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Peer-Review Record

Employing Nanosilver, Nanocopper, and Nanoclays in Food Packaging Production: A Systematic Review

Coatings 2021, 11(5), 509; https://doi.org/10.3390/coatings11050509

by Hamed Ahari^1,*

, Amir Ali Anvar²

, Maryam Ataee² and Mohammad Naeimabadi²

Reviewer 1: Anonymous

Reviewer 2: Anonymous

Reviewer 3: Anonymous

Coatings 2021, 11(5), 509; https://doi.org/10.3390/coatings11050509

Submission received: 17 March 2021 / Revised: 16 April 2021 / Accepted: 21 April 2021 / Published: 25 April 2021

Round 1

Reviewer 1 Report

Very interesting topic and comprehensive paper! I think it is good and I appreciate your hard work in writing the paper. I have just 2 suggestions: (1) add a comprensive list of abbreviations up front for easy reference next to the keywords and (2) if possible consider using food functionality titles as sub-section like UV Protection, High Gas Barrier Plastics ... so on and than describe the specific nanomaterial that are available for this function.

Author Response

Dear Editor

We highly appreciate the kindness of the reviewers and their deep and thorough comments. We are satisfied with the correctness and improvements in our paper due to the comprehensive and wisely comments from the reviewers. We have revised the present review paper in the light of their useful suggestions and comments. I hope our revision has improved the paper to the level of their satisfaction and suitable for publication. Our answers to their specific comments, suggestion, queries are finned the following.

Best Regards

please check the attachement

Author Response File: Author Response.docx

Reviewer 2 Report

The present manuscript intends to summarizes A systematic review on the use of nanomaterials in novel food packaging applications. The manuscript is interesting, well organized and somewhat updated. However, it is very general and it seems a technical revision. Thus, it requires major revisions previous to be published.

Each section should be extended summarizing the state of the art. Some sections only mention some very short generalities about food pancaking.

It is very important to included more related works in this field. There are outstanding research groups very well known around the world working on nanocomposite for food packaging applications. Please see papers from the following leading research groups in this field:

- Prof. Philippe Dubois research group (Mons Belgium)

- Prof José María Kenny research group (Terni, Italy and Madrid Spain)

- prof Luc Averou (Strasburgo, France)

- Prof. Amparo Chiralt’s research group (Valencia, Spain).

My first concern about this manuscript is the Title. It is not a compressive review on nanomaterials in novel food packaging applications. It was focused on three main nanoparticles including Nanosilver, Nanocopper, and Nanoclays. Therefore, the title is not proper. It is very broad and should be focused on the present bibliographic revision.

In section “Nanomaterials in food packaging: definition, characteristics and types”, examples of the different nanoparticles should be mentioned such as cellulose nanocrystals

As barrier properties against gases and humidity or water are of fundamental importance in food packaging applications, the nanoparticles role in the improvement of barrier properties of food packaging should be discussed in a separated section

In section 4 “Natural biopolymers”, the most important and currently used materials such as poly(lacticacid) (PLA) and polyhydroxyalacanoates (PHAs) should be better discussed. Particularly, in section “Synthetic polymers” they should be (have to) described correctly. Those polymers are not all natural polymers. For instance, PCL and PBS are compostable, but they are petrochemical based polymers.

Conclusions should be substantially improved.

Author Response

Dear Editor

Best Regards

Changes are highlighted in red.

Reviewer 2

The present manuscript intends to summarize A systematic review on the use of nanomaterials in novel food packaging applications. The manuscript is interesting, well organized and somewhat updated. However, it is very general and it seems a technical revision. Thus, it requires major revisions previous to be published.

Response: Under the light of the wise comments from all reviewer, we made a revision and hope it satisfies you. We checked the paper grammatically too. Paraphrased some statements which some are highlighted in red.

Each section should be extended summarizing the state of the art. Some sections only mention some very short generalities about food pancaking. It is very important to include more related works in this field.

Response: Thanks for the comment. We tried to expand the section and add more details considering the topic. However we will be thankful if you consider this issue regarding the new title, according to your following comment. We hope it satisfies you.

My first concern about this manuscript is the Title. It is not a compressive review on nanomaterials in novel food packaging applications. It was focused on three main nanoparticles including Nanosilver, Nanocopper, and Nanoclays. Therefore, the title is not proper. It is very broad and should be focused on the present bibliographic revision.

Response: the title has been changed: actually we tried to use another topic more relevant to the content. This topic has been chosen considering the main criteria of the paper. We will be thankful if you let us if it is suitable. We hope it satisfies you.

