Insights into Native Fermentation Process of Apples (Malus domestica) in Low Sodium Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1.There are too many paragraphs in the introduction, and most of the paragraphs have less content. Suggest reorganizing the introduction content to highlight the necessity of apple fermentation and the relationship between the research in this paper.

2.Pay attention to the writing of chemical formulas, especially the subscripts of numbers, for example 2.1, Figure 1-4, Figure 6, Table 3.  MgCl in Figure 5 and Table 2 could be MgCl2. "." was written as "、" in Table 3.

3.Figure 4A is a mirror image.

4.The author analyzed the texture and color of fermented apples, why not analyze the taste of fermented apples? As a food, taste is very important. The author's conclusion is: "Potassium or magnesium chlorides could be used as alternatives to natrium chloride in apples fermentation process.” From the perspective of physical and chemical data analysis, it is possible. However, the taste of magnesium and potassium ions is not so good. How to solve this problem?

Comments on the Quality of English Language

English writing needs further improvement. There are some unprofessional expressions in the paper.

Author Response

Authors answer: The authors thank reviewer for the in deep evaluation of our paper and appropriate suggestions. All the recommended changes are marked in red. Thank you.

Specific comments:

1. There are too many paragraphs in the introduction, and most of the paragraphs have less content. Suggest reorganizing the introduction content to highlight the necessity of apple fermentation and the relationship between the research in this paper.

Authors answer: Thank you for your observation! The text was modified and the changes were marked in red

2. Pay attention to the writing of chemical formulas, especially the subscripts of numbers, for example 2.1, Figure 1-4, Figure 6, Table 3.  MgCl in Figure 5 and Table 2 could be MgCl2. "." was written as "、" in Table 3.

Authors answer: Thank you for your comment! In tables we modified the chemical formulas, as well as the ”.” (they are marked with red color). Unfortunately, in figures, the software we use to generate the graphics does not allow us to introduce subscript letters

3. Figure 4A is a mirror image.

Authors answer: Thank you for your valuable observation! The image has been corrected.

4. The author analyzed the texture and color of fermented apples, why not analyze the taste of fermented apples? As a food, taste is very important. The author's conclusion is: "Potassium or magnesium chlorides could be used as alternatives to natrium chloride in apples fermentation process.” From the perspective of physical and chemical data analysis, it is possible. However, the taste of magnesium and potassium ions is not so good. How to solve this problem?

Authors answer: Thank you for the very good observation! Indeed, potassium and magnesium chloride could influence the taste of the fermented apples: potassim chloride leads to a bitter teaste, while magnesium chloride induces a metallic taste. We accomplished a sensorial analisys, taking into consideration all the sensorial characteristics (including taste), for different salts concentrations (data will be published elsewere) and the conclusion is that, for the concentrations used in this study, the taste modifications are insignificant and do not bother the consumers.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Summary

This manuscript “Insights into native fermentation process of apples (Malus domestica) in low sodium conditions” presents an important and relevant investigation into the effects of sodium chloride substitution with potassium and magnesium chloride during apple fermentation. The work is timely, original, and potentially valuable for the food processing industry, especially in the context of healthier food preservation.

However, there are many inaccuracies and places in the work that require correction or explanation. The chapter on research methods requires improvement, there is no discussion of the results and the conclusions are poor.

General remarks

1. Sections ‘Materials and Methods’, especially 1 to 2.3 are among the weakest parts of the manuscript and require substantial revision. As they currently stand, these subsections are fragmented, uneven in detail, and lacking a scientific narrative.

Section 2.1 ("Reagents and Chemicals") merely lists chemicals and suppliers without linking them to their analytical purpose or experimental steps.

Section 2.2 ("Samples Preparation") is overly detailed in irrelevant places (e.g., spice quantities) but omits crucial experimental context, such as the number of apples used or how many jars/samples were prepared.

Section 2.3 ("Mass Evaluation") is a single sentence and does not justify its separation as a standalone subsection. It could easily be integrated into the broader methods

While the selected analytical methods are appropriate, the methods section requires significant editorial improvement. The structure is confusing and poorly organized. Subsections like “Mass evaluation” are unnecessarily isolated, while others are overloaded with technical detail.

2. Some descriptions are overly detailed (e.g., carotenoid analysis), while others are too brief or incomplete.
3. Some methodologies, like DM, for example, are missing reference values or standards.

