Influence of Non-Thermal Plasma on the Quality and Nutritional Content of Palm Dates

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

 

 Comments and Suggestions for Authors

Title: Influence of non-thermal plasma on the quality and nutritional content of palm dates

Authors studied the effect of SDBD plasma on the bioactive material, chemical content, and Hydroxymethylfurfural (HMF) of some palm date varieties. The SDBD is useful to prevent fungal diseases that seriously affect agricultural production and the food industry. This method are more sustainable and innovative and have a great potential for industrial applications due to its non-thermal operation, short processing time, energy efficiency. According with authors in this study is pointed out that this technology might be safe, did not produce remarkable changes in the quality of palm date varieties. Furthermore, HFM values, the antioxidant activity, and the total phenol contents of treated palm date varieties were notably changed under specific conditions of SDBD plasma treatment, which led to a rise in the quality of palm date varieties.

 

Dear Reviewer, thanks a lot for your valuable comments and suggestions. Herein you will find the response for each question point by point.

 

However, the text is not well edited, presenting several anomalies that must be corrected before publication

Dear Reviewer, thanks a lot for your valuable comments and suggestions.

The edit has been achieved.

 

References must be numbered in order of appearance in the text (including table captions and figure legends) and listed individually at the end of the manuscript.

Dear Reviewer, thanks a lot for your valuable comments and suggestions.

The edit has been achieved.

 

Experimental setup: line 89- p in capital letter.

Response: Thank you for this comment. The change has been achieved.

 

Line 93- in he teflox box, the letter t was missing

Response: Thank you for this comment. The change has been achieved.

 

Line 145 p in capital letter

Response: Thank you for this comment. The change has been achieved.

 

Line 146 and line 150 delete moreover

Response: Thank you for this comment. The change has been achieved.

 

 

paragraph 2.5: this paragraph needs to be described with sufficient detail to allow others to replicate and build on published results. It must be completely rewritten.

 

For example: Proximate analysis, Amino Acid, mineral, polyphenols…

All methods must be followed by bibliographic reference

Dear Reviewer, thanks a lot for your valuable comments and suggestions.

The edit has been achieved.

 

3. Results and Discussions (delete all empty lines)

Response: Thank you for this comment. The change has been achieved.

 

Line 248- delete it and write Autors found that…

Response: Thank you for this comment. The change has been achieved.

 

Line 276- Still and all – delete the sentence

Response: Thank you for this comment. The change has been achieved.

 

Line 301- delete however

Response: Thank you for this comment. The change has been achieved.

 

Line 309-311- rewrite the sentence

Response: Thank you for this comment. The sentence has been rewritten.

 

Line 319- change “consequences” with “result”

Response: Thank you for this comment. The change has been achieved.

 

Line 339- Fresh in lowercase letter

Response: Thank you for this comment. The change has been achieved.

 

Line 419 – add occurs to the sentence: Zhou et al. (2018) proved that no significant changes in the content of both vitamin C and 419 beta-carotene of L. barbarum samples during non-thermal plasma exposure processing

Response: Thank you for this comment. The change has been achieved.

 

 

The last two paragraphs are not sufficiently discussed, especially the paragraph on amino acids.

Response: Thank you for this comment. The edit has been achieved

 

Principal component analysis: delete the punctuation mark from the title

The PCA have to be better rewritten in order to clarify some concept. Moreover is not correct use numbers instead of the considered variables.

Response: Thank you for this comment. The PCA has been rewritten

 

 

 

References

The references list must be checked, many references are not correctly written.

Response: Thank you for this comment. The references have been rewritten correctly.

