The Impact of Indigenous Non-Saccharomyces Yeasts Inoculated Fermentations on ‘Semillon’ Icewine

Round 1

Reviewer 1 Report

This is a review of the article ''The impact of indigenous non-Saccharomyces yeasts inoculated fermentations on ‘Semillon’ Icewine''. The paper is well written and can be improved if the issues below are addressed.

The reference numbering in the text needs to be revised. No [1] and [15] came before [2].

Line 42: What are the genus and species name of Semillon

Line 76: What are the strain names of Lachancea thermotolerans (LT) and Torulaspora delbrueckii used?

Line 104: How was the Semillon’ grape juice composition determined?

Line 173: It appears the result and discussion sections were combined. The subheading should read 'results and discussion'

Lines 186-188: Authors state 'This is beneficial because a long fermentation time and a slow fermentation rate favour the release of wine aroma compounds' How will this affect the turnover of the company? Does the benefit of aroma supercede the need to produce more for the market?

Line 447: Include the reference number after 'Benito et al.'

Conclusions

Authors summarised in the abstract that the emerging low acidity in icewine grapes is becoming a major problem in producing  quality icewine and that using the organisms proposed resulted in reduced volatile acids. However the pH of these in both single fermentation and sequential fermentation results shown (Table 1) are lower than that of SC indicating that they are more acidic. This should be discussed and the limitations pointed out.

Author Response

RESPONSE TO REVIEWER 1

Reviewer 1:

We thank you for giving us an opportunity to revise our manuscript. We appreciate your positive comments and suggestions on our manuscript entitled ''The impact of indigenous non-Saccharomyces yeasts inoculated fermentations on ‘Semillon’ Icewine'' (No. 1861871).

These comments are all valuable and very helpful in revising and improving our paper. The text of our responses is highlighted in red (changes based on your comments). The revised text is also shown in red in the revised manuscript.

Comment 1.

The reference numbering in the text needs to be revised. No [1] and [15] came before [2].

--Response 1: The reference numbering has been corrected

Comment 2.

Line 42: What are the genus and species name of Semillon

--Response 2: Please, we have replaced Semillon with Vitis. vinifera L.cv. Semillon.

Comment 3.

Line 76: What are the strain names of Lachancea thermotolerans (LT) and Torulaspora delbrueckii used?

--Response 3: The strain names are LT-2 and TD-3 for Lachancea thermotolerans (LT) and Torulaspora delbrueckii (TD), respectively. Please, this has now been mentioned in in the manuscript.

Comment 4.

Line 104: How was the Semillon’ grape juice composition determined?

--Response 4: These oenological parameters were determined based on the methods described by OIV-MA-AS313-01: R2015.

OIV-MA-AS313-01: R2015. Compendium of International Methods of Wine and Must Analysis. Chemical Analysis: Acids, Total Acidity (Oeno 551/2015). Paris: Organisation Internationale de la Vigne et du Vin.

Comment 5.

Line 173: It appears the result and discussion sections were combined. The subheading should read 'results and discussion'

--Response 5: Thank you. The subheading has been changed to “Results and Discussion”

Comment 6.

Lines 186-188: Authors state 'This is beneficial because a long fermentation time and a slow fermentation rate favour the release of wine aroma compounds' How will this affect the turnover of the company? Does the benefit of aroma supercede the need to produce more for the market?

--Response 6:

The fermentation of icewine itself is a slow process at low temperature. In icewine production, extending the fermentation time by about 10 days does not affect the production schedule. After the end of fermentation, icewine must be stored for a long time so that the wine acquires a better body, becomes more harmonious and balanced, and is clearer and more stable. After the alternation of heat and cold and a biological stability treatment, the icewine reaches a stable state. This process usually takes about 16 months. From this point of view, the extension of a certain fermentation period does not affect the production of the products, nor the delivery of the products to the customers. Moreover, extending the fermentation time at low temperature increases the biological stability of the final product to a certain extent. Since the yeast is active for a longer period of time at low temperatures, it is more likely to consume the nutrients available in the wine, and the lower amounts of these substances ultimately make the biological stability of the product more reliable. In terms of energy consumption, extending the fermentation period does not increase costs for the winery, since the grapes frozen on the vine are harvested and the wine is fermented in winter. The ambient temperature is now so low that heat exchange during fermentation no longer requires artificial refrigeration. If the temperature needs to be lowered, it is only necessary to regulate the temperature in the brewery, which can only be done by exchanging it with the outside temperature.

The increase of aromatic substances in icewine is a positive influence. Rich aromatic substances also improve the flavor of icewines, making them rounder, more complete and coordinated. An icewine with fragrance and elegance, especially with floral and fruity aromas, significantly increases the quality of the wine. An excellent wine that brings joy, happiness and satisfaction to any drinker.

Comment 7.

Line 447: Include the reference number after 'Benito et al.'

--Response 7: Please, the reference numbering has been corrected

 Comment 8.

Authors summarised in the abstract that the emerging low acidity in icewine grapes is becoming a major problem in producing quality icewine and that using the organisms proposed resulted in reduced volatile acids. However, the pH of these in both single fermentation and sequential fermentation results shown (Table 1) are lower than that of SC indicating that they are more acidic. This should be discussed and the limitations pointed out.

--Response 8: It was observed that acidification (increase in total acidity) by LT resulted in a decrease in pH close of 0.3-0.38 units (Table 1). This value was achieved by producing a maximum of 2-2.2 g/L of lactic acid. Winemakers believe that at a residual sugar level of 150-160 g/L, the total acidity should be regulated to about 9.0 g/L, which is suitable for a balanced taste of sugar and acidity. Thus, if the residual sugar content of ice wine is regulated to 150-160 g/L, fermentation with LT, L-D and L-S could be a suitable alternative to S. cerevisiae in producing icewine with lower pH and acceptable acidity.

Reviewer 2 Report

The manuscript is well written and presents well designed experiment with adequately statistical approach.

Material section provide key details on methods used.

The results and the discussions were detailed and were lead very well with board discussion with literature.

Conclusions are properly drawn.

Provided literature is relevant to the research and published mostly within last 5 years.

In subsection 3.3. Oenological Parameters Analysis, please make mention to the Table 1 and then insert it.

Author Response

RESPONSE TO REVIEWER 2

Reviewer 2:

We thank you for giving us an opportunity to revise our manuscript. We appreciate your positive comments and suggestions on our manuscript entitled ''The impact of indigenous non-Saccharomyces yeasts inoculated fermentations on ‘Semillon’ Icewine'' (No. 1861871).

These comments are all valuable and very helpful in revising and improving our paper. The text of our responses is highlighted in red (changes based on your comments). The revised text is also shown in red in the revised manuscript.

Comment 1. In subsection 3.3. Oenological Parameters Analysis, please make mention to the Table 1 and then insert it.

--Response 1: Please, we have made the correction as suggested.