Microbial food safety along the dairy chain View all 13 Articles. Raw bovine milk is highly nutritious as well as pH-neutral, providing the ideal conditions for microbial growth. The microbiota of raw milk is diverse and originates from several sources of contamination including the external udder surface, milking equipment, air, water, feed, grass, feces, and soil. Many bacterial and fungal species can be found in raw milk. The autochthonous microbiota of raw milk immediately after milking generally comprises lactic acid bacteria such as Lactococcus , Lactobacillus , Streptococcus , and Leuconostoc species, which are technologically important for the dairy industry, although they do occasionally cause spoilage of dairy products.
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Pereira a , L. Luiz a , S. Bruzaroski a , R. Poli-Frederico b , R. Fagnani a and E. The interaction among lipolysis, temperature, and ST occurs even with a low population of P. The ST, temperature, and population of P.
The effect of cold storage, time and the population of Pseudomonas species on milk lipolysis. Grasas y Aceites 70 2 , e This is an open-access article distributed under the terms of the Creative Commons Attribution 4.
The preservation of raw milk by cold storage without adequate sanitary-hygienic measures can allow the growth of psychrotrophic micro-organisms, the major deteriorating agents in fluid milk and dairy products Sorhaung and Stepaniak, Pseudomonas is considered the psychrotrophic predominant genus Fagundes et al.
Therefore, they naturally become the predominant microbiota in milk stored in this temperature range Dogan and Boor, Lipase is a glycoprotein that can hydrolyze long and short chain triglycerides, esters, monoglycerides and phospholipids, releasing fatty acids and glycerol molecules. The breakdown of fat globules leads to an increase in the fraction of short-chain fatty acids C-4 to C-8 , giving a rancid taste and odor to dairy products.
The soapy taste and odor are produced by the hydrolysis of fatty acids with higher molecular weight C to C , whereas the metallic or oxidized taste is the result of the oxidation of unsaturated fatty acids to ketones and aldehydes Chen et al. According to Deeth and Fitz-Gerald , although milk lipolytic degradation and it effects were not as intense as the proteolytic degradation, defects such as rancid, soapy, or bitter taste, as a result of lipase activity, are the first off-flavor changes that were detectable.
Therefore, the aim of this study was to evaluate the effect of cold storage, time and the Pseudomonas fluorescens and Pseudomonas putida populations on the lipolytic index of milk. The Pseudomonas spp. The milk samples were stored in cooling tanks, collected under aseptic conditions, and were kept in a Styrofoam box with reusable ice packs, until analysis.
For Pseudomonas spp. The reagents and materials used in this study are described below. The extracted genetic material was subjected to PCR for the identification of the gender Pseudomonas spp. For the identification of the species P. For the identification of P.
Ultrapure water was used as the negative control and DNA from the strains P. All the PCR products were subjected to agarose gel 1. From eight and six strains confirmed to be P. After reaching the required bacterial cell count, decimal dilutions were made in 0. Each selected dilution was immediately used to set up cultures. In an initial extraction step, milk 4mL was added to 16 mL of Lipo R reagent mL of isopropanol, The tubes were shaken by inversion 15 times, followed by resting for 5 min and the supernatant supernatant-1 was obtained.
Then the rinsing process was carried out by transferring 8 mL of the supernatant-1 to test tubes, followed by the addition of 4 mL of rinsing solution sulfuric acid at 0. After resting for 5 min, the supernatant-2 was obtained. Finally, 4 mL of the supernatant-2 were mixed with 5 drops of thymol blue indicator 1 g of thymol blue in 1. Two independent experiments were carried out with each of the strains. The influence of storage time, temperature, and Pseudomonas spp. A total of 72 experimental runs were conducted, since plating was performed in duplicate.
The response data was plotted as a response surface to obtain a better understanding of the underlying mechanism behind the lipolytic ability of Pseudomonas. The data were analyzed using the software Statistica, release We also accounted for the existing differences in the lipolytic index between the strains of P.
Enzyme production by Pseudomonas spp. The lipolysis over storage time and incubation temperature occurred even with a low population of P. However, due to the marginally significant effect of the P. Despite the fact that storage time, temperature and P. Figure 1. With regards to P. Consequently, the higher the storage time, temperature, and P. The storage time was the strongest factor influencing the lipolysis, followed by temperature and finally, by population size.
In the study on the isolation of psychrotrophic micro-organisms from refrigerated raw milk, it was observed that all the P. Figure 2. Research performed in the past to observe the genetic diversity and the production of extracellular enzymes protease, lipase, and lecithinase by Pseudomonas spp. Kumaresan et al. In our study, if we consider the sensory threshold of 0. Lower temperature and storage time are important factors that can reduce lipid lysis in milk caused by P.
Good cow milking to control P. Materials, reagents, and milk samples 2. Pseudomonas spp. PCR 2. Determination of P. Inoculation with Pseudomonas and measurement of the lipolytic index 2. Statistical analysis 3. Counting, isolation and characterization of psychrotrophic bacteria from refrigerated raw milk.
Detection and impact of protease and lipase activities in milk and milk powders. Dairy J. Lipolytic enzymes and hydrolytic rancidity, in Fox P F. Advanced dairy chemistry: lipids. Dogan B, Boor KJ. Genetic diversity and spoilage potentials among Pseudomonas spp. Growth of Pseudomonas putida at low temperature: global transcriptomic and proteomic analyses. Tests for groups of microorganisms, in Marshall RT Ed Standard methods for the examination of dairy products.
Psychrotrophic spoilage of raw milk at different temperatures of storage. Mahieu H. Purification and properties of a heat-stable enzyme of Pseudomonas fluorescens Rm12 from raw milk. Food Res. Biodiversity of refrigerated raw milk microbiota and their enzymatic spoilage potential.
Food Microbiol. Development of PCR assay to identify Pseudomonas fluorescens and its biotype. FEMS Microb. PCR-Based assay for differentiation of Pseudomonas aeruginosa from other Pseudomonas species recovered from cystic fibrosis patients.
Sorhaung T, Stepaniak L. Psychrotrophs and their enzymes in milk and dairy products: quality aspects. Trends Food Sci. Influence of feed composition on stability of fat globules during pumping of raw milk. Yamamoto S, Harayama S. PCR amplification and direct sequencing of gyrB genes with universal primers and their application to the detection and taxonomic analysis of Pseudomonas putida strains.
Lipolytic capacity of Pseudomonas spp. isolated from refrigerated raw milk
The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of psychrotrophic bacteria and the thermo-stabilities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. Species of Yersinia , Pseudomonas , Serratia , and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens d. Lipolytic activity was high in isolates of Acinetobacter , and the highest in Acinetobacter guillouiae.
Milk spoilage is caused by the presence of proteolytic enzymes produced by Pseudomonas spp. The aim of this study was to identify Pseudomonas spp. Pseudomonas spp. The proteolytic properties of Pseudomonas spp.
Proteolytic and lipolytic potential of Pseudomonas spp. Pedro I. Oliveira 3. Edson A. Rios 2. Pseudomonas, the main genus of gram-negative microorganisms isolated from milk, is psychrotrophic, biofilm-forming, and thermo-resistant deteriorating enzyme producers. The aim of this study was to quantify Pseudomonas spp.
Lipases triacylglycerol acylhydrolases, EC 3. Lipases occur widely in nature, but only microbial lipases are commercially significant. In the present study, production of extracellular lipase in submerged fermentation of Pseudomonas sp. Lp1 isolated from oil contaminated soil has been investigated.