Cold Pressed Oils: Green Technology, Bioactive Compounds, Functionality, and Applications

Cold Pressed Oils: Green Technology, Bioactive Compounds, Functionality, and Applications creates a multidisciplinary forum of discussion on recent advances in chemistry and the functionality of bioactive phytochemicals in lipids found in cold pressed oils. Chapters explore different cold pressed oil, focusing on cold press extraction and processing, composition, physicochemical characteristics, organoleptic attributes, nutritional quality, oxidative stability, food applications, and functional and health-promoting traits. Edited by a team of experts, the book brings a diversity of developments in food science to scientists, chemists, nutritionists, and students in nutrition, lipids chemistry and technology, agricultural science, pharmaceuticals, cosmetics, nutraceuticals and many other fields.

• Thoroughly explores novel and functional applications of cold pressed oils
• Shows the difference between bioactive compounds in cold pressed oils and oils extracted with other traditional methods
• Elucidates the stability of cold pressed oils in comparison with oils extracted using other traditional methods

• Language: English
• Publisher: Academic Press
• Release date: Jul 23, 2020
• ISBN: 9780128181898

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Chapter 1: Introduction to cold pressed oils: Green technology, bioactive compounds, functionality, and applications

Mohamed Fawzy Ramadan    Agricultural Biochemistry Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt

Abstract

Cold pressing is a technique that offers a safe, nonhazardous method for edible oil extraction and processing in which the bioactive constituents are preserved through the omission of thermal and chemical treatments as well as refining processes. This book aims at building a multidisciplinary forum of discussion on advances in cold pressed oil technology, chemistry, and functionality of lipid bioactive phytochemicals found in cold pressed oils focusing on oil processing, composition, physicochemical properties, nutritional quality, organoleptic attributes, oxidative stability, food and nonfood uses, as well as health-promoting traits.

Keywords

Cold pressed; Vegetable oils; Healthy oils; Lipid technology; Lipid chemistry

1: Introduction

In 2015, the United Nations Sustainable Development Goals (UNSDGs) were announced (https://sustainabledevelopment.un.org). These seventeen goals offer a vision of a fairer, peaceful, more prosperous, and sustainable world. They imagine a future that will be free of hunger and poverty, and safe from the worst impact of environmental hazard and climate change. In food—the way it is grown, processed, transported, stored, marketed, and consumed—lies the fundamental connection between people and the path to sustainable economic development. The third UNSDG, Good Health and Well-Being, aims to promote a healthy life and human well-being which is closely related to the use of environmentally friendly processing techniques in food systems as well as the functionality of foodstuffs.

We live in an era where rapid innovations are being made, and these unique technologies could be applied to enhance our edible system. Scientists are searching for new foodstuffs that have properties that can be manipulated and designed at the molecular level to improve their safety, quality, and healthfulness. The scientific research being performed now will have a great effect on the way we eat in the future (McClements, 2019).

Traditional methods of oil extraction use excessive amounts of organic solvents and need high-energy input. Current environmental issues associated with organic solvent disposal demand alternative methods for the extraction of edible oils that are environmentally friendly and energy-efficient. Green technologies identified some alternative methods suitable for edible oil extraction. This has led to the improvement of more energy-efficient and eco-friendly green techniques that reduced the utilization of toxic organic solvents and enabled high-quality products to be developed.

The green extraction methods, including cold pressing extraction (CPE), ultrasonic-aided extraction (UAE), microwave-aided extraction (MAE), subcritical extraction (SWE), and supercritical extraction (SFE), have received attention due to their eco-friendliness and energy efficiency. These green extraction techniques are applied to minimize the utilization of toxic organic solvents, and to extract bioactive lipid-soluble compounds, with the focus on developing a better-quality final product. These benefits have been welcomed by the oilseed industry and manufacturers.

Edible unrefined oils include cold pressed oils (CPO) and virgin oils. Unrefined oils are a category covered by technical regulations in the field of edible oils (Codex, 1999): Cold pressed unrefined vegetable oil is produced without heating, precleaning, dehulling and milling mechanically. Cold pressed unrefined oil can only be purified by washing with water, precipitating, filtrating and centrifuging.

2: Green technologies and processing of vegetable oils

All technologies to eliminate the use of hazardous toxic solvents and chemicals refer to green technology. One definition of green technology is as follows: Green Extraction is based on the discovery and design of extraction processes which will reduce energy consumption, allows the use of alternative solvents and renewable natural products, and ensure a safe and high-quality extract. The Six Principles of Green Extraction of Natural Products are directions to build an innovative and green label and standard.

•Principle 1: Variety selection and use of renewable plant resources.

•Principle 2: Reduce energy consumption using innovative technologies and energy recovery.

•Principle 3: Use alternative solvents (water or agro-solvents).

•Principle 4: Reduce unit operation and favor a safe and controlled process.

•Principle 5: Produce coproducts to include the agro-refining industry.

•Principle 6: Aim for biodegradable and nondenatured extracts without contaminants.

Extraction, according to these principles, is a new concept to protect the consumer and environment, and enhance the competitiveness of industries to be more economic, innovative, and ecologic (Chemat, Vian, & Cravotto, 2012). Many studies have been conducted to find and apply research techniques related to green technology in different applications.

The use of alternative nontraditional techniques of oil extraction has gained attention during the last years. These novel techniques have been applied in the oilseed industry to minimize detrimental changes in the nutritional quality and physicochemical and sensory traits of the extracted oils while reducing the carbon footprint from solvents (Matthäus & Brühl, 2003).