 

4. One noticeable issue is the inconsistency in the naming of sections and parameters throughout the manuscript. For example, in the Materials and Methods, the subsection is titled “Concentration of cations”, whereas in the Results and Discussion, it appears as “Metallic ions concentration”. This inconsistency can confuse readers and should be corrected for clarity and coherence. Similar discrepancies appear elsewhere, and aligning terminology across sections would improve the overall professionalism and readability of the paper.

 

5. Another important issue is the inconsistency and incompleteness of the statistical analysis. In some sections, statistical differences are clearly indicated using letters (e.g., in texture or color tables), while in others only standard deviations are shown on graphs, without any indication of significance. Some tables lack any statistical markers altogether. Without consistent use of significance indicators (e.g., letters or p-values), it is difficult to assess whether the observed differences are statistically meaningful. A unified and complete presentation of statistical results is necessary to support the conclusions drawn from the data.

 

6. The discussion throughout the manuscript is rather weak or, in some sections, nearly absent. In particular, the section on dry matter lacks any comparison with findings from the existing literature. The results are described in detail, but there is no critical interpretation or contextualization in relation to previous studies. For a scientific article, it is essential not only to present data but also to explain their relevance and align them with (or contrast them against) what is already known. Strengthening the discussion would significantly improve the scientific value and depth of the manuscript

3.2.1 No discussion.

3.2.2. No real discussion. The authors present data but do not interpret them — e.g. why does MgCl₂ lead to higher acidity and NaCl to lower? What mechanisms might be behind this? No references to more than one work. Only Yousefi et al. [1] appears, and that in general.

The same applies to the remaining results discussions.

 

7. Day ‘0’ appears on several figures (e.g., Figure 2), but there is no mention in the Materials and Methods section of any measurements being taken at this time point. This raises concerns about the consistency and clarity of data presentation. Moreover, some figures include results from day 0, while others begin only from day 7, without explanation. The authors should clarify whether any experimental data were collected on day 0, and if so, describe the procedure. If not, day 0 should be removed from the figures to avoid misleading readers.

 

8. Chapter on Discussion of Results definitely needs serious revision in terms of language, clarity, structure, and scientific expression. The authors present the results but there is no discussion. The conclusions chapter contains a poor summary. The conclusion does not sufficiently reflect the full scope of the study. Important aspects such as changes in mass, texture, sugar content, and mineral ion concentration are entirely omitted, even though they were part of the core analysis. Simply stating that “the quality characteristics show similar tendencies” is vague and fails to highlight the specific differences observed between the brines. The conclusion should be rewritten to better reflect the results of the study and to express future directions in a clear, grammatically correct, and scientifically specific way.

 

9. The manuscript is written with grammatical errors, the language needs improvement.

 

Specific remarks

Line 100: ‘weighed’ instead of ‘weighted’

Line 101: "every 7 days" or "at 7-day intervals" instead of "at every 7 days"

Line 238: The expression "the process speed was too low to be noticed at 'macro' level" is awkward and too informal for a scientific article.  

• "process speed" sounds colloquial; it would be more appropriate to use "rate of the process" or "fermentation rate" in academic writing.
• "to be noticed at 'macro' level" is vague and lacks scientific clarity — it is unclear whether this refers to visible changes, weight, or another parameter.
• The use of quotation marks around "macro" suggests uncertainty or a non-standard term, which is not suitable in a formal context.

Line 247: rather, the authors mean reverse osmosis, which is not appropriate to describe the phenomenon present here. Reverse osmosis typically refers to a pressure-driven filtration process in membranes, not passive brine uptake. More accurate would be: “...may be explained by diffusion-driven uptake of brine components into the apple tissue.”

Line 248-249: The sentence “Similar results were reported in other studies on sauerkraut [22] or black garlic [23]” is too vague. It would be more informative to specify which particular results or trends are being referred to.

Line 253: ‘textural properties’ instead of ‘texture properties’

Lines 257-258: “value...value” — avoid redundancy (better version: “Dry matter content decreased by 26.17%, reaching 10.62 ± 0.19 g/100 g product.”)

