Development of a Process for Polyphenol Extraction and the Production of a Functional Powder for Food Fortification

Abstract

The valorisation of co-products from food supply chains is consistent with the objectives of the national recovery and resilience plan (NRRP), which favours issues relating to the “green revolution and ecological transition”. The nutraceutical characteristics (antimicrobial, antiviral, anti-cancer, etc.) of grape pomace extracts are due to the presence of polyphenols. The objective of the following research was to develop an innovative extraction process in order to produce a special powder with high technological and nutraceutical value (polyphenols). For the experimentation, red grape pomace from Cabernet Sauvignon grapes was used. The first phase of the experimentation allowed the development of the extraction methods; the second involved the use of a pilot system for the extraction, filtration, and distillation phases. The result obtained is a powder with compositional characteristics suitable for the fortification of alcoholic and non-alcoholic food matrices, due to its colouring and antioxidant and nutraceutical properties.

1. Introduction

In nature, the concept of waste does not exist, since everything is continuously transformed and contributes in new ways to the continuation of life cycles; the emulation of this “natural system” is the basis of the green economy [1].

The transition towards a more circular economy is at the centre of the agenda for resource efficiency, established as part of the Europe 2030 strategy [2]. The European Commission has, in fact, presented a package of measures with the aim of helping businesses and consumers make the transition towards a more circular economy where resources are used in a more sustainable way, which is why several projects have been launched in recent years that represent a change of pace in different sectors [3].

In the agri-food sector, reuse, the valorisation of processing waste, and the use of technologies aimed at increasing the life cycle of products are the main ways to achieve the objective of greater eco-sustainability [4,5].

At the national level, on 13 July 2021, Italy’s national recovery and resilience plan (NRRP) was definitively approved by Council Implementing Decision, which implemented the European Commission’s proposal. For mission two of this plan, which concerns issues relating to the “green revolution and ecological transition”, specifically, the “circular economy and sustainable agriculture” and the “development of a sustainable agri-food supply chain”, resources have been allocated to an amount of 57.49 billion euros.

In Italy today, 310,000 farms are producing grapes for wine manufacture [6], equal to 49.6 million hectolitres of wine [7]; the potential quantity of by-products can be estimated at approximately 1 million tonnes of pomace and 2.3 million tonnes of lees; in reality, since 5% of Italian wine comes from wineries that are not required to deliver the pomace to the distillery or to use it alternatively, the real national quantity of pomace and lees available for each harvest year can be estimated at 0.76 million tons of pomace and 0.21 million tons of lees. Therefore, the recovery of the by-products of the vineyard, i.e., pruning residues and cellar residues (i.e., pomace and lees), is of considerable economic importance. Therefore, they should be considered very important resources for the management of the wine production chain [8], rich in antioxidant compounds and useful for increasing nutraceutical values. Some by-products contribute to creating an innovative packaging system with antioxidant and antimicrobial compounds [9,10], as the collected pruning residues can be used for energy purposes in specially designed boilers, while the pomace and lees can be used both as fuels and for the extraction of numerous substances for energy use by transfer to a biogas [11,12,13] or incineration plant [14,15] or for pharmaceutical [16,17,18] or cosmetic use [16,19] or food [20,21], for the extraction of numerous antioxidant substances. Extraction plays an important role in the isolation and purification of many bioactive components from food material. In order to obtain the extract from the food sample, steps like size reduction, extraction, filtration, concentration, and drying should be noted [22]. Various extraction techniques have been analysed to estimate polyphenol recovery from foods, ranging from traditional methods to modern methods. The most extensively used techniques for extraction include Soxhlet extraction, maceration, ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, high-voltage electric discharge, pulse electric field extraction, and enzyme-assisted extraction [23,24]. Apart from these technologies, membrane separation and encapsulation methods have also shown their potential for the better extraction of polyphenols [25].

These recovery activities therefore constitute an important link in the creation of a virtuous system aimed at improving the sustainability of the entire supply chain, enhancing its various components and reducing its impact.

