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CHAPTER 10

Antioxidants in PecanNut Cultivars [Caryaillinoinensis (Wangenh.)K. Koch]

Ana G. Ortiz-Quezada, Leonardo Lombardini, Luis Cisneros-ZevallosDepartment of Horticultural Sciences, Fruit and Vegetable Improvement Center,Texas A&M University, College Station, Texas, USA

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C

CHAPTER OUTLINE

881

Introduction 881Botanical Description 882Historical Cultivation andUsage 882Present-Day Cultivation andUsage 883

uts & Seeds in Health and Disease Prevention. DOI: 10.1016/B978-0-12-375688-6.101

opyright � 2011 Elsevier Inc. All rights reserved.

Applications to Health Promotionand Disease Prevention 883Adverse Effects and Reactions(Allergies and Toxicity) 887Summary Points 888References 889

LIST OF ABBREVIATIONS

AC, antioxidant capacityCAE, chlorogenic acid equivalentsCE, catechin equivalentsCT, condensed tanninsDPPH, 2, 2-diphenyl-1-picrylhydrazylGAE, gallic acid equivalentsHPLC-MS, high performance liquid chromatography-mass spectrometryORAC, oxygen radical absorbance capacity assayPDA, photodiode arrayTE, Trolox equivalentsTP, total phenolics

INTRODUCTIONPecan [Carya illinoinensis (Wangenh.) K. Koch] is the most valuable nut tree native to NorthAmerica. Over 1000 different pecan varieties have been described, although 90% of cultivated

acreage is represented by only a few dozen varieties. Pecan kernels contain about 70% lipids,

04-5

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PART 2Effects of Specific Nuts and Seeds

namely oleic (over 60%), linoleic, palmitic, stearic, and linolenic acids. Pecans’ antioxidantcapacity, considered one of the highest among nut crops, comes from the non-lipid portion,

and is cultivar-dependent. Defatted pecan kernels contain mainly condensed and hydrolyzable

tannins. After a consecutive base/acid hydrolysis, phenolics released are mainly gallic acid,catechin, epicatechin, ellagic acid, and ellagic acid derivatives.

BOTANICAL DESCRIPTIONPecan has been known for centuries for its edible nuts. The species is distributed over a broad

geographic area, encompassing tremendous climatic variation. The native range of pecanextends for about 26� in latitude, from northern Iowa (lat. 42�200N) to Oaxaca in Mexico (lat.

16�300N) (Figure 104.1) (Thompson & Grauke, 1991). Pecan trees grow abundantly along

the Mississippi River, the rivers of central and eastern Oklahoma, and on the Edwards plateauof Texas. The long tap roots and the frequent presence of shallow water tables allow

native trees to survive the severe hot and dry summers that characterize the area of native

distribution. However, the deeper the water source, the greater is the energy expended toobtain it, which leads to diversion of valuable energy from the developing leaves and nuts.

HISTORICAL CULTIVATION AND USAGEThe pecan is the only nut crop native to the North American continent that has significant

commercial importance. All other major nut crops have been imported from other areas of the

world. The term “pecan” derives from the word pacane, which is the Algonquin word for “nutthat must be cracked with a stone” (Brison, 1974). Spanish explorers in the 16th century came

to refer to them as “pacanos,” or sometime simply nueces (nuts) or nogales, due to their

resemblance to the fruit of the Persian walnut, Juglans regia L. The botanical name of thespecies was chosen because Carya is the ancient Greek name for walnut, and because one of the

earliest indications of pecan use by Native Americans goes back to archaeological evidence

found in present-day Illinois, dating from 9000 years ago. The archeological findings,combined with the descriptions made by the first Europeans during the 16th century, show

that pecans were an essential ingredient for most Native American tribes of the southern part of

what is now the United States. There is also evidence that some migration patterns traced the

FIGURE 104.1Native distribution of pecan. Native distribution of pecans includes south central states of the United States and different

regions of Mexico (from Thompson & Grauke, 1991).

