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Nut Bioactives: Phytochemicals and Lipid-Based Components of Almonds, Hazelnuts, Peanuts, Pistachios, and Walnuts

Nut Bioactives: Phytochemicals and Lipid-Based Components of Almonds, Hazelnuts, Peanuts, Pistachios, and Walnuts

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186



Almond

(Prinus dulcis)



Fruit and Cereal Bioactives: Sources, Chemistry, and Applications



Hazelnut

(Corylus avellana L.)



Peanut

(Arachis hypogaea L.)



Pistachio

(Pistacia vera L.)



Walnut

(Juglans regia L.)



Figure 9.1  (See color insert) Almond, hazelnut, peanut, pistachio, and walnut.



Table 9.1

Fatty Acid Composition of Selected Nuts and Selected Oils as Percentage of Total Fat by Weighta

Fatty Acid

Total Fat



10:0



12:0



14:0



16:0



18:0



18:1



18:2



18:3



% of total fat by wt

Nuts

Almonds

Hazelnuts

Peanuts

Pistachiosb

Walnuts



52.2

62.6

49.2

50.0

56.6



0.0

0.0

0.0

0.0

0.0



0.0

0.0

0.0

0.0

0.0



0.6

0.2

0.1

0.0

0.0



6.6

5.0

10.5

9.9

3.7



1.9

2.0

2.2

2.1

2.5



63.7

77.7

48.1

69.6

21.0



20.1

9.3

31.6

15.4

59.2



0.7

0.2

0.0

0.5

5.8



Mean



54.1











0.2



7.1



2.1



56.0



31.7



1.4



Oils

Olive oil

Canola oil

Safflower oil



100

100

100



0.0

0.0

0.0



0.0

0.0

0.0



0.0

0.0

0.0



11.0

4.0

4.8



2.2

1.8

1.3



72.5

56.1

75.3



7.9

20.3

14.2



0.6

9.3

0.0



Data reported by:

Kris-Etherton, P., Yu-Poth, S., Sabate, J., Ratcliffe, H., Zhao, G., and Etherton, T., Amer. J. Clin. Nutr., 70,

504s–511s, 1999.

b Arena, E., Campisi, S., Fallico, B., and Maccarone, E., Food Chem., 104, 403–8, 2007.

a



Several large prospective studies have found an inverse relationship between nut consumption and

cardiovascular disease (CVD) risk (Fraser et al. 1992; Fraser 1999; Hu et al. 1998; Ellswort et al. 2001;

Albert et al. 2002). 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 (Grunwald 1975; Phillips et al. 1999; Moreau et al. 2002). These beneficial

effects of healthy diets containing specific tree nuts are attributed to their high levels of monounsaturated

or polyunsaturated fats, known for their favorable effects on blood lipids and low levels of saturated fats.

Compared with high-oleic-acid vegetable oils (olive, canola, and safflower), nuts have less saturated fatty

acids (SFA) than olive oil and slightly more SFA than canola and safflower oils on average. The oleic-acid

content of nuts is similar to that of canola oil, but less than that of olive oil and safflower oil. Canola oil

and nuts contain similar amounts of linoleic acid, and these amounts are appreciably greater than those

present in olive oil and safflower oil (Kris-Etherton et al. 1999). The fatty acid profiles of selected nuts

and vegetable oils are shown in Table 9.1.

Besides having a healthy lipid composition, nuts contain dietary fiber, plant proteins, folic acid, various

micronutrients including manganese, copper, magnesium, phosphorus, zinc, and bioactive constituents

(“phytochemicals”) that may confer additional beneficial effects (Kris-Etherton et al. 1999). They are

also rich sources of several antioxidant substances such as antioxidant vitamins, phenolic compounds,

and phytosterols (Table 9.2). Phenolic compounds in nuts are mainly located in the skin or testa (Milbury

et al. 2006; Monagas et al. 2007), which is usually removed by blanching or roasting for the use of



Bioactive Substances of Selected Nuts per 100 g of Dry Weight*

Nut Item

(specie)

Almonds

(Prunus dulcis)

Hazelnuts

(Corylus avellana L.)

Peanuts

(Arachis hypogea L.)

Pistachios

(Pistacia vera L.)

Walnuts

(Juglans regia L.)



Anthocyanins



Flavonoids



Stilbenes



Total Phenols



Phytoestrogens



Tocopherols



Chlorophylls



Xanthophylls



(2.46)a



(28.7)

0.018–93.5b

(37.9)

0.027–113.7f

(94.9)

0.094–189.8j

(26.7)

0.033–143.3p

(333.4)

0.031–744.8v



nd



(90.0)

12.4–239c

(210.9)

8.0–425g

(357.9)

8.0–645.9l

(335.0)

15.8–867r

(814.5)

21.0–1625w



(40.0)

0.112–120d

(0.093)

0.080–0.107h

(110.0)

0.173–220m

(36.14)

0.062–108s

(35.93)

0.139–107.5x



(23.6)

17–27.44e

(30.6)

15.36–45.5i

(9.7)

4.8–16n

(24.6)

8.4–53.0t

(24.3)

14.9–31.72y



nd



nd



nd



nd



nd



nd



(14.3)u



(3.8)u



nd



nd



(6.7)a

Nd

(26.2)

24.3–28.1o

Nd



nd

(0.096)

0.002–0.2k

(0.24)

0.009–0.71q

nd



187



Note: Data are expressed as means (in parentheses) and range.

nd, not detected.

* Data reported by Ballistreri, G., Arena, E., and Fallico, B., Acta Horticulturae, in press, 2010a.

