From Olive Oil to Pomace: Sustainable Valorization Pathways Linking Food Processing and Human Health

Abstract

The olive tree (Olea europaea L.) has been cultivated for millennia, with olive oil representing both a cornerstone of the Mediterranean diet and a major agricultural commodity. Its composition, rich in monounsaturated fatty acids, polyphenols, tocopherols and squalene, supports well-documented cardioprotective, antioxidant and anti-inflammatory benefits. Olive oil production generates substantial secondary streams, including pomace, leaves, pits and mill wastewater, which are rich in phenols, triterpenes and fibers. This review consolidates recent advances in their phytochemical characterization, innovative extraction technologies and health-promoting effects, while highlighting the economic and regulatory prospects for industrial adoption. Comparative analysis shows that olive leaves can produce up to 16,674.0–50,594.3 mg/kg total phenolics; oleuropein 4570.0–27,547.7 mg/kg, pomace retains 2.24 g GAE/100 g dried matrix (DM)total phenolics; oil 13.66% DM; protein 6.64% DM, and wastewater contains high concentration of phenolics content of olives. Innovative extraction techniques, such as ultrasound and microwave-assisted methods, allow for a recovery, while reducing solvent use and energy input. The analysis highlights opportunities for integrating these by-products into circular bioeconomy models, supporting the development of functional foods, nutraceutical applications and sustainable waste management. Future research should address techno-economic feasibility, regulatory harmonization and large-scale clinical validation to accelerate market translation.

1. Introduction

The olive tree (Olea europaea L.) is one of the oldest cultivated plants in the world, with evidence of its domestication tracing back more than 6000 years in the Eastern Mediterranean. Beyond its agricultural significance, the olive tree has historically been a cultural and economic symbol in Mediterranean societies, representing prosperity, peace, and wisdom [1]. Today, olive cultivation has expanded far beyond its native range, reaching regions of America, Australia, and parts of Asia, making olive oil one of the most widely traded vegetable oils globally [2,3].

Olive oil, the primary product obtained from the fruit, is highly valued for its unique sensory properties, nutritional quality, and functional compounds. It is particularly rich in monounsaturated fatty acids, mainly oleic acid, and contains a variety of minor bioactive compounds, including phenolic compounds (hydroxytyrosol, tyrosol, oleocanthal, oleuropein), tocopherol, and squalene, which contribute to its well-documented health benefits [4,5]. These properties support the role of olive oil as a central component of the Mediterranean diet, which has been associated with reduced incidence of cardiovascular disease, metabolic syndrome, and neurodegenerative disorders [6].

The growing global demand for olive oil has, however, intensified the generation of processing by-products, the most notable being olive leaves and olive pomace. Olive leaves, obtained during harvest and pruning, are rich in phenolic compounds such as oleuropein, verbascoside, and luteolin derivatives, with recognized antioxidant, anti-inflammatory, antimicrobial, and cardioprotective activities [7,8]. Olive pomace, the solid residue from oil extraction, contains a complex mixture of fruit skin, pulp, water, residual oil, and stone fragments. Although historically considered waste, it has been increasingly studied for its valuable content in fiber-bound polyphenols, residual oils rich in unsaturated fatty acids [9].

Valorizing these by-products aligns with the principles of the circular bioeconomy and sustainable food systems, as it reduces environmental impact, reduces disposal costs, and generates high-value ingredients for the food and cosmetic sectors [10]. Moreover, the recovery of bioactive compounds from olive-derived matrices may present synergistic health benefits when used in combination, potentially amplifying antioxidant and antimicrobial responses beyond what individual components can achieve [11].

Despite these opportunities, several challenges remain before the large-scale integration of olive leaves and pomace into commercial applications can be achieved. These include the variability of phytochemical profiles depending on cultivation method, geographical origin, agricultural practices, and processing technology [12].

The global olive oil industry remains a significant agricultural sector, with production reaching approximately 2.7 million tons in 2022. Historically, production has shown substantial growth; world production tripled over the past 60 years, rising from under 1 million tons in the early 1960s to approximately 3 million tons in recent years [13]. According to the International Olive Council (IOC), global output in the 2022/23 crop year totaled about 2.76 million tons, with a projected 7% decline to 2.56 million tons in 2023/24, followed by a rebound to 3.38 million tons in 2024/25 [14].

Production remains highly concentrated geographically. The European Union continues to be the dominant producer, accounting for around 67% of global olive oil production, supported by over 4 million hectares dedicated to cultivation. Spain emerges as the global leader, contributing approximately 24% of total production in 2022, followed by Italy, Greece, and Turkey [13,15]. Figure 1 and Figure 2 show the world production of olive and olive oil for 2022.

