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Title: Phenolic compounds and fatty acid composition of organic and conventional grown pecan kernels


Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2009
Publication Date: 7/29/2009
Citation: Malik, N.S., Perez, J.L., Lombardini, L., Cornacchia, R., Cisneros-Zevallos, L., Bradford, J.M. 2009. Phenolic compounds and fatty acid composition of organic and conventional grown pecan kernels. Journal of the Science of Food and Agriculture. 89(13):2207-2213.

Interpretive Summary: Intensive agriculture for maximal productivity utilizing high inputs of fertilizers and pesticides during the last century is now being blamed for decline in soil fertility and to adverse effects on environment. Organic farming proposed as an alternative for sustainable agriculture about fifty years ago is now gaining widespread momentum for being friendly to the environment and producing more nutritious food for human health. It is unlikely that American or Western diets could create deficiencies in protein, carbohydrates, or vitamins so the argument in favor of organic foods has to be based on secondary metabolites such as phenolic compounds. There are over 5000 species of phenolic compounds in plants. These compounds are not only involved in color, aroma and taste of the food but are infrequently involved with health benefits of foods. For example, phenolic compounds have been reported to protect against, atherosclerosis, hypertension, cardiovascular diseases, cancer, viral infections, and act as antidepressant and general antioxidants. For some of these reasons, the market for organically cultivated foods has grown 20-25% annually and projected to surpass $22 billion by 2010. This study was conducted to evaluate the differences between phenolic compounds in organically and conventionally grown pecans cultivars. In addition, fatty acid composition was also included in the study because, pecans are rich in lipid contents and difference in fatty acid composition of organically versus conventionally produced olive oil has been reported previously. Analysis of phenolic compounds and fatty acid composition in three cultivars of pecans (Desirable, Cheyenne, and Wichita), grown organically and conventionally, show that only ‘Desirable’ cultivar produces higher levels of health benefiting phenolic compounds (e.g. catechins and ellagic acid) and fatty acid (oleic acid). It is concluded that for studies on organic system aimed to evaluate the effect of specific cultural practices it is important to choose an appropriate cultivar.

Technical Abstract: In this study, differences in contents of phenolic compounds and fatty acids in pecan kernels of organically versus conventionally grown pecan cultivars (‘Desirable’, ‘Cheyenne’, and ‘Wichita’) were evaluated. Although we were able to identify nine phenolic compounds (gallic acid, catechol, catechin, epicatechin, m-coumaric acid, chlorogenic acid, ellagic acid and an ellagic acid derivative) in the methanol extract (80% methanol) of defatted kernels, only three compounds (gallic acid, catechin, and ellagic acid) existed in sufficient amounts to accurately quantify levels in different cultivars to study differences in organic versus conventional cultivation. Considerably higher levels of ellagic acid and catechin were found in organically grown ‘Desirable’ cultivar; i.e., organic versus conventional samples contained 85 versus 20 µg/g of ellagic acid, and 90 versus 45 µg/g of catechin. Differences in other cultivars were less than 21%. Thus, effects of cultural practices (such as organic versus conventional) on phenolic compounds would depend on the cultivar used. Oil contents were also significantly greater only in organically grown ‘Desirable’ cultivar; i.e., 61.26% oil in organically grown kernels versus 53.40% oil in conventionally grown samples. Oleic acid was the major free fatty acid present and its contents were significantly higher in organically grown ‘Desirable’ and ‘Cheyenne’ cultivars versus the conventionally grown, while there was no difference in levels of oleic acid in‘Wichita’ cultivar. These results once again show that the effects of cultural differences (i.e. organic versus conventional cultivation) largely depend on the type of cultivar used in the study.