Bad food? New sensors will show with a glow | Science News for Students

Bad food? New sensors will show with a glow

Food packaging with these patches could help people avoid potentially sickening germs
Jun 4, 2018 — 6:45 am EST
raw chicken

Is this chicken safe to eat? New glowing sensors built into food packaging might soon alert cooks to risky food.


Sensors in packaging could someday warn you about tainted food in time to keep you from eating it. The plastic patches could detect bacteria that might poison diners.

Carlos Filipe is a chemical engineer at McMaster University in Hamilton, Canada. He and his team developed the new sensors. To make them, the researchers coated a flexible film in molecules that glow in the presence of E. coli. These bacteria are usually harmless. But certain strains of this species can seriously sicken people. A leading source of exposure to those bacteria? Food.

This new sensor glows around molecules that E. coli cells produce. So the material doesn’t have to directly touch the germs to know if they’re there.

The sensors give off what’s known as fluorescence. They take in energy at one wavelength and emit it as a glow at another wavelength. You can’t see that glow under normal light. You have to shine an ultraviolet lamp or a fluorescence scanner to detect it.

The new sensors are about the size of postage stamps. The researchers tested these plastic patches on meat and apple juice hosting E. coli. The sensors lit up brightly. But when the sensors were touching untainted food samples, they didn’t glow. Filipe’s team described its new sensors online April 6 in ACS Nano.

Other scientists have developed tools to detect fluorescence that can attach to a smartphone. These devices are only the size of a matchbox. People could use them to check packaged food at home before opening it, Filipe says. If the food sensor was glowing, a person would know the food was unsafe. Grocery stores could also provide scanners so customers could check a food before buying it.

Next up, the McMaster group plans to make films that glow near other dangerous bacteria, says Tohid Didar. He is a mechanical engineer on the team. One of those bacteria might be Salmonella, which can cause fever, cramps or diarrhea.

Foodborne illnesses such as Salmonella and E. coli kill some 420,000 people worldwide each year, according to the World Health Organization. But food packaging with built-in microbe monitors might warn people of tainted foods so that they can steer clear of them.

Power Words

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bacteria     (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemical engineer     A researcher who uses chemistry to solve problems related to the production of food, fuel, medicines and many other products.

diarrhea     (adj. diarrheal) Loose, watery stool (feces) that can be a symptom of many types of microbial infections affecting the gut.

E. coli     (short for Escherichia coli) A common bacterium that researchers often harness to study genetics. Some naturally occurring strains of this microbe cause disease, but many others do not.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

germ     Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

mechanical engineer     See mechanical engineering.

mechanical engineering     A research field in which people use physics to study motion and the properties of materials to design, build and/or test devices.

microbe     Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

monitor     To test, sample or watch something, especially on a regular or ongoing basis.

Salmonella     A genus of bacteria that can cause disease in people and animals.

sensor     A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.

smartphone     A cell (or mobile) phone that can perform a host of functions, including search for information on the internet.

species     A group of similar organisms capable of producing offspring that can survive and reproduce.

strain     (in biology) Organisms that belong to the same species and share some small but unique characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.


Journal: H. Yousefi et al. Sentinel wraps: Real-time monitoring of food contamination by printing DNAzyme probes on food packaging. ACS Nano. Published online April 6, 2018. doi:10.1021/acsnano.7b08010.

Journal: H. Zhu et al. Cost-effective and compact wide-field fluorescent imaging on a cell-phone. Lab on a Chip. Vol. 11, January 21, 2011, p. 315. doi:10.1039/c0lc00358a.