Impact of Lactic Acid Bacteria on Sour India Pale Ale (IPA) Fermentation: Growth Dynamics, Acidification, and Flavor Modulation
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsAbstract must be curtailed for clarity of your research work.
What was the objective of this work except knowing the fermentation performance/flavour contribution of different Ale ? Why did you choose this topic ? What if the process parameters are changed. I think this should have been the research content since LB relies on pH, temperature and presence of nutrient. I think you must focus on the qualitative aspect of your research theme. I did not see any measurement and precision level in your experimental work except the name of the instruments. It is better to provide the precision of instrument you have used for your experimental task. Comparison must also be there.
Author Response
Comments 1: Abstract must be curtailed for clarity of your research work.
What was the objective of this work except knowing the fermentation performance/flavour contribution of different Ale? Why did you choose this topic? What if the process parameters are changed? I think this should have been the research content since LB relies on pH, temperature and presence of nutrient. I think you must focus on the qualitative aspect of your research theme. I did not see any measurement and precision level in your experimental work except the name of the instruments. It is better to provide the precision of instrument you have used for your experimental task. Comparison must also be there.
Response: The Abstract section has been revised to address the reviewer’s suggestion, with clear articulation of the study objective and rationale.
- What was the objective of this work except knowing the fermentation performance/flavour contribution of different Ale? Why did you choose this topic?
Response: At the end of Introduction section, we added the sentences as “This study aimed not only to evaluate fermentation performance and flavor contributions of different LAB strains, but also to clarify their acidification kinetics, growth stability, and strain-specific influence on volatile profiles. By doing so, we provide brewers with targeted insights for selecting suitable LAB species under controlled kettle souring conditions, which has not been systematically studied before.”
- What if the process parameters are changed? I think this should have been the research content since LB relies on pH, temperature and presence of nutrient.
Response: At the end of Results and Discussion section, we added the sentences as “While this study standardized pH, temperature, and wort composition to isolate strain-specific effects, LAB performance is strongly influenced by these parameters. Future investigations should systematically vary these process conditions to optimize souring efficiency and flavor outcomes for industrial applications.”
- I think you must focus on the qualitative aspect of your research theme.
Response: In the Results and Discussion section, we added the sentences as “In addition to quantitative differences, the qualitative nature of volatile compounds—such as the presence of floral terpenoids or buttery diacetyl precursors—highlights each strain’s unique contribution to beer style differentiation.”
- I did not see any measurement and precision level in your experimental work except the name of the instruments.
Response: In the Materials and Methods section 2.3, 2.4, and 2.5, we have added the precision details for each instrument, highlighted in red where the instruments are mentioned.
- Comparison must also be there.
Response: In Results and Discussion 3.4, we have compared the volatile compound profiles of LAB-acidified beers with those of the control (non-soured) beer. In the Conclusion, we have a paragraph summarizing strains-specific characteristics, noting that P. pentosaceus contributes to fruit-forward beers, L. paracasei produces intense sourness, and L. mesenteroides results in mild, more balanced styles. In addition, the PCA analysis and tables further illustrate these comparisons.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis research paper titled “Impact of Lactic Acid Bacteria on Sour India Pale Ale (IPA) Fermentation: Growth Dynamics, Acidification, and Flavor Modulation” (fermentation-3818538) evaluated the impact of three lactic acid bacteria (LAB) species—Lacticaseibacillus paracasei, Pediococcus pentosaceus, and Leuconostoc mesenteroides—on sour beer fermentation, focusing on growth characteristics, acidification, and volatile compound profiles. The authors found the potential application of P. pentosaceus in fruit-forward sour beers, L. paracasei in bold sour styles, and L. mesenteroides in more subtle, well-balanced profiles, which can provide brewers with targeted options for flavor differentiation in craft beer production. This is an interesting study. However, the current version still needs revisions. Here are some of my suggestions:
In line 12, “The” should be added before “study,” and the author should check the grammar throughout the text for similar issues.
Lines 15–18 lack information on the experimental design, such as grouping and replication, which are important details that the author should supplement.
