Fatty acid composition of tree nut oils

Tree nuts are an important part of the diets of many people throughout the world (Woodroof, 1979b). While information has been published concerning the fatty acid composition of most tree nuts, it is often difficult to compare data from various sources because of a lack of uniformity of analytical techniques used for quantitation. 

Changes in agronomic practices and the inroduction of new cultivars in recent years have been shown to affect tree nut composition. For example, it has been demonstrated that irrigation retarded oleic acid synthesis in filberts (hazel nuts) and reduced its proportion at all stages of ripening. Heaton et al. (1966) showed that nitrogen application to pecan trees caused oleic acid to decrease and linoleic acid to increase in nut kernels. Heaton et al. (1975) reported that variations in fatty acid composition of pecan nuts were associated with cultivar and year of production. These variations in fatty acid composition may influence the nutritional value and storage stability of tree nuts. Listed in Table 6.5 are the total oil content and fatty acid composition of 13 types of tree nut kernels. 

In addition to the effects of cultivar and agronomic practices on oil content and fatty acid composition of tree nuts, the state of maturity may have an influence. 

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Beuchat, L.R. and Worthington, R.E. (1978) Fatty acid composition of tree nut oils. J. Food Technol.,... 

Table 3.136 Oil fatty acid composition of tree nuts ... 

The complete fatty acid composition of pine nut is available in Chapter 2. Pine trees belong to the genus Pirns and contain an unusual group of polyunsaturated fatty acids (PUFA) present in considerable amounts in the seed oil of conifers. These particular PUFA contain 18 or 20 carbon atoms, with their first double bond at the location and a second double bond located at either A9 or Al 1. Thus, there is more than one methylene group separating double bonds on the fatty acid chain, and the term A polymethylene-interrupted polyunsaturated fatty acid (PMI PUFA) is apphed. 

Walnuts contain about 65% lipids, however, considerable differences exist among varieties (range 52-70%, w/w) (1,40). Walnuts also contain 15.8% protein, 13.7% carbohydrate, 4.1% water, and 1.8% ash (w/w) (1). The fatty acid composition of walnut oil is unique compared with other tree nut oils for two reasons walnut oil contains predominantly linoleic acid (49-63%) and a considerable amount of ot-linolenic acid (8-15.5%). Other fatty acids present include oleic acid (13.8-26.1%), palmitic acid (6.7-8.7%), and stearic acid (1.4—2.5%) (Table 5) (40). The tocopherol content of walnut oil varies among different cultivars and extraction procedures and ranges between 268 mg/kg and 436 mg/kg. The predominant tocol isomer is y-tocopherol (>90%), followed by a-tocopherol (6%), and then (3- and 8-tocopherols (41). Nonpolar lipids have been shown to constitute 96.9% of total lipids in walnut oil, whereas polar lipids account for 3.1%. The polar lipid fraction consisted of 73.4% sphingolipids (ceramides and galactosylcera-mides) and 26.6% phospholipids (predominantly phosphatidylethanolamine) (42). Walnut oil contains approximately 1.8g/kg phytosterols (1), primarily p-sitosterol (85%), followed by A-5-avenasterol (7.3%), campesterol (4.6%), and, finally, cholesterol (1.1%) (42). 

Pine nuts (pinon or pignolia) are the edible seeds within the pine cone of several varieties of pine trees (Pinus sp.) but most commonly Pinus pinea or stone pine . Pine nuts are harvested all over the world, most notably in Russia, China, North Korea, Spain, Italy, and Turkey, among others. Pine nuts contain 48-61% lipids by weight (1, 60). Other constiments of pine nut include carbohydrate (19.3%), protein (11.6%), water (5.9%), and ash (2.2%) (1). Pine nut oil contains predominantly linoleic acid (46.4%) and oleic acid (38.1%). Maritime pine nut Pinus pinaster) oil also contains two fatty acids that are unique among tree nut oils pinoleic acid and sciadonic acid (Figure 2), which exist at 7% each in pine nut oU and may have antiatherogenic effects (Table 8) (63). The phenolic acid composition of defatted pine nut meal is given in Table 2 and shows that caffeic acid is the predominant phenolic compound (14). 

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