Impact of Cherries, Strawberries, Bilberries, and Cornelian Cherry Addition on the Antioxidant Activity of Yogurt
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study explores the effect of adding fruits (namely cherries, strawberries, blueberries, and cornelian cherry (Cornus mas L.)) to natural yogurts, and compares their antioxidant activity with that of commercial yogurt products. The results show a clear and significant increase in antioxidant capacity, as measured by ABTS and DPPH assays, as well as an increase in total polyphenol content (vía the Folin–Ciocalteu metod) and reducing power. Notably, yogurts enriched with cornelian cherry and blueberries stood out, suggesting these fruits could have strong functional benefits when used in fermented dairy products.
One of the strongest points of the paper is its originality. To my knowledge, this is the first time cornelian cherry has been evaluated in yogurt, which brings new and interesting data about its antioxidant potential. The study also has practical relevance: developing fruit-enriched yogurts as healthier alternatives to sugar-laden products fits well with current public health strategies aimed at reducing added sugar in the diet.
That said, there are several methodological issues that should be addressed to improve the study’s robustness. For example, the extraction protocol involved adjusting the pH to 4.6 with HCl, which may affect the stability of pH-sensitive or thermolabile antioxidant compounds. Additionally, no organic solvents like methanol or acetone were used—this is a bit surprising, as such solvents are standard when aiming to extract antioxidants of various polarities, especially non-polar ones. It would strengthen the work if the authors justified their choice of pH and tested alternative extraction methods with solvents of different polarities.
Another concern is the use of the Folin–Ciocalteu method for measuring polyphenols. While widely used, it's not specific to polyphenols and reacts with other reducing agents, potentially inflating the results. Including a more specific method like HPLC to identify and quantify individual phenolic compounds would make the findings more reliable.
As for the antioxidant assays, the paper doesn’t touch on the well-known limitations of the methods employed. DPPH, for instance, is poorly soluble in water, which might reduce its reliability in yogurt-based samples. Similarly, ABTS can react with thiols and other compounds, potentially skewing the antioxidant capacity estimates.
The study would also benefit from more detailed chemical characterization of the fruits used. For example, reporting the anthocyanin profile of blueberries or the iridoid content in cornelian cherry would help clarify which specific compounds are driving the observed antioxidant effects.
Lastly, it's unclear whether the commercial yogurts tested contained preservatives, colorants, or other additives that might influence antioxidant activity. This lack of detail weakens the comparison between commercial and natural, fruit-enhanced yogurts.
In summary, the study offers promising insights for both food science and public health, but would benefit from clearer methodological justification and a more thorough discussion of its limitations. With some refinements, it could make a valuable contribution to the literature on functional dairy products.
Author Response
Thank you for all of your valuable comments which allowed us to increase the scientific value of our paper. We corrected the paper as much as possible and we hope that our explanations shed a new light on our paper. Once again, thank you for your support. All changes inspired by your comments are highlighted in turquoise.
Comment 1: This study explores the effect of adding fruits (namely cherries, strawberries, blueberries, and cornelian cherry (Cornus mas L.)) to natural yogurts, and compares their antioxidant activity with that of commercial yogurt products. The results show a clear and significant increase in antioxidant capacity, as measured by ABTS and DPPH assays, as well as an increase in total polyphenol content (vía the Folin–Ciocalteu metod) and reducing power. Notably, yogurts enriched with cornelian cherry and blueberries stood out, suggesting these fruits could have strong functional benefits when used in fermented dairy products.
One of the strongest points of the paper is its originality. To my knowledge, this is the first time cornelian cherry has been evaluated in yogurt, which brings new and interesting data about its antioxidant potential. The study also has practical relevance: developing fruit-enriched yogurts as healthier alternatives to sugar-laden products fits well with current public health strategies aimed at reducing added sugar in the diet.
That said, there are several methodological issues that should be addressed to improve the study’s robustness. For example, the extraction protocol involved adjusting the pH to 4.6 with HCl, which may affect the stability of pH-sensitive or thermolabile antioxidant compounds. Additionally, no organic solvents like methanol or acetone were used—this is a bit surprising, as such solvents are standard when aiming to extract antioxidants of various polarities, especially non-polar ones. It would strengthen the work if the authors justified their choice of pH and tested alternative extraction methods with solvents of different polarities.
Response 1: Thank you for this valuable comment on the antioxidant extraction strategy. We are aware that the choice of extraction conditions, such as pH or the use of organic solvents, can have a significant impact on the recovery of bioactive compounds, especially those sensitive to environmental factors or characterized by low polarity. The choice of pH 4.6 resulted directly from the adopted extraction procedure described in the reference method, on which our research protocol was based. Due to the need to maintain comparability of results and method integrity, we decided not to modify this parameter in the current study. Nevertheless, we agree that the use of solvents with different polarity (e.g. methanol, ethanol, acetone, ethyl ether) can significantly increase the scope of antioxidant extraction, including lipophilic compounds (e.g. tocopherols, carotenoids). We appreciate this suggestion and believe that extending the extraction protocol to include a step using solvent mixtures with different physicochemical properties, taking into account the pH changes on the analyzed features, would be a valuable addition in future work. Such modification could allow for an even more complete characterization of the antioxidant profile of fermented milk products.