Line 276: ‘from’ instead of ‘form’

Line 277: “All pickle samples” or “All samples of pickled apples” instead of  ‘All pickles samples’

Line 282: “increased by 30.5%” instead of ‘“increased with 30.5%”

Line 288: “brine” alone is enough, no need to add “solution”

Fig.4a: inverted graph, mirror image

Line 314: “directly reducing carbohydrates” – uncommon and awkward phrasing; better to say “reducing sugars”

Line 316: but also sugars” – redundant with “carbohydrates” and unclear; this phrase needs reworking

Lines 317-318: “carbohydrates, directly reducing carbohydrates and sugars” – this sounds redundant and confusing

Line 323: again, “directly reducing carbohydrates” is not standard phrasing

Line 332: “variation of their concentrations” better as “changes in concentration”

Line 333: “that is” is informal

Lines 334-335: awkward phrasing

Line 338: “Allure” is an inappropriate and non-scientific word here

Lines 338-348: Sentence is fragmented, and logic is hard to follow

Line: 353: the term "Metallic ions concentration” is used here, while earlier in the methods section the term was “Concentration of cations.”

Line 388: "Even" is incorrectly used, and "vegetal" is a false using — better to use "plant sources."

Page 15: different paragraph spacing

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The language throughout the manuscript is generally weak and in need of thorough revision. It contains numerous grammatical errors, awkward phrasing, and inconsistent terminology that reduce the clarity and professionalism of the scientific content.

Author Response

Authors answer: The authors thank reviewer for the in deep evaluation of our paper and appropriate suggestions. All the recommended changes are marked in red. Thank you.

1. Sections ‘Materials and Methods’, especially 1 to 2.3 are among the weakest parts of the manuscript and require substantial revision. As they currently stand, these subsections are fragmented, uneven in detail, and lacking a scientific narrative.

Section 2.1 ("Reagents and Chemicals") merely lists chemicals and suppliers without linking them to their analytical purpose or experimental steps.

Authors answer: Thank you for your observation! All the recommended changes are marked in the text with red.

Section 2.2 ("Samples Preparation") is overly detailed in irrelevant places (e.g., spice quantities) but omits crucial experimental context, such as the number of apples used or how many jars/samples were prepared.

Authors answer: Thank you for your observation! The text was modified taking into consideration your recommendation and the recommendations of the other reviewers. The modifications are marked in red.

Section 2.3 ("Mass Evaluation") is a single sentence and does not justify its separation as a standalone subsection. It could easily be integrated into the broader methods

While the selected analytical methods are appropriate, the methods section requires significant editorial improvement. The structure is confusing and poorly organized. Subsections like “Mass evaluation” are unnecessarily isolated, while others are overloaded with technical detail.

Authors answer: Thank you for your observation!  The method for mass evaluation was introduced in section 2.3. Physical and chemical analysis.

1. Some descriptions are overly detailed (e.g., carotenoid analysis), while others are too brief or incomplete.

Authors answer: Thank you for your observation! The text has been changed

1. Some methodologies, like DM, for example, are missing reference values or standards.

Authors answer: Thank you for your observation! All these information are given at Lines 107 – 108: The dry matter was carried out according to ISO 1026:1982

1. One noticeable issue is the inconsistency in the naming of sections and parameters throughout the manuscript. For example, in the Materials and Methods, the subsection is titled “Concentration of cations”, whereas in the Results and Discussion, it appears as “Metallic ions concentration”. This inconsistency can confuse readers and should be corrected for clarity and coherence. Similar discrepancies appear elsewhere, and aligning terminology across sections would improve the overall professionalism and readability of the paper.

Authors answer: Thank you for your remark! We modified the text and the changes are marked in red.

1. Another important issue is the inconsistency and incompleteness of the statistical analysis. In some sections, statistical differences are clearly indicated using letters (e.g., in texture or color tables), while in others only standard deviations are shown on graphs, without any indication of significance. Some tables lack any statistical markers altogether. Without consistent use of significance indicators (e.g., letters or p-values), it is difficult to assess whether the observed differences are statistically meaningful. A unified and complete presentation of statistical results is necessary to support the conclusions drawn from the data.

Authors answer: Thank you for your remark! All the data were statistically analyzed. Comparations ware made using Tukey’s test. The significance level was set at 5%.

 

1. The discussion throughout the manuscript is rather weak or, in some sections, nearly absent. In particular, the section on dry matter lacks any comparison with findings from the existing literature. The results are described in detail, but there is no critical interpretation or contextualization in relation to previous studies. For a scientific article, it is essential not only to present data but also to explain their relevance and align them with (or contrast them against) what is already known. Strengthening the discussion would significantly improve the scientific value and depth of the manuscript

Authors answer: Thank you for your remark! We modified the text and the changes are marked in red.

