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Article

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

by
Áron Pál Szövényi
1,2,
Annamária Sólyom-Leskó
2,*,
Balázs Nagy
2,
Zsuzsanna Varga
3,
Noémi Aletta Németh
2 and
Diána Ágnes Nyitrainé Sárdy
2
1
Horticulture Doctoral School, Buda Campus, Hungarian University of Agriculture and Life Sciences, Villányi Str. 29-43, 1118 Budapest, Hungary
2
Department of Oenology, Institute for Viticulture and Oenology, Buda Campus, Hungarian University of Agriculture and Life Sciences, Villányi Str. 29-43, 1118 Budapest, Hungary
3
Department of Viticulture, Institute for Viticulture and Oenology, Buda Campus, Hungarian University of Agriculture and Life Sciences, Villányi Str. 29-43, 1118 Budapest, Hungary
*
Author to whom correspondence should be addressed.
Fermentation 2025, 11(10), 569; https://doi.org/10.3390/fermentation11100569
Submission received: 13 August 2025 / Revised: 28 September 2025 / Accepted: 29 September 2025 / Published: 1 October 2025
(This article belongs to the Section Fermentation for Food and Beverages)
Browse Figure
Review Reports Versions Notes

Abstract

The study compared the effects of conventional and vegan processing aids in the clarification of must, focusing on the phenolic and sensory characteristics of must and wine. The hypothesis was that plant protein could provide results similar to those of conventional aids containing proteins of animal origin, especially in aromatic grapes, where hyperoxidation is avoided. Conducted in 2024 in Etyek-Buda, Hungary, the initial trials subjected the Irsai Olivér grape must to gravity sedimentation with various agents. Vegan processing aids, notably the combination of pea protein and chitin-glucan, showed a gentle impact on the assimilable nitrogen content and a similar reduction in turbidity to those with animal proteins. Nitrogen flotation trials compared gelatin and the vegan alternative (a combination of pea protein and chitin–glucan) in Irsai Olivér and Chardonnay must clarification. The removal of phenolic substances was monitored using the Folin–Ciocalteu method, the acid butanol assay, and the vanillin assay. In addition, nitrogen levels were evaluated before and after the flotation experiments. The plant-based processing aid effectively improved the sensory quality of Irsai Olivér. However, the gelatin-treated Chardonnay was fresher and less bitter than the vegan option, which was less balanced and more bitter with weaker aroma and flavor.

