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Polyphenols from Winery by-products: Conventional versus Unconventional Extraction Methodologies

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Rui Dias-Costa, Marta Coelho, Raúl Domínguez-Perles, Irene Gouvinhas and Ana Novo Barros

Submitted: 13 February 2025 Reviewed: 16 May 2025 Published: 18 June 2025

DOI: 10.5772/intechopen.1011060

Exploring Natural Phenolic Compounds - Recent Progress and Practical Applications IntechOpen
Exploring Natural Phenolic Compounds - Recent Progress and Practi... Edited by Irene Gouvinhas

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Exploring Natural Phenolic Compounds - Recent Progress and Practical Applications [Working Title]

Irene Gouvinhas and Ana Novo Barros

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Abstract

A large number of studies have already demonstrated that winery by-products (WBPs) are a valuable source of natural antioxidants, especially due to their phenolic content. These residues can be reused as new ingredients in the food, cosmetic, and pharmaceutical industries. For that reason, a scientific foundation for the comprehension of extraction methods’ efficiency is essential for starting the reuse of these by-products on a large scale. Numerous phenolic compounds extraction techniques under different conditions are currently being investigated. There has been a growing scientific interest in these phytochemicals, driven by the adoption of more eco-friendly extraction techniques that facilitate higher extraction yields. To extract the phenolic compounds present in WBPs, conventional methods as well as nonconventional extraction methods can be employed. The first ones, which have been used for a very long period, include Soxhlet extraction, maceration, reflux extraction, and others. Nonconventional methods, widely recognized as eco-friendly methods, such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), and supercritical extraction (SE), among others, provide higher extraction yields and high-quality extracts. This chapter will explore the extraction methodologies of phenolic compounds from WBPs produced by the wine industry, with a focus on both conventional and unconventional techniques. Additionally, the grape varieties mentioned in this review are suitable for production in Portugal under Designation of Origin (DO) and Geographical Indication (GI) classifications.

Keywords

  • winery by-products
  • phenolic compounds
  • extraction techniques
  • conventional methods
  • unconventional methods

1. Introduction

In the field of wine production, a significant amount of solid organic and inorganic materials is generated, none of which form part of the final wine product. These materials originated as a result of a vitivinicultural process and can be classified into wastes, residues, winery or wine sub-products, and winery or wine by-products [1]. WBPs include a diverse range of materials resulting from wine processing, such as wastewater sludge, grape stems, grape pomace (seeds, skins, and pulps), wine lees, and vine pruning woods [2, 3, 4, 5, 6, 7]. Approximately 30% of the total volume of vinified grapes amounts to WBPs, totaling nearly 20 million tons, with 50% of this amount attributed to the European Union [8]. These by-products can be recycled, reused, or recovered, with a view to a circular economy approach, with an improvement in the economic and environmental sustainability of the wine industry [9].

The extraction of phenolic compounds from plant sources is essential for unlocking their numerous potential benefits, as the quantity and composition of these compounds depend on the extraction methods used. It is necessary to optimize extraction methods by balancing yield, selectivity, and sustainability.

The extraction yield of phenolic compounds can be influenced by various factors, including their chemical structure, the number and position of hydroxyl groups, and molecular size. Additionally, parameters such as temperature, solvent type and composition, contact time, particle size, and interactions with other food ingredients also play a crucial role [10, 11, 12, 13].

Traditionally, extraction methods heavily relied on organic solvents, raising concerns regarding their impact and health risks due to their toxicity and flammability. Furthermore, the necessity of boiling in these methods contributes to the loss of valuable products, such as polyphenols [2, 14, 15]. However, there has been a significant change toward nonconventional extraction techniques, driven by the increasing demand for sustainable and environmentally friendly practices. These innovative approaches aim to minimize solvent usage, energy consumption, and overall environmental footprint. In fact, there has been a growing scientific interest in these compounds, driven by the adoption of more eco-friendly extraction techniques that facilitate higher extraction yields [16]. On the other hand, conventional extraction methods have certain drawbacks that need to be addressed. To overcome these challenges, unconventional extraction methods have been developed to bridge the gaps left by traditional approaches [17].

In this chapter, the WBPs generated by the wine industry will be described, along with the conventional and nonconventional methods used for the extraction of phenolic compounds from these by-products, which originate from grape varieties suitable for production in Portugal under Designation of Origin (DO) and Geographical Indication (GI) classifications [18]. Additionally, our aim is to provide an overview of published research to simplify and optimize phenolic extraction procedures, achieving higher extract yields and purities.

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2. Winery by-products

Winery by-products (WBPs), such as grape stems, pomace, wine lees, and vine pruning wood (Figure 1), are produced by winemaking companies and contain valuable bioactive compounds that are often overlooked yet hold significant potential for applications across various industries [2]. They have been recognized as a natural source of polyphenols, namely hydroxybenzoic acids, hydroxycinnamic acids, stilbenes, flavonols, flavan-3-ols, flavones, flavanones, flavanonols, proanthocyanidins, anthocyanins, among others.

Figure 1.

Illustrative image of winery by-products.

2.1 Grape stems

Grape stems, also known as grape stalks, represent a significant portion of wine by-products, with approximately 30 kg being produced for every 1000 kg of grapes harvested during the destemming phase [19]. To prevent excessive astringency and negative effects on the wine’s organoleptic characteristics, grape stems are typically removed before the vinification stages. This practice, particularly the removal of stems prior to maceration in red winemaking, is commonly associated with improved wine quality [5, 20]. This potential material constitutes approximately 25% of the total by-products generated by the wine industry [6, 20, 21, 22, 23]. Their composition comprise approximately 17–26% lignin, 20–30% cellulose, 3–20% hemicelluloses, and 6–9% ash [21]. This byproduct is commonly used in landfilling, landfarming, or composting [24]. However, it has the potential to be utilized as a source of bioenergy in the form of pellets or through chemical and biological processing, yielding valuable food additives, materials, or chemicals [25].

