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Review Article

Recent Res. Devel. Lipids, 9 (2013): 139-201 ISBN: 978-81-7895-575-9

9. Phospholipids in cereals, nuts and some selected oilseeds

Federica Pasini1*, Ylenia Riciputi2*, Vito Verardo2 and Maria Fiorenza Caboni1,2

1Department of Agricultural and Food Sciences, University of Bologna. P.zza Goidanich 60, 47521 Cesena (FC), Italy; 2Inter-Departmental Centre for Agri-Food Industrial Research (CIRI Agroalimentare), University of Bologna. P.zza Goidanich 60, 47521, Cesena (FC), Italy

Abbreviations NL: Neutral lipids ST: Sterol TAG: Triacylglycerol FFA: Free fatty acid FA: Fatty acid FAME: Fatty acid methyl ester POL: Polar lipids PL: Phospholipid LPL: Lyso-phospholipid PC: Phosphatidylcholine PE: Phosphatidylethanolamine PI: Phosphatidylinositol PG: Phosphatidylglycerol PS: Phosphatidylserine PA: Phosphatidic acid

*These authors contributed equally to this work. Correspondence/Reprint request: Dr. Vito Verardo, Inter-Departmental Centre for Agri-Food Industrial Research (CIRI Agroalimentare), University of Bologna. P.zza Goidanich 60, 47521, Cesena (FC), Italy E-mail: [email protected]

Federica Pasini et al. 140

DPG (or CL): Diphosphatidylglycerol (or Cardiolipin) MPG: monophosphatidylglycerol LPC: Lyso-phosphatidylcholine LPI: Lyso-phosphatidylinositol LPE: Lyso-phosphatidylethanolamine LPG: Lyso-phosphatidylglycerol NAPE (or N-acyl PE): N-acyl Phosphatidylethanolamine NALPE (or N-acyl LPE): N-acyl Lysophosphatidylethanolamine NAGPE (or N-acyl GPE): N-acyl Glycerylphosphorylethanolamine SFA: saturated fatty acid MUFA: monounsaturated fatty acid PUFA: polyunsaturated fatty acid UFA: unsaturated fatty acid Introduction The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in nonpolar organic solvents and general insolubility in water. There is great structural variety among the lipids, as will be demonstrated in the following figure 1. Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Like triacylglycerols, the backbone of phosphoglycerides is glycerol (a three-carbon alcohol), but only the primary and secondary alcohol residues of glycerol are esterified to fatty acids (long-chain carboxylic acids).

LIPIDS

Unsaponifiable lipids

Saponifiable lipids

Terpenes Steroids Prostaglandins

Simple lipids Complex lipids

Waxes Triglycerides

Glycerol esters Sphingosine esters

Plasmalogens CerebrosidesPhosphoglycerides Sphingomyelins

PHOSPHOLIPIDS GLYCOLIPIDS

LIPIDS

Unsaponifiable lipids

Saponifiable lipids

Terpenes Steroids Prostaglandins

Simple lipids Complex lipids

Waxes Triglycerides

Glycerol esters Sphingosine esters

Plasmalogens CerebrosidesPhosphoglycerides Sphingomyelins

PHOSPHOLIPIDS GLYCOLIPIDS

Figure 1. Lipid classification.

Phospholipids in cereals and nuts

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The third site is esterified to a phosphate group, which in turn is linked to choline, ethanolamine, serine, inositol, or glycerol. Sphingomyelin, on the other hand, contains as its back-bone, the long-chain base, sphingosine (trans-D-erythro-1,3-dihydroxy-2-amino-4-octadecene), an 18-carbon moiety [1]. The main positive functions of phospholipids in foods are their surface-active properties. They act as emulsifiers and stabilizers of emulsions, facilitate the dispersion of solid particles in the water phase, and improve the

texture of multiphase food materials. Phospholipids make the texture smooth and improve the pleasantness by increasing the viscosity. Moreover, Phospholipids increase the oxidative stability of fats and oils and fatty foods, in that they act as synergists of tocopherols and other natural phenolic antioxidants, such as flavonoids. They stabilize even polyunsaturated edible oils and fish oils. Phosphatidylcholine reacts with peroxy radicals to yield trimethylammonium oxides. Phosphatidylamines react with lipid hydroperoxides in the non-radical way to form imines. Phospholipids can also bind heavy metals, which act as prooxidants, to produce inactive, undissociated salts [2]. Beneficial effects of dietary phospholipids (PLs) have been mentioned since the early 1900’s in relation to different illnesses and symptoms, e.g. coronary heart disease, inflammation or cancer [3,4,5]. From the majority of the studies it became evident that dietary PLs have a positive impact in several diseases, apparently without severe side effects. Furthermore, they were shown to reduce side effects of some drugs. Both effects can partially be explained by the fact that PLs are highly effective in delivering their fatty acid (FA) residues for incorporation into the membranes of cells involved in different diseases, e.g. immune or cancer cells. The altered membrane composition is assumed to have effects on the activity of membrane proteins (e.g. receptors) by affecting the microstructure of membranes and, therefore, the characteristics of the cellular membrane, e.g. of lipid rafts, or by influencing the biosynthesis of FA derived lipid second messengers. However, since the FAs originally bound to the applied PLs are increased in the cellular membrane after their consumption or supplementation, the FA composition of the PLs and thus the type of PL is crucial for its effect [6]. The importance of PLs is also related to their many industrial applications principally based on their surfactant properties; in particular, in the food industry, when combined with proteins, PL are used as emulsifiers or emulsion stabilizers. In addition to their biological and technological role, PL are used for several biomedical applications, such as emulsification in pharmaceuticals and the preparation of liposomes for cosmetics and drug delivery [7].


There are several analytical methods available for analysis of phospholipids. TLC, capillary electrophoresis and high performance liquid chromatography (HPLC) can be used to analyze the different class of phospholipids. In this chapter we will discuss the isolation and PL composition of different cereals, nuts and some selected seeds. Phospholipids in food Cereals and Pseudocereals Interest in food functional lipids with nutritional and technological impacts has been growing in the last years. Nutritional effect is manly related to the fatty acid composition of neutral lipids (triglycerides), and to the principal species of unsaponifiable matter (e.g. sterols, and tocochromanols) and polar lipids (phospholipids and glycolipids) which are also responsible for the technological behaviour of fats and fatty food during processing. Among vegetable foods, cereals are monocotyledonous plants that belong to the grass family. The cereal grains such as wheat, rice, corn, barley, oat, rye, sorghum, and millet provide 50% of the food energy and 50% of the protein consumed on earth. Wheat, rice, and corn together make up three-fourths of the world’s grain production. In general, cereal grains have been considered as the main source of carbohydrates to supply food energy to the diet. The cereal crops that are grown for their edible fruit are generally called grain, but botanically referred to as caryopsis. The cereal seed consists of two major components, the endosperm and embryo or germ [8]. The grain is surrounded by a five-layer coat called bran, which makes up 15% of the mass of the whole grain. It is rich in B vitamins and contains about 50% of the total mass of minerals in the grain. The bran consists of cellulose and is indigestible for humans. The germ, about 3% of the mass of the grain, contains the embryo, which is rich in lipids, proteins, B vitamins, vitamin E, and minerals. A membranous tissue called scutellum separates the germ from the endosperm and it is a rich source of thiamine. The starchy endosperm makes up 80 to 90% of the grain and is a reserve of food for the germ. The starch granules are embedded in a protein matrix, while the periphery of the endosperm is composed of a single aleurone layer which is rich in proteins and contains high amounts of minerals, vitamins, and enzymes, but it is usually removed during milling [9]. Cereal grains are an important source of functional lipids. Although the kernel is mainly composed of starch and contains much smaller amounts of lipids compared to oilseeds, cereals increase the content of essential fatty acids (manly linoleic acid C18:2) and glyco- and phospholipids, which also


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improve the quality of cereal products, in human diet. Interest in cereal lipids is also driven by the presence of specific compounds, which are usually absent in mainstream oils, particularly natural antioxidants such as tocotrienols, and other bioactive compounds specific to the cereal grain [10]. The major cereals grown worldwide are common wheat, rye, barley, oat, rice, corn, sorghum and millet. In these crops, lipids are below 10% (except oat which contains about twice the amount present in other cereals) and are mainly located in the germ, bran and/or caryopses endosperm, depending on the cereal [11]. The distribution of lipid components within kernel is not uniform and different classes of lipid compounds are present in different parts of the seed where they play their physiological and protection roles. Knowledge of the distribution of lipids in cereal kernel is important from a technological point of view. The composition of lipid classes is unique to specific cereal grains [10]. Lipid can be associated with the starch as surface lipids, which exist on the surface of starch granules and resembles the rest of the kernel lipids, and internal lipids which consist mainly of monoacyl lipids (lysophospholipids) and free fatty acids that form inclusion complexes with amylose [12]. Nonstarch lipids consist of two types: free (acylglycerols and free fatty acids), extracted with non polar solvents, and bound (glycolipids and phospholipids) usually extracted with polar solvents [10]. Phospholipids represent the most important polar lipid class present in food materials and usually ranges from 1 to 2 wt % of dry matter [2]. Different studies were performed on cereal phospholipid fraction during the last forty years but information on PL composition are difficult to compare since different analytical methods are employed and the ratio of PLs to LPLs is influenced by enzymatic activity. Most of the authors cited below used a mixture of chloroform and methanol, modifying Folch [13] and Bligh and Dyer [14] methods, for the extraction of free lipids and hot water saturated butanol to extract phospholipids bound to amylose in starch granules. Separation of polar from non polar lipid by silicic acid column chromatography or solid phase extraction (SPE) [15] and then isolation of different species of phospholipids by thin layer chromatography (TLC) with different elution system have been employed in cereal lipid analysis by the same authors. Gas chromatographic analysis has been carried out to characterize fatty acid composition of each species. In the last years, moreover, HPLC coupled with mass spectrometer (MS) and light scattering detector (ELSD) has been used to analyze phospholipids in cereal and cereal products (Table 1) [16].


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Wheat (Triticum aestivum L.) In wheat kernel, lipids constitute 2.5-3.3% of kernel weight, depending on cultivar and agronomic conditions; 30-36% are located in the germ, 25-29% in the aleurone layer and 35-45% in the endosperm. The germ and aleurone lipids are predominantly non polar (72-85%) with small amounts of polar lipids (13-23%) and are distinctly different from the endosperm lipids that are especially rich in phospholipids and glycolipids mainly bounded in starch granules [17]. Among polar lipid compounds, phospholipids represent the most important class due to the important effects on the final texture of wheat based products, since they interact primarily with the wheat gluten protein network that is the backbone of wheat-flour-dough mixing properties and gas retention [18]. Hot water saturated n-BuOH was the most efficient extracting solvent for wheat grain bound lipids to starch granules and extraction with iso-PrOH and CHCl3 was greatly inferior. The use of cold water saturated n-BuOH, however, give rise to artefacts due to phospholipase D and transphosphatidylase activity during extraction. To confirm this, Colborne and co-worker [19] separated 11 phospholipids (N-acyl PE, N-acyl LPE, N-acyl GPE, DPG, PG, PE, PA, PC, LPC, LPE, PI) from whole wheat, dissected bran and endosperm by two-dimensional TLC. Phosphorous quantization results from different replicate experiments indicated that in the bran, PC (max. 34.1% of total P), PI (max. 11.7% of total P) and LPC (max. 30.4% of total P) were the most abundant species. However, consistent changes occurred during replicate extraction, leading to elevated levels of N-acyl PE (NAPE) at the expense of other phospholipids like PC and PE. These changes could be assigned to phospholipase D activity. In contrast to the bran, the starchy endosperm had negligible phospholipase D activity and the mean content of the main PL found was 65.4% and 8.7% and 8.4% of total P for LPC, LPE and NAPE, respectively [19]. These phospholipase D artefacts could be partially avoided by denaturing the tissue by heat before extraction. Also in whole grains of tetraploid (Triticum dicoccon S. and Triticum durum D.) and hexaploid wheats (Triticum spelta L. and Triticum aestivum L.) PC and PI were the major PLs determined, and with PE, accounted for 73-95% of total PLs. In particular, Pelillo et al. found that the main differences were in the content of PE and PI among wheat species. Moreover, the amount in naked wheats was about 17% higher than that determined on average in hulled wheats: 10.2±2.8 vs. 8.7±2.2 g/100 g of lipids, respectively (Table 2) [20].


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Table 2. Lipid content, organic phosphorus (P), phospholipid (PL) content in different wheat samples.

