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Peer-Review Record

Investigation on the Quality of Commercially Available GABA Tea in Taiwan

Standards 2023, 3(3), 297-315; https://doi.org/10.3390/standards3030022
by Mu-Chen Wu 1, Shih-Lun Liu 2,3,4,*, Bo-Kang Liou 5, Chun-Yeh Chen 2 and Yuh-Shuen Chen 2,*
Reviewer 1:
Reviewer 2:
Reviewer 3:
Reviewer 4: Anonymous
Standards 2023, 3(3), 297-315; https://doi.org/10.3390/standards3030022
Submission received: 15 May 2023 / Revised: 17 August 2023 / Accepted: 18 August 2023 / Published: 28 August 2023

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors


Comments for author File: Comments.pdf

Comments on the Quality of English Language

The manuscripts needs a proof reading. There are  several language mistakes which needs to be corrected. 

Author Response

Q1:The manuscripts needs a proof reading. There are several language mistakes which needs to be corrected. Also, the manuscript needs a proof reading to get rid of several language problems.

A1: Thank you very much for reviewing our paper. The English language within the manuscript is revised, and showed by red text.

 

Q2: However, the manuscripts need to elaborate more on the consumer testing section. These elaborations would help first time readers to understand the research work in more depth.

A2: Thank you very much for reviewing our paper. (1) The section about consumer testing is supplemented into the introduction. It showed below in P2Line85-94.

In Taiwan, various GABA teas such as GABA Green, GABA Paochong tea, GABA Oolong tea, GABA Puerh tea, and GABA Black tea can be made depending on the level of fermentation (oxidation). In Japan, commercialized GABA tea is treated as a health food, and the quality of the tea product is evaluated based on the GABA content as the main criterion. In order to ensure that the beverage products will sell well, it is important to understand the wants and needs of the consumers [23]. But the results of the tea competition in Taiwan usually affect the quality and price of the tea. The award-winning tea selected by the judges does not reflect that it will be liked and purchased by consumers [24]. The consumer acceptance test is the most appropriate way to understand how consumers feel about food and the willingness of consumers to buy it [25].

 

(2) The section about consumer testing is supplemented in the Results and Discussion. It showed below in P13Line502-508.

No clear trend in the acceptance of appearance and aftertaste was seen between high and low GABA content groups in GABA Black tea, GABA Oolong tea, and GABA Paochung tea. However, in terms of flavor, the high content group is more acceptable than the low content group. In the overall acceptability, it was also observed that the GABA tea in the high content group was higher than that in the low content group. Therefore, it can be hypothesized that the flavor of GABA is an important factor affecting the overall acceptability.

 

(3) The section about consumer testing is supplemented in the Results and Discussion. It showed below in P13Line517-525.

Nonetheless, overall-liking ranged from “dislike slightly” to “like moderately”, suggesting that different types of GABA teas are accepted by consumers and have potential for mar-ketability [31]. The full fermentation process of black tea and the post-fermentation process of Puerh tea will give the finished tea a sour flavor [36,37]. The light-fermentationof of Paochong tea gives the finished tea a special floral flavor [36]. These special flavor of these three teas are the same as the floral and acidic flavor produced by the anaerobic process of the original GABA tea [31]. We hypothesize that this is the reason for the higher accepta-bility of GABA Black tea, GABA Puerh tea and GABA Paochong tea.

 

Q3: Additionally, the principal components analysis (PCA) results need to be explained properly. As of now, there are several statements which are either not clearly written or not supported by the data. Authors are advised to rewrite the PCA results.

A3: Thank you very much for reviewing our paper. The discussion about the PCA has been revised, please see the answersfrom Q19 to Q23. In addition, according to the suggestion of other reviewers, the PCA plots of GABA Paochung Tea, GABA Green Tea and GABA Puerh Tea were added. The discussions about the GABA Paochung Tea, GABA Green Tea and GABA Puerh Tea were added as below in P13Line483-488:

“In terms of the GABA Paochung tea, GABA Green tea, and GABA Puerh tea, the first two components could explain for 72%, 87%, and 90% of variance, respectively. Because of the small number of samples of these three types of GABA tea, it can only be roughly seen that the six main physico-chemical constituents are positively correlated with the first principal constituent, indicating that tea samples with high GABA content have a ten-dency to have high levels of the other five constituents.”

 

Q4: Line 19-20: Please check the total sample size of tea types. As of now it counts to 221 instead of 220.

A4: Thank you very much for reviewing our paper. The total number of GABA tea samples in this study is 220. The 221 samples in the abstract are wrong, it has been corrected. The numbers of GABA Oolong tea are 108, not 109.

 

Q5: Line 22-24: “the distribution……. Oolong tea ranged from 116 to 192 mg/100g”, please check the language.

A5: Thank you very much for reviewing our paper. The sentences are revised as in P1Line22-25 “The GABA content varied among the different types of GABA teas: GABA Oolong tea ranged from 1116-192 mg/100g, GABA Black tea ranged from 182-367 mg/100g, GABA Paochong tea ranged from 192-211 mg/100g, GABA Green tea ranged from 153-171 mg/100g, and GABA Puerh tea ranged from 1142-191 mg/100g.”

 

Q6: Line 22-24: Please arrange the tea type name in either ascending or descending order of GABA content. It is exceedingly difficult to follow.

A6: Thank you very much for reviewing our paper. The different types of GABA tea listed here are sorted according to the number of samples of different types of GABA tea, in descending order. This is the order in which they are described in the following manuscripts.

 

Q7: Line 31-32: “It is assumed….. combined more closely are similar”, the sentence is not clear. Authors are advised to rewrite it.

A7: Thank you very much for reviewing our paper. It is revised, the sentence showed as in P1Line30-32 “The sour flavor in GABA tea is similar to the original sour sensory properties found in black tea. It is assumed that the main reason GABA black tea has the highest acceptance.”