2.2 Grape pomace

Grape pomace, also referred to as grape marc, is the main solid residue generated by the wine industry, resulting from the pressing of whole grapes during must production. It accounts for approximately 20–25% of the total weight of the original grapes and is primarily composed of seeds, skins, pulp, and residual stems [6, 26, 27]. One ton of this material is constituted by 425 kg of grape skin, 225 kg of grape seeds, 249 kg of grape stems, and other minor constituents [28].

The whole grape pomace is produced during the winemaking process, following fermentation for red grapes and preceding it for white grapes [6, 26]. It includes a diverse array of elements, including structural carbohydrates, lignin, oil, polyphenols, unfermented sugars, pigments, and alcohol [29, 30, 31, 32, 33, 34]. Notably, when considering its nutritional value, polyphenols stand out as the primary constituents of grape pomace [30, 31, 32, 33, 34]. Traditionally, this winery byproduct (WBP) has been harnessed for the production of numerous products such as distillates, fertilizers, and animal feed [6]. Moreover, it can serve as a valuable source of tartaric acid, malic acid, citric acid, ethanol, dietary fiber, grape seed oil, and alcoholic beverages through a concise process of short fermentation and distillation [2, 5].

2.3 Wine lees

In accordance with European Commission (EC) Regulation No. 337/79, wine lees, also referred to as dregs, are defined as “the solid residue that precipitates at the bottom of wine containers following fermentation, during storage, or as a result of authorized treatments.” This definition also encompasses the residual matter obtained after filtration or wine centrifugation processes [35]. Wine lees typically account for 2–6% of the total wine volume [6, 21] and are mainly made up of yeast cells, tartaric acid, inorganic matter, phenolic compounds, and ethanol [6, 36]. It can be categorized into three groups based on the vinification stage: alcoholic fermentation lees, malolactic fermentation lees, and lees that develop during the aging of the wine. Additionally, classification by particle size distinguishes between heavy lees and light lees [6, 37]. Traditional applications for wine lees include incineration, landfill disposal, land-spreading, distillation, tartaric acid production, utilization as coloring agents, and incorporation into nutritional supplements [21].

2.4 Vine pruning woods

The distinction between grapevine shoots, grapevine canes, and vine pruning woods is often unclear, as various authors frequently use different names to refer to the same byproduct. The terms “canes” and “shoots” are often used interchangeably [7]. In the literature, some authors used grapevine shoots [13, 38, 39, 40, 41, 42, 43], others grapevine canes [44, 45, 46, 47, 48], and others vine pruning residue [49, 50]. Through the analysis of the articles and the sampling collection dates, the term remains the same because many samples are collected between November and March, the typical time for pruning operations. Noviello et al. [51] also mentioned that grapevine shoots are alternatively known as grapevine canes.

The agronomic practice of pruning results in the generation of a substantial volume of agricultural waste, primarily consisting of vine pruning wood. The annual estimated production of these WBPs is approximately 1–2 tons per hectare [6]. They are considered some of the most prevalent winery wastes [51]. Recent studies recognize them as a valuable resource rather than mere waste [41]. Their composition includes 34% cellulose, 19% hemicellulose, and 27% lignin [21]. This byproduct has diverse applications, including its use as biofuel, aggregate material, cellulose source, and in the production of activated carbon for wine treatment and pulp and paper manufacturing. Moreover, it serves as an alternative to oak chips as an oenological coadjuvant, enhancing the sensory profile of wines [42, 51]. Additionally, it is utilized in the production of ethanol, lactic acid, methanol, various fuels, biomass, and biosurfactants. It also serves as a substrate in mushroom cultivation and is used for extracting volatile compounds [52, 53].

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3. Extraction methodologies

Phenolic compounds from WBPs can be extracted using different methodologies. This section provides a review of the conventional and nonconventional extraction methods of these phytochemicals applied to these by-products of white and red grape (Vitis vinifera L.) varieties authorized for wine production in Portugal (Figure 2).

Figure 2.

Extraction methodologies of phenolic compounds from WBPs of grape varieties authorized for wine production in Portugal.

3.1 Conventional phenolic compounds extraction methodologies

Conventional solid-liquid extraction (SLE), also known as conventional methods, refers to extraction processes characterized by straightforward maceration in a solvent, either with or without stirring. These processes typically occur at atmospheric pressure and are conducted within a temperature range spanning from room temperature to the boiling point of the solvent under reflux conditions. These methods also encompass Soxhlet extraction, liquid-liquid extraction (LLE), and maceration [17, 48, 54]. Many factors significantly influence the outcomes of conventional extraction methods. These include the selection of extraction solvents, their polarity, the solvent-to-solid ratio, the number and positioning of hydroxyl groups, molecular size, extraction temperature and time, particle size, interactions with other food components, pH, and the influence of light [12, 48].

Phytochemicals are primarily extracted using conventional organic solvents such as methanol, ethyl acetate, and acetone, which exhibit outstanding extraction capabilities. However, their inherent health hazards, environmental impact, and concerns regarding the most suitable solvent pose significant challenges [12, 17, 36]. In contrast, ethanol, water, and their mixtures emerge as optimal extraction solvents due to their eco-friendly nature, allowing for their direct application in the food and pharmaceutical industries. These green solvents offer a safer and more sustainable choice [12, 36]. However, there is no solvent that is generally accepted as the best for extracting polyphenols, according to the literature. However, it is generally accepted that solvents with a greater polarity tend to extract phenolics more effectively due to the high solubility of phenolics in these solvents [17].

