Advanced Chemical Fingerprinting of Food and Beverages using LC-MS

Recent studies highlight the increasing importance of LC-MS in quality control and safety

Mass spectrometry has become a central technology in the food and beverage testing industries. Screening, contaminants testing, quality control, and other safety measures have advanced significantly at the hands of MS-based testing workflows.

MS has been a key tool for exploratory research and emerging quality and safety applications as well.  Two recent research studies using LC-MS — focused on the analysis of beer and e-cigarettes — demonstrate the power of the technology for applications of importance and emerging concern.

Chemical diversity in beer

With the growing number of beer varieties across the globe, there is an increasing need for quality control and authenticity testing. Beers are produced in batches of different volumes and in various locations, make adherence to strict quality control challenging. In addition, food fraud is an ever-present threat, partly due to the lack of definitive means for testing complex food and beverage samples. These issues are complicated by the fact that, in the case of beer and wine, ingredients are converted by yeast into thousands of metabolites — together forming the taste, uniqueness, and of course the complexity of the libations.

Researchers from Munich, Germany recently employed advanced LC-MS technologies to explore the vast chemical complexity of beer, as reported in Frontiers in Chemistry. In their work, the investigators used two powerful techniques to analyze 467 beers of different varieties and countries of origin. Direct infusion Fourier transfer ion cyclotron resonance mass spectrometry (DI-FTIR MS) was used for direct sampling of beer extracts, harnessing the ultra-high mass resolution and accuracy of the platform for identification of intact compounds and metabolites. Ultra-high performance liquid chromatography mass spectrometry (UPLC-MS) was then used to analyze a 100-sample subset of the results. DI-FTIR MS directly revealed the chemical diversity across all beers, and UPLC-MS determined the exact molecular structures of each compound and isomer from each sample.

The researchers then placed the metabolites in ‘chemical space’ in relation with one another, linked through a single reaction — addition of a methoxy, hydroxyl, sugar group, etc. to the molecular backbone. The authors theorized this metabolite network could be used to trace the origin of the starting materials specific to each beer. They state the profiling method is rapid and should be very powerful for quality control and testing. Interestingly, the investigators found approximately 7,700 ions with unique masses and formulas, 80% of which aren’t yet described in chemical databases. All told, there may be tens of thousands of unique metabolites identified, awaiting further characterization and potential use in fingerprinting.

Unique e-Cigarette chemicals

There is substantial controversy around vaping e-Cigarettes and whether users are exposed to more or less damaging chemicals as compared to regular cigarettes. In a first of its kind study that subjected vaping liquids and aerosols to advanced chemical fingerprinting, researchers found there are significant differences between the two that may have significant health implications. The study was recently published in ACS ASAP.

Prior work had looked for the presence of known hazardous chemicals in e-Cigarettes that had previously been found in normal cigarettes. In the current work, investigators employed non-targeted analysis to explore the full range of chemicals in both vaping liquid and aerosols. LC-MS/MS analysis was performed on four popular e-Cigarette brands: one disposable, two pod, and one tank/mod types. Aerosols were collected by condensation methods and analyzed alongside liquid samples. Full-scan Orbitrap MS/MS was run in both positive and negative ion modes. Compound Discoverer software was used to detect known (and unknown) compounds, based on comparisons with known quality control compound standards.

The researchers found nearly 2,000 chemicals, the majority of which are uncharacterized. Of those that were identified, several had never before been observed in e-Cigarettes. Three industrial chemicals (including tributylphosphine oxide), a pesticide, and several flavor compounds, potentially harmful for inhalation, were found in the mix. Also included was the stimulant caffeine. Beyond fingerprinting, the LC-MS technique may prove useful for identifying whether combustion of vaping liquids and aerosol compounds gives rise to chemical derivatives. Understanding the nature of these compounds will explain with further detail the potential health effects stemming from the combustion process of e-Cigarettes.

Outlook

Advanced mass spectrometry techniques are bringing much to the table in terms of safety and quality control of our food stuffs. Exploratory fingerprinting techniques are advancing our understanding of the chemical complexity, and health ramifications, of the products we choose to consume – food for thought…

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