 

Q8: Line 49: “When blood GABA levels of blood decrease”, please revise the language.

A8: Thank you very much for reviewing our paper. The sentences are revised as P2Line57-58 “The risk of mania, bipolar disorder, anxiety, and depression is increased when the level of GABA contents in blood decreases by 10% to 15% [12].”

 

Q9: It would be extremely helpful if authors could provide the fermentation duration/time of these samples. It is paramount to provide sample preparation details so that the scientific community can conduct similar research using same conditions.

A9: Thank you very much for reviewing our paper. The 220 samples collected in this study were produced by over 50 different manufacturers. Because of the large number of GABA teas and manufacturers, it was not possible to collect and compare the aerobic-anaerobic fermentation time and frequency of each manufacturer. Scholars have compared the effects of different fermentation conditions on the GABA content of GABA tea after different repeated aerobic-anaerobic fermentation. We have added these sentences to the manuscript. It was showed below in P6Line237-239.

“The study of Wu and Ou showed that the GABA contents of GABA tea with aero-bic-anaerobic fermentation could increase by 14-104 times [30].”

 

Q10: Line 100-101: “stored in a -80° C freezer”. Please check the storage temperature of the freezer.

A10: Thank you very much for reviewing our paper. The sentence is added in the manuscript. It showed as P6Line122-123 “Temperature records for the freezer over a 5-year storage period show a range of -80.6 to -82.1 oC.”

 

Q11: Line116: Please check the language

A11: Thank you very much for reviewing our paper. It is revised as in P3Line154 “No GABA tea samples were produced in this area”

 

Q12: Section 2.3. Consumer acceptance of GABA tea. This section needs details for readers to understand how the consumer study was conducted.

How were the consumers recruited?

What was the consumer profile? Example, age, gender, income, etc.

Total how many samples were tasted by consumer in how many sessions?

What was the amount of tea consumed for evaluation? How did researchers ensure that consumers are drinking the amount of tea required to form an opinion?

Seems like consumer tasted 8 tea samples in one session. This is an extremely high number of products to taste in one session. How did researchers ensure that higher number of samples did not overwhelmed consumer palates.

A12: Thank you very much for reviewing our paper.

The process of the consumer acceptance test is supplemented as follows.

P4Line188-189

“The 101 volunteer respondents (48 male and 53 female students between the ages of 18-26 years old were invited from Hungkuang University) were participated in this study.”

In P4Line194-199

“The tea infusions were brewed with 3 g of tea leaf and 150 mL of boiling distilled water for 5 min (strip type GABA tea) or 6 min (ball type GABA tea) at a time. As the tasting progresses, the required amount of tea infusion was filled into vacuum bottles and served to the respondents. 30mL of tea infusion was provided to each respondent, if there was not enough for the respondent, the reserve staff would replenish the tea infusion”

“In terms of simple consumer acceptance test, the number of samples that can be evaluated by a tester at one time can be as high as 6-8 [32].”

 

Q13: Please provide before and after fermentation GABA contents of each tea sample to validate that fermentation does increase the GABA content of the teas sample. Also, cite research papers which might have concluded similar findings.

A13: Thank you very much for reviewing our paper. The 220 samples collected in this study were produced by over 50 different manufacturers. It was not possible to collect and compare the amount of increasing of GABA content for different sample. Scholars have compared the effects of different fermentation conditions on the GABA content of GABA tea after different repeated aerobic-anaerobic fermentation. We have added these sentences to the manuscript. It was showed below in P6Line237-239.

“The study of Wu and Ou showed that the GABA contents of GABA tea with aero-bic-anaerobic fermentation could increase by 14-104 times [30].”

 

Q14: Line 176-177: “GABA Oolong tea (ball type; 108 samples)”. The Oolong tea sample size does not match the sample size mentioned in the abstract (Line 19-20).

A14: Thank you very much for reviewing our paper. The sample size (221) mentioned in the abstract is wrong. This section has been amended to 220 tea samples.

 

Q15: Line 203: “that creates a boring and sour taste”, please cite the source of this information.

A15: Thank you very much for reviewing our paper. It is revised as in P6Line247-249 “Therefore, a repeated aerobic-anaerobic tea fermentation process was created to not only increase GABA content but also reduce the pungent smell [10].”

 

Q16: Line 205-206: “The original flavors of GABA Green and GABA Paochong teas are described as sweetness, fresh, and floral aroma”. Please cite the source of this information.

A16: Thank you very much for reviewing our paper. It is revised as in P6Line249-250 “The original flavors of Green and Paochong teas are described as sweetness, fresh, and floral aroma [31].”

 

Q17: Line 208-209: “The aerobic-anaerobic fermentation process is necessary for increasing the GABA content of GABA Green and Paochong tea as well as preventing the boring flavor”. Please cite the source of this information.

A17: It is revised as in P6Line252-253 “The aerobic-anaerobic fermentation process is necessary for increasing the GABA content of GABA Green and Paochong tea as well as preventing the boring flavor [10,22].”

 

 

Q18: Line 211-212: “This explains the low GABA con tent in commercially available GABA Green and Paochong teas, which is understandable from a production perspective”. Please cite the source of this information.

A18: Thank you very much for reviewing our paper. It is revised as in P6Line253-255 “If the aerobic-anaerobic fermentation process is overdone, although it will increase the content of GABA, it will affect the original unique taste of Green tea and Paochong tea [31]. This explains the low GABA content in commercially available GABA Green and Pao-chong tea.”

 

Q19: Line 339-340: “positively correlated with the GABA, TF, TR, TB, and TP contents, and negatively correlated with the TC content”. Authors are requested to check the physico-chemical constituents’ correlation with principal components. In the above-mentioned statement, the first principal component was positively correlated with the GABA, TF, TR, TB, and TC contents, and negatively correlated with the TP content.

