Olive Fruit and Olive Oil

C H A P T E R

8 Olive Fruit and Olive Oil ¨ zge Sec¸meler1 and Charis M. Galanakis2,3 O ˙ Gastronomy Department, Altınba¸s University, Istanbul, Turkey 2Research & Innovation Department, Galanakis Laboratories, Chania, Greece 3Food Waste Recovery Group, ISEKI Food Association, Vienna, Austria

1

8.1 INTRODUCTION Olive oil is one of the most reputative traditional foods in the world. Indeed, the cultivation of olives to produce olive oil has deep roots in the history of the Mediterranean region. Worldwide olive oil production was about 2.5 million tons in 2017, the majority of them (87% in 2017) in Mediterranean countries (IOC Production data, year 2016/2017). Spain, Italy, Greece, and Turkey (followed by Tunisia, Portugal, Morocco, and Algeria) are the biggest olive oil-producing countries, generating B1.3 and B0.2 million tons in 2017, respectively. Outside the Mediterranean basin, olives are cultivated in the Middle East, the United States, Argentina, and Australia (Paraskeva and Diamadopoulos, 2006). The tradition of olive oil production represents a very important asset for many countries, not only in terms of culture and health, but also in spite of wealth. Therefore, olive oil production increased over the last few decades as a valuable source of antioxidants and essential fatty acids in the human diet and constitutes one of the most important dietary trends worldwide (Souilem et al., 2017). Olive oil constitutes the basis of the famous Mediterranean diet, whereas its health benefits such as anticancer, anticholesterol, and antioxidant activities are well-known. These benefits partially depend on the presence of functional bioactive compounds (Newmark, 2006; Juan et al., 2006; Garcı´a-Villalba et al., 2012; Cicerale et al., 2012; Watson and Preedy, 2011). Olive oil production is accompanied with the generation of huge amounts of waste that are disposed in the environment, leaving a congested footprint on land and water. This footprint is caused by the high phytotoxicity of polyphenols induced by their high

Innovations in Traditional Foods DOI: https://doi.org/10.1016/B978-0-12-814887-7.00008-3

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concentration in waste. Besides, during olive oil production, almost all the phenolic content of the olive fruit (B98%) remains in the olive mill processing by-products (Klen and ¨ stu¨ndag, ˘ 2013; Sec¸meler, 2017; Vodopivec, 2012; Rodis et al., 2002; Sec¸meler and Gu¨c¸lu¨ U Souilem et al., 2017). These materials are undesirable for the olive oil industry in spite of environmental impact and high disposal costs. To this line, they have been considered as a matter of prevention and minimization for as many years as industrial olive oil production exists. Loss of polyphenols and valorization of these undesirable substances have been studied for many years, whereas the proposed treatments and corresponding references are endless. However, the proposed techniques need to be feasible for the industry. This fact explains why the olive oil industry still remains unsustainable, with a few opposite examples that confirm this rule of thumb (Galanakis, 2017). Olive oil is a sector challenged by many directions: cultivation, production, environmental footprint, and market needs. The latest reflects consumers demand for extravirgin olive oils (EVOOs) of the highest quality. Cultivation and production line dominates the quality of the product, however its price at the end of the day is affected by market rules. This fact results in price variations from time to time that pressure the small traditional producers. On the other hand, local authorities pressure olive oil industries to reduce their environmental impact. Under these conditions, even cheap solutions that promise the total treatment of olive mill processing by-products may collapse financially small olive oil units. As a result, most treatment technologies have been rejected in practice due to industries in denial that claim to close down production, and society’s tolerance that delays the enforcement of environmental legislations implementation (Galanakis, 2017). The urgent need for sustainability within the olive oil industry has turned the interest of producers to consider olive mill processing by-products management with another perspective. These substrates contain ingredients like water, organic compounds and nutrients, which could be recovered or recycled in the food chain and environment. Therefore, olive mill processing by-products (e.g., olive leaf, pomace, deodorization distillate) have been valorized in many applications like alternative energy production (biodiesel, biogas, bioethanol, biohydrogen, biofuel), animal husbandry (feed), agricultural applications (soil regulator), food (gelling agents, functional foods, preservatives), drugs, nutraceuticals, cosmetics (natural moisturizers, sunscreen agents), and biotechnological applications (bioplastic/biopolymer, biosurfactant, and lipase production) (Ferna´ndez-Bolan˜os et al., 2006; Tornberg and Galanakis, 2010; De Magalha˜es et al., 2011; Pizzichini and Russo, 2005; Villanova et al., 2009; Life07 Env/It/421, Re-Waste). Following these trends, the current chapter discusses innovations in the field of olive oil sector, highlighting the prospects of utilizing bioactive compounds of olive fruit in nutrition, human health, and wellness. The composition of olive fruit and its bioactives are discussed in relation to olive oil production. Loss of antioxidants and volatile compounds during production are summarized, whereas trends for the recovery of polyphenols from olive related derivatives are denoted in the prospect of utilizing them in conjugation with olive oil as “superfoods” of the human diet. Ultimately, recommendations based on the current situation are provided, using sector’s competitive advantages and keeping in mind not to lose its traditional nature.

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8.2 COMPOSITION OF THE OLIVE FRUIT

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8.2 COMPOSITION OF THE OLIVE FRUIT There are hundreds of olive cultivars having different shapes, sizes, and composition. The average composition of an olive fruit (Olea europaea L.) used for oil extraction is 22% oil, 50% water, and remaining 19% carbohydrates (pectin, cellulose (6%), and hemicelluloses), proteins (1.6%), minerals (1.5%), volatile compounds (aldehydes, alcohols, esters, hydrocarbons, ketones, furans), and lignin (Conde et al., 2008; Connor and Fereres, 2010; Niaounakis and Halvadakis, 2006; Vierhuis et al., 2001; Boskou et al., 2006). Additionally, olive fruit contains hydrophilic bioactive compounds like phenols (1% 2 3%), lipophilic bioactive compounds (,1%) including squalene (0.48% oil), β-sitosterol (0.27% oil), α-tocopherol (0.028% oil), and pigments (chlorophyll and carotenoids) (Guillaume et al., 2011; Bianchi and Vlahov, 1994; Manzi et al., 1998; Cortesi et al., 1999; Boskou et al., 2006; Niaounakis and Halvadakis, 2006; Jemai et al., 2009) (Fig. 8.1). The oil is concentrated mainly in the pulp (95%) of the olive fruit (Sec¸meler and Gu¨c¸lu¨ ¨ stu¨ndag, ˘ 2017). Oil and water, the two main phases, are distributed through anatomic U parts of olive fruit (skin, pulp, stone, seed) and olive bioactives are distributed between oil and water phases during processing according to their solubility and mass transfer behavior. Total sterol and tocopherol concentrations are 2 2 4 fold higher in the seed than in the pulp (Bornaz et al., 2012; Cortesi et al., 1999). On the other hand, squalene has only been detected in pulp oil (Bianchi and Vlahov, 1994). Phenolic compounds are hydrophilic dispersed in water phase as free form or present as bound form through the lignin. The distribution of oil, bioactives, and volatile compounds into the olive cell and their interactions with other cellular components are crucial for their extraction behavior. Approximately 76% of the free oil is located in the vacuole of the cell where the other 24% of the dispersed oil in cytoplasm is bound oil interacting with a lipoprotein membrane (Petrakis, 2006; Ranalli et al., 1998). Plant cell membranes consist of phospholipid bilayers: FIGURE 8.1 Composition of whole olive fruit (%, w/w). Source: Data taken from Boskou, D., Blekas, G., Tsimidou, M., Other compounds, 2 2006. In: Boskou, D. (Ed.), Olive Oil Chemistry, Properties, Health Effects, AOCS Press, Thessaloniki, pp. 41 72; Oil, 22 Niaounakis, D.M., Halvadakis, C.P., 2006. Waste Management Series 5: Olive Processing Waste Management, second ed., Elsevier Ltd., Italy; Jemai, H., Bouaziz, M., Sayadi, S., 2009. Phenolic composition, sugar contents and antioxidant activity of Tunisian sweet olive cultivar with regard to fruit ripening. J. Agric. Food Chem. 57, 2961 2968.

