Evaluation of Fractions Obtained Through Steam Distillation and Hydroalcoholic Maceration of Wood Chips from Pinus mugo for Flavouring Italian Spirit grappa
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study is novel and well-executed, offering significant contributions to the valorization of Pinus mugo as a flavoring agent.
I would like to bring your attention to the sensory evaluation section, specifically regarding the statement, "A descriptive test was carried out to identify and quantify the nature of the sensory difference." While it is stated that a descriptive test was performed, the specific type of test is not specified. Descriptive tests are a broad category that includes various methodologies such as Quantitative Descriptive Analysis (QDA), Flavor Profile (FP), or others. To ensure the methodology is clear and replicable, I suggest specifying which particular descriptive test was used and it is important to support it with literature.
Also while the triangle test is mentioned, it would be beneficial to clarify why this specific discriminant test was chosen over other possible options. Additionally, consider including the exact number of replicates for the triangle test to provide a clearer understanding of the test's statistical robustness.
You mention that 17 assessors were trained in odour and taste descriptors. It would be useful to elaborate on the training process, especially the number of training sessions, and whether the assessors had prior experience.
While the findings are well-presented, please clarify the statistical significance of sensory and chemical differences.
In sensory evaluation it would be important to specify whether the triangle test and descriptive test were performed in replicates, and if so, how many were conducted to ensure statistical reliability.
It would be beneficial to mention what statistical methods were used to analyze the data collected from the sensory evaluation tests (e.g., ANOVA, MANOVA). This would help readers understand how the sensory data was treated and interpreted.
I suggest adding an asterisk (*) in Figure 4. after performing statistical treatment to indicate significant differences between the samples.
The conclusion should be improved and it would be valuable to include some suggestions for future research or practical steps that could be taken based on your findings. For instance, you might mention investigating the scalability of this approach or exploring the impact of other flavouring agents on the sensory profile of grappa. Providing the next steps would help to frame the broader significance of your work and guide future studies in this area.
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.
We have considered the feedback and suggestions provided, and since QDA analysis raised major concerns, and resulted statistically not significant, we have decided to remove it from the paper body. Our focus was on the technological insights, and the goal of the work remains unchanged, as it aimed at evaluating different products, for which the triangle test was sufficient. Therefore, the removal of QDA does not affect the results or conclusions of the study.
Here following you can find a reply point by point to all the provided comments:
Comments 1: I would like to bring your attention to the sensory evaluation section, specifically regarding the statement, "A descriptive test was carried out to identify and quantify the nature of the sensory difference." While it is stated that a descriptive test was performed, the specific type of test is not specified. Descriptive tests are a broad category that includes various methodologies such as Quantitative Descriptive Analysis (QDA), Flavor Profile (FP), or others. To ensure the methodology is clear and replicable, I suggest specifying which particular descriptive test was used and it is important to support it with literature.
Response 1: As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 2: Also while the triangle test is mentioned, it would be beneficial to clarify why this specific discriminant test was chosen over other possible options. Additionally, consider including the exact number of replicates for the triangle test to provide a clearer understanding of the test's statistical robustness.
Response 2: Thank you for pointing this out. We specified that “This test was chosen to test for perceptible differences due to different flavouring addition to a homogeneous base spirit” (lines 170-171). Since the objective was to test for perceptible different between flavoruing agents to the same base spirit, the triangle test was chosen. Other tests, such as the duo-trio test, the difference from control test and the same-different test are preferable when testing for differences from a standard or control product. In this case, different flavouring agents were equally compared.
Comments 3: You mention that 17 assessors were trained in odour and taste descriptors. It would be useful to elaborate on the training process, especially the number of training sessions, and whether the assessors had prior experience.
Response 3: As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 4: While the findings are well-presented, please clarify the statistical significance of sensory and chemical differences.
Response 4: Results of the statistical analysis were added where missing:
Line 290 “All models and coefficients were significant for p<0.05.”
Lines 450-451 “The discriminant tests significantly differentiated samples flavoured with wood chips from those flavoured with essential oil (p< 0.001).”
In relation to the chemical characterisation, significance for the ANOVA and Tukey HSD test was reported for each compound in Table 4.
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 5: In sensory evaluation it would be important to specify whether the triangle test and descriptive test were performed in replicates, and if so, how many were conducted to ensure statistical reliability.
Response 5: Yes, in the triangle test each tasting included three replicates.
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 6: It would be beneficial to mention what statistical methods were used to analyze the data collected from the sensory evaluation tests (e.g., ANOVA, MANOVA). This would help readers understand how the sensory data was treated and interpreted.
Response 6: We specified that the statistical analysis was based on the Chi-square test.
Lines 218-219 “The significance of the triangle tests was assessed following the procedure established by ISO 4120/2021 [20], based on the Chi-square test between measured and expected distributions.”