Line 340-342: ‘The second principal component was positively correlated with the GABA, TB, and TP contents, and negatively correlated with the TF and TR contents”. Authors are requested to check the physico-chemical constituents’ correlation with both principal components (Similar to line 339-340).

A19: Thank you very much for reviewing our paper.

(1) In the manuscript, the following sentences is added to explain the relationship between the components and the different main components. It is showed in P10Line382-385 “In the result of PCA plot, a positive value of the distribution position of each physi-co-chemical component on the X-axis or Y-axis means that the component is positively correlated with that principal component, and vice versa.”

 

(2) Some error occurred in the discussion section of the PCA results, which have been corrected as follows in P10Line385-P11Line390:

Figure 1 also showed that the first principal component was positively correlated with the GABA, TF, TR, TB, and TC contents, and negatively correlated with the TP content. The second principal component was positively correlated with the GABA and TB contents, and negatively correlated with the TF, TR, and TP contents. This corroborates the previous observation in which spring and winter GABA teas contained lower levels of GABA and TB and higher levels of TF and TR.

 

Q20: Line 345: “The Figure shows GABA Black tea in the first and fourth quadrants and GABA Green”, please provide figure number.

A20: Thank you very much for reviewing our paper. It is revised as in P11Line407 “The Figure 1 shows GABA Black tea in the first and fourth quadrants and GABA Green tea in the third quadrant,”

 

Q21: Line 349: “Based on the PCA comparing different GABA Oolong tea samples (Figure 2)”, please correct the figure number.

A21: Thank you very much for reviewing our paper. The number of this figure is wrong. In addition, according to the suggestion of other reviewers, the PCA plots of GABA Paochung Tea, GABA Green Tea and GABA Puerh Tea were added, so it is revised as follows in P11Line411-412: “Based on the PCA comparing different GABA Oolong tea samples (Figure 2a)”

 

Q22: Line 352-354: “Figure 2 shows that GABA Oolong teas with low GABA levels had higher TC and TR contents but lower TP, TF, and TB levels than regular GABA Oolong teas”. The data does not support this statement. Please rewrite the trend instead of making a conclusive statement.

A22: Thank you very much for reviewing our paper. The statement is wrong, it is revised as in P11Line414-418 “The figure 2a shows that the correlation among GABA, TC, TF, and TB contents were high, but they were negatively correlated with the TP and TR contents. This result meant that GABA Oolong teas with low GABA levels also had lower TC, TF, and TB contents, but contained higher TP and TR contents than regular GABA Oolong teas.”

 

Q23: Line 357-358: “GABA Black tea with high GABA contents had higher TC, TF, and TR levels but lower TP and TB levels than regular GABA Black teas”. The data does not support this statement. Please rewrite the trend instead of making a conclusive statement.

A23: Thank you very much for reviewing our paper. The statement is wrong, it is revised as in P11Line421-P13Line479-782 “The figure 2b shows that the correlation among GABA, TC, and TB contents were high, but they were negatively correlated with the TP ,TF, and TR contents. This result meant that GABA Black tea with high GABA contents had higher TC and TB levels but lower TP, TF and TR levels than regular GABA Black teas,”

 

Q24: Figure 1: Please add legends to the figure for reader to understand sample names, and physico-chemical constituents name without going back and forth. The figures must be self-explanatory for readers.

Figure 2: Please add legends to the figure for reader to understand sample names, and physico-chemical constituents name without going back and forth.

Figure 3: Please add legends to the figure for reader to understand sample names, and physico-chemical constituents name without going back and forth.

A24: Thank you very much for reviewing our paper. It is revised in Figure 1and Figure2. It showed as below:

“The sample code: the first code means the category of GABA tea: B (GABA Black tea), O (GABA Oolong tea), P (GABA Paochung tea), G (GABA Green tea), U (GABA Puerh tea); the second code means the GABA contents of GABA tea: H (the GABA content is above 200 mg per 100 g tea), L (the GABA content is between 150 to 200 mg per 100 g tea), U (the GABA content is below 150 mg per 100 g tea); the third code means the production area of GABA tea: A (Alishan), N (Nantou), C (Central Taiwan), O (Others); the fourth code means the production season of GABA tea: S (spring), H (summer), F( fall) and W (winter); the last three code was the numbers of tea sample of different category of GABA tea.”

 

Q25: Line 373: The sample size of GABA Oolong tea sample does not match with samples size mentioned in the abstract.

A25: Thank you very much for reviewing our paper. The sample size (221) mentioned in the abstract is wrong. This section has been amended to 220 tea samples.

 

Q26: Line 390-391: “not only had a good blood pressure lowering effect”. Please cite the source of this information.

A26: Thank you very much for reviewing our paper. It is revised as in P13Line514”had good blood pressure lowering effects [10]”

 

Q27: Line 396-397: “This finding suggests that the anaerobic fermentation process of GABA tea produces a sour taste”. Authors are requested to provide data to support the above-mentioned statement.

A27: Thank you very much for reviewing our paper. It is revised as in P13Line526-528 ”This finding suggests that the anaerobic fermentation process of GABA tea produces a sour taste [10,18], which can be closely combined with the flavor characteristics of Black tea [33] to enhance the acceptability of GABA teas by consumers.”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript analyses 220 commercially available samples of γ-Aminobutyric acid (GABA) tea produced in Taiwan from 2016 to 2021 and categorizes them by type, region, and season. The physico-chemical composition and consumer acceptance of GABA tea were analyzed to evaluate its commercialization potential. The manuscript has a large data, but it lacks innovation, originality, especially the depth of analysis and discussion is really very poor, and it also has many problems as follows.

1.       The classification order of GABA tea in L19-20 should be consistent with the sample narrative order of GATA content in L22-26 and the sample order in tables such as Table 1 and Table 2.

