Chemical Characterization of Cider Produced in Hardanger—From Juice to Finished Cider

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript evaluates cider production from a specific region in Norway. The manuscript can potentially provide valuable information on the composition of ciders, also according to zone and cultivar variability. However, its scientific quality is not satisfactory due to specific issues. The key issues are:
- Unclear sampling. No list of samples is provided, and for each set of parameters is reported a different sample size. For instance, by comparing the table captions of data (general, phenolic, aroma; Tables 3, 5, 6) al the sample sizes reported are basically different, both indicating a lack of correspondence among samples on juices, mid-fermentation, post-fermentation, but also for the same sample combination (e.g. same cultivar and sampling point) across different parameter types. This last aspect is quite problematic, because it means that some samples were evaluated for some parameter (e.g. basic data) but not for phenolics or aroma. How can we compare the samples data if some parameters present one sample set, and other parameters are done on another set? The authors wrote that there are 17 full sets (line 108), perhaps they can focus only on full sets if they have all analysis for all of these samples.
- Lack of statistical evaluation of the differences found among samples. This aspect needs to be corrected and the relevant statistics (e.g. ANOVA and post-hoc evaluation) included. When statistics are available, the discussion needs to be revised according to the outcome of the significances of differences found, otherwise the statements about differences in the text are not backed by statistics.
- How is "mid-fermentation" defined? Residual sugars (glucose+fructose) data is very variable among these samples (4.6-125.4 g/L!).
- The authors cite "seasonal variation of the fruit" as a variation factor (which is, generally speaking, indoubtably correct), but many samples were chaptalized (lines 254-261), and no specific information is provided about this aspect for the samples analyzed. Therefore, comparing samples with different levels of chaptalization may be very difficult, particularly when (as is this case) the reader is not aware of which samples were chaptalized and which samples were not.

Some other issues are present and reported afterwards.

Abstract and Introduction: there is a general recall to terms concerning wine and winemaking, which is incorrect based on the topic of the article. "General oenological parameters" in the abstract, line 14 (and also in the conclusions, line 472), can be replaced by "general parameters". The "wine monopoly" in the Introduction perhaps it can be replaced by a more inclusive definition or called by its original name.

Material and Methods:
- regarding samples, the authors indicate that 77 samples were collected, but it is hard to understand how these were distributed according to apple cultivar, stage, eventual harvest year, chosen yeast strain and fermentation temperature, chaptalization etc. As previously described, the table captions try to summarize this aspect, but for instance Table 3 caption indicates only 53 samples, and sample size were different for the other tables. In my opinion, a list of samples with key information for each sample is necessary, as supplementary material.
- the ten cider producers sampled (line 103) are representing how much share of the denomination considered (in terms of number of producers and volume produced)?
- how sucrose was determined? No method is listed, only a method for glucose and fructose is reported (lines 131-143).
- Statistics section, lines 228-230: this information is not concerning statistics, it needs to be placed in the methods.

Results and Discussion:
- as previously indicated, all statements needs to be reconsidered in light of the relevant statistics, when available;
- in order to improve the clarity and readability of the results, I suggest to convert Table 3 (and other data tables) to a figure-graph, for instance using boxplots to describe the variability among samples for each parameter. The actual numerical data (presented tables) can be suppled as supplementary material.

Typos:
- few typos are present (e.g. "Typography" line 34, "60 °N" line 36, "-12-18°C" line 115)
- there are two tables listed as Table 5

Comments on the Quality of English Language

Few typos are present (e.g. "Typography" line 34, "60 °N" line 36, "-12-18°C" line 115)

Author Response

Comment 1, R1: Unclear sampling. No list of samples is provided, and for each set of parameters is reported a different sample size. For instance, by comparing the table captions of data (general, phenolic, aroma; Tables 3, 5, 6) al the sample sizes reported are basically different, both indicating a lack of correspondence among samples on juices, mid-fermentation, post-fermentation, but also for the same sample combination (e.g. same cultivar and sampling point) across different parameter types. This last aspect is quite problematic, because it means that some samples were evaluated for some parameter (e.g. basic data) but not for phenolics or aroma. How can we compare the samples data if some parameters present one sample set, and other parameters are done on another set? The authors wrote that there are 17 full sets (line 108), perhaps they can focus only on full sets if they have all analysis for all of these samples.