In this study the authors wanted to demonstrate, first with a laboratory-scale experiment and subsequently with a scale-up at a pilot plant, the feasibility of a process for the extraction of polyphenols from the dried and frozen pomace of red grapes and the creation of a special powder to add to compatible foods, to give them added value in terms of nutraceutical properties. To the best of our knowledge, no data are available in the literature regarding this particular type of recovery system.

2. Materials and Methods

2.1. Chemicals

Acetic acid, ethanol, sodium carbonate, ethoxyethane, iso-octane, chlorane 37.0%, sodium hydroxide 0.1 N, sodium thiosulphate 0.01 N, potassium iodide, starch indicator solution 1.0%, ABTS (2,20-azinobis(3-ethylbenzothiazoline-6-sulphonic acid)), 4-(2-Hydroxyethyl)phenol, Trolox (6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), TrisHCl (2-amino-2-(hydroxymethyl)propane-1,3-diol chlorane) and Lithium perchlorate (LiClO₄) were supplied by Sigma Aldrich (Milan, Italy). 3,4,5-trihydroxybenzoic acid was purchased from Carlo Erba (Milan, Italy). 3,3-bis(4-hydroxyphenyl)-2-benzofuran-1(3H)-one 1% and Folin–Ciocalteau reagent were obtained from Titolchimica (Pontecchio Polesine, Italy).

2.2. Pilot Plant (Figure 1)

The production process involved several key unit operations (Figure 1). Firstly, polyphenols were extracted from organic matrices using a hydroalcoholic solution. The solid was then separated via a press, with the hydroalcoholic fraction enriched in polyphenols being recovered. Next, the extract underwent filtration using a basket centrifuge, followed by vacuum batch distillation to remove the ethanol. Finally, drying was achieved using a spray dryer. To execute these operations, the system was provisioned with hot water (ranging from ambient temperature to 90 °C), cold water (ranging from 4 °C to ambient temperature), and compressed air at 8 bar to power diaphragm pumps, the ejector, and instrumentation. Additionally, temperature, pressure, and flow sensors were installed, along with electronic sensors that transmitted signals to the control panel. The control panel housed various functionalities. It included start switches for the reactor stirrer, air heater, and press motor, as well as a regulator for vacuum control within the plant and an acquisition system for the reactor load cells. Moreover, signal acquisition and conversion systems were integrated with probes in the field, connected to a web acquisition system (CWS). This system facilitated the real-time monitoring of key process variables and historical data acquisition. The CWS allowed for system synoptic viewing and the generation of variable graphs. A vacuum regulation system, employing a compressed air ejector, was implemented. Vacuum regulation was managed by a sensor in the control panel and a regulation valve controlling compressed air flow to the ejector, thereby regulating the absolute pressure in the system. The system could transition the entire pilot plant volume from atmospheric pressure to 0.2 bar absolute in roughly 30 min, maintaining this pressure during the extraction and distillation processes.

Figure 1. Pilot plant with extraction reactor (left) and distillation section (right).

Figure 1. Pilot plant with extraction reactor (left) and distillation section (right).

Finally, the plant was equipped with the following tanks:

1 m³ ethanol tank, used for loading ethanol into the reactor via a membrane pump;

1 m³ tank of demineralised water, used to load water into the reactor or reboiler via a membrane pump;

0.2 m³ tank for distillate discharge (equipped with a safety container).

2.3. Extraction Section

The extractor, serving as a reactor with a total volume of 155 L, boasted dimensions of 450 mm in diameter and 800 mm in height. Its features included a heating jacket, adjustable within the temperature range of ambient to 90 °C, a double-turbine mechanical stirrer, and appropriate breakwaters to optimise agitation while preventing vortices. Furthermore, it was equipped with a bottom butterfly valve, a nozzle for loading solids (DN150) with a safety grid, and additional nozzles for liquid feeding and gas venting, alongside load cells for weighing purposes.

