From Vineyard to Brewery: A Review of Grape Pomace Characterization and Its Potential Use to Produce Low-Alcohol Beverages

Abstract

The production of low-alcohol beverages is an important world trend due to concerns about health and well-being. The use of agro-industrial residues, such as grape pomace, to produce bioactive and diverse beverages is highly acceptable to consumers. It is an eco-friendly approach that contributes to sustainability and a circular economy. This mini review highlights the composition of grape pomace and its emerging role as a fermentation substrate, emphasizing its potential to contribute to sustainable beverage innovation. In addition, we discussed using non-conventional yeasts to produce beer with different aromas, flavors, and low alcoholic content, as well as the possibility of using a vast diversity of substrates during fermentation, including grape pomace. Different yeasts and substrates bring new opportunities to the market for brewery industries and other products.

1. Introduction

The production of wine is one of the most ancient and culturally significant biotechnological processes, with a global output surpassing 250 million hectoliters annually [1]. This process generates substantial by-products, most notably grape pomace, which is a mixture of grape skins, seeds, and stems remaining after the extraction of grape juice or during vinification. Depending on the winemaking method, grape pomace accounts for 15–30% of the total weight of processed grapes [2]. The management of this by-product presents a significant challenge and opportunity within the wine industry. Globally, millions of tons of grape pomace are generated each year, primarily concentrated in major wine-producing countries such as Italy, France, and Spain, which collectively account for over half of the world’s wine production [3].

In Latin America, wine production is also significant, with countries like Argentina, Chile, and Brazil playing crucial roles. Argentina and Chile are among the top ten wine producers globally, while Brazil has emerged as a dynamic player, particularly in sparkling wine production. Only in Brazil, over 800 million liters of wine were produced in 2023, generating approximately 200,000 tons of grape pomace [4]. This by-product is often underutilized despite its potential for diverse applications. Brazil’s wine production is concentrated in the southern regions, particularly Rio Grande do Sul, which accounts for nearly 90% of the national output. The subtropical climate, combined with specific viticultural techniques, produces high-quality grapes, primarily from varieties such as Isabel, Bordo, and Moscato [5]. This production contributes to the local economy and presents opportunities for innovation in managing and valorizing grape pomace. Increasingly, Brazilian wineries and research institutions are exploring the potential of this by-product for sustainable applications.

1.1. Grape Pomace Composition and Variability

Historically considered waste, grape pomace has increasingly been recognized for its potential in diverse applications, including its use as a substrate in fermentative processes [6]. Current valorization strategies range from agricultural applications, such as composting and animal feed, to more sophisticated uses, including the extraction of bioactive compounds, bioenergy production, and food fortification [7]. Despite these interesting properties, significant amounts of grape pomace remain underutilized, underscoring the need for innovative reuse strategies. The composition of grape pomace is highly variable, depending on grape variety, growing conditions, and vinification techniques. However, it consistently contains high levels of phenolic compounds, dietary fibers, proteins, residual sugars, minerals, and other micronutrients [2]. These constituents make grape pomace a nutritionally rich and biochemically diverse substrate, well suited for fermentation processes to produce novel beverages or improve existing ones. Several key components are consistently present despite these variations in composition, as shown in Table 1 and described in more details below.

(a)

Phenolic Compounds: Grape pomace is a rich source of phenolic compounds, including flavonoids, tannins, and anthocyanins. These compounds are predominantly found in skins and seeds, contributing to the pomace’s antioxidant properties. Red grape varieties, such as Cabernet Sauvignon and Merlot, tend to have higher phenolic concentrations than white varieties like Chardonnay or Sauvignon Blanc [8]. Polyphenols are the most studied group of bioactive compounds in grape pomace, primarily consisting of flavonoids (e.g., anthocyanins, flavan-3-ols, flavonols) and non-flavonoids (e.g., phenolic acids, stilbenes). These compounds are renowned for their antioxidant properties, which are critical in combating oxidative stress and reducing the risk of chronic diseases, including cardiovascular diseases, diabetes, and certain cancers [9]. The polyphenolic profile of grape pomace is influenced by grape variety, cultivation conditions, and vinification processes. For instance, red grape pomace is particularly rich in anthocyanins, which impart strong antioxidant and anti-inflammatory effects [10]. Incorporating these polyphenols into functional beverages, such as low-alcohol options, can enhance their health-promoting properties, while also improving sensory characteristics like color and astringency.

(b)

Dietary Fibers: Grape pomace is a valuable source of dietary fibers, which comprises both insoluble fractions (e.g., cellulose, hemicellulose, lignin) and soluble fractions (e.g., pectin, gums) [11]. Dietary fibers promote gut health by improving bowel regularity and serving as a substrate for beneficial gut microbiota, leading to the production of short-chain fatty acids (SCFAs) that support intestinal and metabolic health [12]. These fibers, found in the skins and stems, contribute to its potential as a functional food ingredient [11]. Moreover, fiber-enriched diets are associated with lower cholesterol levels, improved glycemic control, and reduced risks of obesity and type 2 diabetes [13]. The addition of grape pomace to low-alcohol beverages may offer a novel strategy to increase dietary fiber intake while leveraging its other nutritional benefits.

