Skip to Content
Merck
  • Pseudomonas spp. and Serratia liquefaciens as Predominant Spoilers in Cold Raw Milk.

Pseudomonas spp. and Serratia liquefaciens as Predominant Spoilers in Cold Raw Milk.

Journal of food science (2015-07-21)
Solimar G Machado, Fernanda L da Silva, Denise M S Bazzolli, Marc Heyndrickx, Paulo M de A Costa, Maria Cristina D Vanetti
ABSTRACT

The storage of fresh raw milk at low temperature does not prevent proliferation of psychrotrophic bacteria that can produce heat-resistant proteolytic enzymes contributing to the reduced shelf life of dairy products. This study aimed to identify the dominant psychrotrophic proteolytic enzyme-producing population of raw milk from Brazil. Raw milk samples collected in 3 different cooling tanks in Brazil were stored at optimal (45 h at 4 °C followed by 3 h at 7 °C) and suboptimal (45 h at 7 °C followed by 3 h at 10 °C) conditions to simulate farm storage and transportation allowed by Brazilian laws. The highly proteolytic enzyme-producing strains isolated from stored cold raw milk were characterized by repetitive sequence-based Polymerase Chain Reaction (PCR) analysis. This clustering resulted in 8 different clusters and 4 solitary fingerprints. The most proteolytic isolates from each rep-cluster were selected for identification using miniaturized kit, 16S rDNA and rpoB gene sequencing. Serratia liquefaciens (73.9%) and Pseudomonas spp. (26.1%) were identified as the dominant psychrotrophic microorganisms with high spoilage potential. The knowledge of milk spoilage microbiota will contribute to improved quality of milk and dairy products.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Magnesium chloride solution, 0.1 M
Sigma-Aldrich
Magnesium chloride solution, BioUltra, for molecular biology, 2 M in H2O
Sigma-Aldrich
Magnesium chloride solution, PCR Reagent, 25 mM MgCI2 solution for PCR
Sigma-Aldrich
Magnesium chloride solution, for molecular biology, 1.00 M±0.01 M
Sigma-Aldrich
Magnesium chloride solution, BioUltra, for molecular biology, ~0.025 M in H2O
Sigma-Aldrich
Bromothymol Blue, ACS reagent, Dye content 95 %
Sigma-Aldrich
Magnesium chloride solution, BioUltra, for molecular biology, ~1 M in H2O
Sigma-Aldrich
Potassium sulfate, 99.99% trace metals basis
Sigma-Aldrich
Magnesium chloride, powder, <200 μm
Sigma-Aldrich
Potassium sulfate, BioUltra, ≥99.0% (AT)
Sigma-Aldrich
Magnesium chloride, AnhydroBeads, −10 mesh, 99.9% trace metals basis
Sigma-Aldrich
Magnesium chloride, AnhydroBeads, −10 mesh, 99.99% trace metals basis
Sigma-Aldrich
Magnesium chloride, BioReagent, suitable for insect cell culture, ≥97.0%
Sigma-Aldrich
Magnesium chloride, anhydrous, ≥98%
Sigma-Aldrich
Potassium sulfate, suitable for plant cell culture
Sigma-Aldrich
Potassium sulfate, BioXtra, ≥99.0%
Sigma-Aldrich
Fusidic acid sodium salt, ≥98% (TLC)
SAFC
Potassium sulfate