2.       L19: Check whether the sample size for GABA Oolong tea is 109 or 108.

3.       L82-83 states that there are only few institutions in Taiwan that can analyze the GABA content in GABA tea. However, the study in the literature "Comparison of bioactive components in GABA tea and green tea produced in Taiwan" has been able to analyze the GABA content in GABA tea.

4.       The classification order of GABA tea in L106-108 should be consistent with the sample order in Table 1.

5.       The number of samples with a GABA content greater than 300 mg/100 g in Appendix A is 5. If 6 is correct, the total number of samples with a GABA content greater than 200 mg/100 g is 6 + 39 + 31 = 76, please check if 75 is correct.

6.       The results were shown in Table 5 for GABA black tea and GABA oolong tea only, and "The results were shown in Table 5" in L304 should be presented in the following paragraph.

7.       L343 “summer and winter GABA teas contained lower levels of GABA and TB and higher levels of TF and TR” and L268 “summer and fall teas contained higher levels of GABA and TB than the spring and winter teas” have the same physical and chemical properties but correspond to different seasons. Please explain the reason.

8.       Figure 2 shows the GABA Black tea sample, whereas the statement in L349 reads "GABA Oolong tea samples (Figure 2)". The description and figure do not correspond correctly.

9.       The narrative in the manuscript does not indicate Figure 3, which should be indicated in the narrative.

10.     What does " The GABA Green and Puerh teas, as well as their low-GABA level counterparts " mean in terms of samples? The preceding materials and methods do not mention consumer acceptance of Green and Puerh teas.

11.     According to Table 6, "Overall Liking" is greater for GABA Paochong tea than GABA Oolong tea. However, L416 is stated as "followed by GABA Oolong". Please explain why the preference for GABA Oolong tea is greater than that for GABA Paochong tea.

12.     The header section of the table in Appendix A should indicate the units for each indicator.

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Q1: This manuscript analyses 220 commercially available samples of γ-Aminobutyric acid (GABA) tea produced in Taiwan from 2016 to 2021 and categorizes them by type, region, and season. The physico-chemical composition and consumer acceptance of GABA tea were analyzed to evaluate its commercialization potential. The manuscript has a large data, but it lacks innovation, originality, especially the depth of analysis and discussion is really very poor.

A1: Thank you very much for reviewing our paper. The purpose of this study and the questions it hopes to address are described more clearly in the introduction. It is showed below in P2Line85-94.

In Taiwan, various GABA teas such as GABA Green, GABA Paochong tea, GABA Oolong tea, GABA Puerh tea, and GABA Black tea can be made depending on the level of fermentation (oxidation). In Japan, commercialized GABA tea is treated as a health food, and the quality of the tea product is evaluated based on the GABA content as the main criterion. In order to ensure that the beverage products will sell well, it is important to understand the wants and needs of the consumers [23]. But the results of the tea competition in Taiwan usually affect the quality and price of the tea. The award-winning tea selected by the judges does not reflect that it will be liked and purchased by consumers [24]. The consumer acceptance test is the most appropriate way to understand how consumers feel about food and the willingness of consumers to buy it [25].

In P2Line95-P3Line102

Wang et al., found that the tea infusion brewer from GABA tea leaves that met Japa-nese commercial standards (150 mg GABA per 100 g tea leaves) was effective against es-sential hypertension in mice after 12 weeks of feeding [20], and it was also effective in human [26]. There are various types of GABA tea produced in Taiwan, each with its unique flavor. However, there has been no survey on whether the commercially available GABA teas meet the Japanese commercialization standards. If the GABA content of GABA tea does not meet the commercial standards, its health benefits may not be achieved after drinking.

 

In P3Line105-111

The first aim of this study was to see if the GABA tea sold in Taiwan met the commercial standard and to determine whether consumers accept the consumption of functional GABA tea. The second aim was to compare the influences of different production methods, production regions, and harvest seasons on the quality of Taiwan GABA tea. The third aim was to compare the effort of different tea manufacturing processes on the GABA con-tent of GABA tea. It is expected that the result could provide a reference for tea manufacturers.

 

Q2: The classification order of GABA tea in L19-20 should be consistent with the sample narrative order of GATA content in L22-26 and the sample order in tables such as Table 1 and Table 2.

A2: Thank you very much for reviewing our paper. The different types of GABA tea listed here are sorted according to the number of samples of different types of GABA tea, in descending order. This is the order in which they are described in the following manuscripts.

 

Q3: L19: Check whether the sample size for GABA Oolong tea is 109 or 108.

A3: Thank you very much for reviewing our paper. The sample size (221) mentioned in the abstract is wrong. This section has been amended to 220 tea samples.

 

Q4: L82-83 states that there are only few institutions in Taiwan that can analyze the GABA content in GABA tea. However, the study in the literature "Comparison of bioactive components in GABA tea and green tea produced in Taiwan" has been able to analyze the GABA content in GABA tea.

A4: Thank you very much for reviewing our paper. Although there are a number of research units in Taiwan that have conducted GABA-related research. Few research units in Taiwan can be commissioned to conduct GABA testing. However, the sentence was deleted in accordance with reviewers' suggestion.

 

Q5: The classification order of GABA tea in L106-108 should be consistent with the sample order in Table 1.

A5: Thank you very much for reviewing our paper. It is revised. And the sample order of different GABA tea in each table is revised, too.

 

Q6: The number of samples with a GABA content greater than 300 mg/100 g in Appendix A is 5. If 6 is correct, the total number of samples with a GABA content greater than 200 mg/100 g is 6 + 39 + 31 = 76, please check if 75 is correct.

A6: Thank you very much for reviewing our paper. It is revised. The number of GABA tea with a GABA content greater than 300 mg/100 g is 5. And the number of GABA tea with a GABA content greater than 200 mg/100 g is 75. It is revised as P9Line346-347 “We classified our samples based on the GABA content: greater than 300 mg/100 g (5 samples),”

 

Q7: The results were shown in Table 5 for GABA black tea and GABA oolong tea only, and "The results were shown in Table 5" in L304 should be presented in the following paragraph.

