Differences in the Behavior of Anthocyanin Coloration in Wines Made from Vitis vinifera and Non-vinifera Grapes

Round 1

Reviewer 1 Report

The proposed manuscript investigates individual anthocyanin forms in Vitis vinifera and non-Vitis grapes and wines, as well as their changes in relation to pH changes and aging process. It is emphasized that non-Vitis varieties contain higher concentrations of 3,5-diglucosyl anthocyanins, in comparison to Vitis varieties, where predominant anthocyanins are 3-glucosyl anthocyanins. Nevertheless, prior to accepting for publishing, some changes needs to be addressed, as stated below.

L8 I L15 - Non should be written with lowercase letters (non-Vitis)

L38-50 – the pyranoanthocyanins should be also stated here, since these forms are important for wine color

L110-111 – full names should be written for MBA and CS

L95 – you only detected anthocyanins? Without quantification?

Why didn’t you measure total anthocyanins content (mg/g and mg/L), as well?

Author Response

Thank you for your careful review. The responses to your comments are listed below.

L8 I L15 - Non should be written with lowercase letters (non-Vitis)

[A] “N” was changed to “n” (L8).

L38-50 – the pyranoanthocyanins should be also stated here, since these forms are important for wine color

[A] “pyranoanthocyanins” were added here (L40-41).

L110-111 – full names should be written for MBA and CS

[A] Full name of MBA and CS were added (L128-130).

L95 – you only detected anthocyanins? Without quantification?

Why didn’t you measure total anthocyanins content (mg/g and mg/L), as well?

[A] More than 95% of the peak area was attributed to anthocyanins detected at 280 nm, as described in L169. This suggests that the extract is primarily composed of anthocyanins. Regarding MER, although the main peak was malvidin-3-G (Fig. 1), each anthocyanin has a different molecular coefficient. Additionally, the environmental elution conditions (pH, acetonitrile %) for each peak may vary in HPLC. Therefore, we utilized spectrophotometric methods for the quantification of anthocyanins, as outlined by Yokotsuka (L118), employing malvidin-3G equivalent for V. vinifera and malvidin-3,5-diglucoside equivalent for YS.

Again, thank you for giving us the opportunity to strengthen our manuscript with your valuable comments and queries. We have worked hard to incorporate your feedback and hope that these revisions persuade you to accept our submission.

Reviewer 2 Report

The manuscript, "Differences in the Behavior of Anthocyanin Coloration in Wines Made from Vitis vinifera and Non-vinifera Grapes," gives an overview of anthocyanin behavior in vinifera and non-vinifera (YS) wines and anthocyanins based on the well-known effect of pH value on anthocyanins, especially 3,5 glucosides, and based on the color attributes of commercial wines. The novelty and significance of the content are limited. 

Several aspects in the manuscript must be addressed before the manuscript can be considered acceptable for publication: 

The research's aim must be more precise: the phrase "to uncover the essential properties for producing high-quality red wines containing 35DG" is not suitable for a scientific paper.  

M&M:

2.2. Extraction and partial purification of grape skin anthocyanins

The extraction protocol must be clarified, as well as additional details. Describe precisely the sample preparation (fresh or dried skins, how they were separated from berries, drying or no drying...), why methanol was not used in the first step of extraction, and why different approaches were used for MER vs. YS. Please add all missing information needed for the experiment to be reproducible. Comparing anthocyanins of two varieties is problematic if there are differences in the extraction protocols. 

MBA wines? The full name of this variety and its pedigree are not defined.

Commercial wines used in the research

Results: 

Figure 1 - scales are not identical for the two chromatograms and should be uniform. 

The chemical composition of commercial wines must be presented. 

Conclusions: 

The conclusion, "Our findings suggest that wines containing large amounts of 35DG have high CA% and show resistance to aging," must be modified and limited to the research results, i.e., the cultivar used in this research. 

Author Response

Thank you for your kind and careful review. The responses to your comments are listed below.

The research's aim must be more precise: the phrase "to uncover the essential properties for producing high-quality red wines containing 35DG" is not suitable for a scientific paper.  

 [A] This sentence was revised (L73-75)

M&M:

2.2. Extraction and partial purification of grape skin anthocyanins

The extraction protocol must be clarified, as well as additional details. Describe precisely the sample preparation (fresh or dried skins, how they were separated from berries, drying or no drying...), why methanol was not used in the first step of extraction, and why different approaches were used for MER vs. YS. Please add all missing information needed for the experiment to be reproducible. Comparing anthocyanins of two varieties is problematic if there are differences in the extraction protocols. 

[A] In this experiment, we aimed to selectively extract anthocyanins while excluding other phenolics (cofactors) and tannins. Acidified water proved to be an effective solvent overall, resulting in lower yields of tannins with minimal sacrifice in anthocyanin yield.

https://doi.org/10.1111/j.1750-3841.2007.00441.x

We had to modify the procedure for the partial purification of anthocyanins between the two cultivars, as anthocyanins in YS are more hydrophilic due to their structure with two glucose attachments. Additional details of the extraction protocols were included in the manuscript (L86-113).

MBA wines? The full name of this variety and its pedigree are not defined.

[A] Full name and pedigree was indicated in the text (L128-129).

Commercial wines used in the research. The chemical composition of commercial wines must be presented. 

[A] We did not measure the chemical composition of the sample wines (ethanol, organic acids, etc.) since only anthocyanins are of interest in these experiments. Our objective was to ascertain the authentic color profile of commercial wines. pH plays a crucial role in color measurement. Hence, in the commercial wine experiments, we meticulously adjusted the pH to 3.6. The samples utilized were commercially available wines submitted for competition, and considered they exhibited no significant differences in chemical composition. Therefore, the influence of other factors is thought to be minimal in the data related to copigmentation.

Results: 

Figure 1 - scales are not identical for the two chromatograms and should be uniform. 

 [A] Fig. 1 was replaced with the same scale data.

Conclusions: 

The conclusion, "Our findings suggest that wines containing large amounts of 35DG have high CA% and show resistance to aging," must be modified and limited to the research results, i.e., the cultivar used in this research. 

[A] This sentence was revised (L361-363).

Again, thank you for giving us the opportunity to strengthen our manuscript with your valuable comments and queries. We have worked hard to incorporate your feedback and hope that these revisions persuade you to accept our submission.

Round 2

Reviewer 2 Report

The authors have revised the manuscript according to suggestions. In this form, I consider the manuscript is acceptable for publication in Fermentation.