Impact of Calcium Chloride Addition on the Microstructural and Physicochemical Properties of Pea Protein Isolate-Based Films Plasticized with Glycerol and Sorbitol
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The paper titled “Comparative Study on the Effect of Calcium Chloride on the Physicochemical Properties of Glycerol- and Sorbitol-Plasticized Pea Protein Isolate Films” presents a good comparison and characterization of the films, as well as the effect that CaCl2 has as a cross-linking agent. However, the methodology requires some attention, mainly in the formulation of the films and the average thickness they presented, as well as a better nomenclature that allows to quickly identify which test is being talked about. Below I list some additional recommendations. Good article.
- If CaCl2 did not improve the properties of PPI films, why did you use this, only as a cross-linking agent?
- It is well known that some raw materials from plants can be cheaper than those from animals. However, this fact can also have a considerable environmental impact, so obtaining raw materials from biomass can be more profitable and have a better approach to obtaining raw materials.
- The methodology of the opacity measurement is not clear, please provide a better explanation of the wavelength used to obtain the value
-improve images
-define all abbreviations
Comments on the Quality of English Languageno comments
Author Response
Thank you very much for taking the time to review this manuscript. Please find below our detailed responses, with the corresponding revisions and corrections highlighted in yellow in the re-submitted files
Comments 1: The paper titled “Comparative Study on the Effect of Calcium Chloride on the Physicochemical Properties of Glycerol- and Sorbitol-Plasticized Pea Protein Isolate Films” presents a good comparison and characterization of the films, as well as the effect that CaCl2 has as a cross-linking agent. However, the methodology requires some attention, mainly in the formulation of the films and the average thickness they presented, as well as a better nomenclature that allows to quickly identify which test is being talked about. Below I list some additional recommendations. Good article.
Response 1: The average thickness of the resultant has been mentioned (please see L126). List of major abberviations has been added. The M&M section has been improved.
Comments 2: If CaCl2 did not improve the properties of PPI films, why did you use this, only as a cross-linking agent?
Response 2: It has been demonstrated in some studies, that Ca2+ significantly increases the gelation ability, elastic modulus and textural properties of PPI gels through a protein crosslinking mechanism. Therefore, in the present study, we hypothesized that the interaction between Ca2+ and pea protein might improve some functional properties of the resultant films. It has been mentioned in the corrected manuscript (please see L98-102). However, our results showed otherwise. Although the films obtained in this study did not exhibit the expected improvements in properties, they could potentially serve as a source of calcium in the diet. It has been mentioned in corrected manuscript (please see L515-516).
Comments 3: It is well known that some raw materials from plants can be cheaper than those from animals. However, this fact can also have a considerable environmental impact, so obtaining raw materials from biomass can be more profitable and have a better approach to obtaining raw materials.
Response 3: The reviewer is correct; this has been included in the revised manuscript (please see L51).
Comments 4: The methodology of the opacity measurement is not clear, please provide a better explanation of the wavelength used to obtain the value.
Response 4: It has been corrected.
Comments 5: improve images.
Response 5: The GA and Figure 4 have been corrected. Thank you to the Reviewer for pointing this out. Microstructure images have ben added.
Comments 6: define all abbreviations.
Response 6: List of major abberviations has been added. Please see at the end of the manuscript.
Reviewer 2 Report
Comments and Suggestions for AuthorsDear authors
-"Pea Protein Isolate Films": the polymer of which the film is manyufactured is this protein. It is of amino acid origin, perhaps a more official name? Certainly the PPI is not acceptable! You know that polymers are abbreviated with P..., here instead of peas? (polypeptide that is used later in text if the right category, if you don't know the amino acids)
-"protein gels and films": both gels and films are proteins? Or made from polymers derived from polymers?
-"0, 0.01 0.025 0.05%" commas in between?
