Search: acetaldehyde

The gas chromatography headspace method is used to determine the higher alcohols and esters present in beer, i.e., the volatile compounds are transferred from the headspace in the sample vial into the GC system for analysis. The following substances are measured in this analysis:

Acetaldehyde

Propanol-1

Ethyl acetate

2-Methylpropanol

3-Methylbutanol

2-Methylbutanol

2-Methylpropylacetate

Butyric acid ethyl ester

3-Methylbutyl acetate

2-Methylbutyl acetate

Hexanoic acid ethyl ester

Volatile compounds in beer are concentrated through distillation and the distillate is quantitatively determined by direct injection into a gas chromatograph. The linearity of the detector and the determination of the concentrations of analytes in the sample are achieved by using multiple concentration levels within the relevant range and through evaluation of the relative area under the peaks.

This method is suitable for beers exhibiting all ranges of original gravity and alcohol concentrations.

Acetaldehyde is formed during the production of polyethylene terephthalate (PET) and is sealed into the wall of the bottles, but it is possible for the acetaldehyde to later migrate out and into the product. While low concentrations of acetaldehyde, on the order of μg/l, can have a negative influence on the quality of the product, this does not pose a health risk for consumers. Acetaldehyde is a volatile compound with a boiling point of 21 °C and is characterized by an intensely sweet, fruity aroma which is described as green apple. The olfactory sensory threshold of acetaldehyde in water ranges from 7.9 and 120 μg/. Experienced sensory panel members can detect acetaldehyde at levels between 10 and 20 μg/l. For this reason, the Genossenschaft Deutscher Mineralbrunnen (GDB) in Germany suggests a maximum value of 10 μg/l, because there is no effect on the flavor of the product at concentrations below this level. Therefore, one assumes that no perceptible effect on quality at concentrations below this reference value will be apparent. 

The migration rate for acetaldehyde is dependent on the initial concentration of the compound in the PET material, the temperature and duration of storage, as well as on the weight and geometry of the bottle. A greater surface area to volume ratio also results in a higher migration rate. The migration of acetaldehyde during the production of PET bottles can be minimized through the addition of a scavenger, such as anthranilic acid amide. However, this is often not utilized in the production of disposable bottles for economic reasons. CO₂ content and exposure to light also impact acetaldehyde concentrations.

Higher alcohols and esters in beer are determined by gas chromatography using the headspace method, e.g., the volatile compounds are transferred from the gas space in the sample vial to the GC system for analysis. The method is suitable for beer brewed to any original gravity or to any alcohol content.