Adapted from: Pelillo M., Ferioli F., Iafelice G., Marconi E. and Caboni M.F. 2010. Journal of Cereal Science, 51:120-126 Minasbekyan et al. [21] studied the content of phospholipids in chromatin, soluble nuclear fraction and nuclear membrane from dry and germinated embryos of hexaploid wheat samples. They identify seven PL compounds (PC, PE, PI, PS, PA, cardiolipin and LPC) but only PC and PE were present in all nuclear fractions. PC was the major phospholipid in all three sub-fractions of nuclei isolated from dry embryos and the relative content of PC in the nuclear membrane was 28.9% (0.545 μg/mg dry wt), in soluble nuclear fraction 37% (0.407 μg/mg dry wt) and in chromatin 49% (0.710 μg/mg dry wt). Also the content of PE in soluble nuclear fraction was lower (0.179 μg/mg dry wt) than in the nuclear membrane corresponding to the results of other experiments that revealed the presence of choline:ethanolamine phosphotransferase CEPT-1 responsible for the synthesis of PC and PE in the nuclear membrane and endoplasmic reticulum [22]. The interesting finding was that nuclear membrane contains major cylindrical lipids, PC and PE, and a conical phospholipid PA (0.359 μg/mg dry wt) with unique properties. In effect, PA is supposed to be involved in the control of such important biological processes as protein phosphorylation, activation of oxidative processes and modulation of membrane transport [23]. Conversely, LPC was found only in chromatin (0.119 and 0.135 μg/mg dry wt for dried and germinated embryos, respectively). In membrane, germination caused a reduction of all PLs except PA which increased, leading to a major membrane surface charge and then permeability.


Morrison well reviewed the lipid starch composition of several cereals and reported the presence of lysophospholipids, mainly LPC (499-864 mg lipid/100g dry wt) but also LPE (79-104 mg lipid/100g dry wt), LPG (23-54 mg lipid/100g dry wt) and LPI (5-41 mg lipid/100g dry wt), as the most important PL compounds in wheat starch. In particular, Durum wheat showed a higher amount (108 mg/100g dry wt) of LPLs in total starch compared to bread wheat (84 mg/100g dry wt) [24]. The presence of LPC on starch granules was confirmed also by Jimeno and co-workers [25] which isolated and analyzed LPC, by NMR, from the surface of wheat starch granules. Linoleic (C18:2) and palmitic (C16:0) acids were always the major fatty acids in wheat starch LPLs, accounting for 54-70 wt% and 19-39 wt%, respectively [24]. Besides LPLs, also in PE, PC and PI linoleic and palmitic were the two most abundant fatty acids of free and bound lipid fraction of wheat endosperm, but in PC the content of palmitic acid (20.4-48.8 wt%) was higher than in PE and PI (22.8-31.2 wt% and 6.4-28.4 wt%, respectively) and it was the major fatty acid. Oleic acid was also present in all PLs in relatively higher amount compared to other minor fatty acids, especially in PC, as reported by Mckillican in a dated study [26]. Different studies on wheat were focused on flour PLs [27, 28, 29, 30, 31]. Phospholipids are minor components (0.5 % dry mass) of wheat flour and even if they are typical starch lipids, only the PLs of the non-starch fraction are involved in dough quality [32]. As concerning rheological impact, it was demonstrated that native flour phospholipids cooperate soy PC added to dough but had lower effect on the specific volume of the dough than other flour polar lipids like glycolipids [30]. Technological properties of PLs during mixing and fermentation might be due to their ability to modify the physico-chemical properties of a liquid film wrapping gas bubbles [33]. In soft red winter wheat flour the non-starch lipid fraction consisted of more than ten major lipid classes (triglycerides, sterols, free fatty acids, some glycolipids and phospholipids). Results, expressed as relative mass % reported PE (3.5%), PG (2%), PC (0.7%), LPC (2.3%), LPE (0.8%) and NAPE (1.8%) as non starch phospholipids found. However, only lyso forms, LPE (10.2%), LPC (77.6%), LPG (0.1%), and PC (1%) were found among starch phospholipids [27]. By HPLC-ELSD analysis of different flours from French pure wheat varieties, LPC resulted the main phospholipid (0.61-1.43 μmol/g dm, 29-48%) followed by PC (0.65-1.21 μmol/g dm, 26-37%), NAPE (0.12-0.37 μmol/g dm, 4-10.7%) and NALPE (0.13-0.30 μmol/g dm, 4.2-8.7%) [28].


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The total PL amount in free lipid fraction of waxy wheat wholemeal was ~20% higher than in waxy grain (0.60-0.69 vs 0.48-0.56 g/kg dry basis, respectively) [34]. Also PC content, analyzed by HPLC-ELSD by the same authors, was higher in waxy grain compared to non waxy kernels (1.83 vs 1.53-1.57 g/kg dry basis, respectively). Moreover, these PC contents resulted higher than free PL amounts because water saturated butanol (employed in total PC extraction) could extract free and bound lipids simultaneously. The same authors cited above [28] evaluated also the fatty acid composition of phospholipid fraction before and after SPE purification and TLC separation and they showed linoleic acid as the major fatty acid (1.8 μmol/g dm), followed by palmitic (0.5 μmol/g dm) and oleic (0.24 μmol/g dm) acids. According to ESI-MS/MS, acyl carbon and double bond configurations of 36:4 and 34:2 were most prevalent in wheat flour lipid fraction extracts of soft white spring and hard red winter cultivars; these acyl combinations were identified as C18:2/18:2 and C16:0/18:2. Moreover, different phospholipids had typical molecular species: PE predominantly comprised molecular species of 36:4, PC and PA 34:2 and 36:4, PI 34:2 and PS was unique because contained high proportion of very long fatty acids, with predominant molecular species of 42:2 and 44:3. Conversely, LPLs (LPC, LPE and LPG) contained mostly 16:0 and 18:2 species [31].

Rice (Oryza sativa L.)

Rice grains are mainly composed of starch and contain much smaller proportion of lipids. Although, these lipids may make a significant contribution to processing and nutritional properties [11]. Lipids in rice grain are concentrated mainly in germ (34-37%) and bran (19-26% bran dry weight) [35] that are obtained during the milling process used to produce white rice. The lipids in endosperm are present in different forms compared to those in the bran and germ and mainly form complex with amylose in starch granules as internal starch lipids. LPC and LPE accounted for about 50% of the starch lipid in non waxy rice (Table 3) [36]. Bran lipids consisted mainly of neutral lipids (88.1-89.2 wt%, mainly as TAGs, STs, FFAs), glycolipids (6.3-7 wt%) and phospholipids (4.5-4.9 wt%). Among phospholipids, PC (35.0-38.4 wt%), PE (27.2-29.0 wt%) and PI (21-23.3 wt%), which constitute more than 80% of total PLs, were the principal PLs in the rice bran but also other minor compounds (PA 7.2-9.6 wt%, PG 1.4-1.8 wt%, LPC 1.0-1.5 wt%, LPE 1.0-1.4 wt% and NAPE 0.7-0.8 wt%) were isolated in Indian varieties [37]. Glushenkova and co-workers [38] found PC, PI and PE as major phospholipids of rice bran from Uzbekistan samples, accounting for 32.5%,


Table 3. Starch and non-starch lipids in brown rice: Content in the whole and in the different parts of kernel.

Adapted from: Liu L., Waters D.L.E., Rose T.J., Bao J. and King G.J. 2013. Food Chemistry, 139:1133–1145 23.5% and 20.8% of total PLs respectively; also in this study, minor PL components found were LPC (6.8%), NALPE and NAPE (both 6.9%) and PS (2.6%). In addition to the PLs within cell membranes, it is believed that PLs also form a single layer membrane bounding the spherosomes or subcellular lipid bodies [39]. As each PLs may contain a different combination and distribution of fatty acid esters, distinct differences between PL fatty acids in rice varieties were reported. In general, rice bran contained palmitic (C16:0, 25.1-47.6%), oleic (C18:1, 28.3-46.6%) and linoleic (C18:2, 16.3-32.6%) as the principal fatty acids in all phospholipids [37]. Rice bran PLs of red and black rice cultivars contained more than 65% of fatty acids as oleic and linoleic acids and about 35% as essential fatty acids [40]. The unsaturated fatty acids predominantly occupy the sn-2 position (77.3-91.3 wt%) and saturated fatty acids primarily occupy sn-1 or sn-3 position (35.0-78.7 wt%). When comparing the major PLs, the relative wt percentage of linoleic acid was significantly higher in PE (41.8–42.8 wt%) than in PC (26.4–27.0 wt%), while oleic acid was significantly higher in PC (43.8–44.2 wt%) than in PE (34.5–36.2 wt%). On the other hand, palmitic acid was significantly higher in PI (45.7–45.8 wt%) than in PE (17.8–18.7 wt%) or PC (25.4–25.8 wt%) [40]. For the starch PLs in the endosperm, palmitic (48-63%) and linoleic (25-42%) acids were predominant, with minor contributions from oleic (~ 5%) ad myristic (~ 5%) acids [41]. It should be noticed that, as in other cereals, also in rice it is difficult to make meaningful comparisons of the values for PL composition and contents from different studies since there is no standardization in terms of tissue


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sample, storage, processing and degree of milling [42]. In particular, non-starch PL content appeared to be less variable between rice varieties than starch LPL content. Genetic differences between waxy and non-waxy varieties influence the level of starch LPLs in the grain [43, 44]. The non-waxy starches (12.2–28.6%, w/w, amylose) contained 0.9–1.3% (w/w) lipids comprising 29–45% fatty acids and 48–67% lysophospholipids, whereas the waxy starches (1.0–2.3% amylose) contained negligible amounts of lipids [44]. Starch lipids and LPLs in particular, were consistently found to be significantly higher (10 times) in non-waxy rice varieties than waxy varieties and the low content of starch LPLs in waxy rices could be attributed to the absence of amylose content. The lyso forms in rice endosperm may form inclusions complexes with amylose, affecting the physicochemical properties and digestibility of starch, and hence its cooking and heating quality [42]. Although non-starch PLs content is relatively uniform, japonica rice cultivars appeared to contain PLs with higher polyunsaturated fatty acid (PUFA) content than indica cultivars [45]. However, the growing environment was found to have a greater effect than genetic variation levels of rice LPLs such as LPC, LPE and LPG [46]. The PL composition of rice is also regulated and modified during post-harvesting treatment and grain storage. De-husking and milling can negatively affect PLs and grain quality [42]. Yoshida [47] and co-workers reported that significant differences in major PL distributions were observed between well milled rice (WMR) and half milled rice (HMR) when comparing the PL components among five cultivars. The content of PE was significantly lower in WMR (76.3-81.4 mg/20g bran, 25.0–27.3 wt%) than that in HMR (93.6-98.0 mg/20g bran, 37.2–38.9 wt%), whilst the amount of PC was significantly higher in WMR (129.0-134.8 mg/20g bran, 43.3–46.8 wt%) than that in HMR (80.1-85.3 mg/20g bran, 31.8–32.8 wt%), respectively. Conversely, the percentage of PI was very similar to each other between WMR (58.2-69.1 mg/20g bran, 20.2–23.2 wt%) and HMR (53.9-57.8 mg/20g bran, 21.4–22.3 wt%) among the five cultivars. Moreover, when comparing the FA composition in PLs, the percentage of linoleic (18:2n-6) acid was significantly higher in WMR than that in HMR, whilst the percentage of oleic (18:1) acid was significantly higher in HMR than that in WMR, respectively. Lam and Proctor [48] evaluated LPL components and relative contribution of phospholipids to lipid hydrolysis in commercially milled long grain rice during 50 days of storage and noted that LPC, LPE and LPI increased significantly during the first 3 days of storage but only LPC continued to


increase until the end of the study period. Thus PC, whose hydrolysis product is LPC, was the main component of phospholipid hydrolysis during storage. Since PC was the main phospholipid in rice bran lipids and also the main membrane component of rice bran spherosomes, this study suggests that rice bran spherosomes were decomposed during hydrolysis of rice bran lipids. Moreover, since lipases act only at the oil–water interface and since the phospholipids are more polar than their TAG counterparts, they are probably present at the interface as emulsifiers and thus more readily exposed to lipase hydrolysis. Barley (Hordeum vulgare L.) The amount of lipids in barley kernel is in the range of 1.8-4.7% [49] and the higher lipid content is located in the embryonic axis (19.6%, dry weight basis) compared to bran-endosperm (2.8%, dry weight basis) and hull (2.4%, dry weight basis) [50]. In northern America two-row and six-row (spring and winter) varieties the 71% of lipids content was neutral lipids, 9% glycolipids and 20% phospholipids [51]. Compared to other cereals, phospholipid composition of barley grain has been studied much less and the studies carried out on phospholipid characterization of barley kernels dating back to several years ago. The phospholipid content and composition of barley grains varies slightly among barley varieties [52] but change more between kernel sections. In a study of Price and Parsons [50], emerged that phospholipids are mainly located in bran-endosperm (23.1% of total lipids) and less in embryonic axis (17.8% of total lipid); only small amount (5.9% of total lipids) was detected in hull. In another work, Qian and co-workers [53] reported a lipid content of 8.1% in the bran fraction of hulles barley where the phospholipid fraction amounts for 1.25% of the total bran lipids. These authors quantified only four phospholipids: PC (0.63% of total lipids and 50.4% of the phospholipids), PI (0.37% of total lipids and 29.6% of PLs), PE (0.17% of total lipids and 13.6% of PLs) and PS (0.08% of total lipids and 6.4% of PLs). Parsons and Price [54] confirmed the presence of these PLs founding PC (44.3-44.4% of total lipid phosphorus) and LPC (36.8-37.3% of total lipid phosphorus) as the major compounds, comprising over 80% of this lipid class. However, also smaller amounts of PE (7.6-8.8%), PS (4.8-5.0%), DPG (1.5-1.7%), PI (1.1-1.3%), PG (0.2-0.8%) and traces of PA were also reported. Morrison and co-workers [43] examined the lipid and