Why is the font size of L. paracasei larger in line 26? I found that the inconsistency in font size is particularly evident in sections 3 Results and Discussion, for example, lines 204–206. In line 33, “lactic acid bacteria” has already appeared in the title and should be replaced with other keywords to expand the search scope of this paper. The term “craft beer production” could be included in the keywords section, and the keywords should be arranged in alphabetical order.
In line 115, “2.2.16. S rDNA” should be written as “2.2. 16S rRNA,” and corresponding changes should be made in other places.
In line 204, could the craft beer company be specified?
In line 238, Figure 2 has six lines that are not very intuitive. It is suggested that one color be used for one type of index (e.g., OD600), and different groups can be distinguished by the shape of the icons.
In line 266, it is recommended that Table 1 list the P-values and SEM, while the plus-minus signs after the averages can be omitted for more concise data presentation. What does “NA” in the table mean? Is it the same as “ND” in Table 2?
In line 292, the data fluctuation of isoamyl acetate in Table 2 is large. Is this due to the low number of replicates in each group? In fact, the differences between groups are already significant, and the deviation value, such as that of P. pentosaceus, has exceeded 50% of the average.
What is the purpose of the references cited in lines 298–302?
The conclusion in line 374 should be condensed into one paragraph, or at most two paragraphs, with the limitations of this study placed in a separate paragraph or at the end of the discussion.
Do the funding grants in lines 397–399 have corresponding numbers?
The reference list in line 403 does not follow the journal’s requirements. Some information is incomplete, for example, references 33 and 34 in lines 482–485 lack DOIs.
Comments on the Quality of English LanguageIt is suggested that the author check the grammar of the whole text.
Author Response
This research paper titled “Impact of Lactic Acid Bacteria on Sour India Pale Ale (IPA) Fermentation: Growth Dynamics, Acidification, and Flavor Modulation” (fermentation-3818538) evaluated the impact of three lactic acid bacteria (LAB) species—Lacticaseibacillus paracasei, Pediococcus pentosaceus, and Leuconostoc mesenteroides—on sour beer fermentation, focusing on growth characteristics, acidification, and volatile compound profiles. The authors found the potential application of P. pentosaceus in fruit-forward sour beers, L. paracasei in bold sour styles, and L. mesenteroides in more subtle, well-balanced profiles, which can provide brewers with targeted options for flavor differentiation in craft beer production. This is an interesting study. However, the current version still needs revisions. Here are some of my suggestions:
In line 12, “The” should be added before “study,” and the author should check the grammar throughout the text for similar issues.
Response: We thank the reviewer for the pointing out. We have revised the abstract and rechecked the entire manuscript to correct similar grammatical issue.
Lines 15–18 lack information on the experimental design, such as grouping and replication, which are important details that the author should supplement.
Response: The abstract has been revised.
Why is the font size of L. paracasei larger in line 26? I found that the inconsistency in font size is particularly evident in sections 3 Results and Discussion, for example, lines 204–206. In line 33, “lactic acid bacteria” has already appeared in the title and should be replaced with other keywords to expand the search scope of this paper. The term “craft beer production” could be included in the keywords section, and the keywords should be arranged in alphabetical order.
Response: The font size of L. paracasei in line 26 has been corrected, and we have checked the entire manuscript to ensure consistency in the font formatting, particularly in the Results and Discussion section. In addition, the keywords have been revised: “lactic acid bacteria” was replaced to “LAB”, “Craft beer production” “Fermentation” were added, and all keywords are now arranged in alphabetical order.
In line 115, “2.2.16. S rDNA” should be written as “2.2. 16S rRNA,” and corresponding changes should be made in other places.
Response: This has been corrected to “2.2 16S rRNA”, and the same correction has been applied consistently throughout the manuscript.
In line 204, could the craft beer company be specified?
Response: Yes, the craft beer company has now been specified.
In line 238, Figure 2 has six lines that are not very intuitive. It is suggested that one color be used for one type of index (e.g., OD600), and different groups can be distinguished by the shape of the icons.
Response: Yes, Figure 2 has been modified according to the reviewer’s suggestion, with one color assigned to each index and different groups distinguished by icon shapes to improve clarity.