Whole olive fruit Minerals/ash, 2 Protein, 2 Cellulose, 6

Sugar, 13

Water, 50

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squalene, in free form, inside the midplane of the phospholipid bilayer (Haub et al., 2002), however β-sitosterol (Read and Bacic, 2002; Peng et al., 2002), and α-tocopherol (Lopez ¨ stu¨ndag˘ (2017) suggested that et al., 2014) are bound to the bilayer. Sec¸meler and Gu¨c¸lu¨ U β-sitosterol might have further interaction with cellulose in the cell wall structure.

8.3 OLIVE OIL BIOACTIVES Bioactive components are essential (vitamins) or nonessential (polyphenols) substances, which are exist especially in plants and affect human health (antioxidants, antimicrobials, anticancer, antiinflammatory, anticholesterol) (Biesalski et al., 2009; Kris-Etherton et al., 2002). Phenolic compounds are the primary bioactive compounds (1% 2 3%, w/w) in olive fruit (Niaounakis and Halvadakis, 2006).

8.3.1 Phenolic Compounds The plant phenols are secondary metabolites possessing at least one aromatic ring bearing one or more hydroxy substituents (Ryan and Robards, 1998). More than 36 phenolic compounds have been identified in olive oil that are hydrophilic (phenolic acids, phenolic alcohols, flavonoids, and secoiridoids) and lipophilic (cresols). Their antimicrobial, antioxidant, and antiinflammatory effects have been shown in many studies (Cicerale et al., 2009, 2012). Some nonvolatile phenolic compounds stimulate the tasting receptors such as bitterness perception, pungency, astringency, and metallic attributes (Boskou, 2012). Phenols can be grouped according to their chemical structure as phenolic acids (benzoic acid derivatives, cinnamic acid derivatives, and other phenolic acids and derivatives), phenolic alcohols (i.e., tyrosol and hydroxytyrosol), secoiridoids (oleuropein and ligstroside), hydroxy-isocromans (3,4-dihydro-1H-benzo[c]pyran derivatives), flavonoids (flavones and flavanols), and lignans (1-acetoxypinoresinol and pinoresinol) (Cicerale et al., 2009). Their decreasing polarity pattern is hydroxytyrosol , tyrosol , vanillic acid, caffeic acid , p-coumaric acid , elenolic acid , verbascoside , rutin , luteolin-7-glucoside , oleuropein , ligstroside (Ryan and Robards, 1998). The main phenolic compounds, hydroxytyrosol (0.5 214.4 mg/kg) and oleuropein (2 mg/kg), provide extra-VOO its bitter, pungent taste, and have powerful antioxidant activity as shown in both in vivo and in vitro studies (Tripoli et al., 2005; Cicerale, et al., 2009). It has been reported that phenolic compounds such as oleuropein, demethyoleuropein, and verbascoside are present in all parts of the fruit, but are mainly concentrated in the pulp (Ryan and Robards 1998). Other compounds such as nuzhenide are only present in the seed (Servili et al., 1999; Silva et al., 2010). Oleuropein is a combination of oleoside-11-methyl ester and hydroxytyrosol. Due to its secoiridoid phenolic structure it has a browning capacity and intense bitter taste. Its concentration increases during the growth phase, declines with the physiological development of the fruit, and decreases rapidly during black maturation phase. Its degradation is accompanied by accumulation of two derivatives, namely demethyoleuropein and elenolic acid glucoside (Amiot et al., 1989; Ryan et al., 2002). Hydroxytyrosol also increases during

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maturation as a maturation indicator. Oleosides (mainly oleuropein) undergo various degradation reactions during olive oil processing (Ryan et al., 2002). Phenolics are affected by the activity of hydrolytic enzymes that catalyze the liberation of aglycone secoiridoids from their respective glucoside forms (Servili et al., 2004) by the oxidative degradation that is catalyzed by polyphenoloxidases and peroxidases (Servili et al., 1999). The peroxidase showed highest activity at 37 C and polyphenol oxidase at approximately 50 C in VOO processing (Taticchi et al., 2013). On the other hand, reducing the oxygen concentration in the malaxer headspace inhibits the activity of such oxidoreductases (Taticchi et al., 2013). Many olive oil phenolics are subject to degradation upon the application of heat during cooking/frying at high temperatures (Cicerale et al., 2009). The phenolic fraction of VOO has generated high interest regarding its health promoting properties. Subsequent studies (in vivo and in vitro) have demonstrated that olive oil phenolics have positive effects on certain physiological parameters, possibly reducing the risk of chronic diseases that may be related to oxidative damage (coronary heart disease, stroke, and cancers) (Boskou et al., 2006; Cicerale et al., 2009; Covas et al., 2006; Visioli et al., 2002). It has been established that olive oil has beneficial effects on breast and colon cancer (Owen et al., 2000), diabetes accompanied by hypertriacylglycerolaemia, inflammatory, and autoimmune diseases such as rheumatoid arthritis (Alarcon de la Lastra et al., 2001). For example, oleuropein and hydroxytyrosol (the mostly studied phenolics) are also known to possess several biological properties such as antioxidant and anticancer effect (Simidou and Oskou, 2002; Bendini et al., 2007).

8.3.2 Lipophilic Bioactives 8.3.2.1 Squalene Squalene is a polyunsaturated hydrocarbon of the triterpene type (Fig. 8.2) which is liquid at room temperature. Due to its strong hydrophobic nature and its unsaturated structure, squalene is not very stable and gets easily oxidized (Spanova and Daum, 2011). Moreover, it protects polyunsaturated fatty acids against temperature-dependent autoxidation and UVA-mediated (320 2 380 nm) lipid peroxidation in olive oil (Dessı` et al., 2002). Although they show the same oxidation pattern, the reaction of temperature-dependent autoxidation is predominant, and squalene acts mainly as peroxyl radical scavenger (Kohno et al., 1995; Boskou, 2009). Squalene content in VOO is really high (up to 0.1% 2 0.8% w/w), as compared to other fats and oils (Lou-Bonafonte et al., 2012), however it decomposes by 26% 2 47% after 6 months of storage in the dark at room temperature (Manzi et al., 1998). Biological activities of squalene related to its emollient, skin hydration, antioxidant, antitumor properties, and its use in cosmetic dermatology are well-known (Huang et al., CH3

H3C

H3C CH3

H 3C

CH3

FIGURE 8.2 Structure of squalene, C30H50.

