Listeria monocytogenes bacteria, shown growing in a petri dish for analysis, are present in the natural world.

With new federal food safety regulations pending later this year, the industry finds itself dealing with an old problem: microbial contamination. The spring outbreak of bird flu only complicated matters. Microbiologically speaking, 2015 has been a busy year for food safety.

Bird flu pushed ingredient costs higher and made supplies scarcer but did not pose food safety dangers. The overwhelming majority of food manufacturers use processed eggs, and pasteurization, which all processed eggs must undergo, kills the virus involved.

But it’s not that simple with bacteria like E coli, listeria, salmonella and staph that cause human diseases or fungi like fusarium that give off mycotoxins that damage people’s health. The problem is, these microbes are present in the natural world, in the soil and on crops, as well as in the processing environment, through raw materials and the presence of human beings.

Mold, microbial bad boys

Among bakers and snack food processors, fungi pose the biggest concerns. The food industry knows this class of microbes by a more familiar term: mold. Bacteria and viruses cause health problems by infection; molds cause them by giving off metabolic byproducts known as mycotoxins (the poisonous compounds produced by certain fungi). Grain-based products are at the most risk from vomitoxins and aflatoxins. Both are poisonous when consumed in high doses by humans and animals.

Vomitoxin, often called DON (the abbreviation for its scientific name, deoxynivalenol), occurs in grains infected with fusarium mold, a.k.a. “head blight” or “scab.” This common mold grows on wheat, corn, oats, barley and other cereal grains and also generates fumonisin, another mycotoxin. Aspergillus molds produce aflatoxin, a known carcinogen implicated in liver cancer. It is of most concern in corn.

The Food and Drug Administration (FDA) restricts vomitoxin in finished products such as wheat flour to 1 ppm. Dry milled corn products can contain no more than 2 ppm fumonisin, with limits of 4 ppm in cleaned corn for masa and 3 ppm in unpopped popcorn. In its guidance document concerning fumonisin, FDA stated this mycotoxin is associated with a variety of health problems in livestock, but currently, no direct evidence suggests adverse health effects in humans. However, the agency set the action level for aflatoxins much lower: 20 ppb in all foods, including animal feed.

“It shouldn’t surprise us that food manufacturers have such a battle with microbes because they are out there in the environment,” said Shari Plimpton, PhD, vice-­president and director of food industry programs, Center for Innovative Food Technology (CIFT), Dublin, OH, and a consultant to the Snack Food Association (SFA). “They are part of the scene, but we still need to try to keep them out of the processing plant.”

Weather and storage conditions affect mycotoxin development. FDA noted in its guidance documents that high levels are associated with hot and dry weather followed by periods of high humidity and in stored crops damaged by insects.

“The 2015 wheat harvest is just underway now, and I have not seen any reports yet about fusarium, scab or similar conditions,” said Chris Miller, PhD, senior director of research, innovation and quality, Engrain LLC, Manhattan, KS.

Still, bacteria are not in the clear for causing food contamination; the common ones cause most problems. They, too, are plentiful in the environment.

“With salmonella, there are more than 2,000 serotypes in nature,” said Lakshmikantha (Kantha) Channaiah, PhD, director of microbiology, AIB International, Manhattan, KS. “It can survive well in low-water activity or low-­moisture environments. It’s a champ of low-moisture foods.

“With Listeria monocytogenes, you have much the same thing,” he continued. “It is everywhere in nature. It can survive and grow under low temperatures — below 40°F, which represents most refrigerator conditions.” The most recent problems encountered in ice cream are an example of listeria surviving under frozen conditions.

“Staphylococcus aureus also can pose issues,” Dr. Channaiah added. “When workers get sick and are not trained in preventative methods, it can be a potential problem in any food environment.”