High-Pressure Processing of Reduced Salt Pangasius Catfish (Pangasianodon hypophthalmus) Minced Muscle: The Effects on Selected Quality Properties of Its Gels

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

 

Thank you very much for this interesting paper. Please find blew feu remarks and/or questions to be considered if possible:

 

Line 4 : I propose to add “of its gel” , for example, to the title or any other modification to understand that the gel is the studied matrix ant not the meat.  It is up to you.

Line 99 : what is your culture medium for the TPC ?

Line 197 : I like to know the initial contamination ratio of the samples before any treatment to see its efficiency.

Line 209 : with more than 1 log, I am not sur that we can extend the shelf life considerably. What is the microbial norms for this kind material ?

 

Thanks

 

Author Response

Comment 1: Line 4: I propose to add “of its gel” , for example, to the title or any other modification tounderstand that the gel is the studied matrix ant not the meat. It is up to you.

Response 1: Thank you for your suggestion. We agree that the title should be clear so we added "of its gels" to the title and highlighted

Comment 2: Line 99: what is your culture medium for the TPC?

Response 2: Thank you for pointing this out. The culture medium used for TPC was Plate Count Agar (PCA). This information has now been added to the revised manuscript and highlighted.

Comment 3: Line 197: I’d like to know the initial contamination ratio of the samples before any treatment to see its efficiency.

Response 3: We appreciate your valuable comment. The TPC of untreated raw pangasius muscle was approximately 5.14 ± 0.19 log CFU/g. This data has been added to the results section as your comments.

Comment 4: Line 209: With more than 1 log, I am not sure that we can extend the shelf life considerably. What is the microbial norm for this kind of material?

Response 4: Thank you for your comment. We agree that TPC immediately after treatment may not fully predict the shelf life. We deleted the suggestion.

Reviewer 2 Report

Comments and Suggestions for Authors

The analysis and discussion section is too little, please add the overall study of the mechanism analysis and cause analysis.

Author Response

Comment 1: The analysis and discussion section is too little, please add the overall study of themechanism analysis and cause analysis.

Response 1: Thank you very much for your valuable comment. In response, we carefully revised and extended the Analysis and Discussion sections by adding more detailed explanations of the underlying mechanisms and causes associated with the observed results. Specifically, we expanded the analysis and discussions in the TPC, Colour Analysis, Water-Holding Capacity, Mechanical Properties, Microstructure (SEM), and FTIR sections. We hope that these revisions could meet your expectations

Reviewer 3 Report

Comments and Suggestions for Authors

The present entitled “High pressure processing of reduced salt pangasius catfish (Pangasianodon hypophthalmus) minced muscle: the effects on selected quality properties” has been good written but there is no novelty. All work has already been done on HPP and salt concentration.

• Lines 54-58: authors reported mechanism of HPP, what is author novelty in this paper?
• Mention legends and abbreviations in footnote of figures.
• Figure 3. statistical design especially small letters from b to c are contradicting.
• Authors are suggested to conduct protein oxidation parameters (carbonyl, S-H and S-S bonds) in order to assess the effectiveness of HPP against oxidation.
• Figure 6: indicate the changes occurs at different peaks/bands of FTIR in different treatment.
• Lines 220-221: how denaturation causes white color? Any justification or explanation with reference to previous studies. 
• authors should improve discussion section by logical and new insights. 
• clearly state novelty of study and future prospects. 
• why authors did not use high dose of HPP? 

 

Author Response

Comment 1: Lines 54-58: authors reported mechanism of HPP, what is author novelty in this paper?

Response 1: Thank you for your thoughtful question. The novelty of this study lies in the application of high-pressure processing (HPP) to produce salt reduced fish gels, which is the current trend in the food industry and public health. Pangasius is an economically important fish species for many Asian countries and is widely consumed globally. However, the application of novel processing technologies—particularly HPP—on pangasius remains very limited or nearly unexplored.

