The Effect of Non-Saccharomyces Cerevisiae Torulaspora delbrueckii on the Aroma Composition of Munage Grape Base-Wine and the Mechanism of the Effect
, Bingze Liu 1,†, Ruxianguli Maimaitiyiming 1, Liang Wang 1, Lei Zhao 1, Huimin Zhang 1, Keping Chen 2 and Aihemaitijiang Aihaiti 1,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsComments for author File: 
Comments.pdf
Author Response
1)Minor revision
In the title, write cerevisiae with a small initial letter
In line 18, write Saccharomyces in italics
In line 53, write non-Saccharomyces in italics
Line 55 Saccharomyces in italics
In line 59, write non-Saccharomyces in italics
On lines 63 and 65, write the name of the Sauvignon variety correctly
In line 69, write Saccharomyces in italics
Enter the model of the alcoholometer in line 128
In line 241 p-polyloxyacetate, write p- in italics
Line 288 non-Saccharomyces
Line 289 Saccharomyces in italics
Line 294 non-Saccharomyces
Line 296 Saccharomyces in italics
Line 298 delbrueckii d- lower case
Line 299 bacterium?
Line 303 and 310 Saccharomyces in italics
Line 347 [33] insert the exponent
Line 412 bacteria? These are yeasts
Line 430 Münag?
Line 435 β- write in italics
A: Thank you for your suggestions, and we apologize for so many cheap mistakes in the writing of the manuscript. These have been corrected and highlighted in red in the manuscript. Thank you again for your revised suggestion.
2)Why was Torlaspora chosen? Write something more about its characteristics in the introduction.
A: Thank you for your advice. The reason why we chose this yeast to carry out this study is because our laboratory has carried out the research related to strain screening in the early stage, and this yeast has shown strong substrate adaptability, the fastest fermentation speed, strong acid production ability, strong aroma production ability among the 11 strains of endophytes of grapes, and what's more important is that this yeast has a more prominent function of lowering the alcohol at the same time while possessing the same fermentation speed.
Of course, the excellent characteristics of this yeast is also one of the important reasons why we choose to use it. We apologize for the lack of this section in the introduction, so we have added the following to the introduction to supplement the excellent characteristics of this yeast at lines 84-107 highlighted in red:
“Its cells are small, subcircular (6.5 μm × 5.5 μm). and the colonies on WLN culture medium are cream-colored with a faint greenish tinge, spherical protrusions, and smooth and opaque.”
“Its main feature is that it can slowly ferment a large amount of sugar, with an alcohol production capacity of 8% to 14%, and its fermentation products contain less acetic acid, ethyl acetate and acetaldehyde.”
“TD can affect the aroma of wine by affecting some chemical groups (e.g. increase in 2-phenylethanol). It also affects the production of volatile lipid substances, such as a decrease in isoamyl acetate C6-C10 fatty acid content. It has been shown that the odor activity of lipid fatty acids is high in wines fermented with a mixture of TD and Saccharomyces cerevisiae, and that TD can affect the aroma of wines by influencing carbonyl compounds.”
“TD was isolated from high-sugar grape musts and was found to be hyperosmotic-tolerant, and TD remained characterized by high glycerol production and low volatile acid production relative to Saccharomyces cerevisiae. Therefore, TD can be a potential strain for reducing volatile acids in wine fermentation, and the mixed fermentation of TD and Saccharomyces cerevisiae produces dry white wines and sweet wines with outstanding quality.”
Thank you again for your advice.
3)In subsection 2.2. The Making of MGBW there is a lack of information on the phytosanitary status of the grapes, the amount of sugar and the titratable acidity as well as the pH value before correction by adding citric acid in the further experiment. The amount of residual sugar (glucose + fructose in the wine) is missing. Is it a dry wine?
A: thank you for your advice. We apologize for this lack of representationand have added and amended the following to line 120-123 highlighted in red: “Munage grapes (Vitis vinifera L. cv. Munage) were harvested from vineyards in Atushi City, Kizilsu-Kirghiz Autonomous Prefecture, Xinjiang, China, and had a fruit sugar content (as glucose) of 305.263 g/L, an acidity content (as tartaric acid) of 3.274 g/L, and a pH value of 4.64.”
With a residual sugar content of 5.80 g/L, MGBW is a semi-dry white wine by residual sugar content.
Thank you again for your advice.
4)Why was sulfur dioxide not used? It has a microbicidal effect on bacteria of the genus Lactobacillus, which can be resistant at these temperatures and are also participate in the formation of some aromas.
A:Thank you for your advice. As you said, we have also considered the question of whether to add sulfur dioxide.
MGBW is a base wine, and we have optimized the process in the early stage so that it has the characteristics of low alcohol and high aromatic active ingredients, so that it can be blended with a variety of fruit and vegetable concentrates to produce low-alcohol blended alcoholic beverages.
Considering that the fermentation cycle of MGBW is relatively short, 96 h, sulfur dioxide is a gas with irritating odor that may interfere with the results of headspace solid-phase microextraction in the study, and too little sulfur dioxide may not be able to perform its functions of sterilization, color protection, antioxidant, etc., we chose pasteurization to kill the microorganisms in the substrate.
