Effect of Sonication Duration in the Performance of Polyvinyl Alcohol/Chitosan Bilayer Films and Their Effect on Strawberry Preservation
Round 1
Reviewer 1 Report
Lines 1-5: The title does not correspond to what was done in the study. Only film-forming dispersion was treated with sonication particularly the poly(vynil alcohol).
Suggested title:
“Effect of sonication duration in the performance of poly(vynil alcohol)/chitosan bilayer films and their effect on strawberry preservation”
Lines 14-21: The authors can be extending the abstract a little more, highlighting which properties were those that were maintained and that were the main reason for the increase of shelf life.
Lines 79-80: What solution do you refer to, as they say they degassed? It is to poly(vynil alcohol). Which was the concentration of PVA used in the preparation of film-forming dispersions.
Line 95: What was the initial color of the strawberries? and what stage of maturity selected?
Line 178: Why do they carry out the modeling? what will be its usefulness?
Line 294: Please, place the symbology on the foot of figure
Line 303: Why is the behavior compared with unpacked strawberries?
Line 309: According to the variety of strawberries used in this study, what would be the firmness loss to consider a product suitable for consumption?
Line 401: If the decay behavior depend of variety, origin, time of year, etc. then Whay reason to obtain a correlation?
Linea 445: Why the authors stand out the relative humidity? How it influenced in the shelf life of strawberries? What role does the container play? Why the control were strawberries without packaging?.
Author Response
Reviewer 1
Lines 1-5: The title does not correspond to what was done in the study. Only film-forming dispersion was treated with sonication particularly the poly (vynil alcohol).
Suggested title:
“Effect of sonication duration in the performance of poly(vynil alcohol)/chitosan bilayer films and their effect on strawberry preservation”
Re: Yes, we changed the title. Thanks.
Lines 14-21: The authors can be extending the abstract a little more, highlighting which properties were those that were maintained and that were the main reason for the increase of shelf life.
Re: The abstract had been extended. Thanks.
Lines 79-80: What solution do you refer to, as they say they degassed? It is to poly (vynil alcohol). Which was the concentration of PVA used in the preparation of film-forming dispersions.
Re: The CS solution (2, 2.5, 3 wt%) was used in degassed. And the concentration of PVA was 10 wt%, which used in the preparation of film-forming dispersions. Thanks.
Line 95: What was the initial color of the strawberries? and what stage of maturity selected?
Re: The initial color of the strawberries was saturated red color. The L* was 37.01, h* was 29.50, C* was 43.88, which was approximately the same as Campos-Requena et al reported. (Campos-Requena V H, Rivas B L, Pérez M A, et al. Thermoplastic starch/clay nanocomposites loaded with essential oil constituents as packaging for strawberries-In vivo antimicrobial synergy over Botrytis cinerea[J]. Postharvest Biology and Technology, 2017, 129, 29-36.).
We selected the commercial maturity as Lifen et al. refered. (Lifen Z, Shunan Z, Shaojuan L, et al. Combined effects of ultrasound and calcium on the chelate-soluble pectin and quality of strawberries during storage[J]. Carbohydrate Polymers, 2018, 200, 427-435.). Thanks.
Line 178: Why do they carry out the modeling? what will be its usefulness?
Re: The purpose is to predict the shelf life of strawberries. The model was considered transpiration and respiration behavior of strawberries, moisture absorption by packaging, gas and water vapor permeation through the bilayer packaging films to predict changes in relative humidity of packaging headspace as well as moisture condensation within the package to predict the shelf life of strawberries (Jalali A, Rux G, Linke M, et al. Application of humidity absorbing trays to fresh produce packaging: Mathematical modeling and experimental validation[J]. Journal of Food Engineering, 2019, 244, 115-125.). Thanks.
Line 294: Please, place the symbology on the foot of figure
Re: Added. Thanks.
Line 303: Why is the behavior compared with unpacked strawberries?
Re: We set the unpacked strawberries as the negative control, and the PVA films packaged strawberries as the positive control. Then we compared the firmness of unpackaged strawberries with that of packaged strawberries, the preservation effect of different films was explored. (Ye J, Wang S, Lan W, et al. Preparation and properties of polylactic acid-tea polyphenol-chitosan composite membranes[J]. International journal of biological macromolecules, 2018, 117: 632-639.). Thanks.
Line 309: According to the variety of strawberries used in this study, what would be the firmness loss to consider a product suitable for consumption?