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

In their manuscript “Influence of non-thermal plasma on the quality and nutritional content of palm dates”, the authors discovered that non-thermal plasma can kill agricultural microbes, increase phenolic and antioxidant values, and decrease the hydroxymethylfurfural values of palm seeds, without significant changes to their other chemical compositions (e.g., carbohydrates, fats, proteins, vitamins, amino acids, minerals etc.). I think that this work could be suitable for publication in Applied Sciences, following a minor revision relating to suggestions below -

 

Overall -

The authors have chosen an interesting research topic, conducted thorough experimental measurements and analysis, and have written a manuscript that is very rich in content. I think that this manuscript could be better structured by moving the key results up front. The authors could also consider further rationalizing why only certain chemical compositions have changed (e.g., HMF, phenolic values, and antioxidant values) in both the results/ discussion section and in the conclusion section. Specifically, are such changes related to their chemical reactivity (or the specific functional groups that can be oxidized) and the type of plasma used? Or/and are they related to the treatment depth of the plasma and the position of chemicals that can directly interact with the plasma (e.g., chemical contents near the surface of the sample may be more likely to undergo chemical changes compared to chemical contents away from the surface).

 

Suggestions on clarifying the experimental design –

·       Page 2, line 91: why in a Teflon box? Potential discharges onto Teflon may produce fluorinated compounds or HF which could be toxic and dangerous to consumers.

·       Page 3, lines 100-101: Does 5-10kv in your setup lead to corona or spark discharge?

Suggestions on improving the presentation of results –

·       Figure 1d – The authors can perhaps zoom into the 300-420nm region to improve clarity

·       Figure 2 – There is no significant difference in total carbohydrates, sugars, proteins nor fat values between the control and the treated samples. I’m not sure if the small differences described between lines 270-320 are considered as key results. I recommend 1) the authors to correct the number of significant figures used for results (e.g., 24 +/- 2 instead of 23.82 +/- 1.95) and 2) move this entire section to a later location in the manuscript.

·       Figure 3 and sections 3.4., 3.5., and 3.6 – results on the total phenol, antioxidant, and HMF values are very interesting. I can see a clear difference between the control and the treated samples. I recommend discussing these results first, as they are the highlights of this paper.

·       Figures 4 and 5: I found these bar charts only useful as qualitative representations. Quantitatively, they are hard to read, and they provide no information on uncertainties (nor experimental variations measured).

 

Additional comments:

I recommend this manuscript to go through an English editing service prior to publication. Examples of language issues include but not limited to the following -

·       Page 1, line 17: “the total phenolic content” instead of “the total phenolic”

·       Page 1, line 21: “the HMP was not detected” instead of “the HMF not detected”

·       Page 1, lines 30 and 35: what does “foodstuffs” mean? Perhaps use “food items” instead?

·       Page 2, lines 81-82 “due to their high cost or slow speed” instead of “due to their high costly or too slow).

 

Author Response

Reviewer 2

In their manuscript “Influence of non-thermal plasma on the quality and nutritional content of palm dates”, the authors discovered that non-thermal plasma can kill agricultural microbes, increase phenolic and antioxidant values, and decrease the hydroxymethylfurfural values of palm seeds, without significant changes to their other chemical compositions (e.g., carbohydrates, fats, proteins, vitamins, amino acids, minerals etc.). I think that this work could be suitable for publication in Applied Sciences, following a minor revision relating to suggestions below –

 

Dear Reviewer, thanks a lot for your valuable comments and suggestions. Herein you will find the response for each question point by point.

 

Overall -

The authors have chosen an interesting research topic, conducted thorough experimental measurements and analysis, and have written a manuscript that is very rich in content. I think that this manuscript could be better structured by moving the key results up front.

 

Response: Thanks a lot for your valuable comment and suggestion.

The change has been achieved.

 

 

The authors could also consider further rationalizing why only certain chemical compositions have changed (e.g., HMF, phenolic values, and antioxidant values) in both the results/ discussion section and in the conclusion section. Specifically, are such changes related to their chemical reactivity (or the specific functional groups that can be oxidized) and the type of plasma used? Or/and are they related to the treatment depth of the plasma and the position of chemicals that can directly interact with the plasma (e.g., chemical contents near the surface of the sample may be more likely to undergo chemical changes compared to chemical contents away from the surface).

Response: Thanks a lot for your valuable comment, the change has been achieved.

Most ready-to-eat fruits and vegetables contain high levels of free water, which, when exposed to non-thermal plasma, can cause undesirable quality changes. However, because non-thermal plasma cannot penetrate the product, these changes occur only on the surface and do not affect the fresh produce's intrinsic composition or nutritional properties.