1. Introduction

Clarification and fining agents have been used extensively in various stages of winemaking. Their fundamental function is to remove undesirable elements from must or wine. These elements typically comprise molecules containing proteins, polysaccharides, tannins, and phenols in colloidal form, which can affect not only the esthetic quality (such as opacity) of the wine but also its taste and aroma [1]. Flavonoids (e.g., flavonols, flavanols, and flavandiols) can cause technological and organoleptic problems. On the one hand, they play an important role in the life of the grape plant, as they are believed to serve as an initial defense mechanism against pathogenic microorganisms, and insect pests [2] (p. 281). On the other hand, flavonoids may have a contentious influence on the sensory attributes of wines by enhancing both body and astringency [2] (p. 295), which can be reduced during the fining process by forming precipitates with proteins [3].
When clarification or fining agents are applied, these molecules aggregate and become large enough to settle under gravitational influence and can subsequently be removed via racking or filtration. Fining agents may be derived from animal proteins [4] (pp. 286–290), plant proteins [5,6], or inorganic components [7]. In recent years, there has been an increase in the prominence of plant protein-based fining agents [8].
Wines that undergo fining treatments with substances such as egg albumin are unlikely to be harmful to health as long as they are adequately filtered after the fining process [9]. The debate continues on whether residues from fining agents, such as casein, can trigger allergic reactions, including lactose or cow’s milk protein intolerance, or serve as vectors for disease transmission. Consequently, significant efforts have been made to replace animal protein-based fining agents with vegan alternatives. At the Vienna Assembly in July 2004, the International Organisation of Vine and Wine (OIV) endorsed the implementation of specific plant protein-based fining agents for use in must and wine [10]. By December 2005, the application of wheat, potato, and pea protein as processing aids received approval within the member states of the European Union [11].
These fining agents interact with wine tannins to form negatively charged hydrophobic colloids. When metal cations are added, these colloids can precipitate. This causes particle aggregation, which ultimately leads to precipitation after flocculation. Proteins that do not bind to tannins may still aggregate with suspended or colloidal particles, most of which carry a negative charge. Some proteins, such as casein, flocculate simply due to the low pH of the medium; however, tannins are necessary for complete precipitation and clarification [4] (p. 289).
To achieve a similar result to gelatin with a plant-based fining agent, a protein content of at least 80% is necessary. This restricts the use of protein isolates that contain little or no lipid or fiber [12].
One of the first studies on this topic [13] investigated the clarification of Moroccan red wines using gelatin, polyvinylpolypyrrolidone (PVPP), and pea protein. Each of these fining agents significantly decreased the levels of monomers and apparent condensed tannins. Compared to the control, the pea protein was especially effective, removing 36% more oxidized tannins. Regarding organoleptic properties, both pea protein and PVPP produced wines with better aroma and flavor than gelatin when considering astringency and bitterness. Consequently, pea protein was identified as a good alternative to gelatin in the study.
An additional clarification experiment showed a slight difference in sedimentation effects between different agents compared to controlled oxidation exposure, specifically with respect to wine aromatics such as higher alcohols. In particular, although the pea protein binds catechins to a limited extent, it removes other phenolic compounds with similar effectiveness to agents such as PVPP or chitosan [14].
The role of chitin and its derivatives and polymers (chitosan, chitin–glucan [15], etc.) in the clarification and stabilization of must or wine is also widely known [16,17]. A complex of mold or yeast origin, chitin–glucan, exhibits effective prefermentative clarification properties. The covalently bonded chitin chain and branched glucan form a network complex that helps to bind and remove various protein-based turbidity substances from the must. In addition, when combined with pea protein, a synergistic effect occurs, thus removing polyphenols, oxidized substances, and solid particles more effectively, resulting in a clearer and more stable must [18].
Several studies have demonstrated the excellent applicability of these materials in reducing colloidal turbidities [19,20]. In addition to simple sedimentation of suspended particles and stabilization, they also play a role in addressing specific problems, such as the removal of iron, heavy metals (lead, cadmium), or mycotoxin contaminants (ochratoxin A) [21,22,23]. From both environmental and food safety points of view, this solution is considerably safer compared to the use of potassium ferrocyanide, for example.
Flotation is generally seen as a way to decrease turbidity while removing floating particles from the grape must quickly. During the process, high-pressure air, oxygen, or nitrogen is introduced into the must. The bubbles elevate solid particles and oxidized materials to the surface, enabling their removal as foam. Enhancing clarification efficiency can be achieved by integrating hyperoxidation, when a high concentration of oxygen is introduced into the must, resulting in the rapid oxidation of polyphenols. Eliminating precipitated substances leads to more stable wines, which have a paler color, and possess fresher aromas [2] (p. 344).
Wines derived from musts floated with nitrogen have similar or even better sensory qualities compared to wines made from musts settled by gravity [24]. In contemporary winemaking, flotation is undeniably significant in the creation of fashionable light white wines. Even the most basic techniques that utilize compressed air effectively handle must clarification, avoiding the incorporation of dissolved oxygen that leads to unwanted oxidation [25]. Furthermore, wines produced using both clarification methods exhibit comparable levels of total polyphenols [26].
Using special clarification agents during flotation, the polyphenol content can be reduced, leading to a longer shelf life for white wine. When gas bubbling—which moves hydrophobic particles to the surface of the liquid—cannot provide enough flotation, processing aids must be used to improve the wettability of the particles [27]. The use of specific fining agents, such as proteins, gelatine, or vegetable proteins, significantly improves the flotation efficiency of musts during the initial stage of winemaking.
In an experiment with Malvasia del Lazio musts, the best clarification results were achieved using a combination of pea protein and chitin, as this was the fastest method and produced the lowest turbidity values [28]. According to the organoleptic evaluation, these wines possessed a fuller body and reduced astringency. Gelatin required more time to achieve similar turbidity results; additionally, it resulted in a higher polyphenol content. Compared to gelatin, treatment with plant protein led to a decrease in the concentration of volatile organic compounds, which reduced the strength of the aroma, especially the floral and fruity notes, as well as the green notes.
Hungary ranks among the wine-producing areas most at risk for climate change. The wineries of the country are likely to face challenges in adapting to changing conditions driven by social, economic, and physiological factors [29]. Extreme weather events, such as prolonged periods of heat and drought interspersed with sudden torrential rains, are becoming more frequent in the country [30,31]. The phenology has become noticeably (4.5 days) shorter than in previous decades [32,33]. Earlier occurrences of bud break, flowering, and harvest have been noted compared to past decades, with the harvest now taking place 11 days sooner [32]. Hungary is progressively becoming favorable for growing blue grape varieties, and it is anticipated that over time the prominence of white varieties will diminish [34].
However, the increase in extreme heat events in Hungary, along with precipitation shortages, results in a slowdown or even inhibition of photosynthesis and consequently sugar production [35]. On the other hand, efforts to attain a reduced potential alcohol level by opting for an earlier harvest often lead to unusual alterations in acid composition and pH levels [36]. After all, winemakers tend to start the harvest season significantly earlier than the traditional time, opting for August or even late July instead of the customary mid-September. This also influences phenolic maturity, leading to a deviation in the phenolic composition of both the fruit and the resulting wines from the optimal state [37,38,39]. Consequently, this frequently results in the presence of underdeveloped, astringent, and bitter phenolic substances [4] (pp. 170–174).
Wineries in Hungary must now be ready to address these wine chemistry issues, which have become a nationwide concern [40]. Traditionally, gelatin has been a well-established method for removing raw astringency. However, there is a need to investigate other viable options to address the evolving market demand for vegan wine.
Based on our earlier research [41], the primary goal of this publication was to compare the impact of vegetable proteins with that of traditional gelatin-based clarifying agents used in flotation processes. The study aimed to examine how these processing aids affect basic analysis, assimilable nitrogen content, polyphenol levels, and organoleptic properties of must and wine.
In addition, the clarifying effect of seven different processing aids was investigated during static (gravitational) sedimentation in a small-scale experiment.
Two grape varieties, Irsai Olivér and Chardonnay, that meet the requirements of both professionals and consumers in Hungary were selected for the experiments. Irsai Olivér, known for its popularity and aromatic profile, is an autochthonous variety commonly used in the production of light, fruity wines distinguished by their modest alcohol levels, a light to medium body, and pleasant aroma profiles [42]. Chardonnay, renowned worldwide, is also widely recognized and esteemed in Hungary. The winery engaged in the experiments provides an assortment of distinct Chardonnay styles. To ensure an effective comparison, the Chardonnay grape material chosen for the trial was selected due to its characteristics similar to the Irsai Olivér batch; therefore, it was an early-harvested material intended for a light Chardonnay with primary aromatics and predestined for shorter maturation [43].
The hypothesis we proposed suggests that vegan additives have the potential to achieve a level of clarity during the flotation process comparable to that obtained with traditional animal-derived substances. Our goal was to demonstrate that the use of alternative processing aids provides the technological integrity of the grape must and the sensory characteristics of the wine. Another significant aim was to evaluate grape varieties that currently face difficulties under Hungarian conditions.
A significant flaw in the experimental design was the challenge of reproducing the results, since the batches were aimed at commercial production. As the winery equipment was oversized for the requirements of our experiment, we could only replicate the flotation experiments, while the fermentation process had already been conducted in equalized batches.
Nitrogen had to be used for flotation as Irsai Olivér is an aromatic grape variety and therefore vulnerable to oxidation [27,44,45,46]. Should the primary aromas be diminished due to excessive oxidation [4] (p. 123), the wine loses its character, rendering it unmarketable. Although flotation combined with hyperoxidation might prove effective for Chardonnay, allowing for the successful removal of interfering polyphenols, we ultimately had to reject this method to ensure batch comparability.
Another gap was the limited specificity of the analytical methods with respect to the different polyphenolic fractions present in grapes. However, our objective was to employ measurement techniques that have straightforward requirements and can be readily applied in winery operations.