Conventional oil extraction methods are replaced by modern ones, usually called green or clean techniques, because of the long time requirement and high solvent consumption of the former (Chemat et al., 2012; Parker, Adams, Zhou, Harris, & Yu, 2003; Rodríguez-pérez, Quirantes-piné, & Fernández-gutiérrez, 2015; Tiwari, 2015). Pressurized liquid (PLE), pulsed electric field (PEF), high hydrostatic pressure (HHP), high voltage electrical discharges (HVED), SFE, UAE, and MAE are green technologies considered as alternatives to conventional methods (Soquetta, Terra, & Bastos, 2018). According to the Codex Alimentarius, cold pressing is performed only by mechanical processes without thermal application, and the product is produced without destroying the oil nature (Matthäus & Spener, 2008).

3: Advantages versus disadvantages of cold pressing technology

Methods utilized for oil extraction might alter minor compounds that have functional traits and contribute to oil oxidative stability. Recently, CPO has increasingly been considered as these oils have high nutritional values. Vold pressing techniques are becoming an interesting substitute for traditional methods because of consumers’ desire for safe and natural edible products (El Makawya, Ibrahimb, Mabrouka, Ahmedc, & Ramadan, 2019; Kiralan, Çalik, Kiralan, & Ramadan, 2018; Ramadan, 2013).

The advantages of this technology at an industrial level include lower energy consumption and lower investment cost. This extraction does not use toxic solvents or thermal conditioning of the seeds, and does not generate wastewater. It ensures a safe working environment for employees, has a lower environmental impact in comparison with solvent extraction, and shows higher flexibility because processing diverse types of seeds is fast and easy. CPO are preferred to refined oils as they contain more antioxidants and bioactive substances like sterols, carotenoids, and phenolics. More natural biologically active substances such as phenolic compounds and tocols are present in CPO, which could improve oxidative stability (Bhatnagar & Krishna, 2014; Prescha, Grajzer, Dedyk, & Grajeta, 2014).

The main disadvantage of cold pressing techniques is the high capital or investment required compared to conventional methods. In addition, CPO have low efficiency and are not always of the same quality. Most CPO contain high amounts of polyunsaturated fatty acids (PUFA), which might be disadvantageous in terms of oxidative stability. CPO could also contain higher amounts of pro-oxidative compounds, so their shelf life might be shorter compared to refined oils (Brühl, 1996; Rotkiewicz, Konopka, & Żylik, 1999).

4: Cold pressing process

Vegetable oils can be obtained from oilseeds using different systems of the press, solvent extraction, or a combination of both methods. Seeds contain high amounts of oil are prepressed then solvent extracted, or direct solvent extraction could be performed on seeds with lower oil content. The extraction technology can be selected depending on the production cost, material traits, availability, usage goal of the cake, and environmental factors (Ghazani, Garcia Llatas, & Marangoni, 2014; Matthäus & Brühl, 2003; Sloan, 2000).

Based on the oilseed structure and composition, some fractions of oil might remain in the meal or cake. This should be considered when comparing the press and cold press for the oil yield and meal composition. To increase the oil yield from cold pressing, some pretreatments could be applied to seeds before pressing, such as enzyme application, microwave treatment, steaming, and roasting. Cold pressed virgin oils do not require expensive refining. Only centrifugation or filtration is necessary to obtain high-quality CPO. Minor bioactive lipids that are commonly lost during refining are retained in CPO. A producer could select the production type based upon the aim of production, uses of oil and cake, and the amount of processed seeds.

The cold press machine has a simple working scheme wherein oilseeds are fed into one inlet, and two exits provide oil and a nonoiled cake. Oil yield depends on pretreatment (i.e., peeling, drying, and enzymatic treatment) and process parameters applied to the oilseeds or raw materials. Cold pressing could be investigated under three main systems: expellers, expanders, and twin-cold systems (for pilot- or laboratory-scale production) (Çakaloğlu, Özyurt, & Ötleş, 2018).

5: Features and specific phytochemicals of cold pressed oils (CPO)

The contribution of lipid-soluble bioactives to human health is determined by their composition. Fatty acids profile (especially omega-9, omega-6, and omega-3) and high-value minor lipid compounds (i.e., tocols, sterols, glycolipids, phospholipids, aroma compounds, and phenolics) exhibit health-promoting traits and positively influence the biological functions of our body (Ibrahim, Attia, Maklad, Ahmed, & Ramadan, 2017; Kiralan et al., 2017).

The techniques used to extract oils as well as the processing steps such as bleaching, refining, and deodorization influence their bioactive constituents. CPO usually contain unique phytochemicals with health-promoting traits. For example, cold pressed pomegranate seed oil contains punicic acid (C18:3-9cis, 11trans, 13cis), and α-eleostearic. Punicic acid, also known as tricosanic acid, is an omega-5 long-chain PUFA and a conjugated α-linolenic acid isomer with structural similarities to conjugated linoleic acid and α-linolenic acid (Costa, Silva, & Torres, 2019; Lansky & Newman, 2007; Viladomiu, Hontecillas, Yuan, Lu, & Bassaganya-Riera, 2013). The potential health benefits of these conjugated fatty acids have made them increasingly interesting for scientists and consumers (Carvalho, Melo, & Mancini-Filho, 2010; Grossmann, Mizuno, Schuster, & Cleary, 2010).

Another example is pinolenic acid (PNLA; all cis-5,-9,-12-18:3), which is found in cold pressed pine nuts oil. This acid, constituting 14%–19% of fatty acids in pine nuts, is the basic polymethylene interrupted fatty acid (Δ5-UPIFA) (Destaillats, Cruz-Hernandez, Giuffrida, & Dionisi, 2010; Ryan, Galvin, O’Connor, Maguire, & O’Brien, 2006; Wolff & Bayard, 1995). Pinolenic acid has antiinflammatory traits that protect and strengthen the stomach and stomach lining (Chen, Zhang, Wang, & Zu, 2011; Xie, Miles, & Calder, 2016). Cold pressed Korean pine nuts oils are used as nutritional supplements thanks to pinolenic acid and antioxidants.

