Qualitative Changes in Birch Sap after Freezing and Thawing

Round 1

Reviewer 1 Report

Dear authors

this is a nice idea for a paper, but the methods used for the analysis of data are quite poor. You have measured so much data and you only analyze them with means of descriptive statistics in Excel, and automated regressions produced by the program. In this way you can't support soundly you results.

For example, you say in discussion: "In containers of 10 liters and smaller, the quality indicators of frozen and thawed 308 birch sap do not differ from those of fresh juice or differ within the limits of error." How can you tell, when you haven't used a t-test or ANOVA? What is the significance level of your test? 

Multivariate statistics and ANOVA tests can help you improve your paper and make it scientifically and statistically sound. You should perform such analysis first, so that your paper can be published.

Thank you!

Author Response

The authors are very grateful for reviewing our manuscript and providing valuable comments and suggestions. We sincerely appreciate your professional guidance and sincerely thank you for taking the time to carefully evaluate our manuscript despite your busy schedule. We will respond to each of the issues you raised:

Point 1: This is a nice idea for a paper, but the methods used for the analysis of data are quite poor. You have measured so much data and you only analyze them with means of descriptive statistics in Excel, and automated regressions produced by the program. In this way you can't support soundly your results.

For example, you say in discussion: "In containers of 10 liters and smaller, the quality indicators of frozen and thawed birch sap do not differ from those of fresh juice or differ within the limits of error." How can you tell, when you haven't used a t-test or ANOVA? What is the significance level of your test? Multivariate statistics and ANOVA tests can help you improve your paper and make it scientifically and statistically sound. You should perform such analysis first, so that your paper can be published.

Response 1: Thank you very much for your valuable observations. We updated the manuscript by removing the regression equations and figures 14-18. The results were transferred to table 2, where we also presented the one-way analysis of variance (ANOVA) with post hoc Tukey's HSD test for statistical analysis.

Reviewer 2 Report

Please see attached file.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments

The authors are very grateful for reviewing our manuscript and providing valuable comments and suggestions. We sincerely appreciate your professional guidance and sincerely thank you for taking the time to carefully evaluate our manuscript despite your busy schedule. We will respond to each of the issues you raised:

Point 1: The work is clearly exposed, and English is very fluid and easy to understand. As regards the content, there are some suggestions I wish to comment in order to improve the value of the manuscript:

- If we consider the title of the manuscript, the main objective of the study is not accomplished

because we are carefully reported with the characteristics of the birch sap after freezing and thawing, but we do not know the changes in relation to fresh sap because the characteristics of fresh birch  sap are not provided to the reader. The properties of fresh product should be therefore shown for comparisons.

Response 1: Thank you for your suggestion. Considering your comment, we have added fresh birch sap characteristics to the article (Table 1).

Point 2: The authors have decided to yield their results by means of graphics but the presentation of descriptive statistics in tabular form (at least the mean values and standard deviations referred in lines 112-113) is also necessary, to ease other researchers to use the results.

Response 2: Thank you very much for your valuable observations. We updated the manuscript by removing the regression equations and figures 14-18. The results were 

transferred to table 2, where we also presented the one-way analysis of variance (ANOVA) with post hoc Tukey's HSD test for statistical analysis.

Point 3: line 24: Please rewrite the keywords in alphabetical order.

Response 3: Thank you, we corrected it.

Point 4: Introduction: There is a lack of bibliographical references to show the background on the topic of the manuscript (variation in properties of birch sap due to freezing). It would be an improvement to move the material in lines 118-125 to the introduction because that is not a result of the study itself.

Response 4: Thank you, we corrected it. We have added additional bibliographic references. We moved lines 118-125 from the text to the introduction.

Point 5: lines 66-68: Is it an opinion of the authors? If not, I think some supporting reference is needed. Which one is the geographical scope of the assessment?

Response 5:  Thank you very much for your valuable observations. We substantiated the statement with three literature sources:

16. Weiss, G.; Emery, M.R.; Corradini, G.; Živojinović, I. New values of non-wood forest products. Forests 2020, 11(2), 1–19.
17. Purwestri, R.C.; Hájek, M.; Šodková, M.; Jarskỳ, V. How are wood and non-wood forest products utilized in the Czech Republic? A preliminary assessment of a nationwide survey on the bioeconomy. Sustainability 2020, 12, 566.
18. Enescu, C.M. Collection and use of birch sap, a less known non-wood forest product in Romania. Sci. Pap. Ser. Manag. Econ. Eng. Agric. Rural Dev. 2017, 17, 191–194.

