Scaling Up Red Ginger Kombucha Fermentation: Insights into Its Chemical Profile and Health-Promoting Properties

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Authors were investigates the effects of scaling up red ginger kombucha as new, alternative kombucha beverage and same of the bioactive properties (antioxidant activity and antidiabetic characteristic) of ginger kombucha. The article is beneficial for researchers in related fields especially in scaling up of kombucha. But, I have the following concerns about the manuscript.

• The missing data are those related to geometric characteristics of fermentation reactors (“container”) – their diameter and liquid volume which are correlated with specific interfacial area as a key independent variable for scaling-up Kombucha fermentation (Cvetkovic et al., Journal of Food Engineering 85, 2008, 387–392).
• There is no data of sucrose content during fermentation. In addition, the authors did not explain the role of maltose for kombucha fermentation and their determination.
• The authors should explain why they did not use traditional kombucha made of sweetened black tea as control sample in their study.
• Some of the data for manufacturers and country of origin of chemicals and equipment are missing.
• Additionaly, specific minor remarks are given in the attached file

Comments for author File: Comments.pdf

Author Response

Attached is a table of responses containing our answers to Reviewer #1, #2, and #3. The changes have been highlighted in yellow or red for clarity.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

 

This study investigated the fermentation process of red ginger kombucha.

Parameters such as pH, titratable acidity, sugar content (including glucose, fructose, and maltose), organic acids (acetic acid, lactic acid, gluconic acid), total polyphenols, and total flavonoids were analyzed. The fermented red ginger kombucha showed the inhibitory activity of α-glucosidase.

 

The following suggestions are offered for revision.

 

Line 17~18

“using 10% red ginger concentration and 15% red ginger kombucha SCOBY”

Please check the correctness.

 

Line 23

vitamins, and enzymes

It is not the result from this study. It should be deleted.

 

Line 101~102

a Varian 5000 series liquid chromatograph fitted with a UV 100 spectrophotometric detector

Is it a HPLC instrument?  Please check the correctness.

 

Line 147 and 457

α-Glucosidase

 

Line 152

Was it added in a flask?

 

Line 173~174

The representation of significant figures should be consistent.

For example, 35.35 ± 0.04 ppm.

 

Line 176~182

(1) The methods for the extraction of red ginger should be presented.

(2) The methods for GC/MS analysis should be presented.

(3) Five, not six, compounds are shown in Table 1. (Line 177)

(4) Do the authors analyze the concentration of red ginger extracts after fermentation?

 

Line 183

This filtrate was combined with a 20% inoculum (v/v red ginger filtrate) and supplemented with sucrose (10% w/v red ginger filtrate). (Line 92~93)

(1) However, the authors did not analyze the concentration of sucrose; instead, they detected maltose. Please explain.

 

Line 197

What is the sample analyzed in Figure 3? Sugar standards?

 

Line 212~213

Initially, sucrose, the primary carbon source in kombucha, is hydrolyzed into glucose and fructose by the invertase enzyme produced by yeast.

Sucrose (10%) was added to prepare red ginger kombucha. However, the concentrations of glucose and fructose during 0 days were about 140,000 ppm (about 14%) and 100,000 ppm (about 10%). Please explain.

 

Line 304

It should be Figure 6.

 

Line 492~496

Research by Bhattacharya et al. [17] demonstrated that administering 150 mg kombucha tea to mice for 14 days led to a 56.4% reduction in blood glucose levels after being injected with streptozotocin (STZ).

The description is not consistent with “reference 17”.

(1) They used Alloxan instead of streptozotocin.

(2) 150 mg lyophilized extract/kg bw for 14 days

(3) 56.4% reduction in blood glucose levels?

Please check the correctness.

 

Line 494~496

The study also observed a reduction in blood glucose levels in mice from approximately ± 275 mg/dl to around ± 120 mg/dl.

(1) What is the reference?

(2) What mean of ±?

