Optimization of Ultrasonic-Assisted Extraction of Antioxidants in Apple Pomace (var. Belorusskoje malinovoje) Using Response Surface Methodology: Scope and Opportunity to Develop as a Potential Feed Supplement or Feed Ingredient

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this study, the extraction of total phenolic content (TPC) and antioxidant extraction yield of apple pomace was optimized using Response Surface Methodology (RSM). The antioxidant activity of the apple pomace was determined using DPPH and ABTS assays. In addition, its nutritional composition, vitamins, minerals, fatty acids and amino acid content were determined. Although there are not obvious innovations on the methodology, it is a comprehensive study and the results are beneficial for the further study of apple pomace. Followings are some suggestions for further revisions.

1, The introduction section can be improved. For example, more information about apple pomace can be provided; the introduction of RSM can be deleted or briefly descried in the section of “2.6. Response Surface Methodology”; in reality, the RSM is not a “novel technique”.

2, The “and Evaluation of Apple Pomace As a Potential Feed Supplement or Feed Ingredient” can be deleted from the title.

3, The identification criteria of the crude material as “Belorusskoje malinovoje” can be briefly described in the “2.1. Sample selection and collection”.

4, Please explain why only using DPPH and ABTS assays?

5, Please explain why “The most favourable outcomes for TPC and DPPH analyses were attained with an extraction time of 17.5 minutes and an ultrasound-assisted extraction amplitude of 20%. For ABTS, optimal conditions were achieved with a 5-minute extraction time and 20% amplitude.” Why longer extraction time is not good for ABTS assay?

6, Some related results can be provided as supplementary material. For example, the total ion chromatograms of the LC-MS analysis of amino acid.

7, If possible, the phenolic compounds can also be analyzed and tentatively identified by LC-MS analysis.

8, The resolution of figures should be improved, especially for Figure 2.

9, There should be a space between he numeral and unit. The “minute” can be changed to “min”. The “ml” and “μl” can be changed to “mL” and “μL”, respectively.

Author Response

Dear Reviewer

Thanks for your construction suggestions and comments which were useful in upgrading the quality of this manuscript. All the suggestions have been incorporated in the revised version.

Regards

Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, this paper brings value in terms of contributing to the knowledge of Belorusskoje Malinovoje apple variety and as such has potential for publication after addressing the issues in the enclosed word document. The main requirement would be incorporating a deeper analysis of how the characteristics of the Belorusskoje Malinovoje apple variety could positively impact animal feed and dairy farms as this would not only strengthen the paper but also make it more impactful for a wider audience. More discussion on the effect of different extraction parameters on TPC, ABTS and DPPH would also be valuable. After that, the conclusions should be revised and supported more by the results and discussion.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English language is mostly fine with only minor editing required.

Author Response

Dear Reviewer

Thanks for your construction suggestions and comments which were useful in upgrading the quality of this manuscript. All the suggestions have been incorporated in the revised version.

Regards

Authors

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript deals with the evaluation of the effect of extraction from apple pomace (var. Belorusskoje malinovoje) from Estonia on the total phenolic content and antioxidant extraction yield. The sonication-assisted extraction has been successfully used and optimized using response surface methodology. This approach is one of the actively used at the moment in biotechnology and chemistry. Thus, the topic of the study presented is actual from the practical point of view.

The detailed characterization of the chemical composition and quantitative data were presented. On the other habd, the total antioxidant parameters were used for the optimization of the extraction.

The manuscript is well-presented and logically designed. Experimental section is meaningful and explained in details. Results and discussion are sufficient. Conclusions are fully supported with the data obtained.

The manuscript can be accepted to publication after minor revision.

1. There are technical errors throughout the text such as missed bracket for the references, dot at the end of the sentence, etc.

2. Section 2.11, the number of parallel measurements to be mentioned in the text.

3. Table 3, all quantitative data are presented as a single measurement results. The average value±SD or ±coverage interval to be presented. Otherwise, the reliability of the data shows are questionable.

4. Figure quality is insufficient. Figure 2 is fully unreadable. High resolution images are required.

5. Tables 4 and 5, the units for TPC, DPPH^• and ABTS^•+ is better to show in the column heading (there is enough of space). Moreover, (c) in the table 4 title to be removed.

6. Reference list, the style of many references does not correspond to the Journal requirements. Please, make corrections.

Comments on the Quality of English Language

In general, English is ok.

Author Response

Dear Reviewer

Thanks for your construction suggestions and comments which were useful in upgrading the quality of this manuscript. All the suggestions have been incorporated in the revised version.

Regards

Authors

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript may be accepted for publication after minor revisions.

1, The title should be re-considered. The “Evaluation of Apple Pomace As a Potential Feed Supplement or Feed Ingredient” cannot be realized only by chemical analysis.

2, How to identify and ensure the rude material as “Belorusskoje malinovoje” can be briefly described in the “2.1. Sample selection and collection”.

3, Please further check and revise some minor problems. For example, the “thiazoline-6-sulfonic acid ().” (line 22); the “Extraction of TPC, . and” (line 358); the title of Table 5 (line 355).

4, Please check and unify the units. For example, the “40μl” (line 220) should be changed to “40 μL”, there should be a space between the numeral and unit.

Author Response

Dear Reviewer,

We appreciate all your input which has helped us to improve the quality of this manuscript. All suggestions have been incorporated into the text. 

-Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, I find the revised version much improved. You have succesfully brought the results into context of dairy cows and improved the discussion of the extraction parameters. Minor text edits should be made:

Line 73 delete notes on the references

Line 436 both ___ and ABTS, word missing

Line 473 reference number contains letters

475 which assay

478 between what

479 which assay

484 compared to what

487 DPPH radicals

489 DPPH radicals

494 missing words.

499 missing words

508 DPPH again missing. Revise throughout the text.

line 511 same.

Comments on the Quality of English Language

Minor editing of the English grammar required.

Author Response

Dear Reviewer,

We appreciate all your input which has helped us to improve the quality of this manuscript. All suggestions have been incorporated into the text. 

-Authors

Author Response File: Author Response.pdf