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CH3

CH3

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2009). During the past few years, the high squalene content of VOO has been proposed as a major factor in its cancer risk-reducing effect (Newmark, 2006; Waterman and Lockwood, 2007). In vitro and in vivo animal model studies suggest a tumor-inhibiting role of squalene (Newmark, 2006) and chemopreventive activity against colon carcinogenesis (Rao et al., 1998) has also been reported. Besides, the dietary intake differences of squalene has been suggested as a contributing factor to the differences against cancer mortality of Mediterranean countries (2002 400 mg/day) and the United States (30 mg/day), respectively (Newmark, 2006; Smith, 2000). 8.3.2.2 Phytosterols Sterols are integral components of the cell membrane, providing stability to the phospholipid bilayer which is generally characterized by a high proportion of unsaturated fatty acyl chains (Carland et al., 2010; Hartmann, 1998). Most of the free sterols of the cell reside in the plasma membrane, regulate the fluidity of plant membranes, play a role in the adaptation to temperature, and modulate the activity of membrane-bound enzymes. They are triterpenoid or isoprenoids, biosynthetically derived from squalene (via the isoprenoid biosynthetic pathway) (Piironen et al., 2000; Hartmann, 1998). Sterol molecules are incorporated into membranes with the 3 β-OH facing the water interface and the side chain extending into the hydrophobic core to interact with fatty acyl chains of phospholipids and proteins. Thus, they modulate the physical state of bilayers by restricting the motion of fatty acyl chains (ordering effect), which at physiological temperatures are in the liquidcrystalline phase. Active sterol synthesis occurs after seed germination to meet the needs for new membranes, as attested by the several-fold increase in free sterol concentration. The rate of sterol synthesis then gradually decreases with seed maturity (Hartmann, 1998). There are over 100 types of sterols identified in plant species, but the most abundant are β-sitosterol, stigmasterol, and campesterol (Carland et al., 2010). The basic sterol from which other sterol structures are defined is 5α-cholestan-3β-ol. In higher plants, sterols with a free 3β-hydroxyl group, are called free sterols. However, sterols also occur as conjugates in which the 3-hydroxyl group is either esterified (by a long-chain fatty acid to give steryl esters) or β-linked (to the 1-position of a monosaccharide, usually glucose) to form steryl glucosides or, when the 6-position of the sugar is esterified by a fatty acyl chain, acylated steryl glucosides (Hartmann, 1998). Therefore, sterols are present in plants in four forms: free sterols and conjugated forms which are sterol esters, sterol glycosides, and acyl sterol glycosides. In the human diet, sterol glycosides, like free sterols, inhibit the absorption of cholesterol from the gut, thus decreasing the risk of cardiovascular diseases (Christie, 2012). Phytosterols are crystalline solid at room temperature. They are soluble in vegetable oils and fats, as well as in nonpolar solvents such as hexane, iso-octane, and 2propanol and insoluble in water (Cantrill and Kawamura, 2008). Von Bonsdorff-Nikander et al. (2005) reported that the presence of an aqueous phase reduced cholesterol solubility in a variety of organic phases. β-sitosterol and mixed β-sitosterol-cholesterol crystals similarly were precipitated from oil by water (Jandacek et al., 1977). The most common phytosterol, β-sitosterol (Fig. 8.3), exists in three different crystal forms in solid state: anhydrate, hemihydrate, and monohydrate. In the presence of water, β-sitosterol recrystallizes as needle-shaped hemihydrate or monohydrate crystals. The monohydrated crystal form is

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8.3 OLIVE OIL BIOACTIVES

CH3

FIGURE 8.3 Structure of β-sitosterol, C29H50O.

CH3

H3C H

199

H

CH3

H

CH3 H

H

HO

unstable and tends to lose hydrated water even at room temperature. At temperatures below 60 C, approximately half of the water from crystallization left the structure and a hemihydrated form was observed (Von Bonsdorff-Nikander et al., 2005). Sterols are present in olive oil between 1000 and 2300 ppm (Ghanbari et al., 2012), whereas β-sitosterol is the most abundant one. Sterol composition of olive oil (as % of total sterols, w/w), as specified in the International Olive Council (IOC) Trade Standard, should be apparent β-sitosterol (β-sitosterol, Δ-5-avenasterol, Δ-5-23-stigmastadienol, clerosterol, sitostanol, Δ-5-24-stigmastadienol— $ 93%), brassicasterol (0.1%), stigmasterol (,campesterol), campesterol (#4.0%), and delta-7-stigmastenol (#0.5%) (IOC, COI/T.15/NC No 3/Rev.11, July 2016). Phytosterols and their fatty acid esters are quite stable compounds and undergo only limited degradation during oil processing. Only harsh conditions, such as high temperatures ( . 100 C) in the presence of oxygen may increase the oxidation rate (Zhang et al., ´ 2006; Cantrill and Kawamura, 2008; Rudzinska et al., 2009; Thanh et al., 2006). Stability tests, performed by heating at 50 C for several weeks and at 100 C for 1 h, did not show any significant variation in the phytosterol content (campesterol, β-sitosterol, and stigmasterol) of olive oil (Thanh et al., 2006). Phytosterols, in free or esterified form, are monounsaturated compounds (double bond in the B-ring), which are much more stable than the mono-unsaturated fatty acids (e.g., oleic acid), as the steric hindrance by the ring structure prevents chemical reactions. Phytosterol esters were found to be more susceptible to oxidation at elevated temperatures than free phytosterols (Cantrill and Kawamura, 2008) and to have higher solubility in fats and oils and more significant cholesterol-lowering activity compared to the free forms (Qianchun et al., 2011). Due to lower absorption in humans with respect to cholesterol, phytosterols reduce cholesterol absorption acting as cholesterol-lowering agents (Chan et al., 2007). Additionally, they exhibited anticancer properties in vivo on prostate, lung, stomach, colon, ovarian, and breast cancer (Woyengo et al., 2009). Dietary phytosterols retarded the growth and spread of breast cancer cells in mice, after 8 weeks resulting in a 33% tumor size reduction in addition to a 42% decrease in cholesterol absorption (Jones and AbuMweis, 2009). In an in vitro study, the tumor growth of a human colon cancer cell line was effectively inhibited by β-sitosterol (Awad and Fink, 2000). Prostatic hyperplasia (the enlargement of the prostate) is treated clinically with β-sitosterol-containing products in Europe (Berges et al., 1995). Phytosterol consumption may also increase the activity of antioxidant enzymes and thereby reduce oxidative stress (Woyengo et al., 2009).