 

Line 496~498

Additionally, administering 1.71 mL of kombucha tea to hyperglycemic mice (equivalent to 75.25 mL in humans) showed a significant reduction in blood glucose levels [47,50].

(1) What is the reference?

Author Response

Attached is a table of responses containing our answers to Reviewer #1, #2, and #3. The changes have been highlighted in yellow or red for clarity.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The experimental article "Scaling Up Red Ginger Kombucha Fermentation: Insights into Its Chemical Profile and Health-Promoting Properties" devoted to the fermentation of red ginger extract with kombucha inoculum (SCOBY) with a scaling element is of interest, since the claimed food product red root is the basis for the beneficial properties of the drink discovered by the authors. The authors have already described their results using red ginger (links 15 and 16), but in this case they claim recognition of the scientific basis for scaling up the production of a drink from ginger. The article corresponds to this edition by all criteria, but for its publication the following recommendations must be met:

1. The authors should work on reducing the Percent match: 26% value.
2. In the materials and methods section, the authors should provide references to articles in which the analysis of flavonoids in aqueous media using AlCl3 should be done exactly this way: by methanol extraction of flavonoids from an aqueous medium for subsequent determination. 3. Lines 176-182. Similar to point 2, the authors should provide references to articles in which the analysis of the substances listed in Table 1 should be performed after extraction of these substances with hexane from the aqueous medium.
3. The materials and methods should provide data on the sugar content of the red root extract before adding sucrose and inoculum. It is recommended to provide as much information as possible on the composition of the obtained extract before adding sucrose and inoculum.
4. Lines 207-210. The authors should supplement this text with an explanation of the need for "optimization", since the results shown in Figure 4 are quite expected and do not cause for concern.
5. Lines 217-222. The authors must describe their observations regarding the formation (or complete absence) of a bacterial cellulose gel film in this process, since they are describing processes for using a carbon source during fermentation.
6. The recommendation is not fundamental, but it would be attractive to either remove the photo of ginger from the article in Supplementary and add a photo of the scaling setup, or exclude the photo of ginger, taking into account that this source for the drink has been published more than once.
7. Figure 6. The authors should compare their results with other examples of scaling up the drink and explain which results cause them concern. According to the reviewer, the results are quite expected and predictable. This is how it should be. Where do such doubts come from?
8. Figures 7 and 8. The authors should express their point of view: do they think that the observed differences are related to the use of red ginger? The reviewer is sure that the picture could be similar in its absence.
9. Figure 8. The observed difference at the beginning of the process requires explanation. The acid content in the range of 0.05-0.10% is very low. In this case, the source of the acid is red ginger itself. It is strange that the numbers differ... This means that the extracts were prepared differently.
10. Section 3.4. Total polyphenol content. The authors must prove that the increase in phenols is due to the formation of new phenols during fermentation. Where is the analysis of individual newly formed phenols?
11. Figure 10. The authors discuss the increase in flavonoid content, but this increase is so insignificant that it is worth paying attention to something else.
12. Lines 499-501. The authors failed to substantiate the statement in this sentence. It is necessary to expand and explain. Probably, the process control carried out by the authors “did not record” the reasons for the increase in the beneficial effect of the drink.
13. Figure 12. Why are different terms indicated in the figure title and on the ordinate axis? It is recommended to align them.
14. Taking into account recommendations 1-14, the authors should edit the Conclusion and Abstract. In the opinion of the reviewer, the authors were unable to record the reason for the appearance of such beneficial properties in the drink that they describe.
15. The reviewer still has a question about the quantity (output in terms of sugar taken for fermentation) of the bacterial cellulose gel film. If it is impossible to include information about this in the article, the reviewer expects an answer in the "Reviewer's Answers".

Author Response

Attached is a table of responses containing our answers to Reviewer #1, #2, and #3. The changes have been highlighted in yellow or red for clarity.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

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Reviewer 2 Report

Comments and Suggestions for Authors

The authors response well, so I have no more suggestion.