Despite this scale, extraction efficiency remains limited. Only about 15–25% of the olive fruit mass is converted into oil, meaning that a significant 75–85% becomes by-products, including olive leaves, pomace, and mill wastewater [16]. In traditional three-phase systems, producing 1 L of olive oil can generate up to 4–5 kg of pomace plus around 1–1.5 L of olive mill wastewater [17,18]. This generates enormous quantities of residual biomass globally every year, with considerable environmental implications if not managed properly.

However, these residues are increasingly seen as valuable bioresource streams rather than waste. For example, two-phase extraction systems (which produce a water-rich “alperujo”) reduce wastewater but yield moist semi-solid residues that require thoughtful valorization [19,20]. Efficient recovery strategies, such as composting, extraction of bioactives, or development of functional materials and bioenergy by-products, can contribute to resource efficiency, emission reduction, and circular economy objectives [20,21].

This review aims to go beyond previous studies by integrating technological, economic, and regulatory considerations into a single framework. In contrast to previous analyses that have mainly focused on individual by-products or technical aspects, this article highlights the interconnections between olive oil, pomace, leaves, seeds and wastewater, highlighting their collective potential within a circular bioeconomy model. By synthesizing data on bioactive yield, extraction efficiency, and scalability, this paper provides a comparative perspective that can guide both researchers and industry stakeholders in selecting the most promising valorization strategies.

Relevant literature was extracted from PubMed and Web of Science for the period 2008–2025, using keywords such as “olive oil”, “olive pomace”, “olive leaves”, “olive mill wastewater” and “circular bioeconomy”. Research articles and reviews in English that reported data on phytochemical composition, extraction, health effects or valorization strategies were included.

2. Olive Processing, Extraction, and Product Characteristics

2.1. The Olive Processing Chain

Olive production begins with the cultivation of Olea europaea L., one of the oldest domesticated plants in the Mediterranean [22]. Harvesting typically occurs between October and February, depending on the climate and cultivar [23]. Methods range from traditional hand-picking to mechanized shakers, which improve efficiency but may affect fruit integrity. After harvest, olives are rapidly transported to processing facilities to minimize enzymatic and microbial degradation, which can reduce oil yield and bioactive content [24].

Once at the mill, olives undergo crushing and malaxation, breaking the pulp to release oil. Separation follows via mechanical pressing or centrifugation, producing olive oil as the primary product. Simultaneously, by-products are generated [23]:

Olive leaves, collected during pruning and harvest, represent up to 10% of the orchard biomass;

Olive pomace, the solid residue containing skins, pulp, stones, and residual oil;

Olive mill wastewater, rich in water-soluble phenolics.

Proper management of these by-products is essential for sustainability, as they can be further valorized into nutraceuticals, functional ingredients, or biofuels, reducing environmental burden [25].

2.2. Extraction and Processing Technologies

Various techniques are employed to extract oil and recover bioactive compounds from leaves and pomace.

Table 1. Extraction and processing technologies applied to olive oil, leaves, and pomace.

Extraction Method	Application (Oil/Leaves/Pomace)	Principle	Advantages	Limitations	References
Cold pressing	Olive oil	Crushing and pressing without heat	Preserves quality and bioactives	Lower yield	[26]
Two-phase/Three-phase centrifugation	Olive oil & pomace	Decanter separation of oil, water, and solids	High industrial efficiency, scalable	Generates wastewater (3-phase)	[27]
Solvent extraction	Pomace, leaves	Organic solvents dissolve lipids/phenolics	Maximizes recovery	Solvent residues, environmental issues	[28]
Supercritical CO2 extraction	Oil, leaves	CO2 under high pressure/temperature as solvent	Solvent-free, preserves thermolabile compounds	High cost, complex equipment	[29,30]
Ultrasound-assisted extraction (UAE)	Leaves, pomace	Acoustic cavitation enhances the release	Faster, higher yield, energy-efficient	Scale-up challenges	[31,32,33]
Microwave-assisted extraction (MAE)	Leaves, pomace	Microwave energy heats intracellular water	Efficient polyphenol recovery	Risk of thermal degradation	[34,35,36]
Enzyme-assisted extraction (EAE)	Oil, leaves, pomace	Hydrolytic enzymes degrade cell walls	Improves yield and bioactive recovery	Cost, optimization needed	[36,37,38,39]
Aqueous extraction	Leaves	Water-based extraction	Eco-friendly, simple	Less efficient for lipophilic compounds	[40,41]
High-Pressure Processing (HPP)	Olive oil, table olives	Non-thermal high-pressure treatment inactivates microbes/enzymes	Preserves bioactives, enhances safety, extends shelf life	High cost, specialized equipment	[42]
Pulsed Electric Fields (PEFs)	Olive oil extraction, pomace	Short electrical pulses	Improves oil yield & phenolic extraction, energy-efficient	Scale-up challenges, equipment cost	[43]
Ozone treatment	Table olives	Oxidizing gas destroys microbes and pesticides	Effective microbial inactivation	Potential oxidation of sensitive compounds	[44]
Fermentation & Bioprocessing	Table olive	Microbial or enzymatic transformation of by-products	Produces bioactive-rich extracts, sustainable valorization	Requires optimization and safety validation	[45]
Nanotechnology	Olive leaves extracts	Encapsulation in nanocomposite films	Enhances stability & delivery of polyphenols	High cost	[46,47]
Smart Packaging (IoT, sensors, RFID)	Olive oil	Embedded sensors for quality monitoring & traceability	Real-time monitoring, improves consumer trust	High cost, infrastructure required	[48]

summarizes the main methods:

These technologies allow maximization of oil yield, efficient recovery of phenolic compounds, and valorization of by-products, contributing to a circular and sustainable production model.

Traditional methods like cold pressing, centrifugation, or solvent extraction have been used for generations in olive oil production. They are reliable and well-established, but they often come with trade-offs such as lower yields, environmental concerns, or the loss of delicate bioactive compounds. In recent years, modern approaches, like supercritical CO₂, ultrasound and microwave-assisted techniques, enzyme treatments, or even simple water-based extractions, have started to reshape the field. These methods are designed not only to improve efficiency and boost the recovery of valuable phenolics, but also to make the process more sustainable. At the same time, innovative technologies such as high-pressure processing, pulsed electric fields, and ozone treatments are being explored to keep products safe, extend shelf life, and protect their nutritional and sensory qualities. Looking even further, tools like nanotechnology and smart packaging offer exciting possibilities for monitoring, valorization, and traceability across the olive oil chain. In short, while traditional extraction methods remain important, it is the combination with modern innovations that truly points the way toward a more sustainable, efficient, and health-focused future for olive oil, its leaves, and pomace.

In conclusion, supercritical CO₂ is best suited for lipophilic compounds such as squalene and residual oils, while ultrasound- and microwave-assisted extraction ensure efficient recovery of phenolic compounds from leaves and pomace. Enzyme-assisted methods are optimal for the release of bound bioactives but require further cost optimization, while aqueous extractions are preferable for food-grade oleuropein and hydroxytyrosol-rich products. For scale-up, emerging green technologies such as pulsed electric fields and high-pressure processing offer promising options to balance yield, quality and sustainability.

2.3. Origin and Characteristics of Olive Oil, Leaves, and Pomace

2.3.1. Olive Oil

Olive oil is renowned for its high content of monounsaturated fatty acids, especially oleic acid, which typically constitutes 55–83% of its fatty acid profile. This composition contributes significantly to the oil’s oxidative stability and cardiovascular benefits [13,49]. Beyond lipids, olive oil contains a minor yet biologically potent fraction (1–2%) of phenolics (hydroxytyrosol, tyrosol, oleuropein derivatives), tocopherols, phytosterols, and squalene, which impart antioxidant and anti-inflammatory properties [49]. Extra Virgin Olive Oil (EVOO) produced exclusively through mechanical means with acidity ≤ 0.8%, retains the highest level of these compounds [49,50]. A recent estimate indicates that only 15–25% of fruit mass is converted into oil, emphasizing the large volume of by-products generated [13].

2.3.2. Olive Leaves

Olive leaves, which represent roughly 10% of olive tree biomass and are often treated as waste, exhibit exceptionally high concentrations of phytochemicals. Among these, oleuropein is the most abundant secoiridoid (524–21.189 mg/kg dry weight), followed by flavonoids, hydroxytyrosol, and triterpenic acids [51]. Drying method impacts the profile: hot-air drying boosts iridoids like oleuropein, while freeze-drying enhances flavonoid and hydroxytyrosol content along with antioxidant activity [51]. For reference, concentrations of total phenolics in leaves are 16.23 mg/g dry weight [52]. These bioactives lend olive leaves antioxidant, antimicrobial, antihypertensive, and metabolic regulatory benefits, making them promising for nutraceutical and cosmetic applications.

2.3.3. Olive Pomace

Olive pomace is the solid residue after oil extraction, typically accounting for 35–45% of processed fruit weight [53]. It comprises pulp, peels, pits, residual oil, and moisture. Notably, two-phase systems yield high-moisture pomace (≈65–70%), while three-phase systems produce drier pomace (≈45%) [50,53]. Pomace has a high content of organic matter, fats, carbohydrates, and water-soluble phenolic substances. It also contains proteins, although its composition comes from lignocellulosic biomass (30–41.6% lignin, 35.3–49.0% cellulose, pectic polymers, hemicelluloses, oils, and minerals). Pomace is rich in phenolic compounds, including hydroxytyrosol (1.8%), oleuropein, verbascoside, and tyrosol, making it a valuable source of bioactives for food preservation or cosmetic use [50,53]. In one study, olive pomace extracts significantly delayed lipid oxidation [54], reinforcing their utility as clean-label antioxidants. The fiber-rich portion (cellulose, hemicellulose, lignin) further supports circular economy strategies and sustainable utilization.

