Development of a method to measure hydrogen sulfide in wine fermentation.

A hydrogen sulfide (H2S) detecting tube was developed for the quantitative determination of H2S produced by yeast during laboratory scale wine fermentations. The detecting tube consisted of a small transparent plastic tube packed with an H2S-sensitive color-indicating medium. The packed medium changed color, with the color change progressing upward from the bottom of the tube, upon exposure to H2S produced by yeast during fermentation. A calibration study using a standard H2S gas showed that the length of the portion that darkened was directly related to the quantity of H2S (microg) with a high correlation coefficient (r2=0.9997). The reproducibility of the H2S detecting tubes was determined with five repetitive measurements using a standard H2S solution [5.6 microg/200 ml (28 ppb)], which resulted in a coefficient of variation of 3.6% at this level of H2S. With the sulfide detecting tubes, the production of H2S was continuously monitored and quantified from laboratory scale wine fermentations with different yeast strains and with the addition of different levels of elemental sulfur to the grape juice. This sulfide detecting tube technology may allow winemakers to quantitatively measure H2S produced under different fermentation conditions, which will eventually lead winemakers to better understand the specific factors and conditions for the excessive production of H2S during wine fermentation in a large production scale.