2. Materials and Methods

Both trials were conducted during the 2024 vintage in the Etyek-Buda wine region of Northwestern Hungary at a large-scale winery with an international background, focusing on producing still and sparkling wines with the Etyek geographical indication. The flotation experiment utilized two varieties: Irsai Olivér and Chardonnay, whereas the gravitational sedimentation test was conducted with Irsai Olivér.

2.1. Grape Processing and Must Production

The initial analysis of the musts well reflected the characteristics of the varieties, their maturity grade, and the vintage (Table 1). The grape materials were collected at a ripeness level intended to produce light wines with a moderate alcohol content and primary aromatic qualities. Irsai Olivér had lower acidity and a rather modest phenolic character. In the case of Chardonnay, a pronounced acidity was observed along with the presence of more phenolic substances, which also predicted a greater body. The original nutrient content (YAN) could be considered just sufficient for a secure fermentation [47]. With the use of the fermentation support recommended by the manufacturer, a complete fermentation of the total sugar content was anticipated without encountering any fermentation issues.
Both grape varieties, Irsai Olivér and Chardonnay, were processed the same way. After mechanical harvest, the grape material was crushed, and a combined antioxidant additive (dosage: 25 g per 100 L; consisting of 50% potassium metabisulfite, 30% ascorbic acid, and gallnut tannin) and a liquid enzyme complex (dosage: 3 mL per 100 L; pectinase with beta-glucosidase activity) were added to the mash. Following pressing, samples for basic analysis were collected. The musts were then treated for 12 h with liquid pectinase at a dose of 3 mL per 100 L. The antioxidant additive and both enzyme products were purchased from Erbslöh Austria GmbH (Siegendorf, Austria).