Comment 2: Another concern is the use of the Folin–Ciocalteu method for measuring polyphenols. While widely used, it's not specific to polyphenols and reacts with other reducing agents, potentially inflating the results. Including a more specific method like HPLC to identify and quantify individual phenolic compounds would make the findings more reliable.
Response 2: We are very grateful for this comment. Thanks to this, we were able to look at this problem in more depth. Partly, we refer to this in the discussion (line 370-380). Indeed, as Torres et al. (2024) emphasize, despite the growing interest in the Folin-Ciocalteu test, the vast majority of scientific publications ignore the influence of interfering substances on the determination of the total phenolic content (TPC), resulting from the presence of, for example, some amino acids, vitamins and their derivatives (e.g. ascorbic acid), inorganic ions of reducing character. In connection, the authors suggest that this method can be used as an indicator of reducing antioxidant capacity, rather than as a precise measurement of TPC. As a common problem, for example, the use of alcohol as a solvent in the reaction mixture sometimes induces the formation of a precipitate. Therefore, it is recommended to introduce the sample into an aqueous solution when possible. When the compounds to be estimated are poorly soluble in water but soluble in alcohol, the color reaction can be carried out in centrifuge tubes, and the precipitate is removed before reading the absorbance. George et al., (2005) proposed solid-phase extraction (Oasis HLB (hydrophilic-lipophilic balance)) to eliminate water-soluble reducing interferences. However, in the case of the yogurts studied, the extract obtained was purified by filtration and the reaction mixture was clear before measurement, so we consider the measured values to be reliable. Therefore, we believe that, while being aware of its limitations, the Folin-Ciocalteu test is still a useful tool due to its simplicity, low cost and high sensitivity. Your apt remark to use the HPLC method will be taken into account in in-depth studies on this topic in the future which we included in the conclusions.
- Torres, P., Osaki, S., Silveira, E., dos Santos, D. Y., & Chow, F. (2024). Comprehensive evaluation of Folin-Ciocalteu assay for total phenolic quantification in algae (Chlorophyta, Phaeophyceae, and Rhodophyta). Algal Research, 103503.
- Georgé, S., Brat, P., Alter, P., & Amiot, M. J. (2005). Rapid determination of polyphenols and vitamin C in plant-derived products. Journal of Agricultural and food chemistry, 53(5), 1370-1373.
Comment 3: As for the antioxidant assays, the paper doesn’t touch on the well-known limitations of the methods employed. DPPH, for instance, is poorly soluble in water, which might reduce its reliability in yogurt-based samples. Similarly, ABTS can react with thiols and other compounds, potentially skewing the antioxidant capacity estimates.
Response 3: Thank you for your pertinent comment on the limitations of popular methods for assessing antioxidant activity. We agree that tests such as DPPH, ABTS or RP, despite their wide application, have well-documented limitations, which have been repeatedly discussed in the literature. We refer to this in the discussion (line 370-380). Therefore, in the presented study, we adopted a strategy of using complementary tests based on different mechanisms of action. We analyzed the antioxidant capacity of the yogurt matrix using both synthetic DPPH and ABTS radicals and the RP test assessing the reducing power. The use of several methods allowed not only to minimize the limitations of individual tests, but also to obtain a broader, more multidimensional picture of the antioxidant potential of the tested samples. This approach is in line with current methodological recommendations, indicating the need to use a set of tests with different reaction mechanisms to more completely characterize the antioxidant properties of food and bioactive ingredients.
Comment 4: The study would also benefit from more detailed chemical characterization of the fruits used. For example, reporting the anthocyanin profile of blueberries or the iridoid content in cornelian cherry would help clarify which specific compounds are driving the observed antioxidant effects.
Response 4: Thank you for your comment on the characteristics of the materials used in our study. We would like to explain that the purpose of our project was to focus on evaluating the functional effects of selected yogurt extracts under specific experimental conditions. Therefore, a detailed analysis of the chemical composition, antioxidant properties, and phenolic profile of the fruits was not the main focus of our work.
Comment 5: Lastly, it's unclear whether the commercial yogurts tested contained preservatives, colorants, or other additives that might influence antioxidant activity. This lack of detail weakens the comparison between commercial and natural, fruit-enhanced yogurts.
Response 5: Thank you for your comment. Indeed, they were not described in detail in our article, which may affect the interpretation of the comparison between commercial and natural yogurts enriched with fruit. The article has been enriched with this information.