Extensive research in the literature focuses on the extraction of phenolic compounds from WBPs. Tables 1 and 2 present studies that have employed conventional extraction methods to extract phenolic compounds from WBPs of white and red grape varieties, respectively, considering solvent ratios, temperatures, extraction times, and other variables.

White grape varietiesWinery byproductsExtraction conditionsReferences
Códega-do-LarinhoGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
ViosinhoGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
SLE with water, ethanol, ethanol:water (50:50, v/v)
Temperature: 45°C
Time: 1 h
[57]
SLE with ethanol:water
Solvent ratio: 1:125 (w/v)
RSM
Times analyzed: 10–30 min
Temperatures analyzed: 25–95°C
Solvents concentration: 5–90%
Solvent used: food-quality ethanol
[58]
SLE with methanol: water[59]
SLE with
methanol:distilled water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[60]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Malvasia-FinaGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[62]
SLE with
methanol:distilled water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[60]
SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Moscatel-Galego-BrancoGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[62]
SLE with methanol:distilled water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[63]
SLE with
methanol:distilled water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[60]
Grape pomace (whole pomace)SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Grape pomace (seeds)SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
SíriaGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Gouveio-RealGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
ArintoGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[55]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Borrado-das-MoscasGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
Vine pruning woodsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
EncruzadoVine pruning woodsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
Fernão-PiresGrape stemsSLE with methanol:water[59]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
SLE with
methanol:distilled water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[60]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
RabigatoGrape stemsSLE with methanol:water[59]
SLE with
methanol:distilled water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[60]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
VerdelhoGrape stemsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
FolgasãoGrape stemsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Grape pomace (whole pomace)SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Esgana-CãoVine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Malvasia-ReiVine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]

Table 1.

Studies performed on the extraction of phenolic compounds from WBPs of white grapes (Vitis vinifera L.) varieties using conventional methodologies.

SLE, Solid-Liquid Extraction; RSM, Response Surface Methodology.

