Circular Model for the Valorization of Black Grape Pomace for Producing Pasteurized Red Must Enriched in Health-Promoting Phenolic Compounds

Abstract

As compared to red wine technology, where pomace is macerated, the grape juices and musts are obtained by pressing the grapes and removing the pomace, thus removing an important source of antioxidant molecules. The objective of this study was to exploit the bioactive compounds from the black grape pomace and obtain a new food product, namely pasteurized red must with improved health-promoting properties. The study was conducted on four grape varieties for red wines—Fetească Neagră, Cabernet Sauvignon, Blauer Zweigelt, and Arcaș—each coming from a certain recognized Romanian vineyard, as follows: Murfatlar, Dealu Mare, Ștefănești-Argeș, and Iași, respectively. Both the must and the pomace extract used for each product were from the same variety and region. The recovery of polyphenols was achieved by macerating the pomace at ambient temperature, using solutions of ethanol in concentrations of 25%, 50%, and 75%. The results showed that the most efficient method of polyphenol recovery was obtained by using the ethanolic solution of 50%, which was selected for the subsequent stages of the study. The selected hydroalcoholic extract was concentrated by eliminating the solvent by roto evaporation and used as a source of supplementary bioactive compounds for the pasteurized must. The phenolic profiles of the musts enriched with phenolic extracts were determined by liquid chromatography, UHPLS-HRMS, revealing significant increases in the content of individual phenolic acids and other polyphenols. The phenolic extract recovered from the pomace significantly optimized the phenolic quality of the pasteurized must, thus contributing to the improvement of its nutritional value. The new product has a phenolic profile close to that of a red wine, but does not contain alcohol. Also, this technology is a sustainable method to convert grape waste into a safe, antioxidant-rich grape juice with potential health benefits.

1. Introduction

In the current context of bioeconomy development, which emphasizes the efficient use of natural resources and waste reduction, research on the implementation of circular models for the valorization of winemaking by-products—such as grape pomace—has become a strategic priority. Circular economy principles are a fundamental pillar of the transition toward a sustainable system, contributing to environmental impact mitigation, resource reuse, and the creation of new economic opportunities [1,2]. According to United Nations Organization estimates, the global population could reach approximately 10 billion by the year 2050. This growth, combined with the intensification of climate change and the ongoing reduction in agricultural land, primarily due to desertification, leads to increasing pressure on global food security. In response, the European Union (EU) aims to achieve climate neutrality by 2050, as part of its strategy to mitigate these effects and promote the sustainable use of natural resources. The transition to a circular economy, which is focused on reuse, recycling, and reduction, is essential for developing a sustainable consumption model [3,4].

The wine industry is a key agri-food sector with a notable environmental footprint due to its substantial consumption of natural resources, particularly water, but also due to the large volumes of solid and liquid waste it generates worldwide [5,6]. According to data from Oliveira et al. [7], processing 1000 kg of grapes typically yields around 750 L of wine, 130 kg of grape marc, 60 kg of yeast, and 1650 L of wastewater.

Grape pomace, the primary by-product of winemaking, comprises skins, seeds, and stem residues, and accounts for approximately 25% of the total mass of processed grapes [8]. Globally, the annual production of grape pomace is estimated at approximately 8.49 million tons, underscoring its significant potential for valorization as an agro-industrial by-product [9], and this is the reason we have selected to focus this study on this by-product management. Recent studies have shown that grape pomace is a valuable source of bioactive compounds, particularly polyphenols, such as anthocyanins, flavonoids, catechins, and phenolic acids, recognized for their antioxidant, anti-inflammatory, and anticancer properties [10]. The phenolic composition of grape pomace varies depending on grape variety, climatic conditions, geographical origin, and cultivation practices [11]. As a significant portion of these compounds is not fully extracted during vinification, grape pomace remains a rich source of polyphenols with high potential for further exploitation [12,13].

Phenolic compounds are generally classified into two major groups: flavonoids (including flavonols, flavanols, and anthocyanins) and non-flavonoids (such as phenolic acids, stilbenes, and lignans) [14]. Due to its complex composition, grape pomace represents a significant source of phenolic compounds and is thus considered a promising raw material for the development of functional food products with potential health benefits for consumers [15].

Currently, various strategies for the valorization of grape pomace are under investigation, with a particular focus on the extraction and application of phenolic compounds, which are among the most abundant bioactive constituents in this by-product. Extraction constitutes the essential first step in the valorization process, and both the final composition and the biological activity of the extracts are directly influenced by the method employed [16]. Among traditional techniques, solid–liquid extraction via maceration remains one of the most widely used methods [6]. Although it is labor-intensive and time-consuming, a key advantage lies in its minimal requirement for expensive equipment. This conventional approach is frequently applied for extracting bioactive compounds from plant materials, including grapes and grape pomace. The efficiency of the process is influenced by several factors, including the solubility of target compounds, temperature, solvent concentration, particle size, porosity, and stirring intensity. Due to its complex biochemical composition, including dietary fiber, polyphenols, residual sugars, proteins, and micronutrients, grape pomace has traditionally been used in agriculture, particularly as animal feed and organic fertilizer. When used as a feed supplement, pomace has been shown to enhance the nutritional value of livestock diets, increasing the levels of bioactive compounds in animal products (milk and meat). For instance, Blasi et al. [17] demonstrated that incorporating pomace into animal feed can improve the lipid and antioxidant profiles of animal-derived products without adversely affecting animal health or the nutritional quality of the food. Meanwhile, the application of pomace as an organic fertilizer offers an effective ecological strategy for restoring soil fertility. Rich in organic matter and essential nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium, pomace can be directly applied to the soil or used in composting. This practice stimulates microbial activity, improves soil structure, enhances water retention, and reduces reliance on chemical fertilizers. Additionally, the phenolic compounds present in pomace may exert moderate antifungal effects, contributing to the phytosanitary protection of crops [18]. The use of pomace as a nutrient source shows considerable promise and is already being implemented in organic viticulture. In addition to being low-cost and readily available to farmers, the incorporation of pomace-based compost or vermicompost into soil fertilization systems serves as a sustainable waste management solution. This approach aligns with broader efforts to promote sustainability in agriculture [19].

