Effect of New Methods for Inhibiting Malolactic Fermentation on the Analytical and Sensory Parameters of Wines
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsAt the start I would mention, that study is interesting and manuscript is sound. There are some small mistakes to correct, however.
L. 41-44 Do these techniques decrease SO2 level in wine or they can be INSTEAD of adding large amounts of SO2? Wording suggests the former and I don’t believe it is true.
L. 51-58 Are there some drawbacks of using chitosan? It would be good to present both sides of the coin, especially as the manuscript tries to find a new methods for inhibition of MLF.
L. 59-64 Was fumaric acid used to inhibit the MLF in wines? If not, highlight it. If it was, shortly describe the results.
L. 65-74 Information about influence of these acids on the favour of the wine should be implemented in this section.
L 75-84 Various polyphenols can have an effect on the taste and clarity of the wine. I think it should be mentioned.
Section 2.1. What kind of yeast was used? Please, provide at least trade name and manufacturer.
Section 2.2. Three repetitions from each vessel or three repetitions total for each of the wine types?
Table 1 – Why are there no homogenous groups given in this table?
L. 193 – I would use term ‘lipases’ not singular ‘lipase’, because variety of bacteria can produce variety of different lipases.
L. 199-203 This part needs more explanation, because, frankly, it doesn’t make a lot of sense in the first place. So, adding 10000 or 20000 ug of fatty acids per liter of the wine has no influence on the concentration of these acids in the finished product?
L. 203-206 This is kind of general statement. I also wouldn’t go into assessment of the particular levels, because it is a group of various compounds. I am sure that beverage with variety of higher alcohols in the range of 400 mg per L would have far better aroma than a beverage with 280 mg per L of 1-propanol and minuscule (20 mg) amount of other higher alcohols. This is further discussed in the cited work (Swiegers & Pretorius, 2005) and shouldn’t be generalised.
L. 210-215 What can be the reason for that fact?
L. 238-244 Again, why does it happen? Please, discuss.
Figure 5 is unclear, please, correct it. Also, L. 299-306 – please, discuss. And in line 306 you have made an mistake with copy-pasting and lack ug per L in ‘MCFA (1.56v…)
Furthermore – why do authors use ‘.’ for multiplication sign throughout the manuscript? It should be corrected.
Please, prove clearer figure 6.
L. 326-328 I wouldn’t go into saying that some wines acquired highest concentration of positive ‘aromatics’ and talk about higher alcohols, which were previously mentioned as not desirable trait in the high quantities. Also, word ‘aromatics’ should be avoided, as it can indicate chemical aromatic rings, not only the ‘aroma’ or ‘flavour’.
Appendix – Is the all p-value in Table A1 really 0.0000? Additionally, why is the ‘a’ group given to the lowest value?
Author Response
Dear Reviewer, thank you for reviewing the article and valuable comments. We have accepted all suggested corrections.
At the start I would mention, that study is interesting and manuscript is sound. There are some small mistakes to correct, however.
- 41-44 Do these techniques decrease SO2 level in wine or they can be INSTEAD of adding large amounts of SO2? Wording suggests the former and I don’t believe it is true.
Answer: Corrected.
- 51-58 Are there some drawbacks of using chitosan? It would be good to present both sides of the coin, especially as the manuscript tries to find a new methods for inhibition of MLF.
Answer: Drawback are added.
- 59-64 Was fumaric acid used to inhibit the MLF in wines? If not, highlight it. If it was, shortly describe the results.
Answer: Information was added.
- 65-74 Information about influence of these acids on the favour of the wine should be implemented in this section.
Answer: Information was added.
L 75-84 Various polyphenols can have an effect on the taste and clarity of the wine. I think it should be mentioned.
Answer: Information was added.
Section 2.1. What kind of yeast was used? Please, provide at least trade name and manufacturer.
Answer: Information was added.
Section 2.2. Three repetitions from each vessel or three repetitions total for each of the wine types?