Response to comment 1, R1: Thank you for good advice. The results in the tables and figures are in the new version based on the same samples, and an overview of the samples and production method is listed in Table 1. Due to this the total number of samples has been reduced from 77 to 65 samples (included mid-fermentation, and 45 without mid-fermentation) We choose to keep 5 samples which is not of a complete sample set. The argumentation for this choice is that the main purpose of this paper is to give an overview of the chemical characterisation of the ciders produced under the PDO label “Cider from Hardanger”, so the correspondence among juice and cider samples are not important.

Comment 2, R1: Lack of statistical evaluation of the differences found among samples. This aspect needs to be corrected and the relevant statistics (e.g. ANOVA and post-hoc evaluation) included. When statistics are available, the discussion needs to be revised according to the outcome of the significances of differences found, otherwise the statements about differences in the text are not backed by statistics.

Response to comment 2, R1: Thank you for your feedback on the statistical evaluation of the data. We have now discussed with a statistician the best way of presenting our data and performed ANOVA GLM on the data. Our conclusion was that this is not possible, and we must be clearer about the purpose of the paper. The purpose is to give an overview of current situation regarding chemical composition of ciders produced under the PDO label “Cider from Hardanger”. We must look at the paper as a case study, and not a dataset to compare between cultivars and years. To do a proper statistical evaluation, as suggested by a reviewer 1, sampling should have been done different, ours supported case study of actual state.

Comment 3, R1: How is "mid-fermentation" defined? Residual sugars (glucose+fructose) data is very variable among these samples (4.6-125.4 g/L!).

Response to comment 3, R1: Deciding the mid-fermentation was based on alcohol content and the producer’s judgment of mid-fermentation. We agree that this sampling method is a bite uncertain and have decided to take the mid-fermentation results out of the paper.  

Comment 4, R1: The authors cite "seasonal variation of the fruit" as a variation factor (which is, generally speaking, indoubtably correct), but many samples were chaptalized (lines 254-261), and no specific information is provided about this aspect for the samples analyzed. Therefore, comparing samples with different levels of chaptalization may be very difficult, particularly when (as is this case) the reader is not aware of which samples were chaptalized and which samples were not.

Response to comment 4, R1:  The main purpose of this paper is to give an overview of the chemical characterisation of the ciders produced under the PDO label “Cider from Hardanger”. We aimed to understand how natural factors (e.g., seasonal changes) and actual practices in cider technology influence the chemical properties of apple juices and ciders. This foundational understanding is crucial for future studies that might incorporate or isolate the effects of chaptalization, which was not done in this study. We are of course aware that the level of chaptalization was not monitored particularly, and that could have influence chemical properties of ciders, however the study's findings on natural compositional variations of Cider from Hardanger remain valid and significant part of build database. We will add the R1 comment 4 about difficulty comparing the ciders with different and unknown level of chaptalisation in the manuscript discussion.

Comment 5, R1: Abstract and Introduction: there is a general recall to terms concerning wine and winemaking, which is incorrect based on the topic of the article. "General oenological parameters" in the abstract, line 14 (and also in the conclusions, line 472), can be replaced by "general parameters". The "wine monopoly" in the Introduction perhaps it can be replaced by a more inclusive definition or called by its original name.

Response to comment 5, R1: General Oenological parameters are replaced by general chemical parameters. The Norwegian original name Vinmonopolet of the wine monopoly is written in brackets.

Comment 6, R1: Material and Methods: Regarding samples, the authors indicate that 77 samples were collected, but it is hard to understand how these were distributed according to apple cultivar, stage, eventual harvest year, chosen yeast strain and fermentation temperature, chaptalization etc. As previously described, the table captions try to summarize this aspect, but for instance Table 3 caption indicates only 53 samples, and sample size were different for the other tables. In my opinion, a list of samples with key information for each sample is necessary, as supplementary material.

Response to comment 6, R1: Table of producer and number of samples per cultivar/year has now been included in Table 1.

Comment 7, R1:  the ten cider producers sampled (line 103) are representing how much share of the denomination considered (in terms of number of producers and volume produced)?

Response to comment 7, R1: Include approximate production volume in table 1.

Comment 8, R1: how sucrose was determined? No method is listed, only a method for glucose and fructose is reported (lines 131-143).

Response to comment 8, R1: Sucrose included in Line 144

Comment 9, R1: Statistics section, lines 228-230: this information is not concerning statistics, it needs to be placed in the methods.