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amylose contents of 39 barley starch samples and found a strong positive correlation between lysophospholipids and amylose overall. In another study, Kotel’nikova [55] reported the presence of NAPEs in different cereal (wheat, oat, barley) and cereal products. The NAPE content found was 0.19–0.25 mg/g dry wt and, in particular, in barley it was ~0.25 mg/g dry wt. Chapman and co-workers [56] showed that NAE concentration was higher in the seeds with the high content of lipids but for NAPEs, the situation turned out to be opposite: the seeds of barley that contained much higher amounts of NAPEs, are characterized by a low total content of lipids. On the other hand, the content of NAPEs in the seeds was correlated positively with the total content of phospholipids. In barley, the content of NAPEs was on the average about 10% of total phospholipids. The fatty acid composition of total PLs was characterized by linoleic as the main fatty acid, ranging from 44.9 to 51.9 mole% followed by palmitic acid (31.0-36.9 mole%) and oleic acid (10.6-15.8 mole%). Lesser amount of linolenic (1.7-3.9 mole%), oleic (0.7-1.5 mole%), myristic acid (0.8-1.4 mole%) [52] and docosanoic (C22:0, 3.4% of total FAs in PL) [53] acids were also reported. Parsons and Price [54] reported the % of each fatty acid for the different PL species founding that linoleic acid was the principal fatty acid in all PL fractions except PG and PA where palmitic acid was the main one. However, also in this study, no significantly differences where found between barley cultivar. Little variations in fatty acid composition of PL fractions from different studies may be related to barley plant adaptation to growth condition [55, 57]. In particular, it was demonstrated that incubation of barley aleurone layers with gibberellic acid lead to an increase in long-chain unsaturated fatty acid species (saturated/unsaturated fatty acids ratio were 0.78 and 0.52 for treatment without and with gibberellic acid, respectively) in PC. However, when gibberellic acid treated layers were exposed to heat shock, there was a decrease in the amount of long-chain unsaturated fatty acids and an increase in shorter-chain, relatively saturated species. Plants grown in high-temperature stress conditions appeared to compensate for heat by increasing the degree of fatty acid saturation in their membrane PLs in order to decrease the fluidity of the membrane [58].

Corn (Zea mays L.) Among the cereal grains only pearl millet and oat kernels have higher average oil contents than do commercial corn hybrids. The corn kernel contains 1.7-5.1 % of lipids (% of total dry weight) mainly concentrated in the germ [59]. The distribution of kernel lipids was as 76-83% in germ,


1-2% in pericarp, 1% in tip cap, 1-1 1% in starch, and 13-15% in aleurone plus the non starch fraction of the starchy endosperm. The starches had a little surface lipid (FFAs) and true (internal) starch lipid (FFAs, LPLs) in quantities roughly related to amylose content (amylomaize = ca. 73% amylose, 1.03 mg lipid/100 g dry wt; LG-11 = 23% amylose, 0.68 mg lipid/100 g dry wt; waxy maize = < 5% amylose, 0.17 mg lipid/100 g dry wt). Similarly to other cereals, FFAs and LPLs were regarded as normal components of corn starch (rather than degradation products) and may occur as amylose inclusion complexes [60]. The amount of germ in the kernel and oil in the germ are genetically controlled and vary widely [61]. Both dry- and wet-milling processes are used to separate the germ from the remainder of the seed. Dry-milling yields germs contained about 18% oil (moisture free basis) whereas wet milling corn germ contained 30-50% oil, composed mainly by TAGs (98%), PLs (1.5% of crude germ oil) and other minor compounds (FFAs and steryl-esters) [62]. Harrabi et al. and Tan and Morrison [59, 60] reported 4-8.7% of phospholipids in corn kernel lipids (% of total lipids). Compared to other vegetable oils, corn oil is relatively rich in phospholipids. Low oil varieties had significantly higher content of phospholipids as a possible consequence of a reduced triacylglyceride synthesis since PLs and TAGs were derived from the same phosphatidate precursor. In corn grain, PC, PI and PE were identified as the main PLs but PG, DPG, PA and NAPE were also found as minor compounds. According to Harrabi and co-workers [59], PC was found to be the most abundant class of phospholipid, accounting for 57–68% of total PLs, in agreement with the results of Weber [63] which reported that throughout the harvesting period, over 50% of the total phosphorous was found in PC. PI (14.5–19.8% of total PLs) and PE (10.3–13.9% of total PLs) lipids ranked second and third, respectively. PA (3.8-6.6% of total PLs) and PG (2.2-3.3% of total PLs) were the minor classes, accounting together for less than 10% of the total phospholipids. In the same study, the authors compared three corn varieties PLs and showed that there were significant differences in their phospholipid composition: the high oil variety showed a greatest content of PI and the lower oil variety showed the highest amount of PC. Thus, the quantitative and qualitative phospholipid class compositions could be used for the detection of oil adulteration. Weber [63] demonstrated also that the content of PL change, during time, after hand-pollination of a standard corn inbred. The total PL amount was found to be the highest at 30 days after pollination. However the total


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amount of PC, PE and PI was highest at 45 days after pollination. Expressed as % of total phosphorus, the fraction represented by PE fell from 24% to 8% from 10 to 75 days after pollination while the PI remained nearly constant at 10%. PG and PA were minor components at all stages. Besides, in LG-11 germ, PLs increased rapidly between 16 and 52-76 DAP (day after pollination) and then decreased slightly without accumulation of lysophospholipids. Changes in germ lipids up to 52-76 DAP appear to be normal and the late disappearance of storage and structural lipids (TAGs and PLs) without formation of degradation products, suggests that these lipids were required for respiration when energy from photosynthesis was no longer available [64]. In the corn kernel the PL distribution was different when considering germ, endosperm or pericarp. Comparison between three corn kernel parts demonstrated that there was a significant difference in their contents of various PL classes. PC was the most abundant class in germ and pericarp fractions (51.4–70.6% of the total PL), followed by PI (11.3–25.1%) and PE (8.4–12.6%). In contrast, PE was found to be the most abundant class in the endosperm fraction (41.4–48.5%), followed by PC (30.2– 33.4%) and PI (13.2–14.4%). Mean values of PA were significantly higher (8.1-10.8 % of total PLs) in the endosperm fraction of two varieties of corn compared to the germ (2.3-3.5%) and pericarp (2.6-3.1%) fractions [65]. The high proportions of PC and PI seemed to be characteristic of germ lipids in corn but the amount of PA in amylomaize (330 mg/100g dry wt) germ appeared unusually high. Lipids in corn starch are FFAs and LPLs, mainly LPC (8-226 mg/100g dry wt), LPE (1-17 mg/100g dry wt), LPG (1-7 mg/100g dry wt) and LPI (trace-8 mg/100g dry wt). The lowest amount of PLs was found in waxy corn having the lower content of amylose [60]. The fatty acid composition of the main corn PLs was well characterized in the studies cited above. Harrabi et al. [65] found that the most abundant PC species in the germ fraction contain polyunsaturated fatty acids (C18:2), while pericarp and endosperm fractions contained mainly PC molecular species rich in monounsaturated fatty acids (C18:1), confirming as reported by the same authors in the previous work (Table 4) [59]. Studying the variation in corn for fatty acid composition of TAGs and PL, Weber [66] found that the fatty acids of PLs appeared to follow the same pattern as fatty acids of TAGs, with linoleic (32.5-50.7 mol%), palmitic (23.4-44.4 mol%) and oleic (18.8-36.7 mol%) acids as the major fatty acids. Linolenic acid (0-7-1.7 mol%) resulted a minor FA. Within the phospholipids, PC had the highest level of oleic acid, PI had the highest percentage of palmitic acid but linoleic acid was higher in PE. These particular


Table 4. Distribution of the major molecular species of glycerophospholipids found in three corn kernel parts. The values reported correspond to the range of mean values for two corn varieties. The m/z values of PA, PE, PG, PC and PI show ions corresponding to [M–Na]-, [M–H]-,[M–NH4]-, [M–CH3]- and [M–Na]-, respectively.

Adapted from: Harrabi S., Boukhchina S., Kallel H. and Mayer P. 2010. Journal of Cereal Science, 51:1-6

fatty acid patterns were characteristic of each lipid class regardless of genotype. In PE and PC, a saturated fatty acid was paired more often with a monoene and monoenes and dienes were paired less frequently than predicted. In a previous work, the same author found that the percentages of palmitic and linolenic acids decreased (for all PLs, except for LPC), while the percentage of oleic acid increased (for all PLs) as the grain matured. Within the phospholipids, LPC, PI and PG showed the highest values for palmitic and stearic acid. Moreover, resulted also that all the phospholipids had a higher proportion of saturated fatty acids than did the triglycerides or glycolipids [63].


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However, this fatty acid composition could easily modified by environmental conditions. Preconditioning corn at 35°C to induce tolerance to high-temperature desiccation caused a shift in fatty acid composition of the membrane lipids resulted in increased oleic and decreased linoleic acid concentration, which would help the plant from high temperature desiccation [67].

Oat (Avena sativa L.) Oat has been traditionally used as a feed source for animal diets. However, its human consumption has increased in recent years because of some studied health benefits. Among cereals, oat is unique because of its high oil content, typically 2–12%, with a mean value of around 6-7% [68]. The different amount of lipids and the relative percentage of lipid classes are strictly related to the oat cultivars analyzed, to the seed growing conditions and mainly to the extraction solvents. For instance, Sahasrabudhe [69] chose chloroform/methanol 2:1 v/v among 7 different extracting solvents because in oat it extracted a major portion of all lipid classes. In other studies, Aro and co-workers [70,71] reported the extraction of polar lipids by supercritical fluid technology and found that this techniques was rather selective and did not permit to extract completely PLs and other polar lipids in oat. While nutritional interest in food oat has concentrated on oat as a source of dietary fiber, the lipid component has both nutritional and technological potential. Oat lipids are regarded as nutritionally important because they are highly unsaturated and contain several essential fatty acids [72]. However, oat has not been used as a source of edible oil because the amount of oil in the caryopses of commercial cultivars is quite low compared to oil seed crops [73]. Nevertheless, oat contain much higher levels of lipid than any other cereal grain, which makes them an excellent source of energy. Interest in oat lipids has a number of aspects: metabolic energy for animal feed, lipid stability and storage in both feed and food, and the effects of lipids on functionality for processing [68]. Oat kernel contains about 80% free lipids and 20% bound lipids. Hulls of high lipid content oat varieties were reported to have the smallest lipid concentration (2.3% and 0.6% of free and bound lipids, respectively) and the embryo fractions (embryonic axis, 20.6% and 2.8% of free and bound lipids, and scutellum, 12.6% and 3.3% of free and bound lipids) the greatest. Most of the total lipid found in oat kernel was in the bran and starchy endosperm, because these kernel fractions comprise the greatest part of the total kernel weight [74]. Oat starches, in contrast to those of wheat and corn, contain greater amounts of lipids (FFAs and PLs), ranging from 1 to 3% presumably as an amylose-lipid complex [75,76,77].