On the other hand, the dosage and power of the used SDBD plasma did not have the same effect on the chemical components of dates. However, the SDBD plasma dosage and power were able to influence on the active component eg, HMF, phenolic, and antioxidant activity levels.

 

Suggestions on clarifying the experimental design –

 

• Page 2, line 91: why in a Teflon box?

Response: Thank you for this question. In this work we have been used Teflon box to concentrate the generated species on samples.

 

 Potential discharges onto Teflon may produce fluorinated compounds or HF which could be toxic and dangerous to consumers.

Response: Thank you for this comment. There is no contact between plasma discharges and Teflon box, so that, the possibility of generation fluorinated compounds or HF do not occur in this design.  

 

• Page 3, lines 100-101: Does 5-10kv in your setup lead to corona or spark discharge?

Response: Thank you for this comment. In this work 5-10kv generate spark discharge 

 

Suggestions on improving the presentation of results –

• Figure 1d – The authors can perhaps zoom into the 300-420nm region to improve clarity

Response: Thank you for this comment, the change has achieved.

 

   Figure 2 – There is no significant difference in total carbohydrates, sugars, proteins nor fat values between the control and the treated samples. I’m not sure if the small differences described between lines 270-320 are considered as key results. I recommend 1) the authors to correct the number of significant figures used for results (e.g., 24 +/- 2 instead of 23.82 +/- 1.95) and 2) move this entire section to a later location in the manuscript.

Response: Thanks a lot for your valuable comment and suggestion.

The change has been achieved.

 

 

    Figure 3 and sections 3.4., 3.5., and 3.6 – results on the total phenol, antioxidant, and HMF values are very interesting. I can see a clear difference between the control and the treated samples. I recommend discussing these results first, as they are the highlights of this paper.

Response: Thanks a lot for your valuable comment and suggestion.

The change has been achieved.

 

 

    Figures 4 and 5: I found these bar charts only useful as qualitative representations. Quantitatively, they are hard to read, and they provide no information on uncertainties (nor experimental variations measured).

Response: Thanks a lot for your valuable comment and suggestion.

               I agree with you. Figure 4 and 5 have been converted to tables.

 

 

Additional comments:

I recommend this manuscript to go through an English editing service prior to publication.

Response: Thanks a lot for your valuable comment and suggestion.

The manuscript has been revised by an English native speaker.

 

 

Examples of language issues include but not limited to the following -

• Page 1, line 17: “the total phenolic content” instead of “the total phenolic”

Response: Thank you for this comment. The change has been achieved.

 

• Page 1, line 21: “the HMP was not detected” instead of “the HMF not detected”

Response: Thank you for this comment. The change has been achieved.

 

• Page 1, lines 30 and 35: what does “foodstuffs” mean? Perhaps use “food items” instead?

Response: Thank you for this comment. The change has been achieved.

 

• Page 2, lines 81-82 “due to their high cost or slow speed” instead of “due to their high costly or too slow).

Response: Thank you for this comment. The change has been achieved.

 

 

 

Author Response File: Author Response.doc

Reviewer 3 Report

The subject of the article can be of interest to the multidisciplinary community working in the possible application of low temperature plasma in the broad field of plasma agriculture. The results are in line with the current findings and knowledge, but a major improvement should be done on the paper. In particular the section regarding the plasma device and plasma characterization are really poor, and graphical outputs.

In order to make the results reproducible by other group further details should be given on the sdbd device and experimental conditions used (waveforms, energy or power, dimensithe ons, flow rate of gases, residence times of treated gases etc., you can take as a reference other paper cited in you ref list).

You put a quite big emphasis on the emission spectroscopy results also in the abstract (''N2SPS, N2FNS, and hydroxyl radical have emerged in the emission spectrum of the plasma from SDBD.'').

The plasma characterisation by spectroscopy technique is quite disappointing. The monochromator used for the spectroscopy is really low resolution, so not big information can be deduced from spectra. Could you take emission spectra with higher resolution?

