Researchers from Ryerson University have found that placing a frozen juice drink inside a child’s lunch box can significantly reduce the chances of the lunch developing bacteria.

Marilyn Lee, a professor in the University’s School of Occupational and Public Health, co-authored the investigation with student Ishmael Davis. Lee found that the key to avoiding a potentially poisonous lunch pack was to keep the contents as cold as possible.

“Ideally, schools would provide refrigeration for lunches but we know that’s not always the case,” acknowledged Lee: “In the absence of refrigeration, using a frozen juice box or an ice pack is a convenient way to slow the development of bacteria.”

The researchers monitored the temperature of egg salad sandwiches over a period of five hours, and found that they remained colder when the lunch box contained a frozen juice box rather than a cold, but unfrozen, juice box.

“It’s better to keep sandwiches as cold as possible to at least slow bacterial growth,” concluded Lee.

The study’s results were recently published in the Canadian-based journal Environmental Health Review.