(c)

Residual Sugars: The remaining sugars in grape pomace, including glucose and fructose, are by-products of incomplete fermentation. These sugars provide an excellent substrate for secondary fermentation processes, such as those used in producing low-alcohol beverages or kombucha [14,15].

(d)

Proteins and Minerals: Although grape pomace is not as well studied for its micronutrient content as for its polyphenols and fibers, it contains several vitamins (e.g., vitamin C, vitamin E, and B-complex vitamins) and minerals (e.g., potassium, calcium, magnesium). These nutrients contribute to the overall antioxidant activity and metabolic functions in the body [16]. Grape pomace contains tiny amounts of proteins and essential minerals such as potassium, calcium, and magnesium, which further enhance its nutritional value [17], making it an interesting source of nutrition for microorganisms. Vitamin C, for instance, works synergistically with polyphenols to enhance antioxidant capacity, while vitamin E’s lipid-soluble nature protects cell membranes from oxidative damage. Minerals like potassium are vital for maintaining electrolyte balance and cardiovascular health [13].

The functional properties of grape pomace make it an excellent ingredient for developing low-alcohol beverages with added health benefits. Polyphenols can function as natural preservatives and color stabilizers, while dietary fiber can improve the texture and provide a “functional food” label appeal. Additionally, the antioxidant and anti-inflammatory activities of grape pomace components can align with consumer demands for beverages that support wellness.

Emerging studies also suggest that incorporating grape pomace into beverage formulations can mitigate the off flavors associated with alcohol reduction while imparting a pleasant complexity to the sensory profile [18,19,20]. This dual role of enhancing both health benefits and sensory attributes underscores the versatility of grape pomace as a sustainable and functional ingredient.

1.2. Differences Among Grape Varieties

Grape pomace extract (GPE) demonstrates substantial variability depending on the grape variety, cultivation practices, and winemaking techniques, influencing its chemical profile and applications. Red grape varieties, such as Cabernet Sauvignon, Merlot, and Syrah, typically contain higher levels of phenolic compounds such as flavonoids, tannins, and anthocyanins due to prolonged skin contact during fermentation [21]. These compounds impart strong antioxidant properties, making them valuable for food preservation and as substrates for enzyme production in fermentation processes [22]. For example, pomace from Cabernet Sauvignon or Syrah contains elevated levels of antioxidants and pigments [2]. In contrast, white grape varieties, such as Chardonnay and Sauvignon Blanc, often have lower phenolic content but may retain higher levels of certain organic acids and sugars that are useful in microbial fermentation for ethanol or lactic acid production [23,24]. The absence of prolonged skin contact during white wine production accounts for these differences, given that white wines are typically fermented without skin contact, limiting the extraction of these compounds.

Table 1. Composition of grape pomace extract.

Constituent	Quantity (Dry Weight)	Application in Fermentation Processes	References
Phenolic Compounds	50–70 g/kg	Antioxidants in fermented foods, substrate for enzyme production in fermentation.	[2,8]
Fibers	35–60%	Prebiotics in kombucha and kefir fermentation, support for immobilization of fermentative cells.	[11]
Residual Sugars	5–10%	Substrate for ethanol, lactic acid, and other metabolite production in microbial fermentations.	[15,17]
Minerals	5–10%	Nutritional supplement in fermentation media to enhance microbial growth.	[17]
Proteins	10–15%	Nitrogen source in alcoholic fermentation and amino acid production by microorganisms.	[17,24]

Table 1. Composition of grape pomace extract.

Constituent	Quantity (Dry Weight)	Application in Fermentation Processes	References
Phenolic Compounds	50–70 g/kg	Antioxidants in fermented foods, substrate for enzyme production in fermentation.	[2,8]
Fibers	35–60%	Prebiotics in kombucha and kefir fermentation, support for immobilization of fermentative cells.	[11]
Residual Sugars	5–10%	Substrate for ethanol, lactic acid, and other metabolite production in microbial fermentations.	[15,17]
Minerals	5–10%	Nutritional supplement in fermentation media to enhance microbial growth.	[17]
Proteins	10–15%	Nitrogen source in alcoholic fermentation and amino acid production by microorganisms.	[17,24]

In Brazil, hybrid varieties such as Isabel and Bordo are widely used for winemaking. These varieties produce pomace with moderate phenolic content but are often richer in aromatic precursors, making them suitable for innovative fermentation applications [5].

Environmental factors also contribute to the variability of GPE composition. Soil composition, temperature, and water availability during grape cultivation can significantly influence the accumulation of minerals like potassium, calcium, and magnesium in pomace [25]. These minerals serve as micronutrients in fermentation media, enhancing the growth and activity of beneficial microorganisms. Additionally, cultivation practices such as organic farming may result in higher fiber and antioxidant levels compared to conventional methods [26]. The variability extends further due to differences in winemaking techniques. For example, mechanical pressing often retains more residual sugars in the pomace, while thermal vinification processes can degrade certain heat-sensitive phenolic compounds, reducing their bioavailability [11]. Moreover, seed retention during winemaking can elevate protein levels in the pomace, providing an excellent nitrogen source for microbial processes [24].