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H3C H3C H3C

CH3

CH3 O

CH3

H3C

FIGURE 8.4 Structure α-tocopherol, C29H50O2.

of

OH CH3

8.3.2.3 Tocopherols Tocol-related compounds, tocopherols (α, β, δ, γ) and tocotrienols, which belong to the vitamin E family, are particularly important bioactive constituents in vegetable oils mainly due to their antioxidative effects. Tocopherols consist of a chroman ring and a long saturated phytyl chain (Fig. 8.4). Tocopherols are viscous oils at room temperature and are ¨ stu¨ndag˘ and Temelli, 2004). The plant slowly oxidized by atmospheric oxygen (Gu¨c¸lu¨-U chloroplast is the site of biosynthesis, and the aromatic amino acid tyrosine can be considered as the basic precursor of tocopherols (Christie, 2011). Tocopherols are sensitive to light, heat, alkali, and metals; therefore, they are easily oxidized to tocoquinones, which no longer have antioxidant properties. α-Tocopherol (Ferrari et al., 1996), is insoluble in water and soluble in oils, fats, and fat solvents. In VOO, 90% of tocopherols is α-tocopherol with up to 300 mg/kg concentration while others (β-, γ-, and δ-) are present in low amounts, up to 25 ppm (Ghanbari et al., 2012; Boskou et al., 2006). Total tocotrienols have been reported in trace amounts (,0.1 mg/ 100 g) in extra-VOO (Schwartz et al., 2008). Vitamin E is an efficient scavenger of alkoxyl and peroxyl radicals. It protects humans from the oxidative stress mediated by active oxygen and nitrogen species and prevents lipids and lipid-containing foodstuffs from oxidation during storage, thus extending their ´ stability and shelf life (Gliszczynska-´ swigło et al., 2007). α-Tocopherol is the most common form of vitamin E occurring in human blood and tissues and it has the highest biological activity among the tocopherols and tocotrienols (Boskou, 2009). High concentrations of α-tocopherol inhibit the oxidation of polyunsaturated fatty acids in plasma lipoproteins responsible for the initiation of atherosclerosis, decrease protein kinase C activity and modulate several pathways involved in prevention of atherogenesis (Traber and Packer, 1995). Moreover, it has been reported that α-tocopherol attenuates prostate cancer cell proliferation in cultured cells and mouse models (Morley et al., 2010), slows the progression of Alzheimer’s disease (Sano et al., 1997), and has a protective effect on upper respiratory tract infections (Meydani et al., 2012).

8.4 OLIVE OIL PRODUCTION Extraction of edible oils is typically performed using solvent free extraction (aqueous extraction and/or mechanical pressing) or using an organic solvent. Aqueous extraction contains three important processes; crushing, heating, and oil separation using a press or centrifuge. This method is not as effective as solvent extraction method. The advantage of solvent extraction is higher yield and flexibility to almost all materials. Hexane is the most

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widely used solvent today. Even though aqueous extraction provides lower yield, the market needs the less-processed products and hexane free oil due to loss of minor compounds providing bioactivity and sensory preference. Particularly, using higher temperature may result in degradation of flavor and aroma, giving heated or burnt odor. To tackle this issue, low temperature processes have been developed (Febrianto and Yang, 2011; Moral and Me´ndez, 2006). Olive oil extraction has a unique history from traditional to modern systems than other edible oils. In time, different grades of olive oils have been emerged based on their quality attributes and process types employed for their production; VOO, crude olive pomace oil, and refined olive oil. Flow diagram of the processing procedures used to obtain these oil types are given in Fig. 8.5. VOO is obtained by a mechanical process including aqueous extraction, washing, decantation, centrifugation, and filtration. Crude pomace oil is the oil obtained by treating olive pomace with solvents or other physical treatments (aqueous extraction). Refined olive oil and refined olive pomace oil are obtained from VOO and crude pomace oil by refining (IOC, COI/T.15/NC No 3/Rev.11, July 2016; Clodoveo et al., 2015). Lampant olive oil and second centrifugation olive oil are other types obtained by

Olives

Virgin olive oil

I. Aqueous extraction

Olive pomace

Storage Lampant olive oil II. Aqueous extraction

Solvent extraction

Second centrifugation oil

Crude olive pomace oil

Refining

FIGURE 8.5 Flow diagram of the processing procedures used to obtain the different types of olive oil. Source: Restructured from Brenes, M., Romero, C., Garcia, A., Hidalgo, J., Ruiz-Mendez, M.V., 2004. Phenolic compounds in olive oils intended for refining: formation of 4-ethylphenol during olive paste storage. J. Agric. Food Chem. 52 (26), 8177 8181.

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aqueous extraction without any chemical treatment. Lampant olive oil, oil with severe defects or produced from distorted olive fruits is not fit for human consumption due to its flavor and must be refined. However, it can be mixed with VOO (Brenes et al., 2004). A great proportion of the olive oil consumed worldwide consists of a mixture of refined olive oil and VOO (Moral and Me´ndez, 2006). Color, flavor, and cost of these products determine their use in the food industry, as cooking or salad dressing. The presence of the color pigments in VOO and their batch to batch variability also makes it difficult to produce products that have a certain color appearance if the oil is used directly (Febrianto and Yang, 2011).

8.4.1 Virgin Olive Oil Processing (I. Aqueous Extraction or Pressing) Traditional VOO processing is a physical extraction process using a press to extract oil from semisolid matrix formed by particles of the skin, pulp, and seed (Fig. 8.6). Modern continuous aqueous extraction process including crushing, malaxation (homogenization with thermal treatment), centrifugation (3-phase separation-oil, aqueous liquor, and solid waste), filtration, and sedimentation were introduced to increase oil yield. Remaining olive mill wastewater could not be disposed of due to its high humidity and organic load; and pomace generated from these systems (3-phase) needs extra water addition for second extraction. Finally, the 2-phase system which no water is added, generates oil; and a new semi- solid by-product was introduced to minimize water consumption due to environmental, economic, and quality considerations (Zbakh and El Abbassi, 2012; Ranalli and Martinelli, 1995; Boskou, 2012).

8.4.2 Olive Pomace Processing Pomaces from the traditional extraction system and those from the 3-phase extraction require different preconditioning procedures prior to solvent extraction than those coming from 2-phase systems (Fig. 8.4) due to their water content which is 25% 2 30%, 45%, and 55% 2 70%, respectively. High moisture content of 2-phase pomace leads to the need to

Olives

Cold water

Hot water*

Washing

Crushing malaxing

Waste water

Hot water**

Hot water*

Centrifugal decanting

Mechanical pressing**

Pomace**

Pomace***

*Press and 3-phase system **Only press system ***2-phase system

FIGURE 8.6 Flow chart of virgin olive oil extraction for press, 3-phase, 2-phase system.

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Waste water*

Olive oil

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8.4 OLIVE OIL PRODUCTION

Stone

Press and 3phase POMACE

2-phase POMACE

Pitting

Stone

II. Aqueous extraction

Drying

Pitting

Drying

Solvent extraction

Second centrifugation oil

Crude olivepomace oil

FIGURE 8.7 Flow chart of oil production from pomace (press and 3-phase, and 2-phase system). Source: Restructured from Moral, P.S., Me´ndez, M.V.R., 2006. Production of pomace olive oil. Grasas Aceites (Sevilla, Spain), 57, 47 55; Brenes, M., Romero, C., Garcia, A., Hidalgo, J., Ruiz-Mendez, M.V., 2004. Phenolic compounds in olive oils intended for refining: formation of 4-ethylphenol during olive paste storage. J. Agric. Food Chem. 52 (26), 8177 8181; Sec¸meler, O¨., Gu¨c¸lu¨ U¨stu¨ndag, ˘ O¨.G., 2017. Behavior of lipophilic bioactives during olive oil processing. Eur. J. Lipid Sci. Technol. 119, 1600404.