6: Cold pressed oils (CPO) in the literature

A careful search on cold pressed oils (as keywords) in the titles, abstracts, and keywords of publications in the Scopus database (www.scopus.com) revealed that the total number of scholarly outputs published is high (c.975 as of December 2019). Apart from the total published scholarly outputs, c.600 were research articles and c.200 reviews. Fig. 1 shows the scholarly output on CPO since 2000. It is clear that the scholarly output published annually on CPO has increased dramatically over the last two decades, from 11 articles in 2000 to 97 article in 2019. The publications were mainly related to the subject areas of agricultural and biological sciences, biochemistry, genetics and molecular biology, chemical engineering, chemistry, and engineering. The United States, Poland, China, Italy, Turkey, Japan, Germany, Egypt, and Canada have emerged as main contributors. The most prolific journals were the Journal of Agricultural and Food Chemistry, European Journal of Lipid Science and Technology, Journal of Food Science, Food Chemistry, and Journal of the American Oil Chemists Society. On the other side, the sum of annual citations (2009–19) from articles published on CPO have significantly increased during the last 10 years (Fig. 2). These measurable indicators reflect the importance of cold pressed oils as a topic in the international scientific community.

Fig. 1 Scholarly output on cold pressed oil since 2000 ( www.scopus.com ).

Fig. 2 Total number of annual citations (2009–19) from articles published on cold pressed oil ( www.scopus.com ).

Several books have already been published on the composition and functional properties of oils and fats from herbs, oilseeds, medicinal plants, animal sources, and marine sources. However, it is hard to find a book focused on the composition and functionality of CPO. This book contains comprehensive chapters focusing on CPO, which contain unique bioactive components that have led to their being considered health-promoting oils. The following chapters describe several CPO. Each chapter is dedicated to a particular cold pressed oil. Most CPO have unique composition and characteristics that make them valuable sources for novel foods, nutraceuticals, and pharmaceuticals. The chapters have the following topics:

•Cold press extraction and processing of oils

•CPO recovery, content, use of oil cake, and economy

•Fatty acids composition and acyl lipids profile of CPO

•Minor bioactive lipids (carotenoids, phenolics, sterols, tocols, hydrocarbons, aroma compounds) in CPO

•The contribution of bioactive constituents in CPO to organoleptic traits

•Applications of CPO

•Health-promoting properties of CPO and oil constituents

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El Makawya A.I., Ibrahimb F.M., Mabrouka D.M., Ahmedc K.A., Ramadan M.F. Effect of antiepileptic drug (Topiramate) and cold pressed ginger oil on testicular genes expression, sexual hormones and histopathological alterations in mice. Biomedicine & Pharmacotherapy. 2019;110:409–419.

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Chapter 2: Minor bioactive lipids in cold pressed oils

Dilşat Bozdoğan Konuşkan    Food Engineering Department, Faculty of Agriculture, Hatay Mustafa Kemal University, Hatay, Turkey

Abstract

Recently, cold pressed oils have been preferred to refined oils due to their natural, characteristic flavor and their minor bioactive compounds including natural antioxidants. These minor bioactive lipids that are naturally found in cold pressed oils are phytosterols, phospholipids, tocopherols, phenolic compounds, hydrocarbons (squalene), pigments (carotenoids and chlorophyll), and flavor and aroma compounds. The minor bioactive lipids in cold pressed oils have beneficial effects on human health such as antiinflammatory, antimicrobial, anticancer, antihypertension, and lowering of low-density lipoprotein. Furthermore, these bioactive compounds play an important role in prolonging the shelf life of the cold pressed oils by the increase of oxidative stability of the oil. This chapter highlights the minor bioactive compounds found in cold pressed oils and their functional traits.

Keywords

Bioactive lipids; Phytosterols; Phenolic compounds; Tocols; Carotenoids; Chlorophyll

1: Introduction

Nowadays consumers prefer natural and healthy, beneficial food products (Ananth, Deviram, Mahalakshmi, Sivasudha, & Tietel, 2019). Cold pressed oil is one of these products. In recent years, cold pressing has become the preferred method for oil extraction from oilseeds and fruits. This method is also user-friendly and inexpensive compared to other extraction methods (Ananth et al., 2019; Ramadan, 2013). Cold pressed oils refer to oils that are extracted by oil extraction without heat and chemical treatment, which may contain a higher amount of minor bioactive compounds, including natural antioxidants, than other refined oils (Bozdogan Konuskan, Arslan, & Oksuz, 2019; Teh & Birch, 2013). These minor bioactive lipids that are naturally found in cold pressed oils are phytosterols, phospholipids, tocopherols, phenolic compounds, hydrocarbons (squalene), pigments (carotenoids and chlorophyll), and flavor and aroma compounds (Gao, Liu, Jin, & Wang, 2019; Gornas, Siger, & Seglina, 2013; Mildner-Szkudlarz, Rozanska, Siger, Kowalczewski, & Rudzinska, 2019). Minor fractions play an essential role in determining the nutritional and health impact of edible oils (Teh & Birch, 2013). Cold pressed oils are more resistant against lipid oxidation and they have a higher initial oxidation level due to their natural antioxidants (Grosshagauer, Steinschaden, & Pignitter, 2019).