-"water affinity and mechanical characteristics": never use a comma before the words "and" or "or" when for simple parathesis of similar things. The liaise word already exists, check and correct in text where needed
-what do you mean "bioplastics?" I think "bio-based" or "bio-sourced" plastics is more appropriate, depending on the technique used and the origin of the material.
-l. 53: parenthesis in parenthesis? Perhaps, rephrase...
-"As known, alkalization improves the solubility of pea proteins": why is that? What are the amino acids included, so what functional groups are active at aquatic environment?
-by "protein-protein interactions" do you mean physicochemical forces and affinity or the covalent bonds? Because cross-linking is the creation of covalent bonds by adding the cross-linking agent (or by subtraction of H2O). So, clarify, CaCl2 is a cross-linker? (explained a bot in l. 262...)
-what is the moisture of the commercial product?
-"FFSs": stand for what?
-what about film thickness?
-L*a*b* and C*h°: in italics. E* as well
-it is mL
-equations could be written properly
-elastic modulus as E..., moisture content MC? the initial length is L0 or Li
-what about the concentration 0.01%wt? They did not form a good film?
-colour changes notable above 3 or 5 of ΔΕ*? Please check
-"nixtamalization process": please describe
-"porcine gelatin": is this your case?
-"recrystallized Sor": recrystallization because of water removal, pH state or temperature condition? Does the material have the time to crystallize a bit or is it amorphous? (explained a bit in l. 297)
-"biopolymeric films": again, what do you mean?
-"CaCl2 did not provide significant benefits to the PPI films and actually worsened their key properties such as transparency and mechanical strength": this is a "heavy" salt, how did you come up with this trial? Dairy food provide it but others?
Comments on the Quality of English LanguageThere are some mistakes to be taken care: many nouns in row instead of adjectives or past-partiples, and sentences with mixed turn of words I think...
Author Response
Thank you very much for taking the time to review this manuscript. Please find below our detailed responses, with the corresponding revisions and corrections highlighted in yellow in the re-submitted files
Comments 1:”Pea Protein Isolate Films": the polymer of which the film is manufactured is this protein. It is of amino acid origin, perhaps a more official name? Certainly the PPI is not acceptable! You know that polymers are abbreviated with P..., here instead of peas? (polypeptide that is used later in text if the right category, if you don't know the amino acids)
Response 1: "PPI" is a typical abbreviation for pea protein isolate. Please see: [https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/pea-protein-isolate]. Similarly, "SPI" is a common abbreviation for soy protein isolate. The term "pea protein isolate films" has been used many times previously by different authors:
- [https://www.sciencedirect.com/science/article/pii/S0308814622009360]
- [https://ifst.onlinelibrary.wiley.com/doi/pdf/10.1111/jfpp.12135]
- [https://www.sciencedirect.com/science/article/pii/S2772502222000622]
Therefore, I hope the reviewer will accept this terminology. Nevertheless, for clarification, "PPI-based films" is used in the revised manuscript.
Comments 2: "protein gels and films": both gels and films are proteins? Or made from polymers derived from polymers?
Response 2: For clarification, "PPI-based gels and films" is used in the revised manuscript. Please see, for example, L13.
Comments 3: "0, 0.01 0.025 0.05%" commas in between?
Response 3: I am sorry for the oversight. The missing commas have been added.
Comments 4: "water affinity and mechanical characteristics": never use a comma before the words "and" or "or" when for simple parathesis of similar things. The liaise word already exists, check and correct in text where needed
Response 4: Reviewer is correct that a comma is typically not used before "and" or "or" when listing similar items. I have revised the manuscript accordingly and removed the comma in the phrase "water affinity and mechanical characteristics" and others to adhere to standard conventions. Please find the corrected text in the revised manuscript. Thank you for bringing this to my attention.
Comments 5: what do you mean "bioplastics?" I think "bio-based" or "bio-sourced" plastics is more appropriate, depending on the technique used and the origin of the material.