Data reported by:

a  Harnly, J. M., Doherty, R. F., Beecher, G. R., Holden, J. M., Haytowitz, D. B., Bhagwat, S., and Gebhardt, S., Journal of Agricultural and Food Chemistry, 54, 9966–77, 2006.

b,c  Milbury, P. E., Chen, C. Y., Dolnikowski, G. G., and Blumberg, J. B., Journal of Agricultural and Food Chemistry, 54, 5027–33, 2006.

b,d,f,h,p,s,v,x  Thompson, L. U., Boucher, B. A., Liu, Z., Cotterchio, M., and Kreiger, N., Nutrition and Cancer, 54, 184–201, 2006.

b,d,f,h,j,m,p,s,v,x  Kuhnle, G. G. C., Dell’Aquila, C., Aspinall, S. M., Runswick, S. A., Mulligan, A. A., and Bingham, S. A., Journal of Agricultural and Food Chemistry, 56, 7311–5, 2008.

b,c,f,g,j,l,p,r,v,w  Yang, J., Liu, R. H., and Halim, L., LWT—Food Science and Technology, 42, 1–8, 2009.

c,e,g,i,l,n,r,t,w,y  Kornsteiner, M., Wagner, K., and Elmadfa, I., Food Chemistry, 98, 381–7, 2006.

c,e,g,i,r,t,w,y  Miraliakbari, H., and Shahidi, F., Food Chemistry, 111, 421–7, 2008.

c,r,v  Arcan, I., and Yemenicioglu, A., Journal of Food Composition and Analysis, 22, 184–8, 2009.

d,e,i,m,n,s,t,x,y  Kocygit, A., Koylu, A. A., and Keles, H., Nutrition, Metabolism & Cardiovascular Diseases, 16, 202–9, 2006.

e,g,i,l,n,r,t,w,y  Arranz, S., Cert, R., Perez-Jimenez, J., Cert, A., and Saura-Calixto, F., Food Chemistry, 110, 985–90, 2008.

k,q  Tokuşog

˘lu, O., Unal, M. K., and Yemis, F., Journal of Agricultural and Food Chemistry, 53, 5003–9, 2005.

k,q  Baur, J. A., and Sinclair, D. A., Nature Reviews Drug Discovery, 5, 493–506, 2006.

k  Hurst, W. J., Glinski, J. A., Miller, K. B., Apgar, J., Davey, M. H., and Stuart, D. A., Journal of Agricultural and Food Chemistry, 56, 8374–8, 2008.

o,u  Bellomo, M., and Fallico, B., Journal of Food Composition and Analysis, 20, 352–9, 2008.

o,p,q,r,t  Ballistreri, G., Arena, E., and Fallico, B., Molecules, 14, 4358–69, 2009.

p  Seeram, N. P., Zhang, Y., Henning, S. M., Lee, R., Niu, Y., Lin, G., and Heber, D., Journal of Agricultural and Food Chemistry, 54, 7036–40, 2006.

p,q,r,t  Gentile, C., Tesoriere, L., Butera, D., Fazzari, M., Monastero, M., Allegra, M., and Livrea, M. A., Journal of Agricultural and Food Chemistry, 55, 643–8, 2007.

q  Grippi, F., Crosta, L., Aiello, G., Tolomeo, M., Oliveri, F., Gebbia, N., and Curione, A., Food Chemistry, 107, 483–8, 2008.



Nut Bioactives



Table 9.2



188



Fruit and Cereal Bioactives: Sources, Chemistry, and Applications



the kernel in the bakery and confectionary industry. Nut skins and other by-products derived from the

processing of nuts have traditionally been used for livestock feed and as a raw material for energy production. But several studies have confirmed that they are an inexpensive, valuable source of natural antioxidants for nutraceutical and pharmaceutical applications (Wijeratne et al. 2006; Shahidi et al. 2007;

Yu et al. 2007).

The amount of dietary fiber is ~9 g/100 g of nuts, of which ~25% is soluble fiber. Soluble fibers reduce

total- and LDL-cholesterol concentrations and improve glycemic control (Anderson et al. 1994). There

is some evidence suggesting that even arginine, the second most abundant amino acid found in nut proteins, has a hypocholesterolemic effect (Kurowski and Carroll 1992).

Folic acid is also found in nuts. An adequate consumption of folic acid is important for ­preventing

carotid-artery stenosis (Selhub et al. 1995) and 100 g of nuts provides ~16% of the daily intake of

folic acid that is 400 μg/d. On average, one serving of nuts (~30 g) contains ~18% of the daily intake

for copper (Kris-Etherton et al. 1999) and therefore nuts can be a significant source of this essential

mineral (Allen et al. 1977). Copper plays a key role in hematopoiesis and its lack has been associated

with adverse changes in lipids, glucose tolerance and blood pressure (Klevay 1993). Almost all nuts

are good sources of magnesium, providing ~8–20% of the daily intake (400 mg) for this essential mineral in a serving. Low magnesium status can contribute to dysrhythmias, myocardial infarction, and

hypertension.

Phenolic compounds are considered nonnutrient, biologically active compounds (Shahidi and Naczk

1995). The functionality of these compounds is expressed through their action as an inhibitor or an activator for a large variety of enzyme systems, and as metal chelators and scavenger of free oxygen radicals

(Sanchez-Moreno et al. 1999; Russo et al. 2000; Garbisa et al. 2001). Oxygen free radicals are involved

in many pathological conditions such as cancer and chronic inflammation (Briviba and Sies 1994).

Epidemiologic studies (Hertog et al. 1993, 1995) have also shown that phenolic intake is ­significantly

and inversely associated with coronary heart disease (CHD) mortality.

Even vitamin E reduces CHD risk, but only in high doses (>100 IU/d). Nuts are a rich source of tocopherols, although the quantities obtained from typical nut consumption are far less than the amounts shown

to have beneficial effects on CHD. Nonetheless, nut consumption is still an effective means of increasing

vitamin E intake.