Red grape varietiesWinery byproductsExtraction conditionsReferences
Touriga-NacionalGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[66]
SLE with water, ethanol, ethanol:water (50:50, v/v)
Temperature: 45°C
Time: 1 h
[57]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
SLE with ethanol:water
Solvent ratio: 1:125 (w/v)
RSM
Times analyzed: 10–30 min
Temperatures analyzed: 25–95°C
Solvents concentration: 5–90%
Solvent used: food-quality ethanol
[58]
SLE with methanol:water[59]
SLE with
acetone:ethanol:water (1:1:1, v/v/v)
and with ethanol:water (1:1, v/v)
Extraction procedure repetitions: 2 times
[67]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
Grape pomace (whole pomace)SLE with water
Solvent ratio: 1:10 (w/v)
Temperature: 70°C
[68]
SLE with ethanol:water
(80:20, v/v)
Solvent ratio: 1:5 (w/v)
Extraction temperature: room temperature
Extraction time: 48 hours
[69]
SLE with ethanol with a Soxhlet extractor
Solvent ratio: 1:5 (w/v)
Extraction time: 105 minutes
Extraction temperature: 80°C
[27]
Vine pruning woodsSLE ethanol:water (50:50, v/v)
Solvent ratio: 1:40 (w/v)
Extraction temperature: 55°C
Extraction time: 2 h
[13]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
Touriga- FrancaGrape stemsSLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[66]
SLE with water, ethanol, ethanol:water (50:50, v/v)
Temperature: 45°C
Time: 1 h
[57]
SLE with
acetone:ethanol:water (1:1:1, v/v/v)
and with ethanol:water (1:1, v/v)
[67]
SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Grape pomace (whole pomace)SLE ethanol:water
(80:20, v/v)
Solvent ratio: 1:5 (w/v)
Extraction temperature: room temperature
Extraction time: 48 hours
[69]
Tinta-RorizGrape stemsSLE with water, ethanol, ethanol:water (50:50, v/v)
Temperature: 45°C
Time: 1 h
[57]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
SLE with
acetone:ethanol:water (1:1:1, v/v/v)
and with ethanol:water (1:1, v/v)
Extraction procedure repetitions: 2 times
[67]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
Grape pomace (whole pomace)SLE ethanol:water (80:20, v/v)
Solvent ratio: 1:5 (w/v)
Extraction temperature: room temperature
Extraction time: 48 hours
[69]
SLE with ethanol with a Soxhlet extractor
Solvent ratio: 1:5 (w/v)
Extraction time: 105 minutes
Extraction temperature: 80°C
[27]
Vine pruning woodsSLE ethanol:water (50:50, v/v)
Solvent ratio: 1:40 (w/v)
Extraction temperature: 55°C
Extraction time: 2 h
[13]
SLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
SLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
TempranilloGrape stemsSLE with
ethanol:water (50:50, v/v)
Solvent ratio: 1:25 (w/v)
[70]
SLE with
ethanol:water (50:50, v/v)
Solvent ratio: 1:100 (w/v)
Extraction time: 24 h
Extraction temperature: 40°C
[71]
Grape pomace (whole pomace)SLE with
ethanol:water (50:50, v/v)
acidified to pH 1.0 with H2SO4
Temperature: 60°C
[72]
SLE using
a Soxhlet extractor with
ethanol:water (20:80, v/v),
ethanol:water (40:60, v/v),
ethanol:water (60:40, v/v),
ethanol:water (80:20, v/v)
Temperature: 120°C
SLE with
ethanol:water (40:60, v/v)
Solvent ratio: 1:8 (w/v)
Temperature: 40°C
Time: 72 h
[73]
SLE with ethanol:water (50:50)
Solvent ratio: 1:25 (w/v)
[70]
Grape pomace (seeds)SLE with ethanol:water (50:50)
Solvent ratio: 1:25 (w/v)
[70]
Wine leesSLE with ethanol:water (50:50)
Solvent ratio: 1:25 (w/v)
[70]
SLE with
ethanol:water (50:50, v/v)
acidified to pH 2.5 with HCl
Temperature: 25°C
[72]
SLE with ethanol:water (25:75, v/v), ethanol:water (50:50, v/v), ethanol:water (75:25, v/v)
Solvent ratios: 0.1, 0.05, 0.033
and 0.025 g/mL
Extraction temperatures: 25°C, 35°C, and
45°C
Extraction time: 90 minutes
Extraction conditions: pH adjusted to 2.5 with HCl
[74]
SLE with ethanol:water (50:50, v/v), ethanol:water (75:25, v/v)
Solvent ratio: 1:40 (w/v)
Extraction temperature: room temperature
[75]
Vine pruning woodsSLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 180°C
The extracts underwent a drying process using a rotary evaporator, after which they were subsequently reconstituted in 5 mL of methanol and then added n-hexane to remove nonpolar compounds
[53]
SLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 220°C
[76]
AlfrocheiroGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
Vine pruning woodsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
JaenGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
Vine pruning woodsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[65]
SyrahGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
SLE with
deionized water
Time: 10 min in the ultrasonic bath
[77]
SLE with
methanol:distilled water mixture (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[3]
Grape pomace (whole pomace)SLE with methanol
Solvent ratio: 1:40 (w/v)
pH: 4.0 (addition of HCl)
[78]
SLE with ethanol proportions (Response Surface Methodology)
Solvent ratio: 1:10 (w /v)
[37]
Grape pomace (seeds, skins)SLE with methanol
acidified (0.1% HCL, v/v)
Solvent ratio: 1:15 (w/v)
Temperature: 4°C
Time: 2 h
[79]
Grape pomace (seeds, skins)SLE with ethanol:water (10:90, v/v)
pH: 3.5 (tartaric acid)
[80]
Vine pruning woodsSLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 180°C
The extracts underwent a drying process using a rotary evaporator, after which they were subsequently reconstituted in 5 mL of methanol and then added n-hexane to remove nonpolar compounds
[53]
SLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 220°C
[76]
MerlotGrape stemsSLE with deionized water
Time: 10 min in the ultrasonic bath
[77]
SLE with
methanol:water (80:20, v/v)
Time: 3 h
[81]
Grape pomace (whole pomace)SLE with
methanol acidified with 0.1% HCl
Solvent ratio: 1:50 (w/w)
Extraction condition: powdering in liquid nitrogen
Extraction temperature: - 4°C
Extraction time: 1 hour (4 x 15 min)
[82]
SLE with
methanol:water (80:20, v/v), ethanol:water (80:20, v/v), acetone (100:0, v/v), ethyl acetate (100:0, v/v), methanol:water (50:50, v/v) + acid, methanol:water (80:20, v/v) + acid
Solvent ratio: 1:10 (w/v)
Extraction temperature: room temperature
Extraction condition: removal of nonpolar compounds with petroleum ether
Extraction time: 6 h
[83]
SLE with ethanol:water (70:30, v/v)
Temperature: 30°C
[84]
Wine leesSLE with methanol:water:formic acid (80:18.5:1.5, v/v/v)
Solvent ratio: 1:1 (w/v)
[85]
Vine pruning woodsSLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 220°C
[76]
Tinto-CãoGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[62]
Tinta-BarrocaGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[62]
SLE with methanol:water[59]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
SousãoGrape stemsSLE with methanol:water[59]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
SLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[66]
Tinta-AmarelaGrape stemsSLE with methanol:water[59]
SLE with methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[66]
SLE with
methanol:formic acid:water
(50:2:48, v/v/v)
Solvent ratio: 1:125 (w/v)
[61]
Vine pruning woodsSLE with five different ratios of ethanol:water, namely 0:100, 25:75, 50:50, 75:25, and 100:0 (v/v)
Solvent ratio: 1:125 (w/v)
[56]
CastelãoGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
Cabernet-SauvignonGrape stemsSLE with
deionized water
Time: 10 min in the ultrasonic bath
[77]
SLE with
ethanol:water (50:50, v/v)
Solvent ratio: 1:100 (w/v)
Extraction time: 24 h
Extraction temperature: 40°C
[71]
Grape pomace (whole pomace)SLE with an aqueous
solution of base Na2CO3 2.5% (w/w) and
Na2SO3 2.5% (w/w) based on dry pomace
Temperature: 100°C
Time: 120 min
[33]
SLE with
methanol acidified with 0.1% HCl
Solvent ratio: 1:50 (w/w)
Extraction condition: powdering in liquid nitrogen
Extraction temperature: - 4°C
Extraction time: 1 hour (4 x 15 min)
[82]
SLE with
methanol:water (80:20, v/v), ethanol:water (80:20, v/v), acetone (100:0, v/v), ethyl acetate (100:0, v/v), methanol:water (50:50, v/v) + acid, methanol:water (80:20, v/v) + acid
Solvent ratio: 1:10 (w/v)
Extraction temperature: room temperature
Extraction condition: remotion of nonpolar compounds with petroleum ether
Extraction time: 6 h
[83]
SLE with ethanol in deionized water at 0, 20, 40, 60, 80,
and 100% concentrations (v/v)
Extraction time: 90 minutes
[86]
SLE with
methanol:water:acetic acid (80:20:5, v/v/v)
Solvent ratio: 1:50 (w/v)
[87]
SLE with methanol
acidified (0.1% HCl, v/v)
Solvent ratio: 1:15 (w/v)
Temperature: 4°C
Time: 2 h
[79]
Vine pruning woodsSLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 180°C
The extracts underwent a drying process using a rotary evaporator, after which they were subsequently reconstituted in 5 mL of methanol and then added n-hexane to remove nonpolar compounds
[53]
SLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 220°C
[76]
Sauvignon-BlancGrape stemsSLE with water
Solvent ratio: 1:25 (w/v)
Extraction temperature: 348 Kelvin
(74.85°C)
Extraction time: 1.25 h
[88]
SLE with 75% methanol
Extraction time: 2 h
Extraction condition: addition of 75% sulfur dioxide to prevent oxidation
[89]
Grape pomace (whole pomace)SLE with water
Solvent ratio: 1:25 (w/v)
Extraction temperature: 348 Kelvin
(74.85°C)
Extraction time: 1.25 h
[88]
Vine pruning woodsSLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 180°C
The extracts underwent a drying process using a rotary evaporator, after which they were subsequently reconstituted in 5 mL of methanol and then added n-hexane to remove nonpolar compounds
[53]
SLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 220°C
[76]
ChardonnayGrape stemsSLE with
ethanol:water (50:50, v/v)
Solvent ratio: 1:100 (w/v)
Extraction time: 24 h
Extraction temperature: 40°C
[71]
Grape pomace (whole pomace)SLE with an aqueous
solution of base Na2CO3 2.5% (w/w) and
Na2SO3 2.5% (w/w) based on dry pomace
Temperature: 100°C
Time: 120 min
[33]
Vine pruning woodsSLE with ethanol:water (80:20, v/v) at pH 3
Extraction time: 1 hour
Extraction temperature: 220°C
[76]
Pinot-NoirGrape pomace (whole pomace)SLE with
methanol:water:acetic acid (80:20:5, v/v/v)
Solvent ratio: 1:50 (w/v)
[87]
SLE with an aqueous
solution of base Na2CO3 2.5% (w/w) and
Na2SO3 2.5% (w/w) based on dry pomace
Temperature: 100°C
Time: 120 min
[33]
SLE with ethanol:water:formic acid
(50:48.5:1.5, v/v/v)
Solvent ratio: 1:7.5 (w/v)
[90]
Wine leesSLE with ethanol:water:formic acid (50:48.5:1.5, v/v/v)
Solvent ratio: 1:7.5 (w/v)
[90]
MerlotGrape stemsSLE with
methanol:water (70:30, v/v)
Solvent ratio: 1:125 (w/v)
[64]
Grape pomace (whole pomace)SLE with methanol
acidified (0.1% HCL, v/v)
Solvent ratio: 1:15 (w/v)
Temperature: 4°C
Time: 2 h
[79]