Concurrently, consumer preferences have shifted increasingly toward natural food products free from synthetic additives. This trend, coupled with growing interest in nutraceuticals, has driven the search for natural sources to support the development of functional foods [20]. Studies have demonstrated that phenolic extracts can be successfully incorporated into a variety of food matrices, thereby enhancing their nutritional value [21]. Grape pomace, in particular, has been used to fortify bakery products [22,23], yogurt, and cheeses [24,25]. For example, biscuits enriched with grape pomace extract have been shown to contain significantly higher levels of total polyphenols and exhibit greater antioxidant activity compared to control samples [26]. More recently, nutritionally enhanced leavened bakery products, such as pizza crusts, have also been developed using grape pomace flour. In a study by Difonzo et al. [27], wheat flour was partially replaced with grape pomace flour at levels of 15%, 20%, and 25%. The resulting products demonstrated increased phenolic content and improved antioxidant properties. A similar strategy was employed to produce muffins with higher fiber content and reduced fat levels [28]. In the case of unleavened bakery products, grape pomace flour was used to fortify breadsticks by substituting 0.5 g and 10 g of wheat flour per 100 g of product [29]. These fortified breadsticks exhibited elevated levels of dietary fiber and phenolic compounds, while maintaining satisfactory sensory acceptability [30]. Panić et al. [31] developed and validated pilot-scale procedures for anthocyanin extraction from grape pomace, confirming their applicability in the food industry and their potential to improve the nutritional profile of final products. Owing to their broad spectrum of biological activities, extracted polyphenols have also been incorporated into a range of food products, including meat, fish, pasta, ice cream, dairy, and confectionery items [32]. Milinčić et al. [33] investigated the physical and functional properties of goat milk powder enriched with grape pomace seed extract. Their findings showed that the enriched milk, even after heat treatment, exhibited enhanced emulsifying properties and stability, underscoring its potential as a valuable functional ingredient. Similarly, Ratu et al. [34] demonstrated that incorporating just 1.6% grape pomace powder into Caciotta cheese significantly increased the product’s antioxidant activity.

While the application of grape pomace in solid food products has been widely studied, its use in beverages remains relatively underexplored. In this context, Canalejo et al. [14] examined the role of phenolic compounds extracted from grape pomace in enhancing the aromatic profile of wine. Their study emphasized a complementary approach in which grape pomace is added during fermentation to boost both polyphenol content and aromatic quality. This approach was successfully validated in wines made from the Pinot Noir variety [35]. Additionally, there is growing evidence that the incorporation of unfermented grape pomace during the brewing process can enhance the volatile profile and antioxidant capacity of beer, contributing to the development of innovative beverages with potential health benefits [36].

In recent years, the valorization of winemaking by-products, among which grape pomace is of particular importance, has emerged as a strategic path for the development of non-alcoholic functional beverages, through the recovery of phenolic compounds with documented bioactive properties. Grape must enriched with phenolic extracts derived from pomace represents a promising option from both nutritional and agro-food sustainability standpoints. This approach aligns with the principles of circular bioeconomy, enabling the production of a beverage with antioxidant potential comparable to that of wine, but without alcohol content.

Unlike wine, which achieves a high concentration of polyphenols through extraction during grape pressing and the optional maceration step during alcoholic fermentation, the enrichment of must with phenolic extracts enables the preservation of a functional nutritional profile without involving alcohol, thereby making the product accessible to a broader range of consumers. Furthermore, while the bioactive compound profile in wine is highly dependent on fermentation and storage conditions, in enriched must, preservation techniques such as pasteurization or modern non-thermal methods (e.g., ultrasound) can ensure optimal stability of these compounds [37].

The integration of phenolic compounds into non-alcoholic grape must-based beverages represents an innovative direction in functional food development, with potential health benefits and a positive sustainability impact on the wine industry. Recent studies highlight a range of technological approaches aimed at maximizing the extraction and stability of bioactive compounds from viticultural by-products. Aguilar et al. [38] demonstrated that thermomaceration of grape pomace, vine leaves, and canes can yield a functional beverage with high antioxidant activity, supporting the valorization of such by-products within a circular bioeconomy framework. In a complementary direction, Blaszak et al. [39] employed ultrasound-assisted maceration technology to enhance polyphenol extraction from Vitis vinifera L., resulting in must with improved physicochemical properties and significantly reduced microbial load. This opens promising perspectives for replacing sulfites with non-invasive physical preservation methods.

Similarly, Margean et al. [40] compared the effects of pasteurization and high-power ultrasound on red grape must, revealing beneficial modifications in phenolic content and antioxidant activity. Collectively, these studies support the potential of grape must enriched with phenolic extracts from viticultural by-products as a viable candidate for developing functional beverages with health-promoting properties.

Although pomace is recognized for its high value as a source of bioactive compounds, it is important to emphasize that obtaining this by-product involves a significant consumption of natural resources, especially water. A study published in 2020 reported that producing one liter of wine requires between 366 and 899 L of water, depending on factors such as irrigation practices, soil conditions, and the winemaking technologies employed [41]. In Italy, the water footprint was estimated at approximately 580 ± 30 L per 0.75 L bottle of wine [42]. Notably, vineyard irrigation constitutes the largest portion of this footprint, with estimates indicating approximately 0.315 m³ (315 L) of water needed per kilogram of grapes, which is roughly equivalent to the amount required to produce one liter of wine. In addition, winery operations such as equipment cleaning and sanitation contribute an extra 2–10 L of water per liter of wine produced, a figure supported by specialized literature [43].

As demand for grape pomace in food products continues to grow, it is also important to assess the associated impact on water resources, particularly in regions already facing water scarcity. Nevertheless, recent technological advances in irrigation management have significantly improved water use efficiency in viticulture. By adopting integrated strategies and modern technologies, the wine industry can meet the rising demand for pomace without placing additional stress on local water supplies, thereby supporting a more sustainable and responsible development model [43]. While we recognize the importance of water management for overall product sustainability, this study focuses specifically on the sustainable reuse of grape pomace, a by-product inherently generated during wine and grape juice production.

In the current context, marked by increasing demand for functional foods and sustainable innovations, the present research aims to apply circular bioeconomy principles by transforming a winemaking by-product into a value-added product. This is achieved through the recovery of bioactive compounds from grape pomace and their reintegration into pasteurized must, with the goal of enhancing health-promoting properties and diversifying the range of non-alcoholic beverages.

2. Materials and Methods

2.1. Grape Cultivation

The study was conducted on four red wine grape cultivars (Vitis vinifera L.), each originating from a representative Romanian viticultural region: Fetească Neagră (Murfatlar), Cabernet Sauvignon (Dealu Mare), Blauer Zweigelt (Ștefănești–Argeș), and Arcaș (Iași).

Fetească Neagră is an indigenous Romanian variety highly valued for its quality wines, characterized by balanced natural acidity and fine tannins, which contribute to full-bodied wines with good aging potential. Its versatility and distinctive profile have garnered increasing national and international interest, positioning it as a symbolic variety of Romanian viticulture [44].