Response 5: The term "bioplastics" was used to describe the materials fully or partially made from biological resources rather than fossil materials. However, I agree that "bio-based" or "bio-sourced" plastics may more accurately reflect the nature of the materials, depending on their origin and the technique used. I have revised the manuscript to use "bio-based" plastics as appropriate, based on the specific context and material descriptions. Please see, for example, L33.
Comments 6: l. 53: parenthesis in parenthesis? Perhaps, rephrase...
Response 6: It has been corrected.
Comments 7: "As known, alkalization improves the solubility of pea proteins": why is that? What are the amino acids included, so what functional groups are active at aquatic environment?
Response 7: The sentence has been revised to better convey the intended meaning. Please see the updated version below: “As known, alkalization disrupts the protein’s native conformation, leading to unfolding or partial denaturation. As a result, previously buried –SH groups and hydrophobic regions of the protein become exposed, facilitating the formation of a network among polypeptide chains and improving the cohesiveness of PPI-based films”.
Comments 8: by "protein-protein interactions" do you mean physicochemical forces and affinity or the covalent bonds? Because cross-linking is the creation of covalent bonds by adding the cross-linking agent (or by subtraction of H2O). So, clarify, CaCl2 is a cross-linker? (explained a bot in l. 262...)
Response 8: According to Jayachandran et al. [2022], a crosslink refers to either a physical or chemical bond that connects reactive groups in a polymer network through stronger covalent bonds or weaker interactions such as ionic/hydrogen bonding or other non-specific interactions. Protein crosslinking can be achieved by physical or chemical means, or by using crosslinkers. [https://www.mdpi.com/1420-3049/27/23/8124]. The understanding of the mechanism behind calcium-induced crosslinking of proteins has been enhanced. Please refer to L... Additionally, it is important to note that a common example is the crosslinking of alginate. Alginate contains guluronic acid and mannuronic acid units that can form ionic bonds with calcium ions. The carboxyl groups in pectin can also interact with calcium ions through ionic bonding. Furthermore, calcium ions are often considered an ionic crosslinker for whey proteins [https://pubs.acs.org/doi/10.1021/acsabm.8b00604]. [https://www.sciencedirect.com/science/article/abs/pii/S0268005X19314249] [https://pubs.acs.org/doi/10.1021/acsabm.8b00604].
Comments 9: what is the moisture of the commercial product?
Response 9: The chemical characterization of PPI, based on the producer's datasheet, has been expanded. Please see L110-111.
Comments 10: "FFSs": stand for what?
Response 10: Abbreviations are defined in the text upon their first use. Please note that the abstract ia a standalone section of the manuscript. However, a list of abbreviations has been added for convenience. Please see L518-523.
Comments 11: what about film thickness?
Response 11: The film thickness has been mentioned. Please see L126.
Comments 12: L*a*b* and C*h°: in italics. E* as well
Response 12: It has been corrected.
Comments 13: it is mL
Response 13: It has been corrected.
Comments 14: equations could be written properly
Response 14: The equations have been verified, however, the equation editor was not used. We hope the reviewer will accept this.
Comments 15: elastic modulus as E..., moisture content MC? the initial length is L0 or Li
Response 15: I’m not sure if the property abbreviations should be in italics. I’ll leave that to the publisher’s discretion. They will definitely format it if necessary or we will make this adjustment during the manuscript's final revision if necessary. “Li” has been introduced into revised manuscript.
Comments 16: what about the concentration 0.01%wt? They did not form a good film?
Response 16: Yes, if considering the reduced tensile strength.
Comments 17: colour changes notable above 3 or 5 of ΔΕ*? Please check
Response 17: A standard observer sees the difference in color as follows. When:
- 0 < ∆E < 1 - observer does not notice the difference,
- 1 < ∆E < 2 - only experienced observer can notice the difference
- 2 < ∆E < 3.5 - unexperienced observer also notices the difference,
- 3.5 < ∆E < 5 - clear difference in color is noticed,
- 5 < ∆E - observer notices two different colors
[https://wisotop.de/assets/2017/DeltaE-%20Survey-2.pdf]
Comments 18;"nixtamalization process": please describe
Response 18: pH measurements showed that calcium chloride has an acidifying effect. The hypothesis regarding the nixtamalization process (alkaline heating) has been discarded. I thank the reviewer—this feedback inspired me to reconsider the explanations.