A7: Thank you very much for reviewing our paper. The order of Table 4 and Table 5 is revised in the right paragraph.

 

Q8: L343 “summer and winter GABA teas contained lower levels of GABA and TB and higher levels of TF and TR” and L268 “summer and fall teas contained higher levels of GABA and TB than the spring and winter teas” have the same physical and chemical properties but correspond to different seasons. Please explain the reason.

A8: Thank you very much for reviewing our paper. There was an error in L343's description, which has been revised as in P11Line389-390 “spring and winter GABA teas contained lower levels of GABA and TB and higher levels of TF and TR”

 

Q9: Figure 2 shows the GABA Black tea sample, whereas the statement in L349 reads "GABA Oolong tea samples (Figure 2)". The description and figure do not correspond correctly.

A9: Thank you very much for reviewing our paper. There was an error in the order of Figure 2 and Figure 3. It is revised. In addition, according to the suggestion of other reviewers, the PCA plots of GABA Paochong Tea, GABA Green Tea and GABA Puerh Tea were added into Figure 2.

 

Q10: The narrative in the manuscript does not indicate Figure 3, which should be indicated in the narrative.

A10: Thank you very much for reviewing our paper. It is revised. The PCA plots of GABA Oolong tea, GABA Bloack tea, GABA Paochong Tea, GABA Green Tea and GABA Puerh Tea are showed in Figure 2.

 

Q11: What does " The GABA Green and Puerh teas, as well as their low-GABA level counterparts " mean in terms of samples? The preceding materials and methods do not mention consumer acceptance of Green and Puerh teas.

A11: Thank you very much for reviewing our paper. Because all GABA Green and GABA Puerh teas contain less than 200 g of GABA per 100 g tea leaves, they are all regarded as GABA teas with low GABA content. This is revised as in P13Line498-500 “For GABA Green tea and GABA Puerh tea, because of their low GABA content, 2 random-ly selected tea samples from these two kinds of GABA tea were regarded as the low GABA content group”

 

Q12. According to Table 6, "Overall Liking" is greater for GABA Paochong tea than GABA Oolong tea. However, L416 is stated as "followed by GABA Oolong". Please explain why the preference for GABA Oolong tea is greater than that for GABA Paochong tea.

A12: Thank you very much for reviewing our paper. The sentences are revised as in P14Line548-550 “In terms of consumer acceptance, GABA Black tea was the most popular, followed by GABA Puerh and GABA Oolong tea,”

 

Q13: The header section of the table in Appendix A should indicate the units for each indicator.

A13: Thank you very much for reviewing our paper. They are revise in table in Appendix A

 

Q14: Moderate editing of English language required

A14: Thank you very much for reviewing our paper. The English language within the manuscript is revised, and showed by red text.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

·        The English language needs to be improved (spell and check).

For example Line 90 – influences

                                     Line 91 – Taiwanese

                 Table 2 – the standard deviation should be added

                 The rows of Table 2 should be separately dived, as in Table 3.

                 Table 3 – the standard deviation should be added

                 Line 108 – Among the 108 GABA Oolong

                 Table 4 – the standard deviation should be added

                 Table 5 – repetition of previous results? I think this Table is not necessary

                 Figure 1 is not clear and is a bit of a confusing picture. The results of PCA analysis should be separated by tea type (Black tea, Oolong tea, Paochong tea, Green tea, and Puerh tea), representing the 5-year response on GABA, TF, TR, TB, TC, TP, and consumer acceptance.

                 Table 6 – Are the values in Table 6 the average values? Please add the standard deviation

                 Consumer acceptance – what is the shelf life of each tea type? The points of the 9-point hedonic scale were analyzed for each year of the 5-year long period?

 

 

The authors processed an extremely large number of samples (220, 5 types of tea) about the 5-year period. According to the experimental results, there were 5 different variables: tea type, year of tea production, region, anaerobic/aerobic fermentation, and period of tea harvesting (spring, fall, summer, winter) and 7 different responses (GABA, TF, TR, TB, TC, TP, and consumer acceptance). According to the presented PCA analysis, it is hard to notice the positive/negative correlation between the variables in different responses. Authors are encouraged to separate PCA analysis to each tea type or to add statistic method (such as a Color correlation diagram). Please see the recommended literature:

                 Filipović, V., Lončar, B., Knežević, V., Nićetin, M., Filipović, J., Petković, M. (2023). Modeling the Effect of Selected Microorganisms’ Exposure to Molasses’s High-Osmolality Environment. Applied Science, 13: 1207. https://doi.org/10.3390/app13021207

                 Petković, M., Filipović, V., Lončar, B., Filipović, J., Miletić, N., Malešević, Z., Jevremović, D. A. (2023). А Comparative Analysis of Thin-Layer Microwave and Microwave/Convective Dehydration of Chokeberry. Foods 2023, 12 (8), 1651. https://doi.org/10.3390/foods12081651

Author Response

Q1: English language needs to be improved (spell and check).

For example Line 90 – influences

Line 91 – Taiwanese

A1: Thank you very much for reviewing our paper. The English language within the manuscript is revised, and showed by red text.

 

Q2: Table 2 – the standard deviation should be added

  • The rows of Table 2 should be separately dived, as in Table 3.
  • Table 3 – the standard deviation should be added
  • Table 4 – the standard deviation should be added

A2: Thank you very much for reviewing our paper. The tables are revised.

 

Q3: Line 108 – Among the 108 GABA Oolong

A3: The numbers of GABA Oolong tea is 108.

 

Q4:Table 5 – repetition of previous results? I think this Table is not necessary

A4: Thank you very much for reviewing our paper. Table 5 is to facilitate readers to clearly compare the difference between GABA tea with high GABA content (above 200 mg/100 g) and low GABA content (between 150-328 200 mg/100 g). Using the GABA content as the important indicator, the high and low GABA content GABA Oolong and GABA Black teas were grouped and calculated with descriptive statistics.

