ε-Poly-l-lysine Suppressed Decay Development and Maintained Storage Quality in Guava Fruit by ROS Level Regulation and Antioxidant Ability Enhancement

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents several interesting scientific findings. However, the author is required to revise the following information prior to publication:

To ensure the homogeneity of the guava material, the author must provide detailed information such as the age of the guava trees and the methods used to guarantee the uniformity of fruit quality.

The discussion section requires a more in-depth presentation to highlight the novelty of this research, specifically:

1. The author needs to discuss the efficacy of the ε-PL treatment in greater detail.
2. The author needs to provide a more comprehensive discussion of the mechanism of ε-PL (Figure 8).
3. A comparative analysis with similar studies is necessary, including a comparison of the duration for which ε-PL treatment can extend the quality of guava fruit.

The conclusion section must explicitly affirm the effectiveness of the ε-PL treatment.

Author Response

Comment 1: To ensure the homogeneity of the guava material, the author must provide detailed information such as the age of the guava trees and the methods used to guarantee the uniformity of fruit quality.

Answer: Thanks the reviewer’s comment. We have referred to the academic papers concerning postharvest chemistry and biochemistry including our research papers, which are published in academic journals such as Food Chemistry: X and International Journal of Biological Macromolecules, and the relevant information of pericarp chromaticity L^* and a^* values, and pulp total soluble solids content on storage day 0 were supplemented in the new version (See Line 87-89). This supplemented information can be used to ensure the homogeneity of the guava material.

Comment 2: The author needs to discuss the efficacy of the ε-PL treatment in greater detail.

Answer: Thanks the reviewer’s comment. We have added the related information in the new version (See Line 69-71, Line 392-397, Line 445-446, Line 453-457, Line 475-479).

Comment 3: The author needs to provide a more comprehensive discussion of the mechanism of ε-PL (Figure 8).

Answer: Thanks the reviewer’s comment. We have added in the new version (See Line 453-457).

Comment 4: A comparative analysis with similar studies is necessary, including a comparison of the duration for which ε-PL treatment can extend the quality of guava fruit.

Answer: Thanks the reviewer’s comment. The manuscript has contained a comparative analysis with similar studies (See Line 365-368, Line 376-379, Line 387-391, Line 397-399 Line 417-421, Line 447-450). Besides, we have added a comparison of the duration that ε-PL treatment extends the quality-maintaining period of guava fruit (See Line 397-399).

Comment 5: The conclusion section must explicitly affirm the effectiveness of the ε-PL treatment.

Answer: Thanks the reviewer’s comment. We have added in the new version (See Line 475-479).

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for submitting the manuscript entitled “Effects of ε-poly-L-lysine on suppressing decay development and stabilizing storage quality in guava fruit by enhancing its antioxidant ability.” I have carefully reviewed your work and found it of scientific merit. The topic is timely, given the importance of reducing postharvest losses in climacteric fruits. Your study demonstrates that ε-poly-L-lysine, especially at 2 g/L, effectively reduces the decay index, maintains fruit quality parameters, and enhances antioxidant systems in guava.

Overall, the methodology is appropriate, and the data supports your conclusions. I recommend implementing minor revisions to address the following points:

Please clarify in the Materials and Methods how many biological replicates (bags/batches of fruit) were used for each parameter and whether the experiment was performed more than once (e.g., two harvests from the same orchard or different seasons). Specify how fruit were assigned to treatments in a randomized design if applicable.

Add brief information on orchard conditions (e.g., region, temperature, agronomic practices) or harvest season. Such contextual details help readers interpret the applicability of your findings to other growing regions.

A final proofreading would ensure grammatical consistency. The manuscript is largely clear, but small errors in verb tense and prepositions appear occasionally.

In the Results, vitamin C first decreases and then increases in later storage days. Briefly elaborate on physiological or analytical reasons for this fluctuation, referencing prior studies or known guava physiology where relevant.

Consider adding a bit more context comparing your findings on sugars and color changes with other postharvest studies in guava or similar tropical fruits, reinforcing the novelty of ε-PL application.

Additionally, we have noticed that many of the cited studies are authored by researchers affiliated with the same group, even if they do not share identical authorship. While it is legitimate to reference previous work from one’s own laboratory to provide scientific continuity, an overreliance on such citations may be perceived as self-promotion and could undermine the broader scholarly context. We recommend balancing citations of your group’s work with publications from independent sources to further substantiate your findings and reinforce the manuscript’s overall credibility.

By incorporating these improvements, your manuscript will be further strengthened for publication. Thank you again for your submission, and I look forward to seeing your revised version.

Sincerely.