Phytosterols (~110 mg/100 g of nuts) have been shown to reduce blood cholesterol, as well as to

decrease the risk of certain types of cancer and enhance immune function (Ling and Jones 1995; Awad

and Fink 2000; Bouic 2001; Moreau et al. 2002; Ostlund 2004).

Other nutrients present in notable quantities in most nuts include thiamine, niacin, riboflavin, selenium, potassium, and iron.



Almond

Almond (Prunus dulcis) is one of the most popular nut crops. The United States is the first largest

producer of almonds in the world followed by Spain (Lopez-Ortiz et al. 2008). Large kernel and thin

or semihard shell thickness are among the desired nut characteristics in almond breeding. However,

nutritional characteristics might be affected by kernel weights. In addition, almond kernels should have

high contents of fatty acids, oil, and protein as nutritional values. Almonds can also be significant for

their antioxidant properties. It is an excellent source of tocopherols; moreover, the polyphenols located in

almond skin especially (Bolling et al. 2009) may also contribute to their health-promoting actions (Chen

et al. 2005; Milbury et al. 2006; Chen and Blumberg 2008).



Phenolics

The phenolics of almond are a mixture of flavonoids, phenolic acids, and tannins that contribute to their

antioxidant capacity in an additive or even synergistic manner (Milbury et al. 2006; Chen and Blumberg

2008; Garrido et al. 2008). Almond and its by-products derived from industrial processing, such as hull,

shell, and skin have been reported to have powerful free radical scavenging capacities (Pinelo et al.



Nut Bioactives



189



2004; Moure et al. 2007). Skin, while representing only approximately 4% of the total weight, contains

70–100% of the total phenolics present in the nut (Milbury et al. 2006).

Almonds contain a variety of flavonoids including flavanols (catechin and epicatechin), flavonols (kaempferol, isorhamnetin, and quercetin), flavanones (naringenin and eriodictyol), anthocyanins ­(cyanidin

and delphinidin), and proanthocyanidins (of both B- and A-type), as well as phenolic acids  (caffeic

acid, chlorogenic acid, ferulic acid, p-coumaric acid, p-hydroxybenzoic acid, protocatechuic acid, and

vanillic acid) and some alcohols and benzoic aldehydes (eugenol, p-hydroxybenzaldehyde, and protocatechuic aldeide; Amarowicz et al. 2005; Monagas et al. 2007; Chen and Blumberg 2008; Garrido

et al. 2008).

The most abundant group of almond skin phenolics are flavanols (~50%), followed by flavonol glycosides (~25%), and phenolic acids (~20%). The remaining phenolic compounds (flavonol aglycones,

flavanone glycosides, and aglycones) represent ~5% of total phenolic compounds (Monagas et al. 2007;

Garrido et al. 2008). The total content of almond skin phenolics varies from about 160 to 800 μg/g,

but this range is affected both by variety and processing (roasting and blanching). The mean total concentration of phenolic compounds has been found significantly higher in the skins of Spanish almonds

(~410 μg/g) with respect to American almonds (~270 μg/g). The content of phenolic compounds in the

American almonds has a high variability (Milbury et al. 2006; Garrido et al. 2008).

Table 9.3 reports the content (μg/g) of phenolic compounds of almond skins from Spain and the US

industrially processed (blanching + drying). The influence of industrial processing on almond skin polyphenols was studied by Garrido et al. (2008). In this study the phenolic composition of almond skins

obtained from different processes (blanching, blanching + drying, and roasting) has been evaluated.

The mean content of total polyphenols was higher (>twofold) in the roasted samples (28.4 mg/g) than in

the blanched samples (13.3 mg/g). The drying of the blanched samples produced an increase ( + 34%)

in the content of phenolic compounds of blanched samples. Moreover drying and roasting processes

induce an increase of antioxidant activity, they can produce a series of transformations that can affect

the concentration of some phenolic compounds (Piga et al. 2003), which could affect the antioxidant

capacity of almond skins. The ORAC values of almond skins are within 0.331–3.0 mmol Trolox/g range

(Monagas et al. 2007; Chen and Blumberg 2008; Garrido et al. 2008); these values are in the range found

for some by-products derived from the winery industry, such as grape skins and seeds (0.428 and 2.11

mmol Trolox/g, respectively), using the same extraction procedure (Friedrich et al. 2000; Monagas et al.

2005). This suggests that almond skins could be considered as a value-added by-product to be used in

the elaboration of antioxidant dietary ingredients.



Neutral Lipids

Triacylglycerols (TGs) represent the major lipid class in tree nut oils (>95%). Among nuts, almonds have

one of the lowest oil yield (on average ~50%), but its oil contains the highest TGs content (~98g/100 g oil;

Miraliakbari and Shahidi 2007).

Table 9.4 reports the TGs content (%) of almonds for different geographic origins. Five TGs are the

major ones: OLL, OLO, PLO, OOO, and POO (P = palmitic, O = oleic, S = stearic, L = linoleic), together

they represent ~80% of the total TGs content; four are minor: LLL, PLL, PLP, and SOO, representing

~20% of the total TGs content. POP and LnOO have also been found in small amounts (<1% and <3%,

respectively; Cherif et al. 2004). The TGs composition of almonds for different origins is qualitative

similar, but marked differences have been found in the TGs amount. The quantitative differences in the

TGs composition can be useful for distinguishing almonds of different cultivars (Martin-Carratala et al.

1999; Cherif et al. 2004).

The advantage of using TGs analysis compared to fatty acid profiles is that the stereospecific distribution of fatty acids on glycerol molecule is genetically controlled and, thus, the information content of

intact TGs is usually higher (Aparicio and Aparicio-Ruiz 2000; Ulberth and Buchgraber 2000).