 

Q5: Figure 1 is not clear and is a bit of a confusing picture. The results of PCA analysis should be separated by tea type (Black tea, Oolong tea, Paochong tea, Green tea, and Puerh tea), representing the 5-year response on GABA, TF, TR, TB, TC, TP, and consumer acceptance.

A5: Thank you very much for reviewing our paper. In accordance with the recommendations, different types of GABA teas were analysed by PCA analysis and are listed in Figures 2a to 2e.

 

Q6: Table 6 – Are the values in Table 6 the average values? Please add the standard deviation

A6: Thank you very much for reviewing our paper. The scores in Table 6 are average values of 2 tea samples each type of GABA tea sample (8 types). The standard deviation is added in Table 6.

 

Q7: Consumer acceptance – what is the shelf life of each tea type? The points of the 9-point hedonic scale were analyzed for each year of the 5-year long period?

A7: Thank you very much for reviewing our paper. Under normal circumstances, Taiwan tea can be stored in aluminum foil vacuum bags for three years with no change in quality. In this study, in order to maintain the stability of the tea quality, so that all the tea samples could be collected and then analyzed for evaluation at one time. The tea leaves were vacuum sealed in aluminum foil vacuum bags and stored in the refrigerator at -80 degrees Celsius. It is revised as in P3Line120-125 “The other part was vacuum sealed in aluminum bags and stored in a -80 oC freezer to en-sure that the quality of the tea leaves could be maintained at a constant level. Temperature records for the freezer over a 5-year storage period show a range of -80.6 to -82.1 oC. Awaiting the end of the whole project in 2021, total 8 vacuum sealed and frozen samples will be randomly selected for consumer testing in 2022.”

 

Q8: The authors processed an extremely large number of samples (220, 5 types of tea) about the 5-year period. According to the experimental results, there were 5 different variables: tea type, year of tea production, region, anaerobic/aerobic fermentation, and period of tea harvesting (spring, fall, summer, winter) and 7 different responses (GABA, TF, TR, TB, TC, TP, and consumer acceptance). According to the presented PCA analysis, it is hard to notice the positive/negative correlation between the variables in different responses. Authors are encouraged to separate PCA analysis to each tea type or to add statistic method (such as a Color correlation diagram). Please see the recommended literature:

A8: Thank you very much for reviewing our paper. In accordance with the recommendations, different types of GABA teas were analysed by PCA analysis and are listed in Figures 2a to 2e. Also, lines are added to the PCA diagrams so that readers can recognize them more clearly.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

 This study collected 220 commercially available samples of γ-Aminobutyric acid (GABA) 17 tea produced in Taiwan from 2016 to 2021. The results of physico-chemical constituents analysis revealed that during the anaerobic fermentation process of production of GABA tea, the GABA content increased and theabrownins increased considerably, while theaflavins and thearubigins increased marginally.

Some suggestions are as follows:

The title is clear, but it could be enhanced by including the objective and research approach of the investigation.

The abstract mentions consumer acceptance but does not provide specific data or results related to consumer preferences. The last sentence seems incomplete and unclear.

·Consider rephrasing sentence 37 for clarity: "GABA (γ-Aminobutyric acid) is a hydrophilic non-proteinogenic amino acid that is naturally present in the brain and spinal cord of mammals, acting as an important inhibitory neurotransmitter in the central nervous system [1, 2]."

·In sentence 48, it seems that there may be a typo or missing information. Please review and revise accordingly.

·Expand on the studies mentioned in sentences 41-44 that demonstrate the physiological benefits of GABA, including references or brief summaries of the findings.

·Provide more context or references for the antihypertensive properties of GABA mentioned in sentences 45-47 to support the statement.

·Clarify the sentence in which the decrease in blood GABA levels is associated with an increased risk of mania, bipolar disorder, anxiety, and depression (sentence 49) by adding a reference or further explanation.

·Provide references or specific studies to support the claim in sentences 51-53 that GABA supplementation through food intake effectively prevents anxiety, uneasiness, fatigue, and nervousness.

·Consider providing references or citations for the studies mentioned in sentences 62-64 that demonstrate the potential benefits of GABA tea on renal function and life expectancy.

·Revise sentence 66 for clarity: "The method of GABA tea production was introduced from Japan to Taiwan in 1994, initially using a single anaerobic fermentation process that resulted in tea leaves with a dull sour taste and odor [22]."

·Include a brief explanation or reference to support the claim in sentences 77-78 that locally produced GABA tea in Taiwan now parallels the flavor of Taiwan Oolong tea.

·Add references or citations to support the statements made about the effectiveness of GABA tea against essential hypertension in mice and humans (sentences 80-82).

·Provide more information about the limitations or challenges associated with analyzing GABA content in GABA tea (sentence 83) to highlight the significance of the study.

·If applicable, mention the distribution of the sample types across different production areas and seasons to give a clearer picture of the sample distribution.

 Adding additional details and references would further enhance the clarity and reproducibility of the methods.

·Consider providing information on any potential biases or limitations of the consumer acceptance test, such as demographic characteristics of the respondents or the representativeness of the sample.

Comments on the Quality of English Language

Overall, the manuscript's English language quality is strong, and these suggestions are minor refinements to further enhance the clarity and precision of the content.

Author Response

Q1: The title is clear, but it could be enhanced by including the objective and research approach of the investigation.

A1: Thank you very much for reviewing our paper. The purpose of this study and the questions it hopes to address are described more clearly in the introduction. It is showed below in P2Line85-94.