2.2. Preliminary Small-Scale Static Must Sedimentation Studies

Twenty-four portions of Irsai Olivér must, 5 L each, were separated for the gravity sedimentation experiment. The must portions were filled into glass flasks, and each was treated with 50 mg/L sulfur dioxide. Seven must clarification processing aids (Table 2) were added in triplicate, and three portions of grape must were settled without any processing aid (reference batch). The clarification processing aids were purchased from Erbslöh Austria GmbH (Siegendorf, Austria). The results of gravity sedimentation were evaluated after 12 h.
The sedimentation loss, turbidity, and changes in the assimilable nitrogen (YAN) content were examined. Turbidity was measured using a Turbiquant 1100 IR device (Merck KGaA, Darmstadt, Germany) in the winery.
YAN levels (expressed in mg N per liter) were measured and calculated using the ninhydrin reagent by spectrophotometry. For 50 mL of reagent, 1.5 g of ninhydrin, 1.25 mL of glacial acetic acid, and 6.3 g of Na-acetate · 3H2O were mixed and diluted in 2-methoxyethanol. The must samples were diluted tenfold with purified water. Then, 1 mL of reagent was added to 0.5 mL of the diluted sample in a screw cap test tube. The sealed test tube was placed in boiling water at 100 °C for 15 min. After cooling, 5 mL of a 1:1 mixture of water and isopropanol was added, and the absorbance was measured at 570 nm. The reference sample was prepared following the same procedure, but with purified water instead of grape must. The calibration was performed with valine (Merck Life Science Kft., Budapest, Hungary). The YAN values expressed in nitrogen were calculated from the analytical results expressed in valine on the basis of molecular weights.
Statistical analysis of the datasets was performed using one-way ANOVA followed by Tukey test with a 95% confidence interval (IBM SPSS Statistics, Version 29, IBM Corp., Armonk, NY, USA).

2.3. Clarification of the Grape Must Through Flotation

To conduct the flotation experiments, the musts of the two varieties were divided into six portions each. Three portions were floated with liquid gelatin (dosage: 70 mL per 100 L; 20% gelatin content (Erbslöh Austria GmbH, Siegendorf, Austria)), or with a liquid mixture (suspension) of phytoprotein and chitin–glucan (dosage: 150 mL per 100 L; 10% pea protein content (Erbslöh Austria GmbH, Siegendorf, Austria)) as a processing aid, respectively (Table 3). The ratio of the removed components was then calculated using the average values of the triplicates.
The flotation time was 40 to 45 min for Irsai Olivér and 50 to 55 min for Chardonnay, with nitrogen injection (SIAD Hungary Kft., Miskolc, Hungary), using an Easyfloat flotation equipment (JU.CLA.S. S.r.l., Settimo di Pescantina, Italy). All juices had a temperature of 18 °C.
Following flotation, the three parallel batches were blended, and the vinification process was completed in a single batch of each treatment (IO Gel, IO Pea, CH Gel, and CH Pea, respectively). To ensure consistent treatment, batches of each variety were inoculated with specific Saccharomyces cerevisiae yeasts. The two Irsai Olivér batches were inoculated with an alcohol-tolerant hybrid yeast capable of increased thiol production and fermented at 16 °C (Erbslöh Austria GmbH, Siegendorf, Austria). Chardonnay batches underwent fermentation at 16 °C with a characterizing yeast, utilizing an enhanced release of mannoprotein autolysates (Erbslöh Austria GmbH, Siegendorf, Austria). In each batch, a fermentation activator composed of inactivated yeast and yeast cell walls was added as a nutrient supplement (Erbslöh Austria GmbH, Siegendorf, Austria). After fermentation, 50 mg/L of sulfur dioxide was added. Two 0.75 L samples were taken from each of the four batches of wine and sealed in standard glass bottles with a screw cap to ensure stability and prevent any alteration until they could be subjected to sensory analysis.
The dosage of each additive and processing aid was determined according to the manufacturers’ recommendations.

2.4. Chemical Analysis After Flotation Experiments

After pressing, a basic analysis—determination of reducing sugars, acidity, and pH values—was conducted, using a WineScan Flex wine analyzer (FOSS Analytical A/S, Hilleroed, Denmark), which operates on the FTIR principle. Before and after the flotation treatments, the total polyphenol (TP) content and YAN levels were measured, and additionally, an acid butanol assay (ABA; specific for condensed tannins) and a vanillin assay (VA; specific for both condensed tannins and monomeric flavanols) were conducted [48,49]. Sensory evaluation was performed on the young wines after fermentation, following the first racking.
YAN values were determined according to the method described in Section 2.2.
TP was assessed using a modified version of the Folin–Ciocalteu technique. The outcomes were derived from a calibration with gallic acid and thus reported in gallic acid equivalent [50] (pp. 119–120).
For ABA, samples were evaluated by spectrophotometry at 550 nm after conducting Flanzy’s procedure, which involves heating with a butanol–hydrochloric acid solution containing iron(II) sulfate. The findings are presented in terms of malvidin-3,5-diglucoside [51].
VA was performed using spectrophotometry at 500 nm after conducting a color reaction with vanillin in a sulfuric acid–ethanol medium, following the Rebelein method [52]. Results are expressed as catechin equivalents.
Chemical analysis was performed at the Department of Oenology, Hungarian University of Agriculture and Life Sciences (MATE), Budapest. Spectrophotometry was conducted using a Dynamica Halo RB-10 (Precisa Gravimetrics AG, Dietikon, Switzerland) UV-VIS spectrophotometer.
Data statistical analysis was performed using one-way ANOVA and Tukey’s test with a 95% confidence interval (IBM SPSS Statistics, Version 29.0.1.0 (171), IBM Corp., Armonk, NY, USA).