2.3.4. Global Perspective and Circular Valorization

Annually, millions of tons of olive leaves and pomace are produced globally, constituting a substantial environmental burden due to high organic load and phytotoxicity if improperly disposed of. However, increasing efforts toward valorization are transforming these materials into sources of high-value compounds such as natural antioxidants, dietary fibers, and cosmetic ingredients, aligning with circular bioeconomy goals [55]. Comparative analyses emphasize that olive leaves and pomace often contain higher phenolic concentrations than olive oil itself [52], underscoring their potential for sustainable and economic upcycling.

3. Phytochemical Composition

3.1. Olive Oil

Olive oil is the primary product obtained from the fruit of the olive tree and represents a cornerstone of the Mediterranean diet [56]. It is extracted either by mechanical pressing or centrifugation of the olives, producing different grades such as extra virgin, virgin, and refined oils [57].

The composition of olive oil is influenced by factors such as olive cultivar, geographic origin, harvesting time, and processing methods. Its nutritional and functional properties are largely attributed to its fatty acid composition and minor bioactive compounds, including phenolics, tocopherols, squalene, and phytosterols [56,57]. Understanding the detailed phytochemical profile of olive oil is essential to appreciate its health benefits and potential applications in functional foods and nutraceuticals.

3.1.1. Oleic Acid

Oleic acid is the major monounsaturated fatty acid in olive oil, typically constituting 55–83% of total fatty acids. It contributes to the oil’s oxidative stability and cardiovascular protection by lowering LDL cholesterol and modulating systemic inflammation. Its content is affected by the olive cultivar, fruit ripeness, and geographic origin, with late-harvested olives generally providing higher levels [58,59,60].

3.1.2. Linoleic Acid

Linoleic acid is an essential omega-6 polyunsaturated fatty acid, present in smaller amounts (3–21%). It supports cell membrane integrity and lipid metabolism. Its concentration varies depending on the olive variety and climatic conditions [56].

3.1.3. Hydroxytyrosol

Hydroxytyrosol is a potent antioxidant that protects lipids from oxidation and reduces oxidative stress. Its concentration is highest in extra virgin olive oil and is influenced by processing and storage [7].

3.1.4. Tyrosol

Tyrosol complements hydroxytyrosol antioxidant and anti-inflammatory effects, contributing to cardiovascular protection. Its levels are sensitive to processing methods [7].

3.1.5. Oleuropein Aglycone

Derived from oleuropein, this secoiridoid shares bitterness and contributes neuroprotective, anti-inflammatory, and antioxidant effects. Levels depend on olive maturity and extraction method [7,49,51].

3.1.6. Oleocanthal

Oleocanthal gives extra virgin olive oil its pungent sensation and possesses anti-inflammatory activity comparable to ibuprofen, with cardioprotective and neuroprotective benefits [61].

3.1.7. Lignans (Pinoresinol, Acetoxypinoresinol)

Lignans contribute to lipid metabolism regulation and exhibit additional antioxidant activity, acting synergistically with other phenolic compounds [62].

3.1.8. α-Tocopherol

Vitamin E protects the oil from oxidation, offers stability and antioxidant benefits to the consumer. Its content varies with olive variety, harvest, and processing [63].

3.1.9. Squalene

Squalene is a triterpene that protects against oxidative damage and supports skin health, with potential antitumor and cardioprotective effects [64].

3.2. Olive Leaves

Olive leaves, often considered an agricultural by-product, are increasingly recognized for their rich content of bioactive compounds. They are collected during pruning or harvesting and can be processed to obtain extracts for nutraceutical, cosmetic, and food applications [65].

The phytochemical profile of olive leaves depends on the olive cultivar, age of the leaf, season, and extraction method, making them a versatile source of antioxidants, anti-inflammatory agents, and other functional molecules [66]. Their valorization aligns with sustainable practices, transforming what was once waste into high-value functional ingredients.

3.2.1. Oleuropein

Oleuropein is the most abundant secoiridoid in olive leaves, typically present at concentrations ranging from 30 to 150 mg/g dry weight. It exhibits potent antioxidant, anti-inflammatory, antimicrobial, and cardioprotective effects. Its levels are influenced by leaf age, cultivar, and harvesting season, with younger leaves often containing higher concentrations [67,68].

3.2.2. Verbascoside

Verbascoside, a phenylpropanoid glycoside, contributes additional antioxidant and antimicrobial activity. It is soluble in water and ethanol, and its extraction yield depends on the solvent and method used [69].