Cabernet Sauvignon, a widely cultivated international cultivar in Romania, is appreciated for its robust wines with intense black fruit aromas and complex notes of berries, tobacco, or chocolate, depending on the degree of maturation [45].

Blauer Zweigelt, originally from Austria, is known for its balance between acidity and tannins. It produces fruit-forward wines with subtle spicy notes and is employed both in blends and as a single-varietal wine [46].

Arcaș is a Romanian cultivar developed by the research team at the Viticulture and Winemaking Research and Development Station (SCDVV) in Iași, officially registered in 1985. It originates from an intraspecific sexual hybridization between Cabernet Sauvignon and Băbească Neagră. The variety is distinguished by its good adaptability to Romanian soil and climate conditions, producing full-bodied wines with red fruit aromas and herbaceous tones. Its excellent balance of acidity and tannins makes it suitable for both early consumption and aging [47]. Moreover, Arcaș shows considerable promise for Romanian viticulture due to its tolerance to abiotic stress, including drought and extreme temperatures, rendering it particularly suitable for viticultural regions with challenging climatic conditions.

Details regarding vineyard locations and characteristics are presented in

Table 1. Characteristics of the vineyard plantations of the four vineyards studied.

Wine Region	Vineyard	Variety	Planting Year	Coordinates	Planting Distance (m)	Planting Density (Vines/Ha)
Hills of Dobrogea	Murfatlar	Feteasca neagra	2007	44°10′27.57″ N; 28°25′41.38″ E	2.2 × 1.1	4132
Hills of Vallachia and Oltenia	Dealu Mare	Cabernet Sauvignon	1998	44°58′0.75″ N; 26°08′55.77″ E	2.0 × 1.0	4805
	Stefanesti Arges	Blauer Zweigelt	1985	44°48′ N; 25°08′ NE;	2.2 × 1.0	4500
Hills of Moldova	Iasi	Arcas	2009	47°12′30.91″ N 27°32′01.03″ E	2.2 × 1.2	3787

.

2.2. Obtaining Phenolic Extracts from Grape Pomace

The grape pomace used in this study was obtained following the winemaking process conducted in 2023 at the microvinification stations of the research institutions responsible for each grape variety: SCDVV Murfatlar (Fetească Neagră), ICDVV Valea Călugărească (Cabernet Sauvignon), INCDBH Ștefănești (Blauer Zweigelt), and SCDVV Iași (Arcaș). The grapes were processed using a traditional winemaking method involving maceration–fermentation for five days, followed by pressing with a hydraulic press.

After wine separation, the pomace was conditioned by drying in a thin layer at ambient temperature, which varied between 20 and 25 °C. The material was manually turned every 24 h to facilitate water evaporation and to prevent the development of microorganisms (bacteria and fungi) in moist zones of the layer. The end point of the drying process was determined by periodically monitoring the sample’s weight. Drying was considered complete when the weight remained constant over at least two consecutive measurements taken 24 h apart.

Phenolic compound extraction was performed using hydroalcoholic solutions at room temperature for 24 h under intermittent stirring. A pomace-to-solvent mass ratio of 1:4 was used, with three ethanol concentrations (25%, 50%, and 75%) as solvents. After extraction, the liquid phase was separated from the solid residue by filtration through filter paper, followed by centrifugation at 1700 rpm for 15 min. The resulting extracts were stored at 4 °C for 1–2 days until physico-chemical analyses were performed. The extracts obtained from the 2023 pomace were used to enrich the musts produced in 2024. While such extracts are typically prepared from pomace obtained in the same year as the must, in this study, additional time was required to optimize and select the most effective extraction method. This approach ensured the use of the extract with the highest phenolic content and antioxidant activity for must fortification.

2.3. Obtaining Pasteurized Grape Must with Enhanced Health-Promoting Properties

To obtain pasteurized grape must, 10 kg of grapes from each variety (Fetească Neagră, Cabernet Sauvignon, Blauer Zweigelt, and Arcaș) were manually harvested. The grapes had a sugar concentration of over 220 g·L⁻¹. The 2024 harvest was transported to the microvinification stations of the research units involved in the project.

The grapes underwent destemming and crushing using electric equipment, followed by gentle pressing of the resulting mixture (skins, juice, and seeds) in a hydraulic press. The must was then pasteurized at 80–85 °C for 3–5 min to eliminate microorganisms without compromising the integrity of bioactive compounds. After pasteurization, the must was cooled to 40 °C, at which point it was bottled.

For each 950 mL of must, 50 mL of concentrated phenolic extract was added. The enriched must was bottled in 1000 mL glass bottles, sealed with aluminum caps, cooled, and appropriately labeled. The bottles were stored at 5 °C, and analyses were conducted within 30 days of bottling.

2.4. Must Analysis

The physico-chemical properties of the musts were determined using a Lyza 5000 analyzer, which operates based on Fourier Transform Infrared Spectroscopy (FTIR), an advanced technology developed by Anton Paar (Graz, Austria). This method allows for rapid and accurate determination of essential parameters for grape must and wine characterization. The analyzed parameters included sugar content (g·L⁻¹), total acidity (g·L⁻¹ tartaric acid), pH, and total polyphenols (g·L⁻¹).

2.5. Extraction Analysis

Spectrophotometric determinations of total polyphenols, anthocyanin content, antioxidant activity, and phenolic indices (total polyphenol index and Folin–Ciocalteu index) were conducted using Helios Alpha UV-VIS spectrophotometer (Thermo Spectronic, Cambridge, UK) and AnalytikJena Specord 205 UV/VIS (Analytic Jena, Jena, Germany), equipped with 1 cm quartz cuvettes.

Total polyphenol content was expressed as gallic acid equivalents (GAE, g·L⁻¹), using the Folin–Ciocalteu method. Absorbance was measured at 760 nm. For the analysis, 0.1 mL of pomace extract was mixed with 5 mL distilled water and 0.5 mL Folin–Ciocalteu reagent. After 30 min, 1.5 mL of 20% sodium carbonate solution and 2.9 mL distilled water were added. The mixture was incubated for 2 h at room temperature, protected from light. Quantification was performed using a standard curve obtained by serial dilution of gallic acid (in the range of 50–1000 mg·L⁻¹).

Anthocyanin content (mg/100 g pomace) was determined using the Ribéreau–Gayon method, which is based on the pH-dependent color shift in anthocyanins. Absorbance at 520 nm was measured at pH 0.6 and 3.5, using distilled water as a blank [48].

