Ever wonder how long your food is good for after its “sell-by” date? Well, now you can take the guesswork out of the equation.

Researchers have developed a new laser tool for detecting bacterial growth in packaged food. The low-cost, fast laser can detect bacteria inside both packaged food and medical blood supplies, without having to disturb their packaging, reports Medical News Today.

A group of researchers from Zhejiang Normal University in China and Umea University in Sweden have developed the laser. They say packaged food items are given an unnecessarily short shelf life, and hope food waste can be reduced with a better understanding of bacterial growth.
So, how does it work?

“Microorganism growth is always associated with the production of carbon dioxide (CO2),” Jie Shao, associate professor at the Institute of Information Optics at Zhejiang Normal University, told Business Wire.

“By assessing the level of CO2 within a given closed compartment — bottle or bag — it’s possible to assess the microbial growth.”

The researchers eventually hope to test bacterial growth in a wide variety of products, expanding beyond food items and medical supplies.