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Extending dairy shelf life

19-Dec-2002

Research carried out at the Texas A&M university could improve dairy industry consumer products of tomorrow, claim scientists this week.

For a doctoral thesis, Alexander Lin set out to "find the mechanism of how the additives - including gums and phosphate salts - and homogenisation pressure affect the quality of a type of dairy-based beverage during extended storage," he said.

Lin tested canned milk-based diet beverages and milk-based sports drinks that had a long shelf life to find how quality and length of storage could be improved.

"We tried different ingredients to see how they affected quality - how different ingredients have different affects on quality. We also checked different processes," Lin added.

Lin's research focused on a process called high pressure homogenisation. This process was found to extend shelf life of these beverages, while at the same time maintaining their quality and nutrient value.

Homogenisation, a process that has been in use in the dairy industry for more than a century, involves subjecting dairy products to 2,000 to 3,000 pounds per square inch of pressure.

This results in fat globules that remain dispersed throughout the product, rather than separating and rising to the top. In ordinary homogenisation, these fat globules are not all the same size.

Lin chose to investigate what would happen if the pressure was increased during the homogenisation process. "The pressure we tested went up to 14,000 psi," he said.

The result was smaller, more uniformly-sized fat globules and a more stable product with a longer shelf life, said Lin.

The scientist claims this research could eventually have an impact on the way many dairy products - including yoghurt, skimmed and whole milk, cheddar cheese and whey proteins - are processed.

If that happens, consumers will benefit, said Dr Ronald Richter, professor in food science and committee chair for Lin's research, because "improving the processing will cause improvements in the physical properties and longer shelf life".

By keeping products useable for longer, this process could also help reduce waste at the consumer level.

The researchers warned that this process will increase shelf life before the product is opened, not after. "Once it's open, microbiological contamination by the consumer is the primary factor affecting shelf life," Lin said. "It's a method of processing, not storage."

The research using high pressure homogenisation will probably continue, even after Lin receives his doctorate degree in December, Richter said. "The research will be extended beyond beverages and how they can be controlled. We might even want to cause things to gel, like pudding. (If we can) control the functionality with this process - what you put on the surface of things affects how it will behave in different environments."

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