Comparison of Gelatin and Plant Proteins in the Clarification of Grape Musts Using Flotation Techniques

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

Review  

Comparison of Gelatin and Plant Proteins in the Clarification 2 of Grape Musts Using Flotation Techniques

 

General comments

This paper should not be published. The English is poor. The experimental design is flawed in that is not replicated. The terminology used should be amended. The introduction is poorly written and structured, and the manuscript lacks a conclusion section. 

 

Line-by-line comments

Line 19 (abstract). Saying things as “the best results” is vague, what do the authors mean by “best results” and relative to what ? clarify and be precise, what type of improvement was achieved and how much (20% better , ? 25 % more ? ) you see the point.

 

22. same . what is the meaning of gelatin being “better” for chardonnay ? clarify.
23. okay, here the authors should check their chemistry and use a more general term.

 Leucoanthocyanidins is not widely used. Do they mean tannins or proanthocyanindins ? if so, call them tannins throughout the paper. Otherwise the nomenclature is confusing.

Also, in line 36 the authors claim there is a link between tannin and drought tolerance and that link does not exist.

 82-86. authors should mention flotation can be carried out with air , compressed air as well, in which case is coupled with Hyperoxidation. Not all flotations are done with nitrogen.

 

93. clearing is not a good word here. Refer better to “turbidity”.

The introduction starts well, but it seems “cut” midway, I mean, there is no closing parapgraph indicating the main experiment, the hyphotesis, the expected results and how the experiment  was set. It is commonplace to end the introduction section by identifying gaps in research and explaiinnng the experiment that was conducted and under which hyphothesis. Please review the introduction and add all this.

 

The first part of materials and methods pertains to the last portion of the introduction, as a matter of fact.

 

119. the correct spelling is mL and not ml.

In table 1, what is the meaning and purpose of adding the reference or references after each of the agents ?????

 

164. yeast strain ? the same for all juices? Clarify and provide the yeast strain and provider.

What yeast strains were used ?

 

So based on table 2, that means the experiment was not replicated ? meaning after flotation only one tank of each variant (4 tanks total) were set ? in reality, this experiment should have 24 tanks, that is 2 varieties x 4 treatments x 3 replicates = 24 tanks.  Was this the case ? it seems as though it was NOT the case and then the experiment is not properly replicated.

 

204-211. this is not a formally trained panel. no training happened. This is just a panel of wine professionals (seemenly) but the authors must state this is not trained panel and therefore there are not formal descriptive sensory data produced.

 

231. what the authors refer as full maturity is full maturity for their conditions. A juice with 165 g/L residual sugar is about 17 Brix and that is definitely unripe for chardonnay. Clarify and correct this.
232. “is observed”. Results should be presented in past tense “it was observed” apply this to the whole manuscript.

Table 4. the results of the leucoanthocyanindis are very very very dubious. It is unclear what these mean. They can’t be tannins (a chardonnay juice can’t have that much tannin). Catechin numbers seem really really inflated too. The authors should check the bibliography. Only TP numbers seem right, but a clear white juice can’t never have 809 mg/L of tannin and 792 mg/L of catechin.  This is just wrong and it has to be eliminated or changed for another measurement.

 

252-265. this is flotation with nitrogen, not with air. Therefore no hyperoxidation took place and one should not expect large removal of phenolics, which is what table 5 and 6 shows, minimal removal of phenolics. Which makes sense.

Again, my point is about including another treatment in which flotation is coupled with hyperoxidation, that is, flotation occurs with air and not nitrogen.

 

258. please DO NOT (do not) use the term “leucoanthocyanidin”. No one would understand what do you mean by that. I think the authors mean tannin or proanthocyanindins and they should use those terms. Please. Correct in the whole manuscript.

 

267. again, please present and discuss the results in past tense, that is, say “showed” instead of “show”.

 

296. please do not say “cleaning” the word you should use is “clarification”.

 

305-307. as I said before, this is a simple experiment with results that have been seeing and obtained elsewhere. It would have been more meaningful to conduct a flotation experiment using air (and hyperoxydation) as well as the nitrogen flotation treatment. If the authors suspected phenolics, why don’t they use hyperoxygenation ? this is the million dollar question here and the authors must address it.