3.2.3. Flavonoids (Luteolin, Apigenin, Rutin)

Flavonoids in olive leaves provide anti-inflammatory, antioxidant, and anticancer effects. Luteolin and apigenin protect against oxidative stress and cellular damage, while rutin contributes to vascular health. Concentrations vary depending on cultivar and season [70].

3.2.4. Phenolic Acids (Caffeic, Ferulic, p-Coumaric Acids)

These acids enhance the antioxidant potential of olive leaves and support liver and cardiovascular health. Though present in smaller amounts compared to oleuropein, they act synergistically with other phenolics to enhance bioactivity [71].

3.2.5. Triterpenoids (Oleanolic, Maslinic Acids)

Triterpenoids in olive leaves provide anti-inflammatory, hepatoprotective, and potential antitumor activities. Their levels are influenced by the extraction technique and leaf maturity, with higher concentrations obtained through optimized extraction methods [72].

3.3. Olive Pomace

Olive pomace is the solid residue left after oil extraction, composed of fruit skins, pulp, stone fragments, and residual oil. Historically considered a waste product, pomace is now recognized as a valuable source of bioactive compounds, dietary fiber, and residual lipids. Its composition depends on olive cultivar, fruit ripeness, and extraction method, making it a versatile matrix for nutraceutical, functional food, and cosmetic applications [25,73].

Valorization of olive pomace supports sustainability and circular economy principles by transforming by-products into high-value ingredients.

3.3.1. Residual Lipids (Oleic, Linoleic Acids)

Despite the majority of oil being extracted, pomace retains significant amounts of monounsaturated and polyunsaturated fatty acids. Oleic acid remains the most abundant, contributing to cardiovascular health, while linoleic acid supports cell membrane integrity and lipid metabolism [74]. These residual lipids can be recovered and used in functional food formulations or as nutraceutical ingredients.

3.3.2. Hydroxytyrosol and Tyrosol

Phenolic compounds such as hydroxytyrosol and tyrosol are present in both free and fiber-bound forms. Hydroxytyrosol is a strong antioxidant and antimicrobial agent, protecting lipids and proteins from oxidative damage. Tyrosol complements these effects and contributes to cardiovascular protection [75]. The binding of these phenolics to fibers allows for gradual release during digestion, enhancing their bioavailability.

3.3.3. Triterpenoids and Sterols

Minor triterpenoids such as oleanolic and maslinic acids, as well as sterols, persist in pomace and provide anti-inflammatory, cardioprotective, and cholesterol-lowering effects. Their concentrations vary depending on cultivar and processing conditions [76].

3.4. Comparative Perspective of Olive by-Products

A comparative approach is essential to identify the most effective strategies for valorizing olive secondary streams.

Table 2. Comparative Perspective of Olive By-Products.

By-Product	Main Bioactives (mg GAE/g DW or Equivalent)	Typical Extraction Yield	Economic/Technological Feasibility	References
Olive Leaves	16,674.0–50,594.3 mg/kg total phenolics; oleuropein 4570.0–27,547.7 mg/kg	High (UAE, MAE, SC-CO2)	Readily scalable; commercialized extracts and teas	[77,78]
Olive Pomace	2.24 g GAE/100 g dried matrix (DM) total phenolics; oil 13.66% DM; protein 6.64% DM	Moderate; requires drying/solvent extraction	Viable in biorefineries; drying cost is the main limitation	[9,28]
Olive Stones	Mostly lignocellulose; low phenolics	Low; limited use for bioactive recovery	Better suited for energy, biochar, biocomposites	[79]
Olive Mill Wastewater	High concentration of phenolics	High with membrane filtration/adsorption	Costly handling; strict regulations needed	[80]

summarizes the key differences between olive leaves, pomace, stones and wastewater in terms of bioactive yield, extraction efficiency and economic feasibility. Olive leaves are distinguished by their high oleuropein content and commercial availability, while pomace represents a residue rich in fiber and phenolic compounds, which requires careful handling due to its high moisture content. Olive stones have a lower phenolic yield but offer potential for thermal valorization and biocomposite production, while wastewater from olive mills is exceptionally rich in phenolic compounds but presents handling and regulatory challenges due to its high organic load.

4. Application

4.1. Health/Therapeutic Application

Olive-derived matrices, including olive oil, olive leaves, and olive pomace, have been widely studied for their health-promoting and therapeutic effects. These effects are largely attributed to phenolic compounds, triterpenes, unsaturated fatty acids, and other minor bioactives that modulate oxidative stress, inflammation, immune function, and metabolic pathways [81].

