Discrimination of Cheese Products Regarding Milk Species’ Origin Using FTIR, 1H-NMR, and Chemometrics
Fátima De Cássia Oliveira Gomes
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsWhile the document is well-written, I believe there are certain shortcomings in the quality of the research and the manuscript's relevance to readers.
One notable absence is the lack of any mention of industrial or practical applications. It is crucial for the research to serve a specific purpose, such as being applicable as a tool against counterfeiting or adulteration.
Throughout the document, a clear and compelling rationale for conducting this research is absent, beyond utilizing robust techniques to characterize cheese. Furthermore, it is unclear why statistical methods are applied to compare cheeses with evident variations in raw materials and manufacturing processes.
A more logical approach, in my opinion, would be to compare cheeses using chemometrics, focusing, for example, on cheese from different geographical origins. The validity of comparing milk obtained from different animals is questioned; wouldn't there be a logical difference based on the natural variation in composition? Is it truly necessary to employ robust and expensive methods like H-NMR and FTIR, in addition to multivariate statistics, to determine if a sheep-based cheese differs from a cow-based cheese? Could this not be akin to comparing distinct fruit juices (e.g., apple with banana or orange with apricot)?
I propose that the manuscript undergoes a revision and be submitted as a new one. This revision should include the incorporation of a practical application for the research and a modification of the statistical analysis, as suggested by the authors themselves, to compare the same type of cheese from different geographical origins, for example.
Comments on the Quality of English Language
No major problems related to language.
Author Response
Thank you very much for your valuable comments. Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsTarapoulouzi et al. report on a chemometric analysis of 49 European cheese samples made of cow, goat and/or sheep milk. FTIR and 1H-NMR have been applied as experimental methods in OPLS-DA discriminant analysis, getting an acceptable discrimination between cheese from cow milk and cheeses form goat and sheep milk. The goal of the study is clear but the context is not up-to-date from my viewpoint, and the relevance and reliability of the outcomes is quite poor. Therefore, to deserve publication in Applied Sciences, I recommend the authors address the following points:
1. The introduction should be substantially reconsidered:
a. Improper definitions are given (e.g. “Nuclear Magnetic Resonance (NMR) measures hydrogen nuclei to analyze the chemical structure…”)
b. The description of 1H NRM and FTIR spectra of milk is didactic but could be probably reduced
c. A comparison with the existing literature in terms of chemometric approaches to discriminate milks from different origin is missing.
2. Data given on cheese samples should be carefully revised. To the best of my knowledge Grana Padano is from cow milk, not sheep and goat. Hence, they are outliers in the OPLS-DA in my understanding.
3. Experimental details (relaxation delay, number of points, processing parameters…) used for 1H NMR spectra should be given
4. Enlargements of the 1H NMR spectrum (Fig 1) have to be provided, with clear assignment of the known peaks.
5. Details on NMR and FTIR spectra processing (e.g. normalization, binning) before statistical analysis should be given.
6. The discussion of the OPLS-DA findings should be extended. What about the discrimination between cheeses only from goat milk and only from sheep milk? Is there any information from the loading plot? Could you identify the metabolite(s) or at least a narrow spectral region responsible for the discrimination?
Comments on the Quality of English Languageoverall fine
Author Response
Thank you very much for your valuable comments. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsI consider that the present work is an extension of other Works presented by the authors:
Tarapoulouzi, M., Kokkinofta, R. and Theocharis, C.R., 2020. Chemometric analysis combined with FTIR spectroscopy of milk and Halloumi cheese samples according to species’ origin. Food science & nutrition, 8(7), pp.3262-3273.
Tarapoulouzi, M. and Theocharis, C.R., 2022. Discrimination of Cheddar, Kefalotyri, and Halloumi cheese samples by the chemometric analysis of Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectra. Journal of Food Process Engineering, 45(7), e13933
Tarapoulouzi, M. and Theocharis, C.R., 2019. Discrimination of Cheddar and Kefalotyri cheese samples: Analysis by chemometrics of proton-NMR and FTIR spectra. J. Agric. Sci. Technol, 9, pp.347-355.
The authors of this study analyzed various types of cheese using two established techniques that are valuable for food science. By providing significant information on food composition, these techniques are an effective tool for enriching the field. However, the methodology employed for data analysis is not particularly innovative, as it has been used in previous studies. Therefore, the authors should emphasize what distinguishes this particular work from others and what new contributions it offers.
