A Novel Technique Using Confocal Raman Spectroscopy Coupled with PLS-DA to Identify the Types of Sugar in Three Tropical Fruits
, Jorge L. Maicelo-Quintana 2, Geidy Salón-Llanos 1, Miguel Barrena 3, Lucas D. Muñoz-Astecker 1, Ilse S. Cayo-Colca 2, Llisela Torrejón-Valqui 1 and EfraÃn M. Castro-Alayo 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors analyzed the different glucose contents in three tropical fruits by confocal Raman spectroscopy combined with the partial least squares method. And discussed the effects of various pretreatment methods on the model's accuracy. It has certain scientific research value.
It is recommended that the author increase the quantity of three tropical fruits and use more analytical techniques, such as HPLC, HPLC/MS, and GC/MS to analyze three tropical fruits. Ensure the accuracy of the research results and have wider scientific and practical applicability. Therefore, the content of the article is richer and more convincing.
Comments for author File: 
Comments.pdf
Author Response
Reviewer 1
The authors analyzed the different glucose contents in three tropical fruits by confocal Raman spectroscopy combined with the partial least squares method. And discussed the effects of various pretreatment methods on the model's accuracy. It has certain scientific research value.
Response: Thank you for the comment. In addition, according to their report, we have improved the introduction with sufficient and include all relevant references [L. 45, 85], and we have improved the study design and methodology developed (see section 2).
It is recommended that the author increase the quantity of three tropical fruits and use more analytical techniques, such as HPLC, HPLC/MS, and GC/MS to analyze three tropical fruits. Ensure the accuracy of the research results and have wider scientific and practical applicability. Therefore, the content of the article is richer and more convincing.
Response: Thank you for the suggestions. We clarified the sentence refering to the quantity of the fruit, very sorry for the confusion, please see in the methodology [L. 111-114], we added the reference.
Currently, it is not the season for the production of tropical fruits in our region (affected by extended periods of drought), however, we will consider your suggestion for further experiments.
In addition, we have an HPLC, but it does not have an IR detector for sugars analysis, and we do not have GC. However, next year we will start an HPLC with IR detector (for sugars), which will help us to continue the study of sugars in fruits. Although the study focuses only on the Raman spectroscopy technique, your suggestion serves as a basis for future studies such as validation, efficacy, etc. to compare the technique used with chemical analytical methods used. Thank you for your comment.
However, in response to your suggestions, we have added information for greater reliability on the novelty in the use of the Raman spectroscopy technique that is comparable to conventional laboratory techniques (introduction); we also added references that justify its use, the amount of sample (see Section 2) and other aspects that enrich the manuscript (Results and discussion, and conclusion), and an adjustment was made to the title of the research.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe study aimed to evaluate the applicability of Raman confocal spectroscopy combined with PLS-DA to differentiate three tropical fruits. After post-review, I can state that the study has merit and scientific quality, addressing the elements directly and concisely, with consistent and well-presented results. Some basic suggestions were made.
In the summary, in lines 21 and 22, do the results refer only to glucose? And for the other sugars evaluated? What was the range?
In the research objective, the region where the study was conducted, northeastern Peru (Amazonas region), is this really necessary? Because the location can be described only in the methodology.
In the results, insert results and discussion. Because it was done jointly.
In table 3, highlight the best results in bold as well, similar to what was done in table 2.
Author Response
Reviewer 2
The study aimed to evaluate the applicability of Raman confocal spectroscopy combined with PLS-DA to differentiate three tropical fruits. After post-review, I can state that the study has merit and scientific quality, addressing the elements directly and concisely, with consistent and well-presented results. Some basic suggestions were made.
Response: Thank you for your comments. We have taken your suggestions into consideration.
In the summary, in lines 21 and 22, do the results refer only to glucose? And for the other sugars evaluated? What was the range?
Response: Thank you for the suggestion, we added more information, including the range and type of sugar [L. 22-24].
In the research objective, the region where the study was conducted, northeastern Peru (Amazonas region), is this really necessary? Because the location can be described only in the methodology.