Antioxidant activity (AA%) was assessed based on the radical scavenging capacity of DPPH (2,2-diphenyl-1-picrylhydrazyl), using the method described by Brand-Williams et al. [49]. A volume of 0.1 mL of diluted extract (1:10) was mixed with 3.9 mL of 4% DPPH solution (v/v in 96% ethanol) and stirred. The mixture was incubated in the dark for 30 min. Optical density (OD) or absorbance was measured at 517 nm using glass cuvettes with a 10 mm optical path. The control sample was prepared by replacing the extract with 0.1 mL of 96% ethanol. In this study, for comparative purposes only, we opted to express antioxidant activity directly as a DPPH percentage, the antioxidant activity being calculated using the following formula:

Antioxidant Activity (% DPPH) = (OD_control – OD_sample)/OD_control × 100

(1)

Color intensity was calculated as the sum of absorbance values at 420 nm, 520 nm, and 620 nm, expressed in absorbance units (AU).

The total polyphenol index was determined based on the strong UV absorbance of phenolic benzene rings at 280 nm.

The Folin–Ciocalteu index is based on the reaction between hydroxyl groups of polyphenols and the phosphomolybdic reagent. Upon reduction, a blue-colored mixture of tungsten and molybdenum oxides is formed, with maximum absorbance at 750 nm, proportional to the total phenolic content.

2.6. Circular Model for the Valorization of Grape Pomace

A circular model for the valorization of grape pomace involves the recovery and reuse of resources from this viticultural by-product to develop new value-added products. This approach contributes to waste reduction, natural resource conservation, and the promotion of sustainability within the wine industry. In this study, a circular valorization model was implemented with the goal of creating a new functional food product, namely a grape must with enhanced health-promoting potential, through several key steps and activities:

(a) Step one: Obtaining pomace and extracting polyphenols

• Grape pomace was obtained through the vinification of grape varieties Fetească Neagră, Cabernet Sauvignon, Blauer Zweigelt, and Arcaș from the 2023 harvest.
• Polyphenol extractions were performed using hydroalcoholic solutions at concentrations of 25%, 50%, and 75%.

Following the analysis of the extracts’ parameters (total polyphenols, anthocyanins, color intensity index, antioxidant activity, total polyphenol index, and Folin–Ciocalteu index), results showed that the most efficient recovery of polyphenols was achieved using a 50% hydroalcoholic solution. This concentration was selected for the subsequent stages of the study.

(b) Step two: Preparation of must enriched with concentrated phenolic extract

According to the experimental scheme illustrated in Figure 1, the following activities were conducted in the second stage:

• Obtaining fresh must: Grapes from the varieties Fetească Neagră, Cabernet Sauvignon, Blauer Zweigelt, and Arcaș were harvested, then subjected to destemming and crushing, followed by gentle pressing. The resulting must was pasteurized at 80–85 °C for 3–5 min.
• Extraction of phenolic compounds from pomace: Pomace obtained from each of the four grape varieties was extracted using a 50% hydroalcoholic solution, at a solid-to-liquid ratio of 200 g pomace to 800 mL solvent (as illustrated in Figure 1).

Figure 1. Experimental scheme for the preparation of must enriched with phenolic extract.

Figure 1. Experimental scheme for the preparation of must enriched with phenolic extract.

• Concentration of the phenolic extract: The obtained extract was concentrated using a rotary evaporator, reducing the volume from 200 mL to approximately 50 mL.
• Enrichment of pasteurized must: The pasteurized must was enriched with the concentrated phenolic extract by adding 50 mL of concentrated extract to every 950 mL of must.

2.7. HPLC Analysis of Phenolic Compounds

For analytical determinations, 100 µL aliquots of must and fortified must were evaporated to dryness under a stream of nitrogen using a TurboVap LV system (Biotage, Uppsala, Sweden). The residues were reconstituted in 1 mL of a water–methanol (80:20, v/v) solution, filtered through a 0.45 µm hydrophilic membrane filter, and subjected to instrumental analysis.

Phenolic compounds were identified and quantified using an ultra-high-performance liquid chromatograph UltiMate 3000 UHPLC system (Thermo Fisher Scientific, Bremen, Germany) coupled to a Q Exactive Focus Hybrid Quadrupole-OrbiTrap mass spectrometer equipped with a Heated Electrospray Ionization (HESI) source (Thermo Fisher Scientific, Bremen, Germany). Chromatographic separation was carried out on a Kinetex C18 column (100 × 2.1 mm, 1.7 µm particle size), maintained at 30 °C. A gradient elution program using mobile phase A (0.1% formic acid in water) and mobile phase B (0.1% formic acid in methanol) was applied at flow rates of 0.3 and 0.4 mL/min, respectively, as previously optimized [50]. The mass spectrometer operated in negative ion mode over an m/z range of 100–1000, with a resolution of 70,000. HESI source parameters were set as follows: spray voltage 2.8 kV, capillary temperature 320 °C, auxiliary gas heater temperature 413 °C, and sheath and auxiliary gas flows (N2) at 35 and 10 arbitrary units, respectively [50]. Compound identification and quantification were based on the following spectral characteristics: accurate mass, retention time, and mass fragmentation profiles, compared to external standard solutions. Fragmentation analysis was performed using data-dependent CID (collision-induced dissociation) scans at normalized collision energies of 25, 35, and 45 eV to confirm compound identity.

Instrument calibration was conducted over a concentration range of 0–2000 µg·L⁻¹ for each phenolic compound by serial dilution of a 10 mg·L⁻¹ methanolic standard mixture. All stock and working solutions were stored in the dark at 4 °C. Data acquisition, instrument control, and processing were performed using Xcalibur software version 4.1 (Thermo Fisher Scientific, Bremen, Germany).

2.8. Statistical Analysis

To evaluate the experimental results and validate the conclusions, statistical analyses were performed. All analyses were conducted in triplicate to ensure the accuracy and reproducibility of the results.

In order to assess the effect of different hydroalcoholic concentrations on the recovery of phenolic compounds from grape pomace, a one-way analysis of variance (ANOVA) was applied. Duncan’s post hoc test was used for multiple comparisons between group means, allowing the identification of the optimal concentration for polyphenol extraction.

Correlations between phenolic parameters, such as total polyphenols, anthocyanins, antioxidant activity, and others, were evaluated using Pearson’s correlation test. The significance level was set at 0.05, and only statistically significant correlations were taken into account.

All statistical analyses were conducted using the XLSTAT Add-in for Microsoft Excel, software version 15.5.03.3707 (Addinsoft, New York, NY, USA).