2.5. Sensory Analysis

The Chardonnay and Irsai Olivér wines from the flotation experiment were subjected to sensory analysis. The sensory assessment was performed by seven colleagues from the Department of Oenology at MATE and the winery, each of whom holds a degree in enology, on 17 October 2024, in the sensory laboratory of the Department of Oenology at MATE. All members voluntarily participated in the task. The sensory evaluation conditions were organized according to the recommendations and suggestions of the OIV [53].
Six olfactory contributions (intensity of the overall positive aroma in the nose and on the palate, intensity of fruitiness in the nose and on the palate, sensation of freshness in the nose, intensity of bitter taste) were evaluated on a scale of 1 to 10, corresponding to the perceived intensity [54]. The varietal wines were tested in two distinct series, conducted independently, in two repetitions. In each series, the two wines were evaluated in parallel, allowing a straightforward comparison of the two treatments, which was the main goal of the sensory analysis. In the first series, the Irsai Olivér samples were evaluated, continuing with the two Chardonnay samples in the second series. The sequence of the samples within the series was chosen at random. The samples were anonymized for both treatment and variety.
Statistical analysis of the results was performed using one-way ANOVA with a 95% confidence interval for each olfactory contribution, where the repetitions were provided by the members’ results (IBM SPSS Statistics, Version 29.0.1.0 (171), IBM Corp., Armonk, NY, USA).

3. Results

3.1. Results of Gravitational Sedimentation Trials

Due to gravitational sedimentation, approximately one-fifth of the must volume settled in all samples (Table 4). The reference sample exhibited outstanding levels of clarification. Treatment agents containing animal-derived ingredients (IO 1, IO 2, and IO 3) were also effective in reducing turbidity. The IO 6 sample (pea protein with chitin–glucan) demonstrated a comparable result, which was indicated by its NTU value in addition to the volume of the removed sediment content. This combination of processing aids was also among the top performers in terms of nutrient retention and is characterized as being especially gentle. This is in line with our previous experiences [41], demonstrating the value of pursuing additional prefermentative clarification experiments with this material combination.
In contrast, the product consisting solely of pea protein, although performing excellently in clarification, caused a significant decrease in YAN (IO 5). It should also be noted that the IO 7 sample, which was processed with a combination of pea protein, bentonite, and yeast protein, consistently exhibited a high NTU value, reflecting turbidity throughout the gravitational settlement process.

3.2. Chemical Analysis of the Musts Related to Flotation Processes

For Irsai Olivér (Table 5) and Chardonnay (Table 6), the application of gelatin or a plant protein for flotation exhibited minimal or no effects on YAN levels. Nitrogen levels showed a modest reduction, especially when gelatin was used. The decrease can be trusted to be related to the removal of turbid substances.
The unusually dry and warm conditions in 2024 led to musts with anomalies in the phenolic composition. The flotation treatments reduced TP by 20% in the Irsai Olivér, with the plant-based processing aid performing marginally better. Although Chardonnay had a notably higher TP value, the reduction observed was minimal, ranging from 0% to 3%. The increased acidity level of Chardonnay and the prevention of oxidation throughout the treatment process may have negatively influenced the performance of the flotation agents.
The results determined by ABA and VA generally decreased during the flotation experiments. Generally, gelatin was more effective in removing condensed tannins and monomeric flavanols than the vegan alternative in both varieties, but a statistical analysis did not show significant differences in all results. In Irsai Olivér, gelatin proved to be significantly more effective in removing substances determined by the VA method, including monomeric flavanols (mainly catechins) and condensed tannins (by 19%), than the vegan processing aid (3%).
However, in Chardonnay, components determined by the ABA method decreased to a greater extent during flotation (18.9% with gelatin and 8.6% with the vegan alternative) when compared to the Irsai Olivér. The decrease in TP and ABA values during the treatment were minimal, regardless of the processing aid used. It should be noted that, in a technological sense, this grape material was further from physiological maturity than Irsai Olivér, suggesting the presence of unripe phenolics in elevated amounts. Nonetheless, the technological goal of an appropriate prefermentative turbidity was achieved with both processing aids, resulting in turbidity values below 10 NTU in all batches at the end of the flotation processes.