In Taiwan, various GABA teas such as GABA Green, GABA Paochong tea, GABA Oolong tea, GABA Puerh tea, and GABA Black tea can be made depending on the level of fermentation (oxidation). In Japan, commercialized GABA tea is treated as a health food, and the quality of the tea product is evaluated based on the GABA content as the main criterion. In order to ensure that the beverage products will sell well, it is important to understand the wants and needs of the consumers [23]. But the results of the tea competition in Taiwan usually affect the quality and price of the tea. The award-winning tea selected by the judges does not reflect that it will be liked and purchased by consumers [24]. The consumer acceptance test is the most appropriate way to understand how consumers feel about food and the willingness of consumers to buy it [25].

In P2Line95-P3Line102

Wang et al., found that the tea infusion brewer from GABA tea leaves that met Japa-nese commercial standards (150 mg GABA per 100 g tea leaves) was effective against es-sential hypertension in mice after 12 weeks of feeding [20], and it was also effective in human [26]. There are various types of GABA tea produced in Taiwan, each with its unique flavor. However, there has been no survey on whether the commercially available GABA teas meet the Japanese commercialization standards. If the GABA content of GABA tea does not meet the commercial standards, its health benefits may not be achieved after drinking.

 

In P3Line105-111

The first aim of this study was to see if the GABA tea sold in Taiwan met the commercial standard and to determine whether consumers accept the consumption of functional GABA tea. The second aim was to compare the influences of different production methods, production regions, and harvest seasons on the quality of Taiwan GABA tea. The third aim was to compare the effort of different tea manufacturing processes on the GABA con-tent of GABA tea. It is expected that the result could provide a reference for tea manufacturers.

 

 

Q2: The abstract mentions consumer acceptance but does not provide specific data or results related to consumer preferences. The last sentence seems incomplete and unclear.

A2: Thank you very much for reviewing our paper. Relevant sentences about consumer acceptance have been revised as in P1Line28-32 “ In terms of consumer acceptance, GABA Black tea is the most accepted by consumers, followed by GABA Puerh tea, GABA Paochong and GABA Oolong tea. The sour flavor in GABA tea is similar to the original sour sensory properties found in black tea. It is assumed that the main reason GABA black tea has the highest acceptance.”

 

Q3: Consider rephrasing sentence 37 for clarity: "GABA (γ-Aminobutyric acid) is a hydrophilic non-proteinogenic amino acid that is naturally present in the brain and spinal cord of mammals, acting as an important inhibitory neurotransmitter in the central nervous system [1, 2]."

A3: Thank you very much for reviewing our paper. It is revised as in P1Line37-39 “GABA (γ-Aminobutyric acid) is a hydrophilic non-proteinogenic amino acid. The GABA is naturally present in the brain and spinal cord of mammals, acting as an important inhibitory neurotransmitter in the central nervous system [1, 2].”

 

Q4: In sentence 48, it seems that there may be a typo or missing information. Please review and revise accordingly.

A4: Thank you very much for reviewing our paper. It is revised as in P2Line55-56 “Wamg et al., indicated that once the GABA content in GABA tea is above 150 mg GABA per 100 g made tea, there was good anti-hypertensive effect [10,11].”

 

Q5:: Expand on the studies mentioned in sentences 41-44 that demonstrate the physiological benefits of GABA, including references or brief summaries of the findings.

A5: Thank you very much for reviewing our paper. It is revised as in P2Line41-P3Line51 “GABA tea has many important physiological benefits. Jolivalt et al., indicated that increased GABA release contribute to spinally-mediated hyperalgesia in diabetes [4]. Gottesmann et al., and Zhao et al., indicated that the GABA black tea had s ignificant effects on prolong-ing sleeping time with sodium pentobarbital (P<0.05) and GABA black tea improved the sleeping quality of mice to extend with 35 optimal effect in the high dose -treated mice. [5,6]. Koob indicated that the effects of alcohol with GABA antagonists can be antagonized, particularly its sedative, anxiolytic‐like, and acute reinforcing actions [7]. Powers indicat-ed that GABA in the control of GH release by actions at either hypothalamic or pituitary sites. So GABAcould control of GH secretion [8] Pea and Tapia indicated GABA receptor antagonists clearly diminished the intensity of seizures and prevented the neuronal damage [9].”

 

Q6: Provide more context or references for the antihypertensive properties of GABA mentioned in sentences 45-47 to support the statement.

A6: Thank you very much for reviewing our paper. It is revised as in Line P2Line53-55 “In the 1980s, many reports verified that GABA inhibits the activation of the sympathetic nervous system and thereby reduces blood pressure on animals and humans.”

 

Q7: Clarify the sentence in which the decrease in blood GABA levels is associated with an increased risk of mania, bipolar disorder, anxiety, and depression (sentence 49) by adding a reference or further explanation.

A7: Thank you very much for reviewing our paper. It is revised as in P2Line57-58 “The risk of mania, bipolar disorder, anxiety, and depression is increased when the level of GABA contents in blood decreases by 10% to 15% [12].”

 

Q8:Provide references or specific studies to support the claim in sentences 51-53 that GABA supplementation through food intake effectively prevents anxiety, uneasiness, fatigue, and nervousness.

A8: Thank you very much for reviewing our paper. It is revised as in P2Line58-60 “The GABA contents in serum of the human body decrease with age, and GABA supple-mentation through food intake effectively prevents anxiety, uneasiness, fatigue, and nervousness [13,14]”

 

Q9: Consider providing references or citations for the studies mentioned in sentences 62-64 that demonstrate the potential benefits of GABA tea on renal function and life expectancy.

A9: Thank you very much for reviewing our paper. It is revised as in P2Line68-72 “Studies have demonstrated that drinking GABA tea 4.0 mg/rat per day can help maintain kidney function as it promotes salt excretion and prevents renal cell injury [18,19]. Studies of Taiwanese and Japanese have showed that GABA tea considerably prolongs the life expectancy of experimental mice [17,20,21].”

 

Q10: Revise sentence 66 for clarity: "The method of GABA tea production was introduced from Japan to Taiwan in 1994, initially using a single anaerobic fermentation process that resulted in tea leaves with a dull sour taste and odor [22]."