Comments 19: "porcine gelatin": is this your case?
Response 19: Yes, it has been detailed in the revised manuscript.
Comments 20: "recrystallized Sor": recrystallization because of water removal, pH state or temperature condition? Does the material have the time to crystallize a bit or is it amorphous? (explained a bit in l. 297)
Response 20: Microstructural analyses did not reveal Sor recrystalisation. The statement has been removed.
Comments 21: "biopolymeric films": again, what do you mean?
Response 21: It has been changed to “biopolymer-based films”.
Comments 22: "CaCl2 did not provide significant benefits to the PPI films and actually worsened their key properties such as transparency and mechanical strength": this is a "heavy" salt, how did you come up with this trial? Dairy food provide it but others?
Response 22: It has been mentioned in the revised version of manuscript. Please see L98-102.
Comments 23: Comments on the Quality of English Language. There are some mistakes to be taken care: many nouns in row instead of adjectives or past-partiples, and sentences with mixed turn of words I think...
Response 23: English Language has been improved. The final version will also undergo language editing by professionals. We have dedicated a significant amount of time to completing the analyses, and the editorial office has allowed only 8 days for responding to the reviews. We would appreciate your understanding in this matter.
Reviewer 3 Report
Comments and Suggestions for AuthorsThank you very much for your contribution. We are honored to have the opportunity to review your paper. This article presents a comparative study on the effects of calcium chloride on the physicochemical properties of pea protein isolate membranes, plasticized with glycerol and sorbitol phenol. The work highlights recent advancements in this field and explores various applications, encouraging further research in this area. Your paper demonstrates excellence in terms of content, innovation, and scientific value. Although there are some formatting and grammatical issues—such as certain sentences not flowing smoothly—these do not detract from the core ideas and findings of the study. To enhance the manuscript, I offer the following suggestions:
- Please consider revising the title to better reflect the specific research content and conclusions, making it more precise.
- The explanation in the results and discussion section, which attributes the contraction of FFS during evaporation to potential over-crosslinking of the protein matrix (i.e., the strong binding of polypeptide chains), may be speculative and requires further experimental evidence to substantiate this hypothesis.
- The manuscript lacks sufficient experimental support regarding Water Affinities. Please provide more data to reinforce this aspect of the study.
- Relying on only one table as experimental evidence for each section may not be sufficiently convincing. Consider including additional data or analyses to strengthen your arguments.
Author Response
Thank you very much for taking the time to review this manuscript. Please find below our detailed responses, with the corresponding revisions and corrections highlighted in yellow in the re-submitted files.
Comments 1: Thank you very much for your contribution. We are honored to have the opportunity to review your paper. This article presents a comparative study on the effects of calcium chloride on the physicochemical properties of pea protein isolate membranes, plasticized with glycerol and sorbitol phenol. The work highlights recent advancements in this field and explores various applications, encouraging further research in this area. Your paper demonstrates excellence in terms of content, innovation, and scientific value. Although there are some formatting and grammatical issues—such as certain sentences not flowing smoothly—these do not detract from the core ideas and findings of the study. To enhance the manuscript, I offer the following suggestions:
Please consider revising the title to better reflect the specific research content and conclusions, making it more precise.
Response 1: New title has been proposed.
Comments 2: The explanation in the results and discussion section, which attributes the contraction of FFS during evaporation to potential over-crosslinking of the protein matrix (i.e., the strong binding of polypeptide chains), may be speculative and requires further experimental evidence to substantiate this hypothesis.
Response 2: pH and microstructural properties of the films were investigated in order to get better insight in the calcium-induced changes of the properties of the films.