3.3. Sensory Analysis of the Wines

The sensory properties of the two Irsai Olivér wines showed great similarity, with identical results for some descriptors (Figure 1a). Based on aroma and taste characteristics, the IO Pea received generally better scores during tasting, especially regarding nasal attributes. An exception is presented by the freshness, for which the IO Gel proved to be better by 0.5 points. A greater difference can be observed in terms of bitterness, with the vegan sample having a less bitter taste. Although the analytical findings of phenolic compounds might not validate the result, it is important to remember that the bitterness in aromatic varieties like Irsai Olivér might also be attributed [55] to terpene glycosides [4] (p. 192). Perhaps the differences are not overly significant, but it can be stated that vegan treatment agents are also capable of developing good sensory characteristics and a typical varietal character of aromatic grape varieties, such as Irsai Olivér, expected by both winemakers and consumers.
The use of flotation agents in Chardonnay produced somewhat different outcomes than in Irsai Olivér. The results, depicted in Figure 1b, indicated that the CH Gel wine had a superior overall sensory profile, despite that both wines exhibited pleasing sensory qualities. Fruity nose, fruity taste, and overall taste experience received higher ratings. According to the statistical analysis, the difference between the two batches proved to be significant in the case of fruity aroma and fruity taste. CH Gel was less bitter and also had greater freshness. The sensory experience of CH Pea wine, on the other hand, was less well-balanced due to its somewhat higher bitterness and weaker scent and flavor intensity. The research showed that gelatin flotation improved the organoleptic qualities of Chardonnay more than the plant-based, pea protein substitute.

4. Discussion

The static sedimentation trial emphasizes the importance of must clarification and the complex relationship between the materials utilized and the must. According to the findings, gravity sedimentation as the primary step in vinification consistently eliminates comparable amounts of sediment; however, the processing aids utilized have a significant impact on the actual clarity and nutritional content of the grape must.
Conventional products (gelatin and isinglass) for prefermentative sedimentation gave adequate results in gravitational sedimentation. The results confirmed that certain vegan processing aids, such as pea protein and chitin–glucan, offered a special blend of gentle treatment and similar clarification effectiveness, which is essential for wine quality and ensures the fermentation process. Conversely, although pure pea protein was effective in clarification, it led to considerable loss of nutrients, creating a potential risk in the vinification process. This contrast emphasizes the importance of not only focusing on clarity, but also maintaining a balanced nutrient profile during gravitational sedimentation.
Both tested flotation processing agents performed appropriately in the must clarification trials, although they exhibited varying specific efficiency in the two varieties. Our hypothesis was confirmed that the vegan alternative can achieve results similar to the conventional flotation agent. The combination of plant protein and chitin–glucan was completely suitable for flotation, offering an appropriate vegan alternative in winemaking techniques, particularly for aromatic types such as Irsai Olivér.
None of the flotation processing aids had a negative impact on the initial YAN composition of grape musts in the trials.
Given the compositional traits caused by the challenging vintage characteristics, such as accelerated phenology and very early ripening, flotation was a good choice to achieve a must quality intended for a light and fruity wine style. The alterations in the composition of the must could be the cause of the anomalies in the efficacy of the flotation agents. Plant proteins may struggle to withstand a higher concentration of phenolics since they need a different kind and quantity of phenolic binding surface in comparison to gelatin. The presence of oxygen (e.g., hyperoxidation during flotation) could have improved the clarification results; however, for the aromatic variety in the experiment, this was not recommended at all.
For Irsai Olivér, both treatments resulted in wines that shared similar sensory characteristics. While the gelatin-treated wine appeared fresher, the vegan version was less bitter and earned higher overall scores, particularly in aroma. The findings indicated that the plant-based processing aid was able to enhance typical sensory attributes of the variety, just as effectively as traditional clarification agents. This remained accurate despite the use of nitrogen in flotation to prevent the oxidation of vulnerable components.
However, in the case of Chardonnay, gelatin clearly performed better, resulting in a wine with an overall better sensory profile in terms of both aroma and overall taste. The Chardonnay treated with gelatin was fresher and less bitter than the vegan alternative, which was less balanced, with a stronger bitterness and a weaker aroma and flavor intensity. Therefore, the research concluded that the flotation of grape must supported by gelatin improved the sensory properties of Chardonnay better than the plant-based alternative.
Chardonnay, being a grape variety with neutral organoleptic properties, has its flavor profile significantly shaped by winemaking practices, including prefermentative must clarification techniques. Under conditions that exclude oxidation, gelatin was more effective in removing unpleasant and bitter compounds while maintaining the delicate aromas, leading to a more harmonious and enhanced wine sensory experience. However, the plant-based clarification agent was less effective, resulting in a weaker aroma and flavor intensity for Chardonnay wine.
In circumstances where mitigation of oxidative effects is essential, particularly for Irsai Olivér with its vulnerable aromatic components, the application of plant proteins merits consideration. However, in early-harvested grape materials with immature, astringent phenols, this clarification process may prove insufficient. In such cases, a promising approach to the elimination of elements responsible for unfavorable sensory traits may be the integration of targeted oxidation with the use of processing aids consisting of either animal-derived proteins or vegan alternatives.