Point 6: Figures 3, 19 and 20: The sample size (number of dots) is small for fitting purposes. The significance level of the linear fitting should be yielded because the linear equation proposed makes no sense if there is not a significance level (usually p < 0.05).

Response 6:  Thank you for your note. We updated the manuscript by removing the regression equations and figures 14-18.

Point 7: figures 2, 3 and 4: Please use the same format for the three figures.

Response 7:  Thank you, we corrected it.

Point 8:  figure 4: the legend lettering is too small for reading.

Response 8:  Thank you, we corrected it.

Point 9:  figures 14 to 18: Please use the same format used for the figures 5 to 13.

Response 9:  Thank you, we corrected it.

Point 10:  lines 248-249: Is brightness coefficient the same as lightness and L* or not? Please use

homogeneous terminology.

Response 10:  Thank you, we corrected it. Brightness is the same as lightness and L*.

Point 11:  lines 275-277. This sentence corresponds to Material and Methods.

Response 11:  Thank you, we corrected it.

Point 12:  lines 282-283. This sentence corresponds to Material and Methods

Response 12:  Thank you, we corrected it.

Reviewer 3 Report

Title: Qualitative changes in birch sap after freezing and thawing

Author: Mingaila, et al.

General

The paper discusses birch sap (juice) as a nutrient that the authors froze and then thawed. It is not directly related to the properties of the wood or otherwise to the forest, except for the fact that birch trees grow there.

In my opinion, the article is well written and clear, but I do not think it is suitable for Forests magazine. It would be more suitable for another magazine that deals with the manipulation and processing of food and drink.

I suggest rejecting the article on the basis of its content alone rather than its quality and recommend submitting it to another magazine that deals with food and drink.

Author Response

Point 1:  The paper discusses birch sap (juice) as a nutrient that the authors froze and then thawed. It is not directly related to the properties of the wood or otherwise to the forest, except for the fact that birch trees grow there.

In my opinion, the article is well written and clear, but I do not think it is suitable for Forests magazine. It would be more suitable for another magazine that deals with the manipulation and processing of food and drink.

I suggest rejecting the article on the basis of its content alone rather than its quality and recommend submitting it to another magazine that deals with food and drink.

Response 1: Thank You for your opinion, but we do not agree with the suggestion of the respected reviewer and we do not think that the article about birch sap is not suitable for Forests journal because it does not match the topic. The section "Wood Science and Forest Products" publishes articles on non-wood products derived from forest resources, collectively described as non-timber forest products (https://www.mdpi.com/journal/forests/sections/Wood_Science). The journal Forests publishes articles about birch sap, e.g. doi:10.3390/f11040365

Reviewer 4 Report

This work aims to evaluate how the quality indicators of the birch sap change after it is frozen for long storage and then unfrozen for use. The topic is interesting for the readers. Authors should make changes and additions to the text.

1. In the introduction section Authors made "state of the art" on the basis of 12 references. It will be better addition of results of another scientists.

2. The materials and methods section is concise. This section needs more additions. Each test method should be deeply described.

3. Why Authors did not calculate ΔE parameter? In the text, it should be used "CIELab" in all places.

4. The Conclusions section is short. Authors have to add more conclusions (according to their results).

5. Authors cited 25 papers (including 7 papers prepared by P. Viškelis). Why did you cite a large amount of your own papers?

Author Response

Response to Reviewer 4 Comments

The authors are very grateful for reviewing our manuscript and providing valuable comments and suggestions. We sincerely appreciate your professional guidance and sincerely thank you for taking the time to carefully evaluate our manuscript despite your busy schedule. We will respond to each of the issues you raised:

Point 1:  This work aims to evaluate how the quality indicators of the birch sap change after it is frozen for long storage and then unfrozen for use. The topic is interesting for the readers. Authors should make changes and additions to the text.

In the introduction section Authors made "state of the art" on the basis of 12 references. It will be better addition of results of another scientists.

Response 1: Thank you. We made corrections and added more literature sources to the article, provided additional information in the introduction to make the article more informative.

Point 2:  The materials and methods section is concise. This section needs more additions. Each test method should be deeply described.

Response 2: Thank you for your valuable observations. We have provided more details on the methodology and rewritten it.

Point 3:  Why Authors did not calculate ΔE parameter? In the text, it should be used "CIELab" in all places.

Response 3: Thank you, we corrected it. We calculated ΔE and updated the manuscript by removing Figures 14–18. The results were transferred to Table 2.

Point 4:  The Conclusions section is short. Authors have to add more conclusions (according to their results).

Response 4: Thank you very much for your valuable observations. We expanded the conclusions with the obtained results and rewrote them.

Point 5:  Authors cited 25 papers (including 7 papers prepared by P. Viškelis). Why did you cite a large amount of your own papers?

