Ultrasound-Assisted Extraction of Betalains from Opuntia Fruit Pulp of Different Color Varieties

Round 1

Reviewer 1 Report

Dear Authors

The aim of this research is to develop an ultrasound–assisted method for the extraction of extracts enriched with betalains from a wild Opuntia specie (Opuntia dillenii (Ker Gawl.) Haw.). Four variables (%EtOH in the solvent, extraction temperature, ultrasound amplitude and cycle) have been selected by means of a Box–Behnken design. The quadratic interaction of %EtOH and the interaction of %EtOH–cycle have proven to be influential variables at 95% confidence. The optimal conditions were established at 100 mg of sample with 20 mL (60% EtOH) solvent at 20 °C at 24% amplitude and 0.2 cycle for 10 minutes. The developed method has proven its suitability and reliability with CVs lower than 5% both for repeatability and intermediate precision

 

The work is interesting and well done. However, before publication, I suggest revisions to the language

Author Response

The authors of the paper would like to thank the revision of the manuscript and the motivating comments.

Please kindly notice that the manuscript has been sent to a certified English editor before its submission to ensure good English quality.

Reviewer 2 Report

 

This research article explored the optimization of the extraction using ultrasonic-assisted extraction. Although the method itself has been established a while ago and number of authors have published similar work, the contribution of this study is the validation of the method. I tend to see good effort to test and evaluate the performance of the approach. With some improvements, I do recommend this research article. 

I have included my comments on the PDF file. 

Comments for author File: Comments.pdf

Author Response

First, the authors of the paper would like to thank the revision of the manuscript and the motivating comments. The suggestions have been useful for the improvement of the paper.

L14: “or” has been replaced by “and”.

L23: solvent composition has been clarified.

L85: a new sentence has been included to clarify the novelty of the current research and reference 29 has been added according to reviewer recommendation.

L123: 6810 g has been selected based on the previous experience of the group in similar matrices to ensure the complete separation of solid sample and supernatant but this value has not been optimized.

L229: Table 2 and Figure 2 have been modified according to the recommendations of the reviewer.

L281: A Duncan post-hoc analysis has been performed and significant differences have been indicate with different letters in the graph (Figure 3).

L296: Again a Duncan post-hoc analysis has been performed to prove the significant differences between the analysis according to the extraction time (Figure 4).

L339: Please kindly notice that the Garden variety (purple color) exhibits a higher concentration of betalains in its composition as can be detected in Table 4, consequently a higher antioxidant activity is associated with it. This is due to the high level of betalains it has, which have a high antioxidant capacity, and is reflected in the color of the fruit.

Reviewer 3 Report

It is an interesting and well-done study. I am convinced that this study concerns an important topic that will attract the readers of the journal. Abstract is consise and clearly describes the merits of the study. Introduction is well written and provides sufficient background of the study. The design of the experiment is appropriate. However, there is lack of full validation parameters. I could not find the LOD and LOQ of a proposed method. I advise to add given parameters to the results and discussion part. Moreover, as the examined matrix is very complicated and contains many different compounds that can affect the extraction it would be worth mentioning the matrix effect. Did authors check that?

Author Response

First, the authors of the paper would like to thank the revision of the manuscript and the motivating comments. The suggestions have been useful for the improvement of the paper.

The information according to LOD and LOQ was included in a new paragraph (L207-209) in the main text.

Regarding the matrix effect, we have extensive knowledge in the extraction of compounds of biological interest such as betalains, anthocyanins and phenolic compounds in general. The matrices with which we usually work (fruits, vegetables, etc.), even with the variability they have, have many characteristics in common, and when carrying out the design of experiments, the optimal extraction conditions of the compounds of interest in each study matrix are determined. We would like to add that with respect to the level of detection and quantification with which we work in these samples (UV-Vis), the matrix effect is not a determining variable when carrying out the analysis of these compounds, especially when, in addition the extraction conditions have already been optimized previously.

Round 2

Reviewer 3 Report

I can see changes made in the manuscript, in my opinion it is ready to be published.