Table 2.

Studies performed on the extraction of phenolic compounds from WBPs of red grapes (Vitis vinifera L.) varieties using conventional methodologies.

SLE, Solid–Liquid Extraction; RSM, Response Surface Methodology.

3.2 Unconventional phenolic compounds extraction methodologies

Nowadays, conventional extraction methods are increasingly being replaced by alternative extraction methods. These alternatives commonly use an energy source to enhance the transfer of phenolic compounds into the solvent, thereby providing numerous advantages over the conventional ones [12]. They are renowned for their efficiency, eco-friendliness, reduction in the amount of sample, and decreased energy and time consumption, in stark contrast to the conventional extraction methods, which typically involve higher solvent volumes, often accompanied by increased toxicity, lower extraction efficiency, and concerns regarding environmental disposal [12, 48, 91]. These innovative technologies harbor significant potential, particularly when extracting high-value compounds from WBPs.

These modern methods that adhere to the principles of green chemistry and ecological practices have gained special attention for improving the extraction of phenolic compounds. According to the literature, these methods are Ultrasound Assisted Extraction (UAE), Microwave Assisted Extraction (MAE), Pressurized Solvent Extraction (PSE), Enzyme Assisted Extraction (EAE), High Hydrostatic Pressure (HHP), High Voltage Electrical Discharges (HVED), Pulsed Electric Fields (PEF), and Surfactant Mediated Extraction (SME).

UAE harnesses the principle of acoustic cavitation. This involves the generation of mechanical energy through cycles of compression and rarefaction, transmitted via ultrasonic waves to generate nanobubbles. As these nanobubbles’ energy surpasses their resistance threshold, they collapse, rupturing plant cell walls and enabling solvent penetration within the cells. Consequently, there is a bigger transfer of bioactive compounds [92]. This extraction method offers numerous advantages, including simplicity of use, efficiency, rapidity, selectivity, energy efficiency, economic benefits, and high extraction efficiency. This extraction method is advantageous for thermolabile compounds, as it does not require high temperatures. However, it may lead to liquid oxidation and the formation of free radicals [12, 92]. While this extraction method has primarily found application in laboratory settings, it has also been increasingly utilized across diverse industrial sectors [93, 94]. In the study of Alexandru et al. [95], they reported that the use of this technique enhanced phenolics recovery and antioxidant capacity compared to maceration in grape pomace and grapevine shoots.

MAE uses microwave energy to disrupt the hydrogen bonds of polar molecules within the extraction system, rapidly rotating them via ion conduction or dipole-dipole rotation. Furthermore, it is highly recommended for extracting short-chain polyphenols like flavonoids and phenolic acids from plant materials [92] and is suitable for thermolabile phenolic compounds [12]. Highlighting its advantages, it offers simplicity, short extraction times, and low consumption of both solvent and energy. On the other hand, it requires careful selection of power to prevent excessive temperatures. Factors such as extraction time, temperature, the irradiation power, and the dielectric constant of the solvent can influence the polyphenol extraction [12, 92]. This environmentally friendly extraction method has also been applied in several industrial sectors [94]. This technique enhanced the recovery of polyphenols from grape pomace, as shown by Álvarez et al. [96], which increased yields by 57% and anthocyanin content by 85%. When compared to conventional maceration, the adoption of this approach improved phenolics recovery and antioxidant capacity, according to Alexandru et al. [95]. Moreira et al. [13] demonstrated in their study with grapevine shoots that this extraction technique led to a higher phenolic content compared to SLE and Sub Critical Water Extraction (SWE).