Comments on the Quality of English Language

Must be improved

Author Response

Comment 1: Dear authors, thank you for submitting the manuscript entitled “Effects of ε-poly-L-lysine on suppressing decay development and stabilizing storage quality in guava fruit by enhancing its antioxidant ability.” I have carefully reviewed your work and found it of scientific merit. The topic is timely, given the importance of reducing postharvest losses in climacteric fruits. Your study demonstrates that ε-poly-L-lysine, especially at 2 g/L, effectively reduces the decay index, maintains fruit quality parameters, and enhances antioxidant systems in guava.

Overall, the methodology is appropriate, and the data supports your conclusions. I recommend implementing minor revisions to address the following points.

Answer: Thanks the reviewer’s comment.

Comment 2: Please clarify in the Materials and Methods how many biological replicates (bags/batches of fruit) were used for each parameter and whether the experiment was performed more than once (e.g., two harvests from the same orchard or different seasons). Specify how fruit were assigned to treatments in a randomized design if applicable.

Answer: Thanks the reviewer’s comment. In this manuscript, one batch, i.e. 30 samples, was chosen to measure fruit’s attributes on 0 d. The other batch (600 fruit) were separated into four groups with 150 each. There were 3 replications in each group with 50 samples each replication. The relevant repeated descriptions have added in the new manuscript (See Line 92-94). Besides, the all indices are measured three times (See Line 165). Furthermore, the samples used in the experiments on the effects of different concentrations of ε-PL on fruit quality and the antioxidant experiments all came from the guava fruit harvested during the same period, that is, the guava fruit is harvested only once.

Comment 3: Add brief information on orchard conditions (e.g., region, temperature, agronomic practices) or harvest season. Such contextual details help readers interpret the applicability of your findings to other growing regions.

Answer: Thanks the reviewer’s comment. The fruit of guava cv. Xiguahong from orchard in Luoxi Town, Fujian, China, was picked during its commercial maturity stage in the summer. This orchard is commercial orchard, and its planting management is in line with commercial and suitable market needs (See Line 85-87).

Comment 4: A final proofreading would ensure grammatical consistency. The manuscript is largely clear, but small errors in verb tense and prepositions appear occasionally.

Answer: Thanks the reviewer’s comment. We have revised the whole manuscript carefully and tried to avoid any grammar or syntax error. In addition, we had invited the native English speaker to review this manuscript, and avoided any mistakes of tense, grammar and syntax in the new version. We believe that the language is now acceptable for the review process (See the new version).

Comment 5: In the Results, vitamin C first decreases and then increases in later storage days. Briefly elaborate on physiological or analytical reasons for this fluctuation, referencing prior studies or known guava physiology where relevant.

Answer: Thanks the reviewer’s comment. The vitamin C could be used as ROS scavenger, and the increased vitamin C content might be caused by rapid rise of ROS levels, thus delaying ROS-induced oxidative damages, retaining membrane structure, and preserving quality of guava fruit. The underlying causes of elevation of vitamin C level will be further studied (See Line 269-273).

Comment 6: Consider adding a bit more context comparing your findings on sugars and color changes with other postharvest studies in guava or similar tropical fruits, reinforcing the novelty of ε-PL application.

Answer: Thanks the reviewer’s comment. We have added some discussion and compared our results with other previously researches concerning the presented parameters (See Line 376-379, Line 389-391).

Comment 7: Additionally, we have noticed that many of the cited studies are authored by researchers affiliated with the same group, even if they do not share identical authorship. While it is legitimate to reference previous work from one’s own laboratory to provide scientific continuity, an overreliance on such citations may be perceived as self-promotion and could undermine the broader scholarly context. We recommend balancing citations of your group’s work with publications from independent sources to further substantiate your findings and reinforce the manuscript’s overall credibility.

Answer: Thanks the reviewer’s comment. We have revised the manuscript (See the new version).

Comment 8: By incorporating these improvements, your manuscript will be further strengthened for publication. Thank you again for your submission, and I look forward to seeing your revised version.

Answer: Thanks the reviewer’s comment. We have revised the manuscript (See the new version).

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents a well-structured study investigating the effects of ε-poly-L-lysine (ε-PL) on the postharvest storage quality of guava fruit. The research is relevant, addressing an important issue in food preservation and postharvest fruit management. The experimental design is sound, and the statistical analyses appear appropriate for the data presented. However, there are several areas where improvements are necessary, including the clarity of language, a more detailed discussion on mechanisms, and the justification for certain methodological choices.

 

Specific Comments:

1. Title and Abstract

• The title is informative but could be refined for conciseness. Suggestion: "Enhancing Guava Fruit Storage Quality and Decay Resistance Using ε-poly-L-lysine: Effects on Antioxidant Activity."
• The abstract provides a clear summary of the study; however, some sentences lack clarity due to grammatical issues. Consider revising for readability, especially the phrase "Results displayed that ε-PL suppressed storability losses and improved quality in guavas, accompanied by better appearance quality..."
• The conclusion should explicitly mention the practical implications of ε-PL treatment in commercial applications.