modify the basic operations of transportation, storage, and drying, making the process more expensive (Moral and Me´ndez, 2006; Ranalli and Martinelli, 1995). Crude pomace oil is produced in two ways (Fig. 8.7): 1. Solvent extraction: pomace oil is extracted from a dried pomace (8% moisture approximately) with solvent. The product obtained is the “crude pomace oil.” 2. II. Aqueous extraction (Second centrifugation): if the fresh or stored two-phase pomace is subjected to a second centrifugation, it is possible to extract between 40% and 60% of the residual oil. The oil obtained is known as “second centrifugation oil.” The pressed pomace and pomace from the 3-phase process must be directly subjected to drying immediately after leaving the mills in order to prevent rapid deterioration of the oil, particularly free acidity. The pneumatic removal of the stone is done just after drying. In the treatment of two-phase pomace, stone removal is prior to drying and is carried out using mills with filters with approximately 3 mm spaces, which allow solids smaller than this size to pass through. This process provides greater yield in the aqueous extraction including malaxation and centrifugation (Moral and Me´ndez, 2006). Crude olive pomace oil and second extraction oil have to be refined for edible use (Brenes et al., 2004). A volatile phenol with an unpleasant odor, 4-ethylphenol, has been discovered in all oils intended for refining (lampant, crude pomace, and second centrifugation oils). Its presence was particularly significant in second extraction oil, but its concentration increased with storage time of the olive paste, reaching up to 16 mg/kg after 3 months

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and 476 mg/kg of oil after 8 months (Brenes et al., 2004) by bacteria (Jones et al., 2000) and yeasts (Giannoutsou et al., 2004). The pomace plants, where pomace is reextracted, have been an important part of olive oil waste management. In addition to pomace oil, these plants produce dry pomace, pellets, and olive stones for use as fuel. However, the high water content (55% 2 65%) of the 2-phase system pomace makes it difficult to recover the oil from the pomace (Ranalli and Martinelli, 1995). Higher costs of drying and storing led the sector to set up integrated olive plants (consecutive pomace extraction after VOO extraction). Therefore, the oil content of the final waste stream decreased to 1% 2 1.5% and immediate processing of the 2-phase pomace eliminated the presence of unpleasant odor.

8.5 LOSS OF OLIVE BIOACTIVES, VOLATILE COMPOUNDS, AND AROMA INTENSITY DURING VOO PROCESSING Olive bioactives are partitioned between the oil and waste streams according to the processing conditions (such as malaxation time, temperature, decantation type) based on their ¨ stu¨ndag, ˘ 2017). chemistry, solubility, mass transfer behavior (Sec¸meler and Gu¨c¸lu¨ U Subsequently, the sensory profile of VOO is also affected by the oil extraction type, in addition to cultivar, crop year, geographic factors, fruit ripeness, and storage time (Koutsaftakis et al., 1999; Pe´rez-Camino and Cert, 1999; Kalua et al., 2007) because olive bioactives and aroma compounds undergo enzymatic and chemical transformations during olive oil production and new ones/derivatives formed. There are many studies focused on the effect of process conditions (such as malaxation time, temperature, decantation type) on olive bioactives but only a few studies determined their overall partitioning ¨ stu¨ndag, ˘ 2013; (Klen and Vodopivec, 2012; Rodis et al., 2002; Sec¸meler and Gu¨c¸lu¨ U Sec¸meler, 2017). The loss ratio of olive bioactives and their track depend on their chemistry, solubility, and mass transfer behavior. For example, the olive phenolics are more soluble in water than oil. Thus, more than 90% of the total phenolic content of the olive fruit are lost during VOO processing. Phenolics were distributed mainly in 2-phase pomace (65%) and OMW (olive mill waste water) (61%) due to their high water content (63% and ¨ stu¨ndag, ˘ 2013). Klen and Vodopivec (2012) reported that 90%) (Sec¸meler and Gu¨c¸lu¨ U 40% 2 50% of phenolics were already lost during crushing and/or malaxation due to oxidation of phenolics which is promoted by endogenous enzymes. Lignin, the part of the cell wall structure, is a complex macromolecule. Its structure belongs to a group of aromatic polymers containing bounded phenolic molecules giving rigid form to the cell wall (Vanholme et al., 2010). Olive stone (Rodriguez-Gutierrez et al., 2012), which is around 5% of the olive fruit (Niaounakis and Halvadakis, 2006), contains hemicellulose (22 2 28 g/100 g dry matter), cellulose (30 2 34 g/100 g dry matter), and lignin (21 2 25 g/100 g dry matter) as main components. In addition to furfural, decomposition of lignin yielded a high amount of phenolic compounds (ferulic acid, coumaric acid, vanillic acid, vanillin, syringaldehyde) using high temperature and high pressure techniques such as steam explosion (Rodriguez-Gutierrez et al., 2007, 2012; Rodrı´guez-Gutierrez et al., 2008, 2014). This means that the loss is higher than the ratio given above.

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Other bioactive cell components are the lipophilic ones: squalene, sterols, and tocopherols. The first partitioning study of lipophilic bioactives (squalene, β-sitosterol and α-tocopherol) was determined from an integrated olive milling plant consisting of the two consecutive extraction system, 2-phase system, and extraction of remaining oil (7% of the oil in the olives) from combined pomace by 3-phase system (Sec¸meler, 2017). According to this study, the loss of β-sitosterol (44%) and α-tocopherol (42%) were higher than that of squalene (12%) and oil (14%) due to their molecular interactions and cellular distribution. 10% of β-sitosterol and α-tocopherol present in the olives, which are mainly concentrated in the seed of the olive fruit and bound form in the plasma membrane, were lost in final pomace. 19% of the α-tocopherol and 21% of the β-sitosterol loss was unaccounted for, which can be attributed to degradation of α-tocopherol and incomplete recovery of sterols from the olive and pomace matrices. However, only 58% of the β-sitosterol could be extracted by hexane without acid hydrolysis (Sec¸meler, 2017). This means that the actual loss ratio of β-sitosterol is higher than 44% determined without acid hydrolysis due to unrecovered bound forms. Accordingly, the recovery of free sterols and bound sterols including glucoside forms can increase the value added, usage of olive pomace in addition to phenolics and oil recovery. Additionally, removing sterol glucosides is a big problem for biofuel production which is another value added utilization way of olive pomace. The most prominent volatile aroma compounds of VOO are formed by the reactions, taken place in the epicarp of olive fruits and catalyzed by lipoxygenase pathway (Sanchez and Harwood, 2002). In addition to extraction of oil, a complex set of enzymatic and physicochemical processes also initiate with crushing and continue to form other volatile aroma compounds during malaxation simultaneously. In addition to hydrophilic phenolic compounds, volatile compounds are also affected deleteriously as the temperature increases ( . 30 C) due to loss of enzymatic activity (Sanchez and Harwood, 2002; Servili et al., 2003; Kalua et al., 2007).

8.6 OLIVE OIL QUALITY 8.6.1 Olive Oil Standards International olive oil standards published by IOC and European Commission (EU) include standards for purity and quality. The olive oils must not be adulterated with any other type of oil, must pass a sensory analysis by a certified panel of tasters, and meet the analytical criteria (IOC, COI/T.15/NC No 3/Rev.11, July 2016; EU, No 61/2011). Purity criteria includes composition of fatty acid, sterol and triterpene dialcohol and desmethylsterol; trans fatty acid, total sterol, erythrodiol and uvaol, stigmastadiene, 2-glyceryl monopalmitate, triacylglycerol and wax contents; maximum difference between the actual and theoretical ECN 42 and unsaponifiable matter. Quality criteria includes organoleptic characteristics (color and taste), free acidity (good harvesting and handling), peroxide value, absorbency in UV, moisture and volatile matter, insoluble impurities in light petroleum, flash point, trace metals, and fatty acid methyl and ethyl esters (IOC, COI/T.15/NC No 3/Rev.11, July 2016). Additionally, IOC define phenols content as a quality parameter and give a reference method, but not any limit.