Response: Thank for the comment, we removed the location [L. 2-3], and added the location in subsection 2.2 [L. 91-93].
In the results, insert results and discussion. Because it was done jointly.
Response: Sorry for the mistake, we joined them [L. 133].
In table 3, highlight the best results in bold as well, similar to what was done in table 2.
Response: Thank you for the suggestion. We highlighted the best results (see Table 3).
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsRaman confocal spectroscopy combined with the PLS-DA discriminant analysis model was used for the classification study of three tropical fruits. The effect of preprocessing methods on model performance was evaluated. We compared the performance of the unsupervised PCA algorithm and the supervised PLS-DA algorithm for three types of fruit classification. The comments on this manuscript are as follows:
1. In the introduction, the research of Raman spectroscopy technology in the field of food analysis should be further reviewed from the perspective of research objects and data analysis methods.
2.Section 2.1 should include further clear descriptions of the quantity, source and preparation of samples.
3.Why is the instrument resolution set to 3 cm-1 for Raman spectroscopy detection? More accurate resolution settings can provide more complete spectral information of the sample.
4.In Figure 1, further clarification is required regarding the analysis of the characteristic spectral peaks of the sample.
5.How was the sample data set partitioned prior to model building in section 3.2? How was the RMSECV obtained? The above needs to be further explained in the manuscript.
6.The conclusion section of the manuscript needs to be reorganised and rewritten, and the necessary work perspectives need to be added.
7.The quality of the figures in the manuscript is variable and needs to be further improved.
Comments on the Quality of English LanguageMinor editing of English language required.
Author Response
Reviewer 3
Raman confocal spectroscopy combined with the PLS-DA discriminant analysis model was used for the classification study of three tropical fruits. The effect of preprocessing methods on model performance was evaluated. We compared the performance of the unsupervised PCA algorithm and the supervised PLS-DA algorithm for three types of fruit classification.
Response: Thank you for your comments. We have taken your suggestions into consideration. In addition, according to their report, we have improved the introduction with sufficient and include all relevant references [L. 45, 85], and we have improved the study design and methodology developed (see section 2), same with results, discussions and conclusions (changes made are in red).
The comments on this manuscript are as follows:
In the introduction, the research of Raman spectroscopy technology in the field of food analysis should be further reviewed from the perspective of research objects and data analysis methods.
Response: Thank for the comment, we revised more information and added them [L. 45-85].
Section 2.1 should include further clear descriptions of the quantity, source and preparation of samples.
Response: Thank you for the suggestion. Quantity, source and preparation of samples were added [L. 90-99].
Why is the instrument resolution set to 3 cm-1 for Raman spectroscopy detection? More accurate resolution settings can provide more complete spectral information of the sample.
Response: Thank for the comment, we followed a previous report [L. 110-111].
In Figure 1, further clarification is required regarding the analysis of the characteristic spectral peaks of the sample.
Response: Thank you for the suggestion, the required clarification regarding the analysis of the characteristic spectral peaks of the sample was added [see Figure 1].
How was the sample data set partitioned prior to model building in section 3.2? How was the RMSECV obtained? The above needs to be further explained in the manuscript.
Response: Thank for the comment, we added information explaining the data set and the RMSECV [L. 116-121, 185-194].
The conclusion section of the manuscript needs to be reorganised and rewritten, and the necessary work perspectives need to be added.
Response: Thank you, we rewrote the conclusions [L. 258-271].
The quality of the figures in the manuscript is variable and needs to be further improved.
Response: Thank you for the suggestion, the figures quality was improved (see figures).
Comments on the Quality of English Language
Response: Thank you, the text was improved (main text).
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe necessary revisions have been implemented in the current version of the manuscript.
Author Response
Thank you for the suggestion. We also recommended the employment of more analytical methods in the discussion (L. 156-161) and conclusions (L. 268-269), using the suggested reference (L. 158-161).
Author Response File: Author Response.pdf
