How to tell if your meat is fresh with a new biosensor

Meat is one of the most consumed foods in the world, but also one of the most prone to spoilage. Eating spoiled meat can cause serious health problems, such as food poisoning, nausea, vomiting, diarrhea, and even organ failure. Therefore, it is important to determine the freshness of meat before consumption.

However, the conventional methods for assessing meat freshness, such as sensory evaluation, microbial analysis, and chemical tests, are often subjective, time-consuming, costly, and require specialized equipment and personnel. Moreover, they may damage the meat quality and reduce its shelf life.

To overcome these limitations, researchers from Vietnam and Russia have developed a new biosensor that can accurately and efficiently measure the freshness of meat by detecting a key indicator of meat aging: hypoxanthine (HXA).

What is HXA and why is it important?

HXA is a compound that forms when adenosine triphosphate (ATP), the energy-providing molecule present in living cells, undergoes decomposition after the animal dies. ATP is responsible for providing energy to cells and maintaining their functions. When an animal stops breathing, ATP synthesis also stops, and the existing ATP molecules gradually break down into other compounds, such as inosine, xanthine, and HXA.

The decomposition of ATP affects the flavor, texture, color, and safety of meat. As HXA accumulates in meat, it causes the meat to become sour, tough, dark, and susceptible to bacterial growth. Therefore, the level of HXA in meat can indicate its freshness and quality.

How does the biosensor work?

The biosensor developed by the researchers is based on a porous graphene electrode modified by zinc oxide nanoparticles. Graphene is a two-dimensional material made of carbon atoms arranged in a honeycomb lattice. It has excellent electrical, mechanical, and thermal properties, making it suitable for biosensing applications. Zinc oxide is a semiconductor material that has high affinity and selectivity for HXA molecules, enhancing the sensitivity and stability of the biosensor.

The biosensor works by measuring the electrical signal generated by the oxidation of HXA on the electrode surface. When HXA comes into contact with the electrode, it loses electrons and becomes oxidized, while the electrode gains electrons and becomes reduced. This creates a current flow that is proportional to the concentration of HXA in the sample. By measuring the current, the biosensor can determine the amount of HXA and thus the freshness of meat.

How to use the biosensor?

To use the biosensor, the researchers first prepare a solution sample from the meat by mixing it with water and filtering it. Then, they drop a small amount of the solution onto the electrode and connect it to a potentiostat, a device that controls the voltage and measures the current. The biosensor then displays the current value, which can be converted into HXA concentration using a calibration curve.

The biosensor can be used to test different types of meat, such as pork, beef, chicken, and fish. The researchers tested the biosensor on pork tenderloins purchased from a supermarket and found that it performed with over 98% accuracy, favorable detection range, and low detection limit. They also compared the biosensor with other methods, such as high-performance liquid chromatography (HPLC) and microbial analysis, and found that the biosensor was faster, cheaper, and easier to use.

What are the advantages and applications of the biosensor?

The biosensor offers several advantages over the existing methods for meat freshness assessment, such as:

  • High sensitivity and selectivity: The biosensor can detect HXA at very low levels (nanomolar range) and distinguish it from other interfering substances, such as uric acid, ascorbic acid, and glucose.
  • Fast and simple operation: The biosensor can provide results within minutes, without the need for complex sample preparation, expensive instruments, or skilled personnel.
  • Low cost and portability: The biosensor is made of cheap and abundant materials, such as graphene and zinc oxide, and can be fabricated using simple techniques, such as laser irradiation and drop casting. The biosensor is also small and lightweight, making it easy to carry and use in different settings.
  • Nondestructive and noninvasive measurement: The biosensor does not damage the meat quality or reduce its shelf life, as it only requires a small amount of sample and does not involve any chemical reagents or high temperatures.

The biosensor has potential applications in various fields related to meat production, processing, distribution, and consumption, such as:

  • Food industry: The biosensor can help food manufacturers, processors, retailers, and consumers to monitor and control the quality and safety of meat products, and to optimize the storage and transportation conditions.
  • Veterinary medicine: The biosensor can help veterinarians and animal health professionals to diagnose and treat diseases and infections related to meat consumption, such as gout, kidney stones, and urinary tract infections.
  • Environmental monitoring: The biosensor can help environmental scientists and engineers to detect and quantify the pollution and contamination of water and soil by HXA and other nitrogenous compounds, which can cause eutrophication, algal blooms, and fish kills.

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