Contaminants in beverages in the form of chemicals, particulates, or microorganisms may be naturally sourced from the environment or through anthropogenic activities. These include chemicals like pesticides, heavy metals, amines, inks, perfluorinated compounds, bisphenols, etc.; foreign bodies like glass, wood, and metal fragments; and microbes like viruses, bacteria, protozoa, and fungi.
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Without strict quality control measures and contaminant analysis, these hazardous chemicals pose a severe threat to human health.1 To combat these threats, the research community has developed various beverage contaminant analysis techniques to provide high-quality products to consumers.
Sample Preparation Techniques
A pre-concentration (or preparation) stage is essential in beverage analysis to increase analyte concentration and eliminate matrix interferences. This improves the detection limit, accuracy, and sensitivity of the analysis technique. Some extraction methods used for heavy metals are co-precipitation, liquid-liquid extraction, ultrasonic-assisted microextraction, and solid-phase extraction.1 It is noteworthy that the extraction process may lead to loss of analyte or change its character. Thus, detection techniques with minimum preparatory steps are always preferred.3
In case of detection of phthalates from packaging materials, pre-treatment steps include cutting into small pieces and centrifugation with acetone or n-hexane to extract the analytes from the supernatant.1 A filtration step before analysis can further simplify sample preparation if the analyte is of sufficient volatility and the matrix does not contain major interferences; for example, analysis of methanol in liquors.2
Analytical Techniques for Contaminant Detection
Chromatographic methods are mostly used for the separation of individual compounds from beverages. They offer wide applicability, high resolution, and selectivity.1,2 Gas chromatography (GC) and high-performance liquid chromatography (HPLC) are employed for detecting amines, pesticides, inks, alcohols, and phthalates in beverages. These are efficient and rapid methods with low reagents consumption.1
Spectroscopic techniques like ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) are employed to analyze nontargeted contaminants. They are nondestructive methods and help detect contaminants that are missed by targeted analysis. However, the data obtained is qualitative and requires further characterization using additional methods like mass spectroscopy.2
Mass spectroscopy is a powerful tool for detecting contaminants using the mass-to-charge ratio of ions generated from a sample.3 Liquid chromatography is often coupled with mass spectroscopy (LC-MS) to analyze mycotoxins in alcoholic drinks, migration contaminants, and colorants. Inductively coupled plasma is used with mass spectroscopy (ICP-MS) or optical mass spectroscopy to detect the presence of trace metal contaminants like arsenic, lead, and cadmium in beverages.2 Though the technique has high operation and maintenance costs, it is still commonly used as it can identify many elements in a single run with a high detection limit.1
Immunoassays such as enzyme-linked immunosorbent assay (ELISA) are used to detect biogenic amines (BAs) in beverages. Small quantities of BAs are present in raw materials for beverages, but fermentation can increase their concentration to harmful levels. ELISA allows for their rapid and easy detection without interference from other structurally similar compounds.1
Rapid Screening Methods
Electrochemical biosensors with different detection matrices and modified electrodes are used for rapid and easy detection of amines in beverages. They are most sensitive for the detection of bisphenol A and do not require any pre-treatment steps. Most of these biosensors are amperometric (based on current analysis), but alternatively, potentiometric sensors with molecularly printed nanoparticles have also been developed.1
The presence of microbes in beverages poses a severe threat to human health. Detection and identification of such microorganisms at the DNA level is done using polymerase chain reaction (PCR) methods. It involves the amplification of a specific segment of DNA in a sample to an easily identifiable extent.5
Emerging Technologies
High-resolution nuclear magnetic resonance (NMR) is routinely used in wine and beer screening. It can reveal both the molecular and chemical composition of liquid matrices.3 1D mode of NMR has limited quantification ability, but 2D NMR is successfully used to precisely identify contaminants in beverages.2
Raman spectroscopy reveals fundamental chemical bonding in the samples.3 It is used to identify non-intentionally added substances in beverages that mainly come from packaging materials or specific processing conditions.1 The spectroscopic techniques offer the advantages of easy sample preparation and precise quantification but are low in sensitivity. Thus, they are not suitable for complex mixtures.2
Data Analysis and Interpretation
Statistical processing of the data recorded from various instrumental techniques is required to conclude contaminant concentrations. The data is often complex and contains redundant information along with useful information in the form of intensities, band positions, shapes, and peaks. The processing of data obtained from each method is specific to the instrument characteristics. This has been resolved with the development of chemometrics and suitable computer algorithms. For instance, well-formulated chemometric algorithms and databases for Raman spectra help in deriving quantitative and qualitative conclusions.3
Regulatory Compliance and Quality Assurance
Regulatory compliance and quality assurance are imperative for beverage producers, policymakers, authorities, and food scientists. It ensures safety and health for consumers as well as improves nutritional value. Apart from beverages, contaminants may be present in their containers, which eventually migrate into the food chain.