Comments 3: The manuscript lacks sufficient experimental support regarding Water Affinities. Please provide more data to reinforce this aspect of the study.
Response 3: pH and viscosity of the film-forming solutions were investigated in order to get better insight in the calcium-induced changes of the properties of the films. We hope that Reviewer will accept this. After prolonged contact with water, the films often break down into mushy pieces, which complicates the analysis.
Comments 4: Relying on only one table as experimental evidence for each section may not be sufficiently convincing. Consider including additional data or analyses to strengthen your arguments
Response 4: pH and viscosity of the film-forming solutions were investigated. Moreover microstructure (by using two techniques) and pH of the films were investigated.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsDear authors,
some more comments to consider:
-"nuts and lupin", "methylcellulose and certain food additives", "25°C and 6.7 mL" etc: remove commas before the "and" in text, check and correct throughout the text
-"[9-12]" instead
-use MathEditor in Word for equations
-I'd propose multiplication dots for the unit g m mm−2 day−1 kPa−1
-ΔE*: add the * in all cases
-the compounds HCl and Ca(OH)2, etc are known to everyone, no need for the full names, I'd propose
-h= 126.01 ±17.71 and 108.40 ± 10.89 have quite great std. Certainly, you may not repeat the measurements, just comment on the materials' colour state
-Table 3: So (%)= 100.00 ± 0.00 for all cases! Please comment on this value for the materials!
-the list of the abbreviations could be added in Results section, where are needed..?
Comments on the Quality of English Language
This is ok
Author Response
Thank you very much for taking the time to review this manuscript. Please find below our detailed responses, with the corresponding revisions and corrections highlighted in blue in the re-submitted files
Comments 1: "nuts and lupin", "methylcellulose and certain food additives", "25°C and 6.7 mL" etc: remove commas before the "and" in text, check and correct throughout the text
Response 1. It has been corrected in the revised version of the manuscript. However, I have used “oxford coma” and in my opinion it should be accepted. [https://www.youtube.com/watch?v=HT_Gvj6Z6Kk&ab_channel=GrammarMonster]
Please see this title for example: [https://www.sciencedirect.com/science/article/pii/S0268005X2100607X?via%3Dihub]
Comments 2:"[9-12]" instead
Response 2: It has been corrected in the revised version of the manuscript.
Comments 3: use MathEditor in Word for equations
Response 3: MathEditor has been used in the revised version of the manuscript.
Comments 4: I'd propose multiplication dots for the unit g m mm−2 day−1 kPa−1
Response 4: It has been corrected in the revised version of the manuscript.
Comments 5: ΔE*: add the * in all cases
Response 5: It has been corrected in the revised version of the manuscript.
Comments 6: the compounds HCl and Ca(OH)2, etc are known to everyone, no need for the full names, I'd propose
Response 6: It has been corrected in the revised version of the manuscript.
Comments 7: h= 126.01 ±17.71 and 108.40 ± 10.89 have quite great std. Certainly, you may not repeat the measurements, just comment on the materials' colour state
Response 7: h values were recalculated using Converter Lab to Lch [http://colormine.org/convert/lab-to-lch], and the statistical analysis was redone. Previously, h values generated from the colorimeter were used for the calculation of the means. However, I now realize that the h values did not always originate from the same measurements as a* and b*, which contributed to large standard deviations. The data in Table 2 have been corrected accordingly.
Comments 8: Table 3: So (%)= 100.00 ± 0.00 for all cases! Please comment on this value for the materials!
Response 8: Yes, after one day of shaking in water, the films disintegrated into small, clammy pieces, making it very difficult to retrieve the remnants. Therefore, 100% solubility was assumed despite the presence of sediment. It has been mentioned in the revised version of the manuscript.
Comments 9: the list of the abbreviations could be added in Results section, where are needed..?
Response 9. The list of the abbreviations has been shifted under the keywords.
Comments 10: Comments on the Quality of English Language: This is ok
Response 10 Thank you.
