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Influence of storage conditions on the growth of Pseudomonas species in refrigerated raw milk

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Abstract
The refrigerated storage of raw milk throughout the dairy chain prior to heat treatment creates selective conditions for growth of psychrotolerant bacteria. These bacteria, mainly belonging to the genus Pseudomonas, are capable of producing thermoresistant extracellular proteases and lipases, which can cause spoilage and structural defects in pasteurized and ultra-high-temperature-treated milk (products). To map the influence of refrigerated storage on the growth of these pseudomonads, milk samples were taken after the first milking turn and incubated laboratory scale at temperatures simulating optimal and suboptimal preprocessing storage conditions. The outgrowth of Pseudomonas members was monitored over time by means of cultivation-independent denaturing gradient gel electrophoresis (DGGE). Isolates were identified by a polyphasic approach. These incubations revealed that outgrowth of Pseudomonas members occurred from the beginning of the dairy chain (farm tank) under both optimal and suboptimal storage conditions. An even greater risk for outgrowth, as indicated by a vast increase of about 2 log CFU per ml raw milk, existed downstream in the chain, especially when raw milk was stored under suboptimal conditions. This difference in Pseudomonas outgrowth between optimal and suboptimal storage was already statistically significant within the farm tank. The predominant taxa were identified as Pseudomonas gessardii, Pseudomonas gessardii-like, Pseudomonas fluorescens-like, Pseudomonas lundensis, Pseudomonas fragi, and Pseudomonas fragi-like. Those taxa show an important spoilage potential as determined on elective media for proteolysis and lipolysis.
Keywords
PROTEASES, MURAL PAINTINGS, DIVERSITY, FLUORESCENS, SPOILAGE, PHENOTYPIC CHARACTERIZATION, PSYCHROTROPHIC BACTERIA, GENUS PSEUDOMONAS, GRADIENT GEL-ELECTROPHORESIS, DAIRY-PRODUCTS

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Chicago
De Jonghe, Valerie, An Coorevits, Koenraad Van Hoorde, Winy Messens, Anita Van Landschoot, Paul De Vos, and Marc Heyndrickx. 2011. “Influence of Storage Conditions on the Growth of Pseudomonas Species in Refrigerated Raw Milk.” Applied and Environmental Microbiology 77 (2): 460–470.
APA
De Jonghe, V., Coorevits, A., Van Hoorde, K., Messens, W., Van Landschoot, A., De Vos, P., & Heyndrickx, M. (2011). Influence of storage conditions on the growth of Pseudomonas species in refrigerated raw milk. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 77(2), 460–470.
Vancouver
1.
De Jonghe V, Coorevits A, Van Hoorde K, Messens W, Van Landschoot A, De Vos P, et al. Influence of storage conditions on the growth of Pseudomonas species in refrigerated raw milk. APPLIED AND ENVIRONMENTAL MICROBIOLOGY. 2011;77(2):460–70.
MLA
De Jonghe, Valerie, An Coorevits, Koenraad Van Hoorde, et al. “Influence of Storage Conditions on the Growth of Pseudomonas Species in Refrigerated Raw Milk.” APPLIED AND ENVIRONMENTAL MICROBIOLOGY 77.2 (2011): 460–470. Print.
@article{1919892,
  abstract     = {The refrigerated storage of raw milk throughout the dairy chain prior to heat treatment creates selective conditions for growth of psychrotolerant bacteria. These bacteria, mainly belonging to the genus Pseudomonas, are capable of producing thermoresistant extracellular proteases and lipases, which can cause spoilage and structural defects in pasteurized and ultra-high-temperature-treated milk (products). To map the influence of refrigerated storage on the growth of these pseudomonads, milk samples were taken after the first milking turn and incubated laboratory scale at temperatures simulating optimal and suboptimal preprocessing storage conditions. The outgrowth of Pseudomonas members was monitored over time by means of cultivation-independent denaturing gradient gel electrophoresis (DGGE). Isolates were identified by a polyphasic approach. These incubations revealed that outgrowth of Pseudomonas members occurred from the beginning of the dairy chain (farm tank) under both optimal and suboptimal storage conditions. An even greater risk for outgrowth, as indicated by a vast increase of about 2 log CFU per ml raw milk, existed downstream in the chain, especially when raw milk was stored under suboptimal conditions. This difference in Pseudomonas outgrowth between optimal and suboptimal storage was already statistically significant within the farm tank. The predominant taxa were identified as Pseudomonas gessardii, Pseudomonas gessardii-like, Pseudomonas fluorescens-like, Pseudomonas lundensis, Pseudomonas fragi, and Pseudomonas fragi-like. Those taxa show an important spoilage potential as determined on elective media for proteolysis and lipolysis.},
  author       = {De Jonghe, Valerie and Coorevits, An and Van Hoorde, Koenraad and Messens, Winy and Van Landschoot, Anita and De Vos, Paul and Heyndrickx, Marc},
  issn         = {0099-2240},
  journal      = {APPLIED AND ENVIRONMENTAL MICROBIOLOGY},
  language     = {eng},
  number       = {2},
  pages        = {460--470},
  title        = {Influence of storage conditions on the growth of Pseudomonas species in refrigerated raw milk},
  url          = {http://dx.doi.org/10.1128/AEM.00521-10},
  volume       = {77},
  year         = {2011},
}

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