Re: When the strawberries were fully ripe, the color of strawberries was bright red and full, the aroma was the best. At this time, the strawberry hardness is about 2 N. After which the strawberry continues to soften, and the various nutrients decrease at the same time. When the hardness is below 0.5 N, the no longer suitable for consumption (Avalos-Llano K R , Martín-Belloso, Olga, Soliva-Fortuny R . Effect of pulsed light treatments on quality and antioxidant properties of fresh-cut strawberries[J]. Food Chemistry, 2018, 264, 393-400.). Thanks.
Line 401: If the decay behavior depends of variety, origin, time of year, etc. then Whay reason to obtain a correlation?
Re: Although the decay behavior was related to variety, origin, time of year, etc, it is not the determining factor. Strawberry is a fruit with high transpiration rate, and its decay behavior depends more on temperature change of the environment. Therefore, the correlation between temperature and decay behavior is needed to predict the shelf life of strawberries (Mercier S, Brecht J K, Uysal I. Commercial forced-air precooling of strawberries: A temperature distribution and correlation study[J]. Journal of Food Engineering, 2019, 242, 47-54.). Thanks.
Linea 445: Why the authors stand out the relative humidity? How it influenced in the shelf life of strawberries? What role does the container play? Why the control were strawberries without packaging?
Re: The surrounding atmosphere and storage temperature will effects the water loss rate of strawberries. As many paper reported that strawberries should be stored at low vapor pressure and low temperature. So the relative humidity was important for strawberries. When the relative humidity of the environment is similar to that of strawberry, it has the best effect on strawberry preservation (Burg S P, Davenport T L. Heat transfer, mass transport and horticultural commodity water loss during hypobaric storage[J]. Scientia horticulturae, 2017, 225, 561-566.) (Jalali A, Rux G, Linke M, et al. Application of humidity absorbing trays to fresh produce packaging: Mathematical modeling and experimental validation[J]. Journal of Food Engineering, 2019, 244, 115-125.). And some paper proved that maintain a desirable relative humidity will reduce the condensation of packaged strawberries (Bovi G G, Rux G, Caleb O J, et al. Measurement and modelling of transpiration losses in packaged and unpackaged strawberries[J]. Biosystems engineering, 2018, 174, 1-9.).
The container has the function of packaging and protection. The composite membrane as a container has certain permeability and water permeability and antibacterial property, so it can reduce the respiration of strawberry to a certain extent, and protect the strawberry from microbial infection (Liu Y, Wang S, Lan W. Fabrication of antibacterial chitosan-PVA blended film using electrospray technique for food packaging applications[J]. International journal of biological macromolecules, 2018, 107, 848-854.) (Noshirvani N, Ghanbarzadeh B, Gardrat C, et al. Cinnamon and ginger essential oils to improve antifungal, physical and mechanical properties of chitosan-carboxymethyl cellulose films[J]. Food Hydrocolloids, 2017, 70, 36-45.).
We set the strawberries without packaging as the negative control, compared with positive control (PVA films packaged strawberries), so it is easy to explore the preservation effect of different chitosan concentrations on strawberries (Hajji S, Younes I, Affes S, et al. Optimization of the formulation of chitosan edible coatings supplemented with carotenoproteins and their use for extending strawberries postharvest life[J]. Food hydrocolloids, 2018, 83, 375-392.). Thanks.
Reviewer 2 Report
Authors developed bilayer films based on PVA and Chitosan and evaluated the effect of preparation conditions (ultrasonic duration) and chitosan content (2, 2.5 and 3% w/v) on the efficiency of strawberry preservation at 20°C.
The manuscript is well structured and clearly organized. Thus, it contains all essential sections including title, abstract, keywords, introduction, materials and methods, results, discussion, and a list of valuable references. The English language is clean and clear. However, there are several issues that lead to Reconsider after Major Revisions of the manuscript.
Major findings are:
· The abstract is too short and general. Please, describe briefly all treatments, the main methods and summarized the results in terms of OP, WVP, mechanical properties and color, firmness, soluble solids content (SSC), titratable acidity (TA), weight loss, and percentage of decay of strawberries. In other words, the manuscript deserves better abstract.
· Please rewrite the main aim of study at the end of introduction. In particular preparation conditions (ultrasonic duration) is not considered in this paragraph.
· The reason of selectin 2, 2.5 and 3% Chitosan is not clear. Chitosan is an expensive biopolymer and also due to the high viscosity it is difficult to cast chitosan FFS higher than 2 %.