These compositional differences underscore the need for tailored utilization of GPE in fermentation, biotechnological applications, and functional food production. Recent studies have explored the potential of grape pomace as a substrate for producing fermented beverages, including kombucha, kefir, and low-alcohol drinks, leveraging its nutrient profile and bioactive compounds [27]. The fermentation of grape pomace valorizes this by-product and opens avenues for creating functional drinks with health benefits, addressing both environmental and consumer demands. The chemical composition of GPE could make a suitable alternative medium for the growth of various microorganisms since it contains fermentable reducing sugars such as glucose, fructose, and yeast-assimilable nitrogen (YAN) that can fulfill the nutritional requirements for microbial growth [28].

2. Low-Alcohol and Alcohol-Free Beverages

Over the last decade, the rising demand for low-alcohol and alcohol-free beverages (LABs) reflects significant changes in consumer preferences and societal attitudes toward health and wellness. This trend has been driven by health-conscious consumers seeking options that allow them to enjoy social occasions without the adverse effects of alcohol consumption [29]. Innovations in brewing and fermentation technologies have enabled the production of flavorful low-alcohol beers, wines, and spirits, addressing earlier challenges of compromised taste profiles [30]. Market studies indicate a steady annual growth rate in the low-alcohol and alcohol-free beverage sector, with increased adoption in countries where public health campaigns have raised awareness about the risks associated with excessive alcohol consumption [31]. Millennials and Z Generation are prominent contributors to this trend, valuing moderation, and lifestyle alignment with health goals [32]. Additionally, government policies, such as reduced excise duties for low-alcohol products, have encouraged manufacturers to innovate in this category [31]. Low-alcohol beverages have expanded their appeal through functional enhancements, including probiotics, vitamins, and adaptogens, catering to the dual desire for indulgence and nutritional benefits. This evolution diversifies product offerings and makes these beverages key players in the broader functional food and beverage industry. The growing popularity of these products suggests they will remain a significant focus of innovation in the beverage sector for years to come.

Producing low-alcohol beverages involves various techniques to reduce ethanol content while preserving sensory quality. One standard method used to obtain these beverages is arrested or limited fermentation, where the process is deliberately stopped before completion by controlling temperature and time of fermentation, resulting in beverages with lower alcohol content but higher residual sugars [33]. Another approach involves biological methods, such as using low-alcohol-producing yeast strains or halting fermentation by heating the wort [34]. Physical dealcoholization techniques, including vacuum distillation and membrane-based processes like reverse osmosis, are also employed to remove alcohol from fully fermented beverages [35]. Each method presents unique challenges and impacts on the final product’s flavor and quality.

The functional beverage industry is experiencing a paradigm shift driven by consumer demand for health-promoting products with added nutritional and bioactive properties. Among the diverse range of innovations, the incorporation of grape pomace and the application of novel fermentation techniques have garnered significant attention due to their potential to enhance the health benefits and sensory attributes of beverages.

Biotechnological advancements have introduced genetically modified yeast or non-Saccharomyces yeast strains with limited alcohol-producing capacity. These strains can ferment sugars into non-ethanol metabolites, such as glycerol and organic acids, thereby enhancing the complexity of low-alcohol beverages [36]. Additionally, blending techniques are employed to dilute alcoholic beverages with non-alcoholic bases or to mix alcohol-free and full-strength beverages to achieve desired alcohol levels [37]. This approach is often combined with flavor optimization strategies to ensure consumer acceptance. Each technique offers unique advantages and challenges, and their selection frequently depends on the type of beverage, production scale, and desired sensory attributes.

2.1. Grape Pomace as a Functional Ingredient

Grape pomace, a by-product of winemaking, is a rich source of bioactive compounds, including polyphenols, dietary fiber, and residual sugars as mentioned above [38]. Its incorporation into functional beverages presents a sustainable and cost-effective approach to valorizing this agricultural by-product. The polyphenolic content of grape pomace exhibits potent antioxidant, anti-inflammatory, and antimicrobial properties, making it an ideal candidate for developing health-oriented drinks such as probiotic beverages and antioxidant-enriched formulations.

In probiotic beverages, grape pomace can serve as a substrate to support the growth and activity of beneficial microorganisms such as Lactobacillus and Bifidobacterium species. Studies have shown that polyphenols can enhance the viability of probiotics by providing a protective effect against oxidative stress and gastrointestinal conditions [38]. Furthermore, the fiber content of grape pomace may function as a prebiotic, further promoting gut health through the modulation of the gut microbiota.

Beyond probiotics, the antioxidant properties of grape pomace make it a valuable component in beverages targeting oxidative-stress-related health issues, such as cardiovascular diseases and aging. Formulating functional drinks with grape pomace also aligns with sustainability goals, as it reduces agricultural waste while providing health-promoting products.

Advancements in fermentation technology are transforming the beverage landscape. Controlled fermentation using specific yeast strains or bacterial cultures allows for precise modulation of flavor, aroma, and nutritional profiles. For instance, non-Saccharomyces yeasts, such as Saccharomycodes ludwigii or Torulaspora delbrueckii, are increasingly used in beverage production due to their ability to produce complex flavor profiles and contribute with bioactive metabolites [39].