2: Phytosterols

Phytosterols, also called plant sterols, constitute the major proportion of the unsaponifiable fraction of lipids (Wasowicz, 2003; Yang, Oyeyinka, Xu, Ma, & Zhou, 2018), which can occur in vegetable oils either in free form or esterified with fatty acids (Manai-Djebali & Queslati, 2017). Phytosterols are by-products of the isoprenoid biosynthetic pathway via squalene from acetyl coenzyme-A. The phytosterols are cell membrane structural compounds found in the regulation of membrane fluidity, permeability, and metabolism (Shahzad et al., 2017). Based on the chemical structure, phytosterols can be classified into three groups: 4-desmethylsterols (cholestane series, i.e., normal phytosterols), 4-monomethylsterols (4 α-methylcholestane series), and 4,4-dimethylsterols (lanostane series, also known as triterpene alcohols) (Manai-Djebali & Queslati, 2017; Wasowicz, 2003). Generally, plant sterols are 4-desmethylsterols because they do not contain any methyl groups at the fourth position of the sterol ring structure (Moreau et al., 2018). Phytosterols are a family of triterpenes comprising of a 27–30 carbon ring-based structure with hydroxyl groups, and they are highly similar to cholesterol in both structure and biological function (Figueiredo et al., 2018; Shi et al., 2019). Phytosterols consist of a tetracyclic structure and a side chain in position C-17 (Manai-Djebali & Queslati, 2017; Moreau et al., 2018).

Free phytosterols contain a double bond in the B-ring between C-5 and C-6, or C-7 and C-8, also called Δ⁵- and Δ⁷-sterols, while the place of the double bond in the ring is characteristic to specific plant types (Moreau et al., 2018). Phytosterols with a saturated ring structure, called stanols, occur in nature in minor concentrations (Wasowicz, 2003).

The oxidation products of phytosterols in vegetable oils were identified and quantitated by Dutta and Appelqvist (1997). These are 7α and 7β hydroxy-sito-and campesterol, 7-ketosito and 7- ketocampesterol, 5α, 6α-epoxy-sito- and campesterol, 5β, 6β-epoxy-sito and campesterol, and dihydroxysitosterol and dihydroxycampesterol. A study investigating the contents of sterol oxidation products of cold pressed oils and refined oils from Polish markets showed that the content of oxyphytosterols in refined oils was 2–2.5 times higher than in cold pressed oil. Epimers of 7-hydroxy-phytosterols and 7-keto-phytosterols were the dominant compounds in cold pressed oil, while epoxy derivatives were dominant compounds in refined oil (Rudsinzka, Kazus, & Wasquwicz, 2001).

Vegetable oils, oilseeds, and nuts are the richest sources of phytosterols. Beta-sitosterol (29 carbons), campesterol (28 carbons), and stigmasterol (29 carbons) are the three most common sterols (Manai-Djebali & Queslati, 2017; Moreau et al., 2018; Shahzad et al., 2017). The total phytosterol content and profile can vary according to variety, agronomic and climatic conditions, maturity, extraction and refining methods, and preextraction and storage conditions (Bozdogan Konuskan & Mungan, 2016; Fernandez-Cuesta, Leon, Velasco, & De La Rosa, 2013; Lukic, Lukic, Krapac, Sladonja, & Pilizota, 2013; Manai-Djebali & Queslati, 2017; Temime et al., 2008).

Several studies have demonstrated that phytosterols protect against many chronic ailments such as cardiovascular diseases (Ros, 2010; Shahzad et al., 2017), cancer (Jones & AbuMweis, 2009; Rubis et al., 2010), ulcers (Plat et al., 2014), diabetes (Misawa et al., 2012), and inflammation (Grattan, 2013; Gylling & Simonen, 2015). Phytosterols have the capacity to reduce dietary cholesterol absorption in the intestine and serum low-density lipoprotein-cholesterol concentrations. Some research has shown that the consumption of 2 g/day of sterol or stanols may reduce the risk of heart disease by 25% (Hicks & Moreau, 2001; Shahzad et al., 2017; Wasowicz, 2003).

Phytosterols have been reported to have a protective effect against various forms of cancer such as breast (Grattan, 2013), prostate (Awad, Fink, Williams, & Kim, 2001), lung (Manai-Djebali & Queslati, 2017), liver and stomach (Ramprasath & Awad, 2015), and ovary and colon cancers (Baskar, Ignacimuthu, Paulraj, & Al Numair, 2010). In vivo studies have shown that diets enriched with phytosterols (2%, w/w) contributed to improve lipid profiles and decreased atherosclerotic lesions in apolipoprotein E-knockout (apo E-KO) mice (Manai-Djebali & Queslati, 2017; Moghadasian, 2006). Raicht, Cohen, Fazzini, Sarwal, and Takashi (1980) reported that the development of methyl nitrosourea induced tumors in mice when fed with 0.2% β-sitosterol in their diet for 28 weeks. The results showed a 39% reduction in overall tumor numbers and a 60% reduction in tumors per rat.

The phytosterol composition is a very useful parameter for detecting adulterations or to check authenticity since vegetable oils have a specific sterol profile known as a fingerprint (Piravi-Vanak, Ghasemi, Ghavami, Ezzatpanah, & Zolfonoun, 2012; Yorulmaz & Bozdogan Konuskan, 2016). Standardized methods for total phytosterol analysis have been developed by the American Oil Chemists’ Society, the Association of Official Analytical Chemists, and the International Organization for Standardization (Moreau et al., 2018). Generally, the determination of phytosterols including extraction of lipid fraction followed by alkaline hydrolysis (saponification), extraction of unsaponifiable matter, derivatization of phytosterols, and separation/quantification are done by chromatography (Figueiredo et al., 2018). Saponification is practically a universal step prior to phytosterol analysis by gas chromatography (GC), and is included in most of the above references for total phytosterol analysis (Moreau et al., 2018). Thin-layer chromatography (TLC), solid-phase extractions (SPE), and high-performance liquid chromatography are the three main methods used to separate phytosterols classes and total sterols from unsaponifiables (Azadmard-Damirchi & Dutta, 2010). The qualitative and quantitative analysis of phytosterols in vegetable oils is analyzed by gas chromatography. Both flame ionization (FID) and MS (electron impact, or EI) detection are commonly used (Moreau et al., 2018).

