Spray-Dried Formulations Rich in Malvidin from Tintorera Grape Wastes: Characterization, Stability, and Storage

Round 1

Reviewer 1 Report

The propsed manuscript conatins interesning data. Is preaty well designed.

The only few comments are concering the results of  antioxidant activity of Tintorera grapes-please clarifed in the title of table 4 the aseesed material properly

Why the DPPH results are lower than in FRAP. Please explain it in Results and Disscusion section.

Why authors did not used ABTS method for measurement antioxidant activity?

Also the preparation of the extract for measurement of polihenolic compounds and antioxdant activity shoudl be added in subsection "2.6 Total Polyphenol content and Antioxidant capacity of Tintorera grapes and formulations"

Author Response

Author Response File: Author Response.docx

Reviewer 2 Report

This study is interesting and rich from an experimental point of view. The topic is suitable for the journal. However, the writing is so imprecise that it is sometimes difficult to understand the meaning of the procedure and results being described.

Line 72-75: The role of oxygen in the degradation (oxidation) of polyphenols is not mentioned,

In general, the authors do not mention the effect of humidity, nor report the samples' level of humidity.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments

Point 1: The writing is so imprecise that it is sometimes difficult to understand the meaning of the procedure and results being described.

Response 1: We sincerely thank the reviewer for his comments as well as his attached peer-review. we have considered each of its typographical corrections and they have been added throughout the text. We have also reviewed the rest of the manuscript.

Point 2: Line 72-75: The role of oxygen in the degradation (oxidation) of polyphenols is not mentioned.

Response 2: We thank to reviewer for the important comment. Effectively oxygen from environment presents an important role on the oxidation of compounds and when we mentioned degradation, we mean mainly oxidation by oxygen. Therefore a line about this has been added (146-147).

Point 3: In general, the authors do not mention the effect of humidity, nor report the samples' level of humidity.

Response 3: It is true that level of humidity was missing. At the end of 2.3 Samples preparation and spray-drying of Tintorera grape extracts, we mentioned that we had worked with controlled relative humidity. Also, now, we have added the percentage of RH (60%) (line 433).

Author Response File: Author Response.docx

Reviewer 3 Report

Comments to the Authors:

The authors of this paper present an interesting study entitled “Formulations rich in malvidin from Tintorera grape wastes:  Characterization, stability and storage”. Nevertheless, this work might be improved taking into account the following suggestions: 

• I propose you to add in the title that the formulations are been received by spray drying encapsulation methodology.
• COMMENTS:

1. I propose you to add in the abstract some quantitative relevant findings of the study.
2. In the 2.1 chemicals section are not referred all used in the study chemicals e.g. Folin Ciocalteu not reported.
3. In 2.2. section for the materials, please add the collection years. Please add the collection years.
4. The ph of the received extracts is a parameter that affects the anthocyanin stability during the spray dryer encapsulation method. Did you have measured it?
5. It will be interesting if you have investigated the polyphenolic profile of your formulations and reported them in separate columns in table 1 in order to be more clear about the effect of the spray dryer process and the carrier in the polyphenols profile of the formulations.
6. The discussion needs to improve. For example in lines 252 and 255 you have to explain (with numerical results) what reported in the studies (references 22,23 &24)  and how the presented results are in line with your results.
7. It will be interesting for the reader to be reported why you choose the spray dryer instead of the freeze-drying (use of low temperatures) encapsulation method and what are the advantages and disadvantages of the two methods.

Author Response

Response to Reviewer 3 Comments

Point 1: I propose you to add in the title that the formulations are been received by spray drying encapsulation methodology.

Response 1: We appreciate the reviewer suggestion, and the Title has been reformulated as follows: Spray dried formulations rich in malvidin from Tintorera grape wastes: Characterization, stability and storage (line 2)

Point 2: I propose you to add in the abstract some quantitative relevant findings of the study.

Response 2: Thank you for the comment. We have included in the abstract some quantitative relevant results (using 10 % maltodextrin (w:v) at 90 °C inlet temperature had a little influence on the reduction of malvidin 3-O-hex encapsulated (15 %) and presented 3.35 mg GAE g^-1 DW of total polyphenol contents, 98.62 µmol Trolox (FRAP assay) and 39.97 µmol Trolox (DPPH assay).

Point 3: In the 2.1 chemicals section are not referred all used in the study chemicals e.g. Folin Ciocalteu not reported.

Response 3: We appreciate your suggestion and in 2.1 chemicals missing used have been added.

Point 4: In 2.2. section for the materials, please add the collection years. Please add the collection years.

Response 4: Collection years (2018-2019) have been added in 2.2. section

Point 5: The ph of the received extracts is a parameter that affects the anthocyanin stability during the spray dryer encapsulation method. Did you have measured it?

Response 5: Thank you for pointing out the importance of pH. Truly pH is a parameter very important in the anthocyanin stability. For this reason, pH in the samples were monitored in the raw material (mean of pH 3.2) and the formulated (mean of pH 3.9) showing acid character. In acidic condition anthocyanins from Tintorera present more stability.

Point 6: it will be interesting if you have investigated the polyphenolic profile of your formulations and reported them in separate columns in table 1 in order to be more clear about the effect of the spray dryer process and the carrier in the polyphenols profile of the formulations.

Response 6: We greatly appreciate the suggestion. We consider that the table would be too large when adding 4 more columns (LT10, LT30, HT10 and HT30) so we have added a table as supplementary data where these values can be seen. In the text, we have pointed out the effect of maltodextrin and the spray-drying process on formulations. (Line 698-702)

Supplementary data.  Identification and quantification (mg g^-1 DW) of phenolic compounds in formulations (LT10, LT30, HT10 and HT30) by HPLC-DAD-ESI/MS

            Point 7: The discussion needs to improve. For example in lines 252 and 255 you have to explain (with numerical results) what reported in the studies (references 22,23 &24)  and how the presented results are in line with your results.

Response 7: We appreciate the reviewer’s comment and discussion have been improved. Some numerical results from other authors have been included to help us to compare our results. In 3.1 section is found

‘Other authors found values lower for quercetin 3-O-glucoside ranged from 0.0014 to 0.0335 mg g^-1 whereas for isorhamnetin 3-glucoside and syringetin 3-O-glucoside values ranged from 0.0016 to 0.0035 mg g^-1 [22] though they were not detected in this experiment.

Other researchers found values of malvidin 3-O-glucoside around 0.797 mg g^-1 malvidin 3-O-6-coumaryl-glucoside around 0.119 mg g^-1 and peonidin 3-O-glucoside around 0.614 mg g^-1 during raisining process at initial time [23]. These contents of anthocyanins were lower than indicated in our study.’

Point 8: It will be interesting for the reader to be reported why you choose the spray dryer instead of the freeze-drying (use of low temperatures) encapsulation method and what are the advantages and disadvantages of the two methods.

Response 8: Some comments have been added in the introduction to explain why spray-drying process was chosen (line 129-134). Even though, temperature process is a disadvantage compared to freeze-drying, other advantages are mentioned. The main advantage found in spray-drying compared to freeze-drying is that this process is more suitable for industrial scale-up and taking into account the large volumes of grape wastes produced by agri-food industry, the management is more handle facing spray-drying process than freeze-drying. Also, the production time of formulations is an advantage since spray-drying is a process faster.

Round 2

Reviewer 3 Report

Τhe authors follow my suggestions and in my opinion the improve revised manuscript is accepted in th present form.