Can I use the published ORAC data for comparison purpose?
No. In the middle of the 90's, Cao and coworkers published the ORAC values of some vegetables and fruits1. The results primarily demonstrate that the ORAC assay is a valuable tool to evaluate the antioxidant activity. However, due to the limited sample sizes and varieties, the published ORAC values of vegetables and fruits are not comprehensive. Importantly, the most published ORAC results are obtained using the old method; therefore they are not valid anymore.  Furthermore, the naturally occurring antioxidants actually are the secondary metabolites of natural products; Mother Nature has a profound influence on their biosynthesis pathways.  For instance, the geographic locations, weather conditions and the varieties of the species have been determined to influence the antioxidant property chemically and physiologically. We screened over 1000 vegetables last year; the conclusion is that "not every broccoli is created equally"2.

1 Cao, G. H.; Sofic, E.; Prior, R. L. Antioxidant capacity of tea and common vegetables. J. Agric.Food Chem. 1996, 44, 3426-3431.

2 Ou, B., Huang, D., Hampsch-Woodill, M., Flanagan, J., Deemer, E.. Analysis of antioxidant activity of common vegetables employing Oxygen Radical Absorbance Capacity (ORAC) and Ferric Reducing Antioxidant Power (FRAP) assays: A  comparative study. J. Agric.Food Chem. 2002, in press.