3: Phospholipids

Phospholipids (PL), one of the minor lipid components in seed oils, are highly abundant structural and functional lipids found in cell membranes (Gao & Wu, 2019; Herchi et al., 2012). Major phospholipids are derivatives of glycerol, where the 1- and 2- positions are acylated by fatty acids while the 3-positions are esterified with phosphoric acid (Pokorny, 2003). Major PL are lecithin (phosphatidylcholine), cephalin (phosphatidylethanolamine, phosphatidylserine), phosphatidylinositol, sphingomyelin, and phosphatidic acid. Lecithin, cephalin, and phosphatidylinositol, which are the most common phosphatides, can be regarded as triglycerides in which one fatty acid root switches with phosphoric acid (Gunstone & Norris, 1983). The major functions of PL in foods are their surface-active properties, and they act as emulsifiers and stabilizers of emulsions. Phospholipids are completely removed from the oil during degumming or mucilage removal processes, since they cause productivity loss in the oil extraction as they have emulsifier properties (Gunstone & Norris, 1983; Kayahan, 2003). PL usually occur to the content of 1%–2% in freshly extracted soybean or corn oils. They are present in lesser amounts in other seed oils, for example, 0.7%–0.9% in crude cottonseed oil and 0.3%–0.4% in crude peanut oil (Bailey, 1951). PL increase the oxidative stability of fats and oils by acting as synergists with tocols and phenolics (Pokorny, 2003). Phospholipids have attracted remarkable interest because of their health benefits (Herchi et al., 2012). Recent research has shown that PL could be a good source of arachidonic acid, which is important in metabolism, especially in the synthesis of prostaglandins and leukotrienes (Gao & Wu, 2019).

4: Tocols (tocopherols and tocotrienols)

Tocopherols and tocotrienols, together abbreviated as tocols, are natural lipophilic antioxidants that protect oxidation in vegetable oils (Ozcan, Al-Juhaimib, Ahmed, Osman, & Gassem, 2019; Schwartz, Ollilainen, Piironen, & Lampi, 2008). Tocols (vitamin E) comprise a chromanol ring with a C16 phytol side chain and are reclassified in two types according to which the side chain is either saturated (tocopherols) or contains three double bonds at carbons 3, 7, and 11 (tocotrienols) (Lachman, Hejtmankova, Orsak, Popov, & Martinek, 2018). Both tocopherols and tocotrienols exist in four different isomers called alpha, beta, gamma and delta; these differ in the methylation pattern of the benzopyran ring with three methyl groups (at C-5, C-7, and C-8) (Boschin & Arnoldi, 2011). Among the tocopherols, alpha and gamma tocopherols are the most effective lipid-soluble antioxidants in vegetable oils. Alpha-tocopherol shows the highest vitamin E activity while gamma-tocopherol has the highest antioxidant activity (Böhmdorfer, Patel, Netscher, Gille, & Rosenau, 2011; Boschin & Arnoldi, 2011).

Vegetable oils contain not only alpha-tocopherol but also other tocopherols, especially gamma and delta-tocopherol (Saldeen & Saldeen, 2005). The soybean and corn oils are usually dominated by gamma-tocopherol, while in olive oil the more abundant form is alpha-tocopherol (Szymanska & Kruk, 2008). The tocols have quench singlet oxygen and free radicals scavenge, particularly lipid peroxy radicals of polyunsaturated fatty acids (PUFA), therefore terminating lipid peroxidation chain reactions (Azzi, 2019; Maeda & Dellapenna, 2007). Tocols also play an important role as an antioxidant in oil stability. Due to their potent antioxidant properties and biological effects at the molecular level, they have reduced the risk of many diseases such as cardiovascular diseases, antiinflammatory and antidiabetic effects, osteoporosis, hyperlipidemia, neurodegenerative diseases, and cancer (Bartosinska, Buszewska-Forajta, & Siluk, 2016; Saldeen & Saldeen, 2005; Schwartz et al., 2008; Zhang et al., 2019). Vitamin E is also indispensable for immune defense. It has been suggested that tocopherols, acting as hormones or as secondary donors of genetic information, control the expression of some genes (Nogala Kalucka, 2003).

Vitamin E deficiency causes the damage of cellular membranes resulting from oxidation of the unsaturated fatty acids in lipids, and vitamin E deficiency can also display itself as muscular pain and progressing muscular disorder (Nogala Kalucka, 2003). The tocols in oilseeds could be determined by analytical techniques such as GC, liquid chromatography with diode array detection, thin-layer chromatography equipped with evaporative light scattering detection, and liquid chromatography-mass spectrometry (Zhang et al., 2019). For tocopherols, the richest dietary sources are vegetable oils and the products made from these oils. The tocopherol contents in seed oils range from 2 to 8 mg/100 g of coconut oil to 113 to 183 mg/100 g of corn oil (Nogala Kalucka, 2003). The amounts of tocopherols in vegetable oils vary according to variety, extraction method, and refining (Flakelar, Luckett, Howitt, Doran, & Prenzler, 2015).

