Freeze-dried and air-dried Marionberry, Strawberry, and Corn Produced Using Conventional, Organic, and Sustainable Agricultural Practices Compared for Total Phenolic and Ascorbic Acid Content

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.