Moreover, the process of pasteurization also promotes the release of phenolics from grape skins and seeds to a certain extent, also considering this possible positive effect and the residual problem of sulfur dioxide, we finally did not choose to add sulfur dioxide in the preparation of MGBW, thank you again for your advice.
5)Chapter 3.1. I think the pH value 4.11±0.008 is high. Why is the pH adjusted to this value? Why was citric acid used instead of tartaric acid?
A: Thank you for your advice. In our preliminary work, we examined the optimal initial pH for fermentation of MGBW, which ranged from pH = 2 to 7, and finally determined the optimal pH to be 3.61. In the production of MGBW, the pH of the fermentation substrate was 4.64, and we adjusted the pH to 3.61 to start the fermentation, and after 96h of fermentation, we measured the pH of the MGBW to be 4.11, which we think is more convenient for our subsequent use of fruits and vegetables. pH is more convenient for our subsequent compounding of MGBW using fruit and vegetable juice concentrates.
The reason we chose to use citric acid for pH adjustment is that we chose to calculate tartaric acid equivalents in the method of determining the total acid content in this study, so we chose citric acid, which can participate in the main metabolism of microorganisms.
Thank you again for your advice.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript titled "the effect of non-saccharomyces cerevisiae Torulaspora Delbrueckii on the aroma composition of Munage Grape Base-wine and the mechanism of the effect" provides a good approach for the aroma analysis in mixed fermentation.
However, the study requires some revision of the following issues:
Why did the authors choose 96h fermentation time?
Why did the authors choose this grape variety? Is it often used for the production of wine in their region?
What cell numbers did the authors use for inoculation? Did they check it?CFU?
What about sensory analysis?
The authors should give an explanation why the concentrations decrease and increase over the time (Fig. 3c)
The authors should add: Figure 3b and c : which variant? mixed fermentation?
The authors should add 3a; what time point? 96h?
l.299 and 412 it is yeast and not bacteria
L.65 sauvignan blanc with c in the end not d
Author Response
1)Why did the authors choose 96h fermentation time?
A: Thank you for your advice. Regarding the fermentation time of MGBW, it was obtained through the process optimization study conducted in our laboratory in the previous stage. In the process optimization study, we used the number of types of aroma components as an indicator, and the highest number of types of aroma components was detected at 96h of fermentation, so 96h was directly used as the fermentation time of MGBW in this study. Thank you again for your advice.
2)Why did the authors choose this grape variety? Is it often used for the production of wine in their region?
A: Thank you for your advice. The reason why we chose the Munag grape as the raw material for this study is because we want to solve the problem of overcapacity of this grape variety by developing a low alcohol wine product. Our laboratory has found that this variety of grape is often stocked in cold storage at the end of the following year due to its winter production period. We believe that this is due to the lack of further processing products for this variety of grapes, which is why it was chosen for this study. We are also actively working with local food companies on the mass production of MGBW and the subsequent blending of lower-alcohol products. Thank you again for your advice.
3)What cell numbers did the authors use for inoculation? Did they check it?CFU?
A: Thank you for your comment. We apologize for this confusion. Therefore, we have modified accordingly: “108 CFU/mL”at line 138-139 highlighted in red. Thank you again for your advice.
4)What about sensory analysis?
A: Thank you for your advice. For wines sensory analysis is indeed one of the most important indicators that cannot be ignored. However, as MGBW is a base wine for low-alcohol flavored beverages, it will be compounded, blended and mixed in the subsequent production process to produce a variety of low-alcohol flavored beverages with different tastes. Therefore, we plan to conduct a more in-depth study on the sensory analysis of MGBW using gas chromatography and electronic nose. Thank you again for your advice.
5)The authors should give an explanation why the concentrations decrease and increase over the time (Fig. 3c)
A: Thank you for your advice. We added the following to line 289-296 highlighted in red: “The trends of rOAV and relative content of these 27 key aroma components with the most significant content changes after mixed fermentation were consistent, and we hypothesize that this trend of these 27 key aroma components, in the case of esters, may be due to the involvement of TD in up-regulating the level of fatty acid metabolism in the fermentation system. From this, we can also speculate that the time for one cycle of complete fatty acid metabolism in MGBW during fermentation may be 48 h. This also provides a new idea for us to further explore the effect of TD on the aroma formation of MGBW.”
Thank you again for your advice.
6)The authors should add: Figure 3b and c : which variant? mixed fermentation?
A: Thank you for your advice. We have made the following changes to line 298-299 highlighted in red: “the changes in the relative content of 27 key aroma components over time during mixed-fermentation;”
Thank you again for your advice.
7)The authors should add 3a; what time point? 96h?
A: Thank you for your suggestion and we apologize for the unclear presentation. We have made the following changes to line 297-298 highlighted in red: “the total relative odor activity value (rOAV) of MGBW that was mixed-fermented by EC1118 and TD for 96h, as well as MGBW that was single-fermented”.
Thank you again for your advice.
8)l.299 and 412 it is yeast and not bacteria
A: Thank you for your advice. We have amended it to “yeast” at line 331 and 448 highlighted in red.
Thank you again for your advice.
9)L.65 sauvignan blanc with c in the end not d
A: Thank you for your advice. We have amended it to “sauvignan blanc” at line 64 highlighted in red.
Thank you again for your advice.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAll suggestions have been adopted by the authors. I would like the article to be accepted in its entirety.