5: Phenolic compounds

Phenolic compounds (PC), the most abundant secondary metabolites in plants, are compounds containing phenol function (Xu, Wang, Pu, Tao, & Zhang, 2017). The simplest phenolic compound is benzene, which contains one hydroxyl group (Cemeroğlu, Yemenicioğlu, & Özkan, 2001). PC have a common chemical structure comprising an aromatic ring with one or more hydroxyl groups that can be divided into several classes. These are flavonoids, phenolic acids, tannins, stilbenes, and lignans (Xu et al., 2017). PC are important in terms of their health functions, effects on taste, odor, pigment formation, antioxidant and antimicrobial effect, enzyme inhibition, and control criteria in different foods (Acar & Gokmen, 2016; Xu et al., 2017). Many studies have demonstrated that PC have various effects such as antioxidant, antimicrobial, anticarcinogenic, antiinflammatory, and estrogen-related prevention of cardiovascular diseases, cancers, diabetes, and diseases associated with oxidative stress (Lin et al., 2016; Louis, Thandapilly, & Kalt, 2014; Siger, Nogala Kalıcka, & Lampart Szczapa, 2008; Xu et al., 2017; Zhang, Lin, & Li, 2016).

A phenolic compound can interrupt the radical chain reaction by donating a hydrogen atom to the free radicals and therefore converting itself to a radical. Phenolics can also act as metal chelators and oxygen scavenger. Phenolics are removed to a certain portion during the refining process, thus PC are found in higher amounts in cold pressed oil than in refined oil (Grosshagauer et al., 2019). Natural olive oil is known to be the most stable oil because of its high amount of PC (Siger et al., 2008).

It has been stated that the most important PC derivatives are in the rapeseed oil including 2,6 dimethoxy-4-vinylphenol (257 μg/100 g) and ferulic acid (5.6 μg/100 g), while vanillic acid (11.4 μg/100 g) is in pumpkin seed oil and ferulic acid (5.8 μg/100 g) is in corn oil. The total amount of PC was determined as 79 mg gallic acid/kg oil in soy oil, 124 mg gallic acid/kg oil in canola oil, 8397 mg gallic acid/100 g oil in palm fruit, and 20–43 mg synapic acid/100 g oil in rapeseed oil (Yemiscioğlu, Özdikicierler, & Gümüskesen, 2016). PC content and profile in plant oil generally depends on the variety, environmental conditions, extraction methods, and storage conditions (Boskou, 1996).

6: Squalene

Squalene, a molecular formula of C30H50, is formed by the combination of six isoprene radicals to form symmetry at the midpoint of the squalene molecule (Kayahan, 2016). Squalene is a triterpene hydrocarbon, often found in nature, and acts as a precursor to cholesterol and other sterols (Lu, Jiang, & Chen, 2004). It forms the majority of hydrocarbons in the unsaponified fraction of olive oil (Minguez-Mosquera, Rejano-Navarro, Gandul-Rojas, Sanchez-Gomez, & Garrido-Fernandez, 1991). Olive oil contains 0.2%–07% squalene, while other oils contain 0.02%–0.03% (Bayram & Özçelik, 2012). Squalene is usually stored under the skin after ingestion and is therefore used as a moisturizer and emollient in cosmetics. It also has protective cell properties against free radicals as a potential oxidation inhibitor (Bozdogan & Altan, 2008). Squalene has been reported to inhibit the activity of beta-hydroxy-beta-methylglutaryl-CoA (HMG-CoA) reductase, which plays a key role in cholesterol synthesis. Thus, the cell membrane is displaced, and the risk of larynx, colon, and pancreatic cancers is reduced (Bayaz & Mehenktaş, 2004). According to one study, consuming a certain amount of olive oil every day reduces the risk of breast cancer in women by 25% (Trichopoulou, Katsouyanni, & Stuver, 1995). In a study investigating the effects of squalene on skin, colon, and lung cancer in mice, it was reported that squalene, when consumed daily, has antitumor, antibacterial, and anticarcinogenic effects. Researchers have reported that squalene also plays an important role in eye health, especially for rod photoreceptor cells of the retina (Asman & Wahrburg, 2007).

7: Pigments

The content of pigments in cold pressed oils is higher than in refined oils (Aachary, Liang, Hydamaka, Eskin, & Thiyam-Hollander, 2016). The major pigments in cold pressed oils are carotenoids and chlorophyll (Kayahan, 2003).

7.1: Carotenoids

The characteristic yellow-red color of most vegetable oils is due to the presence of various carotenoid pigments (Bailey, 1951). Carotenoids are isoprenoid components comprising of two C20 (geranylgeranyl diphosphate) molecules’ coming together and usually containing 40 carbon (C40) atoms (Bailey, 1951; Minguez-Mosquera, Hornero-Méndez, & Pérez-Gálvez, 2002). Carotenoids are lipophilic compounds that exist in acyclic, monocyclic, and bicyclic forms (Bailey, 1951; Minguez-Mosquera et al., 2002). Carbon atoms in the carbon chain forming the molecular skeleton of carotenoids are connected with alternately single or dual conjugated dual bonds (Altan & Kola, 2009). In general, carotenoids can be defined as terpenic alcohols, hydrocarbons, and organic acids. While a large part of carotenoids is present in the structure of the hydrocarbons, the rest exists in the structure of the alcohol (Kayahan, 2003).

The most prominent feature of hydrocarbon carotenoids is that no oxygen is included in their form. In these carotenoids, the most notable one is carotene (C40H56) (Kayahan, 2003; Rodriguez Amaya, 1997). There are three isomers of carotene in nature: α, β, and γ. α and β-carotenes are usually together in nature. All three carotenes are physiologically provitamins of vitamin A (Divya, Puthusseri, & Neelwarne, 2012). Another carotenoid in the structure of hydrocarbon is lycopene, giving the tomato its red color (Kayahan, 2003; Minguez-Mosquera et al., 2002). Major carotenoid alcohols are lutein (xanthophylls), cryptoxanthin, and rubicxanthin. Lutein is a dioxi derivative of α-carotene showing optical activity (Kayahan, 2003; Rodriguez Amaya, 1997).