CHAPTER 104Pecan Nut Cultivars and Antioxidants

883

pecan season along alluvial plains and other fertile areas of modern Mexico and the UnitedStates. Pecan trees were revered by Native Americans not only as a food source. Members of the

Ojibwa tribe utilized the wood of pecan and other hickories to make bows and finish off

baskets. Additionally, pecan paste and oil, as well as leaf or bark infusions, were used by othertribes as abatement for several illnesses, such as intestinal worms, constipation, skin eruptions,

rheumatism, gastrointestinal problems, and colds, or as facilitator in abortions. Despite theimportance of pecans for Native Americans, it is almost certain that the Natives only relied on

large groves of uncultivated or wild pecan trees, without making use of any widespread

horticulture techniques to propagate and cultivate these trees. It was not until the mid-1800sthat farmers began to realize the commercial value, plus the culinary importance, of pecans,

and started developing horticultural techniques to maximize production. In 1847, it took

a slave gardener (remembered only by his first name of Antoine) at the Oak Alley Plantation,Louisiana, to develop a technique to graft an improved variety (“scion”) onto a different tree

(“rootstock”). This episode marked the beginning of the modern pecan industry, because it

allowed mass propagation of those trees which showed desirable characteristics, such as highkernel percentage (highmeat content), resistance to diseases and insects, and reduced alternate

bearing characteristics (Worley, 1994).

PRESENT-DAY CULTIVATION AND USAGEA little bit more than a century and a half after Antoine’s breakthrough discovery, pecan is

today an economically important tree-nut crop for the United States and Mexico, with an

annual economic value of about $300 million for the United States alone. There are over 1000different pecan varieties that have been described, classified as either native or improved

varieties.

Native trees or seedlings are those that have not been grafted with improved varieties. Thelatter are those that have been genetically altered through selection, and controlled, and are

usually associated with more intensive horticultural practices, but sell at a premium price

compared with native varieties because they usually produce larger kernels and are perceived ashigher quality products. The majority of the improved acreage in the United States comprises

only four varieties (Stuart, Western Schley, Desirable, and Wichita), and about 90% of the

acreage comprises 33 varieties. In recent years, other varieties, such as Pawnee, have beenextensively planted in newly established orchards; however, official data are not available

(T.E. Thompson, personal communication).

A survey conducted recently in Texas reported that most pecan consumers prefer to purchase

shelled pecans to use them as ingredient in food dishes (Figure 104.2) (Lombardini et al.,

2008). The United States and Mexico are the greatest producers of this nut. In the UnitedStates, Georgia, New Mexico, and Texas are the major producers for improved varieties,

whereas fruits from native and seedlings trees are mainly from Oklahoma and Texas

(Table 104.1).

APPLICATIONS TO HEALTH PROMOTION ANDDISEASE PREVENTIONPecan kernels are sources of protein, dietary fiber, vitamins, minerals, and many other

bioactive substances, also called phytochemicals, which are known to provide health benefits.According to the US Department of Agriculture Nutrient Database (USDA, 2009), pecan

kernels contain 72% lipids, 14% carbohydrates, 9% protein, 3.5% water, and 1.5% ash.

Regarding the vitamins and minerals, pecan kernels are a good source of vitamins A and E, theB vitamins, folic acid, calcium, magnesium, potassium, and zinc.

Clinical studies with human subjects have shown that consuming pecans and other tree nuts

may play an important role in reducing the risk of heart disease by improving the serum lipid

0 10 20 30 40 50 60 70 80 90 100Frequency (% respondents)

0 10 20 30 40 50 60 70 80 90 100Frequency (% respondents)

Ingredients in food dishes

Raw snack

Semiprepared snack (roasted, salted, spiced)

Other

Other

I do not use pecans

I do not buy pecans

Meal

Shelled (halves)

Pieces

In-shell

Cracked shell

Prepared (chocolate-covered, roasted, spiced)

FIGURE 104.2Purchasing behavior (top) and consumingpreference (bottom) in regards to pecan, asemerged from a survey conducted in Texas.Pecan halves and pieces are preferentially

purchased by consumers and used mainly as

ingredients in food dishes and snacks (from

Lombardini et al., 2008).

PART 2Effects of Specific Nuts and Seeds

884

profile. These benefits are mainly due to their high unsaturated fatty acid content (Rajaramet al., 2001). Little information is available about the phytochemicals contained in the non-

fatty portion of pecan kernels, which is believed to protect the oil. Around 97% of the total

antioxidant capacity of pecans, measured by oxygen radical absorbance capacity assay(ORAC), comes from the hydrophilic portion. Wu et al. (2004) screened pecan kernels from

unidentified cultivar(s), and nine other tree nuts, and found that pecans had the highest

antioxidant capacity by ORAC (179.40 mmol TE/g) and total content of phenolics (20.16mgof GAE/g). In another study, 98 common foods were screened for their proanthocyanidin

content, or condensed tannin. It was found that within the nut group, pecans from uniden-

tified cultivar(s) had the second highest content (494mg/100 g fresh weight), after hazelnuts(500mg/100 g fresh weight) (Gu et al., 2004).

