Determination of Phenolic Compounds in Blue Corn Flour (Zea mays L.) Produced and/or Metabolized by Colletotrichum gloeosporioides in a Fermentation Process

Round 1

Reviewer 1 Report

Introduction

There are sentences which should include references (line 41-43).

The introduction should focus more on the importance of fermentation process on the increase of nutritional or functional value of corn.

Section 2.4. (Phenolic compounds extraction: initial and during the fermentation process) should be improved the redaction. Why were different extraction conditions used?

Salinas-Moreno 's extraction conditions should be described.

Cyanidin 3-glucoside is the major pigment in blue corn. If this pigment had been degraded, as the authors indicate, the corresponding degradation compound of this anthocyanin, phenolic acid, should have been observed.

The used nomenclature of the samples is confused. Table 1 should be indicated which is control sample.

The discussion should be re-writeen, since is focused on biological activity studies and the objetive of this article is not that.

In vitro antioxidant activity assays could have been carried out.

Author Response

Dear Reviewer 1. 

First, I want to thank you for the suggestions made for my manuscript. All suggestions were analyzed and accepted. I send you the list of corrections made to the document. The corrections made are indicated by color in the manuscript

Observations

There are sentences which should include references (line 41-43).

it was already modified.

The introduction should focus more on the importance of fermentation process on the increase of nutritional or functional value of corn.

it was already corrected Line 50-58. Here it was spoken about how the phenolic compounds can be potentiated by a fermentation process and the principal features of it.

Section 2.4. (Phenolic compounds extraction: initial and during the fermentation process) should be improved the redaction. Why were different extraction conditions used?

Salinas-Moreno 's extraction conditions should be described.

it was already corrected line 121.

Cyanidin 3-glucoside is the major pigment in blue corn. If this pigment had been degraded, as the authors indicate, the corresponding degradation compound of this anthocyanin, phenolic acid, should have been observed.

it was already modified lines 190-192 and complemented lines 202-205.

The used nomenclature of the samples is confused. Table 1 should be indicated which is control sample.

it was already modified lines 90-102. The control showed in this study were used exclusively in the fermentation process to confirmed the axenic presence of C. gloeosporioides

The discussion should be re-writeen, since is focused on biological activity studies and the objetive of this article is not that.

it was already modified lines 366-369.

In vitro antioxidant activity assays could have been carried out.

It is a really good observation, however then in of this study only determines the phenolic compounds in a fermentation process.   

Best Regards,

Dr. Leon Hernandez

Reviewer 2 Report

Manuscript fermentation-1615146

Title:  Determination of Phenolic Compounds in Blue Corn Flour (Zea 2 mays L.) Produced And/Or Metabolized by Colletotrichum 3 gloeosporioides in a Fermentation Process

 Authors: Villarreal-Rodríguez et al.

General comments to the editor and authors

In this manuscript the authors study the effect of fermentation with Colletotrichum gloeosporipoides on phenolics in blue corn flour. In my opinion, the objective of the work is very interesting since the intake of foods enriched in phenolics have been widely relate with improvement in human health. Also, the manuscript is well focussed and the experiments well conducted. It is well written in such a way that it is easy for the reader to follow and the literature is quite recent.

Therefore, in my opinion, the manuscript should be published after minor revision. Just a few changes should be made before publication.

1. Pg 5, lines 186-187 “In the initial extraction of blue corn flour, without fermenting, it was not obtained any HPLC peak that corresponded to CYA, which could have happened because there was an anthocyanins degradation during the extraction”.

I don´t agree with this statement. It is really surprising that CYA was not detected in blue corn flour before fermentation, particularly when PEL was. The extraction method used by the authors should not trigger the degradation of CYA. Considering that MS was not used in the identification, it is possible the retention time of CYA has been mistaken in the identification. Since this is an important result of the manuscript, I suggest verifying the absence of CYA in raw flour.