In addition to evaluating the effects of HPP on gel quality, we employed analytical techniques to gain deeper insights into protein and structural changes. For example, FTIR analysis was conducted using second derivative and deconvolution techniques to investigate detailed alterations in protein secondary structures. Although some previous studies have applied FTIR to fish muscle, but in-depth structural analysis is still limited. Moreover, we also conducted SDS-PAGE on both SDS soluble and sarcoplasmic proteins, which are rarely reported in the previous studies of SDS-PAGE of fish proteins. We hope that our findings can serve as a useful reference for understanding the impact of HPP on the secondary structure of fish proteins.

Due to time and resource limitation, further research is still needed. However, we hope that this study could be a first step in applying advanced, health oriented technologies to the development of value added pangasius products.

Comment 2: Mention legends and abbreviations in footnote of figures.

Response 2: Thank you for pointing this out. We have added the legends and relevant abbreviations (e.g., HPP, HIG, PG300, PG400, PG500) to the footnotes of all figures and tables and highlighted.

Comment 3: Figure 3. Statistical design especially small letters from b to c are contradicting

Response 3: Thank you for your carefully reviewing. We have corrected the error and highlighted

Comment 4: Authors are suggested to conduct protein oxidation parameters (carbonyl, S-H and S-S bonds) in order to assess the effectiveness of HPP against oxidation.

Response 4: Thank you for this valuable suggestion. We acknowledge that assessing protein oxidation (carbonyl content, sulfhydryl, and disulfide bonds) would provide deeper insights into the oxidative stability of HPP-treated gels. However, in this study, we focused on the main physicochemical properties for gelation. We will note this for a future research

Comment 5: Figure 6: Indicate the changes occurs at different peaks/bands of FTIR in different treatment.

Response 5: Thank you for your comment. We have revised the figure caption and highlighted

Comment 6: Lines 220–221: How denaturation causes white color? Any justification or explanation with reference to previous studies.

Response 6:

Thank you for your comment. Several studies have shown that high-pressure processing (HPP) can cause protein denaturation in a way that can increase the whiteness of both fish muscle and fish gels. We have revised the sentence in the manuscript to improve clarity.

Examples from the literature include:

Fish muscle:

Carp – Physicochemical changes induced in carp (Cyprinus carpio) fillets by high pressure processing at low temperature (Sequeira-Muñoz et al., 2006)

Tuna – High pressure processing of fresh tuna fish and its effects on shelf life (Zahra Zare, 2004)

Barramundi – High pressure processing of barramundi (Lates calcarifer) muscle before freezing: The effects on selected physicochemical properties during frozen storage (Truong et al., 2016)

Review – Effect of high pressure on fish meat quality – A review (Oliveira et al., 2017)

Fish gels:

Arrowtooth flounder – Effect of high-pressure treatments on mechanical and functional properties of restructured products from arrowtooth flounder (Atheresthes stomias) (Uresti et al., 2004)

Surimi gels – Effect of high pressure on reduced sodium chloride surimi gels (Cando et al., 2015)

Barramundi – Effect of high-pressure treatments prior to cooking on gelling properties of unwashed protein from barramundi (Lates calcarifer) minced muscle (Truong et al., 2017)

Comment 7: Authors should improve discussion section by logical and new insights.

Response 7: We have revised and expanded the discussion section by adding some explanations and discussions. We hope that the revision could meet your expectations

Comment 8: Clearly state novelty of study and future prospects

Response 8: We have clarified the novelty and added the future prospects of this study in the revised manuscript and highlighted

Comment 9: Why authors did not use high dose of HPP?

Response 9: Thank you for your interesting question. Although the maximum capacity of the HPP system is 600 MPa, this pressure is rarely used in practice due to concerns about equipment durability, and therefore it is not commonly applied in commercial-scale production. The pressure levels used in this study (300–500 MPa) were selected based on preliminary trials and previous literature, which indicate that pressures above 500 MPa may disrupt gel structure and increase energy costs

Reviewer 4 Report

Comments and Suggestions for Authors

1. Lines 233 and 234. The authors contradict themselves in this statement, given that the data shown in Table 1 indicate that there are no statistical differences between the color values. This reflects the authors' contradictions between their data and their discussion. This indicates that they have not been objective in their data analysis.