The composition (%) of the major fatty acids (FAs) of some almond cultivars is reported in Table 9.5.

The major fatty acid in almonds is oleic (C 18:1), representing ~60–70% of the total FAs content, followed by linoleic (C 18:2), ~10–20% and palmitic 5–8% (García-López et al. 1996; Askin et al. 2007;

Miraliakbari and Shahidi (2007); little amounts (below 1%) of myristic (C 14:0) and linolenic acid



190



Fruit and Cereal Bioactives: Sources, Chemistry, and Applications



Table 9.3

Content (μg/g) of Phenolic Compounds in Almond Skins from Spain and the United States.

Compound

Hydroxybenzoic acids and aldehydes

p-hydroxybenzoic acid

Vanillic acid

Protocatechuic acid

Protocatechuic aldehyde

Hydroxycinnamic acids

trans-p-coumaric

Chlorogenic acid

Flavan-3-ols

( + )-catechin

(−)-epicatechin

B-type procyanidins

A-type procyanidins

Flavonol glycosides

Kaempferol-3-O-rutinoside

Kaempferol-3-O-glucoside

Kaempferol-3-O-galactoside

Isorhamnetin-3-O-rutinoside and glucoside

Isorhamnetin-3-O-galactoside

Quercetin-3-O-glucoside

Quercetin-3-O-galactoside

Quercetin-3-O-rutinoside

Flavanone glycosides

Naringenin-7-O-glucoside

Eriodictyol-7-O-glucoside

Flavonol aglycones

Kaempferol

Quercetin

Isorhamnetin

Dihydroflavonol aglycones

Dihydroquercetin

Dihydrokaempferol

Flavanone aglycones

Naringenin

Eriodictyol

Total



Spaina



United Statesb



6.9

14.5

32.0

20.1



3.1

6.0

9.7

9.9





10.6



0.7

12.1



90.1

36.6

77.7

28.9



37.5

18.7

36.2

11.7



12.8





43.2



2.4







29.2

5.0

0.1

79.1

5.7

1.6

7.9

2.6



22.1

1.6



9.8

1.1



1.7

1.8

4.9



2.0

1.7

4.0









9.0

1.1



2.8

2.4

413.0



4.2

2.7

274.8



Data reported by:

Monagas, M., Garrido, I., Lebron-Aguilar, R., Bartolome, B., and Gomez-Cordoves, C., J. Agric. Food Chem., 55,

8498–507, 2007.

a,bGarrido, I., Monagas, M., Gomez-Cordoves, C., and Bartolome, B., J. Food Sci., 73, C106–15, 2008.

bMilbury, P. E., Chen, C. Y., Dolnikowski, G. G., and Blumberg, J. B., J. Agric. Food Chem., 54, 5027–33, 2006.

a,b



(C 18:3) were also detected (Martin-Carratala et al. 1999; Kris-Etherton et al. 1999; Zacheo et al. 2000).

Askin et al. (2007), have observed that the content of the major FAs is influenced by kernel weight. The

contents of palmitic, stearic, and oleic acids, are positively correlated with kernel weight, contrary to the

linoleic acid content. In addition, shell thickness is negatively correlated with contents of palmitic and

stearic acids, but positively correlated with oleic acid.



191



Nut Bioactives

Table 9.4

Mean Content (%) of Major Triacylglycerols of Almonds of Different Geographic Origins

Triacylglycerols

LLL

OLL

PLL

OLO

PLO

PLP

OOO

POO

SOO



Italya



Spainb



Francec



Tunisiad



United Statese



Australiaf



1.21 ± 0.27

6.59 ± 0.33

1.08 ± 0.10

17.72 ± 1.28

5.37 ± 0.37

0.35 ± 0.02

52.06 ± 2.79

12.14 ± 0.72

3.47 ± 0.61



1.87 ± 0.37

10.95 ± 1.96

1.76 ± 0.29

22.65 ± 2.61

8.31 ± 1.13

0.45 ± 0.05

39.27 ± 5.64

11.88 ± 0.32

2.82 ± 0.50



1.78 ± 0.02

9.46 ± 0.05

1.53 ± 0.02

22.99 ± 0.13

7.27 ± 0.06

0.40 ± 0.01

41.68 ± 0.15

11.35 ± 0.11

3.53 ± 0.04



1.96 ± 0.02

11.34 ± 0.09

1.73 ± 0.02

25.68 ± 0.16

9.54 ± 0.09

0.44 ± 0.01

34.27 ± 0.17

12.61 ± 0.14

2.43 ± 0.05



2.51 ± 0.77

11.67 ± 3.70

1.83 ± 0.65

24.14 ± 3.18

8.28 ± 1.92

0.39 ± 0.03

37.71 ± 9.49

10.94 ± 0.48

2.54 ± 0.48



2.24 ± 0.03

12.68 ± 0.08

2.08 ± 0.02

26.25 ± 0.16

10.69 ± 0.05

0.49 ± 0.01

30.29 ± 0.21

12.28 ± 0.07

2.99 ± 0.05



Data reported by:  Martin-Carratala, M. L., Llorens-Jordá, C., Berenguer-Navarro, V., and Grané-Teruel, N., J. Agric. Food

Chem., 47, 3688–92, 1999.

Cultivars examined:  a  Genco, Tuono, Cristomorto; b  Malaguena, Peraleja, Atocha, Del Cid, Desmayo Largueta, Ramillete,

Marcona; c  Ferragnes; d  Achaak; e  Texas, Nonpareil, Titan, Wawona; f  Chellaston.



