Research Can Lead To Longer Shelf Life For Dairy Products

Lin's doctoral thesis involved research on "finding the mechanism of how the additives – including gums and phosphate salts – and homogenization pressure affect the quality of a type of dairy-based beverage during extended storage," he said.

In this research, Lin said, canned milk-based diet beverages and milk-based sports drinks that must have a long shelf life were tested 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," he said.

Eventually his research focused on a process called high pressure homogenization. This process was found extend shelf life of these beverages, while at the same time maintaining their quality and nutrient value.

Homogenization, 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 process results in fat globules that remain disbursed throughout the product, rather than separating and rising to the top the way cream does in non-homogenized milk, Lin said. However, in ordinary homogenization, these fat globules are not all the same size.

Lin decided to see what would happen if much more pressure was applied during the homogenization 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.

Lin's research could eventually impact the way many dairy products – including yogurt, skim 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 longer, this process could also help cut down waste on the consumer level. And for many products, "you won't have to shake before you use," he added with a smile.

However, the researchers added, 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.

His research will have no effect on whether or not a product should be refrigerated – just on how long it can be used. "It's a method of processing, not storage," Lin said.

The research using high pressure homogenization 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."