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Figure 1: Chromatogram of nine compounds found in alcoholic beverages.

Gas chromatography (GC) is a core technique for separating and analyzing compounds, and is commonly used by scientists and laboratory managers across multiple industries. The principle of GC was first conceived in 1941 by A.J.P Martin and RLM Synge. The process involves adsorption of gases and low boiling hydrocarbons. In industrial processes, chromatography is used to purify chemicals, test for trace amounts of substances, separate chiral compounds and test products for quality control.

In beer analysis and brewing, alcoholic beverages are uniquely characterized by complex mixes of compounds, thus creating the individual aromas and flavors that consumers enjoy. While most added compounds augment the desired aroma and flavor aspects of a beverage, trace components can contribute off-flavors and odors.

Therefore, gas chromatography is a powerful tool in the analysis of alcoholic beverage products. Typically, minimal sample preparation is required, since the samples are in the liquid state in an alcohol or alcohol/water matrix. The flavor compounds have a tendency to be volatile in nature, which fulfils one of the main requirements of GC.  Additionally, the ability to automate the analysis makes GC a very practical tool in quality control.

GC is used widely in the brewing industry, particularly since the craft brewing sector has been experiencing significant growth thanks to soaring consumer demand around the world. There is a particular focus on higher quality products in Western Europe.
Ethyl carbamate testing

Ethyl carbamate (Urethane C2H5OCONH2) is a naturally occurring ester that is common in many fermented foods and alcoholic beverages as it can be generated during the fermentation/distillation process. Ethyl carbamate has been detected in various alcoholic beverages that have been fermented, as well as other products including bread, yogurt, cheese, soy sauce and vinegar. The ester can be formed from various substances derived from food and beverages, including hydrogen cyanide, urea, citrulline, and other N-carbamyl compounds. Primary production of ethyl carbamate arises when cyanate reacts with ethanol to form the carbamate ester.

Ethyl carbamate has  been shown to cause cancer when injected into animals and is considered to be probably carcinogenic in man. This resulted in the compound being re-classified in 2007 as a Group 2A genotoxic carcinogen by the IARC (International Agency for Research on Cancer), and it is now regulated in many countries.

Levels found within food are thought to have comparably little effect of increasing chances of developing cancer, although, when partnered with distilled alcoholic beverage consumption, the risk is predicted to significantly increase. There are currently no standardized limits for maximum levels of ethyl carbamate in the European Union (EU). Recommended maximum levels in other countries for ethyl carbamate in alcoholic beverages are contained in Table 1. EFSA (European Food Safety Authority) noted that these levels need to be monitored and reduced by manufacturers. They also suggest steps to minimize formation of ethyl carbamate, such as minimizing exposure to heat and light and limiting storage time of the finished product.

Alcohol profiling
The volatile component profiles of alcoholic beverage products consist of a wide range of compounds, including acids, alcohols, aldehydes and other trace-level flavor compounds. Many compounds contribute to the aromas and flavors experienced by the consumer. The volatile compounds interact with receptors in the nasal passages creating the aroma sensation. Flavor, however, is experienced as a combination of aroma and taste.  The unique sensory properties of different types and brands of alcoholic beverage products often are due to minor differences among the volatile components present.

In addition to alcohols and flavor compounds, trace components and impurities, such as sulfur gases, occasionally are present, and might lead to off-odors or flavors in the product.

These compounds can be generated by contaminants in raw materials used in the beverage, migration into the beverage from process equipment or packaging materials, as well as degradation of naturally occurring flavor compounds due to oxidation or exposure to light or heat. Changes in the relative concentrations of these compounds can result in an undesirable change in the flavor of the beverage. Therefore, accurately profiling the compounds contributing to flavor and aroma, which can span a wide range of volatility, is essential in ensuring product quality.

The compounds were analyzed using an Ellutia 200 Series GC with a flame ionization detector and an EL-FFAP column. To ensure an accurate injection a liquid sampler was used. The liquid sampler produces a lower percentage of thermal discrimination between volatile and lesser volatile molecules in the sample injection when compared to the headspace autosampler. The findings are shown in Figure 1.
As the ethanol content can be over 40 percent (v/v) in some beverages, trace compounds would be difficult to analyze simultaneously with this level of ethanol present. However, adding a timed event to switch between ranges during the analysis would facilitate this. Trace compounds could be 1,000 times less concentrated than the ethanol. Therefore, a range switch during the appearance of ethanol would bring the peak within a practical scale to allow for the trace compounds to be analyzed in one run.

Analysis of alcoholic beverage products is crucial as the volatile component profiles of products consist of a wide range of compounds. Thus, gas chromatography is an extremely powerful tool for analysis. Testing for the presence of ethyl carbamate in food and distilled alcoholic beverage products are thought to help reduce the risk of developing cancer. Ethyl carbamate is genotoxic and a multisite carcinogen in animals and probably carcinogenic to humans. This analysis helps companies produce more desirable products and ensure product quality, which is imperative for success in the food and drink industry. 

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