Alcohol in Beverages

Alcohol measurements tend to be either time consuming (gas chromatography) or inaccurate (ebulliometer). Infrared offers a quick and accurate method of analysis. Mid infrared (Mid-IR) offers distinct absorbance bands without the overtones found in the NIR range. Mid-IR also allow for the use of an ATR (Attenuated Total Reflection) sample stage as shown in the picture on the left. The exposed crystal makes sample presentation and cleaning quick and easy. Another consideration in small winery laboratories is size. The InfraSpec VFA-IR Spectrometer is a compact, rugged and portable solution for alcohol measurement in beverages at a fraction of the cost of an FTIR.

The InfraSpec VFA-IR Spectrometer is a new concept in infrared instrumentation. It utilizes a patented design consisting of an ATR sample plate with an electronically modulated source on one end and a linear variable filter (LVF) and a 128 pixel detector array on the other. The result is an infrared analyzer that, unlike an FTIR spectrometer, has no moving parts and an insignificant optical air path. This makes for a portable, rugged analyzer suitable for use in a field environment. The peak for ethanol is located at 9.6 μm (1042 cm-1), therefore either a 7-14 μm (1430-710 cm-1) or 5.4-10.8 μm (1850-925 cm-1) filter is used.

Results for a Mid-IR analysis of alcohol in beverages is comparable to other methods. The range is 2-95% with an accuracy of +0.1% v/v alcohol. Less than 1 ml is needed for analysis and a result is obtained within one minute.

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