Similarly, the use of specific lactic acid bacteria strains in fermentation can enhance the production of bioactive compounds, including exopolysaccharides and short-chain fatty acids. These compounds not only improve the sensory attributes of beverages but also provide health benefits such as improved gut health and immune support. The integration of grape pomace into such fermentation systems can further amplify these effects, creating synergistic interactions between the bioactive compounds in the pomace and the metabolic activity of the microorganisms [40].

Recent advancements in precision fermentation allow for the tailoring of metabolic pathways to maximize the extraction and bioavailability of key compounds from grape pomace. For example, adaptive fermentation methods involving co-cultures of yeasts and bacteria enable the production of beverages with enhanced functional properties, such as increased antioxidant capacity and gut-modulating effects.

The potential of grape pomace extends beyond functional and probiotic beverages into the realm of low-alcohol and non-alcoholic drinks. The residual sugars and organic acids in grape pomace can contribute to balanced sweetness and acidity, providing a natural flavor profile that aligns with consumer preferences for clean-label products. Additionally, the incorporation of grape pomace into non-alcoholic fermented beverages, such as kombucha or kefir, can enhance their functional properties while introducing novel sensory dimensions [41].

Emerging research suggests that controlled fermentation techniques can be used to develop low-alcohol beverages with enhanced retention of polyphenolic compounds from grape pomace. By optimizing fermentation parameters, it is possible to produce beverages with reduced ethanol content while preserving the health benefits associated with the bioactive constituents of grape pomace [39]. This approach not only caters to the growing demand for healthier alcohol alternatives but also expands the market potential for grape pomace-derived products.

Grape pomace is also being explored as an ingredient in functional water, energy drinks, and botanical infusions. Its compatibility with other natural ingredients, such as herbal extracts and citrus fruits, offers exciting opportunities to create multi-functional, innovative beverages that cater to diverse consumer preferences. The integration of grape pomace into functional beverages, coupled with the use of novel fermentation techniques, represents a promising avenue for innovation in the beverage industry. These strategies not only address consumer demands for sustainable and health-promoting products but also provide an opportunity to explore the versatility of grape pomace in diverse beverage categories. Future research should focus on optimizing processing and fermentation parameters to maximize the functional and sensory benefits of grape pomace, thereby unlocking its full potential in the global market.

2.2. Low-Alcohol Wine

The production of low- and non-alcoholic wine has gained significant importance over the past decade due to shifting consumer preferences toward healthier lifestyles and the demand for beverages that align with social, cultural, and regulatory restrictions [42]. This trend has spurred innovations in winemaking processes that aim to reduce or eliminate ethanol content while maintaining the sensory qualities and health benefits associated with traditional wine. Low-alcohol wine is crafted by lowering the alcohol content in regular wine or employing alternative vinification techniques that limit alcohol production [43].

Biological and physical methods are the two primary approaches for producing low- and non-alcoholic wines. Biological methods include interrupted fermentation, where yeast activity is halted before significant alcohol production occurs [33]. This can be achieved by reducing fermentation temperatures or adding chemical inhibitors. Although better suited for near-complete fermentations, the addition of sulfites and subsequent potassium sorbate will inhibit yeast growth and stabilize the wine [44], preserving the natural sugars of the grapes and enhancing sweetness [45,46]. Another biological method involves using genetically modified or non-Saccharomyces yeast strains with limited ethanol production, which can also improve the flavor profile of the wine [47]. Physical methods involve the removal of ethanol from fully fermented wine through techniques such as vacuum distillation, reverse osmosis, and spinning cone columns [48]. Vacuum distillation operates under low pressure and temperature, reducing the risk of thermal degradation of volatile compounds that contribute to the aroma and taste of the wine [49]. Reverse osmosis employs selective membranes to separate ethanol and water from the wine matrix, retaining most flavor compounds. Spinning cone columns, a more advanced technique, allow precise separation of ethanol while concentrating on the wine’s aromatic components [30].

Global interest in low-alcohol wine has grown steadily, driven by European and North American markets, where consumers seek lighter, health-oriented alternatives. Asia and Latin America are also emerging markets, with increasing awareness of low-alcohol options [50]. The advancements in production methods have significantly improved the sensory attributes of low- and non-alcoholic wines, reducing the gap between these products and their traditional counterparts [51]. Additionally, these wines address the requirements of specific populations, such as pregnant women, designated drivers, and those with religious or medical restrictions on alcohol consumption [42]. As consumer demand continues to grow, further innovation in production techniques will enhance the quality and accessibility of these beverages, solidifying their place in the global wine market.