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Acceptable values of quality criteria change with grades of olive oil. The International Standards under resolution COI/T.15/NC no 3/Rev. 11 (July 2016) lists nine grades of olive oil in two primary categories—(1) olive oil and (2) olive pomace oil. These are the official definitions of each of the nine grades: Virgin olive oils (VOOs) are oils that are obtained from the fruit of the olive tree (O. europaea L.) solely by mechanical or other physical means under conditions, particularly thermal conditions, that do not lead to alterations in the oil, and have not undergone any treatment other than washing, decantation, centrifugation, and filtration. VOOs shall be classified as follows: VOOs fit for consumption as they are: extra-VOO, VOO, and ordinary VOO. VOOs that must undergo processing prior to consumption: lampante VOO, refined olive oil (olive oil obtained from VOOs by refining methods that do not lead to alterations in the initial glyceridic structure), and olive oil composed of refined olive oil and VOOs (a blend of refined olive oil and VOOs). Olive pomace oil is the oil obtained by treating olive pomace with solvents or other physical treatments, to the exclusion of oils obtained by reesterification processes and any mixture with oils of other kinds. It is marketed in accordance with the following designations and definitions: Crude olive pomace oil: olive pomace oil, the physicochemical and organoleptic characteristics of which correspond to those fixed for this category in this standard. It is intended for refining for human consumption, or it is intended for technical use. Refined olive pomace oil: oil obtained from crude olive pomace oil by refining methods that do not lead to alterations in the initial glyceridic structure. Olive pomace oil composed of refined olive pomace oil and VOOs: oil consisting of a blend of refined olive pomace oil and VOOs fit for consumption as they are. In no case shall this blend be called olive oil.

8.6.2 Sensory Quality One of the most important aspects of olive oil classification and value determination which is a prominent factor for consumer perception is sensory analysis. IOC published a standard (COI/T.20/Doc. No 15/Rev. 9 2017) to define the positive and negative attributes, only applicable to VOOs. Natural olive oil had classified as negative and positive in one of the study by Lo´pez-Feria et al. (2007). Eight negative (rancid, winey-vinegary, muddy sediment, hay-wood, vegetable water, earthy, fusty, and musty-humidity) and three principal positive attributes (fruity, bitter, and pungent) have been included (Lo´pezFeria et al., 2007). Positive attributes (fruity taste, bitterness, and pungent) depend on ripeness of the olive and its composition, therefore it depends also on true harvest. Different from positive attributes, negative attributes are: • fusty aroma due to long period storage before extraction; • musty-humid aroma due to large numbers of fungi and yeast as a result of storage at low temperature and high humidity; • muddy sediment aroma due to leaving the olive in contact with the sediment for a long time;

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• winey-vinegary aroma due to the process of fermentation in the olives, leading to the formation of acetic acid, ethyl acetate, and ethanol; • metallic aroma due to being in prolonged contact with metallic surfaces during crushing, mixing, pressing, or storage; and rancid aroma due to having undergone oxidation time (Kalua et al., 2007). As mentioned in part 3.1, there is a relation between phenolic content (hydroxytyrosol and oleuropein) of olive oil and its bitter and pungent taste.

8.6.3 Oxidative Stability The process of oxidation can follow enzymatic and/or chemical routes. Considering the autoxidation, photoxidation, and enzymatic oxidation, the most important external variables influencing oxidative stability are oxygen concentration, temperature, and light (Velasco and Dobarganes, 2002). The main processes leading to the deterioration of lipids are hydrolytic rancidity (lipolysis) and oxidative rancidity (oxidation). In olive oil, the former usually begins in the fruit, whereas the latter is mainly produced during the extraction process and storage. Hydrolytic rancidity is caused by the release of free fatty acids form glycerides, affecting taste. Oxidative rancidity leads to the formation of both unpalatable and toxic compounds and thus is nutritionally undesirable (Harwood and Aparicio, 2000). Olive oil is considered to be resistant to oxidation among edible oils due to low content of polyunsaturated fatty acids and the presence of natural antioxidants such as phenolics and α-tocopherol (Harwood and Aparicio, 2000).

8.7 UTILIZING HIGH ADDED-VALUE AND BIOACTIVE COMPOUNDS OF OLIVE OIL PRODUCTION DERIVATIVES As noted, olive fruit and corresponding by-products generated during olive oil production contain high amounts of phenolics, as well as other organic valuable compounds like pectin and lignin (Galanakis et al., 2010b,d,e; Rosello´-Soto et al., 2015a). These compounds have experimentally been extracted from different substrates (e.g., olive cake, kernel, or olive mill wastewater) and utilized as additives in different food products as well as for the production of nutraceuticals. To this line, the insoluble fraction of olive dietary fiber has been targeted as a source of fermentable sugars in order to fortify bakery products (Felizo´n et al., 2000), while the soluble fraction of dietary fiber (particularly pectin) has been proposed to replace fat replacement in meat products due to its ability to mimic gelling properties of fat (Galanakis et al., 2010a,c). Despite the promising results of these studies, olive polyphenols as bioactive and antioxidant compounds have attracted the main focus of the food industry (Rahmanian et al., 2014). Besides, the huge amounts of polyphenols lost in olive mill wastewater cause environmental problems in the Mediterranean area (Belaqziz et al., 2016; Regni et al., 2017; Souilem et al., 2017). The extraction of polyphenols from food processing by-products has been proposed using conventional techniques (Galanakis, 2012), membranes (Galanakis et al., 2015;