Table 9.5

Mean Content (%) of Major Fatty Acid of Almond Cultivars from Different Origins

Fatty Acids

Origin

American cultivarsa

Italian cultivarsa

Spanish cultivarsb

Tunisian cultivarsa

Turkish cultivarsc



Palmitic

C 16:0



Palmitoleic

C 16:1



Stearic

C 18:0



Oleic

C 18:1



Linoleic

C 18:2



5.76

5.03

7.42

7.50

7.50



0.369

0.401

0.632

0.368

0.724



1.72

1.77

2.03

1.70

1.83



62.75

64.53

68.46

73.10

70.84



20.42

11.87

20.45

19.50

18.49



Data reported by:

Garcia-Lopez, C., Grané-Teruel, N., Berenguer-Navarro, V., Garcia, J., and Martin Carratalá,

M. L., Journal of Agricultural and Food Chemistry, 44, 1751–5, 1996.

b

Miraliakbari, H., and Shahidi, F., Journal of Food Lipids, 15, 81–96, 2007.

cAskin, M., Balta, M., Tekintas, F., Kazankaya, A., and Balta, F., Journal of Food Composition

and Analysis, 20, 7–12, 2007.

a,b



Polar Lipids

Among polar lipids phosphatidylserine, phosphatidylinositol, and phosphatidylcholine are present at

0.13, 0.09, and 0.14 g/100 g of almond oil, respectively. Sphingolipids are also present (0.37 g/100 g of

oil; Miraliakbari and Shahidi 2007, 2008).



Phytosterols and Tocols

Almond oil contains between 2.2 and 2.8 g/kg of phytosterols, mainly β-sitosterol (~2.0 g/kg), with

trace amounts of stigmasterol, Δ5-avenasterol, and campesterol (Maguire et al. 2004; Miraliakbari and

Shahidi 2007).

Almonds stand out for being one of the nuts with the highest α-tocopherol content. It ranges from about

8.0 to 25.0 mg/100 g of oil (Kornsteiner et al. 2006; Miraliakbari and Shahidi 2007; Lopez-Ortiz et al.

2008). Almond oil contains smaller amounts of β + γ-tocopherol, ranging from 0.1 to 3–0 mg/100 g of oil,

and δ-tocopherol present in traces. Therefore, almonds are a dietary sources of α-, β-, and γ-tocopherol

and can contribute to a balanced intake of vitamin E. This explains why almonds have been included in



192



Fruit and Cereal Bioactives: Sources, Chemistry, and Applications



the recommendations of The Dietary Guidelines for Americans (USDA 2005) in the context of enhancing

the intake of this vitamin.



Hazelnut

The hazelnut (Corylus avellana L.) belongs to the Betulacee family and is a popular tree nut worldwide,

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

world’s largest producer of hazelnuts contributing ~74% to the total global production, followed by Italy

(~16%), the United States (~4%), and Spain (~3%; Alasalvar et al. 2009a). Besides its economic value,

hazelnuts provide a unique and distinctive flavor as an ingredient in a variety of food products for taste;

active components such as free amino acids, sugars, and organic acids improve the sensory characteristics of products. Moreover, hazelnuts play a major role in human nutrition and health for its special composition of fat, which are highly rich in monounsaturated fatty acids, protein, carbohydrate, dietary fiber,

vitamins, minerals, phytosterols, squalene, and antioxidant phenolics (Alphan et al. 1997; Richardson

1997; Ackurt et al. 1999; Yurttas et al. 2000).



Phenolics

Hazelnuts have a hard, smooth shell. The seed is covered by a dark brown pellicular pericarp (skin or testa),

which is typically removed before consumption after roasting of the kernel. The hazelnut native phenolics

are almost exclusively located in the perisperm of the seed (Contini et al. 2008). Recent studies (Shahidi et

al. 2007; Alasalvar et al. 2009b) have established that hazelnut wastes, especially the skin and hard shell,

are a reliable source of natural antioxidants. Hazelnut skin shows superior antioxidative efficacy and higher

phenolic content, compared to the hazelnut kernel and other by-products (Table 9.6). By comparison with

almonds and peanut skins, the content obtained from the hazelnut has the highest level of phenolics.

Five phenolic acids have been identified and quantified (both free and esterified forms) by Alasalvar

et al. (2006) and Shahidi et al. (2007) in the hazelnut kernel and by-products. One of which is a hydroxylated derivative of benzoic acid (gallic acid) and four of which were cinnaminc acid derivatives (caffeic

acid, p-coumaric acid, ferulic acid, and sinapic acid). The p-coumaric acid is the most abundant phenolic

acid in the hazelnut kernel with a mean content of ~2.5 μg/g. Whereas gallic acid is the most abundant

with a mean content of ~39.1 and ~ 81.0 μg/g of skin and hard shell, respectively, implying the presence

and the dominance of tannins, ranging nearly 60–65% of the total phenols (Contini et al. 2008). Tannins

are much more powerful antioxidants than simple monomeric phenols, and may have unique roles in the

human digestive metabolism as both savers of other biological antioxidants and protectors of nutrients



Table 9.6

Yield, Content of Phenolics and TAA in Extracts of Hazelnut Kernel and Hazelnut By-Products

Extract

Hazelnut kernel (with skin)

Hazelnut skin

Hazelnut hard shell

Hazelnut green leafy cover

Hazelnut tree leaf



Yielda



Phenolicsb



TAAc



2.26 ± 1.11 e

10.28 ± 1.02 f

2.53 ± 0.33 e

3.59 ± 0.85 e

1.64 ± 1.87 e



13.7 ± 0.5 e

577.7 ± 1.1 f

214.1 ± 0.3 g

127.3 ± 0.7 h

134.7 ± 1.0 i



29.0 ± 3.5 e

132.0 ± 4.0 f

120.0 ± 3.0 g

117.0 ± 2.5 g

148.0 ± 2.1 h



Source:Data reported by Shahidi, F., Alasalvar, C., and Liyana-Pathirana, C. M., J. Agric. Food Chem., 55, 1212–20,

2007.

