The Role of Preservatives and Multifunctionals on the Oxidation of Cosmetic O/W Emulsions

Round 1

Reviewer 1 Report

 I have carefully reviewed and in my opinion, there are several discrepancies found in this draft and it is suitable for publication in the journal in its current form. The authors need to address comments given below and then
it can be reconsidered for publication. 

 In the introduction, please corroborate the need of this review by corroborating with the previous gaps of already published literature and objectives section must be revised keeping in view the food biopreservation.

Provide specific bacteriocins names and give bacteriocin classes as Table title showing "various Bacteriocin" but no specified bacteriocins have been mentioned. 

Title and abstract lead the reader to believe that the content will support this presentation. A manuscript with this content needs to be published. However, for the proposal to be better valued, major changes are needed.

Giving more emphasis to the compounds present in colours and preservatives that will support the justifications about the effects on health, as proposed in the manuscript.

Provide future perspective and possible future research domains to explore in conclusions section 

In the introduction, please corroborate the need of this review by corroborating with the previous gaps of already published literature and objectives section must be revised keeping in view the food biopreservation. Improve the logical and contextual flow between paragraphs.

Add bacteriphagses as food bipreservatives in new subsection and make a separate table and figure in this regard.

For more analysis please follow this papers

 https://doi.org/10.1016/j.focha.2022.100019 

 doi:10.3390/v10040205 

Author Response

Thank you for the review and your helpful comments. We have completed the literature and the need for research in the manuscript and also explained the used cosmetic preservatives in more detail. Some cosmetic active ingredients are also found in foods and some processes in foods are transferable to cosmetic products. An example would be sorbic acid or potassium sorbate. Therefore, we have considered explaining the broad field of preservatives in more detail for cosmetics as well as food. However, in this manuscript, we would like to focus on cosmetics, since the special features here are the initial conditions of the matrix (lower diversity of microorganisms and metabolizable nutrients) and the shelf life requirements for the product (storage at room temperature, shelf life for many months). The aspect about using bacteriophages is very interesting, as they would presumably preserve sufficiently without affecting the product. Your provided reference was inspired us to read more about the use of bacteriophages in cosmetics. Efficacy has already been confirmed for antiseptic or antibacterial applications, which brings hope for the treatment of difficult skin problems. We see opportunities here and research in the area would be worthwhile in our opinion. However, in case of the role of chemical preservatives on oxidation of cosmetics, bacteriophages seem to be beyond the topic. We are looking forward to describe the transferability of our results to food and the use of alternatives, such as bacteriophages, in another paper. We also elaborated the conclusions and perspectives, providing implications for practice and recommendations for further work.

Reviewer 2 Report

Authors should include and explain the below points

 

1. A schematic representation of the main physical properties, compartments, and possible components of an oil-in-water (O/W) emulsion should be included.
2. The effect of interface properties on the physical stability of emulsions should be explained
3. The pH influences the charge, solubility, partitioning, redox state, and chemical stability of major actors in oxidative reactions
4. preservative efficacy should be confirmed in cosmetic formulation by a preservative efficacy test
5. Potential factors affecting oxidation rates like droplet size and charge, and iron-binding effects
6. Solubility, Preservation spectrum, and Working pH range of phenethyl alcohol, potassium sorbate, ethanol, benzyl alcohol, and glyceryl caprylate should be explained properly in the introduction
7. Rheological studies, Stability tests, Organoleptic assessments

Author Response

Thank you for your review and helpful comments. We have incorporated your points into the manuscript. The most important properties of O/W emulsions, physical stability, influences on oxidative reactions, and properties of the preservatives used have been explained in more detail. We have added to the manuscript explanations of the methods used to test the rheological stability and the effectiveness of the preservatives. We did not perform an organoleptic analysis but recommend this for future work. The background in the introduction, the research design and methods, and the results and conclusions have been revised.

Reviewer 3 Report

My report:

Manuscript ID: cosmetics-1732906

Title: The Role of Preservatives and Multifunctionals on the Oxidation of Cosmetic O/W- Emulsions

Authors: Arielle Springer, Helena Ziegler

 

Overview and general recommendation:

The study aimed to quantify the impact of preservatives or multifunctionals on the oxidation of cosmetic products that contain O/W emulsions from microbial spoilage.

Overall, I found the manuscript is well written but the method of formulations needs more details to be clearly described. The results are supported by enough references and statistical analysis. However, I ask that the authors specifically revise the numbers in the tables and on the axes in the figures.

 

Comments to the authors

1. All the numbers in the manuscript should be corrected using dots instead of commas in the case of fractions.
2. What are the formulations used in the study? The authors should mention the composition of the formulation in detail.
3. For good comparison and reliable results, it was preferred that the study be performed in comparison with the blank sample.
4. Just wondering, are this quantified oxygen consumption in the formulations enough to alter the quality, stability, and efficacy of the product during the shelf life under storage conditions?

Author Response

Thank you for the review and your helpful comments. We have adjusted the charts and tables and added a detailed table with the concentrations of the ingredients used in the formulations as recommended. We agree with you that a blank sample would have been very valuable, but have also discussed in the manuscript why a preservative-free sample would not be appropriate for this measurement due to microbial respiration. Although work was performed hygienically and the bacterial count was below the detection limit, even the growth of a few microorganisms during such a long storage period (incubation at 30 °C) could falsify the measurement. This risk of falsification of the results by microorganisms would also exist with other analytical methods, such as the measurement of the peroxide number or TBARS, the microbial activity, e.g. by enzyme-induced oxidation. Your last suggestion encouraged us to calculate more precisely how much oxygen would have been needed to cause a perceptible change in hexanal concentration. We have added this to the discussion. Further research is needed here, but these results are already very promising. We have revised the chapters as recommended, especially the methods.

Reviewer 4 Report

The manuscript deals a small but an important aspect of the cosmetic products. The authors have garnered sufficient scientific evidence to address the objectives. Appreciable work.

Author Response

Thank you for your review and your time. We are very pleased with the positive feedback and hope our data will be helpful for future work.

Round 2

Reviewer 1 Report

Authors satisfy the reviewers suggestions now it is acceptable for publications.

Reviewer 2 Report

Accept in present form