Recently, the phytochemical constituents in defatted pecan kernels were investigated (Villar-real-Lozoya et al., 2007) in six cultivars (Desirable, Kanza, Kiowa, Nacono, Pawnee, and

Shawnee) chosen for their commercial relevance. Results showed significant differences due to

cultivar and, to a lesser extent, to orchard location. The study also revealed that a large portionof the antioxidant capacity was attributable to the total phenolics (TP), and especially to the

condensed tannins (CT), by a ratio ranging from 0.31 to 0.56 CT/TP (Figure 104.3). Total

phenolics measured by Folin-Ciocalteau spectrophotometric assay as chlorogenic acidequivalents ranged from 62 to 102mg CAE/g defatted pecan. Condensed tannins were

measured with the vanillin assay as catechin equivalents per gram defatted pecan, and their

values were between 25 and 47mg CE/g defatted pecan. After base and acid hydrolysis of anaqueous acetone extract of the defatted matrix, catechin, epicatechin, gallic acid, ellagic acid,

TABLE 104.1 Utilized Pecan Production (3 1000 lb) in the United States by Varietyand State, 2004e2008

Utilized Production (In-Shell Basis)

Improved Varieties 2004 2005 2006 2007 2008

AL 1,000 3,200 5,400 10,000 7,400AZ 14,000 22,000 14,000 23,000 17,500AR 1,000 1,100 1,150 1,500 1,000CA 3,500 3,900 3,400 4,400 3,750FL 400 300 200 1,700 1,400GA 42,000 72,000 36,000 135,000 66,000LA 2,500 1,000 3,500 3,000 1,000MS 700 800 2,000 2,200 900MO 200 160 2 110NM 39,000 65,000 47,000 74,000 43,000NC 70 1,650 420 160 600OK 6,000 6,000 5,000 3,000 1,000SC 800 1,500 900 1,500 3,000TX 28,000 50,000 33,000 44,000 20,000US 138,970 228,650 152,130 303,462 166,660

Native and Seedlings 2004 2005 2006 2007 2008

AL 100 800 600 2,000 600AR 700 1,200 1,050 800 500FL 100 700 300 200 300GA 3,000 8,000 6,000 15,000 4,000KS 1,800 3,200 2,000 500 1,900LA 6,500 4,000 17,500 11,000 4,000MS 300 200 500 800 600MO 2,400 940 3 830NC 30 350 80 40 100OK 22,000 15,000 12,000 27,000 4,000SC 300 700 200 500 400TX 12,000 15,000 14,000 26,000 10,000US 46,830 51,550 55,170 83,843 27,230

Georgia, New Mexico, and Texas are the leading states in pecan production for improved varieties, whereas Texas, Oklahoma,

Louisiana, and Georgia lead native and seedling production.

Source: USDA Economics, Statistics and Market Information System (http://usda.mannlib.cornell.edu).

CHAPTER 104Pecan Nut Cultivars and Antioxidants

885

and an ellagic acid derivative were identified (Villarreal-Lozoya et al., 2007). The compoundsfound in greater concentrations were gallic acid (651e1300 mg/g defatted pecan) and ellagic

acid (2505e4732 mg/g defatted pecan), but no significant differences were detected among

cultivars. ORAC values ranged from 373 to 817 mmol TE/g defatted pecan, and strong corre-lations were found between antioxidant capacity and TP, as well as with condensed tannins

(Villarreal-Lozoya et al., 2007). The range values obtained for CT/TP and ACORAC/TP imply

that proportions of condensed and hydrolyzable tannins differ for each cultivar, and thisproportion determines the specific antioxidant activity of the phenolics present in each cultivar

(Villarreal-Lozoya et al., 2007).

The main fatty acids found in the lipid fraction of pecan kernels were oleic (over 60%), linoleic,

palmitic, stearic, and linolenic. Pecans are considered to have high amounts of g-tocopherol,

along with walnuts, while almonds and hazelnuts are rich in a-tocopherol. Tocopherol contentin pecans varies by cultivar, and other factors such as genetics, environment, maturity, and

storage conditions. Tocopherols (vitamin E) are fat-soluble antioxidants naturally present in

vegetable oils, such as those extracted from olive, almond, and hazelnut. Gamma-tocopherolvalues for the six pecan cultivars ranged from 72 to 135 mg g-tocopherol/g oil.

