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Development and Application of a Methodology to Determine Free Ferulic Acid and Ferulic Acid Ester-Linked to Different Types of Carbohydrates in Cereal Products

¹Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN. ²Department of Food Chemistry and Phytochemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany. ³Corresponding author. Karlsruhe Institute of Technology, Institute of Applied Biosciences, Adenauerring 20A, 76131 Karlsruhe, Germany. Phone: +49-721-608-4-2936. Fax: +49-721-608-4-7255. E-mail: mirko.bunzel@kit.edu

Ferulic acid bioavailability is dependent on its form present in food. This necessitates a methodology to quantify different groups of ferulic acid derivatives in food products, especially cereal-based products. The aim of the proposed methodology is to separate and quantify ferulic acid ester-linked to mono- and/or oligosaccharides (OF), to soluble polysaccharides (SPF), and to insoluble polysaccharides (IPF) as well as in its free form. Development and partial validation of this method, which was widely based on liquid/liquid extraction and precipitation steps, was performed using characterized standard materials isolated from corn bran. As the determination of OF was one of the major goals of this methodology, three different feruloylated mono- and oligosaccharides were used for method development and validation. To determine the accuracy of the method, ferulic acid–containing standard materials added to a starch matrix were extracted and separated according to the developed protocol. The separated ferulic acid esters were saponified before ferulic acid was analyzed by reversed phase HPLC. Recovery rates were generally between 70 and 103%, with the lowest recovery rates for SPF and highest recovery rates for IPF and OF. Finally, the applicability of the method to unprocessed and processed wheat bran samples was demonstrated.