 

2. Lines 247 to 248. This statement does not reflect what is shown in Table 2, given that the results between 300 and 500 MPa are statistically equal, thus contradicting what is reflected in the results. The authors do not consider the statistical component, which is what allows real differences to be established. This reflects the authors' subjective discussion of the results, rather than objective discussion based on the statistical evidence.
3. Lines 262 to 263. The authors argue that the treatments are similar to the control treatment (HIG). However, according to the statistical connotations, it is evident that in two of the three parameters evaluated, the treatments are equal but different from the HIG control. It seems that the authors generate subjective arguments without considering what they themselves report in their results, assigning literals to denote statistical differences. Especially considering that the control also has 2% salt?

 

4. On the other hand, could reducing salt by just 1%, that is, going from 2% to 1% salt, be considered a significant change in terms of salt concentration? The authors should fully justify the selection of these salt percentages.

 

5. Lines 325 and 326 describe the proteins as extensively modified, but lines 352 to 353 mention that the proteins are not modified. These are inconsistencies that the authors should clarify.

 

6. In many cases, authors limit themselves to mentioning the concordances with those reported by other authors. It is necessary to discuss the results, explaining the relationship between the chemical, biochemical, or physical properties of the analyzed samples. Therefore, it is necessary to include more bibliography to help explain the behavior of the results instead of merely mentioning the concordance with other studies.

Author Response

Comment 1: Lines 233 and 234. The authors contradict themselves in this statement, given that thedata shown in Table 1 indicate that there are no statistical differences between the colorvalues. This reflects the authors' contradictions between their data and their discussion.This indicates that they have not been objective in their data analysis

Response 1: Thank you for your question. This was our mistake, as the ΔE values reported in Table 1 represent the color differences between each HPP treated sample and the heat-induced gel (HIG), which was used as the reference. Therefore, statistical comparison is not necessary. We have removed the superscript letters from the ΔE values to avoid confusion

Comment 2: Lines 247 to 248. This statement does not reflect what is shown in Table 2, given that theresults between 300 and 500 MPa are statistically equal, thus contradicting what isreflected in the results. The authors do not consider the statistical component, which iswhat allows real differences to be established. This reflects the authors' subjective discussion of the results, rather than objective discussion based on the statisticalevidence.

Response 2: Thank you for your comment. We acknowledge that the statement may lead to misunderstanding, as there were no statistically significant differences among the 300–500 MPa treatments in Table 2. We have removed the sentence from the revised manuscript.

Comment 3: Lines 262 to 263. The authors argue that the treatments are similar to the control treatment (HIG). However, according to the statistical connotations, it is evident that in two of the three parameters evaluated, the treatments are equal but different from the HIG control. It seems that the authors generate subjective arguments without considering what they themselves report in their results, assigning literals to denote statistical differences. Especially considering that the control also has 2% salt?

Response 3: Thank you for pointing this out. We agree that the statement may cause confusion, as the pressure treated gels with 1% salt exhibited comparable hardness and higher gel strength compared to HIG (2% salt). We have revised the sentence for clarity and have highlighted the changes

Comment 4: On the other hand, could reducing salt by just 1%, that is, going from 2% to 1% salt, beconsidered a significant change in terms of salt concentration? The authors should fullyjustify the selection of these salt percentages.

Response 4: Thank you for your thoughtful comment. The selection of 1% salt was based on several considerations. First, our preliminary experiments showed that gels formed without added salt (0%) were weak and brittle. Second, 1% is a commonly studied concentration in previous research on salt-reduced surimi and fish gels. Third, we believe that reducing the salt content from 2% to 1% (a 50% reduction) is meaningful from both technological and health perspective

Comment 5: Lines 325 and 326 describe the proteins as extensively modified, but lines 352 to 353 mention that the proteins are not modified. These are inconsistencies that the authors should clarify

Response 5:Thank you for pointing the inconsistencies out. We agree this may have caused confusion, so we have revised the text and added a paragraph to clarify the difference in materials and methods section.