4.1.1. Cardiovascular Protection

Olive oil is strongly associated with cardiovascular benefits [82]. Its monounsaturated fatty acids, particularly oleic acid, improve lipid profiles by lowering LDL cholesterol and increasing HDL cholesterol. Phenolic compounds such as hydroxytyrosol and oleuropein reduce oxidative stress by scavenging reactive oxygen species (ROS) and preventing LDL oxidation, a key step in atherogenesis. Mechanistically, these compounds also enhance endothelial function by increasing nitric oxide bioavailability, promoting vasodilation and reducing blood pressure. Clinical trials have shown that consumption of polyphenol-rich olive oil reduces systemic inflammation and improves arterial elasticity, contributing to cardiovascular disease prevention [83,84,85,86]. Olive leaves complement these effects through their rich content of oleuropein and flavonoids. These compounds modulate lipid metabolism and reduce inflammatory markers such as TNF-α and IL-6. Oleuropein also inhibits platelet aggregation, reducing thrombosis risk. The combined antioxidant and anti-inflammatory activities protect against atherosclerosis and other cardiovascular disorders [71,87]. Olive pomace contains fiber-bound polyphenols and residual oils that support cardiovascular health. The gradual release of polyphenols in the digestive tract provides prolonged antioxidant protection, while pomace fibers contribute to cholesterol regulation and improved lipid metabolism [74].

4.1.2. Anti-Inflammatory Effects

Olive oil phenolics, including oleocanthal, act similarly to nonsteroidal anti-inflammatory drugs (NSAIDs) by inhibiting cyclooxygenase (COX) enzymes, reducing pro-inflammatory mediators such as prostaglandins. These effects have been linked to reduced chronic inflammation, which is implicated in cardiovascular disease, diabetes, and neurodegenerative disorders [88,89]. Olive leaf extracts are rich in oleuropein, verbascoside, and luteolin derivatives, which inhibit NF-κB signaling and suppress pro-inflammatory cytokines. These compounds help modulate immune responses and protect tissues from inflammatory damage, with potential benefits in arthritis, metabolic syndrome, and chronic low-grade inflammation [90,91].

4.1.3. Antioxidant Activity

Olive oil is a potent source of antioxidants. Hydroxytyrosol, tyrosol, and oleuropein neutralize ROS, prevent lipid peroxidation, and protect DNA and proteins from oxidative damage. These antioxidant effects reduce the risk of chronic diseases such as cancer, cardiovascular disorders, and neurodegeneration [92]. Olive leaves provide additional antioxidant support. Polyphenols and flavonoids scavenge free radicals and upregulate endogenous antioxidant enzymes such as superoxide dismutase (SOD) and catalase. These mechanisms protect cells from oxidative stress-induced apoptosis and maintain cellular homeostasis [93]. Olive pomace, due to its residual polyphenols and fibers, delivers sustained antioxidant effects throughout the gastrointestinal tract. The slow release of bound polyphenols during digestion ensures prolonged protection against oxidative stress and supports overall metabolic health [94].

4.1.4. Metabolic and Antidiabetic Effects

Olive leaf extracts are particularly relevant for glucose regulation. Oleuropein inhibits α-glucosidase and α-amylase enzymes, slowing carbohydrate digestion and reducing postprandial blood glucose spikes. Polyphenols also enhance insulin sensitivity and glucose uptake in peripheral tissues, offering therapeutic potential in type 2 diabetes management [95,96]. Olive oil phenolics contribute by reducing oxidative stress and inflammation, which are key contributors to insulin resistance. Regular intake of polyphenol-rich olive oil has been shown to improve fasting glucose levels and HbA1c in clinical studies [97,98]. Olive pomace fibers support glycemic control by modulating nutrient absorption and acting as prebiotics, which enhance gut microbiota composition and improve metabolic homeostasis [99,100].

4.1.5. Neuroprotective Effects

Phenolic compounds in olive oil and olive leaves have demonstrated neuroprotective effects in preclinical and clinical studies. Hydroxytyrosol and oleuropein reduce neuronal oxidative stress, inhibit neuroinflammation, and modulate pathways involved in amyloid beta aggregation, which is implicated in Alzheimer’s disease. These compounds enhance cognitive function and may slow neurodegenerative progression [101,102].

4.1.6. Anticancer Potential

Olive-derived bioactives may exhibit chemopreventive effects. Olive oil phenolics modulate apoptosis, inhibit angiogenesis, and reduce oxidative DNA damage in cancer cells [103,104]. Olive leaf extracts rich in oleuropein and verbascoside demonstrate antiproliferative effects against various cancer cell lines through cell cycle arrest, ROS modulation, and activation of caspase pathways [105]. Olive pomace polyphenols enhance systemic antioxidant defenses and may synergize with other compounds to reduce tumorigenesis in preclinical models [106].

4.2. Food Applications

Olive-derived matrices are widely employed in the food industry for their multifunctional properties, contributing to preservation, nutritional enhancement, and functional product development. The combination of antioxidants, phenolics, fibers, and unsaturated fatty acids allows olive oil, leaves, and pomace to improve food quality, extend shelf life, and provide biofunctional benefits [53].