Comment 6: In summary, the study offers promising insights for both food science and public health, but would benefit from clearer methodological justification and a more thorough discussion of its limitations. With some refinements, it could make a valuable contribution to the literature on functional dairy products.
Response 6: Thank you for your detailed and valuable evaluation of our study. We also appreciate the suggestions regarding the potential of our study in the context of the literature on functional dairy products.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis study evaluated the antioxidant performance of yogurt mixed with fruits, and is a practical one that involved a number of experiments. The experimental methods and results are described in detail, and the paper is well presented except for a few points. The following are areas for improvement.
Line 84: I think the unit "/ 100g" may be correct ("29-80 mg/100 mg ....") . Please check it.
Line 215: You have mistaken the O and 0 (zero) in Na2CO3. This is a mistake and should be corrected.
Table 1 : Why is there no data on the diet yogurt without added fruit? Since you added the fruit into the diet yogurt, you should describe information on the diet yogurt before mixing.
Table 2: Since the purpose of this study was to compare commercial yogurt with fruit and yogurt with thawed fruit added, if you were going to do a t-test, shouldn't you have compared commercial yogurt with yogurt with fruit of the same fruit content?
Table 3: Why you don't list the results of the diet yogurt before adding the fruit?
Tale 4: The antioxidant performance of different fruit inclusion rates is compared, but there are some difficulties in interpreting the results (For example, DPPH of S2 (7,5), RP of S4 (10), DPPH of B2 (6), RP of B3 (6,3), DPPH of C2 (6,7)). Have you re-tested these samples to confirm the correctness of the results?
Table 5: Why you did not list the result of the diet yogurt without fruit, i.e., "Addition 0%"? Why you did not test the antioxidant activity of the fruits which were added to the diet yogurt?
Conclusion: In Introduction, you described "The aim of the study was to evaluate the antioxidant properties of natural yogurts with the addition of thawed fruits and compare their antioxidant activity with commercial yogurts containing the same fruits". The conclusion to this should be clearly stated.
Author Response
Thank you for all of your valuable comments which allowed us to increase the scientific value of our paper. We corrected the paper as much as possible and we hope that our explanations shed a new light on our paper. Once again, thank you for your support. All changes inspired by your comments are highlighted in green.
Comment 1: This study evaluated the antioxidant performance of yogurt mixed with fruits, and is a practical one that involved a number of experiments. The experimental methods and results are described in detail, and the paper is well presented except for a few points. The following are areas for improvement.
Line 84: I think the unit "/ 100g" may be correct ("29-80 mg/100 mg ....") . Please check it.
Response 1: Thank you for your attention and valuable insights. The unit "/ 100 g" in row 84 has been corrected.
Comment 2: Line 215: You have mistaken the O and 0 (zero) in Na2CO3. This is a mistake and should be corrected.
Response 2: Thank you for pointing out this mistake. We corrected the chemical formula Na₂CO₃.
Comment 3: Table 1 : Why is there no data on the diet yogurt without added fruit? Since you added the fruit into the diet yogurt, you should describe information on the diet yogurt before mixing.
Response 3: Thank you for your question. Table 1 provides data on diet yogurt without added fruit, designations N1-N7.
Comment 4: Table 2: Since the purpose of this study was to compare commercial yogurt with fruit and yogurt with thawed fruit added, if you were going to do a t-test, shouldn't you have compared commercial yogurt with yogurt with fruit of the same fruit content?
Response 4: Thank you for your valuable comment. Indeed, comparing commercial yogurt with yogurt containing thawed fruit with the same fruit content could provide more precise information. In our study, we decided to compare commercial yogurt with yogurt containing a similar addition of thawed fruit, and what more important for us, we compared yoghurts containing the same fruit addition to get knowledge how specific fruit addition affect the analyzed parameters.
Comment 5: Table 3: Why you don't list the results of the diet yogurt before adding the fruit?
Response 5: Thank you for your question. Actually, Table 3 presents results of evaluation of antioxidant activity (ABTS, DPPH, RP) of extracts from commercial natural yogurts before adding the fruit. We did not include only GAE there, because we did not see any justification for giving the GAE content expressed as galusic acid equivalent.
Comment 6: Table 4: The antioxidant performance of different fruit inclusion rates is compared, but there are some difficulties in interpreting the results (For example, DPPH of S2 (7,5), RP of S4 (10), DPPH of B2 (6), RP of B3 (6,3), DPPH of C2 (6,7)). Have you re-tested these samples to confirm the correctness of the results?
Response 6: Yes, we retested these samples to confirm the accuracy of the results in three repetitions.
Comment 7: Table 5: Why you did not list the result of the diet yogurt without fruit, i.e., "Addition 0%"?
Response 7: These data are presented in Table 3.
Comment 8: Why you did not test the antioxidant activity of the fruits which were added to the diet yogurt?
