Hydrothermal–Microwave Processing for Starch Extraction from Mexican Avocado Seeds: Operational Conditions and Characterization

Round 1

Reviewer 1 Report

The authors of this work described an optimized MAE method from Avocado seeds as agro-industrial residue in order to recover starch, which is an important biopolymer with several application and functions. Moreover a comparison with a no-isothermal mode (NO-ISO) and conventional extraction was performed.

The article is very interesting and complete in each experimental part. It shows an amount of data enough to consider MAE an attractive method for a sustainable extraction of food residue.

Anyway, before publication I suggest to heavily revise the English language that in several part is very weak.

Author Response

First, I want to thank you for the extensive corrections and comments to improve and publish this research. The English of the document was revised and improved.

Author Response File: Author Response.docx

Reviewer 2 Report

General comments

A good piece of work but may require significant review in terms of communicating the research findings in an unambiguous, easy to follow manner. I would suggest sufficient time should be taken to review and where necessary, rewrite some sections before resubmitting. Significant findings but very difficult to follow.

Sectional comments

Abstract: Line 31-35 – not clear. Consider rephrasing.

Introduction: Major revision required for the introduction – I would recommend the author should carefully review for clarity. With significant improvement, the introduction should be easy to follow.

Lines 41 – 43 – Rewrite/rephrase for grammatical correctness.

Lines 55 – 57:  Will need a reference/check the grammar.

Lines 53 - 73: I would seek the help of a native English speaker to read before resubmitting.

Lines 80 – 89: Review for clarity.

Materials and methods: Consistency of unit style (cm^-1 or 1/cm; min vs mins; 1% vs 1 %)

98: More details on the blender type.  Is the crushing time 5-10 s or min?

101: AOAC should be written in full the first time.

Results and discussion:

241: Good fit in place of adjustment

243: Separate Tables 1 and 2.

281: Need to differentiate from the right and left images.

289: ‘irreversible water absorption’ - what do you mean by this? The phrase implies the starch maintains its structural integrity after absorbing water irreversibly. Will that be correct to say there?

292: What is CONV?

307: Can you include the error bars for the plots?

350: Showing the DSC/TGA thermograms will be very useful for the visual appreciation of the differences – an important piece.

379: Enlarge Figures 4 and 5 and where possible increase the font size. Also indicate peaks and region of interests on the plots.

400: Increase the font sizes of Figures 6(a-c) axes and legends.

Conclusions:

The conclusion could be improved by being very clear on the statements of key outcomes and should also be supported by a concise summary of findings from the analytical techniques carefully linked together.

Author Response

General comments

A good piece of work but may require significant review in terms of communicating the research findings in an unambiguous, easy to follow manner. I would suggest sufficient time should be taken to review and where necessary, rewrite some sections before resubmitting. Significant findings but very difficult to follow.

The English was revised and improved and was rewrite some sentences of the document.

Sectional comments

Introduction: Major revision required for the introduction – I would recommend the author should carefully review for clarity. With significant improvement, the introduction should be easy to follow.

Improved

Lines 41 – 43 – Rewrite/rephrase for grammatical correctness.

Lines 55 – 57:  Will need a reference/check the grammar.

Lines 53 - 73: I would seek the help of a native English speaker to read before resubmitting.

Lines 80 – 89: Review for clarity.

All improved

Materials and methods:

Consistency of unit style (cm-1 or 1/cm; min vs mins; 1% vs 1 %) 

Modified

98: More details on the blender type.  Is the crushing time 5-10 s or min?

The time of blender is seconds

101: AOAC should be written in full the first time.

Added in document and referenced in references section.

Results and discussion:

243: Separate Tables 1 and 2.

Modified

281: Need to differentiate from the right and left images.

Modified

289: ‘irreversible water absorption’ - what do you mean by this? The phrase implies the starch maintains its structural integrity after absorbing water irreversibly. Will that be correct to say there?

This phrase seeks to mention that in the starch heating process (gelatinization), the starch loses the property of water absorption, and in a second gelatinization process it has a low water absorption capacity. This was verified in the starch obtained by MAE.

292: What is CONV?

Is conventional method, was added the nomenclature in document.

307: Can you include the error bars for the plots?

Added

350: Showing the DSC/TGA thermograms will be very useful for the visual appreciation of the differences – an important piece.

The authors decided that the results of the DSC and TGA are better presented in table, in order to present the exact data of each phase and at the same time reduce the number of figures in the document.

379: Enlarge Figures 4 and 5 and where possible increase the font size. Also indicate peaks and region of interests on the plots.

Modified

400: Increase the font sizes of Figures 6(a-c) axes and legends.

Modified

Conclusions:

The conclusion could be improved by being very clear on the statements of key outcomes and should also be supported by a concise summary of findings from the analytical techniques carefully linked together.

The authors consider a suitable conclusion and to repeat all results again would be a repetition of the results section and discussions.

Author Response File: Author Response.docx

Reviewer 3 Report

The work by Rafael Araujo and co-workers describes isolation of starch from avocado seeds, which are agroindustrial residue produced in large quantities. The idea of the work is interesting; however, I reccommend rejection of the manuscript as scope of work, its impact on the scientific disciplin and the quality of the manuscript presented (mainly poor English) are not sufficient for publication in Processes.

The main drawback of the method is preparation of avocado seeds for the extraction. Freeze-drying is rather expensive process and its use is not favorable in the case of cheap raw materials such as starch.

As I stated before, the idea is good; although the process needs some "rearrangement" before it would be implementable to industry.

Author Response

The main drawback of the method is preparation of avocado seeds for the extraction. Freeze-drying is rather expensive process and its use is not favorable in the case of cheap raw materials such as starch. As I stated before, the idea is good; although the process needs some "rearrangement" before it would be implementable to industry.

The authors are aware that the use of lyophilization is an expensive process on an industrial scale, being hardly viable for high-value compounds, which would not apply to starch. However, lyophilization was used to dry the seeds for two reasons, one to be able to create a homogeneous batch of avocado seed, which was not achieved using fresh seed, since great variability was obtained in the same treatments, derived from variations of starch content between seeds. The second reason was because the convection drying method decreased the starch extraction yield perhaps because the heating caused Maillard reactions on the surface of the seed pieces which created a caramel-like layer. What was sought in this experiment was to use lyophilized seeds to find the optimal conditions of extraction and then move on to the use of fresh seed, eliminating a drying process, which in current work was verified viable.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Dear authors

Thank you for replying to my comments and justifying the use of freeze-drying. I think that such justification should be briefly (2-3 sentences) included in the manuscript, apart from this I don't have any more comments.

Author Response

We have included in page 3 line 100: 

"Lyophilization was used to be able to create a homogeneous batch of avocado seed to find the optimal conditions of extraction, which was not achieved using fresh seed since great variability was obtained in the same treatments, derived from variations of starch content between seeds. on the other hand, the convection drying method decreased the starch extraction yield perhaps because the heating caused Maillard reactions on the surface of the seed pieces which created a caramel-like layer."

We have includes in Acknowledgements:

 "Thanks to Shiva and Rohit Saxena for the technical support."

Author Response File: Author Response.docx