In line 266, it is recommended that Table 1 list the P-values and SEM, while the plus-minus signs after the averages can be omitted for more concise data presentation. What does “NA” in the table mean? Is it the same as “ND” in Table 2?
Response: The revisions have been made as suggested in Table 1. “NA" has been clarified to indicate that the data were not available, as the control sample did not undergo souring and therefore values for pitching rate and kettle-soured pH could not be obtained.
In line 292, the data fluctuation of isoamyl acetate in Table 2 is large. Is this due to the low number of replicates in each group? In fact, the differences between groups are already significant, and the deviation value, such as that of P. pentosaceus, has exceeded 50% of the average.
Response: We thank the reviewer for this observation. The large deviation in isoamyl acetate values reflects natural variability among biological replicates rather than a low number of replicates, as all experiments were conducted in triplicate (N=3, n=3).
What is the purpose of the references cited in lines 298–302?
Response: The references have been removed.
The conclusion in line 374 should be condensed into one paragraph, or at most two paragraphs, with the limitations of this study placed in a separate paragraph or at the end of the discussion.
Response: The Conclusion section has been revised and condensed into two paragraphs, with the study’s limitations placed in a separate paragraph at the end.
Do the funding grants in lines 397–399 have corresponding numbers?
Response: The grant from the Department of Education, Taiwan, does not have the corresponding funding number.
The reference list in line 403 does not follow the journal’s requirements. Some information is incomplete, for example, references 33 and 34 in lines 482–485 lack DOIs.
Response: The References section has been checked, and the formatting has been adjusted to meet the journal’s requirements. The missing DOIs has now been provided.
Reviewer 3 Report
Comments and Suggestions for AuthorsThis manuscript systematically compares the fermentation characteristics, acidification capacity and the influence of flavor substance formation of three lactic acid bacteria (LAB) species in the brewing of sour beer fermentation. The experimental design of this manuscript is reasonable, the data is rich, and it has strong practical application value, especially in the analysis of flavor substances.
But there are some problems which should be considered:
(1) The strains were donated by the enterprise, but their original source, isolation background or whether there was any patent/commercialization information were not disclosed, lacking transparency in the background of the strains.
(2) The explanations for the mechanisms of certain flavor substance changes are rather speculative, lacking direct evidence to support them. And there has been much discussion on the impact of pH on yeast metabolism, but the direct contribution of the metabolic pathway of LAB itself to flavor has not been taken into account.
(3) The abstract and conclusion sections are quite repetitive and can be further streamlined.
(4) The format of the references is not uniform, and some DOIs are missing or incorrect.
Author Response
This manuscript systematically compares the fermentation characteristics, acidification capacity and the influence of flavor substance formation of three lactic acid bacteria (LAB) species in the brewing of sour beer fermentation. The experimental design of this manuscript is reasonable, the data is rich, and it has strong practical application value, especially in the analysis of flavor substances.
But there are some problems which should be considered:
(1) The strains were donated by the enterprise, but their original source, isolation background or whether there was any patent/commercialization information were not disclosed, lacking transparency in the background of the strains.
Response: The strains were obtained from a local craft brewery, which has maintained them for several years, originally inherited from a previous owner. As the detailed isolation background and patent/commercialization information were not available, we performed morphological and molecular identification to verify their identities in this study.
(2) The explanations for the mechanisms of certain flavor substance changes are rather speculative, lacking direct evidence to support them. And there has been much discussion on the impact of pH on yeast metabolism, but the direct contribution of the metabolic pathway of LAB itself to flavor has not been taken into account.
Response: We thank the reviewer for this valuable suggestion. The explanations provided in this study were based on experimental outcomes and their potential applications for the brewing industry. We agree that the direct contribution of LAB metabolic pathways to flavor formation requires further investigation, and have noted this as an important direction for future research.
(3) The abstract and conclusion sections are quite repetitive and can be further streamlined.
Response: The Abstract and Conclusion sections have been revised and streamlined to reduce redundancy while retaining the key findings and practical implications.
(4) The format of the references is not uniform, and some DOIs are missing or incorrect.
Response: The References section has been thoroughly checked, and the formatting has been standardized to comply with the journal’s requirements. All missing DOIs have now been provided.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsIt can be considered.