Response 8: Thank you for your question. A detailed analysis of the chemical composition, antioxidant properties, and phenolic profile of the selected fruits was not the main focus of our work and from our perspective would not give us too much information because we wanted to check how blending fresh or thawed fruits affect antioxidant activity of natural yoghurts, and answer the question whether is it worth to prepare such fresh made yogurts at home instead of buying commercial ones.
Comment 9: Conclusion: In Introduction, you described "The aim of the study was to evaluate the antioxidant properties of natural yogurts with the addition of thawed fruits and compare their antioxidant activity with commercial yogurts containing the same fruits". The conclusion to this should be clearly stated.
Response 9: Thank you for your suggestion. We added this conclusion.
Reviewer 3 Report
Comments and Suggestions for AuthorsComments for Authors
In this study, this study evaluated and compared the antioxidant properties, polyphenol content, reducing power, and bacterial counts of natural and commercial yogurts containing 3–20% thawed fruits (bilberries, cherries, strawberries). Some issues need to be addressed.
Abstract: Abstract should be more comprehensive. For example, the last three sentence could be combined. Too many conjunctions were applied. It should include a brief overview of the research topic, the problem being addressed, the methods used, the key findings, and the implications of the research.
Line 26: It is more transparent if you use alphabetical order of some of the used keywords. For example: antioxidant activity; cornelian cherry, fruit yogurt; natural yogurt; polyphenols
Introduction: line 56-57, In addition, yogurt contains beneficial bacterial cultures, …... beneficial bacterial culture should be mentioned at same place.
Line 59-64, Lines 141-142: The sentences, " The main and practically only 59 one disadvantage of many......... and reduced weight gain." is not clear. Revise it.
Line 65, I suggest using the technical word "yogurt parfait" instead of "combining yogurt with fruit".
Line 85, Clarify the sentence/study “In addition, in the fruits of cornelian cherry we find a number ….”
Line 98-99, cite the reference number instead of year. Raikos et al. (2019) …
The authors claimed that this is the first study to examine the analyzing antioxidant properties of yogurt with cornelian cherry addition. However, it should not be the novelty of this study.
Materials and Methods:
Lines: 94-95: Cite coding of raw material and location of current study and purchasing market.
Line 222, In Microbiological analysis, authors should mention the unit of countplate or colony-forming unit (CFU)
Results and discussion:
Lines 306-308, The sentences, " However, it is worth noting …... fruit addition," needs revision.
Line 322, “as means was presented” change with “as means ± (P < 0.05) was presented”.
The authors should compare the antioxidant properties of different yogurts and yogurt parfaits comprehensively.
Line 388, 407, Blassy et al. (2020) and Mena et al., (2015), cite reference number instead of years.
Conclusion: The conclusion should be restructured to reinforce the key findings and articulate the future implications of the yogurt parfait with a better understanding of antioxidant mechanisms and improve bioavailability.
Comments on the Quality of English LanguageLanguage is not satisfactory and requires extensive revision.
Author Response
Thank you for all of your valuable comments which allowed us to increase the scientific value of our paper. We corrected the paper as much as possible and we hope that our explanations shed a new light on our paper. Once again, thank you for your support. All changes inspired by your comments are highlighted in pink.
Comment 1: In this study, this study evaluated and compared the antioxidant properties, polyphenol content, reducing power, and bacterial counts of natural and commercial yogurts containing 3–20% thawed fruits (bilberries, cherries, strawberries). Some issues need to be addressed.
Abstract: Abstract should be more comprehensive. For example, the last three sentence could be combined. Too many conjunctions were applied. It should include a brief overview of the research topic, the problem being addressed, the methods used, the key findings, and the implications of the research.
Response 1: Thank you for your valuable comment. We recheck the number of words which we used in abstract and you are right we crossed the maximum number of words expected in the instruction for authors, so we shortened one of the last sentences.
Comment 2: Line 26: It is more transparent if you use alphabetical order of some of the used keywords. For example: antioxidant activity; cornelian cherry, fruit yogurt; natural yogurt; polyphenols
Response 2: Thank you for your comment. We changed the keywords to the suggested order.
Comment 3: Introduction: line 56-57, In addition, yogurt contains beneficial bacterial cultures, …... beneficial bacterial culture should be mentioned at same place.
Response 3: Thank you for your valuable comments. We gave them beneficial bacterial cultures.
Comment 4: Line 59-64, Lines 141-142: The sentences, " The main and practically only 59 one disadvantage of many......... and reduced weight gain." is not clear. Revise it.
Response 4: Thank you for your comment. We improved those sentences.
Comment 5: Line 65, I suggest using the technical word "yogurt parfait" instead of "combining yogurt with fruit".
Response 5: Thank you for your comment. We used the technical word "yogurt parfait".
Comment 6: Line 85, Clarify the sentence/study “In addition, in the fruits of cornelian cherry we find a number ….”
Line 98-99, cite the reference number instead of year. Raikos et al. (2019) …
Response 6: Thank you for your comments. We made appropriate corrections.
