Optimization of Ultrasound-Assisted Extraction of Spent Coffee Grounds Oil Using Response Surface Methodology

Round 1

Reviewer 1 Report

Abstract: In the methodology section authors reffer to a differente version of the software Statistica. Please, verify which is the the correct version.

Pag. 11, line 343 - the temperature was fixed in which value? Please, add this infomation in the manuscript.

Pag. 12, line 368 -  Add to the text in which value the solvent contact time was fixed. 

Pag. 13, line 386 - The same comment about the values that L/S were fixed.

One of the advantages of use CCRD is the possibility of obtaining equations which can be used to predict the response according to changes in the process variables. I strongly suggest to the author to include this equations into de manuscript.

Figures and Tables

The number of the figures is wrong. Please correct this infomation.

Parecto Chart: Quality and presentation  of Pareto Chart (Figure 2) must be improved. The zero must to be inserted before the numbers and two decimal places are enough.

RSM: The X/Y axis of the RSM (Figure 2, I suppose to be Figure 3) must be corrected to shown only the range of conditions considered in the study. 

Author Response

Please see the attachment.

Best regards,

Malek Miladi

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper uses indirect sonication was performed to extract oil from SCG using n-hexane as solvent. The analysis of the effects of principal experimental process parameters was done using the design of experiments.

To my opinion this paper was well written and bibliographical data are clearly presented. Therefore, it can be considered for publication after minors corrections.

My comments to improve thare listed below:

1. There are some spelling and grammar mistakes in the manuscript. Please check and revise the manuscript carefully.

2. Line 52-53, “Among these waste streams, the brewing coffee residues are the most significant, since from 1 ton of green coffee beans results about 650 kg of SCG”, the references should be added.

3. Please standardise the writing of units in the fullarticle, mLg^-1.

4. Line 140, “using n-hexane, a non-polar solvent with a boiling point of 68°C”. Please add other advantages of n-hexane? Why was it chosen?

5. In Table 4, please check the table for references that are duplicated.

6. The latest reference for the spent coffee groundand application of ultrasound-assisted extraction should be added. You can check the following reference:

• Gu, J., Pei, W., Tang, S., Yan, F., Peng, Z., Huang, C., ... & Yong, Q. (2020). Procuring biologically active galactomannans from spent coffee ground (SCG) by autohydrolysis and enzymatic hydrolysis. International Journal of Biological Macromolecules, 149, 572-580.
• Yan, B., Chen, Z. S., Hu, Y., Yong, Q. (2021). Insight in the recent application of polyphenols from biomass. Frontiers in Bioengineering and Biotechnology, 9.753898 

Author Response

Please see the attachment.

Best regards,

Malek Miladi

Author Response File: Author Response.pdf

Reviewer 3 Report

1- The keywords must be in alphabetical order. 

2- The figure shown on page 12 in line 364 should be changed as Figure 3, not 2.

3- The paragraph on page 4 from line 181 to line 188 needs to be rewitten.

In my opinion, the data for the current study shown in table 4 can be moved to the end of the table.

Author Response

Please see the attachment.

Best regards,

Malek Miladi

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Considering that this word deals with the optimization of the process parameters for extraction of oil from SCG, it is mandatory that the authors present in the text the mathematical equations obatined from the CCRD.

Author Response

Dear respected, please see the attachment. Regards.

Author Response File: Author Response.docx