A10: Thank you very much for reviewing our paper. It is revised as in P2Line75-77 “The long period of anaerobic fermentation caused the tea leaves to have a boring sour taste and odor [22].”

 

Q11: Include a brief explanation or reference to support the claim in sentences 77-78 that locally produced GABA tea in Taiwan now parallels the flavor of Taiwan Oolong tea.

A11: Thank you very much for reviewing our paper. It is revised as in P2Line93-94 “The consumer acceptance test is the most appropriate way to understand how consumers feel about food and the willingness of consumers to buy it [25].”

 

Q12: Add references or citations to support the statements made about the effectiveness of GABA tea against essential hypertension in mice and humans (sentences 80-82).

A12: Thank you very much for reviewing our paper. It is revised as in P2Line95-94 ”Wang et al., found that the tea infusion brewer from GABA tea leaves that met Japa-nese commercial standards (150 mg GABA per 100 g tea leaves) was effective against es-sential hypertension in mice after 12 weeks of feeding [20]”

 

Q13: Provide more information about the limitations or challenges associated with analyzing GABA content in GABA tea (sentence 83) to highlight the significance of the study.

A13: Thank you very much for reviewing our paper. The sentence was deleted in accordance with the other reviewers' suggestion.

 

Q14: If applicable, mention the distribution of the sample types across different production areas and seasons to give a clearer picture of the sample distribution.

A14: Thank you very much for reviewing our paper. This has been discussed according to the results in Tables 3 and 4.

 

Q15: Adding additional details and references would further enhance the clarity and reproducibility of the methods.

A15: Thank you very much for reviewing our paper. The reference no 10, 27-29 were added in the section of method.

 

Q16: Consider providing information on any potential biases or limitations of the consumer acceptance test, such as demographic characteristics of the respondents or the representativeness of the sample.

Q16: Thank you very much for reviewing our paper. The process of the consumer acceptance test is supplemented as follows in P5Line188-189.

“The 101 volunteer respondents (48 male and 53 female students between the ages of 18-26 years old were invited from Hungkuang University) were participated in this study.”

 

Q17: Comments on the Quality of English Language

A17: Thank you very much for reviewing our paper. The English language within the manuscript is revised, and indicated by red text.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript analyses the physico-chemical composition and consumer acceptance of 220 commercial GABA tea samples produced in Taiwan from 2016 to 2021 and evaluates their commercialization potential. The article has a large amount of data and is relatively logical, and some of the issues previously raised have been modified. The article has been supplemented and improved but still has the following problems.

1. L23-25: Confirm the GABA content of the tea samples in the abstract section, some of which have an extra "1" before them, and the content should be "small value to large value".

2. L236-237: For substances for which abbreviations have been stated, the abbreviations are used uniformly after the substance, such as theaflavin (TF), thearubigin (TR), etc.

3. L249-250 should be “This study collected 71 GABA Black and 108 GABA Oolong tea samples from different production seasons and production areas to compare their physico-chemical constituents”. This is because the different seasons of tea are described first, followed by the different regions of tea.

4. In the "Materials and Methods" and "Results and Discussion" sections, the order of description of physical and chemical properties should be consistent.

5. The results were shown in Table 5 for GABA black tea and GABA oolong tea only, and "The results were shown in Table 5" in L304 should be presented in the following paragraph.

 

 

Comments on the Quality of English Language

Minor editing of English language required

Author Response

This manuscript analyses the physico-chemical composition and consumer acceptance of 220 commercial GABA tea samples produced in Taiwan from 2016 to 2021 and evaluates their commercialization potential. The article has a large amount of data and is relatively logical, and some of the issues previously raised have been modified. The article has been supplemented and improved but still has the following problems.

 

Q1. L23-25: Confirm the GABA content of the tea samples in the abstract section, some of which have an extra "1" before them, and the content should be "small value to large value".

A1: Thank you very much for reviewing our paper. The 1 is extra and wrong. It's been corrected and showed in P1Line22-25. The content has also been corrected to be arranged from small to large. The revised parts are shown by blue text.

 

Q2. L236-237: For substances for which abbreviations have been stated, the abbreviations are used uniformly after the substance, such as theaflavin (TF), thearubigin (TR), etc.

A2: Thank you very much for reviewing our paper. Abbreviations have been used to replace the original names in subsequent manuscript including TF 3 times, TR 3 times, TB 3 times, TP 6 times, and TC 5 times. The revised parts are shown by blue text.

 

 

Q3. L249-250 should be “This study collected 71 GABA Black and 108 GABA Oolong tea samples from different production seasons and production areas to compare their physico-chemical constituents”. This is because the different seasons of tea are described first, followed by the different regions of tea.

A3: Thank you very much for reviewing our paper. It is revised in P7Line291-292 as “71 GABA Black and 108 GABA Oolong tea samples were selected from different production seasons and production areas to compare their physico-chemical constituents.”. The revised parts are shown by blue text.

 

Q4. In the "Materials and Methods" and "Results and Discussion" sections, the order of description of physical and chemical properties should be consistent.

A4: Thank you very much for reviewing our paper. The order of the components in Materials and Methods has been corrected including “2.2.2. The theaflavin, thearubigin, and theabrownin contents”, “2.2.3. The total polyphenol contents”, and “2.2.4. The total catechin contents”. The revised parts are shown by blue text.

 

Q5. The results were shown in Table 5 for GABA black tea and GABA oolong tea only, and "The results were shown in Table 5" in L304 should be presented in the following paragraph.

A3: Thank you very much for reviewing our paper. It is presented in the following paragraph and revised in P9Line350-353 as “Because the number of GABA Black tea and GABA Oolong tea samples in these two groups is relatively large., it was further examined whether the groups of GABA Red tea and GABA Oolong tea differed in terms of physical and chemical components. The results were shown in Table 5.”

Author Response File: Author Response.pdf

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