3. Results and Discussion

3.1. Recovery of Phenolic Compounds from Grape Pomace

The selection of the ethanol concentration used in the extraction process was based on a comparative evaluation of the efficiency of three hydroalcoholic solutions (25, 50, and 75% ethanol, v/v) in extracting phenolic compounds from grape pomace. This approach aimed to identify the optimal concentration that provides a balance between solvent polarity and the solubilization capacity for polyphenols.

The results regarding the recovery of phenolic compounds from grape pomace, using a solid–liquid extraction method with solvent solutions at three concentrations (25, 50, and 75%) and pomace-to-solvent ratio of 1:4, are presented for the four grape varieties studied in their respective regions of origin: Murfatlar, Dealu Mare, Ștefănești, and Iași (

Table 2. The phenolic potential of extracts obtained from the varieties Fetească Neagră, Cabernet Sauvignon, Blauer Zweigelt, and Arcas with ethanolic solutions of 25, 50 and 75%.

Polyphenol Parameters of the Extracts	Grape Variety/Ethanolic Solution Used for Extraction
	Feteasca Neagra			Cabernet Sauvignon			Blauer Zweigelt	Arcas
	25%	50%	75%	25%	50%	75%	50%	25%	50%	75%
Total polyphenols (GAE g.L−1), TP	14.3 ± 2.0 ef	18.3 ± 2.8 cde	16.8 ± 2.4 de	11.7 ± 1.8 f	24.8 ± 3.1 a	19.2 ± 2.5 bcd	-	17.3 ± 1.6 de	22.0 ± 2.5 abc	23.1 ± 2.7 ab
Anthocyanins (mg/100 g pomace), AN	406 ± 20 e	616 ± 31 d	622 ± 34 d	296 ± 18 f	722 ± 39 c	572 ± 28 d	302 ± 22 f	603 ± 29 d	851 ± 40 a	791 ± 32 b
Color intensity, CI	6.7 ± 1.2 f	17.1 ± 2.1 d	18.6 ± 3.2 cd	12.3 ± 1.8 e	24.4 ± 3.1 b	22.6 ± 2.9 bc	-	21.5 ± 1.6 bc	29.9 ± 2.7 a	22.8 ± 2.2 bc
Antioxidant activity (%), AA	86.1 ± 6.7 a	88.3 ± 7.2 a	89.8 ± 7.6 a	-	-	-	86.9 ± 8.0 a	91.6 ± 7.8 a	92.2 ± 8.0 a	92.9 ± 8.0 a
Folin Ciocalteau index, 750 nm, FCI	10.6 ± 1.8 e	24.5 ± 2.0 a	20.2 ± 2.0 b	11.4 ± 1.5 e	23.5 ± 1.9 a	18.5 ± 1.7 b	-	13.0 ± 1.0 de	15.6 ± 1.5 bc	17.4 ± 1.7 bc
Total polyphenol index, 280 nm, TPI	85.4 ± 9.2 g	277.4 ± 17.5 ab	228 ± 15.2 d	116.0 ± 10.9 f	261.7 ± 18.0 bc	238.3 ± 16.5 cd	173.8 ± 14.2 e	221.2 ± 20.1 d	291.8 ± 21.2 ab	302.5 ± 25.8 a

Average values ± standard errors (n = 3). Different letters show statistically significant differences among the results at p < 0.05. For the same compound, variants that share a common letter are not significantly different from each other.

). The evaluated parameters included total phenolic compounds, anthocyanins, color intensity, antioxidant activity, the Folin–Ciocalteu index, and the total polyphenol index. For Blauer Zweigelt the extraction was carried out only with the solution of 50% ethanol, therefore a comparison of the extracted polyphenol groups at other concentrations was not made.

The total polyphenol content in the hydroalcoholic extracts ranged between 11.7 and 23.1 GAE g·L⁻¹. The lowest values were recorded for Fetească Neagră (14.35–18.28 GAE g·L⁻¹), while higher values were observed for Arcaș (17.33–22.03 GAE g·L⁻¹) and Cabernet Sauvignon (11.73–24.79 GAE g·L⁻¹). These variations were influenced by the grape variety, origin of the pomace, and the concentration of the solvent mixture (ethanol/water).

The highest extraction efficiency was observed with the 50% hydroalcoholic solution, which yielded peak values of 24.4 GAE g·L⁻¹ for Dealu Mare and 22.03 GAE g·L⁻¹ for Iași, significantly higher than those obtained with the 25% solution. These results confirm the effectiveness of moderate alcohol concentrations for the extraction of polyphenols from grape pomace, consistent with previously reported results in the literature [51].

Anthocyanin content varied significantly, ranging from 296 to 851 mg/100 g pomace. The highest anthocyanin values were obtained with 50% ethanol extractions:

• Arcaș: 851 mg/100 g (highest overall).
• Cabernet Sauvignon: 722 mg/100 g.
• Fetească Neagră: 616 mg/100 g.
• Blauer Zweigelt 302 mg/100 g.

For the 75% ethanol solution, anthocyanin content decreased slightly (by an average of 13.91%) for Arcaş and Cabernet Sauvignon, but not for Fetească Neagră, which showed a minor, non-significant increase of 0.97%.

Color intensity was directly proportional to anthocyanin concentration. The highest color intensity was recorded for Arcaș—29.92 at 50% and 22.82 at 75%—indicating again that the most efficient pigment extraction occurs at moderate alcohol levels.

The analyzed phenolic extracts exhibited high antioxidant activity, ranging between 86.1% and 92.9%. Arcaș showed strong antioxidant potential, with 92.21% activity at 50% ethanol and 92.9% at 75%, averaging 4.1% higher than Fetească Neagră. Similar results were reported by Grosu et al. [52], who found 87.19% antioxidant activity in extracts from Fetească Neagră pomace.

Both the total polyphenol index and the Folin–Ciocalteu index increased significantly at 50% ethanol concentration, suggesting an effective and comprehensive extraction of a broad spectrum of phenolic compounds. These findings highlight the importance of using moderate ethanol concentrations to optimize the extraction process and enhance the release of polyphenols from the grape pomace matrix.

3.2. Correlation of Phenolic Parameters Obtained in Hydroalcoholic Extractions

Pearson correlation analysis (Figure 2) showed strong positive correlations (close to 1) between the phenolic parameters of the hydroalcoholic extracts obtained from the pomace of the studied grape varieties. The correlation coefficients were calculated for the variables: total polyphenols (TP), anthocyanins (AN), color intensity (CI), antioxidant activity (AA), Folin–Ciocalteau index (FCI), and total polyphenol index (TPI).