3.2.1 No discussion.

Authors answer: Thank you for your remark! The information exist in the manuscript, as follow:

Line 274 – 281: Dry matter content decreased by 26.17%, reaching 10.62 ± 0.19 g/100 g product. This reduction in dry matter content could be due to lactic acid bacteria utilizing the carbohydrates, minerals and other components necessary for their development during the fermentation period. After 28 days of fermentation, the dry matter for all samples started to increase. The reason for this increase could be the difference in osmotic pressure that exists between the saline solution and the fermented plant material, respectively due to the mass transfer that occurs by diffusion.

 

3.2.2. No real discussion. The authors present data but do not interpret them — e.g. why does MgCl₂ lead to higher acidity and NaCl to lower? What mechanisms might be behind this? No references to more than one work. Only Yousefi et al. [1] appears, and that in general.

Authors answer: Thank you for your remark! The information was introduced in the manuscript, as follow:

Line 297 – 301: The difference in titratable acidity may also come from the nature of the cations (Mg²⁺ vs. Na⁺) and their interaction with water. It is possible that MgCl₂ inhibit the lactic acid bacteria resulting in a higher titratable acidity while the NaCl tends to slow down the lactic acid fermentation process, leading a lower titratable acidity.

Line 306 – 308: The values of acidity could be explained by the evolution of lactic bacteria, which registered a rapid development in the first 14 days, followed by stagnation and decrease as presented in a previous study [16].

The same applies to the remaining results discussions.

1. Day ‘0’ appears on several figures (e.g., Figure 2), but there is no mention in the Materials and Methods section of any measurements being taken at this time point. This raises concerns about the consistency and clarity of data presentation. Moreover, some figures include results from day 0, while others begin only from day 7, without explanation. The authors should clarify whether any experimental data were collected on day 0, and if so, describe the procedure. If not, day 0 should be removed from the figures to avoid misleading readers.

Authors answer: Thank you for your observation! Aditional explanations, marked in red, were included into the manuscript.

1. Chapter on Discussion of Results definitely needs serious revision in terms of language, clarity, structure, and scientific expression. The authors present the results but there is no discussion. The conclusions chapter contains a poor summary. The conclusion does not sufficiently reflect the full scope of the study. Important aspects such as changes in mass, texture, sugar content, and mineral ion concentration are entirely omitted, even though they were part of the core analysis. Simply stating that “the quality characteristics show similar tendencies” is vague and fails to highlight the specific differences observed between the brines. The conclusion should be rewritten to better reflect the results of the study and to express future directions in a clear, grammatically correct, and scientifically specific way.

Authors answer: Thank you for your observation! The text was modified and the changes were marked in red.

1. The manuscript is written with grammatical errors, the language needs improvement.

Specific remarks

Line 100: ‘weighed’ instead of ‘weighted’

Authors answer: Thank you for your observation! The text has been changed

Line 101: "every 7 days" or "at 7-day intervals" instead of "at every 7 days"

Authors answer: Thank you for your observation! The text has been changed

Line 238: The expression "the process speed was too low to be noticed at 'macro' level" is awkward and too informal for a scientific article.  

• "process speed" sounds colloquial; it would be more appropriate to use "rate of the process" or "fermentation rate" in academic writing.
• "to be noticed at 'macro' level" is vague and lacks scientific clarity — it is unclear whether this refers to visible changes, weight, or another parameter.
• The use of quotation marks around "macro" suggests uncertainty or a non-standard term, which is not suitable in a formal context.

Authors answer: Thank you for your observation! The text has been changed

Line 247: rather, the authors mean reverse osmosis, which is not appropriate to describe the phenomenon present here. Reverse osmosis typically refers to a pressure-driven filtration process in membranes, not passive brine uptake. More accurate would be: “...may be explained by diffusion-driven uptake of brine components into the apple tissue.”

Authors answer: Thank you for your observation! The text has been changed

Line 248-249: The sentence “Similar results were reported in other studies on sauerkraut [22] or black garlic [23]” is too vague. It would be more informative to specify which particular results or trends are being referred to.

Authors answer: Thank you for your observation! The text has been changed

Line 253: ‘textural properties’ instead of ‘texture properties’

Authors answer: Thank you for your observation! The text has been changed

Lines 257-258: “value...value” — avoid redundancy (better version: “Dry matter content decreased by 26.17%, reaching 10.62 ± 0.19 g/100 g product.”)