Answer: In this chapter, three replicates from each sample taken were meant. In total, an average of 6 values was obtained for each experimental variant in each term.
Table 1 – Why are there no homogenous groups given in this table?
Answer: We added this contribution to the Table 1.
- 193 – I would use term ‘lipases’ not singular ‘lipase’, because variety of bacteria can produce variety of different lipases.
Answer: Corrected.
- 199-203 This part needs more explanation, because, frankly, it doesn’t make a lot of sense in the first place. So, adding 10000 or 20000 ug of fatty acids per liter of the wine has no influence on the concentration of these acids in the finished product?
Answer: Explained.
- 203-206 This is kind of general statement. I also wouldn’t go into assessment of the particular levels, because it is a group of various compounds. I am sure that beverage with variety of higher alcohols in the range of 400 mg per L would have far better aroma than a beverage with 280 mg per L of 1-propanol and minuscule (20 mg) amount of other higher alcohols. This is further discussed in the cited work (Swiegers & Pretorius, 2005) and shouldn’t be generalised.
Answer: Statement was corrected.
- 210-215 What can be the reason for that fact?
Answer: Information was added.
- 238-244 Again, why does it happen? Please, discuss.
Answer: Information was added.
Figure 5 is unclear, please, correct it. Also, L. 299-306 – please, discuss. And in line 306 you have made an mistake with copy-pasting and lack ug per L in ‘MCFA (1.56v…)
Answer: Figure is corrected and information was added.
Furthermore – why do authors use ‘.’ for multiplication sign throughout the manuscript? It should be corrected.
Answer: Corrected.
Please, prove clearer figure 6.
Answer: Corrected.
- 326-328 I wouldn’t go into saying that some wines acquired highest concentration of positive ‘aromatics’ and talk about higher alcohols, which were previously mentioned as not desirable trait in the high quantities. Also, word ‘aromatics’ should be avoided, as it can indicate chemical aromatic rings, not only the ‘aroma’ or ‘flavour’.
Answer: Corrected.
Appendix – Is the all p-value in Table A1 really 0.0000? Additionally, why is the ‘a’ group given to the lowest value?
Answer: Yes, p-values are really 0.0000. The designation of homogeneous groups was chosen in this way for greater clarity. Group 'a' always means the lowest values...
Reviewer 2 Report
Comments and Suggestions for AuthorsComments are also given directly to the corresponding paragraph in the paper (See attached PDF)
The paper deals with innovative strategies to prevent MLF. Chemical and sensory analysis were performed in order to show differences in the different variants that were tested. However, some of the wines underwent a MLF, others not. It is very obvious that wines with MLF show a different aroma profile than wines without MLF. Nevertheless, all wines were compared to each other. This is a lack in the experimental design, I think. Or else, the authors should change the interpretation of the data.
Furthermore, there are only 2 replicates per variant. BEsides, I miss a better statistical analysis of the sensory data (for example PCA), also in combination with the chemical data.
Finally, I miss some microbiological analysis.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer, thank you for reviewing the article and valuable comments. We have accepted all suggested corrections.
The paper deals with innovative strategies to prevent MLF. Chemical and sensory analysis were performed in order to show differences in the different variants that were tested. However, some of the wines underwent a MLF, others not. It is very obvious that wines with MLF show a different aroma profile than wines without MLF. Nevertheless, all wines were compared to each other. This is a lack in the experimental design, I think. Or else, the authors should change the interpretation of the data.
Answer: We ran the MLF purposefully only in the Control variant in order to see the differences. The SO2 variant served as the second control for comparison with individual preparations.
Furthermore, there are only 2 replicates per variant. BEsides, I miss a better statistical analysis of the sensory data (for example PCA), also in combination with the chemical data.
Finally, I miss some microbiological analysis.
Answer: In this case, this is a pilot study that will be referenced by other studies that include a larger trial with more replications, a microbiological trial (growth curves and microbiological stability) and HPLC analysis of organic acids, so we could no longer include these data in this study.