Of particular interest in the study of oat lipids are the high levels of polar lipids and several studies indicated that oat oil may contain 5-15% of glycolipids and 5-26% of phospholipids [69,74,78]. Based on a mean value of 8% total oil, these values indicate that oat kernels may contain 0.8-2.8% polar lipids on a dry weight basis [79]. The phospholipid composition of oat has been scarcely studied despite the important role of phospholipids in the growth, maturing and functioning of all body cells, their character as antioxidants, and their increasing uses in the supplement industry as the main constituents of lecithin. PLs were found to be mainly stored in bran (1.7%, 2.9%, 2.5% and 3.6% of total lipids for LPE, LPC, PE and PC, respectively) and endosperm (1.7%, 3.0%, 2.3% and 3.5% of total lipids for LPE, LPC, PE and PC, respectively) and only PC and PE were found in scutellum (2.6% and 0.9% of total lipids, respectively) and embryonic axis (2.8% and 1.1% of total lipids, respectively) [74]. Sahasrabudhe et al. [69] using a first step of separation by silicic acid column chromatography and thin-layer chromatography analysis determined LPE (20.4% of total PLs), PE (14.8% of total PLs), PG (9.5% of total PLs), PI (3.9% of total PLs) and PS (3.2% of total PLs) in six oat cultivars, with PC (29.9% of total PLs) being the most abundant. In the same study, the total PL content of six oat varieties ranged from 11.6 to 26 wt% of total lipids (1.20-1.83 wt% of dry kernel). In another study, the yield from phospholipids SPE extraction of 18 oat cultivars ranged from 0.725 to 0.952 g/100g of flour dry basis and the analysis of PLs by HPLC-ELSD revealed that PC was the most abundant, followed by PG and PE (289.7, 136.6 and 80.8 mg/100 g of flour for PC, PG and PE, respectively) [79]. Montealegre et al. [80] in the most recent work about phospholipids in oat carried out the analysis of PL, without purification, of five Romanian varieties by HPLC-ELSD (Figure 2) and evaluated also PL molecular species by HPLC-MS. The chromatogram reported below shows a very good separation of oat phospholipids, considering that it was performed by HPLC-ELSD without any prior fat extraction. Usually, separation by one or two dimensional TLC or purification by SPE is performed prior to HPLC analysis. However, especially by SPE the recoveries of PL have been reported to be very different and strongly dependent to the stationary phase used [15,81]. The PLs amount of the five varieties ranged from 3.8 to 10% of total lipids. The average total phospholipid content was 53.2 mg/100 g of fat and phospholipids ranged from 38.0 to 100.3 mg/100 g of fat. The phospholipid content for each variety was similar.


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PG

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Figure 2. HPLC-ELSD chromatogram of oat phospholipids from fat extract, without any prior purification. The individual content of oat phospholipids was also determined. Most of the cultivars were characterized by PE as the main component (8.9-35.6 mg/g of total lipids, 22-35% of total PLs). Except for PE, PI (8.2-16.9 mg/g of total lipids, 17-20% of total PLs), PC (8.4-23.4 mg/g of total lipids, 22-23% of total PLs), and LPC (9.4-22.6 mg/g of total lipids, 23-28% of total PLs) contents were similar in all samples analyzed. The percentage of PG ranged from 2% to 6% of total phospholipids (1.7-2.4 mg/g of total lipids). With regard to PI, their results were higher than those reported using TLC possibly because of an incomplete recovery from TLC [69]. The high content of PI is very interesting because several studies have shown that PI affects lipoprotein metabolism by controlling interactions and regulating signalling pathways [80]. As reported by some of the authors cited above [74,79], no significant genotypic variation in any PL was found in oat. However, PE, PC, LPE and LPC showed highly significant differences between growing years. Moreover, significant differences in oat kernel fractions occurred in all lipid constituents [74]. Linoleic acid was the major fatty acid of the phospholipid fraction in the range of 25.9−31.0% (% area of total FAME), and palmitic, oleic and stearic acids were the second, third, and fourth phospholipid fatty acids in the range of 23.3−24.4 %, 17.0−22.1 %, and 10.9−14.5%, respectively [80], confirming previous results obtained by Sahasrabudhe et al. which reported 38.1 mol%, 28.1 mol%, 21.3 mol% and 4.2 mol% for linoleic, palmitic, oleic and stearic acids, respectively [69]. In different oat cultivars, the unsaturated fatty acids (UFAs) ranged from 60 to 63% of total PL fatty acids. More specifically, polyunsaturated fatty acids (PUFAs) were the most representative UFAs, ranging between 33.9


and 36.8%, while the monounsaturated fatty acids (MUFAs) were 23.6−27.1% of the total PL fatty acids and saturated fatty acids (SFAs) were in the range of 36.1−40.5% [80]. Aro and co-workers [71] reported palmitic acid (42.5%) as the major fatty acid in PC fraction obtained by supercritical extraction, followed by linoleic (29.9%) and oleic acids (20.2%). According to Young et al. [74], in oat bound lipids only myristic acid was found to be disproportionally distributed between the bran (1.6%) and endosperm (0.6%), conversely to free lipids where the bran and endosperm had comparable concentrations of fatty acids, as did the whole kernel. The scutellum and embryonic axis contained less oleic acid and more palmitic, linoleic and linolenic acids than did the whole kernel. They found also that, at least for palmitic and stearic acids, some genetic variability did exist, since they were found in different amounts for different cultivars. As concerning PL molecular species, the principal fatty acids identified in PG were C16:0, C18:0, C18:1, C18:2, and C18:3. PG (C18:2/C18:3) and PG (C18:1/C18:2 or C18:0/C18:3) were the main species. Analysis of the PE class revealed eight major molecular species; these values confirmed the presence of C14:0, C16:0, C18:0, C18:1, C18:2, and C18:3 on the glycerol backbones of phospholipids. In the samples studied, PE was present as C18:2/C18:2 or C18:1/C18:3 and as C18:1/C18:2 or C18:0/C18:3. In the case of PI, analysis revealed eight principal molecular species corresponding to PI with a combination of C16:0, C18:0, C18:1, C18:2, C18:3, and C20:1 fatty acids. Moreover, PI (C16:0/C18:1) was reported as the main one. Finally, for PC, PC (C18:1/C18:1 or C18:0/C18:2), PC (C16:0/C18:1) and PC (C18:1/C18:2) were the most abundant species. As reported for the PC class, LPC fatty acid constituent was analyzed and LPC (C16:0), LPC (C18:2), and LPC (C18:1) were the first, second, and third molecular species, respectively. C20:1 was the least abundant in LPC [80]. Minor cereals: Rye (Secale cereale L.), Triticale (x Triticosecale W.), Millet (Panicum miliaceum L.), Pearl Millet (Pennisetum glaucum L.) and Sorghum (Sorghum vulgare L.) The studies on cereal lipids have been widely performed chiefly on wheat, rice, corn and oat and very important information on processing and utilizing cereal grains have thus been obtained. However, there are other cereal species important as food source of carbohydrates, proteins, lipids and minerals which deserves special attention from nutritional point of view.


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-Rye and Triticale Rye is a cereal cultivated worldwide used as the raw material for brown bread and whisky. This cereal is of particular interest because can withstand low temperature (-25°C) and can be cultivated in poor soils. Rye lipid content is quite low (whole grain rye flour contains 1.6–3.6%) and the total lipid amount, calculated on dry weight basis, is distributed between endosperm (62.3%), germ (34.5%) and bran (3.2%) [82]. Rye lipids are rich in linoleic (59%), oleic (17%), palmitic (15%), and α-linolenic (9%) acids [11]. To our knowledge, general studies on lipid content and composition of lipid classes have been widely reported previously but there are only few reports, not recent, on rye grain phospholipids [82,83,84]. The total phospholipid content of rye was reported to be 18.3% of total lipids (71% of rye lipids was neutral lipids and 10.7% glycolipids) [83] and PC accounted for 12-13 % of total lipids (0.75% wt). Besides PC, PI (2.75 % wt), PE (0.12% wt), LPC (4% wt) and NAPE were also found. LPC was located in endosperm, PC mainly in germ but also in endosperm, PE mainly in endosperm but also in germ and PI only in germ fraction. The bran fraction did not contain phospholipids. PE was found to be the main PL in endosperm but in germ, the ratio PC/PE exceeded 6:1 [82]. The molecular species of the three main PLs in rye were characterized by linoleic, palmitic and oleic as the major fatty acids of residue diglycerides after phospholipase C hydrolysis [84]. PC and PE had as major residues LL (linoleic-linoleic, 30% and 33% for PC and PE, respectively), PL (palmitic-linoleic, 28% and 24%) and OL (oleic-linoleic, 13% and 11% for PC and PE). The OL residue was the main found in PI, followed by LL (18%) and OL (9%). Linolenic and di-oleic species were minor. Thus, PC and PE contained 61-79% linoleic acid and 8-20% palimitic acid; in the case of PI, the former was 41-54% and the latter 29-43% [84]. Triticale, a cross of wheat (usually Triticum durum) and rye (Secale cereale), is the first man-made cereal. This intergeneric hybrid is believed to possess greater environmental adaptability than either of its parents, thus permitting the growing of a high-protein crop on marginal land. Most reports on the composition of triticale have been concerned with the protein and carbohydrate fractions and only some few studies on lipid and PL composition of Triticale have been carried out previously. Triticale lipid content is 2.4-3% [83], and lipids are mainly stored in endosperm (55.2%) and germ (41.9%) as TAGs (22.6 wt%) and glycolipids (10.5 wt%) [82]. PLs accounted for 17.1% of the total lipid content [83] and were characterized by PE as the main compound (5.90 wt% in whole grain,


stored in endosperm and in little amount in germ, 15.2 wt% and 2.2 wt%, respectively) followed by PC (4.3 wt% in whole grain), LPC (2.8 wt% in whole grain) and PI (1.70 wt% in whole grain). Differently from PE and LPC, PC and PI were mainly stored in germ [82]. Effectively, other authors [85], reported that PC was the main PL of triticale embryos (43-51% P of PL), PI the second (17% P of PL) and PE was the third PL (~10% P of PL). PA, PS and PG accounted for less than 5%. Moreover the same authors found that under water stress condition, the content of each PL did not change significantly in soil drought conditions. To the best of our knowledge, no specific fatty acid composition for triticale phospholipids has been reported yet. However, in the total triticale lipid extract linoleic, palmitic and oleic were the major fatty acids reported by the author previously cited. -Millet and Sorghum Sorghum and millets are important food crops in many areas of Asia, Africa and Latin America, ranking fourth or fifth in worldwide total grain production. However, they are primarily used for animal feed. Differently from other major cereal, the phospholipid composition of these cereals has not been thoroughly studied yet. Several kind of millet exist but only some species are used in human diets (Panicum miliaceum or proso millet, Eleusine coracana or finger millet and Pennisetum Americanum or pearl millet). In general, the mean oil content approaches 5.2-11% (on dry weight basis) [86,87,88] for the millets and 3.7-5.3% for the sorghum and it is mainly concentrated in germ, pericarp and aleurone layer, as in other cereals. [89]. Pearl millet typically contains about 1–5% lipids, which are concentrated in the germ and about 10% of the total lipids are bound to the starch. Millet seeds are of considerable importance in many countries as a food for human consumption but their quality deteriorates quickly after they have been ground into a meal, and the action of activated lipase and phospholipase on the lipid components is considered to be responsible for the deterioration. The neutral lipids (manly TAGs, free sterols and steryl-esters) constituted the major portion of millet lipids ranging from 80-83% of total lipids whereas glycolipids and phospholipids contents varied at 6-14% and 5-14%, respectively [87]. Ghodsizad [88] reported a phospholipid content of 1.4% of the total lipid. It has been noted that the relative amount of lipid classes is strictly dependent from the extraction solvent, reported to be different in different studies. Osagie and Kates [86] gave a demonstration

of this statement comparing the yield of each PL extracting pearled millet


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seeds with eight different solvents with increased polarity. They found that hot water-saturated butanol was the most efficient in extracting the polar lipids as well as neutral lipids. Since LPC is the most difficult lipid to extract, it was taken as indicative of the thoroughness of extraction and the authors demonstrated that 42% of LPC (% of total) was extracted with water-saturated butanol compared to less than 1% of LPC extracted with chloroform/methanol. Conversely, PC and PE were better extracted with chloroform/methanol (62% vs 24% for PC and 17% vs 6.4% for PE). PC (26.5-36.8 wt%), PE (23-30 wt%) and LPC (22-30 wt%) were the major constituents of PL class; small amounts of PA (1.5-5.5 wt%), PG (trace-9.2 wt%), PS (trace-8.5 wt%) and PI (trace-8 wt%) were also found. Among millet species, Proso millet was reported to contain the higher amounts of PS and PE than did other small millets and PI was isolated only from Finger millet. As reported in other cereals, all the PL species contained linoleic as predominant acid except Finger millet which contained oleic acid as the major constituent, followed by palmitic acid. Conversely, Foxtail millet contained the highest amount of linolenic acid (~16 wt% compared to ~5 wt% and ~8 wt% of Proso and Finger millets, respectively) [87]. In sorghum kernel, germ contains more the 70% of the oil; 2.7-4% of sorghum lipids are free lipids and only 0.1-0.3% are bound lipids, mainly as PLs. The phospholipids composition of sorghum was similar to that in millet; PLs represent about 5% of the total lipids with about a 1:1 distribution between the lecithin (PC and LPC) and cephalin (PE, PI and PS) fractions [90]. PC and LPC (36.3 wt% and 41.8 wt%, respectively) were the predominant components comprising almost 80% of this lipid class. Smaller amounts of LPE (13.6 wt%) and PE (5.5 wt%) were present, along with small quantities of PG (1.2 wt%) and PA (1.6 wt%). Lysophospholipids constitute the 55.4% of sorghum seed PLs. The fatty acid composition showed significantly amount of myristic acid in PG and PA and except for PC and PE where linolenic was the main fatty acid, high proportions of palmitic acid were found in the other PLs [89]. Pseudocereal: Amaranth (Amaranthus spp.) and quinoa (Chenopodium quinoa W.) Cereals and pseudocereals are plant materials that have similar end-uses as flours for bakery products. However, in botanical terms, amaranth, quinoa and buckwheat are not true cereals, they are dicotyledonous plants as opposed to most cereals (e.g.


