The Optimization of Gelatin Extraction from Chicken Feet and the Development of Gelatin Based Active Packaging for the Shelf-Life Extension of Fresh Grapes

Round 1

Reviewer 1 Report

Line 39: Please modify. partial hydrolysis of collagen, which…

Line 41: Modify. characteristics of gelatin, which….

Line 46: is this global production of chicken feet?

Line 56: Of the total synthetic plastics (global) produced, what percentage is used for food packaging. Very briefly include this data.

Line 57: include briefly the reason for inclusion of CS and NPs.

Line 59: Please specify which type of NPs.

Line 61: what is the rationale for choosing to study with ZnO Nps

Line 147: Include instrument name and model

Table 3 shows microbiological analysis of grapes during storage. Although, influence of different treatments and storage days are indicated with different letter (lower & uppercase), methodology part shows that 1 way anova was performed. Why wasn’t 2 way anova performed?

A 2 way anova would show if there is any interaction between the factors: storage days and treatments(different thin films)

Line 315: please correct typo

Line 314-315: Are there any studies wherein incorporation of metallic or metallic-oxide NPs lowered the biodegradability? Include studies if possible

Conclusion; Improved packaging is different from active packaging. Please be clear if the objective was to develop improved or active packaging (or both) in the introduction. In addition, include the impact of Np incorporation on barrier properties (improved packaging).   

This manuscript is well written with very few mistakes. However, statistical representation of microbiological analysis has to be checked. In particular, values in Table 3 (and table s2) seem to have been derived from 1 way anova when it must have been from 2-way anova, which would indicate if there is interaction between the factors, storage days and treatment films.

   

 

 

 

 

Author Response

Reviewer # 1:

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Comment #1: Line 39: Please modify. partial hydrolysis of collagen, which….

Response: As advised by the reviewer, modified in the revised manuscript.

Comment #2: Line 41: Modify. characteristics of gelatin, which….

Response: Modified in the revised manuscript.

Comment #3: Line 46: is this global production of chicken feet?..

Response: Yes, it is global production of chicken feet and the expression has been modified in the revised manuscript to indicate the global production of chicken feet.

Comment #4: Line 56: Of the total synthetic plastics (global) produced, what percentage is used for food packaging. Very briefly include this data.

Response: Thank you for the valuable suggestion, the suggested information has been incorporated in the revised manuscript,

“The plastic-based packaging is associated with various environmental and health hazards. Global plastic production reached to 380 million metric tons in 2015 and 40% of this plastic production accounted for packaging materials. Approximately, 60% of plastic-based packaging material is used for food sector [8].

 

Comment #5: Line 57: include briefly the reason for inclusion of CS and NPs.

Response: The suggested information is mentioned in the revised manuscript, “Natural polymers, like gelatin and CS can be used to develop biodegradable packaging to preserve the fresh food produce [9]. The mechanical and preservation properties of gelatin-based packaging can be improved by the incorporation of other polymers such as CS and NPs [10]. CS is a non-toxic polysaccharide which exhibits good film forming capacity, biodegradability, mechanical and barrier properties [11]. The addition of NPs to gelatin composite films has been reported to improve the barrier properties [12].”

 

Comment #6: Line 59: Please specify which type of NPs.

Response: The suggested information has been incorporated in the revised manuscript.

Comment #7: Line 61: what is the rationale for choosing to study with ZnO Nps

Response: Thank you for the valuable suggestion, the rational of choosing ZnO NPs has been incorporated in the revised manuscript, “Incorporation of ZnO NPs improved the barrier properties and antimicrobial effect of gelatin based food packaging systems, moreover ZnO NPs were reported to be safe by Food and Drug Administration (FDA) [1].”

Comment#8: Line 147: Include instrument name and model.

Response: The suggested information has been incorporated in the revised manuscript.

Comment# 9: Table 3 shows microbiological analysis of grapes during storage. Although, influence of different treatments and storage days are indicated with different letter (lower & uppercase), methodology part shows that 1 way anova was performed. Why wasn’t 2 way anova performed? A 2 way anova would show if there is any interaction between the factors: storage days and treatments(different thin films)

Response: Thank you very much for the valuable suggestion, we do agree with the reviewer, two-way ANOVA would give much better understanding of the interactions among treatments. The method, tables and result sections have been revised by applying two way ANOVA for antimicrobial and preservation assays,”

Method section:

“ Statistical Analysis

All experiments were carried out in triplicates and results are expressed as mean values with standard deviation (± SD) of three replicates. One-way analysis of variance (ANOVA) with Tukey’s test was used for characterization of gelatin and packaging films, whereas two-way ANOVA with Tukey’s tests was used for antimicrobial and preservation assays, to determine significant differences (p < 0.05) among treatments by using SPSS statistical software package (SPSS, version 22.0, USA).”

Result section

The gelatin nanocomposite films restricted the growth of S. aureus in grapes until the 3rd day of storage in comparison to control treatments (unwrapped and plastic wrapped grapes inoculated with S. aureus). Two-way ANOVA revealed that there was significant difference (p < 0.05) in bacterial count when grapes were subjected to different packaging treatments, similarly the bacterial count was significantly different at different storage days (Table S4). After 4th day of storage, grapes packed in nanocomposite films with 0.3% NPs presented significantly low bacterial count (2.39 log CFU/g) in comparison to control treatments (Table 3).  After 5th day of storage, the bacterial count in unwrapped and plastic wrapped grapes was found 6.97 and 6.07 log CFU/g, respectively. However, the microbial count in grapes wrapped in the nanocomposite films containing 0.2% and 0.3% ZnO NPs remained below 4 log CFU/ml until day 5 which is the maximum acceptable microbial limit for fruits suggested by FDA.

