Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents an interesting and timely study exploring the potential of Albizia amara leaf powder as a natural biosurfactant and emulsifying agent. The topic aligns well with the growing interest in sustainable, plant-derived surface-active materials that can replace synthetic surfactants in pharmaceutical, cosmetic, and food applications. Overall, the work is original, methodically sound, and clearly written, but certain aspects require deeper characterization and clarification before publication in a high-impact journal.

The study is well-motivated and addresses an important challenge: the search for biodegradable, eco-friendly emulsifiers derived directly from plant materials. The experimental design is straightforward and reproducible, and the authors combine surface tension measurements, emulsion stability tests, and microscopic analysis to support their conclusions. The comparison between blending and high-shear homogenization provides valuable insight into how processing parameters influence emulsion structure. The identification of a critical micelle concentration (CMC) for A. amara powder is particularly notable, as it suggests the presence of surface-active molecules, likely saponins or other glycosides. The work has strong practical relevance and represents a promising step toward low-cost biosurfactants derived from raw biomass.

Temperature effects during homogenization were not monitored, even though local heating could influence viscosity and interfacial tension. Including such complementary measurements would significantly improve the scientific depth of the work and strengthen the link between the observed macroscopic properties and the processing conditions. Additionally, a brief discussion of the potential molecular mechanisms responsible for the surface activity of A. amara extracts would make the interpretation more complete and insightful.

This is an innovative and promising contribution to the field of natural biosurfactants. The study provides valuable preliminary evidence that raw Albizia amara powder can act as an effective natural emulsifier. However, to enhance the credibility and reproducibility of the findings, the authors should complement their rheological and interfacial analyses with a more detailed discussion of processing effects and underlying mechanisms. With these improvements, the manuscript would make a strong and meaningful addition to the literature on sustainable surfactants.

Author Response

Thank you for the comments.

Please see the attached document with the replays.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The study lacks the fundamental physicochemical rigor, analytical confirmation, and mechanistic understanding expected for publication in Colloids and Interfaces. To be publishable, the authors must (1) chemically identify and quantify surface-active species, (2) use filtered extracts for surface tension and interfacial analyses, (3) provide reproducible, statistically valid emulsion stability data, and (4) substantiate claims of surfactant-like behavior with mechanistic evidence. Therefore I recommend acceptance after major revisions as noted below.

1. The central claim—that raw A. amara powder exhibits biosurfactant activity—is unsupported by any chemical identification of the active surface-active compounds. No extraction, chromatography, or spectroscopy (FTIR, NMR, GC–MS, LC–MS, or total saponin quantification) was conducted. Without such data, it is impossible to attribute the observed surface tension reduction to saponins or other amphiphilic molecules rather than to particulate or colloidal artifacts. If such analysis are not possible to be conducted, a comment regarding the purity should be included.
2. Measuring surface tension using a pendant drop tensiometer on a suspension containing undissolved plant matter introduces major experimental artifacts. The reported reduction from 57 mN m⁻¹ to 49 mN m⁻¹ is modest and could result from particulate contamination or droplet instability. No dynamic surface tension, equilibrium verification, or replicates with filtrated samples were provided. Therefore, the claim of a “critical micelle concentration” (CMC) at 0.7–0.8 % is unjustified and physically meaningless for such a heterogeneous system. Could the authors include any comment in this sense?
3. The study fails to compare AA suspensions with any reference biosurfactant or synthetic surfactant under identical conditions (e.g., SDS, Tween 20, Sapindus extract). Without these controls, it is impossible to assess the relative effectiveness of AA or to validate the methodology. Could the authors make such comparison?
4. The emulsification tests are simplistic and lack standardization. No clear oil phase composition, phase volume ratio, or droplet size evolution over time is provided. The claim that the “blender provides smaller droplets” is counterintuitive and not supported by rheological or microscopic quantification beyond qualitative images. There is no information on emulsion creaming kinetics, droplet coalescence, or ζ-potential, all of which are fundamental for understanding stability.
5. Assertions regarding sustainability and “eco-friendly potential” are speculative. No biodegradability, toxicity, or life-cycle data are provided. Such claims must be supported by quantitative environmental assessments.
6. Figures should include scale bars, axis labels, and replicate averages.

Author Response

Thank you for the comments.

Please see the attached document with the replays.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors provided sufficient arguments to justify the publication of the study. Therefore I'm in favor or its acceptance.