Nearly every month, it seems, comes a new report. In March, there was news of contaminated romaine lettuce, which eventually led to five deaths and sickened over 200 people across the US and Canada. In May, about 100 people in California got sick after eating raw oysters shipped from British Columbia. Then, at the end of July, the baking company Pepperidge Farm issued a recall for a few flavors of its seemingly innocuous, kid-friendly snack, Goldfish crackers.
And the list goes on. At first blush, lettuce, oysters and Goldfish might not seem that similar — but they and a host of other foods, even such things as peanut butter, baby formula and potato chips — can all harbor safety risks. The romaine, shipped from Yuma, Arizona, was contaminated with Escherichia coli O157:H7. The raw oysters were contaminated with norovirus, a pathogen responsible for most foodborne illnesses in the US. The Goldfish snacks? They were recalled because Pepperidge Farm thought one of the seasoning ingredients might contain Salmonella.
The US Centers for Disease Control and Prevention estimates that each year one in six Americans gets sick after eating contaminated food, and over the past decade, the average annual number of food recalls has steadily climbed. A surprising array of food groups — from fresh produce and meat to packaged dry items — has been recalled after outbreaks or customer complaints, or when random testing turned up spores of bacteria or traces of viruses that can cause food poisoning. These pathogens include Salmonella, Listeria, Shigella, norovirus and the especially dangerous E. coli O157:H7. In 2017, there were 456 food recalls, about a third of which were due to microbe-related contamination, according to a report by Food Safety Magazine. (Many recalls are issued if a food might include — or have come into contact with — unlabeled potential allergens.)
The rise in recalls may partly be due to an uptick in vigilance and sensitivity. “We’ve really advanced in science, and have better methods for detecting outbreaks,” says Jeff Farber, a food microbiologist at the University of Guelph in Canada. Indeed, the United States and Canada have some of the safest food supplies in the world, mostly owing to strong federal surveillance systems, he says.
But despite this watchfulness, and the existence of food preservation technologies such as thermal processing and irradiation that normally work well, people can still sicken and die from contaminated food. Existing technologies can’t deal with all threats. Plus, new concerns over controlling viruses, a small uptick in recalls of dry foods, the high costs of safety recalls, and a shifting public appetite for more fresh foods have all created an urgent need for food researchers to seek new approaches, scientists say.
The challenge is to find scalable techniques that destroy microbial threats while preserving flavors and nutritional value. That’s not easy, since many methods that kill microbes also tend to degrade vitamins or change a food’s structure — boiling lettuce will help clean it, but the resulting slop might not appeal to salad lovers.
Among the many routes to food sterilization now being explored — everything from microwaves to pulsed UV light and ozone gas — two emerging technologies are attracting a lot of interest: cold plasma and high-pressure processing. Neither method will solve everything, but both could help improve the safety of the food supply.