Demineralised water and ethanol were loaded into the reactor via dedicated membrane pumps, with weighing facilitated by load cells. The loading of the thawed solid matrix was performed manually through the appropriate feeding nozzle.

The extraction process unfolded through several sequential steps:

Demi water was loaded into the reactor.

The mixer was activated.

Thawed solid matrix was loaded into the reactor.

Ethanol was introduced into the reactor.

Air evacuation via the ejector was executed until a residual pressure of 0.2 bar was attained, followed by heating initiation through opening of the manual adjustment valve.

The operating temperature was maintained until extraction completion.

The boiler was deactivated, and the air heater was engaged to cool the reactor solution.

Unloading of the reactor was performed.

Subsequent to the extraction phase, solid/liquid separation and centrifugation took place. The mixture was gravity-discharged via the manual valve at the bottom of the reactor into the hopper of the separating press, equipped with a motorised screw and a counter-cone to remove coarse solids, squeezing them to recover the majority of the hydroalcoholic solution. The residual solution content within the separated solid fluctuated but typically ranged between 10 and 20% by weight. As the press solely eliminated solids larger than approximately 0.2 mm, a subsequent separation step was mandated for smaller particles, employing a basket centrifuge with a polypropylene sock.

To optimise the centrifugation process, the extract exiting the press was allowed to settle overnight in a closed drum, reducing centrifugation times due to a decreased suspended solid quantity. The procedural steps involved the continuous loading of the centrifuge through a diaphragm pump from the pilot plant, continuous discharge of centrifuged extract into a bucket, removal of the polypropylene sock from the centrifuge, mechanical extraction of the separated solids, and washing the sock with demineralised water.

2.4. Batch Distillation

The extract, once centrifuged, was distilled to recover the ethanol. The distillation was carried out in a twelve-plate column, with a diameter of 150 mm and a height of 2100 mm, equipped with a horizontal cylindrical reboiler with a diameter of 450 mm, a height of 1221 mm, and a volume of 170 mm. The column was equipped with a condenser at the head.

The distillation phase allowed the ethanol to be removed from the extract, recovering it for subsequent extraction tests. The entire process took place under vacuum to be able to operate at lower temperatures and avoid chemical or biochemical oxidative phenomena that could compromise the bioactivity of the extracted compounds.

Furthermore, the removal of ethanol was almost complete, in order to obtain an efficient reuse of the ethanol in subsequent extractions and to eliminate the risks associated with the formation of explosive mixtures in the subsequent drying phase via spray dryer.

The procedure followed during the distillation phase was as follows:

• The centrifuged product was loaded into the reboiler through a membrane pump and two cartridge filters that removed any residual solids;
• The compressed air that fed the ejector opened, after having closed all the valves;
• Via the panel, the pressure setpoint was adjusted, and the authors waited for the pressure to stabilise at the setpoint value;
• The heating of the reboiler started by opening the manual adjustment valve of the flow rate of hot water entering the jacket;
• The reflux valve opened completely;
• Once the reboiler and column head temperatures stabilised, the reflux valve was partially closed, setting the desired reflux flow rate; the progress of the distillation was monitored through the visual levels of the reboiler and the distillate accumulation tank and the temperature values recorded for the reboiler and for the column head;
• The distillation was interrupted as soon as a temperature in the reboiler equal to that of boiling water at the operating pressure was reached, or when all the ethanol present in the solution had been removed. The reflux valve and the hot water valve then closed;
• The air heater turned on and cooling started;
• Once a temperature of 30 °C was reached in the reboiler, the compressed air valve of the ejector was closed, and the vacuum was broken by opening a manual valve on the roof of the reboiler;
• The concentrate was discharged;
• The distillate was discharged and recycled to the extraction phase.

2.5. Drying Techniques

The residue obtained, both on a laboratory and pilot scale, was dried in two different ways: The sample was transferred to a crucible and placed in an oven at 60 °C. After a few days of rest in the stove, the extract was completely dried; it was then scraped with a spatula from the container and reduced to powder.