Very strong positive correlations (values > 0.800) were obtained between total polyphenols (TP) and anthocyanins (AN), color intensity (CI), Folin–Ciocalteau index (FCI), and total polyphenol index (TPI), indicating a close relationship between these parameters and an efficient extraction of phenolic compounds. There is a very strong correlation of 0.900 between anthocyanins (AN) and color intensity (CI).

Although all extracted polyphenols showed antioxidant activity, expressed by the DPPH radical scavenging capacity, no direct and significant correlation was observed between the total polyphenol content (PT) and the antioxidant activity (AA). The Pearson correlation even indicated a weak negative association between these variables, suggesting that the presence of a large amount of phenolic compounds does not automatically imply an increase in antioxidant activity. However, the absence of a direct correlation between the total polyphenol content (PT) and the antioxidant activity (AA) can be rather explained by a saturation effect of the DPPH method, also previously reported by Brand-Williams et al. [49], according to which, at high concentrations of antioxidants, the DPPH reagent exhausts its reaction capacity.

3.3. Quality Parameters of Control and Phenolic-Enriched Musts

The main quality parameters determined for the control and enriched musts are included in

Table 3. Quality parameters of control musts (Mc) and musts enriched with phenolic concentrate (Mep) extracted with 50% ethanolic solution.

Chemical Parameters of the Extracts	Grape Variety/Type o Must
	Feteasca Neagra		Cabernet Sauvignon		Blauer Zweigelt		Arcas
	Mc	Mep	Mc	Mep	Mc	Mep	Mc	Mep
Sugar (g.L−1)	232.2 ± 10.1 ab	227.5 ± 12.4 ab	245.5 ± 14.8 a	230.0 ± 11.8 ab	230.9 ± 11.2 ab	222.1 ± 10.9 b	229.8 ± 11.0 ab	218.1 ± 9.5 b
Total acidity (g.L−1) as tartaric acid	4.94 ± 0.4 b	4.51 ± 0.3 b	4.96 ± 0.4 b	4.51 ± 0.2 b	5.13 ± 0.5 b	4.62 ± 0.3 b	6.31 ± 0.5 a	6.23 ± 0.5 a
pH	3.89 ± 0.2 a	3.89 ± 0.1 a	3.94 ± 0.1 a	3.92 ± 0.2 a	3.73 ± 0.3 ab	3.74 ± 0.3 ab	3.32 ± 0.2 b	3.32 ± 0.3 b
Polyphenols (g.L−1)	4.69 ± 1.3 a	5.59 ± 0.6 a	2.01 ± 0.1 b	2.27 ± 0.1 b	5.44 ± 1.4 a	5.72 ± 1.3 a	1.91 ± 0.9 b	4.02 ± 1.0 a

Average values ± standard errors (n = 3). Different letters show statistically significant differences among the results at p < 0.05. For the same compound, variants that share a common letter are not significantly different from each other.

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The sugar concentrations in the musts used were relatively similar across the analyzed grape varieties, ranging from 222.1 g· L⁻¹ to 245.5 g ·L⁻¹. In all varieties studied (Cabernet Sauvignon, Fetească Neagră, Blauer Zweigelt, and Arcaș) the control musts had higher sugar concentrations compared to the musts enriched with grape pomace extract. This difference is attributed to a natural dilution effect caused by the addition of phenolic extract.

The total acidity of the musts ranged from 4.51 to 6.31 g ·L⁻¹, with the highest value recorded for Arcas grown in Iasi. The variability in total acidity was primarily influenced by the genetic factor (grape variety) and, to a lesser extent, by the pedoclimatic conditions of each wine region. The addition of concentrated phenolic extract did not result in a significant reduction in total acidity, with an average decrease of just 7.42%.

The pH values ranged from 3.32 to 3.94, indicating a mildly acidic profile for most samples. This level of acidity contributes to flavor balance, chemical stability, and microbiological safety. Notably, the Arcaș variety exhibited the lowest pH value (3.32) in both the control and enriched samples, indicating a more pronounced acidity compared to the other varieties.

The polyphenol concentration in the control musts showed significant variability, ranging from 1.91 g· L⁻¹ to 5.44 g· L⁻¹, a variation attributed to the specific biological potential of each grape variety. It is important to note that each varietal must was enriched with phenolic extract derived from the pomace of the same variety.

The addition of concentrated phenolic extract led to a significant increase in polyphenol content, with values ranging from 2.27 to 5.72 g· L⁻¹, corresponding to an average increase of 36.9%. Differences in the composition and polyphenol content among grape varieties are largely determined by their specific biology, particularly genetic factors that regulate the expression of genes involved in the biosynthesis of phenolic compounds. Equally, these variations can be influenced by climatic conditions such as temperature, sunlight, and humidity, which modulate the synthesis and accumulation of phenolic compounds. According to Crupi et al. [53], the polyphenolic profile of grape pomace varies significantly depending on the grape variety and climatic conditions, with notable differences in anthocyanin and flavonoid concentrations among varieties. These variations are influenced by the interaction between the harvest year and variety, as well as climatic factors like temperature and solar radiation, which regulate phenolic biosynthesis. Additionally, the geographical region, through edaphic characteristics (such as soil texture and composition) and the microclimate of the cultivation site (including altitude, temperature, and local solar radiation), plays a crucial role in determining the biochemical composition of grapes, affecting the phenolic profile and aromatic properties of the resulting products [54]. As this study involved four different grape varieties from four distinct regions, an in-depth analysis of the specific causes underlying the total polyphenol content in the grape pomace was not within the scope of our objectives. However, a comparative analysis of individual phenolic compounds in both the extracts and the final enriched products was conducted.

3.4. Individual Phenolic Compounds in Control and Phenolic-Enriched Musts

The phenolic profiles of both control and enriched musts were determined using UHPLC-HRMS chromatography, with results presented in

Table 4. Individual phenolic compounds in control musts (Mc) and musts enriched with phenolic concentrates (Mep).