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 7: I suggest adding an asterisk (*) in Figure 4. after performing statistical treatment to indicate significant differences between the samples.
Response 7: As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 8: The conclusion should be improved and it would be valuable to include some suggestions for future research or practical steps that could be taken based on your findings. For instance, you might mention investigating the scalability of this approach or exploring the impact of other flavouring agents on the sensory profile of grappa. Providing the next steps would help to frame the broader significance of your work and guide future studies in this area.
Response 8: Thank you for the suggestion. We revised the conclusions accordingly. Please see Lines 512-517.
Reviewer 2 Report
Comments and Suggestions for Authors
The first question for authors is as follows: why is the data from the GC/MS presented only as the supplementary? I would recommend including it in the manuscript.
Throughout the manuscript, authors use ml or L. The proper way is mL and L. However, it would be the best to change liters to metric units, so, use dm³, cm³ and mm³.
Furthermore, many numbers are written with “,” as a decimal point, instead of “.”. Please, correct that in whole manuscript.
Specific comments:
L 104. g, not gr for grams.
L. 135-138 Why didn’t you use amount of essential oil which was distilled from 60 grams of would? That would be far better comparison of these two methods.
L. 140 Six? Fresh wood, spent wood, essential oil. Its three. Why six?
L. 141 What kind of liquid was used for the extraction?
L. 160 Why isn’t the ICP-MS method described?
L. 169 Age and sex of the panellists? Were they trained?
L. 174-175 Two millilitres seem like not enough of the sample for a proper test.
L. 178-184 All of that in 2 mL sample? Impossible, in my opinion.
L. 182-184 5 point category scale, which is described, doesn’t seem correct. If 1 is ‘don’t like’ then 5 should be ‘like’ not ‘like very much’. 5 point scale should look like that:
1- doesn’t like very much
2 – doesn’t like
3 – neither likes nor disliks
4 – likes
5 – likes very much.
Its better, but still, 7 point or 9 point should be used. Design of the analysis is wrong.
L. 185-192 And why isn’t that data present in the manuscript?
L. 221 – any possible reason, why was the essential oil amount so small?
L. 247-249 Products of Maillard reactions also are characterised with high antioxidant capacity, perhaps you want to use this data in discussion.
Figure 1 – maybe could you use different shape for spent and fresh woodchips, (circle and square, for example) so it could be read in black-and-white? Just a detail, not necessary to change that.
L. 451-452 Not even in the ‘balsamic’ and ‘bitterness’?
Figure 4 – why is the 6 maximum value on the graph? It strongly suggests that the 6 was the highest possible value, when in reality it was 9.
Discussion section – no references at all used?
L. 512-514 Wrong way to use ‘on one hand, on the other hand’. It should be used, when speaking two opposite things. For example, ‘I am thinking about quitting my weekend job, on one hand, I would like to have more free time, on the other hand I still need additional money’.
Comments on the Quality of English Language
As an addition to the earlier comments, I would suggest getting the manuscript looked at by a native speaker or somebody who speaks English language freely. Variety of the phrases are used not properly.
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.
We have considered the feedback and suggestions provided, and since QDA analysis raised major concerns, and resulted statistically not significant, we have decided to remove it from the paper body. Our focus was on the technological insights, and the goal of the work remains unchanged, as it aimed at evaluating different products, for which the triangle test was sufficient. Therefore, the removal of QDA does not affect the results or conclusions of the study.
Here following you can find a reply point by point to all the provided comments:
Comments 1: The first question for authors is as follows: why is the data from the GC/MS presented only as the supplementary? I would recommend including it in the manuscript.
Response 1: Thank you for pointing this out. We made the changes accordingly and reported the GC/MS results in the manuscript (Table 4).
Comments 2: Throughout the manuscript, authors use ml or L. The proper way is mL and L. However, it would be the best to change liters to metric units, so, use dm³, cm³ and mm³.
Response 2: We changed all measures accordingly.
Comments 3: Furthermore, many numbers are written with “,” as a decimal point, instead of “.”. Please, correct that in whole manuscript.
Response 3: We corrected accordingly.
Comments 4 and response:
Specific comments:
L 104. g, not gr for grams.
Corrected.
L135-138 Why didn’t you use amount of essential oil which was distilled from 60 grams of would? That would be far better comparison of these two methods.
Thank you for your valuable feedback. The primary aim of this work was not to facilitate a direct comparison, but to provide producers with a method to modulate the characteristics of their products. The proposed technique offers flexibility, allowing producers to adjust the amount of essential oil added—whether less, more, or the same as what is naturally present in the woodchips—thus enabling product personalization. Additionally, the dilution effect was investigated in a preliminary trial (Lines 136-138), which helped establish the sensory perception threshold that became the reference for these trials.
