Use of Capillary Electrophoresis to Determine Oleic and Linoleic Acid Content of Peanut Seed.

A common consumer complaint regarding peanut products is one involving short shelf life and rapid rancidity.  Peanut cultivars with elevated oleic acid content (and decreased linoleic content) have been shown to have an increased shelf life and thus have become largely preferred by peanut processors.  Consequently, peanut breeders often focus on pyramiding the high oleic trait with other desired traits, such as disease resistance, into newly developed breeding materials.  Currently, two methods are in use for determining the oleic/linoleic ratio of peanut seed: Gas chromatography (GC) which is accurate but destructive, and near infrared reflectance (NIR) which requires expensive equipment and is limited to classifying seed as either high-oleic or not high-oleic.  This study has shown for the first time the suitability of capillary electrophoresis (CE) with a partially aqueous electrolyte system for the analysis of free fatty acids (FFA´s) in small portions of single peanut seeds. The partially aqueous electrolyte system consisted of 40 mM Tris, 2.5 mM adenosine-5’-monophosphate (AMP) and 7 mM α–cyclodextrin (α–CD) in NMF-dioxane-water  (5:3:2, v/v) mixture, pH 8-9.  While AMP served as the background UV absorber for indirect UV detection of the FFA´s, the α–CD functioned as the selectivity modulator by affecting the relative effective electrophoretic mobilities of the various FFA´s due to their differential association with α–CD.  This CE method allowed the non-destructive screening of peanut seeds for accurate content of oleic and linoleic acids, which is essential in breeding of peanuts of high oleic acid content.  The extraction method of FFA´s from peanut seeds is very reproducible with high recovery approaching quantitative yield (~ 97% recovery).