Authors answer: Thank you for your observation! The text has been changed

Line 276: ‘from’ instead of ‘form’

Authors answer: Thank you for your observation! The text has been changed

Line 277: “All pickle samples” or “All samples of pickled apples” instead of  ‘All pickles samples’

Authors answer: Thank you for your observation! The text has been changed

Line 282: “increased by 30.5%” instead of ‘“increased with 30.5%”

Authors answer: Thank you for your observation! The text has been changed

Line 288: “brine” alone is enough, no need to add “solution”

Authors answer: Thank you for your observation! We removed “solution”

Fig.4a: inverted graph, mirror image

Authors answer: Thank you for your observation! We corrected the image.

Line 314: “directly reducing carbohydrates” – uncommon and awkward phrasing; better to say “reducing sugars”

Authors answer: Thank you for your observation! We deleted “directly”.

Line 316: but also sugars” – redundant with “carbohydrates” and unclear; this phrase needs reworking

Authors answer: Thank you for your observation! We deleted the redundant words.

Lines 317-318: “carbohydrates, directly reducing carbohydrates and sugars” – this sounds redundant and confusing

Authors answer: Thank you for your observation! We deleted the redundant words.

Line 323: again, “directly reducing carbohydrates” is not standard phrasing

Authors answer: Thank you for your observation! We deleted “directly”.

Line 332: “variation of their concentrations” better as “changes in concentration”

Authors answer: Thank you for your observation! The text has been changed.

Line 333: “that is” is informal

Authors answer: Thank you for your observation! We deleted “that is”.

Lines 334-335: awkward phrasing

Authors answer: Thank you for your observation! The text has been changed.

Line 338: “Allure” is an inappropriate and non-scientific word here

Authors answer: Thank you for your observation! We changed “allure” with  “aspect”.

Lines 338-348: Sentence is fragmented, and logic is hard to follow

Authors answer: Thank you for your observation! The text has been changed.

Line: 353: the term "Metallic ions concentration” is used here, while earlier in the methods section the term was “Concentration of cations.”

Authors answer: Thank you for your observation! The text has been changed.

Line 388: "Even" is incorrectly used, and "vegetal" is a false using — better to use "plant sources."

Authors answer: Thank you for your observation! The text has been changed.

Page 15: different paragraph spacing

Authors answer: Thank you for your observation! The paragraph spacing has been changed.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors investigated the effects of  potassium or magnesium chloride instaed of sodium chloride on the pickling process of apples. In general many characterization have been presented, but I suggest the following revision to improve the manuscript.

• the english is not good quality, please review all the language
• the introduction is dispersive and don't explain the context of the paper purpose. the rationale of the work is not clear.
• the purpose of the paper is not very clear. Try to explain better the main aim of the work
• the procedure in materials and methods must be more detailed (procedure and data analysis)
• in the results section a paragraph that explain and compare all the results should be added to better clarify and discuss all data and why the KCl and MgCl₂ are better then NaCl
• improve the conclusion section
• 36 natrium choride is sodium chloride
• line 91 how it was sterilized?
• line 136 correct with °C
• line 162 correct Na₂CO₃
• line 162 normally the Folin-Ciocalteau procedure is different. Less reagent is used and the incubation is at 40°C for 30 min. Can you have a picture of the calibration curve with gallic acid to see the color-change from yellow to blue? in addition you must explicitate the concentration level of calibration curve.
• line 170 correct NaNO₂
• line 173 concentration level of the calibration curve?
• line 177-186 it is not clear how you determine the amount of the cartenoids and chlorophyll. the procedure must be improved with more details
• figure 1 should be implemented: statistical differences are not shown. Also differences at same check point but different salt should be underlined by statistical analysis
• line 293 natrium must be sodium
• for the color analysis it is better to report graphic change of deltaE during time. So e figure must be added
• in all text natrium chloride must be sodium chloride
•  

Author Response

Authors answer: The authors thank reviewer for the in deep evaluation of our paper and appropriate suggestions. All the recommended changes are marked in red. Thank you.

• the english is not good quality, please review all the language

Authors answer: Thank you for your observation! The text was modified and the changes were marked in red

• the introduction is dispersive and don't explain the context of the paper purpose. the rationale of the work is not clear.

Authors answer: Thank you for your observation! The text was modified and the changes were marked in red

• the purpose of the paper is not very clear. Try to explain better the main aim of the work

Authors answer: Thank you for your observation! The text was modified and the changes were marked in red

• procedure in materials and methods must be more detailed (procedure and data analysis)

Authors answer: Thank you for your observation! The text was modified.

• in the results section a paragraph that explain and compare all the results should be added to better clarify and discuss all data and why the KCl and MgCl₂ are better then NaCl

Authors answer: Thank you for your observation! The text was modified.

