Comparison of three methods for accurate quantification of hydrogen sulfide during fermentation

Two analytical approaches for the rapid measurement of hydrogen sulfide (H2S) have been compared to a reference method for their potential application as a rapid procedure for the quantification of H2S formed during alcoholic fermentations. In one case, silver nitrate, lead acetate, and mercuric chloride selective detector tubes for the analysis of H2S in air were investigated. In the other case, a commercially available kit for the diagnosis of nitrogen starvation in wine fermentations, which is based on the detection of H2S, was investigated. Both methods exhibited excellent linearity of response, but the mercuric chloride tube was found to suffer from interferences due to the concomitant presence of mercaptans, which resulted in erroneous H2S quantification. A comparative study between the two methods studied and the cadmium hydroxide/methylene blue reference method commonly used to monitor H2S indicate that the two new methods displayed better recoveries at low H2S concentrations, besides being more rapid and economical. The two new methods were successfully used to quantify production of H2S in different grape juice fermentations. The suitability of each method for the study of specific aspects of H2S production during fermentation is discussed.