Tensiometric and Thermodynamic Study of Aliphatic and Aromatic Amine in Aqueous D-Glucose Solutions: A Comparative Study
Round 1
Reviewer 1 Report
The manuscript is devoted to a comparative study of the effect of additions of tyramine and the amino acid taurine on the surface tension of aqueous solutions of D-glucose. The relevance of the work is related to the prevalence of these substances in food products, and the role of D-glucose as a carrier of taurine and tyramine in a living organism. An analysis of the data obtained provides unique information on intermolecular interactions at the interface of an aqueous solution. Unfortunately, this information is not clearly disclosed. The manuscript needs significant revision. The comments on the manuscript are summarized in the following points.
- The gamma and C symbols first appear in Section 2.2 and need to be explained. Likewise, all quantities in equations (5,6,8,9) must be explained.
It is necessary to indicate in the headings and captions which component the concentration and excess concentration in Fig. 2-5 and tables 1 and 2 refer to.
- Terminology.
a) The manuscript says "Surface tensions of glucose in aqueous ... solvents", p.1 onwards.
Surface tension should refer to a solution of a certain composition, not to a solute.
b) Comparing the behavior of an amino acid and an amine is of interest. But it is incorrect to classify tyramine as an amino acid. The phenolic substituent is too low in acidity to be called an acid.
с) The manuscript contains the following “The interaction of D-glucose molecules with an aqueous amino acids …are possible through repulsive forces between hydrophobic parts of the amino acids with D-glucose in presence of water molecules”, p.8.
Probably, the author has in mind the hydrophobic interaction between non-polar fragments of a solute and a co-solute, which consists in the repulsion of water molecules by them. In this case, water molecules are removed from the overlapping hydration shells into the bulk of the solvent. There is no repulsion between solute and co-solute molecules, and the hydrophobic parts of the molecules approach each other.
d) The headings of tables 4 and 5 contain: “Enthalpies, ΔH (kJ/mol) of glucose in aqueous Taurine” and “Entropies of glucose…”. Enthalpies and entropies should be referring to the process in solution.
- Figures 2-6 are of poor quality. The horizontal size is distorted.
Units of mass “Kg” in inserts in Fig.2,4 should be corrected to “kg”.
- The English in the manuscript is not good enough.
There are combinations of incompatible words:
to obtain the possible ... interactions, p.1;
physico-chemical interaction ("molecular interactions" is more suitable), p.1;
interactive behavior of amino acids, p.4;
to calculate … equation, p.6;
linear regression line equation, pp.6,7 onwards (overuse of "line" or "linear");
the intermolecular forces of glucose, p.22.
There are errors and obscure passages.
For example:
- “upon the and equations” ?, p.6;
- “the stabilization of taurine in an aqueous D-glucose media was after the cavity formations due to addition of D-glucose in aqueous media behind the surface interactions and surface energy”, p.9;
- “are occupied by amino acid taurine molecules by various intermolecular interactions leading to aggregations with availability of fewer water molecules on to the surface of interface”, p.9; etc.
Author Response
I am very thankful to Reviewers for the positive response to my Manuscript. I would like to state that necessary changes are made in revised manuscript according to reviewer’s comments.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript entitled "Physicochemical and thermodynamic study of taurine and tyramine in aqueous D-glucose solutions" focuses on interaction between taurine, tyramine and glucose in solutions. The results are interesting; however, the manuscript is not well-written and organized properly.
1. Authors need to address why this study is important. In the manuscript, the authors mentioned its applications in infant formulas, more detailed introduction is needed.
2. The introduction should be reorganized. Author should divide it into several paragraphs to address the each concept that is important in this paper.
3. In the second section "Experimental Section," the authors may need to title as "Materials and Methods." In this section, Author should describe how the experiments were conducted in details, such as temperatures, concentrations, etc. for solutions preparation.
4. In the Section 2.2, authors should explain the parameters, such as C, γ, etc. Also, authors may need introduce each physicochemical and thermodynamic parameter calculations into different sections accordingly.
5. In the results and discussion section, the first paragraph sounds more like the content for the materials and methods section.
6. Is CM as same as CMC? Also, authors need to explain more about "critical aggregation concentration" since it is the key parameter expressing the interaction between taurine, tyramine and glucose.
7. Why surface tension parameters used to evaluate taurine and tyramine with glucose are based on temperature and Log C respectively? How to compare the results if the basis are different? Also, the x-axis titles of Fig 2a and 3a are different.
8. Authors mentioned that tyramine behaves like surfactant based on the results of surface tension and cac formation. This finding needs more discussion and comparison to taurine.
9. In Table 1, footnote for each parameters and abbreviations are needed.
10. Overall, the results and discussion are nor organized and presented properly. Authors should divide it into several subsections to discuss different parameters or it is hard for readers to follow.
Authors need to improve the writing. Several long paragraphs in the manuscript including many concepts, which makes readers hard to follow the main topics of each part of the paper.
Author Response
I am very thankful to Reviewers for the positive response to my Manuscript. I would like to state that necessary changes are made in revised manuscript according to reviewer’s comments.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The revised version of the manuscript may be recommended for publication.
But minor corrections, I recommend to make.
1. The heading of section 3.1 seems incorrect. It can be removed, keeping only the text.
2. The headings to Tables 4 and 5 (as in the first version) do not indicate the process to which the terms enthalpy and entropy refer. It turned out “enthalpy of ... solution”. More correct would be "Enthalpies (entropies) of surface formation of ... solution".
Author Response
Heartfelt thanks to the reviewer for recommending my manuscript to publish. I sincerely appreciate all valuable comments and suggestions, which helped me to improve the quality of the manuscript.
Author Response File: Author Response.pdf