• improve the conclusion section

Authors answer: Thank you for your remark! The text has been changed.

• 36 natrium choride is sodium chloride

Authors answer: Thank you for your remark! The text has been changed.

• line 91 how it was sterilized?

Authors answer: Thank you for your remark! ”by introducing into a hot air oven (150°C) for 15 minutes” was introduced into manuscript and marked in red.

• line 136 correct with °C

Authors answer: Thank you for your remark! The text has been changed.

• line 162 correct Na₂CO₃

Authors answer: Thank you for your remark! The text has been changed.

• line 162 normally the Folin-Ciocalteau procedure is different. Less reagent is used and the incubation is at 40°C for 30 min. Can you have a picture of the calibration curve with gallic acid to see the color-change from yellow to blue? in addition you must explicitate the concentration level of calibration curve.

Authors answer: Thank you for your remark! We have completed the requested information in the text, the method is correct, more over there are many other researchers that reported this method.

• line 170 correct NaNO₂

Authors answer: Thank you for your remark! The text has been changed.

• line 173 concentration level of the calibration curve?

Authors answer: Thank you for your remark! The information was completed.

• line 177-186 it is not clear how you determine the amount of the cartenoids and chlorophyll. the procedure must be improved with more details

Authors answer: Thank you for your remark! The method was clarified in the manuscript.

• figure 1 should be implemented: statistical differences are not shown. Also differences at same check point but different salt should be underlined by statistical analysis

Authors answer: Thank you for your remark! Figure 1 was modified.

• line 293 natrium must be sodium

Authors answer: Thank you for your remark! The text has been changed.

• for the color analysis it is better to report graphic change of deltaE during time. So e figure must be added

Authors answer: Thank you for your remark! We included Figure 6. Total color difference (ΔE) in the apple pickle fermentation with different brine solutions in the article.

• in all text natrium chloride must be sodium chloride

Authors answer: Thank you for your remark! The text has been changed.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The issue has been effectively addressed.

Author Response

Thank you for your remark.

Kind regars, 

The authors

Reviewer 2 Report

Comments and Suggestions for Authors

The revised manuscript shows that the authors have implemented the suggested improvements. The paper is now more coherent and readable, and the analytical methods are better described. However, the discussion of the results is still somewhat superficial in my opinion, but is acceptable. However, the conclusions should be further improved to reflect the key findings in more detail, to highlight the differences between salt types (mass, texture, ions, bioactive compounds - all of which were studied but not included in the conclusions, and to lack an indication of the key differences between salts: which parameters were most sensitive to salt substitution) and to suggest directions for future research. 

Comments on the Quality of English Language

The language of the manuscript has improved, but it still requires further editing for clarity, conciseness, and scientific tone to meet the standards of a high-quality journal.

Author Response

Authors answer: The authors thank reviewer for the in deep evaluation of our paper and appropriate suggestions. All the recommended changes are marked in blue. Thank you.

Specific comments:

The revised manuscript shows that the authors have implemented the suggested improvements. The paper is now more coherent and readable, and the analytical methods are better described. However, the discussion of the results is still somewhat superficial in my opinion, but is acceptable. However, the conclusions should be further improved to reflect the key findings in more detail, to highlight the differences between salt types (mass, texture, ions, bioactive compounds - all of which were studied but not included in the conclusions, and to lack an indication of the key differences between salts: which parameters were most sensitive to salt substitution) and to suggest directions for future research. 

Authors answer: Thank you for your observation! All these information are given at Lines 578-584: The dry matter content initially decreased for all samples until the 28^th day and then increased due to osmotic pressure that exists between the saline solution and the fermented apples. The TA value significantly increased and reached the highest values in the final phase of fermentation (after the 35^th days). In contrast, the levels of reducing sugars and uronic acids content decreased for all the samples. This aspect can be explained by the different adaptation capacity and metabolic activity of the microorganisms involved in the fermentation process. 

and

Lines 586 – 593: The present study indicates that pickling process where NaCl was substituted by KCl or MgCl₂ has beneficial effects on the concentration of bioactive compounds of fermented apples. The results revealed that these substitutions can increase the levels of carotenoids, TPC, TFC and chlorophyll. The results of textural analysis indicated that the KCl produced small changes on the textural characteristics of brine-pickled apples compared to NaCl or MgCl₂. Color parameters of all brine-pickled apple samples decreased during pickling process.

Author Response File: Author Response.docx