· The concept of PVA/CS bilayer film and PVA/CS blend films are mixed together several times (e.g. Lines 58, 61 and 241 and …).
· For measuring mechanical properties and WVP, standard methods (ASTM standards) should be applied (e.g. Line 103). Please state WVP calculation formula and units for calculation the formula.
· Please add a new section in M&M to explain ATR-FT-IR analysis, spectra wavenumber range, number of scans and spectral resolution.
· Line 209: The positive effect of CS content on solution viscosity is not statistically calculated, however it is stated inside the paragraph. Please, use capital letter in Tab.2 to show significant difference in each column if you want to state the difference inside the text.
· Due to the limited penetration depth (only a few micrometers) of infrared radiation into the sample in the ATR-FT-IR measurement geometry, the spectra should be measured from the bottom- and the top-side of the bilayer films. Moreover, the result of PVA/CS-2 and PVA/CS-3 is missing in Figure.1. Overall, it is not recommended to use ATR-FT-IR to study films wit high thickness.
· Line 239 and 240: “ultimate stress of 25.08 ± 4.32 MPa and a specific deformation of 72.97 ± 7.26 %” These values are not presented inside the Tab. 3.
· Line 248: “Young’s modulus” is not presented inside the Tab.3.
· Authors did not consider the ultrasound treatment effects for OP and WVP results (e.g. Line 256-274 Tab.4.).
· Line 364: Please, control pH values statistically for each day of analysis and use capital letter in Tab.5 to show if there is an significant difference in each column for treatments (control, PVA, PVA/CS-2 and ...) or not. Moreover, in line 360 edit the pH value for PVA/CS-2.5 after 21 days of analysis to “3.65”
· The title and caption of all figures and tables should edit and state precisely again.
· Authors should use the Table option of Microsoft Word to create tables.
Some other minor corrections are presented below:
· Line 10: “Correspondence” repeated two times. Pls delete one of them.
· Line 22: Keywords please add “biodegradable packaging or strawberry packaging or strawberry preservation”
· Line 20: “Botrytis cinereal” edit to italic form.
· Line 78 and Line 86: it is better to switch “2.1. ultrasonication” and “2.2.CS/PVA film preparation” paragraphs.
· Line 79: “solution” it is not clear which solution?
· Line 86: Please edit “CS/PVA” to “PVA/CS” to keep consistency in writing PVA/CS.
· Line 87: “cm2”
· Line 108: Please cite the ASTM method for mechanical properties measurement.
· Line 115: Citation CB/T 26253 (GB/T, 2010) is not found in the reference list. Please, state how WVP calculated with a formula.
· Line 118: sentence is not complete?!!! “The UV-vis for the transmission spectra of the film specimens was recorded from”
· Line 209 and 252: Authors should use the Table option of Microsoft Word to create tables.
· Please edit “Table 2. The effect of ultrasonic treatment on film forming solution viscosity”
· Line 193: “PVA-3” edit to “PVA/CS-3”
· Line 236: Fig.1. please add absorbance for vertical axis title.
· Line 238: please delete “one” from beginning of the paragraph.
· Line 250: “The physical” edit to “The mechanical”
· Line 272: “Table 4. OP and WVP values of films based on PVA as control and bilayer films based on PVA and different concentration of CS” .
· Line 273: inside the Tab. 4 value for WVP for PVA/CS-3 film “22.99±5.57b” should edit to “22.99±5.57a”
· Lines 289-292: In Fig. 2. it seems PVA/CS-3 had the lowest value for weight loss. Moreover, back to the OP and WVP results, there is not any significant differences between PVA and PVA/CS-2 and PVA/CS-2.5. I would suggest rewriting these lines again (Lines 289-292).
· Fig.2 : Please change the symbols size or use different color to have clear and readable graphs.
· Line 297 and 316: Please switch “3.6. Firmness” paragraph with “3.7. Decay” paragraph to have consistency in graph numbers.
· Line 357 and 369: Please switch “3.10. pH” paragraph with “3.11. Ascorbic acid content” paragraph to have consistency in graph numbers.
Author Response
Reviewer 2
Authors developed bilayer films based on PVA and Chitosan and evaluated the effect of preparation conditions (ultrasonic duration) and chitosan content (2, 2.5 and 3% w/v) on the efficiency of strawberry preservation at (5±2) °C.
The manuscript is well structured and clearly organized. Thus, it contains all essential sections including title, abstract, keywords, introduction, materials and methods, results, discussion, and a list of valuable references. The English language is clean and clear. However, there are several issues that lead to Reconsider after Major Revisionsof the manuscript.