2.3. Low-Alcohol Spirits

The production of low- and non-alcoholic spirits has become a rapidly expanding sector in the beverage industry, driven by changing consumer preferences, health awareness, and regulatory considerations. These products aim to replicate the sensory experience of traditional spirits while significantly reducing or eliminating alcohol content. The challenge lies in achieving the complex flavor profiles characteristic of spirits without the functional contribution of ethanol. The production of low- and non-alcoholic spirits typically involves three primary approaches: distillation, extraction, and blending. The process begins by distilling botanicals, herbs, or fruits in water or ethanol to extract essential oils and flavor compounds. In cases where ethanol is used initially, the alcohol is subsequently removed through reverse osmosis or vacuum distillation. Vacuum distillation operates under reduced pressure, which allows the separation of alcohol at lower temperatures, preserving delicate flavor compounds [45,49]. Non-alcoholic spirits often utilize water-based extraction methods to derive flavors from raw materials. Techniques such as maceration or steam distillation capture volatile aromatic compounds without using ethanol as a solvent. This method suits products targeting complete alcohol elimination [30]. Another common approach involves blending natural flavor extracts, acids, sweeteners, and other functional ingredients. This process aims to recreate the mouthfeel, complexity, and balance typically provided by alcohol. Advances in food science have enabled the development of non-alcoholic spirits with enhanced body and viscosity using non-ethanol-based additives, such as glycerol or xanthan gum [52].

2.4. Global Consumption and Market Trends

The global market for low-alcohol beverages continues to expand, with Euromonitor International predicting a compound annual growth rate (CAGR) of over 7% for LABs (low-alcoholic beverages) through 2026 [53]. This growth reflects increased consumer focus on health and wellness, stricter regulations on alcohol advertising, and cultural shifts toward mindful consumption. Europe leads the LAB market, driven by robust demand for low-alcohol beer, wine, and cider. North America and Asia–Pacific are also key regions, with consumers in these areas increasingly drawn to functional drinks like kombucha and kefir. Latin America, including Brazil, shows growth potential, especially as local ingredients like grape pomace are utilized for innovative product development. Incorporating grape pomace into low-alcohol beverage production aligns with global sustainability goals by reducing food waste and promoting the circular economy. The valorization of grape pomace could offer a competitive advantage for producers, particularly in markets where consumers value eco-friendly and locally sourced products [54].

3. Low-Alcohol Beer: Production and Use of Grape Pomace

Non-alcoholic and low-alcoholic beers (NABLABs) have gained significant traction recently due to growing consumer interest in health-conscious and low-calorie beverages [55]. The global NABLAB market is projected to grow significantly, with Europe and North America leading consumption, followed by increasing interest in Latin America and Asia [56]. This trend underscores the importance of developing innovative approaches to enhance the nutritional and sensory properties of NABLABs to meet diverse consumer expectations. Grape pomace offers a promising solution for producing low-alcohol beer [57].

The increasing demand for low-alcohol beverages, coupled with the growing interest in sustainable practices within the beverage industry, has led to innovative applications of grape pomace, an abundant by-product of winemaking. Recent research has focused on leveraging grape pomace as a raw material for low-alcohol beverages, employing novel fermentation techniques and formulations to enhance their sensory profiles and functional properties. Its rich content of phenolic compounds, fibers, and residual sugars provides an ideal substrate for enhancing nutritional profile and flavor complexity of NABLABs [58,59]. Grape pomace can be incorporated into NABLAB production through co-fermentation or adding pomace extracts during the brewing process (Figure 1). Studies have demonstrated that these methods can provide unique fruity and tannic notes to the beer while enriching it with antioxidants and dietary fibers [18,57,60]. In Brazil, where the craft beer and wine industries are thriving, integrating grape pomace into NABLAB production represents an innovative avenue for sustainable beverage development. Using local by-products, Brazilian brewers can address environmental concerns, reduce waste, and create distinctive products that align with global consumption trends [61]. This approach valorizes grape pomace and expands the potential of NABLAB as a functional beverage, bridging the gap between tradition and innovation. NABLAB production typically involves methods to limit or remove alcohol content while retaining the sensory characteristics of traditional beer. Standard techniques include arrested fermentation, vacuum distillation, reverse osmosis, and blending with non-alcoholic beer [49].

The demand for NABLAB reflects a global shift toward moderation in alcohol consumption, driven by health trends, changing lifestyles, and stricter regulations around alcohol marketing [53]. Restricted fermentation is a method in which the fermentation process is intentionally stopped before significant alcohol content develops. This can be achieved by rapidly cooling the wort, adding sulfur dioxide, or using sterile filtration to remove yeast. This technique preserves residual sugars, giving the beer a naturally sweet taste and a fuller body. However, achieving the desired balance of sweetness and flavor complexity can be challenging and requires precise control of the fermentation parameters [62,63].

Grape pomace can be added during brewing, particularly in the mashing or boiling stages, where its sugars and phenolics can interact with the wort, enhancing flavor and stability [64,65]. Vacuum distillation is a technique that removes alcohol from fully fermented beer by applying heat under reduced pressure. The lowered boiling point of ethanol under vacuum conditions minimizes the loss of volatile aromatic compounds, helping retain the beer’s flavor profile. Although effective, this method requires specialized equipment and can be energy-intensive, making it less accessible for smaller breweries [30]. The alcohol is removed, and the remaining concentrate is diluted with water or other flavoring agents to achieve the final product. This method is particularly valued for preserving the beer’s original taste and aroma. However, it can be costly and time-consuming due to the need for multiple filtration steps [66]. Grape pomace extracts can be introduced post-alcohol removal to restore complexity and contribute additional antioxidants and bioactive compounds [21]. Another common approach is blending regular beer with non-alcoholic beer to achieve a lower alcohol content. This method is straightforward and cost-effective but requires careful selection and blending of the base beers to ensure consistent quality and flavor. It is often used in large-scale industrial production where cost and efficiency are prioritized [37].