FIGURE 104.3Positive correlation between total phenolic content andcondensed tannins from defatted pecan kernels. Condensedtannins are the major components of the total phenolics present

in defatted pecan kernels.

PART 2Effects of Specific Nuts and Seeds

886

Nut shells were also analyzed for total phenolic content and condensed tannins for the six

cultivars. Interestingly, their TP and CT values were 6 and 18 times higher than the ones foundin the defatted kernels. It was concluded that phenolics from shells are mainly formed by

condensed tannins (TPzCT), and their presence may affect the content of kernel phenolics.It has been suggested that tannins leach from shells to kernels during soaking and precon-

ditioning during commercial processing. Another possible source of leaching could be

cold-room storage prior to cracking and shelling, due to water condensation inside the nuts asa result of small temperature fluctuations. Shells represent a large by-product of the pecan

industry, with the shell percentage in pecan nuts varying from 40% to 50% (Worley, 1994).

Processing plants have found only a limited market for pecan shells, with minimal profit.Thus, the high antioxidant capacity observed shows a potential alternative use of pecan shells

as a novel source of antioxidants.

The presence of high contents of phenolic compounds, tocopherol, and mononounsaturatedfatty acid suggest several health benefits. Phenolic compounds have been reported to protect

against atherosclerosis, hypertension, cardiovascular diseases, cancer, and viral infections, and

to act as general antioxidants. Tannins are water-soluble phenolic compounds of highmolecular weight, and are classified as condensed (proanthocyanidins) or hydrolyzable

(gallotannins or ellagitannins). The prevention of several chronic diseases, including cancer,

cardiovascular and neurological diseases, and inflammation, have been associated with theintake of tannins. In general, tannins are known to have certain health benefits, such as

antioxidant, anti-allergy, antihypertensive, and antitumor, as well as antimicrobial activities

(Okuda, 2005). Condensed tannins are associated with foods of high antioxidant capacity,such as wine, cocoa, and grape seed (Gu et al., 2004). Hydrolyzable tannins have been iden-

tified in several fruits and nuts, such as pomegranate juice (Seeram et al., 2007) and walnuts

(Fukuda et al., 2003). Ellagitannins have recently attracted attention because of their antioxi-dant capacity and their antiproliferative activity, which inhibit prostate cancer growth (Seeram

et al., 2007). Upon hydrolysis, ellagitannins release ellagic acid, which is also of particular

interest, as it reportedly has antiviral properties (Corthourt et al., 1991) and provides protectionagainst cancers of the colon, lung, and esophagus (Rao et al., 1991; Stoner & Morse, 1997).

A study was conducted to evaluate the differences in phenolic compounds betweenorganically and conventionally grown pecan cultivars, and it concluded that the effects on

cultivation method vary by cultivar (Malik et al., 2009). Three pecan cultivars were analyzed:

Cheyenne, Desirable, and Wichita. Nine free phenolic compounds were identified: gallicacid, catechol, m-coumaric acid, catechin, caffeic acid, epicatechin, chlorogenic acid, ellagic

FIGURE 104.4HPLC chromatogram of the main hydrolyzabletannins from defatted Choctaw pecan kernels at280 and 360 nm. Peaks were defined by mass

spectrometry, including (1) 2, 3 HHDP-glucose

(RT, 2.96 min; lmax 247; 481m/z); (2)Pedunculagin isomer (RT, 7.81 min; lmax 247;783m/z); (3) Galloyl pedunculagin (RT, 11.68 min;

lmax 248; 951 m/z); (4) Glausrin C (RT, 15.54 min;

lmax 270; 933 m/z); (5) Ellagic acid pentose

conjugate (RT, 19.35 min; lmax 249, 360; 433 m/z);

(6) Ellagic acid (RT, 20.42 min; lmax 246, 271,365; 301 m/z); (7) Ellagic acid galloyl pentose

conjugate (RT, 22.24 min; lmax 247, 359; 585 m/z);

(8) Ellagic acid galloyl pentose conjugate (RT,

23.5 min; lmax 246, 360; 585 m/z).