Some observations
Introduction:
· Line spacing should be the same in all paragraphs
· How does this work differ from others presented and what is innovative about it?
Materials and methods:
· The information about the cheeses is repeated in both the text and Table 1. Therefore, please remove the redundant information from the text and instead mention that the description of the samples can be found in Table 1.
· For the FTIR and freeze dryer, please specify the country in which they were used.
· Also, please explain what the acronyms OPLS-DA and AUC stand for?
Results and discussion
· Could you provide more specific information about the composition of the cheeses based on the figures as there is no discussion of the results presented? It would be helpful if you could outline the differences in composition between the samples.
· Additionally, it would be useful if you could provide information on how the FTIR results compare to those of other authors.
· Finally, please explain the meaning of strong and medium absorption?
Conclusion
It should be more specific regarding the findings found
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Thank you very much for your valuable comments. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe manuscript "Discrimination of cheese products regarding milk species' origin using FTIR, 1H-NMR and chemometrics" presents a proposal for discriminating European cheese samples of various origins using different analysis techniques. Below are my considerations.
- Objectives (lines 99-103) does not describe the actual novel contribution of the research.
- In figure 1, the spectrum is not legible and the peaks need to be identified. I suggest putting in another figure that is relevant to showing significant differences between the cheese samples.
- Line 285: Describe in more detail the results of the work carried out by Tarapoulouzi and Theocharis, emphasizing the contributions of the present work in relation to the work mentioned.
- In the conclusions, the cheeses produced from goat's and sheep's milk were not differentiated by the techniques used. Clarify whether the techniques used were appropriate to the proposal. In addition, the differences between production methods and geographical origin were not satisfactorily discussed.
Author Response
Thank you very much for your valuable comments. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 5 Report
Comments and Suggestions for Authors-Lines 16-17, substitute sentence for: "The samples of this study will be enriched for further testing with spectroscopic techniques and chemometrics."
-Table 1, Tables should only have three horizontal lines.
-Line 156, delete "goodness of".
-Lines 188-190, reference these arguments.
-Figure 2, remove the outer line.
-Figure 3, b) avoid overlapping of some values at the bottom. Also, if possible, increase the size of the Figure to achieve a better view of the data.
-Line 252, "as also happens in previous studies", writing should be impersonal.
-Table 2, all Tables should have the same format throughout the whole document. Tables 1 and 2 do not have the same format.
-Lines 259-262, 287-289, 290-291, 316-319, rewrite these sentences for better understanding.
-Figure 4, the x-axis should range from 0 to 100%. Also, consider increasing the size and remove the software version, date, and time from the bottom-right corner of the Figure.
-Figure 5, consider increasing the size and remove the software version, date, and time from the bottom-right corner of the Figure.
Comments on the Quality of English Language
Some sentences are poorly written and must be improved for better understanding.
Author Response
Thank you very much for your valuable comments. Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAuthors have made some improvements in the document.
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Thank you very much.
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have partially answered my comments and remarks. I believe that the manuscript has been improved and deserves publication in Applied Science, once the authors have addressed the following points:
- The details added on NMR and FTIR spectra processing before statistical analysis are not sufficient from my point of view. How about bin size? Was the water peak in the NMR spectra excluded? Please carefully revise this point.
- If I can understand that many questions are still open and will be addressed in following studies, I find anyway crucial to discuss more the OPLS-DA findings of the present manuscript to be of some relevance to the readers. What about the loading plot? Which metabolite(s) or spectral region(s) are more relevant for the discrimination of the two clusters? At lines 216-218, you mention that “In addition, it was observed (AND CONFIRMED BY CHEMOMETRICS) that proline (d), methionine (e), citric acid (f), and formic acid (g) at 2.00, 2.23, 2.80, and 8.40 ppm respectively, are different in cow’s and goat’s & sheep’s cheese.” This finding (and similar observations) have to be discussed from the viewpoint of the statistical analysis.
Comments on the Quality of English Languageoverall fine
Author Response
Thank you very much.
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have responded satisfactorily to all the comments submitted.
Observation:
The verb in the aim should be in the past.
Comments on the Quality of English LanguageThe english was improved
Author Response
Thank you very much.
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsAll comments and suggestions have been answered by the authors.
Author Response
Thank you very much.
Please see the attached file.
Author Response File: Author Response.pdf