5. Conclusions

The efficacy of vegan must clarification agents was considered similar to that of conventional products in prefermentative treatments. The clarity achieved by all treatments met the technological goal of starting fermentation in properly prepared musts. The secure course of fermentation and subsequent clarification of the wines were ensured.
In general, plant proteins and gelatin work well as processing aids in winemaking. Although plant-based fining agents are a great substitute for gelatin in aromatic wines, they should also be taken into account for other types of wine.
The results clearly justify further research. In particular, the optimization of the combination of pea protein and chitin–glucan deserves more attention, as this “soft” approach may represent a promising alternative to traditional processing aids. Furthermore, exploring the efficacy and interactions of various plant-derived substances is valuable for offering winemakers a broader selection of sustainable options to produce high-quality wines. Future studies would be worth expanding with various factors, such as the implementation of various processing aids alongside hyperoxidation techniques, other (late ripening) aromatic grape varieties, and analyzing grape materials at several stages of fruit ripeness.

Author Contributions

Conceptualization, Á.P.S., N.A.N. and D.Á.N.S.; methodology, Á.P.S., A.S.-L. and D.Á.N.S.; writing—original draft preparation, Á.P.S., A.S.-L., N.A.N. and B.N.; writing—review and editing, Á.P.S., A.S.-L. and D.Á.N.S.; visualization, A.S.-L.; supervision, D.Á.N.S. and Z.V.; project administration, D.Á.N.S., Z.V. and B.N. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

National laws do not require ethical approval for sensory evaluation. Sensory analyses involved employees of the MATE and of the experimental site who participated voluntarily and without the collection or processing of sensitive personal data. The study was carried out according to the MATE Ethical Codex, §8 Ethical standards, rights and obligations for persons engaged in educational and research activities (FI 51129, 18 August 2021).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

The authors would like to thank Pázmányi Dániel, the winemaker at Haraszthy Pincészet Kft., for providing the conditions for the experiments and Hannes Weninger (Erbslöh Austria GmbH) for offering materials tested in the trials. During the preparation of this manuscript, the authors utilized Chat-GPT (GPT-5, OpenAI) to generate the visual elements incorporated in the graphical abstract. The authors have reviewed and edited the output and take full responsibility for the content of this publication.

Conflicts of Interest

The authors declare no conflicts of interest.