The sample was appropriately diluted with demineralised water up to a maximum ethanol concentration of 2% by weight, to be sent to the subsequent drying phase via spray dryer.

Various preliminary tests had made it possible to identify the optimal operating conditions for the drying phase with a spray dryer, namely:

Air flow 165 m³/h;

Air inlet temperature 160 °C;

Solution flow rate 0.25 L/h;

Cleaning piston activation time: 30 s.

The cyclone allowed only a part (typically less than 30%) of the solid extract to be recovered; the spray dryer was therefore used for the sole purpose of evaluating the feasibility of the process (

Table 1. Spray dryer parameters (temperature (°C), air (Hz), pump (rpm), piston (Hz).

Trial	T (°C)	Air (Hz)	Pump (rpm)	Piston (Hz)
1	90	25	10	10
2	160	40	18	10
3	200	30	18	10

).

2.6. Raw Material

Grape marc (organic Cabernet Sauvignon cv) was collected at the end of a traditional wine-making process for red wine production by La Cura Company, Massa Marittima (GR). To avoid microbiological spoilage and prevent the oxidative degradation of the phenolic compounds, the grape marc was stored in an inert atmosphere (N₂ 100%) until use at different temperature conditions: 18 °C and −20 °C. In order to define the extraction potential of the matrix to be used, tests were conducted to determine the phenolic compounds in fresh pomace, after having dried or frozen it.

2.7. Chemical Characterisation

All the chemical determinations necessary for the characterisation of the extract (pH, dry residue g/L, total phenols mg/L of A. gallic, no flavonoid phenols mg/L of A. gallic, flavonoids mg/L of A. gallic, anthocyanins mg/L of Malvin, antioxidant activity μmol TEAC/mL, and etanol %V/V) were performed as previously described by Bianchi et al. [26] and Mercanti et al. [27].

2.8. Statistical Analysis

A one-way analysis of variance was performed using CoStat, Version 6.451, CoHort 6.0 Software (Pacific Grove, CA, USA) to assess the presence of significant differences in the compositional parameters among the investigated samples. The means were separated by Tukey’s post hoc test using a p ≤ 0.05. Each analysis was performed in triplicate.

3. Results and Discussion

3.1. Polyphenol Content of the Raw Materials

Looking at

Table 2. Comparison of polyphenol content between dry and frozen matrix.

Sample	gGAE/KgSS
Fresh	45$\pm 2$
Frozen (1a)	44$\pm 3$
Dry (1b)	41$\pm 2$
Frozen (2a)	42$\pm 5$
Dry (2b)	40$\pm 3$

Data are expressed as mean ± standard deviation (n = 3) at p = 0.05.

, the polyphenol content of both the frozen and dry samples is slightly lower compared to the fresh sample. This could imply some degree of degradation or loss of polyphenols during the freezing or drying processes [28]. However, the difference in polyphenol content between fresh and frozen/dry samples is relatively small, suggesting that freezing or drying may still retain a significant portion of the original polyphenol content [29]. Understanding the impact of freezing and drying on polyphenol content is crucial for optimising the processing methods in industries such as food or pharmaceuticals [30]. These findings suggest that freezing could be a viable method for preserving polyphenols in matrices intended for extraction processes.

3.2. Laboratory Tests

In order to evaluate the optimal temperature to use in the pilot phase, we conducted a series of pre-screening tests at 20, 40, 55 and 87 °C (

Table 3. pH, dry residue %, total phenols mg/L of A. gallic, no flavonoid phenols mg/L of A. gallic, flavonoids mg/L of A. gallic, anthocyanins mg/L of Malvin, and antioxidant activity μmol TEAC/mL of extract of the pomace extracts obtained using temperatures of 20, 40, 55, and 87 °C.

