You pick up a container of milk and glance at the “best before” date. Does the thought of taking a whiff turn your stomach? A new test might spare you, and your nose, a foul encounter. It might also save you from getting sick.

A team at McMaster University in Canada has developed a transparent test patch that can be applied to or incorporated in packaging for meat and other food subject to spoilage. The patch is printed with molecules that can show contamination from harmful bacteria like E. coli and Salmonella in real time. If pathogens are present, it emits a signal that can be read via a smartphone or another device.

The team predicts the label may one day replace the “best before” date on food and drink packaging. They say the patch would give consumers something more reliable than an expiration date to determine whether something is safe to eat or drink.

As anyone who has had one knows, foodborne diseases are not to be taken lightly. The Centers for Disease Control and Prevention estimates that 48 million Americans contract such illnesses each year. Of those, 128,000 people are hospitalized and 3,000 cases are fatal.

Worldwide, up to 600 million people fall ill from foodborne pathogens each year, according to the World Health Organization. Of those, 420,000 people die as a result of consuming contaminated food. Children under the age of 5 are particularly susceptible.

The researchers say the technology may one day be used in other ways, such as health care settings. They envision bandages that can detect wound infection and surgical instrument wrapping that can signal the presence of harmful pathogens.

All in all, the team has big dreams for their small patch.