In a study published in 2024, researchers explored the use of grape pomace in combination with a kombucha SCOBY (Symbiotic Culture of Bacteria and Yeast) to produce functional beverages. The study demonstrated that the fermentation process significantly enhanced the antioxidant, anti-inflammatory, and anti-diabetic properties of the beverage [15]. Optimizing fermentation parameters, such as temperature, grape pomace concentration, and fermentation duration, resulted in a product that not only possessed desirable bioactive characteristics but also exhibited sensory properties suitable for direct consumption as a functional low-alcohol beverage.

Additionally, the incorporation of grape pomace in craft beers has been studied to enhance both the bioactive and sensory qualities of the beverage. A 2024 study on the inclusion of purple grape pomace during the fermentation of craft beers revealed significant improvements in the technological, sensory, and bioactive attributes of the final product. This formulation offers a promising alternative to traditional beers, providing consumers with a healthier, low-alcohol option with enhanced nutritional benefits [57].

Given the evolving beverage industry, the integration of grape pomace into low-alcohol beverages has garnered significant attention in recent years. New studies have emphasized the use of novel fermentation techniques, such as employing non-Saccharomyces yeasts, which help retain bioactive compounds and enhance the sensory profile of beverages [67], and advancements in extraction technologies have facilitated the incorporation of high-quality polyphenol and dietary fiber fractions from grape pomace into beverage formulations [68]. These innovations not only improve the functional properties of low-alcohol beverages but also align with sustainability and health trends by repurposing winemaking by-products [69].

Further research has highlighted novel strategies for stabilizing bioactive compounds in grape pomace during beverage processing. Encapsulation techniques, such as microencapsulation and spray-drying, have been employed to preserve polyphenols during storage and improve their bioavailability in low-alcohol formulations [47,70]. Additionally, recent product development efforts have focused on blending grape pomace extracts with other functional ingredients, such as prebiotics and probiotics, to create synergistic health benefits in low-alcohol beverages [71].

4. Challenges in the Application of Grape Pomace Extract (GPE) in Fermentation Processes

Grape pomace is a low-value by-product that presents a significant number of high-value-added products. The amount of non-edible residues of grape pomace waste causes environmental pollution, management issues as well as economic loss. Grape pomace is difficult to use in its solid form; however, the grape skin and pulp extract are easily usable. GPE can be prepared by adding hot water in grape pomace followed by stirring and filtration. The utilization of grape pomace extract (GPE) in fermentation processes presents several challenges that must be addressed to optimize its potential as a substrate for producing fermented beverages or biotechnological products [3]. These issues are primarily related to the chemical complexity of GPE, variability in composition, and the potential inhibitory effects of specific compounds. The chemical composition of GPE is highly variable, depending on the grape variety, cultivation conditions, winemaking processes, and extraction methods. This variability affects its fermentability and suitability as a substrate. For example, polyphenols, such as flavonoids, anthocyanins, and tannins, which are abundant in GPE, may vary in concentration and structure. While these compounds contribute to antioxidant activity, they can inhibit microbial growth or interfere with enzymatic activity in fermentation processes [72]. Studies have shown that phenolic compounds can disrupt cell membranes and inhibit the activity of key enzymes in Saccharomyces cerevisiae, the primary yeast used in fermentation [73]. To mitigate these effects, strategies such as dilution, detoxification, or selecting phenol-tolerant yeast strains have been proposed [73,74,75]. Although GPE contains residual sugars, such as glucose and fructose, their concentrations may not always be sufficient for effective fermentation. Additionally, non-fermentable sugars or sugar degradation products (e.g., furfural) can suppress microbial activity [76]. Supplementing GPE with additional fermentable substrates and pre-treating the extract with enzymes such as phospholipases to remove inhibitory compounds are potential solutions [77]. Unfortunately, large-scale production using GPE is still not a reality, despite many studies found in literature.

During fermentation, GPE can produce inhibitory by-products, such as acetic acid and ethanol [78], which can negatively affect microbial viability and fermentation efficiency. These by-products result from the metabolism of sugar and other organic compounds, particularly under suboptimal fermentation conditions [21]. Control of fermentation parameters, including pH, temperature, and inoculum density, is essential to minimize their production [79]. The economic feasibility of using GPE in industrial fermentation remains a challenge. The cost of processing and transporting GPE and its inherent variability can limit its scalability for large-scale applications [80]. Developing standardized extraction, processing methods, and utilizing GPE as part of a circular economy approach may improve its viability as a fermentation substrate. Another issue is the use of microbial strains adapted to the unique chemical environment of GPE. While conventional fermentation microorganisms, such as Saccharomyces cerevisiae and Lactobacillus spp., can be used, their performance may be hindered by inhibitory compounds or imbalanced nutrient profiles [81]. Recent studies suggest that genetically modified or naturally resilient strains may enhance the efficiency of GPE fermentation [82].

