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Psychrotrophic organism is a putrefactive type

Technical information Food refrigeration and freezing Micro-organisms associated with dairy products

Micro-organisms associated with dairy products

The main micro-organisms of concern in dairy products such as milk and cheese putrefactive bacteria and pathogenic bacteria. They arise from contamination of raw materials in the process of milking of animals (e.g. Flora of the udder or in the faeces), from contaminated equipment/handlers and milking environment (e.g. spore-forming bacteria). Milk from cows suffering mastitis or other diseases that may contain bacteria, which are usually not found in milk from healthy animals, including S. aureus, pyrogenic streptococci and actinomycetes, Brucella spp., mycobacteria, Salmonella, L. monocytogenes, Coxiella burnetii, and some viruses, including foot-and-mouth disease virus (FMDV). Most milk is pasteurized following transport/short-term storage at temperatures/times (e.g. 72C for 15 s)that inactivate the plant's cells, including infectious bacterial pathogens commonly associated with milk, such as Salmonella bacteria, L. monocytogenes, pathogenic Escherichia coli, campy-lobacters and Yersinia enterocolitica.

The same type of inactivation is stored at low temperatures for a long period of time (e.g.

68C for 30 minutes), while the ultra-high temperature (UHT) treatment as a rule, are used at temperatures up to 149C for 2 seconds and it will deactivate mesophilic spore-forming bacteria, allowing such milk stored at room temperature for a long time. Lowering the temperature/time combinations, for example, 138C for 10 seconds, is used to increase a period of storage (called ESL) milk stored in the cold for a long (more than 4 weeks. In these products, psychrotrophic spore-forming microorganisms but are inactivated products are not commercially sterile. Some of the milk passes micro-filtration, as an alternative to the pasteurization to remove infectious agents. Some raw milk may contain mycotoxins and is considered as a result animals ingress of contaminated feed.

Spoilage microorganisms associated with milk include psychrotrophic bacteria such as Pseudomonas, Flavobacterium spp., Chromobacterium spp., Alcaligenes spp. and thermo-mophilic spore-forming bacteria that survive pasteurization. Other ingredients used in frozen desserts include butter, sugar, chocolate, fruits, nuts and eggs. These are often added after pasteurized milk and ensure their safety, normally provided by the suppliers of these materials, some of which (e.g. eggs, chocolate) were known to have associated with pathogens such as Salmonella or their toxins, such as S. aureus enterotoxin. Some microbiological contaminants, such as Listeria monocytogenes, associated with wet equipment and production, as it faces in the production of ice cream. Environmental monitoring and effective cleaning and disinfection critical for the safety of these products, in particular, when considering post-processing, for example. frozen in shock freezing and hardening tunnels.

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