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Galanakis, 2015a,b), solvent extractions (Tsakona et al., 2012; Heng et al., 2016), as well as emerging technologies (Galanakis, 2013; Barba et al., 2015; Rosello´-Soto et al., 2015b; Kovacevic et al., 2018) that minimally affect sensorial and nutritional properties of the substrate (Zinoviadou et al., 2015). The recovery of polyphenols particularly from olive oil waste and by-products has also been proposed by similar approaches (Galanakis et al., 2010b,d; Galanakis and Kotsiou, 2017), whereas some of them have been patented or even commercialized. Ferna´ndez-Bolan˜os et al. (2006) recovered hydroxytyrosol from olive pomace and olive stone with two steps chromatographic purification and purified for food, drug, cosmetic, and agriculture usage. They recovered 85% by nonactivated ionexchange resin and then recovered 75% using nonionic resins in the second step. In addition to column chromatography, Villanova et al. (2009) used membrane systems including microfiltration, ultrafiltration, nanofiltration, and reverse osmose for purification of tyrosol and hydroxytyrosol, in order to use in cosmetic (milk, gel, and cream), nutraceuticals and beverage-based diet blends. De Magalha˜es et al. (2011) extracted hydroxytyrosol and other phenolic compounds from pomace, olive leaves, and olive stone by water or hydro alcoholic solvent extraction. Then the extract was subjected to phase separation by centrifugation. Solid phase was purified using supercritical carbon dioxide and reverse osmose technology, and liquid phase was purified using nanofiltration and reverse osmose membrane technology. Pizzichini and Russo (2005) pretreated the olive pomace by enzymatic hydrolysis (pectinase enzyme) to deactivate polyphenol oxidase (oxidation) and to prevent membrane stuck. Then solid phase was separated by centrifugation to use as biogas and soil regulator production. Liquid phase was purified by MF (membrane filtration), NF (Nano filtration), UF (ultra filtration) and RO (Reverse Osmosis) and 12 L pure polyphenol and 17 L concentrated polyphenol were produced from 200 L olive pomace. In addition to recovery of polyphenols from OMW and pomace, Tornbeg and Galanakis (2010) recovered pectin, a polysaccharide in pomace, which is used as a gelling and thickening in the food industry for years. Oil and water was separated by centrifugation and evaporation. Alcohol soluble polyphenols were extracted by two stage solvent extraction (ethanol: water) and concentrated by filtration (UF and NF). Nonalcohol soluble lignins, tanins, and polysaccharides were separated from soluble dietary fibers by centrifugation and then dietary fibers were separated by penetration. There are also studies focusing on recovery of lipophilic bioactives from deodorization distillates. For example, squalene, sterols, tocopherols and triglycerides have been recovered by serial processes which are ethyl ester formation, fractionation by distillation, purification by crystallization (Galanakis, 2017). In recent studies, using hydrothermal processes (steam, subcritical water, and supercritical water) for total recovery of olive wastes offer an innovative green approach. These processes are including recovery and extraction of olive phenolics (Ferna´ndez-Bolan˜os et al., 1999) and hydrolysis of lignocellulosic materials (hemicellulose, cellulose, lignin) of olive pomace, olive stone, and OMW for biofuel production (Mo¨ller et al., 2011; Garrote et al., 1999; Ferna´ndez-Bolan˜os et al., 1999; Ferna´ndez-Bolan˜os et al., 2001; Abu Tayeh et al., 2016; Kumar et al., 2009). Steam explosion (at 160 2 260 C, 0.69 2 4.83 MPa) of olive pomace is used to increase oil yield and sterols due to solubilization of cell wall material and release of bound oil and sterols, to breakdown the lignocellulosic matrix and lignin-carbohydrate bonds to recover the major phenols (hydroxytyrosol and tyrosol) and dietary fiber and to enhance

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enzymatic hydrolysis of cellulose. In a separate liquid fraction containing water soluble phenolic compounds and carbohydrates, hydroxymethylfurfural and furfural are formed by degradation of monosaccharides at higher temperatures (Manorach, 2014; Ferna´ndezBolan˜os et al., 1998, 1999, 2001, 2004; Rodrı´guez et al., 2008; Rodrı´guez-Gutie´rrez et al., 2014; Rodrı´guez-Gutie´rrez et al., 2007; Lama-Mun˜oz et al., 2011). Steam pretreatment also used in combination with acid hydrolysis, ultrafiltration, and column chromatography to recover concentrated phenols and oligosaccharides (Rubia-Senent et al., 2013). Subcritical water extraction is an effective reaction medium/solvent for the total valorization of olive pomace, which offers the advantage of semicontinuous processing and the recovery of multiple fractions. It has been studied to recover phenolic compounds from olive pulp (160 C, 30 min) and was found more efficient than methanol extraction (2 h) (Yu et al., 2014). Steam explosion and subcritical water reaction medium were used and compared for value added utilization of olive pomace to obtain sterol enriched oil and phenols by Sec¸meler (2017). The effect of pretreatment method (steam and subcritical water), and temperature (160, 180 and 200 C, 5 min) on oil, β-sitosterol and phenol recovery from olive pomace were investigated in this dissertation. 54% 2 76% of the bound oil and 18% 2 32% of the bound β-sitosterol of the pomace were recovered by steam and subcritical water pretreatment. As the operating temperature increases, significant effectiveness of steam pretreatment related to subcritical water was decreased so that subcritical water showed an increasing trend on oil yield related to steam pretreatment. The pretreated biomass, which would be free of sterol glucosides and phenols, could be further utilized for biofuel production, although to a limited extent if the samples are rich in sterol glucosides (Songtawee et al., 2014). According to these studies, sequential processes with different temperatures and pretreatments might be investigated for total valorization of olive pomace.

8.8 CURRENT STATUS QUO OF INNOVATIONS IN OLIVE OIL SECTOR 8.8.1 Marketing Olive Oil as a Superfood Olive oil, the production of olive fruit extraction, is the pillar of the Mediterranean diet and its consumption is well-known to provide multiple benefits to our health (e.g., for the cardiovascular system) (Galanakis, 2011). Olive oil is nowadays highlighted and marketed as a superfood for human health not only due to its lipid profile (e.g., high oleic acid and low saturates), but also due to its high content in micronutrients such as squalene and polyphenols (Galanakis, 2017). The latter powerful antioxidants are in many cases advertised almost as an elixir that promises to relieve us against multiple diseases and health problems. Which of these advertised health claims have a scientific basis and how many of them are promises or just guesses? Over the last two decades, olive oil has concentrated scientific attention not only in the Mediterranean area, but all around the world due to its beneficial effects in human health (Rahmanian et al., 2014). This trend is mainly driven by its content in polyphenols.

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Hydroxytyrosol, tyrosol, oleuropein, eleocanthal, oleacein, and other polyphenols with exotic names may not be well-known to the general public yet, but they already appear in the product labels in the shelves of supermarkets and pharmacies, promising to provide multiple benefits to consumers. Polyphenols pass from the olive tree to olive fruit, olive oil, and olive processing byproducts (olive tree leaves and olive mill wastewater) (Souilem et al., 2017). Recent biochemical, pharmacological, and other studies have shown that polyphenols possess strong radical scavenging capacities and can play an important role in protecting against oxidative damages and cellular aging (Galanakis, 2018). By far the most investigated olive oil polyphenol is hydroxytyrosol. Studies have been conducted in both cells and animals, whereas its antioxidant effect is nowadays taken for granted. Besides, hydroxytyrosol is currently in early clinical trials as a dietary supplement for patients with multiple sclerosis and as a measure preventing breast cancer in women with a relevant genetic predisposition. Oleuropein, which is mainly contained in the olive tree leaves, has also been investigated a lot. Oleocanthal, a tyrosol derivative whose antiinflammatory role was found similar to that of the drug Ibuprofen in 2005, have also shown important bioactivities (e.g., against Alzheimer’s disease, several cancers etc.), although most studies have been performed in cells and few of them in animals, thus it has not yet been fully evaluated (Galanakis, 2017). Despite the so far promising results, the main weakness for these investigations is that their outcomes are to a great extent not systematically addressed. Olive oil is an extremely complex mixture of ingredients and thus it is not clear if findings based on experiments conducted with free compounds (e.g., hydroxytytorosol and oleuropein that exist in minute quantities in olive oil) can be extended to actual major constituents and olive oil (a natural product with great variability in composition). The problem of the levels of individual bioactive compounds in olive oil and the possible combined effects of various classes of bioactive compounds have not yet been answered. In addition, the vast majority of the available studies have so far been conducted either in vitro or in vivo (Galanakis, 2017). Very few of them have been performed in reliable clinical trials in humans. The latter constitute the necessary test to prove the efficacy and safety of a component.

8.8.2 The Health Claim of Polyphenols in Olive Oil and Its Ambiguous Interpretation Those consumers, who are observant and check more olive oil packages, have mentioned that some of the labels indicate that olive oil contains substances that shield the human body against various health problems. Besides, since 2012, olive oil can be labeled with a health claim approved of the European Authority for Food Safety (EFSA) and is strictly defined by the EU regulation 432/2012 as follows: “Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress” (EU, No 432/2012). However, this claim can only be used for olive oils containing at least 5 mg of hydroxytyrosol and its derivatives (e.g., oleuropein complex and tyrosol) per 20 g of olive oil. In addition, the label must provide information to the consumer that the beneficial effect is obtained with a daily intake of 20 g of olive oil (about one and a half spoon).