Response to comment 9, R1: We put it under materials and methods

Comment 10, R1: Results and Discussion:
- as previously indicated, all statements needs to be reconsidered in light of the relevant statistics, when available;

Response to comment 10, R1: We have carefully considered this suggestion, and discussed that with our institutional biostatistician. Including the fact that we present a case study for building a database in sources of variability are too wide and not possible to be handled by available statistical approaches – so we can consider the data presentations (mean – min/max) only as trends and clarify that differences are not statistically significant.

Comment 11, R1: to improve the clarity and readability of the results, I suggest converting Table 3 (and other data tables) to a figure-graph, for instance using boxplots to describe the variability among samples for each parameter. The actual numerical data (presented tables) can be suppled as supplementary material.

Response to comment 11, R1: We thank for this suggestion, and we agree that graphs are a cleaner way to present data. However, presenting the data graphically means presentation of a high number of graphs. So, after deep discussions we have decided to keep the data as they are, in form of tables including min/max and average values.

Comment 12, R1: Typos:
- few typos are present (e.g. "Typography" line 34, "60 °N" line 36, "-12-18°C" line 115)
- there are two tables listed as Table 5

Response to comment 12, R1: The typos have now been corrected as suggested.

Reviewer 2 Report

Comments and Suggestions for Authors

This study measured and analyzed sugar, acid, ethanol, total phenols, individual polyphenols  and volatile compound in 77 samples of apple juice, during fermentation and in cider. By identifying and quantifying taste-specific compounds present in juice, mid-fermented, and final cider samples from various apple varieties that are commonly used in Hardanger cider production，the study enhanced the understanding of the chemical properties of ciders from Hardanger. The research emphasized the significance of identifying key chemical components that influence the sensory quality of Cider from Hardanger in order to establish product differentiation and consistent quality.

However, the author should consider the following aspects to improve their work.

 

1> In the introduction, the logical relationship between the third, fourth, and fifth paragraphs is not clear enough.

2> It is recommended to transfer Tables 1 and 2 into the supplementary materials. A brief introduction to the Materials and Methods is sufficient.

3> The title, analysis content, and data in Table 3 of 3.1.1 should be presented in the same order, such as sugar, ethanol and acid, for the convenience to read.

4> The data presented in sections 3.1.1, 3.2.2 and 3.2 of the article were presented in tabular form. For the authors, it’s better to first consider figures to present the data and deliver information.

5> Table 5 should be placed in the appendix, and it does not need to be elaborated too much. In addition, the title of Table 7 should be changed to Table 6.

6> To be precise, chlorogenic acid is a derivative of hydroxycinnamic acid, and language expression should be rigorous.

7> This article has tested the basic physicochemical indicators of the samples and the substances that affect the aroma of apple cider. However, color is also an important component factor affecting its quality. Why did the author not consider detecting the chemical substances that affect the color of apple cider?

Comments on the Quality of English Language

okay

Author Response

Reviewer nr 2 - Comments and Suggestions for authors from reviewer nr 2 and the authors responses to the comments:

 

Comment 1, R2: In the introduction, the logical relationship between the third, fourth, and fifth paragraphs is not clear enough.

Response to comment 1, R2: The manuscript has been corrected now and logical relationship between the paragraphs have been improved.

Comment 2, R2: It is recommended to transfer Tables 1 and 2 into the supplementary materials. A brief introduction to the Materials and Methods is sufficient.

Response to comment 2, R2: We have now moved Table 1 and 2 to Supplementary material as suggested.

Comment 3, R2: The title, analysis content, and data in Table 3 of 3.1.1 should be presented in the same order, such as sugar, ethanol and acid, for the convenience to read.

Response to comment 3, R2: The data, table and title are now in the same order.

Comment 4, R2: The data presented in sections 3.1.1, 3.2.2 and 3.2 of the article were presented in tabular form. For the authors, it’s better to first consider figures to present the data and deliver information.

Response to comment 4, R2: We thank you very much for the suggestion, but after careful consideration, we decided to deliver the data in tables that are the according to our opinion the best presentation of collected database of the case study.

Comment 5, R2: Table 5 should be placed in the appendix, and it does not need to be elaborated too much. In addition, the title of Table 7 should be changed to Table 6.

Response to comment 5, R1: Table 5 are moved to supplementary materials as suggested, and the order of the table is changed.  

Comment 6, R2: To be precise, chlorogenic acid is a derivative of hydroxycinnamic acid, and language expression should be rigorous.