Comment 7: The authors claimed that this is the first study to examine the analyzing antioxidant properties of yogurt with cornelian cherry addition. However, it should not be the novelty of this study.
Response 7: Thank you for this comment. We never claimed that this is the novelty but to the best of our knowledge this is the first study to examine the analyzing antioxidant properties of yogurt with cornelian cherry addition and we believe that it's worth underlying.
Comment 8: Lines: 94-95: Cite coding of raw material and location of current study and purchasing market.
Response 8: Thank you for your comment. We made appropriate corrections.
Comment 9: Line 222, In Microbiological analysis, authors should mention the unit of countplate or colony-forming unit (CFU)
Response 9: Thank you for your comment. We've added this information to the methodology.
Comment 10: Lines 306-308, The sentences, " However, it is worth noting …... fruit addition," needs revision.
Response 10: Thank you for your comment. We corrected this sentence.
Comment 11: Line 322, “as means was presented” change with “as means ± (P < 0.05) was presented”.
Response 11: Thank you for your comment. We corrected this sentence.
Comment 12: The authors should compare the antioxidant properties of different yogurts and yogurt parfaits comprehensively.
Response 12: Thank you for your comment. We corrected Results by adding the fallowing comment: Generally speaking, this simplified analysis suggests that natural yoghurts with the addition of thawed fruit most often showed higher antioxidant activity than commercial yoghurts containing the same fruit.
Comment 13: Line 388, 407, Blassy et al. (2020) and Mena et al., (2015), cite reference number instead of years.
Response 13: Thank you for your comment. We made appropriate changes.
Comment 14: Conclusion: The conclusion should be restructured to reinforce the key findings and articulate the future implications of the yogurt parfait with a better understanding of antioxidant mechanisms and improve bioavailability.
Response 14: Thank you for your comment. We changed the conclusions reinforcing the key findings and articulate the future implications.
Comment 15: Language is not satisfactory and requires extensive revision.
Response 15: Thank you for your comments. We appreciate your observations regarding the linguistic quality of our manuscript. We have conducted a thorough analysis and editing to improve clarity, coherence, and overall readability. All linguistic changes are highlighted in yellow.
Reviewer 4 Report
Comments and Suggestions for AuthorsImpact of Cherries, Strawberries, Bilberries, and Cornelian Cherry Addition on the Antioxidant Activity of Yogurt
The study titled "Impact of Cherries, Strawberries, Bilberries, and Cornelian Cherry Addition on the Antioxidant Activity of Yogurt" investigates the effect of incorporating various fruits into commercial natural yogurt on its antioxidant activity. The research evaluates the antioxidant potential of yogurts enriched with cherries, strawberries, bilberries, and Cornelian cherries. In addition, the manuscript presents comparative data from commercially available yogurts containing the same fruits. However, the manuscript requires improvements in clarity, structure, and presentation to enhance its scientific impact and ensure better understanding of the results.
Abstract
In the abstract you have mention that you have evaluated the antioxidant properties of natural yogurts containing different percentage of thawed fruits and compared with commercial yogurts containing the same fruit, but the natural yogurt was also commercial. Improve the sentence. Additionally, improve the abstract and mention some of your results here, not just general states.
Introduction
Line 85 – here it is not clear is it part from your analysis or someone else data
Line 103 – While the manuscript emphasizes the novelty of evaluating yogurts with a variety of fruit additions, it should be noted that numerous studies have already investigated the antioxidant activity of fruit-enriched yogurts. However, the comprehensive comparison of multiple fruits within a single study, as presented here, may still offer valuable insights for the formulation of dairy products and contribute to a better understanding of their antioxidant potential in relation to both product quality and potential health benefits. The sentence should be revised, as the claim of novelty is overstated given the existence of numerous related studies.
Line 109 – There are many yogurts on the market with added fruit but the fruits present in commercial yogurts are not fresh for obvious reasons. “not fresh for obvious reasons” – can you explain what do you think with this?
Statistical analysis
The statistical analysis section requires improvement, as the results are presented in a very basic manner. More detailed and advanced statistical evaluation is needed to strengthen the validity of the findings and enhance the overall quality of the study.
Material and methods
The criteria for yogurt selection should be clearly defined. Did you consider the shelf life of the products? Were all the yogurts evaluated with the same expiration date? Additionally, were the same yogurt cultures used across all samples? Please specify the type of yogurt (e.g., set, stirred, drinkable) and provide details regarding the packaging, milk as these factors can influence the product’s antioxidant properties and overall quality.
Line 128 – the cornelian cherry fruit was frozen or fresh?
Line 133 - How was the ratio of fruit added to the yogurt determined? Please clarify the criteria or rationale used for selecting the specific quantity of fruit in the formulation.