The integration of olive oil, leaves, and pomace into diverse food systems highlights their multifunctional roles as natural antioxidants, antimicrobials, and sources of dietary fiber. As summarized in

Table 3. Application of olive oil, leaves and pomace in food industry.

Olive-Derived Ingredient	Food Product	Incorporation/Dose	Main Effects	Explanation	References
Olive oil (hydroxytyrosol-enriched)	Functional oils, dressings, mayonnaise, sauces	Enrichment with hydroxytyrosol	↑ Oxidative stability, ↓ peroxide formation, maintained color and flavor	Hydroxytyrosol acts as a powerful antioxidant, inhibiting lipid peroxidation, without altering the sensory properties.	[107,108,109]
Olive oil phenolics (oleocanthal)	Minimally processed foods	Natural presence	Antibacterial activity vs. Listeria monocytogenes, E. coli; ↑ microbial safety	Polyphenols disrupt bacterial membranes, reducing pathogen survival in fresh food.	[110]
Olive leaf powder	Baked goods	Incorporated into doughs with fats	Delays lipid oxidation, extends shelf life	Phenolics eliminate free radicals, slowing rancidity and preserving the quality of the product.	[111,112]
Olive leaf extract (oleuropein-rich)	Functional beverages, teas	Direct addition	↑ Antioxidant capacity, flavor contribution	Oleuropein provides strong radical scavenging activity but also imparts herbal/bitter aromatic notes.	[113,114]
Olive leaf extract (oleuropein)	Minced beef	Incorporated in formulations	↓ Lipid and myoglobin oxidation; 25–65% reduction in TBARS, 43–65% reduction in metmyoglobin	Oleuropein prevents oxidation by scavenging radicals.	[115]
Olive leaf extract	Yogurt	3–5% addition	↑ Total phenolic content (~91 mg GAE/L), ↑ antioxidant capacity (~613 µmol TE/L), good sensory acceptability	The extract increases phenolics and antioxidant levels without exceeding the threshold of bitterness, ensuring consumer acceptance.	[116]
Encapsulated olive leaf bioactives (nanoliposomes)	Yogurt	Entrapment 70–88%	↑ Stability and antioxidant activity, ↓ syneresis, better texture and color retention	Encapsulation protects the phenolics, controls their release and improves the structure of the yogurt.	[117]
Olive pomace fiber	Bakery, cereals, snacks	Incorporated into flour-based products	↑ Water retention, texture, dietary fiber; sustained polyphenol release during digestion	Insoluble fiber increases water retention capacity, while fiber-polyphenol interactions delay release during digestion.	[118,119]
Olive pomace phenolic extract	Active packaging, edible coatings	Films and coatings	Scavenges free radicals, ↓ microbial growth, extends shelf life of meat, cheese, fruits	Gradual release of phenolics into food surface enhances antioxidant	[119]
Olive pomace fiber (polyphenol-rich)	Bread	Substitution with defatted pomace fiber	↑ Prebiotic potential: promotes Bifidobacteriaceae and Lactobacillales; ↓ harmful metabolites in colon model	Fermentable fiber and phenolics modulate the gut microbiota, favoring beneficial strains.	[120]
Olive pomace powder (fermented bread)	Bread	Incorporation into dough	↑ Phenolic content, anti-inflammatory activity (depends on fermentation)	Fermentation increases the bioavailability of phenolics compounds and bioactive peptides, increasing the anti-inflammatory effects.	[121]
Pulp-enriched olive pomace powder (POPP)	Simulated GI digestion model	Retains ≥ 50% phenolics	↑ Bioaccessibility of unsaturated fatty acids; targeted delivery to colon	The fibrous matrix protects the phenolics compounds during digestion, releasing them into the colon, where they exert their bioactivity.	[122]
Olive pomace-enriched biscuits	Biscuits (8-week RCT)	Enrichment with pomace	↑ Phenolic metabolites (DOPAC, homovanillic acid), ↓ oxidized LDL, ↑ beneficial gut microbiota	The phenolics compounds in olive pomace undergo microbial biotransformation, reducing oxidative stress and modulating intestinal flora.	[100]

, olive oil phenolics primarily enhance oxidative stability in lipid-rich matrices, contributing to prolonged shelf life and sensory preservation. Olive leaf extracts, rich in oleuropein and other flavonoids, demonstrate strong antioxidant and antimicrobial effects, particularly effective in dairy and meat products, while also being suitable for functional beverages. Olive pomace, due to its fiber and residual phenolics, has shown promising applications in bakery and cereal products, improving nutritional profiles and exerting prebiotic and anti-inflammatory effects. However, technological challenges such as reduced loaf volume or changes in texture must be considered. Overall, these applications exemplify how olive-derived by-products can simultaneously support sustainable food production and the development of functional, clean-label products.