“Employing Nanosilver, Nanocopper, and Nanoclays in Food Packaging Production: A Systematic Review”.

In section “Nanomaterials in food packaging: definition, characteristics and types”, examples of the different nanoparticles should be mentioned such as cellulose nanocrystals.

Response: thanks for the comment. We agree with your comment. There are many type of nanoparticles which can be discussed. Actually it was tried to add more details regarding other type of nanoparticles. However, considering the changes in the title, addition of more type of nanoparticles and discussing them Disrupts content coherence. Besides the length of the paper will not be acceptable by the journal. Thereby, thanks to your previous comment, the title focuses on three nanoparticles and follows more metallic nanoparticles.

As barrier properties against gases and humidity or water are of fundamental importance in food packaging applications, the nanoparticles role in the improvement of barrier properties of food packaging should be discussed in a separated section.

Response: thanks for the comment. We added a section according to your wise comment. I hope it satisfies you. We tried to mention main aspects of barrier properties instead of repeating results from previous studies.

“Increasing the path length or blocking the passage of oxygen gas in the polymer by various particles is a new approach that has become one of the most important and effective pathways. There are several strategies for making an improved barrier properties in polymers (like bioplastics) used for food packaging due to refraining from migration of oxygen, carbon dioxide, anhydride, aroma, flavor, and water vapor to the ingredients of food, eventuating to make them as the most sustainable biopolymers [67, 172, 173]. Results of several studies proposed nanoscale size fillers like MMT, and kaolinite clay. Protein, starch, cellulose, PLA based nanocomposites are the ones that were separately reviewed earlier and compared, guaranteeing barrier performances and physical packaging integrity. Totally, it seems that industrial usage of polymer blends, multilayer systems, natural biopolymers with chemical modifications, coatings, and composites can improve aforementioned features [67, 172, 173].

Preserving food properties like taste, color, flavor, texture, and nutritional value happens by providing proper mechanical strength, barrier properties, and antimicrobial features for packaging compounds. NPs showed their potential in improving the barrier properties of the novel food packaging systems. Size, morphology and type of nanoparticles affect their potential in improving the barrier properties [174]. The shape of the particles in the change in permeability of the composite relative to the background is a function of the volume fraction of the particles. In fact, data volume fraction is the main input in most permeability prediction models, showing the sub-relationship of how the weight fraction is converted to volume [175]. The following equation shows how the weight loss is converted to volume:

(1)

Where and are the density of the particle and the polymer, and w is the weight percentage of the particle in the polymer. Spherical and cylindrical NPs mostly showed different effect on barrier properties compared with plate NPs. To increase the distribution of particles in the polymer field, chemical surface improvement of particles is another technique usually used and the most important goal is to bring closer the polarity of the polymer and nanoparticles [176]. In general, according to the polymer background, various carbonyl, hydroxyl, etc. groups can be used to improve the surface of particles. For example, in spherical particles such as SiO2, silyl or silane functional groups can be used to improve the particle surface. One of the most important reasons for the decrease in permeability by these particles can be the increase of curvature in the passage of oxygen permeable gas, germination in the polymer matrix and the formation of an adsorbent crystal in the condenser [177]. In this regard, it seems that nanoclay due to its plate form may illustrate more improvement in barrier properties comparing with Cu and Ag NPs.”

In section 4 “Natural biopolymers”, the most important and currently used materials such as poly(lacticacid) (PLA) and polyhydroxyalacanoates (PHAs) should be better discussed. Particularly, in section “Synthetic polymers” they should be (have to) described correctly. Those polymers are not all natural polymers. For instance, PCL and PBS are compostable, but they are petrochemical based polymers.

Response: thanks for the comment. We tried to make this section more acceptable by adding more details. We hope it satisfy you. Besides we added more details in other sections if needed.

“4.2. Polylactic Acid (PLA)

As properties like being easy to handle in making monomers, having less environmentally burden, sustainability, biocompatibility, and biodegradability are considered as the most important ones for nanomaterials used in nanocomposites for food packaging purposes, it has been demonstrated that PLA based nanocomposites are one of acceptable types of polymers used in food packaging. In spite of the fact that there is several merits for usage of PLA in food packaging, there are also several drawbacks as: having no cost-effectiveness, and low performance due to gas barrier properties. Results of several studies depicted that adding plasticizers or chemically modifications of PLA based nanocomposites can effectively hamper those shortcomings, and improve barrier properties of PLA based nanocomposites used for food packaging [136].