Line 202 – 0.2 M – 0.2 mol/L
Line 215 – Na2C03 – replace with a letter
Results
Line 247 – No need for discussion here
Table 2 – Line 250 – what does it mean “for the same method” which method. The letters of significance are confusing, how do you analyze only at the same group of product or something else?
Line 260 – The statement is not accurate, as the commercial natural yogurt sample N4 shows similar characteristics to N3, with no significant differences observed between them. Therefore, the description should be reformulated to reflect this. Additionally, presenting the antioxidant activity data (ABTS, DPPH, RP) for all seven samples in a highly detailed manner may not be necessary. It would be more effective to present the results in a narrative format, summarizing the ranges and highlighting only the most relevant comparisons or significant findings.
Table 4 – Why do all the results for yogurt with added strawberry (DS) generally show lower values for ABTS, DPPH, and RP compared to the selected commercial natural yogurt (N4)? How do you explain this outcome? Additionally, the DPPH values are also lower in samples with added bilberry, cherry, and Cornelian cherry. Please provide a clear interpretation or possible explanation for these findings.
Line 298 – “same method” or same column
Table 5 – In this table are the averages values for all of the samples? Why? What would you like to say?
Line 302 – According to the table, there is no statistical significant differences between the samples, when the percentage of fruit was increased (table 5)
Line 311 – same method – same column
Line 341- title to be improved it is not clear? This is the results only with 10% fruit addition to the commercial natural yogurt?
Line 345 – 349 “Similar results were observed for bacteria of the genus Lactobacillus but this only applied to yogurts with the addition of bilberries and cherries. In the case of the addition of cornelian cherry and strawberries, significantly a smaller number of Lactobacillus bacteria was found.” - But no statistical differences with cornelian cherry and strawberry according to the table 8, the differences are only with the natural yogurt.
Discussion
The Discussion section needs significant improvement. First, it should directly address the observed lower antioxidant activity in samples with added fruit compared to the commercial natural yogurt. How substantial of a change in antioxidant activity would be expected after fruit addition and sample preparation? Additionally, the manuscript lacks data on the antioxidant activities of the individual fruits themselves—why was this not included? Providing this information would help clarify the relationship between fruit addition and the overall antioxidant capacity of the yogurt.
References
The cited references are appropriate. The reference list fulfils the Journal requirements only to be included DOI number.
Overall Recommendations
I recommend major corrections.
Comments for author File: 
Comments.pdf
Author Response
Comment 1: The study titled "Impact of Cherries, Strawberries, Bilberries, and Cornelian Cherry Addition on the Antioxidant Activity of Yogurt" investigates the effect of incorporating various fruits into commercial natural yogurt on its antioxidant activity. The research evaluates the antioxidant potential of yogurts enriched with cherries, strawberries, bilberries, and Cornelian cherries. In addition, the manuscript presents comparative data from commercially available yogurts containing the same fruits. However, the manuscript requires improvements in clarity, structure, and presentation to enhance its scientific impact and ensure better understanding of the results.
Response 1: Thank you for all of your valuable comments which allowed us to increase the scientific value of our paper. We corrected the paper as much as possible and we hope that our explanations shed a new light on our paper. Once again, thank you for your support. All changes inspired by your comments are highlighted in grey
Comment 2: In the abstract you have mention that you have evaluated the antioxidant properties of natural yogurts containing different percentage of thawed fruits and compared with commercial yogurts containing the same fruit, but the natural yogurt was also commercial. Improve the sentence. Additionally, improve the abstract and mention some of your results here, not just general states.
Response 2: Thank you for your comments. We corrected abstract.
Introduction
Comment 3: Line 85 – here it is not clear is it part from your analysis or someone else data
Response 3: Thank you for your comment. We clearly indicate the source of the following facts „Cornelian cherry is also a rich source, in particular, of potassium (about 1490 mg/ 100 g) and minerals such as zinc, manganese and iron [23].” As for this sentence, these are the results of other authors regarding the fruits of the cornelian cherry.
Comment 4: Line 103 – While the manuscript emphasizes the novelty of evaluating yogurts with a variety of fruit additions, it should be noted that numerous studies have already investigated the antioxidant activity of fruit-enriched yogurts. However, the comprehensive comparison of multiple fruits within a single study, as presented here, may still offer valuable insights for the formulation of dairy products and contribute to a better understanding of their antioxidant potential in relation to both product quality and potential health benefits. The sentence should be revised, as the claim of novelty is overstated given the existence of numerous related studies.
Response 4: Thank you for your comment. We cleared the sentence: “However, studies focusing specifically on the impact of fruit addition on the antioxidant activity and health-related properties of ready-to-eat natural yogurt remain relatively scarce”. Usually, they analyze yogurts where the fruit addition was made during the production. In this study, we focused on plain yogurts where the fruits were added. The closest term which can describe the analyzed samples is “yogurt parfait” with the difference that typical yogurt parfait contain additionally granola.
