Received for review June 6, 2002. Revised manuscript received December 4, 2002. Accepted December 9, 2002. We thank Jim Dewey and Oregon Freeze-Dry, Inc., and Kim Baglien and Stahlbush Island Farms, Inc., for kind financial support.

Abstract:

Secondary phenolic metabolites play an important role in plant defense mechanisms, and increasing evidence indicates that many are important in human health. To date, few studies have investigated the impact of various agricultural practices on levels of secondary plant metabolites. To address this issue, the total phenolic (TP) content of marionberries, strawberries, and corn grown by sustainable, organic, or conventional cultural practices were measured. Additionally, the effects of three common postharvest processing treatments (freezing, freeze-drying, and air-drying) on the TP content of these agricultural products were also investigated. Statistically higher levels of TPs were consistently found in organically and sustainably grown foods as compared to those produced by conventional agricultural practices. In all samples, freeze-drying preserved higher levels of TPs in comparison with air-drying.

Keywords: Phenolics; ascorbic acid; sustainable agriculture; organic agriculture; conventional agriculture; strawberry; corn; marionberry

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