wheat, rice, barley) which are monocotyledonous. Moreover, pseudocereals are broadleaf plants whereas cereals are grasses. They are referred to be pseudocereals, as their seeds resemble in function and composition those of the true cereals. The grain structure of amaranth and quinoa differs significantly from cereals such as corn and wheat; in the formers, the embryo, which is circular in shape, surrounds the starch-rich perisperm and together with the seed coat represent the bran fraction, which is relatively rich in fat and protein. In addition, the percentage of bran fraction (seed coat and embryo) in amaranth and quinoa seeds is higher in comparison with common cereals, explaining the higher levels of protein and fat present in these seeds [91]. All of these plant materials have a wide range of phytochemical constituents and are of interest to researchers in the health and medical fields [92]. Thus, in the last years, an increasing trend in research is focusing on their use in the formulation of high quality, healthy gluten-free products such as bread and pasta. However, the main limit is that commercialization of these products is still quite limited. - Amaranth (Amaranthus spp.) Grain amaranths are a small group from the genus Amaranthus, with more than 60 existing species. The main species cultivated for their seeds are Amaranthus hypochondriacus in Mexico, Amaranthus cruentus in Guatemala and Amaranthus caudatus in Peru and other Andean countries [93]. In many developed countries, the amaranth’s use has been extended mainly to rich nutritional food produced under ecological–organic production systems. In the last years, amaranth kernels have been attracting increased attention due to the importance of their rich nutritional compounds to human nutrition: with excellent protein quality, they can also be used in gluten-free special diets. Amaranth grains have also been suggested as an alternative natural source of oil and squalene. Besides nutritional interest, from a technological point of view, the substitution of 10% and 15% (on weight base) wheat flour by amaranth flour has demonstrated to play a positive effect on dough quality (increased binding of flour, better dough processing): incremented CO2 produced, enhanced porosity of bread (more regular with softer pores), and improved nutritive value of products [94]. The oil content of grain amaranth vary (from 4.8% to 8.5%) and depends on the species and on the varieties investigated [95,96,97]. Lorenz and Hwang [95] found that free lipids of amaranths (manly TAGs) varied from 5.7% to 7.2% and bound lipids (glycolipids and phospholipids) from 0.4 to


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0.9% (6.1-12.7% of total lipid content). More than 70% was identified as neutral lipid and phospholipids represent 3.6-16.3% of the total lipids [95,96]. High concentrations of squalene were found in total lipids, ranging from 3.6% to 6.1% [94]. The high price of amaranth grain probably precludes its use as a single source of squalene, but it may be feasible if the oil is obtained as a by-product in the preparation of high value defatted amaranth protein or starch [98]. Gamel and co-workers [97] studied the behaviour of PLs under technological treatment like heating, popping, air classification or seed germination and found that in Amaranthus caudatus popping and air classification treatments caused a 10% decrement of total PLs (9.2% of total lipids) compared to that of the heated or of the raw one (10.2% of total lipids). These significantly differences were not found in Amaranthus cruentus. Conversely, germinated seeds dried at different temperatures increased the total PL content in both varieties (13.1-14.2% in A.caudatus and 9.9-11.3% in A. cruentus, respectively), increasing the temperature. As in many other cereals, PE, PC and PI were identified ad quantified as the major PLs of amaranth but PA and PS was also detected [95,96]. The major fatty acids in amaranth oil PL consisted of linoleic acid (35.9–55.9%), oleic acid (18.7–38.9%) and palmitic acid (19.1–26.9%); the total saturated fatty acids of PL accounted for 29.4% and the unsaturated fatty acids reach the 70.6% of total PL fatty acids [94,96].

-Quinoa (Chenopodium quinoa W.) Quinoa, also known as quinoa or white quinoa (Chenopodium quinoa Willd.), is a native plant to the Andes Mountains and the grains and young leaves have been consumed for many years in south America. Quinoa cultivation began to decline in Andean countries with the development of intensive agriculture and the introduction of cereals such as barley and wheat brought cheaper products. Nowadays, quinoa continues to be grown only in some countries of Latin America; however, it is becoming a more and more interesting organic food crop worldwide due of its high nutritional value; it provides an exceptional combination of vitamins, minerals, high protein quality, and essential amino-acid composition. Quinoa is suitable for people with celiac disease because it does not contain gluten [94]. Moreover, the fat content is at least twice (2-10%) as high as in most cereals [99]. These lipids distinctly contribute to improve the quality of diet because of the presence of a large amount of essential fatty acids, such as linoleic and linolenic acids [100].


Many studies have been carried out on the lipid content and fatty acid composition of ether extractable materials of quinoa. However, little research has been performed on the bound lipids and total lipid content of this pseudocereal. In a study on quinoa grains, Park and Morita [100] found a change of lipid composition, in particular of PLs, during germination. In this study, the fat content of germinated quinoa ranged from 7.2 to 8.8% of dry weight basis. After germination for 72 hr, the free lipid content decreased distinctly (from 6% to 4% of dry weight basis), whereas that of bound lipids increased significantly. However, the bound lipid content of the same duration of germination increased from 2.4 (no germination) to 4.8% (72 hours of germination), respectively. These results suggest that glycerol and free fatty acids (FFAs) released by lipase are rapidly metabolized for re-synthesis of membrane bound lipids in the early germination period. PLs represented the 26.5-8.7% of bound lipids and they tended to decrease during the germination (from 0 to 72 h of incubation), varying from 0.6 to 0.4% dry wt. The NL/POL of quinoa germinated for control, 24, 48 and 72 hr was 1.04, 1.13, 1.56 and 1.56, respectively. As concerning PLs fatty acid composition, the same authors showed that all kinds of germinated samples contained linoleic acid as the most predominant fatty acid (52.2-54.6%), except for 72 hr-germination where the most predominant was oleic acid (42.4%), and oleic and palmitic acids were the second and the third (23.4-27% and 14.8-16.4%, respectively). During germination, the amount of polyunsaturated fatty acids in PLs decreased and increased the amount of saturated and monounsaturated fatty acids. Thus, the ratio ω3/ω6 varied from 0.8 to 0.05, 0.06 and 0.09 after 24, 48 and 72 hours of germination [100]. Przybylski et al. [101], in another study on quinoa seed, reported LPE as the most abundant PL which account for 45% of the total polar lipids. PC was the second most represented phospholipid component and contributed for 12% of whole seed phospholipids. A considerable variation in phospholipids was evident between different seed fractions. The overall fatty acid composition of the whole quinoa seeds was similar to that reported for other cereal grains, with linoleic, oleic, and palmitic acids as the major acids present. Phospholipids in nuts and selected oilseeds Edible nuts and seeds are cultivated and grown in a variety of growing conditions and climates, are globally popular, and are valued for their sensory, nutritional, and health attributes. Typically rich sources of lipids


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and proteins, nuts and seeds are widely used for their oils and they are also consumed directly as food due to their characteristic flavours. Traditionally nuts and oilseeds have been perceived as an unhealthy food because of their high fat content and caloric value. However, recent epidemiological studies and traditions suggests that frequent consumption of nuts and some oilseeds may be protective against coronary heart disease (CHD) [102,103]. Regular consumption of nuts is also associated with favorable plasma lipid profiles, enhancement of immune function, reduced risk of cancer, stroke, type-2 diabetes, inflammation, and several other chronic diseases [104,105]. In particular, nuts, seeds and their oils are known to contain several bioactive and health-promoting compounds and as such have long been considered an important component of the Mediterranean diet [106]. Much of the existing literature attributes the beneficial effects of nuts and oilseeds to their fatty acid composition, rich in monoinsaturated (oleic acid) or polyunsaturated fats known for their favorable effects on blood lipids and low levels of saturated fats; however very little research has been conducted on the compositions and activities of their minor components such as sterols, phenols, tocopherols and phospholipids that may confer additional beneficial properties and antioxidant effects. Information about nut and oilseed phospholipids (PLs) is lacking, although their content and fatty acid composition is important for utilisation of these plant seeds and their by-products in the food industry. The analysis of PLs is important because they contribute to the stability and quality of edible oils, fats and fatty foods through their anti-oxidative activitiy and/or contibution to the smoothness, texture, and mouthfeel of food [107,108,109]. Indeed, it is well known that PLs may act synergistically with tocopherols to delay the onset of lipid oxidation [109,110,111]; they also participate in the Maillard reaction, providing stability to oils at high temperature as well as contributing in the development of colour and flavours [112,113]. In particular, the amino group of PLs could contribute to the formation of browning substances [114]. On the other hand, PLs are responsible for oil discoloration during deodorisation and steam distillation so that their determination is necessary to evaluate the efficiency of degumming [115,116]. Some oils contain substantial amounts of PLs, e.g. sunflower oil or peanut oil, although usually these compounds are present with an avarage of 1-2% on the total fat content. The most important members of this class of lipids found in edible fats are phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS) and phosphatidylcholine (PC).


Development of a methodology for quantitative analysis of PLs becomes important to handle the quality of nonrefined oils and to evaluate the efficiency of the degumming process. Although the phosphatide content in oils can be estimated from the total phosphorus percentage, there is a need for knowledge of the PLs profile. The official methods for PLs use high-performance liquid chromatography (HPLC), which is the preferred method that replaced thin layer chromatography (TLC) [109]. The low concentration of PLs, mainly after oil rifining, requires some concentrating method before HPLC analysis. After lipid extraction, using mainly a chloroform/methanol mixture by modified Folch [13] and Bligh and Dyer [14] procedures, polar lipids are isolated by traditional solid–liquid column chromatography or by solid-phase extraction (SPE) prepacked cartridges [117]. Some researchers employ TLC with different elution system for the preliminary separation of oil PL classes, which were scraped and/or followed by enzymatic hydrolysis to permit their separation and detection by gas-chromatography (GC) [118,119,120]. Nevertheless, to enhance the resolution of the often complex mixtures of lipids, HPLC is now largely employed with different kind of detector (e.g. DAD and ELSD). In addition, recent studies have demonstrated the utility of HPLC coupled with mass spectrometer (MS) in quantitative and qualitative analyses of oil PL components. This method provide the molecular species of several oil PL classes, but the procedure still required that the fatty acids be anlysed by GC. Off-line coupling of HPLC separation with fast-atom bombardment (FAB) mass spectometry has also been used in the analysis of PLs in peanuts [110]. Besides, there have been considerable efforts in the last few years to identify oil PLs by elctrospray-tandem mass spectometry. Boukchina [121] and co-workers have described LC-MS and MS-MS methods as rapid tools for the separation and identification of the main PL classes and their fatty acid composition, without the need to chemically modify the PLs. Almond (Prunus dulcis) Almond is one of the most popular nut crops cultivated e.g. in Mediterranean countries and United States. Almond seeds are usually with a large kernel and a thin or semihard shell and they are used both as a snack and as an ingredient in other food products. Almond oil is extensively studied and is widely used in many cosmetic formulation because its beneficial action on skin. Almonds are the nuts with the lowest oil yield (~50%) but with the highest triacylglycerol (TAG) content (~98%) [122,123]. Almond oil is an oleic-rich oil (65 to 70%) accompanied by linoleic, palmitic, and minor