Response 5: Thanks to the reviewer for the apt remark. We apologize for the disappointing oversight. We have narrowed down our articles to three.

Round 2

Reviewer 2 Report

Please see attached file

Comments for author File: Comments.pdf

Please see attached file.

Author Response

Dear Reviewers, thank you for your attention, valuable comments and time. Your comments really improve the quality of the manuscript.

 Response to Reviewer 2 Comments

The authors are very grateful for reviewing our manuscript and providing valuable comments and suggestions.

Point 1: The clean version of the manuscript is not so clean because it includes colured words, crossed out words and many error messages.

Thank you, we corrected it.

Point 2: Lines 24-25: I think it is better for the visibility of yor work to avoid using as keywords some of the terms included in the title. (I present my apologies because I have not reported this feature in my first revision.)

Thank you for your suggestion. We corrected it.

Point 3: Lines 64-65: Bilek et al. is plural. Thus, replace “states” with “state”.

Thank you, we corrected it.

Point 4: Line 90: “no or ep-isodic”. Please rewrite.

Thank you, we corrected it.

Point 5: Line 110: Replace “solids” with “solid”.

Thank you, we corrected it.

Point 6: Line 156: I suggest “Trends and relationships” instead of “Trend relations”.

Thank you for your suggestion. We corrected it.

Point 7: Line 303: Replace “Teble” with “Table”.

Thank you, we corrected it.

Point 8: Lines 345-350: All this material is repeated in the next paragraph.

Thank you, we corrected it.

Author Response File: Author Response.docx

Reviewer 3 Report

L 154 What kind of temperature sensor was used?

L284 – What conditions were in the freezer? What was the speed of circulating air?

L306 – “when the temperature is maintained« - what temperature? Ambient temperature?

Table 1. How many samples were taken for quality indicators determination?

Figure 6,7,8,9,... Draw the line representing the value of fresh sap.

L366 – “the remaining 366 ice consists of almost pure water with a pH of 7.0 or close (Figure 7).” – the values are only till 5.7 and not till 7.0 as you mention.

L584 – 598 Repeating the same paragraph.

Author Response

Response to Reviewer 3 Comments

The authors are very grateful for reviewing our manuscript and providing valuable comments and suggestions.

Point 1: L 154 What kind of temperature sensor was used?

Thank you, we corrected it in the text. The temperature of the birch sap was measured and recorded using the Omega OM-DAQPRO-5300 Portable Handheld Data Logger (Omega Engineering Inc., USA) with K-type thermocouple temperature sensors.

Point 2: L284 – What conditions were in the freezer? What was the speed of circulating air?

The freezer was maintained at a temperature of -18 ± 0.5 °C, as written in the text, line 214 (in the revised version, lines 170-171). Cold air velocity in the freezer was around 2 m/s.

Point 3: L306 – “when the temperature is maintained« - what temperature? Ambient temperature?

 The freezer was maintained at a temperature of -18 ± 0.5 °C, as written in the text, line 214 (in the revised version, lines 170-171).

Point 4: Table 1. How many samples were taken for quality indicators determination?

Chemical composition tests were performed in triplicate. Results were presented as the averages of 3 measurements with the standard deviation of the means.

Point 5: Figure 6,7,8,9,... Draw the line representing the value of fresh sap.

Thank you for your valuable feedback and suggestion to include fresh birch sap data in our graphs. We appreciate your keen interest in our work. However, after careful consideration, we have concluded that incorporating this data would not be technically correct and this could potentially lead to inaccuracies and misinterpretations.

The bottom axis of our chart represents days. The freshness of the sap is a variable that changes rapidly over time and incorporating it into our day-based chart could lead to potential misinterpretations. Including fresh birch sap data in a chart where the x-axis represents days could imply that the sap remains fresh over those days, which is not the case.

We believe that adding this data could inadvertently lead to inaccurate conclusions being drawn from our research. Therefore, we have decided to refrain from incorporating fresh birch sap data into our chart.

We hope this provides further clarity on our decision. We appreciate your understanding and are open to any further discussions or suggestions you may have.

Point 6: L366 – “the remaining 366 ice consists of almost pure water with a pH of 7.0 or close (Figure 7).” – the values are only till 5.7 and not till 7.0 as you mention.

Thank you for your comment. We have clarified the sentence.

Point 7: L584 – 598 Repeating the same paragraph.

Thank you, we corrected it.

Reviewer 4 Report

Authors correctly made changes and additions to the text. The reviewer recommend the paper for the publishing in present form.

Author Response

Response to Reviewer 4 Comments

Thank you for the positive evaluation of our work.

Sincerely, Authors