Microstructural Characterization of High-Protein Dairy Powders

Round 1

Reviewer 1 Report

The authors have prepared a good manuscript but I have a few comments for them to consider, and perhaps the manuscript could be modified slightly in response to some of these queries.

General comment: dairy powder rehydration has been a very active area of research in the last few years. The authors need to more clearly state in the introduction what their paper is adding specifically to this body of work. One difficulty I have with the paper is the selection of powders. For example, rennet casein and skim milk powder are completely different materials that are rehydrated/used in completely different contexts - it is well-known that rennet casein is very different by virtue of the physical changes arising from the biochemical treatment of the casein. So what is the value in making this comparison? There have been more dedicated works focusing on some of the different categories that you are investigating (e.g., SMPs, MPCs, RCNs) and it is not apparent what your study is doing differently.

- L64: "casein forward ingredients" and "whey-protein-forward" are unusual/unconventional phrases and their meaning is not clear. Consider using a more typical phrase from the literature.

-  Results and Discussion: some of the results could benefit from a more in-depth discussion of the existing literature. For example: is there other flowability research on these kinds of powders that could be referenced and discussed in comparison? As it stands the discussion seems a bit light on detail and it is difficult to place in the context of existing knowledge.

Other than these comments I think the paper is a solid piece of work.

Author Response

Authors: All the necessary changes as suggested by reviewers have been incorporated and queries answered.  The line numbers have changed because of changes made. All the changes as instructed are tracked in the corrected manuscript. We thank all the reviewers for their constructive comments and help in improving the quality of the manuscript.

Reviewer 1

Comments and Suggestions for Authors

The authors have prepared a good manuscript but I have a few comments for them to consider, and perhaps the manuscript could be modified slightly in response to some of these queries.

General comment: dairy powder rehydration has been a very active area of research in the last few years. The authors need to more clearly state in the introduction what their paper is adding specifically to this body of work. One difficulty I have with the paper is the selection of powders. For example, rennet casein and skim milk powder are completely different materials that are rehydrated/used in completely different contexts - it is well-known that rennet casein is very different by virtue of the physical changes arising from the biochemical treatment of the casein. So what is the value in making this comparison? There have been more dedicated works focusing on some of the different categories that you are investigating (e.g., SMPs, MPCs, RCNs) and it is not apparent what your study is doing differently.

Authors: Thank you for your comment. We were just trying to compare high-protein dairy powders (doesn’t matter how they are manufactured). The literature suggests that the powders are different in functionality, and we wanted to see what the microstructure of these powders is and whether it will give researchers a clue to do further research on this. Because of these differences, rennet casein is preferred in processed cheese products manufacture whereas MPC and MCC being soluble in nature are preferred in cheese, yogurt, and beverages. It has been explained in various places in the text. We also included the word functionality in Line 81.

- L64: "casein forward ingredients" and "whey-protein-forward" are unusual/unconventional phrases and their meaning is not clear. Consider using a more typical phrase from the literature.

Authors: Thank you. The cited reference used the "casein forward ingredients" and "whey-protein-forward" however we agree with you and have made changes. (Line 64-65)

-  Results and Discussion: some of the results could benefit from a more in-depth discussion of the existing literature. For example: is there other flowability research on these kinds of powders that could be referenced and discussed in comparison? As it stands the discussion seems a bit light on detail and it is difficult to place in the context of existing knowledge.

Authors: Thank you. Added the details in (lines 233-235; lines240-252)

Other than these comments I think the paper is a solid piece of work.

Authors: We thank the reviewers for their constructive comments and help in improving the quality of the manuscript.

Reviewer 2 Report

The present manuscript reveals the microstructure of several milk-derived powders. The manuscript is well presented and the experimental design is interesting. The results are of significance, especially to the industry handling mil powders and using them as ingredients. Some points should, however, be reconsidered.

I suggest that the authors should consider changing the term "functional" to "handling" and "reconstitution" properties. Densities and flow properties are usually characterized as handling properties, while wettability and dispersibility as "reconstitution" properties. Functional properties are mainly either properties connected with nutrition (antioxidant, antimicrobial etc) or techno-functional (emulsification, gelation properties etc). This would expand to the term "functionality" as well.

The SEM images yielded interesting results. The discussion of the observations is to-the-point and in-depth. However, the authors should add some points linking the observed SEM structure with the "functional" properties section results. Therefore, a different manuscript order should be applied: begin with the SEM results and continue with the "functional" results using the SEM data for justifying the "functional properties" measurements.

Table 1 and related discussion: please add w/w to the concentrations mentioned.

Table 2: please add SD to the values

Wettability values are not presented in any Table. Please add the average and SDs of wettability to Table 2.

WMP was stored for 9 or 12 months. Line 136 and Table 3/L257 do not match.

 Please use the abbreviations of the samples throughout the manuscript, tables and figures.

Author Response

Authors: All the necessary changes as suggested by reviewers have been incorporated and queries answered.  The line numbers have changed because of changes made. All the changes as instructed are tracked in the corrected manuscript. We thank all the reviewers for their constructive comments and help in improving the quality of the manuscript.

Reviewer 2

The present manuscript reveals the microstructure of several milk-derived powders. The manuscript is well presented and the experimental design is interesting. The results are of significance, especially to the industry handling mil powders and using them as ingredients. Some points should, however, be reconsidered.

I suggest that the authors should consider changing the term "functional" to "handling" and "reconstitution" properties. Densities and flow properties are usually characterized as handling properties, while wettability and dispersibility as "reconstitution" properties. Functional properties are mainly either properties connected with nutrition (antioxidant, antimicrobial etc) or techno-functional (emulsification, gelation properties etc). This would expand to the term "functionality" as well.

 Authors: We agree with the reviewer that functionality is a broad term. Similar to that handling and reconstitution properties are also broad which we have studied in part only. Since the focus is on the microstructure of the high-protein dairy powders we modified the title to just show the microstructure as an important analysis and the other properties 9handling and reconstitution properties0 as support. Changes are made at multiple places by replacing functional properties with handling and reconstitution properties.

The SEM images yielded interesting results. The discussion of the observations is to-the-point and in-depth. However, the authors should add some points linking the observed SEM structure with the "functional" properties section results. Therefore, a different manuscript order should be applied: begin with the SEM results and continue with the "functional" results using the SEM data for justifying the "functional properties" measurements.

 Authors: As mentioned above the importance of the microstructure of high-protein dairy powders is presented and functional properties are supporting data.

Table 1 and related discussion: please add w/w to the concentrations mentioned.

Authors: Thank you. Added as instructed.

Table 2: please add SD to the values

Authors: Thank you. Added as instructed.

Wettability values are not presented in any Table. Please add the average and SDs of wettability to Table 2.

Authors: Thank you. Added as instructed. All the high-protein dairy powders were more than 300 sec and the test was terminated at 300 seconds.

WMP was stored for 9 or 12 months. Line 136 and Table 3/L257 do not match.

Authors: The WMP was stored for 12 months, and a necessary change has been made in Line 136.

 Please use the abbreviations of the samples throughout the manuscript, tables, and figures.

Authors: Thank you. Abbreviations changed in Tables and figures

Authors: We thank the reviewers for their constructive comments and help in improving the quality of the manuscript.

Round 2

Reviewer 2 Report

The manuscript is improved.