Major findings are:
The abstract is too short and general. Please, describe briefly all treatments, the main methods and summarized the results in terms of OP, WVP, mechanical properties and color, firmness, soluble solids content (SSC), titratable acidity (TA), weight loss, and percentage of decay of strawberries. In other words, the manuscript deserves better abstract.
Re: Yes, the abstract had been extended. Thanks.
Please rewrite the main aim of study at the end of introduction. In particular preparation conditions (ultrasonic duration) is not considered in this paragraph.
Re: We rewrote this part. Thanks.
The reason of selectin 2, 2.5 and 3% Chitosan is not clear. Chitosan is an expensive biopolymer and also due to the high viscosity it is difficult to cast chitosan FFS higher than 2 %.
Re: In our experiment, we chose the low-viscosity chitosan (food grade, deacetylation degree = 90 %, Mw = 165,000 Da). When the concentration was 2%, it has good fluidity. When the concentration over 3%, it couldnot to form films evenly. So we chose chitosan with slightly higher concentration to improve the antimicrobial property of the bilayer film and prolong the shelf life of strawberries (Ventura-Aguilar R I, Bautista-Baños S, Flores-García G, et al. Impact of chitosan based edible coatings functionalized with natural compounds on Colletotrichum fragariae development and the quality of strawberries[J]. Food chemistry, 2018, 262, 142-149.). Thanks.
The concept of PVA/CS bilayer film and PVA/CS blend films are mixed together several times (e.g. Lines 58, 61 and 241 and …).
Re: We corrected the wrong descriptions. Thanks.
For measuring mechanical properties and WVP, standard methods (ASTM standards) should be applied (e.g. Line 103). Please state WVP calculation formula and units for calculation the formula.
Re: Added. Thanks.
Please add a new section in M&M to explain ATR-FT-IR analysis, spectra wavenumber range, number of scans and spectral resolution.
Re: Added. Thanks.
Line 209: The positive effect of CS content on solution viscosity is not statistically calculated, however it is stated inside the paragraph. Please, use capital letter in Tab.2 to show significant difference in each column if you want to state the difference inside the text.
Re: Table 2 was replaced. Thanks.
Due to the limited penetration depth (only a few micrometers) of infrared radiation into the sample in the ATR-FT-IR measurement geometry, the spectra should be measured from the bottom- and the top-side of the bilayer films. Moreover, the result of PVA/CS-2 and PVA/CS-3 is missing in Figure.1. Overall, it is not recommended to use ATR-FT-IR to study films with high thickness.
Re: The thickness of the bilayer films was only 50 μm, and it could be seen from the infrared spectrogram to distinguish the difference between PVA and CS films. The peak of 1580 cm-1 in chitosan appears in the all bilayer films, indicated that there was a reaction between the two substances (Zhuang C, Jiang Y, Zhong Y, et al. Development and characterization of nano-bilayer films composed of polyvinyl alcohol, chitosan and alginate[J]. Food Control, 2018, 86, 191-199.). And the result of PVA/CS-2 and PVA/CS-3 was added in Figure 1. Thanks.
Line 239 and 240: “ultimate stress of 25.08 ± 4.32 MPa and a specific deformation of 72.97 ± 7.26 %” These values are not presented inside the Tab. 3.
Re: The error was revised. Thanks.
Line 248: “Young’s modulus” is not presented inside the Tab.3.
Re: We deleted it. Thanks.
Authors did not consider the ultrasound treatment effects for OP and WVP results (e.g. Line 256-274 Tab.4.)
Re: We selected the optimal ultrasonic time by the viscosity of the solution and the mechanical properties of the bilayer films in our studies. We only tested OP and WVP under the best ultrasonic condition (25 minutes, at this time, the film liquid viscosity is moderate and has good mechanical properties) (Chemat F , Zill-e-Huma, Khan M K . Applications of Ultrasound in Food Technology: Processing, Preservation and Extraction[J]. Ultrasonics Sonochemistry, 2010, 18, 813-835.). Thanks.
Line 364: Please, control pH values statistically for each day of analysis and use capital letter in Tab.5 to show if there is an significant difference in each column for treatments (control, PVA, PVA/CS-2 and ...) or not. Moreover, in line 360 edit the pH value for PVA/CS-2.5 after 21 days of analysis to “3.65”
Re: Corrected. Thanks.
The title and caption of all figures and tables should edit and state precisely again.
