Nutritional and functional components in peanuts grown in the United States - fatty acids, vitamin E, and phytosterols
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Peanuts consisting of Runner-, Virginia-, and Spanish-types grown in the United States for production years 2005 and 2006 were collected for the study. Fatty acid profiles in Runner peanuts were significantly (P<0.05) different among the normal, mid-, & high-oleic peanuts investigated. The ratio of oleic to linoleic acids were found to be 1.9±0.3, 5.3±1.1, & 16.9±5.2 for normal, mid-, & high-oleic peanut lipids, respectively. Correlation coefficients (r) revealed a negative relationship between oleic and linoleic acids (r=-0.997, P<0.001). Principal component analysis (PCA) yielded 3 significant principal components (PCs), which together account for 87.2% of the total variance in the fatty acids in Runner peanuts. No significant (P>0.05) differences were noted in total tocopherol levels in normal- (22.4 mg/100 g), mid- (23.9 mg/100 g), and high-oleic (22.4 mg/100 g) Runner peanuts. α-Tocopherol (α-T) levels did vary significantly among the Runner cultivars classified by their oleic acid content (mid, 11.7 mg/100 g; normal, 10.9 mg/100 g; high, 9.8 mg/100 g). The mean α-T level in Runner peanuts was 10.5 mg/100 g, which is 26.7% greater than the imputed value for peanuts, all types (NBD 16087) provided by the USDA National Nutrient Database for Standard Reference. Correlation coefficient (r) among tocopherols revealed a weak inverse relationship between α- and γ-Tocopherol (γ-T) (-0.032) and positive relationships between β-tocopherol (β-T) & γ-T (r=0.436, P<0.001) and γ- & δ-tocopherol (δ-T) (r=0.437, P<0.001). PCA analysis of tocopherol contents in Runner peanuts yielded two significant PCs, which together account for 72.6% of the total variance in data set. For phytosterols in Runner-, Virginia-, and Spanish-type peanuts, campesterol, stigmasterol, β-sitosterol, and Δ5-avenasterol were major sterols and clerosterol, Δ5,24(25)-stigmastadienol, Δ7-sitosterol and cycloartenol were minor sterols. Phytosterols were identified by retention time and mass spectra. The inclusion of steryl glucosides by acid hydrolysis increased total phytosterol levels by approximately 20%. Total phytosterol levels in Spanish (144.1±5.3 mg/100 g) peanuts were significantly higher than in Runner (127.5±6.3 mg/100 g) and Virginia (129.3±6.9 mg/100 g) types (P<0.05). Cluster analysis of phytosterols in peanuts (n=221) segregated the two major clusters represented by significantly lower campesterol & β-sitosterol and higher campesterol & β-sitosterol (P<0.05).