturation and cell death during HPP.

Links

Publisher Full Text (DOI)

Authors+Show Affiliations

Hayman MM
Department of Food Science, The Pennsylvania State University, 202 Food Science Building, University Park, PA 16802, USA. Melinda.Hayman@gmail.com <Melinda.Hayman@gmail.com>
Kouassi GK
No affiliation info available
Anantheswaran RC
No affiliation info available
Floros JD
No affiliation info available
Knabel SJ
No affiliation info available

MeSH

Colony Count, MicrobialConsumer Product SafetyFood HandlingFood MicrobiologyFood PreservationFreeze DryingGlycerolHumansHydrostatic PressureKineticsL-Lactate DehydrogenaseListeria monocytogenesTemperatureTime FactorsWater

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

18403036

Citation

Hayman, Melinda M., et al. "Effect of Water Activity On Inactivation of Listeria Monocytogenes and Lactate Dehydrogenase During High Pressure Processing." International Journal of Food Microbiology, vol. 124, no. 1, 2008, pp. 21-6.
Hayman MM, Kouassi GK, Anantheswaran RC, et al. Effect of water activity on inactivation of Listeria monocytogenes and lactate dehydrogenase during high pressure processing. Int J Food Microbiol. 2008;124(1):21-6.
Hayman, M. M., Kouassi, G. K., Anantheswaran, R. C., Floros, J. D., & Knabel, S. J. (2008). Effect of water activity on inactivation of Listeria monocytogenes and lactate dehydrogenase during high pressure processing. International Journal of Food Microbiology, 124(1), 21-6. https://doi.org/10.1016/j.ijfoodmicro.2008.02.026
Hayman MM, et al. Effect of Water Activity On Inactivation of Listeria Monocytogenes and Lactate Dehydrogenase During High Pressure Processing. Int J Food Microbiol. 2008 May 10;124(1):21-6. PubMed PMID: 18403036.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of water activity on inactivation of Listeria monocytogenes and lactate dehydrogenase during high pressure processing. AU - Hayman,Melinda M, AU - Kouassi,Gilles K, AU - Anantheswaran,Ramaswamy C, AU - Floros,John D, AU - Knabel,Stephen J, Y1 - 2008/03/04/ PY - 2007/06/05/received PY - 2008/01/17/revised PY - 2008/02/14/accepted PY - 2008/4/12/pubmed PY - 2008/8/5/medline PY - 2008/4/12/entrez SP - 21 EP - 6 JF - International journal of food microbiology JO - Int J Food Microbiol VL - 124 IS - 1 N2 - The aim of this study was to investigate the effect of water activity (aw) on the inactivation of Listeria monocytogenes and lactate dehydrogenase (LDH) during high pressure processing (HPP). For microbial inactivation lyophilized cells of L. monocytogenes 19,115 were left dry or were suspended in 10 ml of 0.1% peptone water, 10 ml of glycerol, or mixtures of glycerol and peptone water. All samples of various aws were high pressure (HP) processed at ambient temperature at 600 MPa for 300 s. Following HPP, samples were serially diluted in 0.1% peptone and spread-plated on Tryptic Soy agar supplemented with Yeast Extract. For enzyme inactivation, 4.2 mg of lyophilized LDH was suspended in 2 ml of 100 mM phosphate buffer (pH 7.4), 2 ml of peptone water or glycerol, or in 2 ml mixtures of glycerol and peptone water. A lyophilized sample with no added liquid was also included. All enzyme samples were subjected to HPP as described above. After HPP, LDH was diluted to 0.28 microg/ml in 100 mM phosphate buffer (pH 7.4). LDH activity was assessed by measuring the change in concentration of beta-NADH as a function of time. Dynamic light scattering analysis (DLS) was performed to examine the size distribution, polydispersity, and hydrodynamic radius of LDH before and after HPP. No significant difference in CFU/g was observed between lyophilized cells not subjected to HPP and lyophilized cells subjected to 600 MPa for 300 s (P<0.05). However, lyophilized cells that were suspended in 100% to 60% peptone water showed a approximately 7.5-log(10) reduction when subjected to HPP. Survival of L. monocytogenes following HPP significantly increased (P<0.05) when the peptone water concentration was decreased below 60% (aw approximately 0.8). DLS results revealed that LDH suspended in buffer underwent aggregation following HPP (600 MPa, 300 s). Inactivation rate constants obtained using a first-order kinetic model indicated that untreated and HP processed lyophilized LDH had similar activities. When LDH was subject to HPP in solutions containing glycerol, enzyme activity decreased as the water content increased (r2=0.95). Lyophilization completely protected L. monocytogenes and LDH from inactivation by high pressure. Furthermore, enzyme activity and cell survival increased as water activity was decreased. We postulate low aw results in protein stabilization, which prevents protein denaturation and cell death during HPP. SN - 0168-1605 UR - https://www.unboundmedicine.com/medline/citation/18403036/Effect_of_water_activity_on_inactivation_of_Listeria_monocytogenes_and_lactate_dehydrogenase_during_high_pressure_processing_ DB - PRIME DP - Unbound Medicine ER -