CHAPTER 104Pecan Nut Cultivars and Antioxidants

887

acid, and an ellagic acid derivative. Only catechin, gallic acid, and ellagic acid were present

in sufficient amounts to be quantified. Results showed that organically grown Desirable had

a higher concentration of catechin and ellagic acid (86% and 311%, respectively) than theconventionally grown; however, there were no significant differences in the levels of gallic

acid. In the other two organically grown varieties, Cheyenne and Wichita, the differences

were smaller, but followed the same trend. It was concluded that growing organic pecanscould increase the phenolic content in the kernel, but that results may depend on the

cultivar investigated.

In another study, the condensed and hydrolyzable tannins present in kernels from fourcultivars (Choctaw, Desirable, GraCross, and Kiowa) were identified (Ortiz-Quezada et al.,

unpublished data) (Figure 104.4). Extracts of defatted pecan powder were obtained to

measure total phenolics (TP) and antioxidant activities, using 2, 2-diphenyl-1-picrylhydrazyl(DPPH) and the ORAC assay. GraCross and Desirable had a significantly higher TP content,

but only GraCross showed a high CT content and antioxidant capacity by DPPH and ORAC

(Figure 104.5). Nonetheless, the ellagitannin content, as measured after a 2-M HCl hydro-lysis by HPLC, showed inverse results, as Desirable and Kiowa had the highest ET value,

followed by Choctaw, and lastly by GraCross. Extracts were analyzed by HPLC-MS, and

tannins were identified in the negative ion mode according to their retention times, PDAand mass spectra, daughter ions, and fragmentation patterns. Thirteen ellagitannins were

identified, but three other ellagitannins have not yet been characterized (599, 951 and

1085m/z); free ellagic acid was also found. The masses of these ellagitannins ranged from433 to 1207m/z. Now that the chemistry of defatted pecan has been characterized, health

benefit assays can be performed in order to find alternative uses for pecan and understandtheir mechanisms of action.

A study in progress will explore the effects of pecan metabolites on adipogenesis, as an anti-

obesity assay at the molecular level.

ADVERSE EFFECTS AND REACTIONS (ALLERGIES AND TOXICITY)Pecan kernels can be allergenic for sensitive population. A 2S albumin, Car i 1, has beencharacterized as the allergen contained in pecan protein. Another group of allergens

FIGURE 104.5(A) Total phenolic content; (B) condensed tannin content; (C) antioxidant capacity by DPPH; (D) antioxidant capacity byORAC of four pecan cultivars. The effects of pecan variety on phenolic content and the corresponding antioxidant activity.

GraCross variety showed the overall highest phenolic and antioxidant activity.

PART 2Effects of Specific Nuts and Seeds

888

(neoallergens), characterized by the same molecular weight as the original allergen, can

develop during storage or after a thermal treatment, such as baking or roasting (Malanin et al.,

1995). These neoallergens can derive from protein degradation due to autolysis that involvesthe interaction with hydrolyzed sugars (Maillard or browning reaction) (Berrens, 1996).

Consequently, several individuals that are not allergic to raw or fresh pecans may develop

symptoms in response to heated or stored pecan kernels. Another study found no toxicity forpecan color after feeding at a concentration of 5% to female rats for 90 days (Sekita et al.,

1998).

Indirect toxicity caused by ingestion of pecan kernels may be also caused by mold developing

during storage at relatively high humidity. Even without apparent shell damage, spores of

Aspergillus spp. and Penicillium spp. may be present in the kernel (Doupnik & Bell, 1971).Aspergillus is of special concern, since it produces aflatoxins, which are toxic and carcinogenic,

especially to the liver. If pecans are moldy, aflatoxins may be present above safe levels

of < 20 ppb.

SUMMARY POINTSl Pecan is the most valuable nut tree native to North America.

l Pecan use by Native Americans goes back to archaeological evidence found in present-dayIllinois, dating from 9000 years ago.

l Over 1000 different pecan varieties have been described.

l The United States and Mexico are the greatest producers of this nut.l Pecan’s high antioxidant capacity comes from the non-lipid portion.

CHAPTER 104Pecan Nut Cultivars and Antioxidants

l Defatted pecan kernels contain phenolic compounds; the main ones are gallic acid,catechin, epicatechin, ellagic acid, and ellagic acid derivatives.

l These individual phenolics are arranged in polymers as condensed and hydrolyzable

tannins.l Pecan nut shells contain mainly condensed tannins.

l These phenolic compounds have been proven to be beneficial against several cancers and

inflammation, and to have antiviral and antihypertensive activity, among others.l The identified allergen is a 2S albumin called Car i 1.

l Pecans can become toxic when they get moldy.