L.140 Six? Fresh wood, spent wood, essential oil. Its three. Why six?
It was our mistake. Corrected.
L. 141 What kind of liquid was used for the extraction?
Dichloromethane was used; we specified in Lines 141-142.
L.160 Why isn’t the ICP-MS method described?
The method employed is a standard procedure used by the LaChi laboratory (DAFNAE Department, University of Padova, Italy) and we have now included the appropriate reference to support this.
L.169 Age and sex of the panellists? Were they trained? For the Quantitative Descriptive Analysis, information on the panellists and more detailed explanation of the training session have been reported in the supplementary materials, together with the results of the test.
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
L. 174-175 Two millilitres seem like not enough of the sample for a proper test.
Based on the recommendations from the Ethical Committee, panellists were not allowed to swallow the grappa samples. They were asked to smell the sample and take a small sip, but they were instructed to not ingest. Therefore, the quantity was reduced. We noticed that after each test, all the panellists were left with a considerable amount of grappa sample, which was not fully consumed.
L.178-184 All of that in 2 mL sample? Impossible, in my opinion.
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
L. 182-184 5 point category scale, which is described, doesn’t seem correct. If 1 is ‘don’t like’ then 5 should be ‘like’ not ‘like very much’. 5 point scale should look like that:
1- doesn’t like very much
2 – doesn’t like
3 – neither likes nor disliks
4 – likes
5 – likes very much.
Its better, but still, 7 point or 9 point should be used. Design of the analysis is wrong.
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
L.185-192 And why isn’t that data present in the manuscript?
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
L. 221 – any possible reason, why was the essential oil amount so small?
The limited EO yield could be related to both the age of the plant material and the distillation method. Lis et al (2019) reported that the essential oil yield from Pinus mugo wood was 0.1%. The material used in their experiment was wood from 2-3 year-old branches, while in the present experiment we received wood material with a wider age range and older plants were included. Our study also differed in relation to the distillation method and extraction time. The distillation apparatus used by Lis et al (2019) was a Clevenger-type apparatus, which performs hydrodistillation, and the extraction lasted 3 hours. In our experiment, we performed steam distillation in a pilot still for one hour. Since we did not find sufficient data for comparison, we conclude that the small EO yield obtained was due to machinery and time parameters.
L. 247-249 Products of Maillard reactions also are characterised with high antioxidant capacity, perhaps you want to use this data in discussion.
Thank you for this hint. We did some speculation on this aspect but we prefer not to make assumptions regarding factors that were not measured in this study.
Figure 1 – maybe could you use different shape for spent and fresh woodchips, (circle and square, for example) so it could be read in black-and-white? Just a detail, not necessary to change that.
We have improved the figures based on your suggestion.
L. 451-452 Not even in the ‘balsamic’ and ‘bitterness’?
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Figure 4 – why is the 6 maximum value on the graph? It strongly suggests that the 6 was the highest possible value, when in reality it was 9.
As explained above, we have removed the Quantitative Descriptive Analysis (QDA) from the manuscript.
Comments 5: Discussion section – no references at all used?
Response 5: Thank you for pointing that out. We integrated the discussion sessions with the references used. For some reason, they were lost due to issues with the links to the reference management software. However, the discussion is now reporting the appropriate references.
Comments 6: L. 512-514 Wrong way to use ‘on one hand, on the other hand’. It should be used, when speaking two opposite things. For example, ‘I am thinking about quitting my weekend job, on one hand, I would like to have more free time, on the other hand I still need additional money’.
Response 6: Thank you for this revision. We corrected the phrasing.
4. Response to Comments on the Quality of English Language
Point 1: As an addition to the earlier comments, I would suggest getting the manuscript looked at by a native speaker or somebody who speaks English language freely. Variety of the phrases are used not properly.
Response 1: Thank you very much for your suggestion. We have carefully revised the manuscript to improve the clarity and flow of the language.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsManuscript was improved. However, please check the lines 137, 143 and the table 5 for the , mL, L and so on.
Also, in the Tables names, when you describe that the 'data is expressed as (...) Anova (...) p = 0.001 (...)' and so on... Typically, that data is presented under the table not in the description of the table. MDPI template shows you how to do it, perhaps you could change it.
Author Response
Thank you very much for your additional comments to this manuscript. The corresponding revisions have been made as follows.
Reviewer: "Manuscript was improved. However, please check the lines 137, 143 and the table 5 for the , mL, L and so on."
Reply: Corrections have been made accordingly.
Reviewer: "Also, in the Tables names, when you describe that the 'data is expressed as (...) Anova (...) p = 0.001 (...)' and so on... Typically, that data is presented under the table not in the description of the table. MDPI template shows you how to do it, perhaps you could change it."
Reply: Footers have been added to Tables 3 and 4.