Re: Revised. Thanks.
Authors should use the Table option of Microsoft Word to create tables.
Re: We changed the all tables. Thanks.
Some other minor corrections are presented below:
Line 10: “Correspondence” repeated two times. Please delete one of them.
Re: Deleted. Thanks.
Line 22: Keywords please add “biodegradable packaging or strawberry packaging or strawberry preservation”
Re: Added. Thanks.
Line 20: “Botrytis cinereal” edit to italic form.
Re: Done. Thanks.
Line 78 and Line 86: it is better to switch “2.1. ultrasonication” and “2.2.CS/PVA film preparation” paragraphs.
Re: Done. Thanks.
Line 79: “solution” it is not clear which solution?
Re: Yes, the solution is the CS solution (2, 2.5, 3 wt%). Thanks.
Line 86: Please edit “CS/PVA” to “PVA/CS” to keep consistency in writing PVA/CS.
Re: Done. Thanks.
Line 87: “cm2”
Re: Corrected. Thanks.
Line 108: Please cite the ASTM method for mechanical properties measurement.
Re: Added. Thanks.
Line 115: Citation CB/T 26253 (GB/T, 2010) is not found in the reference list. Please, state how WVP calculated with a formula.
Re: The reference was added. Thanks.
Line 118: sentence is not complete?!!! “The UV-vis for the transmission spectra of the film specimens was recorded from”
Re: We corrected the wrong descriptions. Thanks.
Line 209 and 252: Authors should use the Table option of Microsoft Word to create tables.
Re: We replaced the all tables. Thanks.
Please edit “Table 2. The effect of ultrasonic treatment on film forming solution viscosity”
Re: Revised. Thanks.
Line 193: “PVA-3” edit to “PVA/CS-3”
Re: Done. Thanks.
Line 236: Fig.1. please add absorbance for vertical axis title.
Re: Added. Thanks.
Line 238: please delete “one” from beginning of the paragraph.
Re: Done. Thanks.
Line 250: “The physical” edit to “The mechanical”
Re: Done. Thanks.
Line 272: “Table 4. OP and WVP values of films based on PVA as control and bilayer films based on PVA and different concentration of CS”.
Re: We corrected the wrong descriptions. Thanks.
Line 273: inside the Tab. 4 value for WVP for PVA/CS-3 film “22.99±5.57b” should edit to “22.99±5.57a”
Re: Yes, changed. Thanks.
Lines 289-292: In Fig. 2. it seems PVA/CS-3 had the lowest value for weight loss. Moreover, back to the OP and WVP results, there is not any significant differences between PVA and PVA/CS-2 and PVA/CS-2.5. I would suggest rewriting these lines again (Lines 289-292).
Re: We re-wrote it. Thanks.
Fig.2: Please change the symbols size or use different color to have clear and readable graphs.
Re: Changed. Thanks.
Line 297 and 316: Please switch “3.6. Firmness” paragraph with “3.7. Decay” paragraph to have consistency in graph numbers.
Re: Corrected. Thanks.
Line 357 and 369: Please switch “3.10. pH” paragraph with “3.11. Ascorbic acid content” paragraph to have consistency in graph numbers.
Re: Yes, corrected. Thanks.
Round 2
Reviewer 2 Report
The changes have been made. I think the bibliography should be integrated with these recent publications and then it can be accepted for printing.
Food Packaging and Shelf Life
Volume 19, March 2019, Pages 31-39
Comparative analysis of blend and bilayer films based on chitosan and gelatin enriched with LAE (lauroyl arginate ethyl) with antimicrobial activity for food packaging applications
and:
Food Packaging and Shelf Life
Volume 18, December 2018, Pages 95-100
Properties of poly(vinyl alcohol) films as determined by thermal curing and addition of polyfunctional organic acids
Author Response
Responses to Reviewer’s Comments
Comments from the editors and reviewers
Reviewer 1
The changes have been made. I think the bibliography should be integrated with these recent publications and then it can be accepted for printing.
Food Packaging and Shelf Life
Volume 19, March 2019, Pages 31-39
Comparative analysis of blend and bilayer films based on chitosan and gelatin enriched with LAE (lauroyl arginate ethyl) with antimicrobial activity for food packaging applications
and:
Food Packaging and Shelf Life
Volume 18, December 2018, Pages 95-100
Properties of poly(vinyl alcohol) films as determined by thermal curing and addition of polyfunctional organic acids
Re: We added those references. Thanks.