Notes:Data are expressed as means ± SD (n = 3) on an extract. Means ± SD followed by the same letter, within a

column, are not significantly different (p >.05).

a  Expressed as grams per 100 g of defatted samples. b  Expressed as milligrams of catechin equivalents per gram of

extract. c  Expressed as micromoles of trolox equivalents per gram of extract.



193



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(lipid, proteins, and carbohydrates) from oxidative damages (Chung et al. 1998; Hagerman et al. 1998).

By comparison with almonds and walnuts, hazelnuts have the highest content of condensed tannins

(proanthocyanidins; Karamac et al. 2007).

Yurttas et al. (2000) have identified six phenolic aglycones in Turkish and American hazelnuts: gallic

acid, p-hydroxybenzoic acid, epicatechin and/or caffeic acid, sinapic acid, and quercetin. Protocatechuic

acid has been reported to be the predominate phenolic acid in the skin of an American hazelnut (0.36 μg/g)

by Senter et al. (1983). These differences could be ascribed to varieties and extraction procedures that

exerted a great influence on the concentration and variability of the phenolic acids present. The phenolic

content of hazelnuts could be used as an important criteria in evaluating hazelnut quality (Contini et al.

2008; Alasalvar et al. 2009b).



Neutral Lipids

The lipid fraction is the major component of hazelnuts (~60%), and is composed of nonpolar (98.8%)

and polar (1.2%) constituents (Amaral et al. 2006a; Alasalvar et al. 2009a). Triacylglycerols (TGs) are

the major nonpolar lipid class, representing nearly 100% of the total nonpolar lipids in hazelnut oil

(Alasalvar et al. 2003). The TGs are increasingly used in the food industry as a tool to assess the quality

and authenticity of vegetable oils (Aparicio and Aparicio-Ruiz 2000), particularly the adulteration of

olive oil with hazelnut oil (Parcerisa et al. 2000).

Amaral et al. (2006a) identified and quantified 11 TGs for 19 cultivars coming from six different

countries (United States, Italy, Spain, France, Germany, and England) during three consecutive years;

12 TGs (including one unknown) have been determined by Alasalvar et al. (2009a) in hazelnut oils of

five native hazelnut varieties from Turkey (Table 9.7). The predominant TGs are OOO (65.3–70.8%),

followed by OOL (13.6–15.4%), POO (8.9–11.4%), SOO (3.5–3.7%), and OLL (2.0%). They account

for more than 95% of total TGs content; the remaining seven TGs contribute only about 2% to the

total amount.

TGs are usually determined by HPLC/ELSD, studies conducted with different RI detectors (Parcerisa

et al. 1995) and MS detector (Parcerisa et al. 2000) have rendered higher values for LLL, OLL, POL,

and PPO and much lower values for OOO. Trace amounts of PPP in hazelnut oil have been reported

by Parcerisa et al. (1995). In contrast, Ayorinde et al. (1999) have analyzed hazelnut oil using MALDITOF-MS and pointed out that minor quantities of SLL and SOL could be ascribed to the coelution with

Table 9.7

Mean Triacylglycerol Content (Relative %) of Hazelnut Oil

Triacylglycerols

LLL

OLL

PLL

OOL

POL

PPL

OOO

POO

PPO

Unknown

SOO

PSO



Amaral et al. (2006a)a



Alasalvar et al. (2009a)b



0.23 ± 0.06

2.00 ± 0.27

0.09 ± 0.03

15.36 ± 1.23

1.57 ± 0.21

0.03 ± 0.01

65.32 ± 1.22

11.43 ± 0.56



0.25 ± 0.28

2.02 ± 1.99

0.05 ± 0.07

13.56 ± 5.28

0.77 ± 0.49

0.01 ± 0.01

70.82 ± 6.08

8.89 ± 1.93



0.10 ± 0.02





0.03 ± 0.01

0.02 ± 0.02

3.54 ± 1.51

0.05 ± 0.04



3.73 ± 0.76

0.13 ± 0.03



Cultivars and varieties examined:  a  Butler, Campanica, Cosford, Couplat, Daviana,

Ennis, Fertille de Coutard, Grossal, Gunslebert, Lansing, Longa d’Espanha, Merveille

de Bollwiller, Morell, Negreta, Pauetet, Round du Piemont, Santa Maria de Jesus,

Segorbe, Tonda de Giffoni; b  Tombul, Yassi Badem, Sivri, Karafindik, Ham.



194



Fruit and Cereal Bioactives: Sources, Chemistry, and Applications

Table 9.8

Percentages of Fatty Acids of Lipid Fractions Extracted from Hazelnuts of Different Origins

Fatty Acids (%)

Origin

Italy



Spain



Turkey

United States



Cultivar

T. Romanaa

T.g.d.l.b

Mortarella

T. Giffonic

Casina

Segorbe

Negret

Ribet

Tomboul

Imperial

Barcelona

Daviana

Montebello

Butler

Ennis

Halls giant

Willamette



C16:0



C16:1



C18:0



C18:1



C18:2



C18:3



5.78

6.04

4.98

5.38

5.70

4.66

5.04

5.52

5.48

5.07

5.20

5.19

5.10

5.77

5.41

4.72

5.20



0.22

0.30

0.15

0.19

0.21

0.17

0.19

0.19

0.21

0.18

0.17

0.19

0.21

0.24

0.23

0.17

0.18



2.50

2.81

2.72

2.86

2.96

2.58

2.49

2.68

2.04

3.36

1.93

2.29

3.34

2.68

1.38

2.19

2.43



82.55

82.29

78.90

82.83

78.58

79.85

79.06

76.45

74.13

76.42

78.72

79.19

80.31

79.55

77.08

79.13

80.76



8.59

8.17

12.83

8.37

12.19

12.34

12.82

14.69

17.78

14.52

13.58

12.75

10.46

11.26

15.55

13.23

11.04



0.10

0.10

0.11

0.10

0.10

0.12

0.13

0.15

0.11

0.13

0.14

0.11

0.17

0.11

0.11

0.14

0.11



Source: Data reported by Parcerisa, J., Richardson, D., Rafecas, M., Codony, R., and Boatella, J., J.