4.3. polyhydroxyalacanoates (PHAs)

Bioplastics like polyhydroxyalkanoates (PHAs) are considered a potent nominee for food packaging. The ideal features of PHAs comprises hydrophobicity, biodegradability, nonlinear optical activity, thermoplasticity, piezoelectricity, nontoxicity, and impermeability to water and/or gases [138]. In a research, PHA-based film incorporated with clove essential oil was prepared for active food packaging purposes. No microbial growth was reported on the film surface [139]. Migration is a key issue in food packaging, since monomers or additives employed in PHA preparation might conceivably migrate into food matrix. Incorporation of PHA with other biomaterials has been considered as a way of improving the vital properties while keeping biodegradability [140]. Furthermore, interest in promoting the main properties via fabrication of PHA-based nanocomposites by addition of organic or inorganic NPs such as MMT, layered double hydroxides, cellulose nanowhiskers, multi-walled CNT has rapidly increased [141]. It was also approved that PHA-based films can include metallic NP such as AgNPs, CuNPs, and ZnONPs to own more antibacterial, improved barrier and mechanical properties for food packaging purposes.”

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript has an interesting structure, and the authors make a careful review of the subject, having cited 175 references. The manuscript is easy to read but revision and spell-checking of English language is important to be done, mainly in the first part of the manuscript, e.g.:

Line 15: “Thereby, food industry economically, improve food safety and quality, and reduce the food spoilage will be promoted.” needs to be improved, please rewrite it
Line 26: “The concept of nanotechnology was firstly…” change to “The concept of nanotechnology was first…”
Line 25: “Thank to this technology, many of current…” change to “Thanks to this technology, many of the current…”
Line 38: “…study, antibacterial properties…” change to “…study, the antibacterial properties…”
Line 40: “…high potential for applying as an active food packaging…” change to “high potential to be applied in an active food packaging …”
Line 43: He focused on…” change to “They focused on…”
Line 71 “By searching literatures…” change to “By searching literature…”
…

Line 77: the phrase “As follows, we introduced nanomaterials using in food packaging, focusing on inorganic nanoparticles including metals, metal oxides, clay and its derivatives and their considerable features providing active and smart food packaging were discussed.” is very confusing, rewrite it, please
Introduction, Line 29: The phrase: “In 2013, the nano-packaging industry is valued at $ 6.5 billion and is projected to grow to $ 15.0 billion by 2020” the reference is missing. Moreover, given that we are already in 2021, can this information be updated?
The objectives of the work are only mentioned in the abstract. So, I think it is important at the end of the introduction, for example, that they appear clearly defined.
Line 57: “2.1 Study Selection” change to “2.2 Study Selection”
Table 2:

ml change to mL;
The reference column should be the last;
in the third column, if the units were placed in the title: Nanoparticle size (nm), it made the table more appealing
remove the space between the% symbol and the numbers;
the method description, on the third line, is very confusing, please rewrite it
species names written in Latin must always be written in italics. please review this aspect throughout the manuscript

The initials such as ENPs, PVOH, GI, and CB must be described in full the first time that appeared in the text.
Check all chemical symbols of chemical compounds as they appear misspelt in the text e.g. TiO2 change to TiO₂, nSiO2 change to nSiO₂ ...
2.6. Nano clays change to 3.2.6. Nanoclays
The sentence "However, migration experimental data are not currently available, despite the fact that a number of food packaging types containing NPs are already available and in commercial use in some countries" is not entirely true, see what Ahari et al. (2021), refer, in the article Migration of silver and copper nanoparticles from food coating: Many studies have reported that the application of NPs in food packaging may cause NPs migration into foodstuff that in turn, results in toxicity [55]. Check and correct if necessary

In my opinion, with these minor revisions, the manuscript will be ready for publishing.

Author Response

Dear Editor

Best Regards

Changes are highlighted in red.

Reviewer 3

The manuscript has an interesting structure, and the authors make a careful review of the subject, having cited 175 references. The manuscript is easy to read but revision and spell-checking of English language is important to be done, mainly in the first part of the manuscript, e.g.:

Response: thanks for the comment. We made a complete revision. We edited the paper grammatically. We paraphrased some parts. Added more details in some sections. We tried to provide a table for the abbreviations (as the reviewer No. 1 suggested). We added more sections too. The sub heading of some sections has been changed too. We hope it satisfies you.

Line 15: “Thereby, food industry economically, improve food safety and quality, and reduce the food spoilage will be promoted.” needs to be improved, please rewrite it.