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The effect of sourdough fermentation on the phenolic profile of ivory and brown tef varieties.
A. SLIWINSKI (1), G. Ziegler (1) (1) Pennsylvania State University, University Park, PA, U.S.A..

Tef (<i>Eragrostis tef)</i> is an endemic Ethiopian cereal grain. Due to its small size it is milled whole, and therefore tef flour retains the phenolic compounds present mostly in the bran layer of the grain. These phenolic compounds are found in three forms: free, conjugated (esterified to soluble fibre/sugars) and bound (esterified to insoluble fibre). In cereals, bound phenolic compounds make up the largest portion of total phenolics and can be released by hydrolyzing the ester bonds with strong alkali or acid. Fermentation of other grains, such as oats and barley, has resulted in increases of free phenolic compounds. Two varieties of tef<i>, </i>one ivory and one brown, were subject to a 72-hour fermentation using a sourdough culture (Cultures for Health). Phenolic acids were extracted before and after the process to determine the effects of fermentation on the phenolic acid distribution among the three forms (free/conjugated/bound). Extracts were analyzed by HPLC-DAD, and phenolic acids were identified and quantified by matching peak elution times to external standards and standard calibration curves respectively. The abundance of individual phenolic acids between the three fractions did not change over the course of the 72-hour fermentation in either the ivory or brown tef. However, there were visible color changes of the free-form extract, which was yellow for both ivory and brown tef before fermentation and became purple-green after the fermentation was completed. This result suggests that fermentation is potentially affecting another class of phenolic compounds that are responsible for the colors observed.