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From: Food Quality & Safety magazine, February/March 2010

Food Microbiology Marches On

From Napoleon's army to today's consumer, the focus is on food safety

by Lori Valigra

Editor’s Note: This article on the history and impact of advances in food microbiology is the first in a new series for Food Quality. In “FoodTech: Tools That Changed the Industry,” we look at various technologies and tools, such as microbiological testing, that have played a key role in and had an indelible impact on the food industry. In our next issue, we will explore the emergence and evolution of rapid food microbiology tools.

Napoleon wanted to conquer the world, but he knew, as his famous quote aptly states, “an army travels on its stomach.” To be sure his men had safe rations, he offered a 12,000-franc prize to anyone who could come up with a food preservation method. Nicolas Appert, the chef and distiller who ultimately claimed the prize, spent more than a decade discovering that boiled foods placed in airtight glass containers would not spoil. In 1810, Peter Durand, a British merchant who received a patent for the tin containers that were forerunners of the cans used today, further refined the concept.

Safe food meant strong troops and power to Napoleon. The message isn’t so different today for food companies, which have learned from the history of food microbiology. They realize their businesses could be toppled by a large recall or a reputation for tainted foods and that outbreaks can sicken or kill consumers. Millions of dollars are lost to product recalls as production halts, products sit on warehouse shelves and then are discarded, and the public hesitates to buy from that company again.

That’s why companies have embraced testing for pathogens, thus enabling the evolution of better food microbiology tools. Scientists have used Petri dishes to grow samples and analyze them, added immunoassays and polymerase chain reaction (PCR) tools in the 1990s, and are now pushing toward more rapid test results. Growing cultures—a pervasive part of testing even today—can take up to a week and remains a bottleneck. Government and industry groups have also pushed for regulations and good manufacturing practices to advance the field of food microbiology.

“They [companies] are driven by risk aversion—looking at their auditing practices and at what they need to do better,” said Donald Zink, PhD, senior science advisor for the U.S. Food and Drug Administration’s (FDA’s) Center for Food Safety and Applied Nutrition in College Park, Md.

“It’s not just about testing, but about managing your inventory and business,” said Purnendu Vasavada, PhD, a professor of food science at the University of Wisconsin in River Falls and a member of the Food Quality editorial advisory board. “The food industry has always been looking at contamination. This is their bread and butter,” he said.

Louis Pasteur was an early leader in understanding the persistence of microbes, and the basics of food preservation have remained the same since his time.
Louis Pasteur was an early leader in understanding the persistence of microbes, and the basics of food preservation have remained the same since his time.

Since 2005, total microbiology testing volume has increased from 629.9 million to 738.3 million tests, an increase of 17.8%, according to Tom Weschler, founder of Strategic Consulting Inc., Woodstock, Vt. Testing for food pathogens, which, at 25.6%, has grown faster than the total market for microbial tests, now comprises 138.1 million tests. The total market for food microbiological testing topped $2 billion in 2008.

“There is testing done all the way from the farm to the fork,” said Weschler. The majority takes place using samples taken at the food factory. Not as much is done at food retail and service. “Food companies want to sell safe products, but they also want to protect their brand name, which is most directly influenced by a recall,” he said.

High Stakes

But more than brand name is at stake, because lives are in the balance. 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. “We still have some of the cans in the agency museum, even the swollen ones,” said Dr. Zink, who formerly worked in industry for Nestle and Campbell Soup Co. And last year, Peanut Corporation of America went bankrupt after its widespread Salmonella outbreak was linked to at least nine deaths and 636 cases of food poisoning.

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.”

Bacteria is a living thing needing nutrients, moisture, and the proper heat. 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.

—J. Stan Bailey, PhD, bioMerieux

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.
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.

Attention to pathogens has paid off. Foodborne pathogens are responsible for some 76 million illnesses in the United States annually. But the incidence of E. coli O157:H7, one of the most severe foodborne diseases, declined 36% from 2002 to 2003, according to a report by the Centers for Disease Control and Prevention (CDC) and others. The overall incidence of E. coli O157:H7 has declined 42% since 1996. The data also showed that the incidence of three common foodborne diseases—Campylobacter, Salmonella, and Yersinia—continued to decline substantially over the previous eight years. The declines were attributed to enhanced surveillance and outbreak investigations to identify new control measures. More attention was also placed on disease prevention.

There is testing done all the way from the farm to the fork. Food companies want to sell safe products, but they also want to protect their brand name, which is most directly influenced by a recall.

—Tom Weschler, Strategic Consulting Inc.

Starting in 1997, the USDA’s Food Safety and Inspection Service implemented the Pathogen Reduction/Hazard Analysis Critical Control Point (HACCP) system in all 6,000 federally inspected meat, poultry, and egg products plants over a three-year period. In addition, in 1996, the CDC, USDA, and FDA established the Foodborne Diseases Active Surveillance Network (FoodNet) surveillance system to quantify, monitor, and track the incidence of laboratory-diagnosed cases of foodborne illnesses.

“The public health case is driving food microbiology now,” said Dr. Zink. He added that FoodNet and PulseNet, a national network of public health and food regulatory agency laboratories coordinated by the CDC, have improved scientists’ ability to identify a pathogen and the specific food that carries it. It is more than a thousand times better than was possible even a decade ago, he said.

Faster Turnaround

With millions of dollars and reputations at stake during recalls, there is a push toward more rapid test results. In comparison with earlier methods, which could take up to a week, some results are now available within eight hours—a factory shift. “The purpose is to do one-shift tests,” said Daniel Fung, PhD, professor of food science at Kansas State University in Manhattan, Kan. Dr. Fung, a member of the Food Quality editorial advisory board, pioneered a method to miniaturize a most probable number system that can test for pathogens within a single factory shift.

The incidence of E. coli O157:H7, one of the most severe foodborne diseases, declined 36% from 2002 to 2003, according to a report by the Centers for Disease Control and Prevention and others. The overall incidence of E. coli O157:H7 has declined 42% since 1996.
The incidence of E. coli O157:H7, one of the most severe foodborne diseases, declined 36% from 2002 to 2003, according to a report by the Centers for Disease Control and Prevention and others. The overall incidence of E. coli O157:H7 has declined 42% since 1996.

The food industry has followed some of the test techniques used in the pharmaceutical industry, but that can be challenging. Molecular techniques in the clinical industry may not always be appropriate in the food industry because the latter has such low margins, said Morgan Wallace, PhD, senior research microbiologist at DuPont Qualicon in Wilmington, Del.

DuPont offers a PCR-based system called BAX that came out of clinical diagnostics in the mid 1990s, when assays for the food industry could be developed. The company has 13 PCR assays that target nine microbes. DuPont has sped up results by taking measurements at the end of each PCR cycle instead of at the end of each batch. The result is that after E.coli is enriched for about eight hours, results are available in about 55 minutes, compared to 3.5 hours using the prior method. And BAX can detect multiple species in parallel in one PCR reaction.

Strategic Consulting’s Weschler believes the food industry is pushing ahead of pharma with rapid methods. “The food industry is further along in rapid methods than pharma, and it is driving new methods,” he said. Dr. Bailey of bioMerieux is not as optimistic. “It will be a long time before we can significantly shorten” the test result time, he said.

Others point to new technologies. For example, Mike Doyle, director of the Center for Food Safety at the University of Georgia in Griffin, Ga., said new methods using ribozomal RNA can produce more copies than DNA, providing more targets for molecular tests and eliminating an extensive enrichment process. “New technology will probably revolutionize the industry.” ■

 

Valigra is a science journalist based in Cambridge, Mass. Contact her at lvaligra@gmail.com.

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