318. I do not know Hungary, but is is safe to claim that dry and warm vintages always result in wines higher in phenolics ? if so, can the authors provide a reference to back up this claim?

 

The manuscript does not have a conclusion section.

 

 

 

Comments on the Quality of English Language

very poor English 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article entitled “Comparison of Gelatin and Plant Proteins in the Clarification of Grape Musts Using Flotation Techniques”, submitted to the journal presents a large-scale operational comparison of the efficiency of a gelatine preparation and a plant alternative (combination of plant protein - pea - and chitin-glucan) in the flotation clarification of musts of two wine varieties. Changes in basic analytes (sugars, acids, pH, YAN), phenolic compounds (TP, leucoanthocyanins, catechins) and sensory profile of young wines are monitored. This experiment builds on the authors' previous work. Additionally, 7 different "processing aids" were tested in the laboratory for clarifying effect during static sedimentation. The manuscript is clearly structured and written in a language understandable to potential readers.

To clarify must and wine and reduce unwanted polyphenolic substances, a number of fining preparations with precipitation and/or sorption effects are used. In the past, these were mainly proteins of animal origin; for many years, plant protein preparations, especially legumes, have been tested. Another topic of interest is the use of synthetic filtration and sorption polymers that mimic proteins, such as PVPP. Since different preparations affect the chemical and sensory profile of wine differently, depending on the nature of the raw material and the desired result, research into the effects of different sorbents on wine quality is constantly relevant and may provide new practical insights in this field.

The contribution is particularly evident in the practical comparison of two commonly available flotation variants under high-capacity conditions, along with the corresponding analytical and sensory evaluations. The study has two limitations: only one test of two varieties from a single vintage was performed, and some of the conclusions are variety- and vintage-specific. Thus, the study's generalizability is limited. The manuscript provides a practical comparison of the efficacy of gelatin and plant-based alternatives in flotating musts, meaningfully integrating chemistry and sensory science. However, major methodological and presentation additions are required to clearly support the conclusions.

 

I have the following comments:

1. In the introduction, I recommend shortening the historical passages and strengthening the motivation for the combination of "pea protein + chitin-glucan."
2. The methodology should describe the origin of the preparations—gelatin, phytoprotein, and chitin-glucan (as well as other agents used), the manufacturer, and the composition. It would be appropriate to state the active protein content (%, or g/hl).
3. For the main factorial problem (2 varieties × 2 flotation agents), a two-factor ANOVA is missing (a mixed ANOVA with "batch/replication" as a random effect would also be appropriate). The use of only "one-way ANOVA + Tukey" is methodologically weak given the variety×agent interactions.
4. Tables 5 and 6 show negative/0 removal values (e.g., TP, YAN for CH Pea), which the authors attribute to measurement error. It would be appropriate to indicate confidence intervals, effect sizes, and the procedure for handling values <0 (truncation to 0?).
5. In the methodology, YAN is expressed in mg valine/L, while elsewhere mg/L YAN (usually mg N/L) is implicitly used. It is necessary to standardize the units.
6. Turbidity after flotation – NTU after treatment is missing (only from sedimentation tests). NTU/FTU is a key output for clarification efficiency – please add and discuss.
7. Sensory analysis – the panel, randomization, and replication need to be described in detail. A scale of 1–10 is used, but there is no statistical evaluation in Fig. 1.
8. It would be necessary to add fermentation kinetics (time to completion of fermentation, max. temperature, volatile acids) to make it clear that differences in YAN did not lead to technical problems.
9. 14 of the 36 references ( 20 - 33) refer to websites associated with the company (Erbslöh). The results should be discussed with references to other, scientific publications. It would be useful to extend the discussion with a more solid mechanistic explanation of the differences (pH, phenolic composition, macromolecule-tannin interactions, chitosan/chitin-glucan vs. gelatin), with actual citations.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Since the authors have satisfactorily answered my questions and responded to my comments with changes in the text, I have no further comments and wish the authors every success in their future work.

Author Response

Dear Rewiever,

We appreciate your efforts in reviewing our manuscript.

Thank you for your recommendation.

The Authors