2. Introduction

• The introduction sufficiently establishes the problem and the significance of the study. However, it lacks a critical discussion of previous studies using ε-PL in similar postharvest treatments.
• Some background statements are overly general. For example, "Guava is an important economic crop widely planted in subtropical or tropical regions." Consider specifying global production statistics or referencing key studies on guava postharvest challenges.

3. Materials and Methods

• The methodology is generally well-detailed, but additional clarification is needed:
• The selection criteria for guava fruits should be more explicitly stated. Were there size, weight, or maturity index standards applied?
• The reason for selecting 2 g/L as the optimal ε-PL concentration should be justified earlier in the manuscript.
• The duration and environmental conditions of the storage experiment are well described, but details on microbial assessment (if any) could strengthen the discussion on decay suppression.
• The statistical methods should specify which tests were applied for post-hoc comparisons (e.g., Duncan’s multiple range test).

4. Results and Discussion

• The discussion should be improved by:
• Providing a more mechanistic explanation of how ε-PL enhances antioxidant enzyme activities. While the study shows an increase in SOD, POD, and CAT activities, the biochemical pathways or genetic factors involved are not explored.
• Comparing findings with existing literature. Several references are cited, but direct comparisons with previous studies on similar treatments in guava or other fruits are lacking.
• Including a subsection on practical implications for food industries. How does ε-PL compare with other conventional preservation methods?

5. Conclusion

• The conclusion effectively summarizes the key findings but lacks a strong statement on future research directions.
• A recommendation for testing ε-PL in commercial supply chains or under varying storage conditions would enhance the impact of the study.

Comments on the Quality of English Language

The manuscript presents a well-structured study investigating the effects of ε-poly-L-lysine (ε-PL) on the postharvest storage quality of guava fruit. The research is relevant, addressing an important issue in food preservation and postharvest fruit management. The experimental design is sound, and the statistical analyses appear appropriate for the data presented. However, there are several areas where improvements are necessary, including the clarity of language, a more detailed discussion on mechanisms, and the justification for certain methodological choices.

 

Specific Comments:

1. Title and Abstract

• The title is informative but could be refined for conciseness. Suggestion: "Enhancing Guava Fruit Storage Quality and Decay Resistance Using ε-poly-L-lysine: Effects on Antioxidant Activity."
• The abstract provides a clear summary of the study; however, some sentences lack clarity due to grammatical issues. Consider revising for readability, especially the phrase "Results displayed that ε-PL suppressed storability losses and improved quality in guavas, accompanied by better appearance quality..."
• The conclusion should explicitly mention the practical implications of ε-PL treatment in commercial applications.

2. Introduction

• The introduction sufficiently establishes the problem and the significance of the study. However, it lacks a critical discussion of previous studies using ε-PL in similar postharvest treatments.
• Some background statements are overly general. For example, "Guava is an important economic crop widely planted in subtropical or tropical regions." Consider specifying global production statistics or referencing key studies on guava postharvest challenges.

3. Materials and Methods

• The methodology is generally well-detailed, but additional clarification is needed:
• The selection criteria for guava fruits should be more explicitly stated. Were there size, weight, or maturity index standards applied?
• The reason for selecting 2 g/L as the optimal ε-PL concentration should be justified earlier in the manuscript.
• The duration and environmental conditions of the storage experiment are well described, but details on microbial assessment (if any) could strengthen the discussion on decay suppression.
• The statistical methods should specify which tests were applied for post-hoc comparisons (e.g., Duncan’s multiple range test).

4. Results and Discussion

• The discussion should be improved by:
• Providing a more mechanistic explanation of how ε-PL enhances antioxidant enzyme activities. While the study shows an increase in SOD, POD, and CAT activities, the biochemical pathways or genetic factors involved are not explored.
• Comparing findings with existing literature. Several references are cited, but direct comparisons with previous studies on similar treatments in guava or other fruits are lacking.
• Including a subsection on practical implications for food industries. How does ε-PL compare with other conventional preservation methods?

5. Conclusion

• The conclusion effectively summarizes the key findings but lacks a strong statement on future research directions.
• A recommendation for testing ε-PL in commercial supply chains or under varying storage conditions would enhance the impact of the study.

Author Response

Comment 1: The manuscript presents a well-structured study investigating the effects of ε-poly-L-lysine (ε-PL) on the postharvest storage quality of guava fruit. The research is relevant, addressing an important issue in food preservation and postharvest fruit management. The experimental design is sound, and the statistical analyses appear appropriate for the data presented. However, there are several areas where improvements are necessary, including the clarity of language, a more detailed discussion on mechanisms, and the justification for certain methodological choices.

