Food and Fermentation Industries >

2026 , Vol. 52 >Issue 17: 61 - 73

DOI: https://doi.org/10.13995/j.cnki.11-1802/ts.046854

Proteolytic properties of Pseudomonas isolated from raw milk and consistency of their phenotypic distribution with three typing methods:A comparative study

  • ZHAN Cuiqing ,
  • QI Yan ,
  • YOU Chunping
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  • 1(College of Food Science and Technology, Shanghai Ocean University, Shanghai 201306, China)
    2(State Key Laboratory of Dairy Biotechnology, Key Laboratory of Functional Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Shanghai Engineering Research Center of Dairy Biotechnology,Dairy Research Institute, Bright Dairy & Food Co.Ltd., Shanghai 201103, China)

Received date: 2026-04-08

  Revised date: 2026-04-23

  Online published: 2026-09-21

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Abstract

Raw milk is prone to quality deterioration during cold storage due to the proteolytic activity of psychrotrophic spoilage bacteria, particularly those belonging to the genus Pseudomonas.This study was conducted to clarify the proteolytic phenotypic characteristics of raw milk-derived Pseudomonas and to evaluate the applicability of different molecular typing methods in the consistency analysis of their spoilage phenotype clustering.A total of 31 Pseudomonas strains (including 26 isolates from raw milk in Shanghai and 5 type strains) were used as research subjects, and molecular typing was performed based on 16S rRNA gene sequences, ribotyping fingerprints, and a combination of housekeeping genes and protease genes using multi-locus sequence typing-like typing (MLST-like), respectively, to systematically compare the consistency of each typing result with the distribution of proteolytic phenotypes.The results showed that 67.7% of the strains produced clear zones on skim milk agar plates, and the average protease activity of the proteolytic-positive strains was 0.56 ΔA·h-1·mL-1.In species-level identification, ribotyping exhibited higher discriminatory power than 16S rRNA gene sequencing, with 48.4% of the strains identified as Pseudomonas fluorescens.The proteolytic capacity of the P. fluorescens group was significantly higher than that of the non-P. fluorescens group (P<0.000 1).Regarding consistency with the distribution of proteolytic spoilage phenotypes, the clustering results of 16S rRNA gene sequence analysis and ribotyping showed similar overall trends in the distribution of proteolytic phenotypes, while MLST-like typing exhibited the clearest correspondence with proteolytic capacity and the risk classification of proteolytic spoilage.This study revealed the distribution characteristics of proteolytic phenotypes of Pseudomonas in raw milk and evaluated the applicability of the three typing methods for identifying spoilage risk.These findings provided a reference for the identification and graded control of spoilage risk posed by Pseudomonas in raw milk.

Key words： raw milk; Pseudomonas; protease; 16S rRNA gene sequence analysis; ribotyping; multi-locus sequence typing-like typing

Cite this article

ZHAN Cuiqing , QI Yan , YOU Chunping . Proteolytic properties of Pseudomonas isolated from raw milk and consistency of their phenotypic distribution with three typing methods:A comparative study[J]. Food and Fermentation Industries, 2026 , 52(17) : 61 -73 . DOI: 10.13995/j.cnki.11-1802/ts.046854

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