Comment# 10: Line 315: please correct typo

Response: Corrected as advised.

Comment# 11: Line 314-315: Are there any studies wherein incorporation of metallic or metallic-oxide NPs lowered the biodegradability? Include studies if possible

Response: The suggested information has been incorporated in the revised manuscript,

“Ediyilyam et al. [25] reported a decrease in the biodegradability of gelatin-CS composite films after the incorporation of silver NPs, which was attributed to antimicrobial effect of silver NPs.”

Comment# 12: Conclusion; Improved packaging is different from active packaging. Please be clear if the objective was to develop improved or active packaging (or both) in the introduction. In addition, include the impact of Np incorporation on barrier properties (improved packaging).

Response: The suggested changes are incorporated in the conclusion and introduction sections of revised manuscript by emphasizing the objective of study to develop gelatin based active packaging with improved barrier properties.

Comment# 13: This manuscript is well written with very few mistakes. However, statistical representation of microbiological analysis has to be checked. In particular, values in Table 3 (and table s2) seem to have been derived from 1 way anova when it must have been from 2-way anova, which would indicate if there is interaction between the factors, storage days and treatment films.

Response: Thank you for the valuable suggestion, two-way ANOVA has been applied and incorporated in the tables and result section of the revised manuscript.

Reviewer 2 Report

 

The manuscript is interesting, but it needs to be improved. Specifically, the extracted gelatine form chicken feet is not sufficiently characterized and this point is a weakness of this work. The characteristics of obtained product must be clearly reported and discussed before its incorporation with chitosan. Extracted gelatine from chicken feet have FTIR similar to that of bovine genatin, but this is not sufficient to highlights its good quality and characteristics. This point must be accurately addressed before reconsideration of manuscript.

Author Response

Reviewer # 2: The manuscript is interesting, but it needs to be improved. Specifically, the extracted gelatine form chicken feet is not sufficiently characterized and this point is a weakness of this work. The characteristics of obtained product must be clearly reported and discussed before its incorporation with chitosan. Extracted gelatine from chicken feet have FTIR similar to that of bovine genatin, but this is not sufficient to highlights its good quality and characteristics. This point must be accurately addressed before reconsideration of manuscript.

Response: Thank you for the suggestion, the extraction of chicken feet gelatin was optimized by using response surface methodology by considering bloom strength which is major attribute in deciding the commercial applications and quality of gelatin. The extracted gelatin was characterized by proximate analysis, FTIR and electrophoretic analysis to determine the molecular weight distribution. Furthermore, as advised by the reviewer, emulsifying properties (emulsion stability index and emulsion activity index) and foaming properties (foam stability and foam capacity) of chicken feet gelatin have been incorporated in the revised manuscript to further elaborate the functional characteristics of extracted gelatin.

Reviewer 3 Report

The present paper describes gelatin extraction from chicken feet and its use in preparing a composite with chitosan and ZnO nanoparticles with antibacterial properties for food packaging. Some interestin work has been reported but it is not clear what is the novelty of the work and, mainly, what is its aim. I would suggest the authors to focus on one aspect (be it gelatin extraction, composite characterization or microbiological studies) and deepen the work.

Author Response

Reviewer # 3: The present paper describes gelatin extraction from chicken feet and its use in preparing a composite with chitosan and ZnO nanoparticles with antibacterial properties for food packaging. Some interesting work has been reported but it is not clear what is the novelty of the work and, mainly, what is its aim. I would suggest the authors to focus on one aspect (be it gelatin extraction, composite characterization or microbiological studies) and deepen the work.

Response: Thank you for the encouraging remarks and valuable suggestion. The aim of the manuscript has been now highlighted in revised manuscript. The study is designed with aim of extracting gelatin with good bloom strength from chicken feet and its application in the formulation of packaging films. The study was designed to extract and characterize gelatin followed by its practical application in the development of biodegradable food packaging. Similar studies have been recently reported by extraction of gelatin and similar polymers from natural sources followed by their application in developing biodegradable food packaging:

“Bangar, S. P., Whiteside, W. S., Ozogul, F., Dunno, K. D., Cavender, G. A., & Dawson, P. (2022). Development of starch-based films reinforced with cellulosic nanocrystals and essential oil to extend the shelf life of red grapes. Food Bioscience, 47, 101621.”

“Salem, A., Jridi, M., Abdelhedi, O., Fakhfakh, N., Nasri, M., Debeaufort, F., & Zouari, N. (2021). Development and characterization of fish gelatin-based biodegradable film enriched with Lepidium sativum extract as active packaging for cheese preservation. Heliyon, 7(10), e08099.”

However, as advised by the reviewer, emulsifying properties (emulsion stability index and emulsion activity index) and foaming properties (foam stability and foam capacity) have been incorporated in the revised manuscript to further elaborate the functional characteristics of extracted gelatin.

Round 2

Reviewer 1 Report

Modifications have been satisfactorily made. 

Reviewer 3 Report

the authors have substantially improved the manuscript, taking into account all the points raised by the reviewers