The supply chain that brings meat to market worldwide is highly complex and usually very efficient. But when disruptions in one part of the world can result in transportation delays an ocean and a continent away, meat spoilage becomes a very real risk to food producers, vendors and consumers. This is especially true if food inspection protocols are lax.
There are several factors that can cause meat to spoil, including bacteria, enzymes, and oxidation. Spoilage can cause meat to develop off flavors and odors, and in some cases, it can make the meat unsafe to eat. This can be a major problem for food producers, as spoiled meat can lead to product waste, loss of revenue, and damage to the producer’s reputation. Therefore, to prevent spoilage, food producers must carefully control the temperature and humidity of the meat throughout the supply chain, and properly package and label the meat to ensure its freshness and safety.
To improve food safety, a group of Concordia researchers designed a new, inexpensive, reliable and consumer-friendly technology that identifies the presence of the toxin putrescine in beef. As its name denotes, Putrescine is a toxic chemical compound that is produced by the breakdown of proteins in meat. It is a common cause of spoilage in beef, as well as other meats and fish. When putrescine is present in high levels, it can give the meat an unpleasant odor and taste, and can make it unsafe to eat. If spoiled meat consumed in large doses, it can cause headaches, vomiting, diarrhea and heart palpitations. It has also been linked to higher risks of colorectal cancer.
There are many different biosensors that can be used to check the quality of food. Some of these sensors use specialized enzymes or bacteria to detect certain contaminants in food, while others use electrical or optical techniques to measure the presence of specific chemicals or compounds. Some of the most common biosensors used for food quality testing include:
- Enzyme-linked immunosorbent assay (ELISA) biosensors, which use antibodies to detect the presence of specific proteins or other molecules in food.
- Bacterial biosensors, which use living bacteria to detect the presence of specific contaminants in food.
- Optical biosensors, which use light-sensitive molecules to detect the presence of specific chemicals in food.
- Electrical biosensors, which use electrical signals to measure the presence of specific chemicals or compounds in food.
However, these biosensors are complex to use, therefore, rapid, easy-to-use biosensors for people to check the quality of the food are needed.
The researchers explain how they developed the paper-based synthetic biosensor in the journal Applied Bio Materials using a protein found in nature.
“Making a rapid, easy-to-use biosensor for people to check the quality of the food they are eating is empowering,” says lead author Alaa Selim, MSc 22, now pursuing her PhD at the University of Saskatchewan’s Vaccine and Infectious Disease Organization. “We wanted to make a device that anyone could use, that is disposable and contained no toxic materials.”
Her co-authors include her former PhD student colleagues at the Shih Microfluidics Lab, James Perry, Mohamed Nasr and Jay Pimprikar, as well as Steve Shih, associate professor of electrical and computer engineering.
Results improve over time
The technique behind the sensor relies on cell-free protein synthesis, which produces a protein using the biological machinery of a cell without actually using the living cell. The researchers found that the putrescine repressor protein PuuR, found in the E.coli bacteria, could be used to indicate the presence of putrescine.
In a lab test, putrescine was added to the cell-free system that was producing the repressor in a solution and placed on a paper device to see if the researchers could visually see the presence of putrescine under UV light. After an hour, the researchers found that the biosensor was detecting the presence of putrescine; after four hours, they were confident their readings were highly accurate.
They then proceeded to test actual meat samples. Small slivers of beef kept in a freezer, in a refrigerator and at room temperature were compared to see how much putrescine accumulated over the span of several days. As expected, the samples from the freezer and refrigerator had very low levels of putrescine, while the one kept at room temperature showed quite high levels — enough to sicken anyone who might eat it. They compared the results from their biosensor to those of a high-tech chromatography used in food inspection and found their results to be somewhat correlated.
A foundational technology
While a fully functional, commercially available version of the biosensor will not be available any time soon, the researchers are optimistic about its potential.
“We believe our work is a first step toward using sensors in the meat preparation industry,” says Shih, the Concordia University Research Chair in Microfluidics for Biological and Chemical Analysis. “In addition, we believe this type of sensing can be used for other fields like environmental sampling of heavy metal contamination and cancer and disease diagnostics.”
For Selim, the most important thing to a consumer is their health and the health of their family. “I want anyone, regardless of their background in technology, to be able to use this, whether it’s a college student, a busy mom or people working in the restaurant industry.”