New Insights into the Origin of Volatile Sulfur Compounds during Wine Fermentation and Their Evolution during Aging
, Carole Camarasa and Audrey Bloem *Round 1
Reviewer 1 Report
The work is sound and I do not see issues in publication in present form.
However I am unsure how the author can be sure of what stated in the sentence on line 190-192, in particular on the part "and is not chemically converted further but consumed by yeasts".
Legend of figure 2 report an error:
"w/o cells 24 h: incubation in absence of cells during 234 209 h. Experiments were conducted in triplicate." should be "w/o cell EF".
Also, I do not think the "EF" acronym is explained anywhere in the paper.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript describes an extensive investigation on the volatile sulfur compounds (VSCs) production during winemaking and the Yeast metabolism contribution to their production. The results are of interest because these compounds are responsible for unpleasant aromas when present above a certain threshold in wines.
I noticed three main points that must be discussed before publication to improve the manuscript:
1 the choice of the Viognier grape,which is white, the authors did not comment the fact that red and white wines are different in composition and in aromas.
2 the laboratory conditions are extremely useful but that accelerated wine ageingor high temperatures (50°C) [cited from literature, line 441] are not reflecting the winemaking or natural wine aging procedures.
3 the cerevisiae strains used in the winemaking processes can be highly different in terms of metabolism, thus a sentence on the variability of the strains can be useful for the reader.
In other terms, the authors should add a comment explaining that their results are based on the use of a specific wine (or a synthetic wine), a specific yeast strain, in laboratory conditions. Of course, this is necessary to standardize the experiments, but nevertheless, the winemaking processes are more complex and depends on many factors.
Minor comments:
line 44 hydrogen sulfide, please add (H2S)
line 53, 431, 498 and 516 “ …” were used several time in the text. Please explain.
line 54 a citation on the mechanism of H2S formation is lacking
line 108 specify why this concentration was used (400 μM of a specific VSC) and why different concentrations were not tested? Preliminary experiments were performed? Data from literature? Previous studies of the authors? Is this concentration added to obtain an excess of the compound? Please specify.
line 147 the temperature is missing
line 124 specify that the anoxic environment is required to mimic the wine aging in the bottle.
Line 164 the Discussion is missing, did the authors intended Results and Discussion?
Line 206 what are a,b,c,d? they are missing in the legend
Line 206 incubation, specify in presence or absence of cells
Line 182 it would be better to mention here that some compounds were never detected.
Line 188 ETA and other compounds, it would be nice to add to the names the corresponding letter i.e. (a) in Figure 2 to help the reader to follow the results.
Line 311 the word evolution in this and other legends could be replaced by variation or by another term?
Line 311 add (a) and (b) to describe the upper and lower part of the figure in the legend. The same comment for figure 4.
Line 436 SM200 is not present in M&M
Line 534 please add “in laboratory conditions”. The authors have not performed experiments during a winemaking process.
Line 633 the reference 27 is missing.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