For instance one main point to understand the production of species from your device is the gas temperature in plasma. Could it be possible to detect with sufficient resolution the SPS(0,0) band of Nitrogen? Moreover the identification of band, maybe due to very low spectral resolution is completely wrong (also reported wavelength).

I assume that the HV is of AC type, continuous, and that you cannot precisile trigger on the streamer event. This means that on the time and space averaged spectrum strong emissions from FNS with respect to SPS should be difficult to identify. Moreover, it is quite surprising the strong emission from OH radical. I would rather expect emission spectra completely dominated by SPS emission. To identify precisely the species you should be able to resolve the spectra feature (that are not reported). It is also surprising that you cannot observe any emission fro oxygen atoms.

What is the spectral sensitivity of your device? 

You have to check the spectral feature of Nitrogen by referring to one of the reference papers for people working in the field ( 10.1063/1.555546). Alternatively, you can use available software such as Spectrum Analyzer Homepage (muni.cz) that will enable you also to identify transition (vibrational levels, bands etc). 

From the point of view of biological experiment I have tried to understand how do you run experiment on A.niger, but I could not understand it, maybe is my fault. For instance, what do you mean by ''In all runs, a 5mm disc of A.Niger has been treated.''  Please note that A.Niger should be italic.

Overall try to improve the experimental section by checking the text, and by adding also schematic and or picture of the apparatus design and experimental setup.

Regarding the results overall the graph used is difficult to read, the size of character is too small. In particular, I find it quite difficult to read figures 4 and 5. I suggest changing the type of graph and adding tables, reporting the error and statical significance of the data.

In section 3.3 there is no discussion about the possible role of plasma in the increase in antioxidants. I would rather expect that using an oxidizing environment such as plasma there would be a reduction, not an increase. Why? Possible explanation?

Just a curiosity. Section 3.8 proteins, did you verify something about the solubility of proteins before and after plasma treatment?

Please check the English spelling. As an example line 521-522 ''SDBD plasma compared with they are untreated.'' ??

 

 

Author Response

                                                  Reviewer3

The subject of the article can be of interest to the multidisciplinary community working in the possible application of low temperature plasma in the broad field of plasma agriculture. The results are in line with the current findings and knowledge, but a major improvement should be done on the paper. In particular the section regarding the plasma device and plasma

Dear Reviewer, thanks a lot for your valuable comments and suggestions. Herein you will find the response for each question point by point.

In order to make the results reproducible by other group further details should be given on the sdbd device and experimental conditions used (waveforms, energy or power, dimensithe ons, flow rate of gases, residence times of treated gases etc., you can take as a reference other paper cited in you ref list)

Response: Thank you for this comment, the editing has been achieved.

You put a quite big emphasis on the emission spectroscopy results also in the abstract (''N2SPS, N2FNS, and hydroxyl radical have emerged in the emission spectrum of the plasma from SDBD.'').

Response: Thank you for this comment.

The plasma characterisation by spectroscopy technique is quite disappointing. The monochromator used for the spectroscopy is really low resolution, so not big information can be deduced from spectra. Could you take emission spectra with higher resolution?

Response: Thank you for this comment. Unfortunately, we non having except this spectroscopy.

For instance one main point to understand the production of species from your device is the gas temperature in plasma. Could it be possible to detect with sufficient resolution the SPS(0,0) band of Nitrogen? Moreover, the identification of band, maybe due to very low spectral resolution is completely wrong (also reported wavelength).

Response: Thank you for this comment. Unfortunately, we non having except this spectroscopy. On the other hand, OES result well agree with many reference, pleases see the following,

Kim, Yeong Woon, et al. "LLC inverter design for driving surface DBD optimized for airborne bacteria inactivation." Journal of Power Electronics 21.12 (2021): 1878-1887.‏

Piferi, Cecilia, et al. "Current filaments in asymmetric surface dielectric barrier discharge." Applied Sciences 11.5 (2021): 2079.‏

Motyka-Pomagruk, Agata, et al. "Implementation of a non-thermal atmospheric pressure plasma for eradication of plant pathogens from a surface of economically important seeds." International Journal of Molecular Sciences 22.17 (2021): 9256.‏

