Screening of Antioxidant Effect of Spontaneous and Bioinoculated with Gluconobacter oxydans Fermented Papaya: A Comparative Study
, Beatriz Ferreira 3, Beatriz Guedes 3,4, Daniela Moreira 3, Pablo A. García 5, Luisa Barreiros 3,6 and Patrícia Correia 2,3Round 1
Reviewer 1 Report
The work seems interesting and explores the theme of fermented papaya. The introduction is clear and exhaustive, and the conclusions are appropriate giving a view of future work to be done. Just a few comments:
L 86: The choice of the different experimental conditions should be motivated
L 119: What does the acronym AAB mean?
L 261: For a better reading, reduce the decimals in the text
Author Response
Dear Reviewer,
We appreciate the time that you have dedicated to providing your feedback on our manuscript. Please find below the answers to the performed comments and recommendations:
L 86: The choice of the different experimental conditions should be motivated
The selection of the different experimental conditions used in this study was motivated by their potential influence in the fermentation process and the properties of the obtained products, namely their antioxidant effect. The text of the manuscript was modified accordingly to better convey this idea as follows (section 2. Materials and Methods, ii. Preparation of fermented papaya extracts, line 90):
“In this study, the assays were carried out in various experimental conditions to evaluate the impact of those conditions in the fermentation process and the properties of the obtained products, including the antioxidant effect. Two major assay conditions were evaluated: Spontaneous fermentation (SF) and Fermentation with Gluconobacter oxydans (FGO). Moreover, the influence of biostimulation with glucose, the use of fresh or thawed fruit after storage by freezing, and the use of fruit in different forms (puree and pieces) were also assessed (Table 1).”
L 119: What does the acronym AAB mean?
The acronym AAB stands for acetic acid bacteria (AAB). Accordingly, its meaning and corresponding acronym AAB were added to lines 61 and 122.
L 261: For a better reading, reduce the decimals in the text
We have reduced the decimals in the text and tables for better reading. Moreover, we have performed a careful review of the text, to improve the overall quality of the manuscript and correct for possible typos and/or misspellings. All the modifications were marked up using the “Track Changes” function of MS Word.
Reviewer 2 Report
In this study the authors have carried out a study of the antioxidant activity and other general parameters of spontaneous and bioinoculated with Glu- 2 conobacter oxydans fermented papaya.
Although the study is innovative, the analyses used appear to be too few to be presented as a scientific publication. In addition, analyses that can help, such as the fermentation conditions and especially the bacteria present in the starting material, should be taken into account.
Author Response
Dear Reviewer,
We acknowledge the time you have dedicated in providing your feedback on our manuscript. We agree with you and recognize that further experimental data would be helpful. Nevertheless, the major aim of the present study was to perform an initial assessment of the potential antioxidant effect of fermented papaya products obtained using different experimental conditions and evaluate the impact of these conditions on product properties. Having this in mind, the presence of phenolic compounds and the antioxidant activity of fermented extracts were screened using different commonly applied analytical methodologies. Considering that the obtained fermented products could be used in the future as a beverage or incorporated into pharmaceuticals or cosmetic products formulations, we aimed at first evaluating whether these fermented products exhibited promising antioxidant capacity and contained any compounds of interest with health benefits (such as phenolic compounds) to, then, conduct further studies in selected conditions. The conclusion section of the manuscript considers the future work to be conducted towards a more complete study on fermented papaya production and properties (lines 333-343):
“In order to perform a rigorous and comparative evaluation of the assays, it will be needed to specify the days on which the analyses are withdrawn in future work. Future research also would need to control additional fermentation conditions, such as: the type of plant material- rotting fruit, the seeds, or even the peel can also be saved to prevent food waste; the temperature; the use of different bacteria. Furthermore, it will be useful for future studies to identify and characterize the species of bacteria present in the fermented papaya product and in the starting medium used as substrate to relate the bacterial community with the obtained compounds. It is also critical to identify and determine the phytonutrients produced as a result of fermentation that boost the increase in antioxidant activity provided by fermentation with bacteria,namely by the exact quantification of each phenolic compound. ”
Taking all of this into account, and in order to better clarify the major goal of the present work, we opted to modify the title of the manuscript to:
Screening of antioxidant effect on spontaneous and bioinoculated with Gluconobacter oxydans fermented papaya: a comparative study
The methodologies applied to determine the monitored parameters, namely pH, Brix value, reducing sugars, sodium pyruvate content, Total Phenolic Content (TPC) and antioxidant activity were selected according to the following criteria: commonly applied methodologies in laboratories worldwide and application in the analysis of beverages and fermented products. In fact, several studies focusing on fermented beverages have described the analysis of parameters using methodologies similar to ours (Jakubczyk et al., 2020) (Alderson et al., 2021). We have modified the text at the end of the Introduction section to include this information (lines 78-80):
“These parameters were evaluated using methodologies commonly applied in laboratories worldwide and previously described for the analysis of fermented products and beverages (refs. Jakubczyk et al., 2020 and Alderson et al., 2021).”
Regarding to the reviewer’s comment “In addition, analyses that can help, such as the fermentation conditions and especially the bacteria present in the starting material, should be taken into account”, we acknowledge and agree with this suggestion. In fact, the material used as substrate could be microbiologically characterized, particularly the bacterial community, to enlighten the observed processes and obtained product. This characterization can be included in future studies, and this information has been added to the Conclusion section, as follows (lines 337-340):
“Furthermore, it will be useful for future studies to identify and characterize the species of bacteria present in the fermented papaya product and in the starting medium used as substrate to relate the bacterial community with the obtained compounds.”
Regarding fermentation conditions, Reviewer 1 also raised this issue, and the text of the manuscript has been modified accordingly to better explain the rationale for the selection of the different experimental conditions tested in this study, as follows (section 2. Materials and Methods, ii. Preparation of fermented papaya extracts, line 90):
“In this study, the assays were carried out in various experimental conditions to evaluate the impact of those conditions in the fermentation process and the properties of the obtained products, including the antioxidant effect. Two major assay conditions were evaluated: Spontaneous fermentation (SF) and Fermentation with Gluconobacter oxydans (FGO). Moreover, the influence of biostimulation with glucose, the use of fresh or thawed fruit after storage by freezing, and the use of fruit in different forms (puree and pieces) were also assessed (Table 1).”
Round 2
Reviewer 2 Report
Having read the authors' comments and having seen that they have corrected and explained some of the decisions made, I consider the work accepted