Colors of carotenoids are the reason for the polienic conjugated bonds named chromophore structure (Kayahan, 2003). Carotenoids must include at least seven conjugated double bonds to have a noticeable light yellow color. Because of this, poliens including less conjugated double bonds are not technically regarded as carotenoids (Altan & Kola, 2009).

Carotenoids, which are natural color substances, usually give the foods in which they are present yellow, red, and orange colors. Of these, α-carotene, β-carotene, lutein, and zeaxanthin give a yellow color, lutein gives a green color with yellow, and lycopene gives a red color (Zeb & Mehmood, 2004). It is known that the oil with the highest carotenoid content is crude palm oil (500–700 mg/kg oil). Carotenoid content of the other crude vegetable oils is below 100 mg/kg oil (Yemiscioğlu et al., 2016).

Some important characteristics of carotenoids include absorbing light, being isomerized and oxidized easily, being able to connect hydrophobic surfaces, and being a singlet oxygen quencher (Rodriguez Amaya, 1997). Carotenoids in oils play an important role in the stability of the oil as a singlet oxygen quencher in addition to their coloring properties (Cert, Moreda, & Pérez-Camino, 2000; Psomiadou & Tsimidou, 2002). Carotenoids, together with PC and tocols, are involved in the oxidative stability of oils and have synergist antioxidant effects (Luaces, Perez, Garcia, & Sanz, 2005; Mba, Dumont, & Ngadi, 2018). Carotenoids play a major role in human nutrition and health due to the fact that they take part in provitamin A and display anticancer properties. Studies have shown that antioxidant carotenoids have protective effects against skin disorders, eye disorders, cancer, and cardiovascular diseases (Campestrini et al., 2019; Rodriguez Concepcion et al., 2018).

7.2: Chlorophyll

Chlorophyll is in porifyrin structure since it is classified into porifyrin group compounds. Porifyrin consists of four pyrrole units connected by methyin bridges. The most important feature of porifyrins is that they tend to chelate with metal ions. The color of porifyrins depends on the compounds in the ring structure and the structure of the central atom. Magnesium is the central atom that chelates metal in chlorophyll (Minguez-Mosquera et al., 2002). Chlorophyll pigment, containing one atom of magnesium at the center of the molecule, consists of chlorophyll a and chlorophyll b (Cemeroğlu et al., 2001; Psomiadou & Tsimidou, 2001). The structural difference between two chlorophylls stems from the fact that chlorophyll a contains one more oxygen atom and two fewer hydrogen atoms than chlorophyll b (Kayahan, 2003). The green color of all plant tissues originates from chlorophyll pigment (Minguez-Mosquera et al., 2002). Some oils, such as early harvest olive oil, frost-exposed seed oils, rapeseed, and soybean oil, have a green color from chlorophyll and similar compounds (Kayahan, 2003). Since chlorophyll is temperature-sensitive, it loses its magnesium during heat treatment, which breaks into pheophytin and turns brown-yellow (Kayahan, 2003). With the stimulating effect of oxygen, heat, light, and enzymes, the chlorophyll molecule is easily broken down (Del Giovine & Fabietti, 2005). The breakdown of chlorophylls is much faster than that of carotenoids (Boskou, 1996).

Chlorophyll a and b (1–10 ppm) are responsible for the greenish color of olive oil, and chlorophyll breakdown products a and b (0.2–24 ppm) are responsible for the brown color of the oil (Boskou, 1996; Kayahan, 2003). Among chlorophyll, the one having the highest amount is pheophytin (70%–80%), which is found in olive oil and other vegetable oils (Boskou, 1996; Minguez-Mosquera et al., 1991). Chlorophyll and pheophytin act as pro-oxidants in the photooxidation of oils (Aparicio, Roda, Albi, & Gutierrez, 1999; Tan, Chong, & Low, 1997). Chlorophyll transforms into pheophytin using O2 in a light environment. It shows antioxidant activity together with phenolic antioxidants in the dark and plays an important role in the stability of olive oil (Psomiadou & Tsimidou, 2001; Velasco & Dobarganes, 2002).

The amount of carotenoid and chlorophyll in the vegetable oils depends on variety, maturity, environmental factors, extraction systems, and storage conditions (Minguez-Mosquera et al., 1991; Sibbett, Connell, Luh, & Ferguson, 1994).

8: Aroma and flavor compounds

Cold pressed oils have a characteristic taste, smell, and flavor (Mounts, 1985). Flavor is tightly correlated with the qualitative and quantitative composition of volatile components in oil (Dun et al., 2019). Taste and odor substances in oils can be examined in two groups, as natural taste and odor substances as well as taste and odor substances formed as a result of technological processes or oxidative degradation. The natural taste and odor substances are hydrocarbons and have a polyethylene structure. As a result of technological processes or oxidative deterioration, taste and odor substances such as aldehyde, ketone, and alcohol are formed in the structure of the oils (Sidar, 2011). Tridecadien, pentadecen, hexadecadien, nonadecen, triacosahexen, and octacosatrien were determined in fresh olive oil and peanut oil (Kayahan, 2003). It is also stated that the characteristic smell of palm kernel oil originates from methyl-nonyl and other ketones. In addition, oils can absorb any foreign taste and odor easily (Kayahan, 2003). The flavor of oils depends on the variety, ripeness degree, environmental condition, growing region, storage, and extraction methods. Many studies have investigated the volatile compounds attributed to plant edible oils. Hexanol, trans-2-butenal, and acetic acid were the main volatile compounds in linseed oil, while trans-2-butenal and acetic acid, accompanied by trans, trans-3,5-octadiene-2-one and trans, trans-2,4-heptadienal dominated the flavor components of camelina oil (Dun et al., 2019).