PSE, also referred to as Pressurized Liquid Extraction (PLE) or Accelerated Solvent Extraction (ASE). If water is employed as the solvent, it is alternatively referred to as Pressurized Hot Water Extraction (PHWE), Sub Critical Water Extraction (SWE), or Superheated Water Extraction (SHWE) [48, 91]. This methodology is based on a pressurized extraction chamber (10–15 MPa), which keeps the solvent in a liquid state at a temperature exceeding its boiling point (up to a maximum of 200°C) and under higher pressures (approximately 1700 psi). Subsequently, the extraction efficiency is boosted through enhanced mass transfer and solubility of compounds within the medium [48]. It offers the advantages of faster extraction compared to conventional techniques and low solvent use. However, it exhibits low selectivity, requires high temperatures, and entails costly equipment. Its primary application is the extraction of phenolic compounds [12]. Luque-Rodríguez et al. [43] employed this methodology to extract phenolics from vine shoots, demonstrating increased yield and reduced extraction time compared to SLE. Moreira et al. [13] also used this technique to compare SLE, MAE, and SWE, concluding that SWE resulted in the highest flavonoid content.

EAE is a sophisticated extraction method leveraging enzymes such as cellulases, hemicelluloses, pectinases, and other enzymes that can be used to catalyze the hydrolysis of the polysaccharides in the cell wall, which is primarily composed of celluloses, hemicelluloses (xyloglucans), pectin, and proteins, thereby enabling better release and extraction of phenolic compounds. These compounds are bound to cell wall polysaccharides through hydrophobic interactions and hydrogen bonds [97].

HHP involves the application of high pressures (namely 100–1000 MPa) to a matrix, transmitted by a liquid within a closed system. In this green extraction, pressure forces air out of plant cell vacuoles, leading to cell membrane damage and improved contact with the extraction solvent. Additionally, it can modify the conformation or denature cell membrane proteins, decreasing their selectivity and thus making phenolic compounds more accessible for extraction. The pressure transmitter fluid is generally water, and the process can be used with or without the utilization of temperature. Nowadays, a large number of studies have focused on innovative applications of HHP, such as the improvement of polyphenols’ extraction [98, 99].

HVED includes electrical breakdown, which is accompanied by various secondary phenomena, such as high-amplitude pressure shock waves, bubble cavitation, liquid turbulence generation, and active species production, leading to particle fragmentation and damage to the cellular structure, thereby facilitating the release of intracellular compounds [100, 101]. This method has shown promising results in laboratory studies [93].

PEF implies placing the sample between two electrodes, varying the pulse amplitude between 100 and 300 V/cm and 20–80 kV/cm, conducted at room temperature or slightly higher. Plant cells are exposed to a certain electric field, and consequently, cell membranes can be damaged, leading to the formation of temporary or permanent pores [54, 98, 101].

SME is a technique for extracting substances from a complex matrix, such as plant materials or soil, employing surfactants. These surfactants are compounds characterized by possessing both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties within their molecular structure and can exist as neutral compounds (non-ionic) or as part of anionic or cationic systems [102]. With this type of extraction, surfactants are used to aid in the solubilization and extraction of target substances from the matrix through the formation of micelles or other complexes, where the hydrophilic portion of the surfactant interacts with water molecules, while the hydrophobic portion interacts with the nonpolar compounds of interest [15, 102, 103]. It offers several advantages, including better efficiency of polyphenol extraction, and is recognized as relatively nontoxic, with desirable stability and compatibility, including those that are poorly soluble in traditional solvents. Additionally, it can be a more environmentally friendly option compared to organic solvent-based extraction methods, as surfactants are often biodegradable and can reduce the need for toxic organic solvents [15, 103].

Tables 3 and 4 show several studies on the extraction of phenolic compounds using nonconventional methodologies using different extraction conditions from WBPs of white and red grape varieties, respectively, considering solvent ratios, temperatures, extraction times, and other variables.

White grape varietiesWinery byproductsExtraction conditionsReferences
Sauvignon-BlancGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
ChardonnayGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
ASE (ASE 350) system equipped with a solvent controller
Extraction solvents:
acetone:water (80:20, v/v),
methanol:water (60:40, v/v)
Static time: 4 min
Pressure: 1500 psi
Temperature: 40°C
Heating period: 5 min
[105]
Grape pomaceMAE
Optimal conditions using RSM:
Extraction solvent:
ethanol:water (48:52, v/v)
Time: 10 min
Solid mass: 1.77 g
[106]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]

Table 3.

Studies performed on the extraction of phenolic compounds from WBPs of white grapes (Vitis vinifera L.) varieties using unconventional methodologies.

ASE, Accelerated Solvent Extraction; MAE, Microwave Assisted Extraction; SHLE, Superheated Liquid Extraction; UAE, Ultrasound Assisted Extraction; RSM, Response Surface Methodology.