889

ReferencesBerrens, L. (1996). Neoallergens in heated pecan nut: products of Maillard-type degradation? Allergy, 51, 277e278.

Brison, F. R. (1974). Pecan culture. Austin, TX: Capital Printing.

Corthourt, J., Pieters, L. A., Claeys, M., Vanden Berghe, D. A., & Vlietinck, A. J. (1991). Antiviral ellagitannins fromSpondias mombin. Phytochemistry, 30, 1129e1130.

Doupnik, B., & Bell, D. K. (1971). Toxicity to chicks of Aspergillus and Penicillium species isolated from moldy

pecans. Applied Microbiology, 21, 1104e1106.

Fukuda, T., Ito, H., & Yoshida, T. (2003). Antioxidative polyphenols from walnuts (Juglans regia L.). Phytochemistry,

63, 795e801.

Gu, L., Kelm, M. A., Hammerstone, J. F., Beecher, G., Holden, J., Haytowitz, D., et al. (2004). Concentrations of

proanthocyanidins in common foods and estimations of normal consumption. Journal of Nutrition, 134,

613e617.

Lombardini, L., Waliczek, T. M., & Zajicek, J. M. (2008). Consumer knowledge of nutritional attributes of pecans

and factors affecting purchasing behavior. HortTechnology, 18, 481e488.

Malanin, K., Lundberg, L., & Johansson, S. G. O. (1995). Anaphylactic reaction caused by neoallergens in heated

pecan nut. Allergy, 50, 988e991.

Malik, N. S. A., Perez, J. L., Lombardini, L., Cornacchia, R., Cisneros-Zevallos, L., & Braford, J. (2009). Phenoliccompounds and fatty acid composition of organic and conventional grown pecan kernels. Journal of the Science

of Food and Agriculture, 89, 2207e2213.

Okuda, T. (2005). Systematics and health effects of chemically distinct tannins in medicinal plants. Phytochemistry,

66, 2012e2031.

Rajaram, S., Burke, K., Connel, B., Myint, T., & Sabate, J. (2001). A monounsaturated fatty acid-rich pecan-enricheddiet favorably alters the serum lipid profile of healthy men and women. Journal of Nutrition, 131, 2275e2279.

Rao, C. V., Tokumo, K., Rigotty, J., Zang, E., Kelloff, G., & Reddy, B. S. (1991). Chemoprevention of colon carci-

nogenesis by dietary administration of piroxicam, a-difluoromethylornithine, 16a-fluoro-5-androsten-17-one,and ellagic acid individually and in combination. Cancer Research, 51, 4528e4534.

Seeram, N. P., Aronson, W. J., Zhang, Y., Henning, S. M., Moro, A., Lee, R., et al. (2007). Pomegranate ellagitannin-derived metabolites inhibit prostate cancer growth and localize to the mouse prostate gland. Journal of Agri-

cultural and Food Chemistry, 55, 7732e7737.

Sekita, K., Saito, M., Uchida, O., Ono, A., Ogawa, Y., Kaneko, T., et al. (1998). Pecan nut color: 90-days dietarytoxicity study in F344 rats. Journal of Food Hygienic Society of Japan, 39, 375e382.

Stoner, G. D., & Morse, M. A. (1997). Isothiocyanates and plant polyphenols as inhibitors of lung and esophageal

cancer. Cancer Letters, 114, 113e119.

Thompson, T. E., & Grauke, L. J. (1991). Pecans and other hickories (Carya). Acta Horticulturae, 290, 839e904.

US Department of Agriculture (USDA). (2009). USDA National Nutrient Database for Standard Reference, Release 22.

Washington, DC: USDA Agricultural Research Service, USDA Nutrient Data Laboratory.

Villarreal-Lozoya, J. E., Lombardini, L., & Cisneros-Zevallos, L. (2007). Phytochemical constituents and antioxidantcapacity of different pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. Food Chemistry, 102, 1241e1249.

Worley, R. (1994). Pecan production. In C. R. Santerre (Ed.), Pecan technology (pp. 12e38). New York, NY:

Chapman & Hall.

Wu, X., Beecher, G. R., Holden, J. M., Haytowitz, D. B., Gebhardt, S. E., & Prior, R. L. (2004). Lipophilic and

hydrophilic antioxidant capacities of common foods in the United States. Journal of Agricultural and FoodChemistry, 52, 4026e4037.