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acids, though its fatty acid composition can vary widely. Few reports on polar lipids of almond oil exist; however sphingolipids (~22%) and phospholpids (~78%) were found to be the principal polar lipid classes [124]. Among PLs, PC, PE and PI seemed to be the major components in Bulgarian almonds (38%, 28% and 8% of the total PLs, respectively. Table 5) [125]. Boukchina [121] and co-workers reported a similar trend with the same relative abundance for PE and PC (45%), followed by PI (8%). Miraliakbari and Shahidi [122,123] reported also high levels of PS, ranging from 21 to 39% of the total PL content. A study on almonds of Crete island showed PE as the predominant PL in immature seeds (37% of PLs), decreasing in mature seeds (14%) where the predominant PL was phytosphingosine (34%) [124]. The fatty acid composition of four indiviadual PLs (PC, PE, PI and PA) was identified by capillary gas chromatography of their methyl esters. Oleic acid (C18:1) was the predominant fatty acid in all the individual PLs and linoleic acid (C18:2) was also found to be present in high amount. Myristic (C14:0), plamitic (C16:0) and stearic (C18:0) acids predominated as saturated acids in almond PLs, where the unsaturated:saturated ratio was determined to change in the direction PI>PA>PE>PC (Table 5) [125]. Table 5. Phospholipid (PL) contents and fatty acid composition of oils and PLs of almond.

tr.: traces. Adapted from: Zlatanov M., Ivanov S. and Aitzetmüller K. 1999. Fett/Lipid, 101(11): S.437–43 Hazelnut (Corylus avellana L.) The hazelnut belongs to the Betulaceae family and is a popular tree nut, mainly distributed along the coasts of the Black Sea region of Turkey, southern Europe (Italy, Spain, Portugal, and France), and in some areas of the United States (Oregon and Washington). Turkey is the main hazelnut producer in the world, followed by Italy, the United States, and Spain [126,127]. Hazelnut is, therefore, the most popular tree nut in Europe and because its unique and distinctive flavour, it is widely used as an ingredient in a variety of food products. Moreover, hazelnuts play a major role in


human nutrition and health for their special fatty acid composition, which includes oleic and linoleic acids as well as the presence of tocopherols and sterols. Hazelnuts are an excellent source of energy due to the 60% of oil content. The principal lipid classes, isolated by column and thin-layer chromatography, include triacylglycerols as non polar lipids (98.4%) and glucolipids (1.4%) and phospholipids (<0.2%) as polar lipids [128]. Oleic acid was reported by Parcerisia et al. [128] as the main fatty acid in triacylglycerols as well as in the two main identified PL compunds (~46%), PI and PC. Linoleic acid was also predominant in polar lipids (PI=23% and PC=33%), followed by palmitic (PI=16% and PC=13%) and stearic (~4%) acids. Compared to triacylglycerols, PLs showed higher percentages for saturated fatty acids (SFAs) and polyunsaturated fatty acids (PUFAs) and lower percentages for monounsaturated fatty acids (MUFAs). The lipid class composition of Tombul hazelnut oil has also been studied using Iatroscan TLC-FID by Alasalvar and co-workers [126], revealing 1.2% of polar costituents in oil. PC, PE, and PI were main polar lipids, contributing 56.4%, 30.8%, and 11.7% to the total polar lipids, respectively. Similar results were reported by Parcerisa et al. [129], analysing non polar and polar lipid components of hazelnut oil during fruit development. At the beginning of hazelnut development PL contents showed their highest value, followed by a steep decrease; however, a small increase of PL contents was observed at the end of hazelnut maturity. The fatty acid composition of PC, the major PL in hazelnut, presented oleic and palmitic as the most abundant fatty acids, ranging from 30% to 70% and from 12% to 31% respectively, during development [129]. High percentages also of lauric, myristic and stearic acids revealed a high level of SFAs in PLs, lending further support to the previously published data [128]. Besides PC, Zlatanov et al. [125] reported also the fatty acid composition of PI, PE and PA, where the predominant fatty acids were always oleic, linoleic, palmitic and stearic acids. High levels of SFAs were found to be present in all the PLs and the unsaturated:saturated ratio was determined to change in the direction PI>PC>PE>PA (Table 6). Traces of PA have also been detected in hazelnut oil and its composition in fatty acids was characterised by high content of palmitic acid (69.5%), followed by oleic (17.4%) and myristic (8.9%) acids [123,125,129]. Despite of the other PLs, stearic acid was present only in traces (Table 6) [125]. Frequently the hazelnut oil is used to adulterate extra virgin olive oil and this fraud constitutes a serious concern since it may also have severe health implications, such as introducing hazelnut-derived allergens. Besides, the high degree of similarity between these two oils as regards triacylglycerol,


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Table 6. Phospholipid (PL) contents and fatty acid composition of oils and PLs of hazelnut.

tr.: traces. Adapted from: Zlatanov M., Ivanov S. and Aitzetmüller K. 1999. Fett/Lipid, 101(11): S.437–439

sterol and fatty acid compositions, complicates the detection of such adulteration. Recent studies have been devoted to the analysis of PLs, since this polar compounds are usually present in seed oils at a concentration range of 10–20 g/kg, while their amounts in virgin olive oils are 300–400 times lower [130]. Thus, Calvano et al. [131] developed a new selective extraction procedure involving the use of the ionic liquid arising from the combination of TBA (tributylamine) and CHCA (a-cyano-4-hydroxycinnamic acid) for the extraction and enrichment of PLs from oils. The resulting extracts were analysed by MALDI-TOF-MS using TBA-CHCA as matrix. This whole procedure was found to be very useful to obtain a PL fingerprint for each oil that can be used to detect potential markers for the presence of hazelnut oil in extravirgin oilve oil. Peanut (Arachis hypogaea L.) Peanut, or groundnut, is universally popular and it is used as a snack food or as an ingredient in the manufacture of a variety of food products [132]. Peanuts are grown worldwide in the tropics and temperate zones and they constitute a multimillion-dollar oilseed crop. Asia and Africa together contributed 94% of the word peanut oil production, while America did with 4%. Peanut seeds may be consumed raw, roasted, pureed, or in a variety of other processed forms, and they are a good source of proteins, lipids and fatty acids for human nutrition. They are rich in oil, naturally containing from 47 to 50% [133]. Peanut oil is prepared from roasted seeds and it is a pale yellow oil with distinctive nutty taste. Its odour is almost removed with refining [133]. Peanut oil is a good food oil with a high oleic content, what is associated with its good oxidative and frying stabilities. As all the vegetable oils, peanut oil primarily consist of TAGs (>95% of total lipid content) [134] but several other lipid minor compounds are also present, such as phospholipids. The PL content (0.4–1.6%) is low in peanut oil and the major classes are found to be the following: PC (38.3–66.4%), PI


(15.7–30.9%), PE (13.3–21.9%), PA (2.2–11.8%), and PG (non-reported up to 2.5%) [134,135,136]. Oleic acid (~50%) is the main fatty acid in peanut PLs, followed by linoleic (~35%) and palmitic (~18%). In particular, the concentration of saturated fatty acids (palmitic and stearic acids) in the PI is found to be markedly higher than the other PLs [134]. Yoshida and co-workers [134] evaluated a PL degradation during peanuts microwave roasting (2450 Hz of frequency), with an appreciable change at 20 min roasting. The greatest rate of PL losses was observed for PE, followed by PC or PI. After microwave roasting, the percentage of unsaturated fatty acids such as oleic and linoleic acids showed significant decreases in the PL classes, compensated by increases of saturated fatty acids such as palmitic and stearic acids (Table 7). This reduction in PLs after microwave treatment may be due to the decomposition of PLs and/or formation of other compounds, like browning substances responsible of the colour formation in peanut oil [112,137]. Because PLs are the major constituents of cell membranes, when seeds are damaged, cells release enzymes who are activated during this stress event and result in breakdown of PLs. For example, changes in PL concentration may occur when peanuts are harvested prematurely, cured at a high temperature, and/or exposed to freezing temperatures [135,138]. In many cases, the quality is affected and the oil becomes increasingly difficult to refine. Singleton and Stikeleather [135] studied the effects of these stress events founding that immature peanuts presented higher total PL content and higher concentrations of PA, PE, and PC than mature seeds. The decrease in concentration of PA and PC with maturation was explained on the basis that these PLs are the precursors to the formation of the other PLs. All PLs increased in concentration in the heat-damaged sample (at 40°C), except for PG. In contrast, in the freeze-damaged seeds, a significant increase in concentration Table 7. Phospholipid (PL) contents in oils obtained from peanut seeds roasted at different times in a microwave oven.

‘‘Others’’ include phosphatidic acid and phosphatidyl glycerol. Each value is the average of 3 replicates and expressed as relative contents in % of PLs within the total lipids (*) and the individual lipids within the total PLs(**). Adapted from: Yoshida H., Hirakawa Y., Tomiyama Y., Nagamizu T., Mizushina Y. 2005. Journal of Food Composition and Analysis, 18:3–14.


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was observed for PA and PG, whereas the concentrations of PC decreased to very low levels when compared to the control sample. This might be related to the fact that freezing induces phospholipase-D activity, which remove the choline group from PC (Table 8).

Table 8. Effect of post-harvest treatment on total phospholipids (PLs).

d.w., dry weight. Adapted from: Singleton J.A., Stikeleather L.F. 1995b. Journal of the American Oil

Chemists' Society (JAOCS), 72:485–488 In the same work, authors determined the relative content of the molecular species of PC as affected by postharvest treatment. Mature peanuts had a distribution of 40.7% C18:2/C18:2 and 59.3% C18:2/C18:1, whereas immature seeds presented greater concentrations, but equal proportions of the above mentioned species (50.0%). In contrast, molecular species found in the high temperature cured sample had a higher degree of saturation due to the presence of C18:1/C16:0 molecular species (72.8%). This fact was probably due to the oxidation of the more unsaturated molecular species by heat stress. In an other study, Singleton et al. [110] suggeted a new method to separate and characterise the molecular and fragment ions of PE, PI and PC isolated from peanuts, using a reversed- phase HPLC in tandem with a fast atom bombardment mass spectrometer (HPLC-FAB MS). In particular, five PE species (C18:2/C18:2, C16:0/C18:2, C18:1/C18:2, C16:0/C18:1, and C18:1/C18:1), six PI species (C18:0/C18:3, C16:0/C18:1, C18:1/C18:1, C16:0/C18:0, C18:0/C18:1 and C18:0/C18:0), and six PC species (C18:2/C18:2, C16:0/C18:2, C18:1/C18:2, C16:0/C18:1, C18:1/C18:1 and C18:0/C18:1) were identified by positive and negative ion FAB. This flow-FAB technique provided sufficient fragmentation for a structural information of peanut PLs. Besides, in a recent work Jonnala and co-workers [136] examined the changes in PL composition and content of peanut varieties developed through conventional breeding. Although there were some statistical differences among the PL contents and composition of peanut breeding lines


and parent lines, these variations were within the range reported for traditional peanut varieties [135,138]. All the breeding lines were rich in PC. Pistachio (Pistacia vera L.)

Among Pistachio trees, Pistacia vera L. is the only species that produces edible nuts and it belongs to the Anacardiaceae family. This nut is widely appreciated all over the world for its peculiar organoleptic characteristics and it is mainly cultivated in the United States, western Asia, and some Mediterranean countries (Italy, Turkey, Greece, and Tunisia). Pistachio seeds are consumed raw, sun-dried, or roasted, as snack food and/or as ingredients in the confectionery industry, while the shells have been proposed as a raw material to prepare activated carbons [139]. Furthermore, P. vera seeds are of high economic value due to their balanced composition, characterised by a low carbohydrate content of about 10%, a protein content of more than 20%, and a lipid content varying from 40 to 63%, all on a dry weight basis [140]. The pistachio is one of the oleaginous seeds with the highest amount of polar lipids (~2%) [122,123]. PLs are present in a major quantity (~1.5%) and the main compound is PC, followed by PS and PI at 45, 40, and 20%, respectively [122,123]. Chahed et al. [140] in a study of the lipid evolution during pistachio seed replenishment, showed how the PL fatty acids were predominating during the first stages of seed development. After the 10th week after impollination (WAP), TAGs became the predominantig lipid class probably obtained from PLs breakdown, especially from PC [141,142]. Besides, during seed development, C18:2, C16:0 and C18:1 were the most abundant FAs in PLs. In particular, during the first stages C18:2 was predominating, whereas C18:1 became the major FA from the 11th WAP. In an other work, Chahed and co-workers [143] reported the differences in total PL content of two different pistachio varieties, cultivated in four different Tunisian regions. Statistical differences among the PL contents were found, indicating a probable effect of geografical location and variety on pistachio seed quality and composition. Recently, three populations of Pistacia lentiscus fruits were analysed for their contents, classes and different molecular species of PLs in order to promote their production and marketability. The LC-ESI-TOF-MS and MS/MS were used to accomplish this analysis and four main classes of PL were detected: PA, PE, PG and PI. The latter was found to be the dominant class in the all provenances of lentisc fruit (from 37 to 59% of total PL). Besides, various molecular species were detected in each class of PL. In particular, the predominant molecular species of PA were C16:0/C18:2


