Use of Kombucha SCOBY and Commercial Yeast as Inoculum for the Elaboration of Novel Beer

Round 1

Reviewer 1 Report

In the present work, authors used a combination of kombucha SCOBY and commercial brewing yeast as a starter culture to produce a sour beer with limited alcohol content. Results indicated that kombucha-fermented wort produces a beer with specific characteristics, while the combination of kombucha and commercial yeast showed carbohydrate consumption and contents of organic acids similar to the control. Authors concluded that the use solely of kombucha as a starter culture produced a low-alcoholic product with specific properties such as high antioxidant activity and sour characteristics. In general, the work is very interesting, the experimental design is appropriate and the aim is clear. The results are well-presented and the discussion supports the findings to a high extent. The manuscript is well-written, even though a moderate English editing is recommended in some parts. I have some comments and suggestions for further improving the impact of the work.

 

-L20-22. The monitoring of microbial population growth throughout the fermentation (at least 2 more sampling points at the middle stage) would be very interesting and useful.

-L48-49. Please revise.

-L50. Please revise.

-L54-55. What kind of characteristics? Please specify.

-L74-75. Please revise.

-L124. What is the meaning of total bacteria? Maybe total viable counts? Please check and revise throughout the manuscript.

-L327-329. Why Malic and citric acid remained almost constant throughout the process? Please discuss more deeply this finding.

-L396-411. If no significant difference was observed between the treatments, the different values presented herein are almost negligible. You should refer only to a tendency, no differences, if the p value is close to 0.05, according to the statistical analysis. Please check carefully and revise accordingly.

 

A final paragraph (either at the end of the discussion or the conclusion section) highlighting the significance of the present study and how scientific/industry community could be benefited by these findings, is totally missing. Furthermore, authors should propose some “next steps” as future prospects. Both of them will strengthen the impact of the manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript presents interesting and novel data on the potential of using Kombucha microbial cultures to produce speciality beers with low alcohol content. The experimental approach and associated analyses look appropriate and the paper is well referenced. Overall, the content of this paper is relevant to the readership of the journal. Some comments for authors' consideration now follow:

- General comments. It is difficult to ascertain the significance of the claims that the total phenolics and antioxidant activity in kombucha produced beer are statistically different from control (yeast) beer. For example, Table 4 shows the standard deviations in the DPPH % inhibition, but authors do not comment on this in the text. The differences look minor. Regarding HPLC analyses, "peak areas" do not make much sense from a quantitative viewpoint, and if possible, such data should be reported in concentration terms. The kombucha beer is really incompletely fermented, but yeast was able to grow during fermentation. Authors should comment on this anomaly (being possibly sue to growth of non-Saccharomyces yeasts). It would have been nice if the authors were able to identify the yeast species in their kombucha SCOBY culture.

- Specific (minor) comments.:

lines 85-86. Need to define what is meant by "pre-fermented" kombucha liquid

line 112 "larger" beer (lager)

line 199 I don't think a final beer fermentation pH of 6.5 would be "ideal"

Table 2 Need to define ND

line 233 showed should be shown

line 323 h/L?

line 337 delete "Therefore"

line 350 Change to ...most beer styles.

line 382 Why was 4EG detected in the C beer? (No Brettanomyces)

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The revised manuscript has been improved. I have no further comments.