2. In “Results and Discussion” section there are some paragraphs which would be more appropriate for Introduction. For example:

-lines 182-186; 205-216; 224-234; 239-243.

All these paragraphs mention information described in the literatures. They are not “results” of this study. I suggest moving to Introduction, removing or, at least, shorten a lot.

3. Data in tables should be expressed as w/w, not w/v. I mean mg kg^-1 sample (or extract) instead of mg l^-1.

4. Conlcusions (lines 346-359). This section should not be a summary of the whole study (like the Abstract). Please, amend it in such a way that it does not repeat information already commented.

5. Although the manuscript is well written there are a few spelling mistakes that should be corrected. For instance: line 244 “flour blue corn”, line 354 “CA is also not part….” Please revise English.

Author Response

Dear Reviewer 2 

First, I want to thank you for the suggestions made from my manuscript. All suggestions were analyzed and accepted. I send you the list of corrections made to the document. The corrections made are indicated by color in the manuscript

Observations

1. Pg 5, lines 186-187 “In the initial extraction of blue corn flour, without fermenting, it was not obtained any HPLC peak that corresponded to CYA, which could have happened because there was an anthocyanins degradation during the extraction”.

I don´t agree with this statement. It is really surprising that CYA was not detected in blue corn flour before fermentation, particularly when PEL was. The extraction method used by the authors should not trigger the degradation of CYA. Considering that MS was not used in the identification, it is possible the retention time of CYA has been mistaken in the identification. Since this is an important result of the manuscript, I suggest verifying the absence of CYA in raw flour.

The observation is very interesting and allowed us to realize the conditions of sample preparation, storage, and conservation of the samples (light, storage containers, quality of solvents used, etc.) before being analyzed by HPLC. It is also important to mention that standards of the majority components identified in the bibliography were used in the study.

2. In “Results and Discussion” section there are some paragraphs which would be more appropriate for Introduction. For example:

-lines 182-186; 205-216; 224-234; 239-243.

it was already corrected

All these paragraphs mention information described in the literatures. They are not “results” of this study. I suggest moving to Introduction, removing or, at least, shorten a lot.

3. Data in tables should be expressed as w/w, not w/v. I mean mg kg^-1sample (or extract) instead of mg l^-1.

it was already corrected.

4. Conlcusions (lines 346-359). This section should not be a summary of the whole study (like the Abstract). Please, amend it in such a way that it does not repeat information already commented.

it was already corrected

5. Although the manuscript is well written there are a few spelling mistakes that should be corrected. For instance: line 244 “flour blue corn”, line 354 “CA is also not part….” Please revise English 

it was already corrected

Best regards,

Dr. Leon Hernandez

Reviewer 3 Report

After a careful reading, I could notice that the authors followed the reviewer’s comments and improved the paper. The paper is now ready to be published.
Excellent work!

Reviewer 4 Report

Specific points

In general, this study can make a significant contribution to food processing. However, the conclusion of this study should be much more clearly defined.

L:108: „Phenolic compounds content, was performed as described by De Wanto et al. [15]…”

“De Wanto et al.” - should be corrected in - Dewanto et al. Please, correct this in the whole text.

L:135: “Data were expressed as the mean ± standard deviation of three experiments…”  - no standard deviations are given (for example, see Table 1).

Table 1: In my opinion, below the table, the explanations of abbreviations (CYA, PEL, CA, QRC, CLA and 20A, 20B……30F) listed in the table should be given.

4. Conclusions: In fact, no conclusions, it is not clear which fermentation conditions give the best results. I think that is exactly what should be pointed out in the conclusion. In my opinion, the conclusion written in this way actually looks like an Abstract. I think that the conclusion of this research should be rewritten.

________________

All my suggestions are for improving the manuscript. I hope all the suggestions are clear.

Best regards

Round 2

Reviewer 1 Report

The identification of phenolic compounds carried out in this study is poor.  The objetive should be changed since no biological studies have been carried out in this study.