5. Using Non-Conventional Yeasts for Fermented Beverages with Grape Pomace

Exploring non-conventional yeasts as fermentation agents has garnered significant attention recently [83]. These yeasts, which include genera such as Pichia, Hanseniaspora, Torulaspora, Metschnikowia, and Kluyveromyces, offer unique metabolic capabilities that can overcome some of the limitations associated with traditional fermentation using Saccharomyces cerevisiae [84,85]. By leveraging non-conventional yeasts, it is possible to enhance the valorization of grape pomace into diverse and innovative fermented beverages [86]. Non-conventional yeasts often exhibit higher tolerance to phenolic compounds, tannins, and other inhibitory metabolites in this residue. For instance, Metschnikowia pulcherrima has demonstrated resilience in environments rich in polyphenols, which are known to inhibit the growth of traditional yeasts [87]. This resilience allows for more efficient sugar utilization and fermentation performance. Specific non-conventional yeasts can metabolize non-traditional sugars and complex carbohydrates that may remain unfermented by S. cerevisiae. Kluyveromyces marxianus, for example, is capable of fermenting lactose and inulin, which expands the scope of substrates that can be fully utilized in grape pomace-based fermentations [88,89]. Those yeasts also contribute to producing unique aromatic and flavor profiles, which can enhance the sensory complexity of beverages. Hanseniaspora uvarum, for instance, produces high levels of acetate esters, which impart fruity and floral notes [85]. Similarly, Torulaspora delbrueckii is known for its ability to enhance mouthfeel and produce lower levels of ethanol while increasing glycerol content, making it suitable for crafting lower-alcohol beverages with enhanced sensory attributes [90]. Specific non-conventional yeasts can reduce the formation of undesirable by-products, such as acetic acid and sulfur compounds, commonly associated with suboptimal fermentation conditions of grape pomace. Pichia kluyveri, for instance, has shown the potential to minimize volatile acidity while preserving valuable aromatic compounds [91,92].

Furthermore, the co-fermentation of grape must with various fruit juices, such as kiwi, has been investigated to create novel low-alcohol beverages. A particularly promising formulation was derived from a 60:40 mixture of Cabernet Sauvignon must and kiwi juice, fermented with Saccharomyces delbrueckii. Sensory evaluation of this product revealed a favorable fruity aroma and consumer acceptance, with a significant proportion of participants indicating a willingness to purchase the beverage. This co-fermentation approach contributes to the diversification of flavors and the reduction in fruit waste, highlighting its sustainability benefits [93].

Advances in metabolic engineering and bioprocess optimization enable the customization of non-conventional yeasts for fermentation. Genetic modifications can enhance their ability to tolerate specific inhibitors, utilize unconventional sugars, or produce targeted metabolites, such as organic acids, ethanol, or bioactive compounds [94,95]. For example, engineered Yarrowia lipolytica strains have been used to convert lignocellulosic substrates into value-added products, showcasing their potential application [96]. Moreover, using non-conventional yeasts to ferment using grape pomace aligns with sustainability principles and the circular economy. These yeasts can maximize the utilization of this residue’s complex nutrient profile, reducing waste while creating value-added products such as functional beverages, bioethanol, or organic acids [97]. Their ability to ferment at lower temperatures and pH values reduces energy and resource demands, enhancing environmental benefits.

6. Enhancing Grape Pomace Extract (GPE) Nutritional Value Through Fermentation

GPE, a by-product of winemaking, is a rich source of bioactive compounds such as polyphenols, dietary fibers, vitamins, and residual sugars. Despite its nutritional potential, direct utilization is limited due to the low bioavailability of its compounds, the presence of anti-nutritional factors, and variable composition. Fermentation emerges as a promising approach to enhancing the nutritional value of GPE, converting it into functional products with improved health benefits and broader applications [97].

Fermentation processes, particularly those involving lactic acid bacteria (Lactobacillus spp.) and non-conventional yeasts (Kluyveromyces and Torulaspora species), can enhance the bioavailability of bioactive compounds in GPE. Microbial activity breaks down complex polyphenols, such as proanthocyanidins, into simpler phenolic acids, which are more easily absorbed in the gastrointestinal tract [98]. Enhanced bioavailability has been linked to improved antioxidant and anti-inflammatory properties, contributing to GPE’s potential as a functional ingredient [99]. GPE’s microbial fermentation can produce beneficial metabolites such as short-chain fatty acids (SCFAs), exopolysaccharides, and organic acids. Probiotic strains like Lactobacillus plantarum improve the digestibility of GPE and contribute to gut health by promoting the growth of beneficial microbiota [2]. Fermented GPE could thus serve as a prebiotic or functional beverage ingredient with added health benefits. GPE contains certain anti-nutritional compounds, including tannins and phytic acid, which can interfere with nutrient absorption. Fermentation reduces these inhibitory factors, making GPE more suitable for human consumption. For instance, tannase-producing microorganisms like Aspergillus niger can degrade tannins into gallic acid and glucose, enhancing digestibility and bioactivity [100,101]. The fermentation process can be tailored to enrich GPE with essential nutrients such as B-complex vitamins, including folates and riboflavin, produced by specific yeasts and lactic acid bacteria [102]. This fortification transforms GPE from a by-product into a nutritionally valuable ingredient suitable for health-conscious consumers. The fermentation of GPE can enhance its antioxidant properties by increasing the concentration of low-molecular-weight phenolics [103]. Studies have shown that fermenting GPE with Saccharomyces cerevisiae or Lactobacillus strains results in higher levels of phenolic compounds such as gallic acid, caffeic acid, and catechins, which are associated with improved oxidative stress regulation [104]. This antioxidant enhancement makes fermented GPE attractive for functional beverages and nutraceuticals. Fermentation enables the development of novel GPE-based products, such as kombuchas, probiotic beverages, and fermented functional foods. By manipulating fermentation parameters (e.g., pH, temperature, and microbial strain), GPE can be tailored to produce beverages with specific nutritional profiles or bioactivities, expanding its applicability in the food and beverage industry [58].

