Food Microbiology Marches On

In the earliest annals of food safety, it is unclear to what degree scientists knew the microbiology behind their processes. Louis Pasteur was an early leader in understanding the persistence of microbes. “Pasteur said that if you have a sterile environment and don’t touch it, you still can get microbes in it, so there must be a way to get in,” said Bob Young, MS, senior technical specialist at 3M in St. Paul, Minn. The company introduced its Petrifilm Plates about 25 years ago as an alternative to the agar Petri dish. Most are used daily on the product line.

J. Stan Bailey, PhD, director of scientific affairs at bioMerieux in Athens, Ga., added that the basics of food preservation have remained the same since the time of Pasteur. “Bacteria is a living thing needing nutrients, moisture, and the proper heat,” said Dr. Bailey, who has, in the past, worked with the U.S. Department of Agriculture (USDA). “Food preservation comes down to controlling those factors. No matter how sophisticated we get, it gets back to those factors that allow those organisms to grow.”

The FDA’s Dr. Zink said food microbiology took off as a science after World War II. “More food was available after the war, and there was a boon for food and scientists. One key driver was the spoilage of food,” he said. Extending the shelf life of milk is one example.

Dr. Zink said that in the 1940s, scientists at Iowa State University, notably bacteriologist Frank Eugene Nelson, PhD, were among the pioneers researching microorganisms in food and developing methods for testing it. Till then, most of the methods used in the food industry were long-time tests for water contaminants such as fecal coliforms. “He is a key person,” said Dr. Zink of Dr. Nelson’s role in the field of food microbiology and in teaching Dr. Zink and others. “He’s like my academic grandfather.”

Old Methods Persist

Though rapid result methods—such as DuPont Qualicon’s BAX PCR—can detect Listeria in eight hours, cell cultures in the Petri dish remain the norm, accounting for 50% or more of current testing. That is primarily due to its low price. Rapid methods have “progressed more slowly than anyone expected,” Dr. Zink said. Sample-size preparations and amplification remain bottlenecks in terms of speed of results, because it is critical to get enough of the pathogens to detect and determine which organisms are dead or alive. “We have yet to get away from some type of amplification,” he added. It still takes 24 hours or more to grow high enough numbers of a bacterium to be able to test it.

Bon Vivant Soup Company went out of business after a 1971 case of botulism in its vichyssoise killed at least one person and made others ill.

“The bottom line is that there are still very basic tools to use for general testing,” said Philippe Gadal, PhD, CEO of AES Chemunex in Cranbury, N.J. He said he’s still amazed at the level and the type of testing that is or is not being done. “One yogurt company took a random sample and placed it in a hot area for a couple of days and looked at and smelled it,” he said. “This is inappropriate.” That company ended up having a major recall in 2008 and lost millions of dollars. AES Chemunex offers several testing systems, including BactiFlow and D-Count, designed for use in general foods, and Scan RDI, which is designed for use only in filterable products like water.