		Feteasca Neagra		Cabernet Sauvignon		Blauer Zweigelt		Arcas
		Mc	Mep	Mc	Mep	Mc	Mep	Mc	Mep
Phenolic acids (mg·L−1)	gallic acid	0.63 ± 0.03 e	10.25 ± 0.54 a	0.81 ± 0.04 e	0.96 ± 0.05 e	2.12 ± 0.21 d	5.53 ± 0.30 b	0.15 ± 0.01 f	4.01 ± 0.32 c
	3,4-dihydroxybenzoic acid	0.34 ± 0.02 f	3.00 ± 0.15 a	0.68 ± 0.03 e	0.70 ± 0.03 e	0.83 ± 0.05 d	2.05 ± 0.10 b	0.24 ± 0.01 f	1.12 ± 0.06 c
	2,5-dihydroxybenzoic acid	0.09 ± 0.01 c	0.14 ± 0.01 b	0.11 ± 0.01 c	0.16 ± 0.01 b	0.42 ± 0.03 a	0.40 ± 0.02 a	0.05 ± 0.01 d	0.06 ± 0.01 d
	4-dihydroxybenzoic acid	0.62 ± 0.05 b	0.26 ± 0.02 e	0.45 ± 0.03 c	0.37 ± 0.02 d	0.42 ± 0.03 cd	0.68 ± 0.05 a	0.14 ± 0.01 f	0.19 ± 0.01 f
	caffeic acid	0.66 ± 0.05 g	0.44 ± 0.03 h	3.07 ± 0.15 a	2.27 ± 0.11 d	2.50 ± 0.12 c	2.85 ± 0.15 b	1.60 ± 0.08 e	0.92 ± 0.04 f
	syringic acid	2.26 ± 0.12 f	58.71 ± 2.12 a	7.76 ± 0.45 e	9.34 ± 0.58 e	11.53 ± 0.56 d	26.65 ± 1.10 c	2.46 ± 0.10 f	37.88 ± 1.30 b
	p-coumaric acid	0.86 ± 0.04 d	1.18 ± 0.06 c	0.39 ± 0.02 e	0.39 ± 0.02 e	1.65 ± 0.07 a	1.48 ± 0.04 b	0.21 ± 0.01 f	0.36 ± 0.02 e
	chlorogenic acid	2.93 ± 0.10 d	6.36 ± 0.22 a	4.90 ± 0.25 b	3.82 ± 0.15 c	1.89 ± 0.09 e	3.19 ± 0.19 d	1.62 ± 0.08 f	0.75 ± 0.04 g
	ellagic acid	0.19 ± 0.01 bc	0.56 ± 0.03 a	0.17 ± 0.01 bc	0.15 ± 0.01 cd	0.59 ± 0.04 a	0.58 ± 0.05 a	0.12 ± 0.01 d	0.21 ± 0.02 b
	abscisic acid	0.53 ± 0.03 c	0.51 ± 0.04 c	0.55 ± 0.03 bc	0.54 ± 0.02 bc	0.61 ± 0.04 b	0.61 ± 0.03 b	0.51 ± 0.02 c	1.00 ± 0.07 a
Flavanols (mg·L−1)	catechins	8.07 ± 0.42 e	9.69 ± 0.51 d	4.52 ± 0.20 f	3.21 ± 0.18 g	15.51 ± 0.56 a	14.30 ± 0.54 b	1.29 ± 0.10 h	12.57 ± 0.62 c
	epicatechin	2.25 ± 0.12 d	3.37 ± 0.14 b	0.64 ± 0.04 e	0.46 ± 0.04 e	2.34 ± 0.10 d	2.83 ± 0.14 c	0.02 ± 0.01 f	6.66 ± 0.32 a
Flavones (mg·L−1)	taxifolin	0.13 ± 0.01 c	0.17 ± 0.01 b	0.05 ± 0.01 d	0.12 ± 0.01 c	0.02 ± 0.01 e	0.39 ± 0.02 a	0.03 ± 0.01 de	0.13 ± 0.01 c
	vitexin	0.09 ± 0.01 e	0.55 ± 0.03 b	0.05 ± 0.01 fg	0.06 ± 0.01 ef	0.15 ± 0.01 d	0.24 ± 0.02 c	0.02 ± 0.301 g	0.91 ± 0.03 a
	rutin	≤0.023	0.10 ± 0.01 c	0.93 ± 0.05 a	0.96 ± 0.05 a	0.03 ± 0.01 d	≤0.023	0.02 ± 0.01 d	0.30 ± 0.02 b
	kaempferol	0.20 ± 0.02 d	0.34 ± 0.03 c	0.16 ± 0.01 de	0.10 ± 0.01 ef	1.70 ± 0.08 b	1.80 ± 0.09 a	0.03 ± 0.01 f	0.04 ± 0.01 f
	quercitin	0.19 ± 0.01 b	0.56 ± 0.03 a	0.17 ± 0.01 bc	0.15 ± 0.01 cd	0.59 ± 0.02 a	0.58 ± 0.03 a	0.12 ± 0.01 d	0.20 ± 0.02 b
Dihydrocalcones (mg·L−1)	phlorizin	0.68 ± 0.04 c	0.61 ± 0.04 d	0.41 ± 0.03 e	0.44 ± 0.03 e	1.55 ± 0.07 a	1.37 ± 0.05 b	0.23 ± 0.01 g	0.32 ± 0.02 f
	phloretin	0.01 ± 0.01 b	0.03 ± 0.01 a	≤0.008	≤0.008	0.02 ± 0.01 ab	0.03 ± 0.01 a	0.01 ± 0.01 b	0.01 ± 0.01 b
Flavonoids (mg·L−1)	apigenin	0.09 ± 0.01 a	0.03 ± 0.01 b	0.03 ± 0.01 b	0.03 ± 0.01 b	≤0.024	0.04 ± 0.01 b	0.03 ± 0.01 b	≤0.024
	pinocembrin	0.03 ± 0.01 b	≤0.024	≤0.024	≤0.024	≤0.024	≤0.024	0.05 ± 0.01 a	≤0.024
	crisin	0.16 ± 0.01 b	0.03 ± 0.01 c	0.03 ± 0.01 c	≤0.025	≤0.025	≤0.025	0.27 ± 0.02 a	≤0.025
	galangin	0.05 ± 0.01 b	≤0.024	≤0.024	≤0.024	≤0.024	≤0.024	0.12 ± 0.02 a	≤0.024
Stilbens (mg·L−1)	trans-resferatrol	0.03 ± 0.01 e	0.03 ± 0.01 e	0.03 ± 0.01 e	0.38 ± 0.02 c	0.64 ± 0.04 b	1.40 ± 0.06 a	0.03 ± 0.01 e	0.27 ± 0.02 d
	polydatin	0.40 ± 0.02 c	0.30 ± 0.02 d	0.17 ± 0.01 e	0.10 ± 0.01 f	0.93 ± 0.06 b	1.11 ± 0.05 a	0.14 ± 0.01 ef	0.18 ± 0.02 e
Anthocyanins (mg·L−1)	Oenin (malvidin-3-O-glucozide)	63.33 ± 3.10 a	37.19 ± 1.74 d	8.12 ± 0.41 f	5.72 ± 0.24 gh	52.84 ± 2.43 b	41.46 ± 1.89 c	3.81 ± 0.15 g	12.44 ± 0.70 e
TOTAL phenolic compounds (mg·L−1)		84.78 ± 3.20 d	134.37 ± 5.26 a	34.01 ± 1.5 e	30.40 ± 1.78 e	98.90 ± 4.50 c	109.54 ± 4.96 b	13.21 ± 0.60 f	80.62 ± 3.78 d

Average values ± standard errors (n = 3). Different letters show statistically significant differences among the results at p < 0.05. For the same compound, variants that share a common letter are not significantly different from each other.