Comment 6: In many cases, authors limit themselves to mentioning the concordances with those reported by other authors. It is necessary to discuss the results, explaining the relationship between the chemical, biochemical, or physical properties of the analyzed samples. Therefore, it is necessary to include more bibliography to help explain the behavior of the results instead of merely mentioning the concordance with other studies.

Response 6: Thank you for this valuable suggestion. In the revised manuscript, we have expanded the discussion sections with added reference to better explain the observed trends. We hope that the revision could meet your expectations.

 

Reviewer 5 Report

Comments and Suggestions for Authors

This manuscript investigates the effects of HPP on the quality properties of pangasius catfish minced muscle gels with reduced salt concentrations. It is well-structured and follows a logical progression from introduction, materials and methods, results, and discussion to conclusions. 

• It is necessary to add a brief explanation of why specific pressures (300, 400, and 500 MPa) were chosen for the HPP treatments.
• The authors should clarify the rationale behind the choice of 1% and 2% salt concentrations
• The authors should discuss the practical implications of the findings, such as the potential for extended shelf life or improved consumer acceptance of the reduced salt products
• The authors should discuss potential limitations of the study, such as the use of a single species or the specific processing conditions employed.

Author Response

Comment 1: It is necessary to add a brief explanation of why specific pressures (300, 400, and 500 MPa) were chosen for the HPP treatments

Response 1: The pressure levels were selected based on preliminary trials and literature, which suggest that this range (300–500 MPa) is effective for inducing gelation in fish proteins without causing gel structure damage. Pressures above 500 MPa for treating gel products are rarely used in practice due to potential structural degradation of gels and concerns about equipment durability and high energy consumption.

Comment 2: The authors should clarify the rationale behind the choice of 1% and 2% salt concentrations

Response 2: We have included a clarification in the revised manuscript. These levels were chosen based on previous studies related to salt-reduced surimi and fish gels. Preliminary experiments showed that 0% salt resulted in very weak and brittle gels, whereas 1% salt is a commonly studied concentration in previous research on salt-reduced surimi and fish gels. A reduction from 2% to 1% also represents a 50% decrease in sodium content, which is meaningful from both technological and health perspective.

Comment 3: The authors should discuss the practical implications of the findings, such as the potential for extended shelf life or improved consumer acceptance of the reduced salt products

Response 3: We have expanded the conclusion section to briefly discuss the potential benefits of using HPP in reduced-salt fish gel products. This study did not assess shelf life or consumer perception, the improved physicochemical properties may contribute to better stability and consumer acceptance.

Comment 4: The authors should discuss potential limitations of the study, such as the use of a single species or the specific processing conditions employed

Response 4: Thank you for your valuable suggestion. We have added a paragraph to mention the limitations of this study in conclusion section and highlighted.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I think this revised paper could be accepted in current form.

Author Response

Comment: I think this revised paper could be accepted in current form.
Response: The authors thank for the acceptance recommendation of the reviewer.

Reviewer 3 Report

Comments and Suggestions for Authors

no further comment

 

Author Response

Comment: no further comment
Response: The authors thank for the valuable support of the reviewer.

Reviewer 4 Report

Comments and Suggestions for Authors

1. The authors should explain more clearly why they eliminated the statistical comparison of color change if they want to know which treatment is closer to the control.
2. The authors do not provide scientific references to support the choice of salt percentages used. No preliminary data or experimental design is reported to help clarify how salt levels are selected. Even when salt is typically used, scientific evidence of the use of these salt percentages is necessary.
3. It is necessary to show bibliographic evidence that demonstrates the authors' argument is valid. Saying they are commonly used levels is a very subjective way of presenting the levels of an independent variable. This is not correct.

Author Response

Comment 1: The authors should explain more clearly why they eliminated the statistical comparison of color change if they want to know which treatment is closer to the control.

