The Listeria outbreak in Florida has so far led to at least one death, 22 hospitalizations, and ice cream product recalls since January.

People get Listeria infection from eating foods contaminated with soil, undercooked meat, or raw or unpasteurized dairy products. Listeria can cause convulsions, coma, miscarriage, and birth defects. It is the third leading cause of food poisoning deaths in the United States.

To avoid invisible food dangers, people check the dates on food packages.

But dates, for example, have little to do with when food expires or becomes less safe to eat.

Jill Roberts, associate professor of global health at the University of South Florida and a microbiologist, used molecular epidemiology to study the spread of bacteria in food.

He explained that a more science-based product dating system could make it easier for people to distinguish between foods they can eat safely and those that could be dangerous.

The US Food and Drug Administration reports that consumer confusion about product labels is likely responsible for about 20% of food waste in the home, at an estimated cost of US$161 billion annually.

It is reasonable to believe that date labels exist for safety reasons, as the federal government mandates rules to include nutrition and ingredient information on food labels.

For example, a food producer might survey consumers in a focus group to choose a “use by” date six months after the product was produced because 60% of the focus group no longer liked the taste. Small manufacturers of similar food may play a game of imitation and put the same history on their product.

One industry group, the Food Marketing Institute and the Grocery Manufacturers Association, suggests its members mark food “best if used before” to indicate how long a food is safe to eat, and “use by” to indicate when a food has become unsafe.

But the use of these more accurate tags is optional. Although the recommendation is motivated by a desire to reduce food waste, it is not yet clear if this recommended change will have any effect.

A joint study by the Harvard Food Law and Policy Clinic and the National Resources Defense Council recommends eliminating dates aimed at consumers, citing the potential for confusion and waste.

Instead, the research indicates that manufacturers and distributors use “production” or “packaging” dates, along with “sale” dates, which are targeted at supermarkets and other retailers. The dates to the retailers indicate the amount of time the product will remain of high quality.

The Food and Drug Administration considers some products to be “potentially dangerous foods” if they have properties that allow microbes to thrive, such as moisture and an abundance of nutrients that feed the microbes.

These foods include chicken, milk and tomato slices, all of which have been linked to outbreaks of foodborne diseases. But there is currently no difference between the date label used on these foods and those used for the more stable nutrients.

Infant formula is the only food product that is scientifically dated for “use by the latest” and regulated by the government. It is routinely tested in the lab for contamination.

But infant formula also undergoes nutrition tests to determine how long it takes nutrients — especially protein — to break down. To prevent malnutrition in children, the “use by” date on infant formula indicates how long it is no longer nutritious.

It is relatively easy to measure the nutrients in foods. The FDA already does this regularly. The agency issues warnings to food producers when the nutrient contents listed on their labels do not match what the Food and Drug Administration laboratory finds.

Microbial studies are a scientific approach to making meaningful history labels on foods. In the lab, microbial study might involve letting perishable food spoil and measuring the amount of bacteria that grows in it over time.

Scientists also do another type of microbial studies by watching how long it takes microbes like Listeria to reach dangerous levels after the microbes are intentionally added to food to monitor what they do, noting details such as the growth in the amount of bacteria over time.

Determining the shelf life of food using scientific data on both its nutrition and safety can significantly reduce waste and save money while increasing the cost of food.

But in the absence of a standardized food-dating system, consumers can rely on their eyes and nose, deciding to ditch the fuzzy bread, green cheese or a bag of smelly salad.

People can also pay close attention to the timing of perishable foods, such as deli, where microbes grow easily.