Better and Safer Food Through Spectroscopy

Food quality and safety is a concern for us all. What you might not know is that spectroscopy is beginning to play an important role in making sure that food meets quality and safety standards.

pH, polarity, temperature, pressure, and viscosity affect food quality and safety. And all these characteristics can be measured with spectroscopy.

Since quality and safety relate to these properties, coming up with fast and simple ways of measuring these is important. One researcher uses optical spectroscopy to identify molecules that have characteristics that can reveal the safety and quality markers he seeks.

“We identify naturally occurring fluorescent molecules in food, that is, edible fluorescent molecules,” said Richard Ludescher, Ph.D., and a professor of food science with expertise in biophysics, protein at Rutgers University in New Jersey. “We are identifying which of those molecules have a fluorescent property that can tell us about a physical or chemical state, which in turn can tell us about that property and safety.”

Ludescher focuses on naturally occurring molecules in the food we eat that fluoresce. These molecules are sensitive under optical spectroscopy to the physical and chemical properties that are relevant to food science.

“My research is based on when you have fluorescent molecules in solution, their fluorescence properties are often influenced by particular properties of the solution,” he said. “It tells you if they are sensitive to the pH, polarity, temperature, pressure or viscosity. Then you now have a sensor, a chemical that is sensitive to that property. You can now measure pH by a signal from that molecule.”

pH is an important property for food. Manufacturers have to be careful how it changes in meat, for example, since the wrong pH can create undesirable products or properties. Ultimate pH, the pH measured 24 hours after slaughter, can determine the meat’s tenderness, according to studies published by the National Institutes of Health.

 “The food and agriculture industries face many challenges in meeting both FDA regulations and customer expectation,” according to a report by photonics.com. “The Food Safety Modernization Act, passed in late 2010, introduced new quality standards to the U.S. food supply with the intent of preventing a health crisis, rather than responding after people become sick. It includes the establishment of science-based standards for preventive quality controls in food facilities, the production and harvesting of fruits and vegetables, and mandatory FDA inspections to ensure compliance. The regulations set stringent guidelines to help detect defective or potentially hazardous materials in products before they are shipped to consumers.”

Every food and agriculture enterprise, including importers, must have preventive measures in place to ensure their products are compliant with established regulations.

Most quality-testing solutions for usually require the destruction of some of the product for lab tests. And that testing can be a lengthy process. If the testing is on-site, the results may take a few hours. Off-site testing could take several days.

Chromatography and atomic absorption spectroscopy have historically been the common analytical techniques in the agriculture industry for a wide variety of analyses. Unfortunately, each method takes significant sample preparation and long delays to get the results.

Fluorescence spectroscopy offers another opportunity.

“Spectroscopic methods measure the wavelength dependence of the interaction of light with matter,” according to the photonics.com report. “This interaction could be the amount of light absorbed by a sample, or the diffuse reflection of light off a sample, making spectroscopy a valuable tool for measuring a wide variety of liquids, solids, and gases. By incorporating certain types of measurement heads and probes, it is possible to measure samples in-line without destroying any of the product and delaying the process.”

Each compound has a unique fingerprint or molecular composition and arrangement of atoms. Each chemical, therefore, will interact with light at different wavelengths, making identification of these molecules in a non-destructive way.

The dairy industry uses NIR (near infrared) spectroscopy to monitor sugar, fat and water content of products.

The technology goes beyond quality control. A sample may be contaminated or, through spectroscopy, shows certain deviations from a pre-existing standard. As a result, a warning signal can be sent that something is wrong.

Inline testing of food products, while in production, is the preferred method to control for these differences and alert scientists to problems with the materials.

Food scientists also develop new foods. Each one has problems that must be solved. Fluorescence spectroscopy plays a role. The challenge is figuring out how to manufacture the food item and keep it safe.

Wine production is garnering the attention of fluorescence spectroscopy. Most wineries have multiple brands and growing fields. Winemakers need to monitor these fruits for the phenolic content in the grape that will give it the desired color, flavor and mouthfeel. Fluorescence spectroscopy is a cheaper and faster way to characterize the phenolic content in grapes and wine than historically conventional methods.

HORIBA Scientific recently patented an instrument called the Aqualog®, which makes this process faster and less costly. With the Aqualog, you can collect the entire composition of all the colored and phenolic compounds. The acquisition time is roughly 30 seconds. In less than a minute, operators can fully automate the analysis in terms of the phenolic identity and concentration.

Fluorescence spectroscopy is also supplementing olive oil production.

Scientists believe phenolic compounds, like those found in olive oil, can contribute to a lower rate of coronary heart disease and prostate and colon cancers. Olive oil is a source of at least 30 phenolic compounds.

Olive oils have unique fluorescent fingerprints. In fresh, extra-virgin olive oil, emissions originate from phenols, tocopherols and chlorophylls. During oil deterioration, new fluorescence appears from oxidation products. Fluorescence spectroscopy can distinguish these characteristics during manufacturing and while the product sits on the shelves of supermarkets.

Researchers, found they might use fluorescence in olive oil analysis for screening fluorescent components during storage, to monitor extra-virgin olive oil deterioration. Moreover, other studies showed that fluorescence, as well as other spectroscopic techniques including NIR (near infrared spectroscopy) and MIR (Mid-infrared spectroscopy) might be used to quantify the adulteration of extra-virgin olive oils with refined and deodorized oil.

Food safety scientists use inductively coupled plasma - optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) to measure heavy metals in foods that may cause cancer, neurological issues and cardiovascular disease when consumed.

Energy dispersive X-ray fluorescence (EDXRF) spectroscopy helps food labs optimize production. Scientists use the technology to measure nutrients and fortificants, screen for contaminants and incidental adulterants, and identify foreign body contaminants during food production and packaging. It also provides essential information about concentrations of minerals and toxic metals. EDXRF is suited for researchers running biofortification programs using micronutrients.

Raman spectroscopy can provide detailed molecular vibrational information for the target analyte in food samples in a short amount of time.  Surface-enhanced Raman spectroscopy (SERS) can help detect chemical and bacterial contaminants in foods and determine the composition and qualities of foods.