Answer: Thanks the reviewer’s comment.

Comment 2: The title is informative but could be refined for conciseness. Suggestion: "Enhancing Guava Fruit Storage Quality and Decay Resistance Using ε-poly-L-lysine: Effects on Antioxidant Activity."

Answer: Thanks the reviewer’s comment. Regarding title, we have referred to the academic papers concerning postharvest chemistry and biochemistry including our research papers, which are published in academic journals such as Food Chemistry, Food Chemistry: X and International Journal of Biological Macromolecules. We have revised the title further in the new manuscript (See the Title).

Comment 3: The abstract provides a clear summary of the study; however, some sentences lack clarity due to grammatical issues. Consider revising for readability, especially the phrase "Results displayed that ε-PL suppressed storability losses and improved quality in guavas, accompanied by better appearance quality..."

Answer: Thanks the reviewer’s comment. We have revised in the new manuscript (See the Abstract).

Comment 4: In abstract, the conclusion should explicitly mention the practical implications of ε-PL treatment in commercial applications.

Answer: Thanks the reviewer’s comment. We have revised in the new manuscript (See Line 24-26).

Comment 5: In Introduction, the introduction sufficiently establishes the problem and the significance of the study. However, it lacks a critical discussion of previous studies using ε-PL in similar postharvest treatments.

Answer: Thanks the reviewer’s comment. We have revised the relevant contents in the new manuscript (See Line 68-72).

Comment 6: In Introduction, some background statements are overly general. For example, "Guava is an important economic crop widely planted in subtropical or tropical regions." Consider specifying global production statistics or referencing key studies on guava postharvest challenges.

Answer: Thanks the reviewer’s comment. We have revised the relevant contents in the new manuscript (See Line 31-33, Line 35-38).

Comment 7: The selection criteria for guava fruits should be more explicitly stated. Were there size, weight, or maturity index standards applied?

Answer: Thanks the reviewer’s comment. We have added the relevant contents in the new manuscript (See Line 88-91).

Comment 8: The reason for selecting 2 g/L as the optimal ε-PL concentration should be justified earlier in the manuscript.

Answer: Thanks the reviewer’s comment. We have added the relevant contents in the new manuscript (See Line 100-101).

Comment 9: The duration and environmental conditions of the storage experiment are well described, but details on microbial assessment (if any) could strengthen the discussion on decay suppression.

Answer: Thanks the reviewer’s comment. In our prior investigation, Neopetrichoides claviculata was identified as one of the primary pathogens causing guava fruit disease. However, the disease incidence resulting from N. claviculata infection is not the focus of our study, and thus not address here. Additionally, the internal mechanisms of fruit disease caused by N. claviculata infection will be further exploration.

Comment 10: The statistical methods should specify which tests were applied for post-hoc comparisons (e.g., Duncan’s multiple range test).

Answer: Thanks the reviewer’s comment. The relevant statistical methods have reflected in the manuscript. The one-way analysis of variance and Duncan’s tests are adopted for assay (See Line 166-168).

Comment 11: Providing a more mechanistic explanation of how ε-PL enhances antioxidant enzyme activities. While the study shows an increase in SOD, POD, and CAT activities, the biochemical pathways or genetic factors involved are not explored.

Answer: Thanks the reviewer’s comment. We have added the relevant contents in the new manuscript (See Line 431-436).

Comment 12: Comparing findings with existing literature. Several references are cited, but direct comparisons with previous studies on similar treatments in guava or other fruits are lacking.

Answer: Thanks the reviewer’s comment. We have revised the relevant contents in the new manuscript (See Line 365-368, Line 376-379, Line 387-391, Line 397-399 Line 417-421, Line 447-450).

Comment 13: Including a subsection on practical implications for food industries. How does ε-PL compare with other conventional preservation methods?

Answer: Thanks the reviewer’s comment. We have added the relevant contents in the new manuscript (See Line 476-480).

Comment 14: The conclusion effectively summarizes the key findings but lacks a strong statement on future research directions.

Answer: Thanks the reviewer’s comment. We have added the relevant contents in the new manuscript (See Line 458-462).

Comment 15: A recommendation for testing ε-PL in commercial supply chains or under varying storage conditions would enhance the impact of the study.

Answer: Thanks the reviewer’s comment. I agree with your suggestion. In the future, we will adopt your valuable opinions to for testing ε-PL in commercial supply chains or under varying storage conditions to improve the postharvest quality of guava fruit.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript has been revised according to the suggestions provided. I believe it is now ready for publication in its current form.

Author Response

Thanks the reviewer’s comment. 

Reviewer 3 Report

Comments and Suggestions for Authors

The paper has been modified according to the requirements.

Author Response

Thanks the reviewer’s comment.