Harnessing the power of spectroscopy for food safety

April 2022 | Canadian Food Inspection Agency | by Dr. Thomas Teklemariam

The Canadian Food Inspection Agency (CFIA) is always looking for ways to enhance food safety. Electromagnetic radiation (EMR) can provide a unique perspective on what’s in food and is extremely useful in investigations into food safety, quality and potential fraud.

All light waves, even those that are invisible to the naked eye, are collectively referred to as electromagnetic radiation (EMR). EMR is a stream of energetic photons travelling at the constant speed of light in a wave-like rhythm and its energy is equivalent to the frequency of the wave. All of life’s existence and many technologies we use every day rely on various forms of EMR: radio waves, microwaves, infrared radiation, visible light, ultraviolet rays, X-rays and gamma rays, in order of increasing energy.

Understanding spectroscopy

When EMR collides with matter, energy is transferred. The atoms and molecules of the material that EMR collides with shape the nature of the interaction. Spectroscopy is the study of interactions between EMR and matter. How matter absorbs, emits or scatters radiation provides important information about the material's properties and composition. Many different forms of spectroscopies exist depending on the frequency range of the EMR used. Spectroscopy-based methods deliver fast, sensitive, low-cost and waste-free analysis with little-to-no sample preparation. Their application as “green” or environmentally friendly analytical methods has increased dramatically in recent years across health sciences, physics, chemistry and other disciplines.

Spectroscopy at the CFIA

The Canadian Food Inspection Agency (CFIA) Food Foreign Matter Analysis Unit at the Greater Toronto Area (GTA) laboratory uses 2 spectroscopic techniques for unknown material identification, food safety investigations and method development research related to food authenticity. These techniques are:

  • Fourier transform infrared (FTIR) and Raman spectroscopy and
  • Laser induced breakdown spectroscopy (LIBS)

Fourier transform infrared and Raman spectroscopy

Molecules can be identified by how they interact with infrared radiation. Fourier transform infrared (FTIR) and Raman spectroscopy are complementary technologies based on the absorption and scattering of the middle section of infrared radiation, respectively. Because the absorption of low-energy infrared light generates vibrational motion in chemical bonds of molecules, both methods are also known as vibrational spectroscopy. The methods allow scientists to capture molecular fingerprints from a variety of materials. Fingerprinting describes a molecule’s unique structure and makes it easier to compare similarities and differences between them.

Laser induced breakdown spectroscopy

Material can also be identified by how it cools after being vaporized. Laser induced breakdown spectroscopy (LIBS) is a type of emission spectroscopy that analyses plasma radiation. LIBS generates plasma by vaporizing a micrometer-sized portion of the sample surface at an extremely high temperature. This leads to the development of a short-lived, high-temperature local plasma akin to the boiling plasma seen on the sun's surface. Spectrophotometers gather the light released by cooling plasma and create a spectral fingerprint of the atoms and ions in the plasma. LIBS is regarded as one of the most practical and efficient ways to get a quick atomic fingerprint of gases, liquids and solids. LIBS has grown so much in popularity that it is currently one of the key instruments aboard the Mars rover, where it actively investigates the chemical composition of rocks and minerals on another planet.

Protecting our food with spectroscopic fingerprinting

The CFIA is always looking for ways to ensure food safety. Also known as non-targeted analysis, spectroscopic fingerprinting has proven to be useful in recent years for many food safety applications. This includes identifying unknown material, confirming food authenticity (for example, that cheap oil hasn’t been mixed into olive oil or that the fish species is what is on the label) and testing for food safety and quality. Spectroscopic fingerprinting provides a quick method for detecting any deviations or anomalies when compared to authentic samples. Unlike targeted approaches, which attempt to identify a single agent at a time, fingerprinting looks for unusual patterns in large amounts of spectrum data. To sense subtle differences in this large volume of data, the methodology uses refined multivariate data analysis tools that can quickly identify suspect samples for targeted analysis. Recent advances in data science and machine learning have greatly improved the use of multivariate data analysis techniques, as well as the development of interactive and intuitive tools for communicating complex data.

Using FTIR to combat food fraud in fruit juice

Fruit juices, including coconut water, are often targets of food fraud, where cheap fillers are added to maximize volume for profit. In a recent study, the CFIA used FTIR spectroscopy-based chemical fingerprinting to distinguish coconut water substituted with sugar solutions in line with recorded incidents. The molecular fingerprint spectra were acquired from samples that had been incrementally substituted with six different sugar solutions, including one that mimicked the natural sugar content of coconut water. The data was examined using a method known as principal component analysis (PCA). PCA is used to simplify pattern recognition in complex data by extracting only the most significant properties, which are then projected and visualized as a simple x-y plot. PCA clearly separated the data based on the type and level of substituted sugars. This method of identifying additives and substitutes could pose a challenge to even the most skilled fraudster.

Tracking down the source of glass in food with LIBS-based fingerprinting

In the food industry, glass fragments in packaged foods are a significant food safety risk. When glass is found in food, the CFIA begins an investigation to identify the glass and determine where the glass came from--packaging, the environment or other possible sources. This important information is needed to develop and apply preventative measures to protect consumers.

Although molten silicon dioxide is the base material used to make glass, different types of glass have unique physical characteristics based on their specific applications. The CFIA has recently shown how LIBS-based elemental fingerprinting can assist in food safety investigations by distinguishing glass types based on composition. LIBS-based atomic spectra were acquired from a range of glass samples used for various purposes, including food jars, windows, display glass and glass used in lighting. The data was then subjected to multivariate data analysis and clustering techniques to visualize differences between the glass types.

Analysis of these samples showed that glass used in food packaging and flat glass such as windows (also known as soda-lime glass) have a similar composition. On the other hand, LIBS easily identified other glass samples that have unique properties: laboratory beakers, UV-lights, electronic displays and halogen lamps. Glass is made with different compositions to meet the specific physical requirements of how and where it will be used. During a food safety inquiry related to glass found in food, this LIBS-assisted speciation of glass in the environment can support efforts to track down the source of glass fragments. This is just one example of several potential applications for LIBS in food safety and quality assurance.

Harnessing the power of spectroscopy is just one of the ways the CFIA is committed to safeguarding food and its properties. Check out the links provided below for more information on food safety and food fraud.

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