Chromatogr.,º A, 805, 259–68, 1998.

Note: Data are means of triplicate results.

a Tonda Romana; b  Tonda gentile delle langhe; c  Tonda giffoni.



OLL and OOO. Therefore, the type of detector used has a significant influence on TGs profile (Alasalvar

et al. 2009a).

Amaral et al. (2006b) have also studied the effect of roasting on hazelnut lipids. They observed a

decrease of TGs containing linoleic acid moieties and an increase of TGs containing oleic, palmitic, and

stearic acids, with the increase of temperature and roasting time. In general, as roasting time increased,

losses of TGs species are more pronounced in those containing more than four double bonds, probably

because the rate of fatty acids breakdown is related to the increasing rate of oxidation with increasing

unsaturation (Yoshida et al. 2003).

Among nuts, hazelnuts have the highest oleic acid content (~80%; Miraliakbari and Shahidi 2007).

The other major fatty acids are linoleic (~13%), palmitic (~5%), and stearic (~2%; Parcerisa et al. 1998;

Koksal et al. 2006). The fatty acid composition of the hazelnut is influenced by variety and geographical origin (Table 9.8). It has been reported that the ratio of oleic to linoleic acid varies among hazelnut

cultivars, and that their contents are inversely related (Parcerisa et al. 1995; Amaral et al. 2006c). The

ratio oleic to linoleic, for cultivars reported in Table 9.8, varies from 4.1 to 9.8; this can really point to

different behaviors for the several cultivars there were studied.

In general, with roasting (Amaral et al. 2006a) and during fruit development (Seyhan et al. 2007),

the relative levels of monounsaturated fatty acids increase while that of the polyunsaturated fatty acids

decrease.



Polar Lipids

Hazelnut oil components have been separated and quantified using column chromatography by Parcerisa

et al. (1997), revealing that oil contains less than 0.2% of phospholipids (phosphotidylcholine and phosphatidylinositol). The lipid class composition of hazelnut oil has also been studied using Iatroscan by

Alasalvar et al. (2003), revealing 1.2% of polar lipids in oil. Among polar lipids, phosphotidylcholine,



195



Nut Bioactives

Table 9.9

Mean Tocopherol and Tocotrienol Composition of Hazelnut Oils (mg/100 g)

Tocols



Crews et al. (2005)a



α-Tocopherol

β-Tocopherol

γ-Tocopherol

δ-Tocopherol

α-Tocotrienol

β-Tocotrienol

γ-Tocotrienol

Total



35.40

1.10

2.10









38.60



Country of origin of hazelnuts: 



a 



Amaral et al. (2006b)b



Alasalvar et al. (2009a)c



24.47

0.84

0.97

0.01

0.19

0.03

0.12

26.63



30.50

1.07

10.15

0.43

0.17

0.09

0.22

42.63



Italy; b  Portugal; c  Turkey.



phosphotidylethanolamine, and phosphatidylinositol were present at 56.4, 30.8, and 11.7%, respectively.

Traces of phosphatidic acid have also been detected (Miraliakbari and Shahidi 2008).



Phytosterols and Tocols

Total sterols content varies from about 120 to 250 mg/100 g of hazelnut oil (Crews et al. 2005; Amaral

et al. 2006c; Alasalvar et al. 2009a). There are differences among cultivars, though β-sitosterol is the

major sterol in all cultivars (84–219 mg/100 g oil), followed by Δ5-avenasterol (2.2–18.2 mg/100 g oil),

and campesterol (5.1–16.4 mg/100 g oil). Besides these compounds, cholesterol, stigmasterol, clerosterol,

Δ7-avenasterol, Δ7-stigmastenol, cholestanol, brassicasterol, 24-methylenecholesterol, campestanol,

Δ7-campesterol, Δ5,23-stigmastadienol, sitostanol, and Δ5,24-stigmastadienol have also been found, but they

contribute less than 4% to the total (Crews et al. 2005; Amaral et al. 2006c; Alasalvar et al. 2009a).

Hazelnut varieties are an excellent source of tocols ranging from 11 to 45 mg/100 g oil (Crews et al.

2005; Amaral et al. 2006b; Alasalvar et al. 2009a). In the majority of hazelnuts, seven tocol isoforms

have been detected (α-, β-, γ-, and δ-tocopherols and α-, β-, and γ-tocotrienols; Table 9.9).

The major tocopherol present is α-tocopherol, followed by γ- and β-tocopherol. Hazelnut oil has been

reported to have the highest α-tocopherol level among tree nut oils (Kornsteiner et al. 2006). Differences

in tocols composition could be ascribed to the geographical origin of hazelnuts (Crews et al. 2005), and

the type of detector (UV, FL, or FL/DAD) and methodology used that exert a significant effect on the

tocol profiles (Alasalvar et al., 2009a). Roasting of hazelnuts causes a modest decrease of vitamin E

homologues (maximum 10%; Amaral et al. 2006b).



