As food travels from farms to food processors to grocers and finally to your table, food safety is a constant concern. From farm fields to your kitchen, food is vulnerable to contamination by microscopic organisms that cause illness.
Now the University of Wisconsin-Madison has hired four scientists whose research will strengthen efforts to protect food from contamination.
The researchers are part of the University”s Cluster Hiring Initiative, which builds faculty teams around fields of knowledge. The program, which began in 1998, emphasizes collaboration across different fields, in order to bring a variety of fresh perspectives to complex issues.
The director of the Food Research Institute saw the initiative as an opportunity to strengthen food safety research. “There was a serious deficiency – a low critical mass in that area,” says Michael Pariza, who chaired the committee that proposed the food-safety hires.
Each scientist is associated with the Food Research Institute in the College of Agricultural and Life Sciences. They are:
* Jaehyuk Yu, a fungal molecular geneticist with the Department of Food Microbiology and Toxicology;
* Nancy Keller, a molecular biologist with the Department of Plant Pathology and Department of Food Microbiology and Toxicology;
* Ferencz Denes, a plasma engineer with the Department of Biological Systems Engineering, and the College of Engineering”s Center for Plasma-Aided Manufacturing; and
* Laura Knoll, a molecular parasitologist with the Department of Medical Microbiology and Immunology in the School of Medicine.
Although the four scientists have been on the faculty for less than two years, they are already collaborating on important problems. Yu and Keller are trying to reduce problems with toxins from molds that contaminate grain in farm fields. Denes and food microbiologist Amy Wong are developing new methods for protecting food during processing. Knoll, who was recently appointed, will also be collaborating with colleagues in research on parasites such as cryptosporidium, which contaminated drinking water in Milwaukee and sickened thousands of people.
Mold on crops a concern for farmer and consumer alike
Certain molds that grow on crops can produce various toxins, some of which cause cancer and make livestock sick. Crops contaminated with these toxins cannot be sold as food for humans. Yu and Keller are trying to find out how fungi grow and reproduce on crops, and how to keep them from producing toxins.
“You must know the enemy”s weapons and defenses, and how it will react,” explains Yu. “If you know the enemy thoroughly, you will be able to fight and control the enemy.” The “enemy” Yu speaks of is Aspergillus, a group of molds that can grow on many types of grains and nuts. In Wisconsin, Aspergillus periodically causes major problems with corn, especially if there is a hot, dry growing season.
When some problematic Aspergillus species reproduce, they produce spores that contain a toxin called aflatoxin. The Food and Drug Administration considers aflatoxin to be a strong carcinogen, and limits the amount in food for human consumption. If livestock eat feed contaminated with aflatoxin, they become sick, gain less weight, produce fewer eggs or less milk, and may die. Thus farmers are unable to sell corn contaminated with aflatoxin or use it to feed their livestock.
To understand how fungi grow, reproduce and produce toxin, Yu examines the signals and pathways that tell Aspergillus to move to different stages in its life cycle. He thinks that certain types of proteins are the key to activating growth and reproduction. Keller also studies Aspergillus, as well as investigates its interaction with plants. She”s interested in plant substances that induce or inhibit fungal growth. She thinks she”s identified a natural fatty acid that Aspergillus needs to develop, as well as natural anti-fungal compounds that plants use to protect themselves.
Eventually, the scientists think that selective breeding or genetic engineering can be used to disrupt the life cycle of Aspergillus. If the fungus grows without releasing spores, it will eventually “melt” and die, according to Yu. The researchers hope to learn the basic mechanisms that control the fungal life cycle from their work with Aspergillus, and apply what they learn to other species-such as Fusarium species-that produce major fungal toxins.
“We want to increase the quality of life, and benefit humans and society,” Yu says. The two believe their joint approach is powerful because not all of their effort is in one area, allowing them to study what goes on throughout the entire life cycle of the fungus.
By working together, Keller and Yu are able to share resources and accomplish more in a shorter period of time, Keller says. Students will also benefit from having Yu and Keller on campus: “We”re going to teach a course together next year,” Keller says.
By altering surface properties, researchers reduce contamination
To keep food safe in your kitchen, you need to clean the utensils and surfaces you use to prepare food. Industrial food processors also must find ways to guard against pathogens such as Salmonella and E. coli, as well as other bacteria that can impart bad flavors to foods. They need reliable ways to clean and disinfect the equipment and other surfaces they use in handling and packaging food.
“Even with diligent cleaning, there can still be contamination,” says Wong. Some organisms are resistant to sanitizers, and repeated food preparation cycles may leave tiny food deposits in the nooks and crannies of conveyor belts, blades and other surfaces, she says.
Bacteria that attach to these surfaces may multiply forming layers of cells called biofilms. These biofilms can contaminate fresh food, and cause it to turn foul.
Denes and Wong think that changing the properties of food preparation surfaces can help processors keep their facilities clean and sanitary. The two, who combine their expertise in everything from advising students to conducting research, are finding ways to alter the top layers of materials. They want to make it difficult for bacteria to attach to materials, and also want to incorporate antibacterial agents to surfaces.
Scientists can”t yet explain exactly how bacteria adhere to surfaces, but changing the properties and characteristics of a surface can make it difficult for bacteria to attach and form colonies. Denes uses what he calls “dry chemistry” to do this. Instead of using large amounts of toxic chemicals and solvents, he uses cold plasma – a special electrically charged gas-to treat surfaces that will be in contact with food.
The plasma interacts with the top layer of even inert surfaces, while keeping the material”s basic properties unchanged. Using a patented device, Denes and Wong can modify a surface, and add antibacterial agents to its outer layer. They can also use plasma to disinfect and decontaminate surfaces, water and air.
The food industry has expressed an interest in using plasma-treated surfaces and in disinfecting their food preparation devices with plasma. The U.S. Navy is also considering using plasma technology to remove corrosion-causing biofilms from surfaces on their ships. The research may also lead to new methods for sterilizing and altering hospital surfaces and medical devices, such as catheters.