Ambrico, Paolo F., et al. "Surface Dielectric Barrier Discharge plasma: A suitable measure against fungal plant pathogens." Scientific Reports 10.1 (2020): 1-17.‏

I assume that the HV is of AC type, continuous, and that you cannot precisile trigger on the streamer event. This means that on the time and space averaged spectrum strong emissions from FNS with respect to SPS should be difficult to identify. Moreover, it is quite surprising the strong emission from OH radical. I would rather expect emission spectra completely dominated by SPS emission. To identify precisely the species you should be able to resolve the spectra feature (that are not reported). It is also surprising that you cannot observe any emission fro oxygen atoms.

Response: Thank you for this comment. Unfortunately, we non having except this spectroscopy. On the other hand, OES result well agree with many references, pleases see the following,

Kim, Yeong Woon, et al. "LLC inverter design for driving surface DBD optimized for airborne bacteria inactivation." Journal of Power Electronics 21.12 (2021): 1878-1887.‏

Piferi, Cecilia, et al. "Current filaments in asymmetric surface dielectric barrier discharge." Applied Sciences 11.5 (2021): 2079.‏

Motyka-Pomagruk, Agata, et al. "Implementation of a non-thermal atmospheric pressure plasma for eradication of plant pathogens from a surface of economically important seeds." International Journal of Molecular Sciences 22.17 (2021): 9256.‏

Ambrico, Paolo F., et al. "Surface Dielectric Barrier Discharge plasma: A suitable measure against fungal plant pathogens." Scientific Reports 10.1 (2020): 1-17.‏

 

What is the spectral sensitivity of your device?

Response: Thank you for this question, The resolution of the spectrometer  is  0.5 nm FWHM.

You have to check the spectral feature of Nitrogen by referring to one of the reference papers for people working in the field ( 10.1063/1.555546). Alternatively, you can use available software such as Spectrum Analyzer Homepage (muni.cz) that will enable you also to identify transition (vibrational levels, bands etc). 

Response: Thank you for this comment. The software has been used.

From the point of view of biological experiment I have tried to understand how do you run experiment on A.niger, but I could not understand it, maybe is my fault. For instance, what do you mean by ''In all runs, a 5mm disc of A.Niger has been treated.''  Please note that A.Niger should be italic.

Response: Thank you for this comment. 'In all runs, a 5mm disc of A.Niger has been treated.''  It manes that, samples of A.Niger is disc and have constant radius equal 5mm.

Overall try to improve the experimental section by checking the text, and by adding also schematic and or picture of the apparatus design and experimental setup.

Response: Thank you for this comment, the editing has been achieved.

Regarding the results overall the graph used is difficult to read, the size of character is too small. In particular, I find it quite difficult to read figures 4 and 5. I suggest changing the type of graph and adding tables, reporting the error and statical significance of the data.

Response: Thanks a lot for your valuable comment and suggestion.

                         I agree with you. Figure 4 and 5 have been converted to tables.

 

In section 3.3 there is no discussion about the possible role of plasma in the increase in antioxidants. I would rather expect that using an oxidizing environment such as plasma there would be a reduction, not an increase. Why? Possible explanation?

Response: Thank you for this question.

Non-thermal plasma treatment triggered the elevation of phenylpropanoids and ROS metabolism, as well as the enhancement of enzyme activities and the activation of associated gene expression, and therefore increased the antioxidant activity of fruit. On the other hand, treatment with non-thermal plasma showed the ability to boost phenolic accumulation and, therefore, antioxidant activity.

Just a curiosity. Section 3.8 proteins, did you verify something about the solubility of proteins before and after plasma treatment?

Thank you for this question, the solubility of proteins before and after plasma treatment did not verify in this work.

Please check the English spelling. As an example line 521-522 ''SDBD plasma compared with they are untreated.'' ??

Response: Thanks a lot for your valuable comment and suggestion.

The manuscript has been revised by an English native speaker.

 

 

Author Response File: Author Response.docx