No need to cry over spoiled milk… pasteurisation-resistant bacteria identified

By Mark Astley

- Last updated on GMT

US researchers identify heat treatment-resistant bacteria in milk

Related tags: Milk, Bacteria

US researchers have identified a heat treatment-resistant spoilage-causing microbe in fluid milk - knowledge they hope can be used to extend the shelf life of dairy products.

Spore-forming bacteria, Paenibacillus, was identified by researchers from the Milk Quality Improvement Program at Cornell University’s College of Agriculture and Life Sciences.

High temperature, short time (HTST) milk pasteurisation kills off the majority of spoilage-causing microbes. However certain bacterial strains, such as Paenibacillus, can survive the heat treatment process as spores and cause milk to spoil during storage.

The Cornell University researchers documented their findings in the report, Identification and Characteristic of Psychrotolerant Sporeformers Associated with Fluid Milk Production and Processing.

Report co-author Martin Wiedmann told DairyReporter.com that the discovery could help processors make high temperature, short time (HTST) pasteurised milk with an extended shelf life.

Extended shelf life

“We have characterised a large set of spore-forming bacteria isolated from pasteurised milk and other dairy associated sources; we have found that a specific group of these bacteria, called Paenibacillus, largely contains organisms that can grow at low temperatures,” ​said Wiedmann.

“These bacteria can form spores, which are extremely heat resistant.”

“This research should help some processors make HTST milk that has shelf life >17 to 19 days,” ​he said.

Wiedmann confirmed that the teams’ discovery could lead to some sort of commercial development to prevent the survival of the bacteria.

“This research does indeed identify the specific organisms that would need to be targeted by any type of interventions, whether additives, novel processing technologies, or methods to prevent contamination to begin with. Along these lines we have recently developed a molecular biology (PCR-based) test to specifically detect these organisms,” ​Wiedmann added.

Improve milk quality

Wiedmann also confirmed that the Wiedmann-Boor lab, which published the report, has been enlisted by New York State-based cooperative, Upstate Niagara, to help improve the quality of its milk by assessing milk samples for the spore-forming Paenibacillus.

“We are working with dairy processors in New York to apply these findings and to further extend shelf life of HTST fluid milk; we are always happy to work with additional partners though to assure our research findings are rapidly used by industry,” ​Wiedmann added.

Report co-author Nicole Martin added, however, that there is much more to learn about the organism.

“I would simply add that we are currently working to further characterise these organisms for additional phenotypic characteristics that are important for milk spoilage,” ​said Martin. “We have learned that many of these organisms produce enzymes that degrade various components of the milk in addition to lactose, including proteins and lipids.”

Related topics: Regulation & Safety, Fresh Milk

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