Comment 5: Line 109 – There are many yogurts on the market with added fruit but the fruits present in commercial yogurts are not fresh for obvious reasons. “not fresh for obvious reasons” – can you explain what do you think with this?
Response 5: In production practice, fruit ingredients for commercially produced yoghurts are processed, at least pasteurized, to guarantee microbiological quality. None of the commercial producers will risk the spoilage of yogurt by adding fresh fruits. We gave this explanation in the text.
Statistical analysis
Comment 6: The statistical analysis section requires improvement, as the results are presented in a very basic manner. More detailed and advanced statistical evaluation is needed to strengthen the validity of the findings and enhance the overall quality of the study.
Response 6: Thank you for this remark. We are sure that more detailed and advanced statistical evaluation is possible. We used typical statistical analysis which is usually applied in majority of these type of works. We just wanted to indicate the significance of the differences.
Material and methods
Comment 7: The criteria for yogurt selection should be clearly defined. Did you consider the shelf life of the products? Were all the yogurts evaluated with the same expiration date? Additionally, were the same yogurt cultures used across all samples? Please specify the type of yogurt (e.g., set, stirred, drinkable) and provide details regarding the packaging, milk as these factors can influence the product’s antioxidant properties and overall quality.
Response 7: Thank you for your valuable comments. We added information about the type of yogurt and raw material used by the manufacturers to produce the yogurts. As for the shelf life and expiration date we just took care of that the analyzed yogurts were within their expiration date. We totally agree that all these factors which you mentioned can affect the antioxidant properties of the analyze samples. However, we just wanted basically to analyze the properties of natural yogurts with different level of fruits and compare them to almost random (besides the same fruit addition) commercial yogurts. From our perspective very important was that we use the same plain yogurt for the preparation of diet yogurts and we use the same fruit, we just increased the content of the fruit in yogurt. The most important thing was a practical meaning of this study. Such homemade yogurt on the basis of commercial natural yogurts might be a good healthy alternative for commercial sweetened ones.
Comment 8: Line 128 – the cornelian cherry fruit was frozen or fresh?
Response 8: Thank you for your comment. We added the relevant information.
Comment 9: Line 133 - How was the ratio of fruit added to the yogurt determined? Please clarify the criteria or rationale used for selecting the specific quantity of fruit in the formulation.
Response 9: Thank you for your important comment. We gave the explanation of the chosen quantity of fruit in the formulation.
Comment 10: Line 202 – 0.2 M – 0.2 mol/L
Line 215 – Na2C03 – replace with a letter
Response 10: Thank you for your comments. We corrected these sentences.
Results
Comment 11: Line 247 – No need for discussion here
Response 11: Thank you for your comments. We moved this sentence to discussion part.
Comment 12: Table 2 – Line 250 – what does it mean “for the same method” which method. The letters of significance are confusing, how do you analyze only at the same group of product or something else?
Response 12: Thank you for your comment. We deleted the expression “for the same method” and hope that now everything is clear.
Comment 13: Line 260 – The statement is not accurate, as the commercial natural yogurt sample N4 shows similar characteristics to N3, with no significant differences observed between them. Therefore, the description should be reformulated to reflect this. Additionally, presenting the antioxidant activity data (ABTS, DPPH, RP) for all seven samples in a highly detailed manner may not be necessary. It would be more effective to present the results in a narrative format, summarizing the ranges and highlighting only the most relevant comparisons or significant findings.
Response 13: Thank you very much for your insightful observation. There was a misunderstanding and a typo when writing the text. We have corrected this fragment. As for the comment about the excessive amount of data, perhaps you're right but we preferred to present clearly and unambiguously all results to avoid any comments from reviewers that we do not show all the data
Comment 14: Table 4 – Why do all the results for yogurt with added strawberry (DS) generally show lower values for ABTS, DPPH, and RP compared to the selected commercial natural yogurt (N4)? How do you explain this outcome? Additionally, the DPPH values are also lower in samples with added bilberry, cherry, and Cornelian cherry. Please provide a clear interpretation or possible explanation for these findings.
Response 14: Thank you for this question. We added explanations in the discussion.
Comment 15: Line 298 – “same method” or same column
Line 311 – same method – same column
Response 15: Thank you for this comment. It's the same. Each column refers to different method but we changed it for increased clarity.
Comment 16: Table 5 – In this table are the averages values for all of the samples? Why? What would you like to say?
Response 16: Thank you for your questions. We explained this analyzing the results in this table. The values presented in Table 5 represent the average values for all samples in each fruit addition group. We chose to present the data in this way to simplify data interpretation, as the detailed analysis in Table 4 was complex and could be difficult to interpret unequivocally.