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The analysis quantified a broad range of phenolic compounds, including the following: phenolic acids: gallic, 3,4-dihydroxybenzoic, 2,5-dihydroxybenzoic, 4-dihydroxybenzoic, caffeic, syringic, p-coumaric, chlorogenic, ellagic, and abscisic acids; flavanols: catechin and epicatechin; flavonols: quercetin, taxifolin, rutin, kaempferol, and vitexin; flavonoids: apigenin, pinocembrin, chrysin, and galangin; stilbenes: trans-resveratrol and polydatin; dihydrochalcones: phloretin and phloridzin; and anthocyanins: oenin.

Among the phenolic acids, syringic acid was the predominant compound in the control musts, with concentrations ranging from 2.26 to 11.53 mg·L⁻¹, the highest values being found in the Blauer Zweigelt variety. In the musts enriched with concentrated phenolic extract, syringic acid content increased significantly, ranging from 9.34 to 58.71 mg·L⁻¹. The largest increases were recorded for Fetească Neagră (29-fold) and Arcaș (18-fold).

Gallic acid also showed notable increases: it ranged from 0.19 to 2.12 mg·L⁻¹ in control musts and from 0.96 to 10.25 mg·L⁻¹ in enriched musts.

Flavanols represented the dominant class of phenolic compounds across all variants. Among them, catechin reached the highest concentrations, with 15.51 mg·L⁻¹ in Blauer Zweigelt, 8.07 mg·L⁻¹ in Fetească Neagră, 4.52 mg·L⁻¹ in Cabernet Sauvignon, and 1.12 mg·L⁻¹ in Arcaș. In the phenolic-enriched musts, catechin content increased 11-fold in Arcaș, while in the other varieties (Cabernet Sauvignon and Blauer Zweigelt), a slight decrease in catechin was observed.

Within the flavonol class, kaempferol and quercetin were identified as predominant. Kaempferol concentrations in control musts ranged from 0.03 to 0.20 mg·L⁻¹, with the highest levels found in Fetească Neagră. In enriched musts, kaempferol content showed an average increase of approximately 7.2%.

Quercetin ranged from 0.12 to 0.59 mg·L⁻¹ in control musts, and from 0.17 to 0.58 mg·L⁻¹ in enriched musts, indicating a notable enhancement of the phenolic profile. Among stilbenes, phloridzin—though not a predominant compound in grapes or grape pomace—was detected at the highest concentrations in control musts, ranging from 0.23 to 1.55 mg·L⁻¹, with the highest values again in Blauer Zweigelt.

The most extensively studied stilbene, trans-resveratrol, ranged between 0.03 and 1.40 mg·L⁻¹, with significant increases in the enriched musts of Cabernet Sauvignon and Blauer Zweigelt.

Analyzing the total content of individually quantified phenolic compounds, regardless of their phenolic class, the hierarchy for control musts was as follows:

• Blauer Zweigelt > Fetească Neagră > Cabernet Sauvignon > Arcaș.
• In contrast, for the phenolic-enriched musts, the hierarchy was
• Fetească Neagră > Blauer Zweigelt > Arcaș > Cabernet Sauvignon.

These results highlight the significant influence of both grape variety and phenolic extract addition on the phenolic composition of the analyzed musts.

4. Conclusions

The efficient management of pomace, the main by-product of the grape juice and wine production, remains a significant challenge for the wine industry due to its ecological and economic implications. In recent years, there has been a marked increase in research focused on the sustainable valorization of this by-product, driving the development of integrated strategies aimed at utilizing the solid fraction that remains after separating the grape must or wine. This cascade approach opens up diverse application opportunities across the food, cosmetic, and pharmaceutical industries.

This study highlights the potential of grape pomace as a valuable source of polyphenolic compounds with high antioxidant activity, emphasizing its possible reuse across various industries, particularly the food industry in this case.

The results demonstrated that grape pomace can be repurposed for polyphenol extraction, thereby reducing viticultural waste in an eco-friendly manner, while simultaneously producing a functional grape juice with enhanced nutritional value.

Solid–liquid extraction using hydroalcoholic solutions containing 50% ethanol at a 1:4 pomace-to-solvent ratio proved to be the most efficient method for recovering polyphenols from grape pomace, while also minimizing water and solvent consumption.

Regarding must enrichment with concentrated phenolic extracts, significant increases were observed in key bioactive compounds such as syringic acid, gallic acid, and trans-resveratrol, thus emphasizing the potential of this newly proposed practice to enhance the phenolic profile of grape musts.

The phenolic profile varied significantly depending on the grape variety, with Fetească Neagră must exhibiting the highest phenolic content after enrichment, followed by Blauer Zweigelt, Arcaș, and Cabernet Sauvignon.

These findings suggest that the addition of concentrated phenolic extracts not only improves the content of bioactive compounds, but also positively influences the quality and functional properties of the final product, thereby increasing its value in terms of health benefits. By upcycling the grape pomace from the same grapes used for must production, the resulting juices are more sustainable, reducing waste and raw material inputs, while offering clean-label products with enhanced natural flavor and added health benefits.

To support the industrial application of this technology, further research is needed to optimize the extraction, separation, and purification processes of phenolic compounds, with a strong emphasis on sustainability and energy efficiency. Although a detailed economic analysis of implementation costs was beyond the scope of this study, it remains a promising area for future research. Assessing both the economic and ecological impacts will be crucial for the practical validation of proposed solutions and for accelerating their adoption within the industry.

From a managerial perspective, the valorization of pomace requires the adoption of sustainable economic models in which winery and agri-food sector leaders embrace “zero waste” strategies. This entails not only investments in advanced extraction equipment and technologies but also fostering intersectoral collaborations to develop innovative value-added products. The successful implementation of such strategies can offer a significant competitive advantage for producers committed to sustainability and operational efficiency.