Propylene Glycol (PG) in Alcoholic Beverages

Donna Kinder, Ellutia

Propylene glycol (PG) can be used as a food additive and is widely accepted as safe for human consumption at low levels. The WHO (World Health Organization) have set the maximum permissible daily intake of propylene glycol as a food additive at 25 mg/kg bodyweight. PG comes in several grades with food grade PG, often used in the external chilling systems of breweries, as well as ice cream production, amongst others. The brewing industry standard requires that PG used within the chilling system must be food grade at a concentration no less than 25% by volume. This mix of PG and water enables the brewer to achieving cooling temperatures between -2.7 °C and -3.3 °C (25–27 °F). Contamination of beer can occur as a result of a damaged vessel wall or pipework, resulting in PG from the coolant jacket entering the beer stream. In Europe, authorities are very cautious about acceptable uses of PG within the cosmetics and food industry and is limited to mostly non‑food applications. Those that are permitted are very limited and it is not currently approved to add to beer. There is, however, an EU 1 g/kg limit in food (additive number E1520).

Analysis

An Ellutia 200 Series gas chromatograph with a flame ionization detector (FID) was used for the analysis. The only sample preparation required was for the sample of beer degassed. This can be achieved by sonicating the sample or by repeatedly pouring the sample between two beakers. Once degassed the sample can be directly injected into the GC.

Figure 1: A chromatogram of a 0.5 µL injection of 700 ppm solutionof propylene glycol in a generic lager, with a retention time of approximately 6.7 min. This chromatogram shows good peak shapes and indicates little interference from the matrix components.

Figure 2: Calibration set 250–10,000 ppm propylene glycol in 5% ethanol solution, R2 = 0.996. Good lineaity and correlation is observed.

GC Conditions

Injector temperature (°C): 230

Carrier gas type: Hydrogen

Split flow (mL/min): 30

Column flow (mL/min): 3.0 simulated constant flow

Injection volume (µL): 0.5

Column type: 15 m × 0.25 mm, 0.25-µm df EL-WAX

Column Temperature Program:

Initial temperature (°C)/hold time (min): 50/0

Temperature ramp (°C/min): 10

Final column temperature (°C)/hold time (min): 200/0

Detector: FID

Detector temperature (°C): 240

Figure 3: Comparison of two shop purchased lagers with a 250 ppm PG in 5% ethanol solution. Sample 1 - Green, Sample 2 - Blue, and 250 ppm PG in 5% ethanol solution - Red. From the peak areas of each sample, the concentration of PG has been calculated and is shown in the inserted table.

Conclusion

Analysis of propylene glycol content in lager can be achieved using an Ellutia 200 Series gas chromatograph with an FID. Initial testing has indicated that there are low PG concentrations in commercially available lagers. Sources of PG found in these samples cannot be established off-site and any unintentional contamination of these samples would need to be investigated. Intentional PG content should be monitored and levels should be kept within permissible levels. As daily exposure levels are subjective to an individual’s bodyweight and average consumption of lager, and other potential food sources of PG, it would seem prudent to reduce the levels of PG that an individual could be exposed to.

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