Undesirable 'off' flavors in alcoholic drinks are the result of the generation of hydrogen sulfide (H2S) during the conversion of simple sugars into alcohol by the yeast in the fermentation process. In fact hydrogen sulfide at low levels is desirable, as it imparts defining flavor characteristics to the beer at lower concentrations.
Nevertheless, high levels of hydrogen sulfide result in an off-putting rotten egg smell to alcoholic drinks and 'skunky' odor in bad beer is a result of the interaction between hydrogen sulfide with the hops during the brewing process. Excess hydrogen sulfide can be a sign of improper oxygen levels, microbial infection, unhealthy yeast during fermentation, or many other root causes.
Testing of Dissolved Hydrogen Sulfide Concentration
Considering the volatility of hydrogen sulfide (boiling point -60°C), testing the headspace over the liquid is an efficient approach of determining the concentration of dissolved hydrogen sulfide. Under well controlled accumulation time and temperature, the concentration of hydrogen sulfide in the headspace varies in proportion to the concentration of dissolved hydrogen sulfide in the sample.
Although brewers monitor the concentration of hydrogen sulfide during production using sophisticated sensors in their fermentation tanks, bad beer can sometimes make it into the bottle.
Solution from Arizona Instrument
The Jerome® J605 Hydrogen Sulfide Analyzer offered by Arizona Instrument is an ideal device capable of determining hydrogen sulfide concentration in bottled beer down to 5ppb within 7 minutes. The analyzer does not require any hazardous material and has a linear response over the range analyzed with regard to concentration.
The test begins by connecting an Erlenmeyer vacuum flask to a Jerome® J605 Hydrogen Sulfide Analyzer using tygon or other suitably sized inert tubing, followed by filling the Erlenmeyer flask with a full bottle of beer and allowing to stir for 5min. The apparatus setup for determining hydrogen sulfide concentration in beer using the Jerome® J605 Hydrogen Sulfide Analyzer is shown in Figure 1.
Figure 1. Apparatus Setup for determination of H2S in beer by Jerome®J605.
The Jerome® J605 Hydrogen Sulfide Analyzer is positioned to sample the headspace over the beer every 2 minutes. Sampling is performed for 30min and the results are summarized in Table 1:
Table 1. Concentrations of Hydrogen Sulfide in PPM for Three Different Alcoholic Beverages.
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From the results, it can be seen that the hydrogen sulfide concentration is very high for Heineken, as expected because it has the strongest flavor among the analyzed beverages. The wine has the lowest level of hydrogen sulfide as anticipated owing to the fact that wine obtains its flavor from other sources.
About Arizona Instrument
Initially known as the Quintel Corporation, Arizona Instrument LLC was founded in 1981 by a group of engineers breaking away from The Motorola Corporation who were dedicated to the idea of providing precision moisture analysis instruments that were accurate, reliable, and easy to use.
The first instrument released was the MA Moisture Analyzer, but the company quickly expanded its Computrac® moisture analysis line and became an accepted leader in moisture analysis, setting a standard that has been adopted by many Fortune 500 companies. Today the Computrac® line is comprised of three technologies: rapid loss-on-drying, high temperature loss-on-ignition, and moisture specific analysis using polymer capacitance sensor, GREEN alternative to Karl Fischer.
This information has been sourced, reviewed and adapted from materials provided by Arizona Instrument.
For more information on this source, please visit Arizona Instrument.