Kern County, located in the South San Joaquin Valley, is the fourth largest agricultural-producing county in the United States and grapes are its largest commodity, followed by almonds and milk. Grapes contain polyphenols that have health-protective effects, including prevention of heart disease and cancer. The protective effects of grape polyphenols have been associated with their antioxidant activities. Additionally, darker coloration in the flesh and skin of fruit, such as orange, red, or black, is associated with enhanced antioxidant activity. The ORAC (oxygen-radical absorbance capacity) assay is widely-used to quantify the antioxidant activities of grape polyphenols. In this study, seven commercial and experimental table grape varieties were selected with a range of skin colors: pale green, dark green, pale red, medium red, dark purple, and black. The skins, seeds, and pulp were separated and extracted with both water and acetone. From these samples, the antioxidant capacity as ORAC of the different fractions and grape varieties were compared. Total phenols (gallic acid equivalents) of all fractions were also determined and correlated well with the ORAC values. This study provided ORAC values for South San Joaquin Valley table grapes and also confirms that these values correlate well with total phenolic concentration.

Funding Support: Grapes and some chemical supplies provided by Sun World International, LLC. Additional funding provided as start-up funds for Dr. Forester at CSUB.