Response to comment 6, R2: We have reformulated the sentence, and now the language is more rigorous, as suggested

Comment 7, R2:  This article has tested the basic physicochemical indicators of the samples and the substances that affect the aroma of apple cider. However, color is also an important component factor affecting its quality. Why did the author not consider detecting the chemical substances that affect the color of apple cider?

Response to comment 7, R2: We totally agree with the suggestion, however in our case study we have focused on chemical parameters that impact taste/aroma, and not colour. Now we cannot improve the manuscript with this parameter, since the samples would now already change the colour due to ageing process. We will include that in our future work about ciders from Hardanger.

Reviewer 3 Report

Comments and Suggestions for Authors

Please see the attachment.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Moderate editing of English language is required,

Author Response

Reviewer nr 3 - Comments and Suggestions for authors from reviewer nr 3 and the authors responses to the comments:

 

Comment 1, R3: Abstract. The authors could add a phrase at the beginning of the abstract as an introducƟon to the theme. Line 22. Please add ‘expressed as gallic acid equivalents”.

Response to comment 1, R3: An introduction sentence has now been added in the beginning of abstract. The missing information are now included in line 16 in brankets following the word Polyphenols.

Comment 2, R3: Keywords. Cider is wriƩen in bold, please correct.

Response to comment 2, R3: The bold font has been removed.

Comment 3, R3: IntroducƟon.· Line 88-89. Please add a reference.

Response to comment 3, R3: We have added the reference in the Introduction text, as suggested.

 

Comment 4, R3: Materials and methods. Line 115. The fermentaƟon temperature range is not clear, is it -12 to 18 oC? Line 117. Please give the full name of YAN.

Response to comment 4, R3: The temperature range is corrected and yeast assimilable nitrogen is included in the text in front of abbreviation YAN.

 

Comment 5, R3: 2.5. GC-MS analyses of volaƟle compounds.  In the descripƟon of GC-MS analysis, please specify the soŌware used for quanƟficaƟon, and how the quanƟficaƟon was performed. Lines 164, 169. Change fibre to fiber.

Response to comment 5, R3: In the materials and method section we have added the information about the software for GC-MS analyses how the quantification has been performed.  We have change Fibre to fiber. We have also explained in more detailes how identification and quantification of analyzed compounds were done and included the data about the software.

Comment 6, R3: 2.7. StaƟsƟcal analysis. Please report the version of the soŌware and the manufacturer’s informaƟon.

Response to comment 6, R3: Ther minitab version is included.

Comment 7, R3: Figures and tables. Table 1 could be moved to supplementary files. Table 3. Please correct “Ɵtratable acid” to “Ɵtratable acidity”. Also, I suggest incorporaƟng the number of samples in the table. Finally, please keep two decimals to all numbers presented in the table. Table 5. Please change the font within the table. Table 5. Please provide a reference for all odor thresholds reported here. Supplementary material. Please provide capƟons for tables and figures. What is the difference between Figure 1 and Supplementary figure?

Response to comment 7, R3: Table 1 (and 2) have now been moved to Supplementary. We have corrected titratable acid to titratable acidity in Table 3.  We have incorporated number of samples in the table, we have double checked the number of decimals and the fonts in the tables. Table 5 is moved to supplementary materials and were moved the descriptor where we could not find the reference. We have now corrected the Captions of tables and figures throughout the text. Figure 1 is polyphenols and figure S1 is aroma.

Comment 8, R3: Results and discussion Lines 262-263. Please rephrase to clarify the meaning. Line 272. Please specify the table for the supplementary material. Lines 291-292. “yeast assimilaƟon by malic acid”. Please correct to “yeast assimilaƟon of malic acid”. Line 312. Please don’t use bold leƩers. Also apply to lines 421-433, 453-454, and Table 7. Line 385. Please change “compound” to “compounds”.

Response to comment 8, R3: The table in supplementary material in the old line 272 is specified. We have rephrased the sentence and improved the meaning in line 262. The phrase “yeast assimilation by malic acid” is changed to “yeast assimilation of malic acid”. We have changed the bold letters in the text, but the bold letters in table indicate values over the threshold limit, and we did not change that. In the old line 385 we changed compound to compounds.

Comment 9, R3: References. References are not appropriately cited, so the whole secƟon should be revised according to the journal’s instrucƟons. I’m not able to discern the rate of self-citaƟon, since references are not appropriately cited.

Response to comment 9, R3:  the citations are now corrected and prepared in the Beverages instruction

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made appropriate revision or explanations. This manuscript may be accepted at its current form.

Comments on the Quality of English Language

good

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all comments and the manuscript has been improved.