Chemical and Sensory Profiles of Merlot Wines Produced by Sequential Inoculation of Metschnikowia pulcherrima or Meyerzyma guilliermondii

Round 1

Reviewer 1 Report

M&M

Very simple description of GC MS method please describe better: column, conditions,...

Results

Why were inoculated the Sc on day 3? Maybe a longer period improved the effect of the non-Sacch

Table 1 interesting that non-Sacch decreased volatile acidity.

Glycerol values are que high with all the yeasts, do you have any explanation?

Why is decreased the pH with the non-Sacch, even with degradation of malic acid?

I think that a spider net graph for sensory analysis would be more illustrative than the table.

Discussion

The most innovative is the use of My instead of the typical Mp, but the effect is similar. Which is the improvement?

Concerning the unclear carbon fate and the lower pH, do you think that order organic acid can be formed?

Author Response

REVIEWER #1

Reviewer’s comment: M&M. Very simple description of GC MS method please describe better: column, conditions,...

Authors’ response: Information has been updated. Refer to lines 114 to 124.

Reviewer’s comment: Results. Why were inoculated the Sc on day 3? Maybe a longer period improved the effect of the non-Sacch.

Authors’ response: It has been widely believed that many of the non-Saccharomyces yeasts die-off as soon as alcoholic fermentation begins, either due to low tolerance to ethanol, antagonistic interactions with fermentative yeast, or other undefined methods. Some of our preliminary work has indicated that three days may be optimal but more experimentation is required.

Reviewer’s comment: Results. Table 1 interesting that non-Sacch decreased volatile acidity.

Authors’ response: The Reviewer is absolutely correct; this was an interesting finding. Without additional experimentation, esterification with alcohols is possible but there are other potential mechanisms.

Reviewer’s comment: Results. Glycerol values are que high with all the yeasts, do you have any explanation?

Authors’ response: No, we do not have an explanation as equivalent concentrations have been previously reported as well.

Reviewer’s comment: Results. Why is decreased the pH with the non-Sacch, even with degradation of malic acid?

Authors’ response: The degree to which pH was altered was not extremely large (≤0.1 units) but statistically significant. To date, potential mechanisms have not yet been identified.

Reviewer’s comment: Results. I think that a spider net graph for sensory analysis would be more illustrative than the table.

Authors’ response: The Authors agree with the Reviewer but when the spider graph was prepared, it appeared to be far too complicated given the number of terms. Our sensory scientist suggested the use of a table instead.

Reviewer’s comment: Discussion. The most innovative is the use of My instead of the typical Mp, but the effect is similar. Which is the improvement?

Authors’ response: Perhaps our laboratory is “old school” but Reviewers have required used genus abbreviations prior to species names.

Reviewer’s comment: Discussion. Concerning the unclear carbon fate and the lower pH, do you think that order organic acid can be formed?

Authors’ response: Our laboratory is currently investigating the fate of carbon. Results so far has been quite mixed; some believe that carbon flows into succinate, fumarate, and/or glycerol or is completely respired. None of our current experiments support these hypotheses so our work is continuing to examine other fates.

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a straightforward fermentation manuscript of a sequential fermentation using two non-Saccharomyces strains. The big difference is that the authors have done this on a larger scale which is one of the fewer cases as most publications still focus on microvinifications in a lab setting. They report a ~1% reduction in the alcohol levels which is highly desired in modern-day winemaking.

Overall, the manuscript is easy to read and could be considered for publications. There are still some issues and the biggest (for me) is that the authors omitted some detail on the scale of the fermentation that took place. What was the volume of  the vessel/steel tanks? How many liters of must are 37.5kg of must (line78-79).