Red grape varietiesWinery byproductsExtraction conditionsReferences
TempranilloGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
ASE (ASE 350) system equipped with a solvent controller
Extraction solvents:
acetone:water (80:20, v/v),
methanol:water (60:40, v/v)
Static time: 4 min
Pressure: 1500 psi
Temperature: 40°C
Heating period: 5 min
[105]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
Grape pomaceUAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
MAE
(Used as a pretreatment)
Extraction solvent: ethanol:water (50:50, v/v)
Time of irradiation: 60 s
Temperature: 80°C
Power: 300 W
[72]
Wine leesUAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
MAE
(Used as a pretreatment)
Extraction solvent: ethanol:water (60:40, v/v)
Time of irradiation: 90 s
Temperature: 115°C
Power: 300 W
[72]
MAE
Extraction solvent: ethanol:water (60:40, v/v) adjusted to pH 4 with formic acid
Irradiation power: 140 W for 10 minutes
Solvent ratio: 1:8.3
[107]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
SyrahGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
ASE (ASE 350) system equipped with a solvent controller
Extraction solvents:
acetone:water (80:20, v/v),
methanol:water (60:40, v/v)
Static time: 4 min
Pressure: 1500 psi
Temperature: 40°C
Heating period: 5 min
[105]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
UAE
Extraction solvent: ethanol:water (80:20, v/v)
Solvent ratio: 1:30
Temperature: 75°C
Time: 15 min
Amplitude: 70%
Cycle: 0.7 s
[108]
Grape pomaceUAE
Extraction solvent: water
Solvent ratio: 1:20 (w/v)
Temperatures: 20, 35, 50°C
[109]
UAE
Extraction solvent: water
Solvent ratio: 1:5 (w/v)
Acoustic frequency: 40, 80, 120 kHz
Ultrasonic power density: 50, 100, 150 W/L
Times: 5, 15, 25 min
[110]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
Wine leesMAE
Extraction solvent: ethanol 75% (hydrochloric acid 1% in water)
Irradiation power: 200 W for 17 min
Solvent ratio: 1:10 (w/v)
[111]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25(w/v)
Time: 15 min
[32]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
MerlotGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
ASE (ASE 350) system equipped with a solvent controller
Extraction solvents:
acetone:water (80:20, v/v),
methanol:water (60:40, v/v)
Static time: 4 min
Pressure: 1500 psi
Temperature: 40°C
Heating period: 5 min
[105]
PLE
Extraction solvent:
ethanol:water mixtures (0–100%)
Pressure: 1500 psi
Temperatures tested: 40–120°C
Times tested: 1–11 min
Optimal conditions using RSM: 30% ethanol: water, 120°C, 10 min
[22]
Grape pomaceUAE
Extraction solvent: methanol acidified with 2% formic acid
Solvent ratio: 1/100 (w/v)
Ultrasonication: 59 kHz
Time: 10 min
Temperature: 25–35°C
[112]
Wine leesUAE
Extraction solvent: aqueous ethanol solution
Frequency: 40 kHz
Acoustic energy density: 48 W/L
[113]
UAE
Extraction solvent: ethanol:water:formic acid (50:48.5:1.5, v/v/v) at pH 2.7
Different times and ultrasonic powers were tested depending on the experimental design
[114]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
Cabernet-SauvignonGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
ASE (ASE 350) system equipped with a solvent controller
Extraction solvents:
acetone:water (80:20, v/v),
methanol:water (60:40, v/v)
Static time: 4 min
Pressure: 1500 psi
Temperature: 40°C
Heating period: 5 min
[105]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
Grape pomaceASE
Extraction solvent: ethanol:water (70:30, v/v)
Optimal conditions using RSM:
140°C
[115]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
Wine leesUAE
Extraction solvent: aqueous ethanol solution
Frequency: 40 kHz
Acoustic energy density: 48 W/L
[113]
UAE
Extraction solvent: methanol
Solvent ratio: 1:0.25 (w/v)
Time: 15 min
[32]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
Cabernet-FrancGrape pomaceSME
Solvent/liquid ratios: 1:10, 1:20, 1:100 (w/v)
pH: 4.0
Time: 45 min
[15]
Wine leesUAE
Extraction solvent: aqueous ethanol solution
Frequency: 40 kHz
Acoustic energy density: 48 W/L
[113]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
LembergerGrape pomaceEAE
Extraction solvent: water
Solvent ratio: 1:3 (w/w)
Enzymes: Novoferm 106,
Cellubrix L
Temperature: 50°C
Time: 2 h
pH: 4.0
[116]
EAE
Extraction solvent: water
Solvent ratio: 1:3 (w/v)
Temperature: 80°C
Enzymes: pectinolytic and cellulolytic enzymes
[30]
ChambourcinGrape pomacePLE
Extraction solvent: ethanol:water (40:60, v/v)
Tested conditions using RSM:
Temperatures: 70, 100, 130°C
Extraction times: 1, 5, 9 min
Ethanol concentrations: 20, 50, 80%
Optimal conditions:
Time: 9 min
Temperature: 130°C
Extraction procedure repetitions: 5 times
[29]
Petit-VerdotGrape stemsUAE
Extraction solvent:
ethanol:water (50:50, v/v)
Extraction temperatures: 5–65°C
Ultrasound amplitude: 30–70%
Ultrasonic cycle duration: 0.2–0.7 s
Ultrasonic probe tip: 2–7 mm
Extraction time: 5–15 min
Solvent ratios: 1:25, 1:50
Intensity: 200 W and 24 kHz
[104]
Vine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
Cabernet-MitosGrape pomaceEAE
Extraction solvent: water
Solvent ratio: 1:3 (w/v)
Temperature: 80°C
Enzymes: pectinolytic and cellulolytic enzymes
[30]
Alicante BouschetGrape pomaceHHP
Extraction solvent: sodium acetate buffer (pH 5)
Solvent ratio: 1:8 (w/v)
Times: 0, 5, 10, 15, 30 min, and 2 h
[99]
MalbecVine pruning woodsSHLE
Solvent extraction: ethanol:water 80:20 (v/v) at pH 3.60
Extraction temperature: 180°C
Extraction time: 60 min
MAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Solvent ratio: 1:20 (w/v)
Extraction time: 5 min
Irradiation power: 140 W
UAE
Extraction solvent: ethanol:water 80:20 (v/v) at pH 3
Irradiation power: 280 W
[53]
NebbioloVine pruning woodsUAE
Extraction solvent: ethanol with
1.5% β-cyclodextrin solution for
5 min at 100 W and 30 min at 80 W
Solvent ratio: 1:10 (w/v)
MAE
Extraction solvents: ethanol, ethanol:water (50:50, v/v), acetone, butanone
Temperature: 60°C
Time: 30 min
Power: 1.5 kW under
nitrogen pressure (5 bar)
[95]
GrenacheVine pruning woodsPEF, HVED, and UAE
(Used as a pretreatment)
Extraction solvent: basified water
(0.1 M of NAOH)
Temperature: 50°C
[100]
Tinta-RorizVine pruning woodsMAE
Extraction solvent: ethanol:water (60:40, v/v)
Solvent ratio: 1:200 (w/v)
Extraction temperature: 100°C
Extraction time: 20 min
SWE
Solvent ratio: 1:40 (w/v)
Extraction temperature: 150°C
Extraction time: 40 min
Pressure: 40 bars
Frequency: 3 Hz
[13]
Touriga-NacionalVine pruning woodsMAE
Extraction solvent: ethanol:water (60:40, v/v)
Solvent ratio: 1:200 (w/v)
Extraction temperature: 100°C
Extraction time: 20 min
SWE
Solvent ratio: 1:40 (w/v)
Extraction temperature: 150°C
Extraction time: 40 min
Pressure: 40 bars
Frequency: 3 Hz
[13]