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and C18:1/C18:2, whereas the minor species were C16:0/C18:3 and C18:3/C18:2. In the PE class, C18:1/C18:1 and C18:2/C18:2 were the major species identified from the negative ESI-MS spectra. The phospholipids C18:2/C18:2, 18:2/C18:1, and C16:0/18:2, C16:0/18:1 were the most abundant species within the PG and PI classes, respectively. Among lentisc populations, a significant difference in the relative observed abundance of various PL classes as well as of the various molecular species of each class was observed. These results prove that environmental variations, climatic factors and type of soil have a strong influence on the PL composition of seed [144]. Pumpkin seed (Cucurbita spp.) Pumpkin seeds are a useful source of oils (37.8-45.4%) and proteins (25.2-37.0%) and they are utilised in several countries as snacks after salting and roasting for human consumption [145]. Pumpkin seed oil has been mainly produced and sold in the southern parts of Austria, Slovenia, and Hungary [146]. Besides, oil of pumpkin seeds is used as cooking oil in some countries in West Africa and the Middle East [147]. Pumpkin seed oil typically is a highly unsaturated oil, with predominantly oleic and linoleic acids present. The highly unsaturated fatty acid composition of this oil makes it well-suited for improving nutritional benefits from foods. Pumpkin seed oil has been implicated in providing many health benefits [148]. The most critical health benefit attributed to pumpkin seed oil is preventing the growth and reducing the size of the prostate [149]. As for all oleaginous plants, TAGs are the main component of the pumpkin seeds (92.7-93.4%), whereas PLs represent only the 1.5% of the total lipid content [150]. The main PL compound in the kernel of pumpkin seeds is PC (~55%), followed by PI (~25%) and PE (~20%) [151]. The fatty acid profile of PLs has high amount of unsaturated fatty acids, ranging from 68.5 to 70.2% and consisting mainly of oleic and linoleic acids. However, the amount of saturated acids, such as palmitic and stearic acid, is higher in PLs compared with those of TAGs and free fatty acids (FFAs) [150]. Yoshida et al. [151,152] have studied the effects of microwave roasting (2450 MHz of frequency) on PLs in kernels of pumpkin seeds. With longer roasting time, the total PL content was reduced to two-third of the initial levels and the rate of PL losses increased in the followed order, PI, PC and PE. The fatty acid distribution differed among individual PLs and significant differences occurred when the seeds were microwaved for 20 min or more. In particular, longer microwave processing caused higher roasting temperatures that results in a lower percentage of linoleic acid and a greater percentages of oleic, palmitic and steraic acids in three PLs.


The reduction of PLs following microwave treatment may be due to the decomposition of PLs and/or formation of a complex with protein or carbohydrate [152]. Sesame seed (Sesamum indicum L.) Sesame is one of the world’s most important oilseed crops, cultivated for centuries for its high content of both excellent quality oil (42-54%) and protein (22-25%) [118,119,153,154]. Sesame seed is used extensively in baked goods and confectionery products. Not only it is a source of edible oil, but the seed itself provides a nutritious food for humans as a health food, which increase energy and prevents aging [155]. Oils from roasted and unroasted sesame seeds have a mild taste and they are widely used and cultivated in the eastern Asian countries, especially in India, China, Myanman and Japan. One excellent characteristic of sesame oil is its resistance to oxidative deterioration. Sesame oil is composed of a 90-96% TAGs and of 2-3% PLs and it is high in unsaturated fatty acids (approximately 85%) [119,154]. Sesame oil contains almost equal levels of oleic (35 to 54%, average 40%) and linoleic (39 to 59%, average 46%) acids along with palmitic (8 to 10%) and stearic (5 to 6%) acids. However, sesame seed oil resists oxidative deterioration [156]. Its remarkable stability may be due to the presence of the endogenous antioxidants, sesamol and sesaminols, together with tocopherols [157]. The conventional method for the preparation of sesame oil involves cleaning, roasting, grinding, cooking and pressing but not refining [158]. The roasting process is the key step for making sesame oil, since the colour, composition and quality of sesame oil are all influenced by the conditions of the roasting process. For these reasons, Yoshida and co-workers [118,119,159] studied the optimum roasting conditions for preparation of oil with good quality from white sesame seeds when roasted in a domestic electric oven. With increased roasting time the amounts of PLs decreased gradually and this trend became more pronunced in the oils prepared using a 250°C roasting temperature [118]. There was almost no change in fatty acid composition of PLs of the sesame oil when prepared by roasting below 200°C. But the higher the roasting temperature and the longer the roasting time, the greater was the percentage of palmitic and oleic acids, and the less was that of linoleic acid. On the other hand, significant differences occurred in fatty acid distributions of PLs in the oils after 15 min roasting at 220°C. Furthermore, the retention of total fatty acid contents in PLs of sesame oils prepared by roasting at 250°C decreased substantially (41.2, 9.0 and 3.6% at 5, 15 and 25 min, respectively) (Table 9). The differences may be attributed to the degradation


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Table 9. Fatty acid distribution of PLs in oils obtained from sesame seeds roasted at different temperatures in an electric oven.

Each value is the average of 3 replicates. The content of fatty acids in each sample was calculated relative to the unroasted sample (100%). The content of each individual fatty acid is given as a percentage of the corresponding total. Adapted from: Yoshida H. and Takagi S. 1997. Journal of the Science of Food and Agriculture, 75, 19–26 of PLs depending on the formation of browning substances by roasting. These results indicated that a high-quality product would be obtained by roasting sesame seeds for 25 min at 160 or 180°C, 15 min at 200°C and 5 min at 220°C in a domestic electric oven [118]. Yoshida et al. [159] showed also the changing patterns of the principal PLs (PC, PE and PI) in the sesame seeds before and after roasting. With increasing roasting time the greatest PL losses were observed for PE, followed by PC and PI. These trends became pronounced with longer roasting times and higher roasting temperatures. At elevated roasting temperatures, some of the naturally occurring classes of PLs, in particular PE, greatly enhance the activity of primary antioxidant in vegetable oil [160]. Besides, authors showed how the positional distribution of fatty acids of the PC in sesame oil was retained during roasting: unsaturated fatty acids, especially oleic and linoleic, were predominantly concentrated in the sn-2-position, and saturated fatty acids, particularly palmitic and stearic acids, primarily occupied the sn-1 or sn-3-position. These results suggest that unsaturated fatty acids located in sn-2-position are significantly protected from oxidation during roasting in a domestic electric oven [161]. The same trend in the positional distribution of fatty acids was also observed in all PLs


(PC, PE and PI) of three different unroasted sesame seed cultivars: white, yellow and black [154]. However, the concentration of saturated fatty acids in the sn-1-position of PI was markedly higher than that of PE or PC, probably because of differences in their biosynthetic pathway. In general, no essential differences were observed in the content and composition of PLs among the three cultivars. The major fatty acids in the three PL fractions (PC, PE and PI) for each genotype were linoleic, oleic, stearic and palmitic acids. In particular, these fatty acid distribution patterns were higher in unsaturated fatty acids for PE and PC than in those for PI [154]. Sunflower seed (Helianthus annuus L.) The sunflower is one of the most important oilseed crops in the world. The nutritional quality of the sunflower oil ranks among the best vegetable oils in cultivation and is widely used as salad oil, cooking and frying oil and in margarine production. The high nutritional value of the traditional sunflower oil is due mainly to its fatty acid composition. It is a combination of monounsaturated (oleic acid, 16-19%) and polyunsaturated (linoleic acid, 68-72%) fats with low saturated fat levels (e.g. palmitic acid, 6% and stearic acid, 5%) [162,163]. Traditional sunflower oil rich in linoleic acid (60–75%) is used in the food industry and in various commercial products. Linoleic acid is an essential fatty acid for humans and it is preferred by industries when oil hydrogenation is require [164]. Because of the high level of PUFA, sunflower oil is susceptible to oxidation during frying and roasting [120]; however, as for all vegetable oils, the quality and stability of sunflower oil is also influenced by the presence of minor costituents, such as PLs. The major PLs in sunflower seed oil are PC, PE, PI and PA, with a total concentration lower than 1.2% [165]. PLs are natural components of oilseeds that pass to oil during extraction; however they are removed at the crushing plant by degumming with water and almost completely removed from crude oils during refining. Some authors demonstrated that oil obtained by solvent extraction has a higher concentration in PLs than that obtained by pressing, with particular high content in PE and PC [109,166]. However, no significant differences in the PL profiles were observed. Besides, the water-degumming process produced a decrease in PL content, indipendently of the method of oil extraction. Degummed oils contained higher percentages of PA and lower percentages of PC than original crude oils. This is consistent with the fact that PA is the less hydratable and PC is the most hydrophylic of the phosphatides occurring in sunflower oil, thus PC can be better removed from the oil by degumming with water [166]. Yoshida et al. [120,167] studied the influence of microwave roasting on the composition and positional


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distribution of fatty acids in PLs in the kernels of sunflower seeds roasted in a domestic microwave oven (at a frequency of 2450 MHz). In the unroasted seeds, PC was the main PL, followed by PI and PE but the greatest rate of losses during roasting was observed for PE, followed by PI or PC (Table 10). These trends became more pronounced with longer roasting time (after 20 min), although these losses were not so pronounced as observed after roasting sesame seeds [118,119]. The hull of sunflower seeds may somewhat protect the lipid components in the kernels from microwave energy. The major fatty acids in the three PLs were found to be linoleic (55-65%), oleic (15-20%), palmitic (10-30%) and steraic (5-10%) acids [120,167]. However, PI was unique in that it had the highest saturated fatty acid content among the three PLs, with particular concentration in the sn-1-position. Significant differences in fatty acid distributions occurred when sunflower seeds were microwaved for 20 min or more. The longer the roasting time, the greater the relative percentages of palmitic, staric and oleic acids, and lesser that of linoleic acid. Nevertheless, the principal characteristics for the positional distribution of fatty acids in the three PLs were retained during microwave roasting, as observed in sesame seed oil [119]: unsaturated fatty acids predominantly occupied the sn-2-position, and saturated fatty acids were highly concentrated in the sn-1- or sn-3-position after 30 min of microwave roasting. The results suggest that no significant changes in fatty acid distribution of PLs would occur within 12 min of microwave roasting, ensuring that a good-quality product would be attained. Some authors showed how the qualitative composition of PLs in sunflower seeds are formed pratically completely in the first 15 days after flowering [164]. In particular, they studied changes in PLs in developing seeds of a selection of high oleic acid sunflower variety (HOS) grown in Bulgaria (Diamant variety). PC, PI, PE, PA, PS, LPC, MPG and DPG were dected in the high oileic sunflower kernel oil over the whole examination period. PC, PI and Table 10. Phospholipid (PL) contents in oils obtained from sunflower seeds roasted at different times in a microwave oven.

Each value is the average of 3 replicates and expressed as relative contents in % of PLs within the total lipids (*) and the individual lipids within the total PLs(**). Adapted from: Yoshida H., Hirakawa Y. and Abe S. 2001. European Journal of Lipid Science and Technology, 103:201–207.