Parameters	20 °C	40 °C	55 °C	87 °C
pH	4.00 ± 0.01 a	4.00 ± 0.04 a	4.00 ± 0.01 a	4.00 ± 0.04 a
Dry residue %	1.8 ± 0.1 c	1.7 ± 0.1 c	3.7 ± 0.1 b	9.1 ± 0.1 a
Total phenols (mg/L of A. gallic)	79 ± 2 d	101 ± 4 c	201 ± 1 b	833 ± 15 a
No flavonoid phenols (mg/L of A. gallic)	7.6 ± 0.8 d	17 ± 1.0 c	60 ± 9.0 b	85 ± 1.0 a
Flavonoid phenols (mg/L di A. gallic)	72 ± 1 d	84 ± 3 c	140 ± 8 b	748 ± 14 a
Anthocyanins (mg/L of Malvin)	3.6 ± 0.5 d	7.0 ± 0.1 c	54.0 ± 0.1 b	174 ± 8.0 a
Antioxidant activity (μmol TEAC/mL)	0.23 ± 0.04 d	0.53 ± 0.06 c	1.52 ± 0.05 b	2.11 ± 0.08 a

Data are expressed as mean ± standard deviation (n = 3). The letters (a,b,c,d) indicate significant differences (p < 5%) after the ANOVA analysis of variance.

).

Extraction tests were conducted using a hydroalcoholic mixture (50% V/V).

Operating conditions:

Temperatures: 20, 40, 55, and 87 °C;

Solid/liquid ratio = 1/10;

Extraction time: 3 h;

At the end of the extraction, the extracts were filtered with Whitman and Buchner filters.

From the data obtained in Table 3, we can draw several conclusions:

The pH in the various extractions carried out at the indicated temperatures is approximately 4, a value that does not allow the conservation of the extracts in liquid form, which, having a high water activity, could be altered by the development of unwanted bacteria. Therefore, if one did not want to proceed with the drying process of the extracts (the possible industrial production of extracts in aqueous solution), it would be necessary to use acidifiers such as citric acid (E330) and lactic acid (E270).

At higher temperatures, a higher dry residue is obtained, a higher quantity of phenols (flavonoids and otherwise), and a greater antioxidant activity of the extracts, also given the use of an inert atmosphere (N₂ 100%): in these conditions, the increase in the extraction of the analysed compounds is decidedly greater than any thermal degradation of the same.

Based on the results obtained in the laboratory, we subsequently continued with pilot-scale studies. We conducted three phenolic compound extraction tests, exploiting all the variables developed in the previous phase.

3.3. Pilot Plant Tests

Table 4. Operating conditions relating to temperatures, pressure, and time for the three tests carried out.

Operatives Variables	1	2	3
Temperature	55 °C	78 °C	87 °C
Pressure	0.54 bar	1 bar	1.2 bar
Time of extraction	3 h	3 h	3 h

provides a summary of the operating conditions pertaining to temperature, pressure, and extraction time for the three conducted tests. Regarding the temperature, the experiments were conducted at different temperatures: 55 °C for the first test, 78 °C for the second test, and 87 °C for the third test. The variation in temperature indicates an exploration of different thermal conditions to optimise the extraction process. Typically, higher temperatures can enhance the extraction efficiency by accelerating the dissolution kinetics of polyphenols from organic matrices [31,32]. However, there is a balance to strike, as excessively high temperatures might lead to the degradation of heat-sensitive compounds or alterations in the chemical composition of the extract [33].

The pressure conditions also varied across the tests, with the first test conducted at 0.54 bar, the second at 1 bar, and the third at 1.2 bar. Pressure can influence the solubility of compounds and impact the extraction efficiency. In general, higher pressures may enhance solubility [34], particularly for non-polar solvents, potentially leading to increased extraction yields [35]. However, too high a pressure might introduce operational challenges and increase energy consumption.

All three tests were conducted for a duration of 3 h each. Extraction time is a critical parameter that affects the quantity and quality of the extracted compounds [36]. Longer extraction times may allow for a more thorough extraction of polyphenols from the matrices, but there is a practical limit beyond which any additional extraction time may not significantly improve yields and could instead lead to increased costs and energy consumption.