Peanut

Peanut or groundnut (Arachis hypogaea L.) is universally popular and is used as a snack food or as

an ingredient in the manufacture of a variety of food products such as peanut butter and peanut brittle

(Venkatachalam and Sathe 2006). Peanuts may be consumed raw, roasted, pureed, or in a variety of

other processed forms, and constitute a multimillion-dollar crop worldwide (Yu et al. 2005) with numerous potential dietary benefits. Recently several peanut cultivars were developed with elevated concentrations of the monounsaturated oleic acid, in relation to other highly oxidizable polyunsaturated fatty

acids. The high oleic trait provides peanuts with potentially greater health benefits and serves to prolong

shelf-life characteristics. Numerous phytochemical compounds with potential antioxidant capacity are

present in peanuts including polyphenolics (Talcott et al. 2005), tocopherols (Hashim et al. 1993), and

proteins (Bland and Lax 2000). Moreover, the peanut is a good source of folate and resveratrol. Regular

peanut consumption lowers serum TG and increases dietary folate intake, thereby lowering plasma

homocysteine concentration. Higher peanut butter consumption was associated with a decreased risk of

type 2 diabetes in women (Yang et al. 2009).



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Fruit and Cereal Bioactives: Sources, Chemistry, and Applications



Phenolics

Numerous phenolics have been identified in peanut skins, such as phenolic acids, flavonoids and stilbenes (Yu et al. 2005; Francisco and Resurreccion 2009). Yu et al. (2005) identified three classes of

phenolic compounds in raw peanut skins: (1) phenolic acids including chlorogenic acid, caffeic acid, and

ferulic acid; (2) flavonoids including epigallocatechin, epicatechin, catechin gallate, epicatechin gallate;

and (3) stilbenes (resveratrol). Caffeic acid, chlorogenic acid, ellagic acid, resveratrol, and its glycoside

were identified but not quantified, due to a very low concentration and peaks were suppressed by major

procyanidins (Yu et al. 2006). By weight, 17% of peanut skins are procyanidins consisting of low and

high molecular weight oligomers (Karchesy and Hemingway 1986).

Table 9.10 shows the mean values of peanut skin phenolics of the major cultivar groups (Runner,

Virginia, and Spanish). Ethyl protocatechuate, a protocatechuic acid ethyl ester, also has been identified in Spanish peanut skins (Huang et al. 2003; Yen et al. 2005), but no amount was provided

by the authors. Caffeic acid has been detected only in Spanish skins. This compound was also

detected by Yu et al. (2005) in peanut skins (peanut type not specified). The p-coumaric acid is

predominantly present in peanut kernels (~60 μg/g; Talcott et al. 2005; Duncan et al. 2006) with

respect to skins (~13 μg/g). Monomeric and oligomeric flavan-3-ol has been detected in peanuts.

Monomeric (+)-catechin is more abundant than (−)-epicatechin in peanut skins (849 and 196 μg of

catechin equivalents/g of peanut skin, respectively; Monagas et al. 2009). Total monomers account

for only 19% in peanut skins, while procyanidins (both A- and B-type, including B-type dimers,

and A-type dimers, trimers, and tetramers) represent ~80% of total flavan-3-ol content (~4600 μg

of catechin equivalents/g of peanut skin). Peanut skins are characterized by a high proportion of

A-type procyanindins, total dimers + trimers accounting for 40% and tetramers for 37% of the

total monomers + oligomers content (Yu et al. 2006; Monagas et al. 2009). Moreover the presence

of isoflavones (~90 μg/100 g of wet weight), mainly genistein, glycitein, and biochanin A, as well

as lignans (~75 μg/100 g of wet weight; secoisolariciresinol) has been revealed in fresh, dry, and

roasted peanuts (Kuhnle et al. 2008).

Among nuts, only peanuts and pistachios are sources of stilbenes (Baur and Sinclair 2006). The

trans-resveratrol is the main resveratrol isomer that occur in peanuts, with a mean content of ~8.5 μg/g

(skin + kernel; Tokuşoğlu et al. 2005; Francisco and Resurreccion 2009). Tokuşoğlu et al. (2005), after

exposure of peanuts to UV light, have observed the conversion of trans-resveratrol into cis-form with a

range value of 0.04–0.50 μg/g. Roasted peanuts have a minor amount of resveratrol (~four-fold less) than

raw peanuts (Sanders et al. 2000; Hurst et al. 2008). Even in pistachios, the thermal process induces a

profound loss (>80%) of this compound (Ballistreri et al. 2009).



Table 9.10

Mean Values of Peanut Skins Phenolics of Different Cultivar Groups

Compound

Protocatechuic acid

Caffeic acid

p-Coumaric acid

Epigallocatechin

Catechin

Procyanidin B2

Epicatechin

Quercetin

Resveratrol



Runner



Virginia



Spanish



7.62 ± 1.34

nd



34.03 ± 1.95

nd



23.35 ± 0.91

440.05 ± 16.70

74.35 ± 13.14



4.98 ± 0.63

1275.92 ± 77.10

535.03  ± 41.72



15.45 ± 0.87

3.49 ± 0.36

12.31 ± 1.42

1274.72 ± 67.50

448.30 ± 36.47



20.67 ± 5.63

60.06 ± 11.44

20.14 ± 1.49

4.30 ± 0.10



17.69 ± 1.61

144.75  ± 1.42

22.88 ± 2.92

3.66 ± 0.44



107.00 ± 18.99

238.55 ± 9.20

27.99 ± 2.10

15.04 ± 1.57



Source: Data reported by Francisco, M. L. L. and Resurreccion, A. V. A., Food Chem., 117, 356–63, 2009.

Note: Data are expressed as μg/g of dry skin.

nd = not detected.



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