PE were the main components. Since PA is the first to be biosynthesised and it is a precursor for the biosynthesis of PC, PI and PE [168], as expected, its amount was higher in the early stages of the seed development and then decreased gradually (from 25% on the 15th day down to 2% on the 90th day). Accordingly, the amounts of PC and PE increase from 31 to 39% and from 5 to 18%, respectively, while the amount of PI remains the same. The other PL species were in insignificant quantities which practically did not change during growing. The fatty acid composition of the main PL classes (PC, PI, PE and PA) did not change during the growing period; whereas the respective quantities changed with the percentage of saturated fatty acids decreasing and that of unsaturated fatty acids increasing due to the substantial increase in the amount of oleic acid (while the amount of linoleic acid decreased). Besides, while fatty acid composition of PC hardly changed throughout the investigated period, a major increase of oleic acid content between the 30th and the 60th day of seed developing occured in PE and PI [164]. These results confirm the good quality of the HOS oil with a beneficial fatty acid content and it has good prospects as a salad and cooking oil. Lipid characterisation of oil from the wild sunflower species Helianthus petiolaris Nutt was also evaluated [169]. Wild sunflower seeds yielded oil content between 27 and 30% that it is lower compared with cultivated sunflower (H. annus) (55%) [167]. Besides, this oil showed higher concetration of unsaturated fatty acids and lower level of tocopherols and PLs, making it a product with low quality and stability. In particular, the PL content was comparable to those for water degummed sunflower oils, which had values between 0.10–0.21%. The relative proportions of the main PLs varied widely, i.e., PC (8.4–17.1%), PI (5.1–44.0%), PE (8.2–16.8%), and PA (26.2– 78.3%). The PL profile exhibited a high relative percentage of PA, as is the case with water-degummed sunflower oils [109]. Walnut (Juglans regia L.) Walnut belongs to the Juglandaceae family and it has been used in human nutrition since ancient times. The walnut tree is native to central Asia and is now cultivated throughout southern Europe, northern Africa, eastern Asia, the United States, and western South America. China is the leading world producer, followed by the USA, Iran, Turkey, Ukraine, Romania, France and India, but production in other countries such as Chile and Argentina has increased rapidly in recent years. Walnut is a crop of high economic interest to the food industry: the edible part of the fruit (the seed or


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kernel) is consumed, fresh or toasted, alone or in other edible products. It is globally popular and valued for its nutritional, health and sensory attributes. Walnut is a nutrient-dense food mainly owing to its high fat content (60-70%) and protein, vitamin and mineral profiles. Considering all kernel components, many studies have described various health beneficial effects of walnut-supplemented diets in comparison with reference diets. According to Simopoulos [170], walnuts are unique because they have a perfect balance of n-6 (linoleic acid) and n-3 (α-linolenic acid) polyunsaturated fatty acids, a ratio of 4:1, which has been shown to decrease the incidence of cardiovascular risk and to be crucial agents in the regulation of the transepidermal water loss [171]. Walnut phenolics may also have health effect owing to their good antioxidant, antiatherogenic, anti-inflamatory and antimutagenic properties [172]. Walnut kernel mainly contains lipids, among with TAGs are present in very high concentration (>95 g/100 g oil) [122]. Among nut oils, walnut oil contains the lowest amount of MUFAs (~15–20 g/100 g of oil) and the highest level of PUFAs (>50 g/100 g of oil) [122,173]. The composition of TAGs is largely of unsaturated FAs, mainly linoleic acid together with oleic and linolenic acids in similar amounts. However, walnut oil contains 2-3% of polar lipids, consisting of 73.4% (2.3% in total oil) sphingolipids and 26.6% (0.8% in total oil) PLs. About the PL composition of walnut oil, literature reports quantitative different results. According to Miraliakbari and Shahidi [122,123], PC is present in a major amount, more than PS and PI, with a mean content of of 0.38, 0.36, and 0.22 g/100 g of oil, respectively. In Greek walnut seeds, PE was found to be the main PL with a precentage of 48.5% of total PLs [174]. Otherwise, Zlatanov et al. [125] reported high content in PI (45% of total PLs), followed by PC (18%), PE (15%) and PA (7%) in oil obtained from Bulgarian walnut seeds (Table 11). The analysis of fatty acids of the total PLs by GC-MS showed linoleic acid (50.9% of total PLs) as the main fatty acid, followed by palmitic (22.6%) and linolenic (17.2%) acids. Conversely, oleic acid (2.3%) was present in small amount, lower than stearic acid (4.6%). Therefore, the polyunsaturated fatty acids were the most abundant of the unsaturated fatty acids of total PLs, and the PUFAs/MUFAs ratio was 29.2 [174]. Zlatanov and co-workers [125] reported also the fatty acid composition of the individual PLs in Bulgarian walnut oil. Palmitic acid was the principal fatty acid in PC and PI (41.7 and 36.2%, respectively), followed by stearic (39.5 and 30.6%) and oleic (10.3 and 17.7%) acids. Stearic acid was present


Table 11. Phospholipid (PL) contents and fatty acid composition of oils and PLs of walnut.

tr.: traces. Adapted From: Zlatanov M., Ivanov S. and Aitzetmüller K. 1999. Fett/Lipid, 101(11):

S.437–439 in major amount in PE (32.8%), more than palmitic (29.6%) and oleic (19.4%) acids; whereas PA reported the highest level of palmitic acids (47.2%). High amounts of linoleic and linolenic acids were also found in all PL classes, ranging from 12.6 to 5.0% and from 7.6 to 1.4%, respectively. In particular, the unsaturated:saturated acid ratio was determined to change in the direction PE>PI>PA>PC (Table 11). Minor nuts and oilseeds: Brazil nut (Bertholletia excelsa H.B.K.), Cashew (Anacardium occidentale L.), Macadamia (Macadamia tetraphylla and M. integrifolia), Peacan (Carya illinoinensis) and Pinenut (Pinus pinea) There is no accepted definition of “minor nut and seed” oils, however there is a wide range of oils produced, sold, and used in still low quantities compared to the ones discussed above. Because the list of these nut and seed oils is almost endless, in this work has made a selection based on the frequency with which they are reported in the literature and the worldwide diffusion of their crops and uses. These oils are generally of interest because they contain components, which give the oil interesting healthy or technical properties. Brazil nut is a native plant from the Amazonian region (Brazil, Perù, Colombia, Venezuela, and Ecuador) and it is used most extensively in confections in Europe and North America [175]. The Brazil nut is also used in the cosmetic industries and it has a well-known nutritional value due to its high content of lipids (50–70%), proteins (10–20%), and carbohydrates (10–20%) [176]. It is high in essential fatty acids (39.3% of oleic acid and 36.1% of linoleic acid) [177], amino acids containing sulfur (methionine and cysteine), vitamins (A and E), fibers and minerals, especially selenium.


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Brazil nuts have TAGs as the major lipid class (>95 g/100 g oil) [122] and their saturated fat content is the highest among all nuts and oilseeds (~20% of total fat). Besides, brazil nut oil contains ~2% of polar lipids with the PLs as the main class [122]. PI and PC range from 16 to 31% and 24 to 53% of total PL content, respectively. PS, PA, and PE account for about 30, 24, and 21% of total PL content, respectively [122,177]. About the fatty acid composition of PLs, palmitic acid was the major fatty acid in PA, PC and PI (38%, 34% and 26% of total PLs, respectively), followed by oleic (14-31%) and staric (18-23%) acids. PE reported linolenic acid as main fatty acid (34%), followed by oleic (23%) and palmitic (18%) acids. This fatty acid composition of PLs was found to be different from the FA composition of brazil nut oil: oil contained more linoleic (36.1%) acid than PLs, which are present, on average, at 10%; PA and PI contained high level of lauric acid (10-12%) whereas the oil has a very low quantity (0.2%) and PE contained 34% of linolenic acid while the oil does not contain any [177]. Cashew is one of the nut crops cultivated in the tropical regions of India, Brazil, and Africa. An interesting aspect of the tree is the “false fruit”, known as cashew apple that is the receptacle for the true fruit, the cashew nut. India is the largest producer and exporter of the cashew kernel, accounting for almost 50% of the world export [178]. The cashew nut is a good source of proteins (20%), carbohydrates (23%), and fats (45%) [179]. Of the fat, neutral lipid accounted for 96%, in which oleic acid (56%) and linoleic acid (18%) are the major fatty acids [180,181,182]. The cashew nut contains ~3% of polar lipids [183]. The sphingolipid classes found in cashew nuts were cerebrosides and ceramides that showed positive effects on colon carcinogenesis [184]. The thin layer chromatography of cashew kernel PLs revealed four principal PL classes: LPC (Lysophosphatidyl choline), PC, PE and PS. Maia et al. [185] reported the highest percentages for PC (53.6%) and PE (14.0%), which together contributed over 60% of the total PLs; whereas Nagaraja and co-workers [186] accounted similar amounts for PC and PE with an avarage percentage of 11%. LPC and PS showed lower content, ranging from 5.1 to 7.0% and from 6.5 to 7.5%, respectively. More than 50% of the fatty acid pattern of the total cashew PLs was represented by oleic acid. The other two main fatty acids were palmitic and linoleic acids with an avarage of 29.6 and 16.3%, respectively [186]. Maia and co-workers [185] detailed how these main fatty acids together represented 85.3% of the total in PE and 73.3% of the total in PC. Besides, PC showed greater percentages of lauric, myristic and stearic acids, whereas PE showed greater values of palmitic, oleic and linoleic. Therefore, PE was 73.5% unsaturated and PC 62.6%.


The macadamia is a large evergreen tree indigenous to the coastal rainforests of Australia that belongs to the botanical family of Proteaceae. Australia is the largest producer of macadamia nuts followed by the United States, South Africa and New Zealand [187]. There are two species, Macadamia tetraphylla and integrifolia, which produce edible nuts; these species are also known as a rough-shell and a smooth-shell type, respectively, for their characteristic surface texture of the shells [188]. Macadamia nuts have a high oil content of about 75 mg/100 g of the nut [189,182] and the major fraction of the oil is represented by TAGs, accounting for about 80% of total lipids. Besides, these nuts are rich in MUFAs (~80%), predominantly oleic (49.6-65.1%) and palmitoleic (17.3–30.8%) [190,182]. Macadamia nuts contain higher levels of MUFAs than any other food source known, making it good for skin care. At maturity the macadamia nut contains ~3% of polar lipids [188]. During drying and roasting, polar lipids increase from 2 to 7% [191]. Thermal treatments are essential for the preservation of the nuts and the development of their good flavour and taste. Among polar lipids, PLs are present in high amount, accounting for ~85% of total polar lipids and their main classes are represented by PE and PC. As polar lipids were found to be also present cerebrosides (~7%), acylsteryl-glucosides (~6%) and steryl-glucosides (~1%). Pecans, native to the central and eastern North America and the river valleys of Mexico, belong to the Juglandaceae family that also include walnuts, hickory nuts, heartnuts, and butternuts. Popularly used as a snack food (roasted/salted), pecans are also used in a variety of food products including the widely enjoyed pecan pie, baked goods, candy and confections, dessert toppings, salads, and several main dishes. A pecan nut is a high-energy food (~690 kcal/100 g) as lipids [up to 75% (w/w)] and carbohydrates [up to 18% (w/w)] make up the bulk of the seed kernel weight [192]. Pecan nuts are rich in proteins, vitamins (especially vitamine E), calcium, magnesium, potassium, zinc, fibers, and antioxidants [193]. Pecan has been ranked among foods with the highest phenolic content, thus it can be considered an important dietary source of antioxidants [194]. Pecan nuts contain 70–75% of oil, mainly composed of oleic acid (~65%), linoleic acid (~25%), and palmitic acid (~6%). This oil is found to be very poor in saturated fatty acids (<9%), and rich in monounsaturated fatty acids, improving human serum lipid profile and lower LDL levels [195]. TAGs represent the major neutral lipid class (~96% of total lipid content) and PLs the main polar lipids class with a level of about 1g/100g of pecan oil. PC and PS were found to be the most abundant PLs (0.23–0.52 and 0.24–0.47g/100g of oil, respectively), followed by PI (0.2–0.7 g/100 g of oil) [122,123].


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Erickson [196] proved the contribution of PLs to headspace volatiles during storage of pecans. During storage, TAG amount did not change significantly, whereas a decrease in PL content were seen. Because the PL losses did not coincide with increases in FFAs, author postulated that PL losses arised from either oxidation of esterified fatty acids of the PL fraction or from binding of PLs to nonextractable components. Besides, PL fraction contained nearly twice the levels of PUFAs as the TAG fraction and significant losses in 18:2 and 18:3 were recorded for the PLs, which appeared to have served as a major site of oxidation. Based on a strong negative correlation between hexanal and its precursor fatty acid (18:2) in PLs, the results suggested that membrane lipids would be a primary site of attack during the early stages of oxidation. Future studies with oilseeds should therefore examine the possibility that variations in PL fatty acid composition could explain cultivar differences in storage stability. Pine nuts are consumed raw and roasted and as ingredients in many traditional dishes and the most common nuts come from five species: the European stone pine, Pinus pinea, the Mexican Pinus cembroides, the Asiatic Pinus koraiensis and Pinus sibirica, and the Californian Pinus monophylla [197,198]. Pinus pinea is the specie principally widespread in the Mediterranean area (Spain, Portugal, Italy, Greece, Albania, and Turkey), where there is its highest production and consumption. It is called the “Stone Pine” and the “Umbrella Nut” as the tree grows in stony ground and shaped like an umbrella. They contain adequate amounts of all of the essential amino acids [132], and they are a source of important vitamins (B1, B2, and K) and minerals especially potassium and phosphorus [199]. The composition of the pine nut shows variation among the species depending on geographical and climatic conditions. The pine nut oil content varies from 31 to 75% and TAGs represent the major lipid class 96%, while diacylglycerol, polar lipids, and free fatty acids are in lesser proportions (1.95%, 0.84%, and 0.93%, respectively) [122]. In most species oleic and linoleic acids are the principal acids accounting for about 70% followed by the pinoleic acid (about 17%). Sphingolipids are the main polar lipids with a level of about 0.28–0.57 g/100 g of pine nut oil. Among PLs, PC and PS are the most abundant classes (0.14–0.37 and 0.15–0.33 g/100 g of oil, respectively), followed by PI (0.07–0.19 g/100 g of oil) [122,123]. References 1. Erickson M.C. Phospholipids: Structures and Physicochemical Activities. In:

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review article - semantic scholarseed consists of two major components, the endosperm and embryo or...

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