Other issues:

line 4: consider removing "followed by Saccharomyces cerevisiae". Sequential implies S. cerevisiae was added and the title is a bit wordy.

 line 14: detail of the must in brackets is unnecessary in the abstract

Introduction in general. Authors should cite 10.3390/microorganisms8071038 especially to mention that a couple of Metschnikowia strains are commercially available

Authors should also incorporate 10.3390/microorganisms8071029  or related work to just emphasize the pulcherrim production and how it could affect fermentation

line 63: it is Enoferm Syrah

line 66: just say glucose and not dextrose

line 88: what is the breakdown of the fructose and glucose

Fig 1 and 2. I am not sure what the authors are trying to portray with the arrows at day 10/12 of the NSY. If they couldn't culture any NSY (or very few) on these days on the lysine plates then that should be a solid point on the zero axis

line 181: S. cerevisiae not cursive

Table 1. Just as a quick reference it might be helpful to give the names of the NSYs again rather than readers needing to go back to the text

Author Response

REVIEWER #2

Reviewer’s comment: This is a straightforward fermentation manuscript of a sequential fermentation using two non-Saccharomyces strains. The big difference is that the authors have done this on a larger scale which is one of the fewer cases as most publications still focus on microvinifications in a lab setting. They report a ~1% reduction in the alcohol levels which is highly desired in modern-day winemaking.

Authors’ response: The Authors extend a thank you to the Reviewer for his/her comments which improved the quality of the manuscript.

Reviewer’s comment: Overall, the manuscript is easy to read and could be considered for publications. There are still some issues and the biggest (for me) is that the authors omitted some detail on the scale of the fermentation that took place. What was the volume of the vessel/steel tanks? How many liters of must are 37.5kg of must (line 78-79)?

Authors’ response: Information has been added. We thank the Reviewer for pointing out this oversight (line 80).

Reviewer’s comment: line 4: consider removing "followed by Saccharomyces cerevisiae". Sequential implies S. cerevisiae was added and the title is a bit wordy.

Authors’ response: Text was altered (line 4).

Reviewer’s comment: line 14: detail of the must in brackets is unnecessary in the abstract.

Authors’ response: Many reviewers request this type of detail to be within the abstract. If the Reviewer wishes, the Authors can remove but would suggest to maintain the current information.

Reviewer’s comment: Introduction in general. Authors should cite 10.3390/microorganisms8071038 especially to mention that a couple of Metschnikowia strains are commercially available.

Authors’ response: The Authors thank the Reviewer for pointing out this newer reference and have included this work into the manuscript.

Reviewer’s comment: Authors should also incorporate 10.3390/microorganisms8071029 or related work to just emphasize the pulcherrim production and how it could affect fermentation.

Authors’ response: The Authors felt the need to limit the number of references to include given the manuscript already has 39 cited. If the fermentations had slowed due to addition of Mt. pulcherrima, then the work of Sipiczki (2020) would have been critical for discussion. Because fermentations were not affected, the role of pulcherrim (if any) remains unknown.

Reviewer’s comment: line 63: it is Enoferm Syrah.

Authors’ response: Text was altered (line 64).

Reviewer’s comment: line 66: just say glucose and not dextrose.

Authors’ response: Text was altered (line 67).

Reviewer’s comment: line 88: what is the breakdown of the fructose and glucose.

Authors’ response: During fermentation, the concentrations of fructose and glucose were not continuously monitored as collecting this information was of lower priority given the hypothesis being tested.

Reviewer’s comment: Fig 1 and 2. I am not sure what the authors are trying to portray with the arrows at day 10/12 of the NSY. If they couldn't culture any NSY (or very few) on these days on the lysine plates then that should be a solid point on the zero axis.

Authors’ response: The dashed errors indicate that the populations declined below the detection limit (<300) as noted in the vertical axis. To use a solid line would indicate that the lower population values were actually known (and they were not).

Reviewer’s comment: line 181: S. cerevisiae not cursive.

Authors’ response: The Authors apologize to the Reviewer but searched the entire manuscript and could not find this typographical error.

Reviewer’s comment: Table 1. Just as a quick reference it might be helpful to give the names of the NSYs again rather than readers needing to go back to the text.

Authors’ response: The Authors thank the Reviewer as this was an outstanding addition to Table 1 (refer to line 225).

Author Response File: Author Response.pdf

Reviewer 3 Report

Please include capacity of stainless steel tanks.

Author Response

REVIEWER #3

Reviewer’s comment: Please include capacity of stainless steel tanks.

Authors’ response: Information has been added to the text. We thank the Reviewer for pointing out this oversight (line 80).

Author Response File: Author Response.pdf