Comments:
- 159: Information added.
- 172: Before each blind tasting, we perform a judging of the null sample with an explanation of the experimental design. This is an experienced team of evaluators who evaluate dozens of experiments a year.
- 180: We improved in the text and table.
- 233: DIacetyl is mentioned here as another carbonyl compound on which MCFA has a positive effect...however, no statistically significant differences were observed in this study compared to other variants, so they were not included in the graph.
Reviewer 3 Report
Comments and Suggestions for AuthorsThis study compared the influence of five preparations，fumaric acid, chitosan, Estaan，MCFA and sulphur dioxide，used to inhibit malolactic fermentation to reduce the use of SO2. All oenological preparations used to inhibit malolactic fermentation demonstrated an inhibitory effect against lactic bacteria，while the Estaan and chitosan’s inhibitory effect were not permanent. The research work is interesting and useful for wine fermentation. The paper is suitable for publication in the journal.
Author Response
Dear reviewer, thank you for the review and positive assessment of our manuscript.
Round 2
Reviewer 2 Report
Comments and Suggestions for Authors
Comments for author File: Comments.pdf
Author Response
Concerning the following 4 points the authors haven’t given an acceptable answer yet:
- My comment from table 1 was not answered:
My comment was:
“Here I miss a lot of interpretation of the data, for example: Why does Malic acid increase in the control at the second time point? Why does Acetic acid decrease in the control at the second time point?
→ No answer of the authors
Answer: In this case, perhaps it is measuring error, we revised the data and there is i large variability of each value before avereging.
Why is in the control Lactic acid lower at the second time point than in the Chitosan variant?...Perhaps the acids should be enzymatically analysed...”
Answer: We think, it is right. Based on the results, there is no totally complete malolactic fermentation undergone in MLF variant (0,79 g/L of MA) contrary to chitosan variant (0,17 g/L of MA). So the lactic acid content is lower in control variant. ...
- My comment from review1 should be reconsidered:
My comment was:
The paper deals with innovative strategies to prevent MLF. Chemical and sensory analysis were performed in order to show differences in the different variants that were tested. However, some of the wines underwent a MLF, others not. It is very obvious that wines with MLF show a different aroma profile than wines without MLF. Nevertheless, all wines were compared to each other. This is a lack in the experimental design, I think. Or else, the authors should change the interpretation of the data.
Answer: We ran the MLF purposefully only in the Control variant in order to see the differences. The SO2 variant served as the second control for comparison with individual preparations.
→ In this case the data should interpreted with the SO2 variant as control for all non MLF wines and with the MLF control for all MLF wines....
Answer: We agree with the proposed change and have changed the designation of the variants both in the text and in the tables and graphs.
- My comment from review1 should be reconsidered:
My comment was:
Furthermore, there are only 2 replicates per variant. Bwsides, I miss a better statistical analysis of the sensory data (for example PCA), also in combination with the chemical data.
Finally, I miss some microbiological analysis.
Answer: In this case, this is a pilot study that will be referenced by other studies that include a larger trial with more replications, a microbiological trial (growth curves and microbiological stability) and HPLC analysis of organic acids, so we could no longer include these data in this study.
→ This is not an explanation for having only two replicates
Answer: Unfortunately, we only have two repetitions, but in larger volumes. We have done three repetitions of the analytical measurement.
To support the correctness of the results, we have the same trial based on small volumes, but the results will be included in another, follow-up study.
- My comment from review1 should be reconsidered:
My comment was:
Where are the diacetyl results?
Answer: 233: DIacetyl is mentioned here as another carbonyl compound on which MCFA has a positive effect...however, no statistically significant differences were observed in this study compared to other variants, so they were not included in the graph.
→Data should be shown, if there is no statistically significant differences it also cannot have a positive effect…
Answer: In this case, I apologize for the wrong answer, we have not measured the results of diacetyl. We have made the corresponding data in the text where it is not already mentioned.
