ELUCIDATING DIFFERENCES IN PHENOLIC PROFILE BETWEEN TEF (ERAGROSTIS TEF) VARIETIES USING MULTIVARIATE ANALYSES
Open Access
- Author:
- Sliwinski, Anna
- Graduate Program:
- Food Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 15, 2017
- Committee Members:
- Gregory Ray Ziegler, Thesis Advisor/Co-Advisor
Joshua D Lambert, Committee Member
Jairam Kp Vanamala, Committee Member - Keywords:
- tef
eragrostis tef
phenolic
polyphenol
multivariate analysis
principal component analysis - Abstract:
- Tef (Eragrostis tef) is a cereal grain endemic to Ethiopia. Due to its small size it is milled whole and, therefore, tef flour retains the phenolic compounds that are present mostly in the bran layer of the grain. These phenolic compounds are found in three forms: free, conjugated (bound to soluble fiber/sugars), and bound (bound to insoluble fiber). 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. It is thought that the distribution of phenolic compounds between these fractions and interaction with fiber within a certain food can have unique influence on metabolism and physiology in the body of those who consume it. However, many factors including variety can affect phenolic content. Eight tef varieties, six grown in the same season (2012) and location (Bishoftu, a.k.a. Debrezeit, Ethiopia) and two grown in Idaho, USA (purchased from TeffCo in 2016) were extracted to characterize their free, conjugated, and bound phenolic profiles. Extracts were analyzed by high performance liquid chromatography with a diode array detector (HPLC-DAD), and phenolic acids were identified and quantified by matching peak elution times to external standards and standard calibration curves, respectively. Principal component analysis (PCA) and multifactor analysis (MFA) were run to compare chromatograms of the different fractions and varieties. These analyses were able to differentiate between brown and white varieties in the free and bound phenolic fractions with separation in the first principal component being dominated by large hydrophobic compounds eluting in the flavonoid portion of the chromatogram. Ferulic acid was found to be the most abundant phenolic compound in the bound fraction with the DZ-Cr-384 (Kuncho) variety having the highest ferulic acid content (280.73 μg/g defatted tef flour). There were no significant differences in total phenolic content between varieties as determined by the Folin-Ciocalteu assay.