Response 1:

Thank you for your comment. We have deleted the statistical comparison for the following reason:

Your previous comment stated that “Lines 233 and 234. The authors contradict themselves in this statement, given that the data shown in Table 1 indicate that there are no statistical differences between the color values.”

Lines 233 and 234 in the manuscript state:

“In this study, the ΔE value ranging from 6.15 to 6.59 indicates a strong color difference between the pressure-induced gels and HIG.”

This statement does not contradict to “the data shown in Table 1 indicate that there are no statistical differences between the color values.” Our statement refers to the difference between the heat-induced gels (HIG) and the pressure-treated gels, while the statistical comparison in Table 1 refers to the differences among the pressure-treated gels only.

As we used heat induced gels as a benchmark, there is no ΔE data available for this treatment, and therefore we cannot assign statistical letters to it. We agree with your suggestion that the manuscript should be clear and easy for readers to follow. Since the statistical comparison among the treatments is insignificant, and including it may confuse readers, we have deleted it for clarity.

Comment 2: The authors do not provide scientific references to support the choice of salt percentages used. No preliminary data or experimental design is reported to help clarify how salt levels are selected. Even when salt is typically used, scientific evidence of the use of these salt percentages is necessary

Response 2:

Thank you for your valuable comment. Regarding the use of 2% salt concentration as the conventional level, Cando et al. (2015) or Li et al. (2024) stated that:
“On the technological side, gel based products are normally made with 2–3% NaCl, and thus their physicochemical properties are highly suited to this kind of product.”

In addition, the study by Zhang et al. (2023), Zhang et al. (2023b) and Wu et al. (2024) also used 2% salt concentration as the control, while 1% was considered as the reduced salt treatment.

We also published papers focusing on salt reduction in barramundi gels, in which 2% NaCl was used as the conventional salt concentration, and 1% as the reduced level. These include:

2. Truong, B.Q.; Buckow, R.; Nguyen, M. Mechanical and Functional Properties of Unwashed Barramundi (Lates calcarifer) Gels as Affected by High-Pressure Processing at three Different Temperatures and Salt Concentrations. Journal of Aquatic Food Product Technology 2020, 1-10.
3. Truong, B.Q.; Buckow, R.; Nguyen, M.H.; Furst, J. Effect of high-pressure treatments prior to cooking on gelling properties of unwashed protein from barramundi (Lates calcarifer) minced muscle. International Journal of Food Science & Technology 2017, 52, 1383-1391.

We have cited these references accordingly in the revised manuscript.

References

17. Li, Q.; Chen, S.; You, J.; Hu, Y.; Yin, T.; Liu, R. A comprehensive unraveling of the mystery of reduced-salt surimi gels: From molecular mechanism to future prospects. Trends in Food Science & Technology 2024, 154, 104783.
18. Wu, D.; Xiong, J.; Li, P.; Zhang, Y.; Li, F.; Yin, T.; Huang, Q. Dual enhancement effects of different yeast extract on gel properties and saltiness perception of low-salt surimi gel from silver carp. Food Hydrocolloids 2024, 152, 109925.
19. Zhang, C.; Chen, L.; Lu, M.; Ai, C.; Cao, H.; Xiao, J.; Teng, H. Effect of cellulose on gel properties of heat-induced low-salt surimi gels: Physicochemical characteristics, water distribution and microstructure. Food Chemistry: X 2023, 19, 100820.
20. Zhang, X.; Guo, Q.; Shi, W. Ultrasound-assisted processing: Changes in gel properties, water-holding capacity, and protein aggregation of low-salt Hypophthalmichthys molitrix surimi by soy protein isolate. Ultrasonics Sonochemistry 2023, 92, 106258.

Comment 3: It is necessary to show bibliographic evidence that demonstrates the authors' argument is valid. Saying they are commonly used levels is a very subjective way of presenting the levels of an independent variable. This is not correct

Response 3:                             

Thank you for your comment. We agree that the selection of experimental levels should be supported with scientific evidence rather than subjective statements. Therefore, we have revised the manuscript to include bibliographic references that support for our selection of 1% and 2% salt concentrations and highlighted