7. Sustainability and Waste Valorization

Following global environmental concerns, the wine industry needs to address its environmental challenges and focus on solving them. A large quantity of grape pomace is generated during wine production and is usually perceived as a waste. If not appropriately treated, grape pomace can disequilibrate the environment, which goes against what Environmental Management (EM) politics stands for: integrating social and ecological systems [105]. OIV states that by-products should be recycled or reused locally to reduce environmental impact. For this, grape pomace can also be acknowledged as a by-product. It can be used in biotechnological products and applications, such as energy production—through combustion, gasification, and pyrolysis—and fertilizers produced by the anaerobic digestion of grape pomace [7]. GPE also has antimicrobial effects, as well as anticancer effects, alongside antioxidant properties [106]. Therefore, enhancing the nutritional value of GPE through fermentation contributes to a circular economy approach by transforming winemaking waste into high-value products. This approach reduces environmental burdens and generates economic benefits by creating functional food ingredients and nutraceuticals from what would otherwise be discarded [107].

The utilization of grape pomace as itself—not undergoing any kind of treatment or processing—as a substrate in beverages industries does not have any impact with regard to the use of energy or carbon footprint, yet these impacts do happen in the winemaking processes, not necessarily associated with the grape pomace, since most of the case studies link the use of energy to other industrial factors [108,109]. Traditional approaches for managing fruit waste, including grape pomace, are incineration and landfill [110]. These methods are hazardous for the environment, since incineration leaves a carbon footprint [108], and landfill, considering it can inhibit growth or retard germination due to its composition [111], is also harmful to the environment and to biodiversity. Thus, the use of grape pomace as a substrate in beverages industries can help minimize environmental impacts, being a form of waste valorization and waste management, minimizing negative impacts of grape pomace on nature.

8. Conclusions

Despite all the challenges addressed in this review, grape pomace holds promise as a sustainable and bioactive substrate for fermentation, particularly in producing bioethanol, organic acids, and functional beverages. Addressing compositional variability, microbial inhibition, and cost scalability through advanced biotechnological and processing approaches will be key to unlocking its full potential. Fermentation offers an innovative strategy to enhance the nutritional value of grape pomace, improving its potential as a functional food ingredient or beverage base. By improving bioavailability, reducing anti-nutritional factors, and enriching its nutrient profile, fermented grape pomace can meet the growing demand for sustainable and health-promoting products. Continued research into fermentation technologies and microbial interactions will be pivotal in discovering the residue’s full potential in the food and nutraceutical industries.

Non-conventional yeasts offer promising avenues to enhance the fermentation of this type of residue, creating unique and sustainable beverages while addressing the limitations of traditional processes. Through biotechnological advancements and process innovations, these yeasts can play an essential role in valorizing grape pomace extract and expanding the diversity of fermented products. While fermentation shows great promise in enhancing the nutritional value of grape pomace, certain challenges remain. Standardizing fermentation processes to ensure consistent product quality and efficacy is critical. Understanding the interaction between the compounds and microbial metabolism can also help optimize fermentation conditions for specific nutritional outcomes. Advances in microbial biotechnology, including genetically modified strains or microbial consortia, may further enhance the potential of grape pomace as a fermented functional ingredient. Despite their potential, adopting non-conventional yeasts in industrial grape pomace fermentation faces challenges, including limited commercial availability, inconsistent performance under large-scale conditions, and the need for optimized fermentation parameters customized to each yeast species.

Recent advancements in the use of grape pomace for the development of low-alcohol beverages emphasize both the potential health benefits and sensory appeal of these products. By utilizing innovative fermentation techniques and novel ingredient formulations, the beverage industry continues to make strides toward sustainable and functional low-alcohol beverages that meet the demands of modern consumers. The integration of grape pomace into these products not only enhances their bioactive properties but also contributes to waste reduction, aligning with current trends in sustainability and health-conscious consumption.

Additionally, regulatory approval and consumer acceptance of novel fermentation processes and yeasts may pose hurdles [90]. To address these issues, future research should focus on developing robust, industrially viable strains with predictable performance, exploring synergistic fermentations involving S. cerevisiae and non-conventional yeasts to combine their strengths, conducting sensory studies to evaluate consumer preferences for grape pomace-fermented beverages, and optimizing process parameters to scale up fermentation using these novel yeasts. Although the composition variability of GPE may be presented as a challenge, it can also be an opportunity for local beverage industries. The difference in grape varieties cultivated in each region—and consequently the difference in GPE composition—gives them the chance to produce beverages with a unique profile, resulting from using non-conventional yeasts and the local grape by-product as a substrate.