4.3. Cosmetic Applications

Olive-derived bioactives are also highly valued in cosmetic formulations due to their antioxidant, anti-inflammatory, and skin-protective properties [123].

4.3.1. Olive Oil

Olive oil has long been used in topical applications for its emollient, moisturizing, and protective properties. Its phenolics, tocopherols, and squalene act as antioxidants, protecting skin from oxidative stress induced by UV exposure and pollution.

Mechanistically, hydroxytyrosol and oleuropein neutralize ROS in skin cells, preventing lipid peroxidation in cell membranes and reducing photoaging [124]. Cosmetic applications include creams, serums, lip balms, and sunscreens enriched with phenolic extracts for anti-aging and protective benefits [123].

4.3.2. Olive Leaves

Olive leaf extracts provide potent antioxidant and anti-inflammatory effects in topical formulations. Oleuropein and verbascoside inhibit ROS formation, reduce cytokine-mediated inflammation, and protect against skin damage caused by UV radiation and environmental pollutants [125].

Mechanistically, these compounds upregulate endogenous antioxidant enzymes and inhibit NF-κB signaling in keratinocytes and fibroblasts, reducing inflammatory mediators and promoting skin repair. Olive leaf extracts are incorporated into facial masks, lotions, and serums targeting anti-aging, soothing, and skin barrier support [126].

4.3.3. Olive Pomace

Olive pomace is increasingly used in cosmetic products due to its phenolic content and moisturizing fibers. Polyphenols act as antioxidants, protecting skin cells from oxidative damage, while fibers can enhance texture and hydration in creams and exfoliants [123].

Mechanistically, pomace extracts scavenge free radicals, modulate inflammatory pathways, and improve skin elasticity by promoting collagen synthesis. Applications include anti-aging creams, facial scrubs that leverage the sustained release of bioactive compounds from pomace matrices [127,128].

To provide an integrated overview, Figure 3 summarizes the multifunctional role of olive-derived matrices, correlating their phytochemical richness with both health effects and practical applications. As illustrated, bioactive compounds such as phenols, flavonoids and triterpenoids exert antioxidant, anti-inflammatory, cardioprotective, neuroprotective, antidiabetic, antimicrobial and anticarcinogenic activities, supporting their therapeutic potential. At the same time, these properties allow for widespread applications in the food, cosmetic and packaging sectors, where olive oil, leaves and pomace are increasingly used as natural preservatives, functionality enhancers and agents. This figure highlights the dual importance of olive by-products as health-promoting agents and as valuable raw materials for innovative industrial uses, thus strengthening their contribution to both human well-being and circular bioeconomy strategies.

5. Conclusions

Olive oil, leaves and pomace represent a highly interconnected system within the olive processing chain, providing a broad spectrum of bioactive compounds with significant potential for health, nutrition and technology. Olive oil remains the main product, rich in monounsaturated fatty acids, phenolic compounds, tocopherols and squalene, and serves as the cornerstone of the Mediterranean diet due to its cardioprotective, anti-inflammatory and antioxidant properties. Olive leaves and pomace, historically considered by-products, are increasingly recognized as valuable sources of polyphenols, triterpenes and dietary fiber, supporting applications in functional foods, cosmetics and emerging biofilm-based packaging. Advances in eco-friendly extraction technologies, including supercritical CO₂, ultrasound-assisted and enzyme-assisted methods, allow for the selective recovery of bioactives while reducing environmental impact, and integrated olive biorefineries offer a sustainable framework that aligns with the principles of the circular economy.

Despite these opportunities, several limitations must be acknowledged. Current evidence is largely based on in vitro or animal studies, while large-scale human clinical trials remain limited, making it difficult to fully validate health claims. Furthermore, the phytochemical composition of olive-derived matrices is highly variable, influenced by variety, geographical origin, agricultural practices and processing methods, complicating reproducibility and industrial scalability. Regulatory frameworks also differ substantially across jurisdictions, with inconsistent approaches to safety assessment and approval of functional ingredients, creating barriers to market adoption.

Therefore, future research should address these gaps by conducting life cycle assessments of valorization technologies to quantify environmental and economic impacts, examining regulatory compliance and safety assessments in different jurisdictions, and developing pilot and industrial-scale case studies to compare costs, yields, and sustainability outcomes. Coordinated international efforts to harmonize regulatory standards and validate bioactivity claims through well-designed clinical trials will be essential. By integrating these critical aspects, the valorization of olive oil, leaves, and pomace can progress from experimental studies to large-scale applications, promoting both human health and the goals of a circular bioeconomy. Future research should also explore economic feasibility, regulatory frameworks and comparisons with other agro-industrial by-products to better situate the valorization of olive by-products within the wider circular bioeconomy.