Looking at the dry residue % (

Table 5. Dry residue %, total phenols (mg/L of A. gallic), and the antioxidant activity (μmol TEAC/mL) for the three tests carried out.

Parameters	1		2		3
	Extract	Concentrated	Extract	Concentrated	Extract	Concentrated
Dry residue %	1.92$\pm \mathbf{0.1}$	1.85$\pm \mathbf{0.1}$	0.89$\pm \mathbf{0.1}$	1.73$\pm \mathbf{0.1}$	2.30$\pm \mathbf{0.1}$	3.20$\pm \mathbf{0.1}$
Total phenols (mg/L of A. gallic)	1167 ± 2	2005 ± 1	2669 ± 2	4061 ± 1	3387 ± 2	5124 ± 1
Antioxidant activity (μmol TEAC/mL)	0.36 ± 0.04	0.43 ± 0.06	0.79 ± 0.03	1.23 ± 0.04	1.20 ± 0.08	1.74 ± 0.04

Data are expressed as mean ± standard deviation (n = 3) at p = 0.05.

), extract 1 and concentrated 1 have relatively lower values compared to extract 2 and concentrated 2, while extract 3 and concentrated 3 show the highest values. This indicates differences in the concentration of solids between the extracts and their concentrated forms.

Regarding total phenols (mg/L of A. gallic) (Table 5), there is a significant increase in total phenols when comparing the extracts to their concentrated forms. Extract 1 has the lowest phenol content, while extract 3 has the highest. The concentration process appears to enhance the total phenolic content in the solutions.

Finally, concerning the antioxidant activity (μmol TEAC/mL) (Table 5), the trend is similar to that of total phenols; in fact, the antioxidant activity increases in the concentrated solutions compared to the extracts. Extract 1 shows the lowest antioxidant activity, while extract 3 has the highest. On the basis of the results obtained, we can state that the concentration process seems to enhance the antioxidant capacity of the solutions.

3.4. Spray Dry Drying Tests

At the end, the extracts were dried using a spray dryer in order to obtain a powder (Figure 2). The variations in spray dryer parameters across the trials indicate an exploration of different conditions to optimise the drying process and obtain the desired powder characteristics. The selection of appropriate parameters involves balancing factors such as temperature, air flow, and feed rate to achieve efficient drying while preserving the quality of the final product. Finally, the powdered matrix was dissolved in water and in a hydroalcoholic solution (50% ETOH V/V) in order to define its miscibility and determine the title in the phenolic compounds.

Comparing the data for water and hydroalcoholic solutions (

Table 6. Total phenols (mg/L of A. gallic) and antioxidant activity (μmol TEAC/mL of extract) of the powder dissolved in water and hydroalcoholic solution (50%).

Parameters	Water	Hydroalcoholic Solution
Total phenols (mg/L of A. gallic)	181$\pm 2$	280$\pm 2$
Antioxidant activity (μmol TEAC/mL of extract)	1$.02\pm 0.07$	1.9$2\pm 0.05$

Data are expressed as mean ± standard deviation (n = 3) at p = 0.05.

): The hydroalcoholic solution has a higher total phenol content (280 mg/L) compared to water (181 mg/L). This suggests that using a hydroalcoholic solution as a solvent contributes to a greater extraction of total phenols compared to using water alone. Regarding the antioxidant activity (μmol TEAC/mL of extract), the hydroalcoholic solution shows a higher antioxidant activity (1.92 μmol TEAC/mL) compared to water (1.02 μmol TEAC/mL).

This indicates that the hydroalcoholic solution extraction method results in a higher antioxidant capacity compared to water.

3.5. Main Implications and Future Perspectives

3.5.1. Main Implications

Enhancing Sustainability in the Agri-Food Sector:

The extraction of bioactive compounds like polyphenols from agricultural waste, such as grape marc, underscores the potential to reduce the environmental impacts associated with waste disposal. By valorising these by-products, the agri-food sector can contribute to a circular economy, where waste is minimised and transformed into valuable products.