Wei et al. (2012) compared the volatile components in rapeseed oils obtained by cold pressing without any treatment, cold pressing with thermal treatment, and microwave radiation. The contents of the degradation products of glucosinolates obtained by cold pressing with thermal treatment and microwave radiation decreased, while the contents of oxidized volatiles and heterocyclic compounds increased. Can-Cauich, Sauri-Duch, Moo-Huchin, Betancur-Ancona, and Cuevas-Glory (2019) reported that the total phenolic compounds, total carotenoids, and squalene of pumpkin oils obtained by mechanical pressing were higher than those obtained by solvent extraction.

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Chapter 3: Valorization of by-products from the production of pressed edible oils to produce biopolymer films

Senka Popović; Nevena Hromiš; Danijela Šuput; Sandra Bulut; Ranko Romanić; Vera Lazić    Faculty of Technology Novi Sad, University of Novi Sad, Novi Sad, Serbia

Abstract

After oil production from oilseeds, valuable by-products (cake/meal) remain, which could be valorized as a raw material for animal feed, biofuel production, and extraction of valuable components (proteins, polysaccharides, phenols, etc.). Considering the composition of oil industry by-products, regarding the high content of proteins and polysaccharides, these materials present a promising substrate for eco-friendly biopolymer packaging materials production. Biopolymer films production from almost all oil industry by-products, cakes, meals, protein isolates, and concentrates has been investigated. In addition to globally present oilseeds (soybean, sunflower, and rapeseed), there are locally used oilseeds, like pumpkin seed, peanut, sesame, and others, whose by-products have been evaluated as raw materials for green packaging material production. In this chapter, different oil industry by-products utilized (as well as products derived from them) for packaging materials production will be reviewed. Recent trends in production, characterization, and potential applications of biopolymer materials obtained from oil industry by-products will be displayed.

Keywords

Oil industry; By-products; Valorization; Green packaging materials

1: Introduction

One of the most important challenges for agriculture and food industry in the present and the upcoming future is to feed the growing world population (FAO, 2018). The production of a huge amount of agricultural products and their usage for food production lead to significant amount of residues, called agro-waste. A certain amount of agro-waste is considered as by-products, but even these by-products are currently underutilized. Trends and potential solutions are mainly aimed at the production of biofuel and animal feed, as well as extraction of valuable components (i.e., proteins, polysaccharides, phenols, etc.). In this context, production of biodegradable natural polymers—biopolymers—can make a significant contribution to recovery and utilization of obtained wastes and/or by-products (Popović, Lazić, Hromiš, Šuput, & Bulut, 2018). Oilseeds and oilseed products play an important role in providing a nutritionally balanced diet. After production of oil from oilseeds, valuable by-product, cake, or meal remains. Considering their composition (high content of proteins and polysaccharides), these materials present promising substrates for eco-friendly biopolymer packaging materials.

2: By-products of oilseeds processing

Depending on modern concepts of sustainable development and environmental protection, industrial production as the ultimate goal has the maximum utilization of all resources and practical production without any waste. Sustainable development concerns the safe present and leads to a secure future since, at the same time, the needs for raw materials and energy sources have been reduced.

The oilseed industry creates significant quantities of by-products that are currently underused. Depending on the type and quality of oilseeds, the oil extraction process, and the quality of the obtained by-products, their application could be not only for animal feed but also for a wide range of food products. Most research on the subject showed that in addition to an adequate hygienic approach of complete technological processing and health safety, the by-products of a particular process can have favorable functional characteristics and are suitable for human consumption. Of particular importance is the use of various oilseed cakes obtained in the processing of pressing; therefore, without the use of organic solvents, oilseed cake maintains the favorable nutritional properties of the starting material.

3: Oilseeds processing technology

Usage of by-products deriving from the processing of seeds and oilseed has become a necessity in terms of creating new products instead of creating waste products. The use of by-products has become an integral part of the usual production process, by increasing the efficiency of processing and using energy. A scheme of the technological process of production of edible oils, followed by cakes and meals, as by-products, is shown in Fig. 1.

Fig. 1 Technological scheme of production of nonrefined and refined edible oils, cakes, and meals.

Edible oils can be produced as nonrefined (cold pressed and virgin) or as refined edible oils. In the production of edible nonrefined oils, cake is obtained as a by-product. From the cake after the production of crude oils, the remaining oil is extracted by solvent extraction and remains as a secondary product. Crude pressed oil, crude extracted oil, or a mixture is passed through a whole series of steps of the chemical or physical refining process, to obtain edible refined oil (Dimić, 2005; Romanić, 2015; Shim, Gui, Wang, & Reaney, 2015).

4: Cakes composition and characteristics of some oilseeds

The cake is a by-product (Fig. 2) that remains after the extraction of oil from oilseeds by the process of pressing, primarily in the production of edible nonrefined or cold pressed oils. Cakes can be edible or inedible. Some edible oilseed cakes have a high nutritional value. Their composition and nutritional value depend on the type, the conditions of growing the raw material, and oilseeds processing route (Dimić, Romanić, Peričin, & Panić, 2006; Peričin, Radulović, Mađarev, & Dimić, 2007).

Fig. 2 Cakes of sunflower seeds obtained from the production of cold pressed oil.

Cakes and flour, obtained after the oil extraction from oilseeds by