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Fermentation 11 00569 g001
Figure 1. Sensory profiling results of (a) Irsai Olivér and (b) Chardonnay wines fermented from musts after flotation treatment conducted with gelatin or with a vegan alternative as processing aid. For attributes denoted by an asterisk (*), a one-way ANOVA determined a significant difference (p < 0.05).
Figure 1. Sensory profiling results of (a) Irsai Olivér and (b) Chardonnay wines fermented from musts after flotation treatment conducted with gelatin or with a vegan alternative as processing aid. For attributes denoted by an asterisk (*), a one-way ANOVA determined a significant difference (p < 0.05).
Fermentation 11 00569 g001
Table 1. Initial composition of the grape musts before clarification.
Table 1. Initial composition of the grape musts before clarification.
Compound/MeasureIrsai OlivérChardonnay
Reducing Sugars (g/L)171.5165.6
Titratable Acidity (g/L)6.008.55
pH3.543.40
YAN (mg/L)112118
TP (mg/L)434774
ABA (mg/L)573809
VA (mg/L)711792
Table 2. Experimental setup of the static sedimentation experiment. Product ingredients of animal origin are highlighted in bold fonts.
Table 2. Experimental setup of the static sedimentation experiment. Product ingredients of animal origin are highlighted in bold fonts.
BatchComposition and Formula of the Clarifying Agent
IO 0reference batch (no processing aid used)
IO 112% gelatin, citric acid, 10% PVPP, 1% isinglass, SO2 (liquid)
IO 240% gelatin, 10% cellulose, 35% bentonite, 15% PVPP (powder)
IO 32% isinglass, citric acid, SO2 (liquid)
IO 410% cellulose, 60% pea protein, 10% PVPP, 20% bentonite (powder)
IO 5100% pea protein (powder)
IO 610% pea protein, chitin–glucan, tartaric acid, SO2 (liquid)
IO 760% pea protein, 20% bentonite, 20% yeast protein (powder)
Table 3. Experimental setup of flotation trials. The intervals of the triplicate results are shown in parentheses. In IO batches, a significant difference (p < 0.05) was observed in the sediment quantity (letters (a and b) indicate significantly differing batches); in CH batches, no significant difference (p > 0.05) was observed due to one-way ANOVA.
Table 3. Experimental setup of flotation trials. The intervals of the triplicate results are shown in parentheses. In IO batches, a significant difference (p < 0.05) was observed in the sediment quantity (letters (a and b) indicate significantly differing batches); in CH batches, no significant difference (p > 0.05) was observed due to one-way ANOVA.
Variety/Harvest DateBatchProcessing AidAverage Batch Quantity (hL)Sediment (Loss) (%) *
Irsai Olivér/5 AugustIO Gelgelatin25.3 (24–26)2.6 (2.5–2.6) a
IO Peapea protein + chitin–glucan26.7 (25–28)5.9 (5.9–6.0) b
Chardonnay/26 AugustCH Gelgelatin30.3 (29–31)4.2 (4.0–4.4) a
CH Peapea protein + chitin–glucan30.0 (28–31)4.4 (4.3–4.4) a
* Calculated as the ratio of grape must quantity before and after the flotation process.
Table 4. Sediment content, NTU values, and changes in YAN in Irsai Olivér musts clarified through static sedimentation, using different processing aids. The intervals of the triplicate results are shown in parentheses. For each parameter, letters (a, b, etc.) indicate statistical differences between different processing aids, according to Tukey’s test.
Table 4. Sediment content, NTU values, and changes in YAN in Irsai Olivér musts clarified through static sedimentation, using different processing aids. The intervals of the triplicate results are shown in parentheses. For each parameter, letters (a, b, etc.) indicate statistical differences between different processing aids, according to Tukey’s test.
BatchSediment (%)NTUDecrease in YAN (%)
IO 021.6 (21.5–21.6) f29 (27–31) a3.2 (2.7–3.9) b
IO 120.1 (20.0–20.2) c42 (40–44) b3.7 (3.5–4.0) b
IO 220.6 (20.5–20.7) d32 (30–34) a2.9 (2.6–3.2) b
IO 320.6 (20.5–20.6) d41 (38–42) b7.6 (7.1–8.6) d
IO 416.6 (16.5–16.7) a28 (26–30) a3.7 (3.0–4.3) b
IO 521.0 (20.9–21.0) e31 (30–32) a19.9 (19.5–20.3) e
IO 621.8 (21.7–22.0) f33 (30–35) a0.0 (−0.2–0.4) a
IO 719.4 (19.3–19.5) b66 (64–68) c6.0 (5.8–6.4) c
Table 5. Proportion (%) of removed substances during flotation of Irsai Olivér must with different agents. The interval of the three parallel samples is shown in parentheses. Letters (a and b) indicate statistically different results among processing aids with p < 0.05.
Table 5. Proportion (%) of removed substances during flotation of Irsai Olivér must with different agents. The interval of the three parallel samples is shown in parentheses. Letters (a and b) indicate statistically different results among processing aids with p < 0.05.
CompoundIO GelIO Pea
YAN7.9 (7.5–8.2) b2.9 (2.1–3.6) a
TP19.7 (17.1–22.6) a20.8 (20.0–21.9) a
ABA9.4 (9.0–10.0) a5.9 (3.0–7.7) a
VA19.1 (18.4–20.1) a3.1 (2.3–3.7) b
Table 6. Proportion (%) of removed substances during flotation of Chardonnay must with different agents. The interval of the three parallel samples is shown in parentheses. Letters (a and b) indicate statistically different results among processing aids with p < 0.05.
Table 6. Proportion (%) of removed substances during flotation of Chardonnay must with different agents. The interval of the three parallel samples is shown in parentheses. Letters (a and b) indicate statistically different results among processing aids with p < 0.05.
CompoundCH GelCH Pea
YAN5.8 (5.1–7.0) b0 (0–1.7) a
TP1.8 (0–3.1) a0 (0–0.5) a
ABA18.9 (18.0–19.5) a8.6 (5.1–11.5) b
VA0.3 (0–0.6) a3.6 (1.8–4.7) a
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MDPI and ACS Style

Szövényi, Á.P.; Sólyom-Leskó, A.; Nagy, B.; Varga, Z.; Németh, N.A.; Nyitrainé Sárdy, D.Á. Comparison of Gelatin and Plant Proteins in the Clarification of Grape Musts Using Flotation Techniques. Fermentation 2025, 11, 569. https://doi.org/10.3390/fermentation11100569

AMA Style

Szövényi ÁP, Sólyom-Leskó A, Nagy B, Varga Z, Németh NA, Nyitrainé Sárdy DÁ. Comparison of Gelatin and Plant Proteins in the Clarification of Grape Musts Using Flotation Techniques. Fermentation. 2025; 11(10):569. https://doi.org/10.3390/fermentation11100569

Chicago/Turabian Style

Szövényi, Áron Pál, Annamária Sólyom-Leskó, Balázs Nagy, Zsuzsanna Varga, Noémi Aletta Németh, and Diána Ágnes Nyitrainé Sárdy. 2025. "Comparison of Gelatin and Plant Proteins in the Clarification of Grape Musts Using Flotation Techniques" Fermentation 11, no. 10: 569. https://doi.org/10.3390/fermentation11100569

APA Style

Szövényi, Á. P., Sólyom-Leskó, A., Nagy, B., Varga, Z., Németh, N. A., & Nyitrainé Sárdy, D. Á. (2025). Comparison of Gelatin and Plant Proteins in the Clarification of Grape Musts Using Flotation Techniques. Fermentation, 11(10), 569. https://doi.org/10.3390/fermentation11100569

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