By Kate Sander

SYRACUSE, N.Y. — Spoilage organisms can wreak havoc on dairy products, at best shortening product shelf-life and at worst causing illness for consumers. It's an expensive problem, and common enough that Dairy Management Inc. and USDA have provided funding for Dr. Kathryn Boor, associate professor of food science, Cornell University, and her colleague Dr. Martin Wiedmann, to track and identify spoilage organisms.

Boor, who will present the research to dairy industry executives this coming week at the "Cornell Conference on Dairy Markets and Product Research," in Syracuse, N.Y., says identifying the genetic fingerprints of spoilage organisms allows determination of bacteria beyond the species and subspecies level — information that can be used for tracking contamination sources and outbreaks and ultimately eliminating the problem. The data also can be used to determine whether the bacteria are capable of causing specific defects in the milk such as destruction of fat, protein or flavor.

The research has focused on two areas: developing and applying fingerprinting methods for Pseudomonas spp. (typical Gram negative spoilers) and Listeria monocytogenes. Pseudomonas is a common cause of spoilage in fluid milk and L. monocytogenes can pose serious health problems for consumers.

The researchers have used automated ribotyping which provides a rapid, sensitive and reliable means for typing, classification and speciation of bacteria, Boor says. For Pseudomonas, the researchers have developed a database based on automated ribotyping of the bacteria using 300 Pseudomonas spp. isolates from milk and dairy products. For L. monocytogenes, a database has been developed using a collection of more than 2,000 human, animal and food isolates based on a collaborative effort between the university, the New York State Veterinary Diagnostic Laboratory, the New York State Department of Health, the New York State Department of Agriculture and Markets, the New York City Department of Health and other state health departments over the course of the past several years.

What has resulted is a significant amount of valuable data that Boor says can be utilized to clean up contamination in a plant.

For example, a milk processing plant might find that suddenly its pasteurized gallons of milk have a shelf-life that has diminished from 21 days to less than 10. Using the latest ribotyping technology and comparing it to the data already gathered, the plant could collect and identify predominant spoilage microflora in the processed products as well in the plant environment and raw milk supply. Armed with the specific "fingerprint" information, the company could then work backwards from the end product to determine when and where the contamination is occurring. Specifically, with information about the organism below the subspecies level, it can be determined whether there is more than one source of bacteria, Boor explains.

And once it is determined what the source or sources of initial contamination are, they can then be eliminated. In addition, with the information at hand, researchers also are learning which organisms are likely to cause consumer complaints, Boor says.

However, even though the data is available, it's fairly expensive and high-tech to do such research to determine what is causing spoilage problems. Still, that doesn't mean dairy executives should rule out using the information.

Boor likens it to the early calculators of just 30 years ago that were expensive, large and only performed certain basic functions. Today, credit card-sized calculators are given away as promotional tools and calculators with complex functions don't cost very much. Boor expects a similar thing to happen with the tracking and identification of spoilage organisms; the more that becomes known about them and the more the fingerprinting techniques develop, the more useful, cost-effective and common the technology will be. Collecting the data on Pseudomonas and L. monocytogenes is just the first step in the process of making this type of information available and useful to the industry, Boor says.

"These data are clearly powerful, but they are most valuable when they're instantly available to those who need to make 'bottom line' decisions regarding product quality and safety," she adds.

With that in mind, a "Pathogen Tracker" database, scheduled for public release by June 2002, is being developed to allow data exchange, data mining and access to third parties.

The database will include such information as isolate source (human, food, animal, environment), year and month of isolation, location (county or state) and DNA fingerprints.

CMN