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This European regulation is somehow ambiguous since the list of hydroxytyrosol derivatives is not referred and the determination method is not defined. The official determination method of the International Olive Oil Council is based on high performance liquid chromatography with UV detection. This ambiguity generates implications in the market. On one hand, some phenols are named as hydroxytyrosol derivatives, while others that are actually derivatives are sometimes advertised for activities that are not approved. At the same time, some commercialized olive oils indicate other false benefits that do not comply with EFSA rules.

8.8.3 Polyphenols From Olive Mill Wastewater: A Great or a Stifled Opportunity? The situation becomes even more complicated taken into account that olive mill wastewater is richer in polyphenols compared to olive oil. This fact led the researcher to consider this waste stream as a cheap source of antioxidants. Indeed, the first animal experiments and a couple of human studies have confirmed the bioactivity of extracts derived from this source and subsequently relevant dietary supplements appeared in the market (e.g., Hidrox, OlivActive, Oleaselect, Opextan, Prolivols, Phenolea Complex, and others) (Galanakis, 2015a,b, 2017). Nowadays, at least five companies around the world have commercialized methodologies for the recovery of polyphenols from olive mill wastewater (Galanakis and Schieber, 2014) in order to merchandize them as natural preservatives and bioactive agents. Applications of polyphenols include the fortification of different products such as vegetable oils (Galanakis et al., 2018b), bakery (Galanakis et al., 2018a) and meat products (Galanakis, 2017), cosmetics, sunscreens (Galanakis et al., 2018c, d), and others. Many commercial products involving hydroxytyrosol are marketed already in the United States, and the U.S. Food and Drug Administration (FDA) granted generally-recognized-assafe status and allowed their usage as antioxidants in baked goods, beverages, cereals, and other foods at a level of up to 3000 mg/kg. In Europe, EFSA handles health claims of hydroxytyrosol-containing products in a preserved manner and has tightened up the way in which companies can advertise health benefits. Indeed, health claims have only been approved for olive oils rich in hydroxytyrosol. If you recover hydroxytyrosol from olive mill wastewater and fortify a food product (e.g., bakery products) or even an olive oil, the health claim is not valid. This policy is driven by the need to protect consumers from claims that lack scientific depth and evidence. However, the significantly different approach of market release between FDA and EFSA influences substantially the olive oil industry growth in EU. Demonstration of proven health benefits is very costly for the companies activated in the field. This fact creates implications for stifling innovation in the field, as the obtainment of the required data to prove health benefits is not affordable and most companies (typically start-ups with low funding) cannot afford them. Besides, the risk of claims rejection by the corresponding authority is too high. With all of these ambiguities and unknown parameters (solid evidence in clinical trials is yet to be gathered), still no one can claim the development of medicines from olive oil

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components. Olive oil is a superior food providing health benefits, whereas extracts derived from olive oil processing by-products can be considered as powerful nutritional supplements. However, both are neither medicine nor can be considered as sources for the development of medicines. This is something to be highlighted and may be proved (or not) over the next years. The current scientific evidence suggests that choosing an extra-VOO rich in polyphenols would contribute to the dietary intake of micronutrients in quantities that have been correlated with a reduced risk of developing coronary heart disease. Nevertheless, since polyphenols are more and more linked to the quality of olive oil and human health, they will continue to drive innovations and advances in the market. Thereby, it is only a matter of time that researchers will clarify the potential health benefits of the relevant compounds and extracts. Subsequently, authorities around the world will stand over the above issues and harmonize specifications, for example, by setting qualitative limits for polyphenols according to data from well-defined determination methods, by defining in details the derivatives of hydroxytyrosol and by providing a way out for the polyphenols recovered from olive oil processing by-products.

8.9 CONCLUSION The disposal of olive mill wastewater and olive pomace is an environmental and economic problem that still cannot be entirely solved in practice. Olive oil is a traditional food and has a long history from stone mill-cold press to hammer crusher-two phase centrifugation and refination. Because oil is the single added value in this sector, the primary concern in the innovative studies and of course the industry of olive oil production is to increase the oil yield rather than sensory quality and bioactive constitutes. This fact decreases the attractiveness of olive oil in spite of its positive health effects. In other words, current innovations in olive oil leads to loss of its traditional nature, which in turn causes loss of its competitive advantages and the added value that it provides to consumers. Nowadays, it is possible to evaluate the lignocellulosic materials (hemicellulose, cellulose, lignin) as well as bioactive substances (phenolics, sterols, triterpenic acids, oligosaccharides) of olive oil production wastes with different purposes such as biofuel, and to ¨ stu¨ndag, ˘ 2015). Thus, food obtain more than one product (Fig. 8.8) (Sec¸meler and Gu¨c¸lu¨ U waste loss will be reduced and added value will be provided in the sector. The valorization olive mill processing by-products could help olive oil industries to solve environmental and sustainability issues accompanied with the disposal of these streams. At the sample, utilizing the bioactivity of target components exist in both olive oil and processing by-products could help industries to develop new products, and innovate substantially in a sector that was always considered to be traditional. Current legislative constraints with regard to health claims of olive bioactives could be overpassed using nutritional claims and developing a vast variety of natural products in foods and cosmetics by considering sensory quality and consumer perception.

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Waste valorization chain of olive oil sector. Source: Restructured from Sec¸meler, O¨., Gu¨c¸lu¨ U¨stu¨ndag, ˘ O¨.G., 2015. Valorization of Wastes and Byproducts of Olive Oil Production (in Turkish), Du¨nya Gıda Dergisi, Mayıs.2015/90-98.

FIGURE 8.8

References Abu Tayeh, H., Levy-Shalev, O., Azaizeh, H., Dosoretzi, C.G., 2016. Subcritical hydrothermal pretreatment of olive mill solid waste for biofuel production. Bioresour. Technol. 199, 164 172. Alarcon de la Lastra, C., Baranco, M.D., Motilva, V., Herrerias, J.M., 2001. Mediterranean diet and health: biological importance of olive oil. Curr. Pharm. Des. 7, 933 950. Amiot, M.-J., Fleuriet, A., Macheix, J.-J., 1989. Accumulation of oleuropein derivatives maturation. Phytochemistry 28 (1), 67 69. Awad, A.B., Fink, C.S., 2000. Phytosterols as anticancer dietary components: evidence and mechanism of action 1, 2. J. Nutr. 2127 2130. Barba, F.J., Galanakis, C.M., Esteve, M.J., Frigola, A., Vorobiev, E., 2015. Potential use of pulsed electric technologies and ultrasounds to improve the recovery of high-added value compounds from blackberries. J. Food Eng. 167, 38 44. Belaqziz, M., El-Abbassi, A., Lakhal, E.K., Agrafioti, E., Galanakis, C.M., 2016. Agronomic application of olive mill wastewaters: effects on maize production and soil properties. J. Environ. Manage. 171, 158 165. Bendini, A., Cerrentani, L., Carrasco-Pancorbo, A., Gomez-Caravaca, A.M., Segura-Carretero, A., FernandezGutierrez, A., et al., 2007. Phenolic molecules in virgin olive oils: a survey of their sensory properties, health

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