Development of Value-Added Products:

This study demonstrates the feasibility of turning grape marc, a by-product, into a source of high-value antioxidants. This could lead to the creation of nutraceuticals, functional foods, or natural food preservatives, opening up new markets and revenue streams for the agri-food industry. This powdered formula rich in polyphenols also offers a promising ingredient for the food and cosmetic industries, where antioxidant properties are highly valued.

Optimised Extraction Methods:

The comparison of different solvents for extracting polyphenols reveals that hydroalcoholic solutions are more effective than water alone in both extracting higher concentrations of phenols and increasing antioxidant activity. This insight is crucial for refining extraction processes and improving the efficiency of bioactive compound recovery, potentially leading to better yields and a more cost-effective operation in commercial settings.

Pilot Plant Insights:

The laboratory-scale experiment, followed by the demonstration at the pilot plant, provides essential data on how large-scale operations can be scaled up. The pilot plant’s operational stages—extraction, separation, and drying—offer valuable information for optimising these processes to maximise polyphenol recovery. Such insights are critical for transitioning from laboratory experiments to industrial applications, making the process more viable and scalable.

3.5.2. Future Perspectives

Further Process Optimisation:

This study points to future opportunities for enhancing the extraction process through the optimisation of variables such as solvent composition, temperature, and time. This could further improve yields, reduce energy consumption, and lower costs, making polyphenol extraction from grape marc more efficient and commercially viable.

Exploration of Other Agricultural By-Products:

While this study focuses on grape marc, similar processes could be applied to other agricultural by-products, such as citrus peels, olive pomace, or apple cores. Expanding the scope of such research could unlock additional sources of bioactive compounds, contributing to a broader range of value-added products.

Technological Advancements:

As technology continues to evolve, more advanced techniques such as supercritical fluid extraction, ultrasound-assisted extraction, or membrane filtration could be integrated into the process to enhance selectivity, reduce solvent use, and improve extraction efficiency.

Integration with Sustainable Supply Chains:

These findings have a strong potential for integration into sustainable supply chains, where bioactive compounds can be recovered from agri-food waste and incorporated into various products in the food, health, and cosmetic industries. This could lead to more sustainable practices in manufacturing and distribution, reducing the environmental footprint of agri-food industries.

Scaling Up to Industrial Levels:

The pilot plant demonstration is an important step, but scaling this technology to an industrial level will require addressing challenges such as the consistency of raw material quality, the standardisation of extraction processes, and optimising the economics of large-scale operations. Success in these areas could pave the way for the widespread adoption of this technology.

Regulatory and Market Considerations:

The development of value-added products like polyphenol-rich powders will also require compliance with food safety regulations and market acceptance. Future work could include studying consumer preferences, conducting safety assessments, and navigating regulatory frameworks to ensure that the products can be safely introduced to the market.

4. Conclusions

Within the agri-food sector, initiatives focused on the reuse and valorisation of processing waste are pivotal for enhancing eco-sustainability. This article delves into the analysis of a laboratory-scale experiment and subsequent demonstration of a pilot plant aimed at extracting polyphenols from grape marc, demonstrating the potential for creating powdered formula rich in antioxidant compounds. The operations of the pilot plant, characterised by extraction, separation, and drying processes, provide valuable insights into the optimal conditions for maximising polyphenol extraction and antioxidant activity. The data suggests that the hydroalcoholic solution is more effective in extracting total phenols and has a higher antioxidant activity compared to water alone. This information could be valuable in selecting an appropriate solvent for extracting bioactive compounds with antioxidant properties. Looking ahead, this study not only underscores the significance of leveraging agricultural by-products to enhance the sustainability of supply chains but also highlights the potential for developing value-added products. As the sector progresses, the future prospects entail further advancements in technology and process optimisation, fostering even greater sustainability and innovation in agri-food practices.