Table 4.

Studies performed on the extraction of phenolic compounds from WBPs of red grapes (Vitis vinifera L.) varieties using unconventional methodologies.

EAE, Enzyme Assisted Extraction; HHP, High Hydrostatic Pressure; HVED, High Voltage Electrical Discharges; MAE, Microwave Assisted Extraction; PEF, Pulsed Electric Fields; PLE, Pressurized Liquid Extraction; RSM, Response Surface Methodology; SWE, Subcritical Water Extraction; UAE, Ultrasound Assisted Extraction.

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4. Challenges, limitations, and future directions

This review evidenced that grape pomace is the WBP with the highest number of studies comparing the different extraction methods. In contrast, grape stems remain the least explored, particularly when it comes to unconventional extraction methodologies. In this regard, further research is necessary on the extraction of these phytochemicals present in grape stems using nonconventional methods.

WBPs hold significant potential for use in several added-value products due to their content of bioactive compounds, namely phenolic compounds. However, the choice of extraction method directly influences the recovery of these valuable compounds present in WBPs.

Furthermore, the extracted phenolic compounds face challenges related to low bioavailability, chemical instability, low solubility, occasional low extraction yields, low stability, and sensitivity to environmental factors such as light and heat, resulting in loss of their bioactivity [27, 117, 118]. For these reasons, more research is needed to increase the extraction yields while reducing the processing time of these valuable compounds [119]. The adoption of green technologies, replacing toxic solvents with more sustainable alternatives, is essential to optimizing processing [119].

The study by Liu et al. [120] demonstrated that UAE and SLE extracted a similar number of phenolic acids, though with different compositions. However, the UAE allows the identification of a higher number of flavonoids compared to the conventional method, suggesting that this nonconventional approach efficiently extracts flavonoids in a shorter time while maintaining a similar chemical composition to SLE [120]. The same authors also concluded that the UAE holds significant potential for green, large-scale industrial production, helping to reduce both economic and environmental impacts. In this sense, combining UAE with SLE or other techniques [121] could be a promising strategy to enhance extraction yields and improve the recovery of phenolic compounds. For example, in the study conducted by Matos et al. [122], which focused on extracting phenolics from wine lees, the microwave pretreatment prior to conventional SLE led to increased total phenolic content, total anthocyanin content, and enhanced antioxidant activity. A similar outcome was observed in the study by Rajha et al. [100], where HVED, PEF, and UAE pretreatment increased the extraction efficiency of total polyphenols, kaempferol, epicatechin, and resveratrol compared to untreated grapevine shoot samples. Romero et al. [121] also utilized microwave pretreatment and enhanced anthocyanin extraction yield, reducing processing time in wine lees samples. For easy scale-up and cost-effective production, simple and effective extraction and purification procedures should be chosen in order to enhance the recovery of bioactive compounds, maintain their integrity, and maximize their potential for commercialization [93].

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Acknowledgments

Rui Dias-Costa acknowledges the financial support provided by National Funds by FCT Ph.D. grant: 2021.07571.BD, https://doi.org/10.54499/2021.07571.BD (accessed on 4 June 2025). Irene Gouvinhas is funded by FCT under the Scientific Employment Stimulus—Individual Call (2022.00498.CEECIND), https://doi.org/10.54499/2022.00498.CEECIND/CP1749/CT0001 (accessed on 20 January 2025).

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Conflict of interest

The authors declare no conflict of interest.

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Funding

This work was supported by National Funds by FCT – Portuguese Foundation for Science and Technology, under the projects UID/04033/2023: Centre for the Research and Technology of Agro-Environmental and Biological Sciences, LA/P/0126/2020 (https://doi.org/10.54499/LA/P/0126/2020), and the scientific collaboration under the FCT project UIDB/50016/2020.

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Written By

Rui Dias-Costa, Marta Coelho, Raúl Domínguez-Perles, Irene Gouvinhas and Ana Novo Barros

Submitted: 13 February 2025 Reviewed: 16 May 2025 Published: 18 June 2025