Despite strict bans, contaminants can form in beverages unintentionally during processing, packaging, and distribution. It is not only important to eliminate contaminants from beverages, but early detection is also required to prevent their spread after people ingest them.1
Case Studies and Applications
A recent review article in TrAC Trends in Analytical Chemistry presented the application of ultrasound to extract organic contaminants from liquid samples using green solvents. Ultrasound-assisted extraction is an easy process and applicable to various matrices. The review highlights using environmentally friendly solvents such as deep eutectic solvents and novel sorbents like magnetic nanoparticles in beverage analysis.4
Another recent study in Food Additives & Contaminants: Part A demonstrated the utilization of novel Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR/Cas9)-based biosensing for identifying DNA barcodes of poultry and livestock in processed food samples. It is a simple and flexible site-specific DNA editing tool that can be used in conjugation with well-established PCR methods for rapid beverage contaminant analysis.5
Future Trends in Beverage Contaminant Analysis
Electronic nose (e-nose) and electronic tongue (e-tongue) are the latest trends expected to be more popular for beverage contaminant analysis in the future. This is because of their ease of use, rapid analysis, environmentally friendly, simultaneous multiple analysis, and little or no preparatory steps. They comprise multisensory systems and work on pattern recognition through advanced mathematical data processing.3
In conclusion, combining multiple sensing techniques and single-step algorithms using artificial intelligence techniques will further improve contaminant analysis in beverages.
Sources:
1. Pelegrín, C. J., Flores, Y., Jiménez, A., & Garrigós, M. C. (2020). Recent Trends in the Analysis of Chemical Contaminants in Beverages. Beverages, 6(2), 32. https://doi.org/10.3390/beverages6020032
2. He, N. X., & Bayen, S. (2020). An overview of chemical contaminants and other undesirable chemicals in alcoholic beverages and strategies for analysis. Comprehensive Reviews in Food Science and Food Safety, 19(6), 3916–3950. https://doi.org/10.1111/1541-4337.12649
3. Arslan, M., et al. (2021). Recent trends in quality control, discrimination and authentication of alcoholic beverages using nondestructive instrumental techniques. Trends in Food Science & Technology, 107, 80-113. https://doi.org/10.1016/j.tifs.2020.11.021
4. Rosa Ana Pérez, & Albero, B. (2023). Ultrasound-assisted extraction methods for the determination of organic contaminants in solid and liquid samples. Trends in Analytical Chemistry, 166, 117204–117204. https://doi.org/10.1016/j.trac.2023.117204
5. Sultana, S., Azrina Azlan, Mohd, Nor Ainy Mahyudin, & Amaladoss Anburaj. (2024). A review of CRISPR-Cas and PCR-based methods for the detection of animal species in the food chain-current challenges and future prospects. Food Additives & Contaminants: Part A, 1–15. https://doi.org/10.1080/19440049.2024.2304577
Further Reading