Sensors for Monitoring Volatile Chemicals in Meat Products

By Benedette Cuffari, M.Sc.Jul 13 2020

Image Credit: pilipphoto/Shutterstock.com

There has been an increasing demand to replace traditional odor detection methods with novel gas sensors to ensure the distribution of safe meat products around the world.

Degradation of Meat

Muscle foods, which include meat, poultry, and fish products, are rich in a wide range of nutritional substances, including protein, lipids, and minerals. As a result, these muscle foods are considered staple food items in the diet of many individuals around the world.

Unfortunately, many of the components of meat that make them valuable can quickly degrade into various volatile compounds, including aldehydes, alcohols, sulfide, and ammonia, following exposure to microorganisms or other endogenous compounds.

Once these types of volatile chemicals arise, the quality of meat products can quickly deteriorate. Although many of these volatile chemicals, which can include those detailed in Table 1, often exist at low thresholds in different muscle foods, these low concentrations can still alter meat composition.

To reduce the occurrence of these chemical reactions, meat industries around the world enforce careful handling, processing, and storage of raw meat before they reach the consumer.

Table 1: An overview of the different volatile chemicals that can be found in different meat products. This table was adapted from that provided by Jiang, S. & Liu, Y., 2020.

Quality Detection of Meat

Several quality detection methods evaluate the physicochemical properties of meat products during their processing and storage.

Many of these detection methods evaluate the odor, color, texture, and nutritional values of meat products, as changes in these properties can determine whether a given piece of meat is considered acceptable for consumer use.

Odor quality is considered the most critical factor influencing the purchase behavior of consumers. Therefore, several different techniques evaluate these properties of meat products.

Gas chromatography-mass spectrometry (GC-MS), for example, is one analytical method that is often used to evaluate the volatile compound profile of meats. Despite its widespread use, GC-MS is associated with several disadvantages, including time-consuming requirements, destruction and complex sample preparation, high operation costs, and the need for highly skilled operators to operate this instrument.

Why Gas Sensors?

Many of the limitations associated with traditional analytical methods for odor detection in meats such as GC-MS have led industry researchers to turn to alternative methods that quickly provide accurate results, are operation-friendly, and can provide on-line detection of odor quality in meat products.

Gas sensors have rapidly evolved over the past several years to be ideal analytical tools that meet these needs of the meat industry.

The basic working principle of most gas sensors is to sense materials that are placed on the surface of transducer devices. Many gas sensors will utilize metal oxide and biomaterials, such as receptors or cells, as their sensing materials. In contrast, common signal transducers can include those based on surface acoustic waves (SAWs), surface plasmon resonators (SPRs), quartz crystal microbalances (QCM), and metal-oxide semiconductors (MOS). 

Biosensors

Several different types of biosensors have been evaluated for their usefulness in the detection of volatile compounds in meat products, some of which include receptor-based and enzyme-based biosensors.

Typically, biosensors will use a specific biological sensing element that will undergo a binding reaction with the volatile compound of interest and relate this information to a physicochemical transducer that is either in immediate contact with or is integrated within the sensing element.

The most popular sensing elements used in receptor-based biosensors include odorant-binding proteins, as well as the olfactory receptors originating from mosquitos, humans, rats, or zebrafish.

Odorant-binding proteins, for example, can be coated onto the surface of SAWs for a low-cost biosensing device that is highly sensitive to the weight, volume, and conductivity of samples placed onto its surface. The two most common volatile elements that are measured by odorant-binding proteins coupled with SAW detection devices include octenol and carvone.

MOS Sensors

Despite the advantages of biosensors, they are often limited in their ability to eliminate interference by environmental factors such as electromagnetic waves, humidity, and temperature, all of which usually exist in a food production plant. As a result, MOS sensors are often the sensor of choice for food detection purposes as a result of their robustness, stability and recyclability.

Researchers around the world have designed and tested various types of MOS sensors for the analysis of volatile chemicals in muscle food products, particularly in fish.

During the spoilage of fish, trimethylamine oxide (TMAO), which naturally exists in this type of muscle product, will be converted to dimethylamine and TMA, both of which are volatile compounds that are often measured to determine the freshness of fish products.

By measuring the resistance changes that occur to the metal oxide, MOS sensors can accurately measure TMA concentrations at detection limits that often exceed 15 parts per million (ppm).

Some of the different sensing elements that have been evaluated for their TMA measurement capabilities include tin oxide (SnO₂), nanosized titanium oxide (TiO₂), gold oxide (GO)/ copper oxide (Cu₂O) nanocomposites, and poly 3-hexylthiophene (P3HT).

Sources and Further Reading

• Jiang, S., & Liu, S. (2020). Gas sensors for volatile compounds analysis in muscle foods: A review. Trends in Analytical Chemistry 126. doi:10.1016/j.trac.2020.115877.
• Dominguez, R., Pateiro, M., Gagaoua, M., et al. (2019). A Comprehensive Review on Lipid Oxidation in Meat and Meat Products. Antioxidants 8(10). doi:10.3390/antiox8100429.

Kosowska, M., Majcher, M. A., & Fortuna, T. (2017). Volatile compounds in meat and meat products. Food Science and Technology 37(1). doi:10.1590/1678-457x.08416.

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