Comment 17: Line 302 – According to the table, there is no statistical significant differences between the samples, when the percentage of fruit was increased (table 5)
Response 17: We appreciate your careful review and the opportunity to clarify our findings. In response to your comment regarding Line 302, we acknowledge that our initial statement may have been somewhat ambiguous. For clarity, our analysis indicates that when increasing the percentage of fruit added to the yogurt samples, no statistically significant differences were observed between the samples at higher fruit levels, specifically beyond 7%. The detailed analysis presented in Table 4 was complex, and for clarity, we derived simplified mean values based on the individual fruit addition levels shown in Table 5. Our results demonstrate that increasing fruit content in the diet yogurts correlates with a significant increase (p<0.05) in antioxidant activity—measured by both DPPH and ABTS assays—as well as in reduction power and phenolic compound content.
Comment 18: Line 341- title to be improved it is not clear? This is the results only with 10% fruit addition to the commercial natural yogurt?
Response 18: That is correct. We changed the title of this table to be more clear.
Comment 19: Line 345 – 349 “Similar results were observed for bacteria of the genus Lactobacillus but this only applied to yogurts with the addition of bilberries and cherries. In the case of the addition of cornelian cherry and strawberries, significantly a smaller number of Lactobacillus bacteria was found.” - But no statistical differences with cornelian cherry and strawberry according to the table 8, the differences are only with the natural yogurt.
Response 19: Thank you for your remark. That was that what we meant. We made appropriate correction to clear the message.
Discussion
Comment 20: The Discussion section needs significant improvement. First, it should directly address the observed lower antioxidant activity in samples with added fruit compared to the commercial natural yogurt. How substantial of a change in antioxidant activity would be expected after fruit addition and sample preparation? Additionally, the manuscript lacks data on the antioxidant activities of the individual fruits themselves—why was this not included? Providing this information would help clarify the relationship between fruit addition and the overall antioxidant capacity of the yogurt.
Response 20: Thank you for your valuable comment regarding the Discussion section. We appreciate your insight and agree that addressing the observed differences in antioxidant activity is essential for a comprehensive understanding of our results. In response, we revised the Discussion.
References
Comment 21: The cited references are appropriate. The reference list fulfils the Journal requirements only to be included DOI number.
Response 21: Thank you for your remark. You inspired us to check the reference list and we found some mistakes which we corrected. According to instructions for authors, DOI numbers are not mandatory
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI have a few additional points to mention, so please consider them and make corrections if necessary.
(1) Regarding unsweetened yogurt, there are a bunch of terms like “diet yogurts” in Table 2, “diet natural yogurts” in Table 4, and "natural yogurts". What's the difference between them? If they are the same, please use consistent terminology.
(2) Is "N6" the "diet yogurt"? It needs to be clearly stated in the tables.
(3) The multiplication symbol in the formula (Line 176, Line 191) resembles the letter "x". Please check to make sure it is correct.
(4) Is there only one sample for each yogurt? Does the standard deviation represent the variation in multiple measurements, or are there multiple samples for each yogurt? Please specify the number of samples.
Author Response
Comment 1: I have a few additional points to mention, so please consider them and make corrections if necessary.
Response 1: Thank you for all of your additional comments which allowed us to increase the scientific value of our paper. All changes inspired by your comments are highlighted in green.
Comment 2: Regarding unsweetened yogurt, there are a bunch of terms like “diet yogurts” in Table 2, “diet natural yogurts” in Table 4, and "natural yogurts". What's the difference between them? If they are the same, please use consistent terminology.
Response 2: Thank you for your comments. Indeed, our article uses various terms such as "diet yogurts" (Table 2), "diet natural yogurts" (Table 4), and "natural yogurts." We agree that for consistency and clarity, we should use uniform terminology. Therefore, we made an adjustment and used the term "natural yogurts" in all references to avoid ambiguity and ensure consistent presentation of data. Thank you again for your valuable suggestion.
Comment 3: Is "N6" the "diet yogurt"? It needs to be clearly stated in the tables.
Response 3: Thank you for this comment. Yes, "N6" is a diet yogurt. We've marked this phrase in the tables. For example: „DS – natural yogurt (N6) with strawberry addition”.
Comment 4: The multiplication symbol in the formula (Line 176, Line 191) resembles the letter "x". Please check to make sure it is correct.
Response 4: Thank you for your remark. We have corrected the multiplication symbol.
Comment 5: Is there only one sample for each yogurt? Does the standard deviation represent the variation in multiple measurements, or are there multiple samples for each yogurt? Please specify the number of samples.
Response 5: Thank you for your valuable comments. In our work, we performed several independent samples for each type of yogurt, which allowed us to estimate the variability of measurements. The standard deviation shows the variability of the results obtained from these many samples for each yogurt, which enables a more reliable assessment of the parameters. The entire analysis was repeated three times.
Reviewer 4 Report
Comments and Suggestions for AuthorsI don't have any additional comments for the authors.
Author Response
Thank you for your acceptance, and again, thank you very much for all of your previous comments which allowed us to increase the scientific value of our paper.
