Title page for ETD etd-11152006-082336

Type of Document Master's Thesis
Author Holliday, Darryl Lourey
Author's Email Address dholli2@lsu.edu
URN etd-11152006-082336
Title Phenolic Compounds and Antioxidant Activity of Oat Bran by Various Extraction Methods
Degree Master of Science (M.S.)
Department Food Science
Advisory Committee
Advisor Name Title
Zhimin Xu Committee Chair
Daryl McKee Committee Member
Kerry Dooley Committee Member
Witoon Prinyawiwatkul Committee Member
  • oat bran
  • antioxidants
  • phenolics
Date of Defense 2006-10-02
Availability unrestricted
Recent studies have suggested that the health promoting capabilities of oats are due to its antioxidants (tocopherols, tocotrienols, and sterols) found within the bran along with phenolic compounds, such as avenanthramides, p-hydroxybenoic acid and vanillic acid. Long-chain fatty acid oxidation is directly responsible for most off-flavors in food. Since oat bran is a good source of antioxidants, a concentrated extract could be used as a natural preservative, for foods rich in unsaturated long-chain fatty acids.

Three methods, traditional solvent (TSE), microwave-assisted solvent (MAS), and supercritical fluid treatment (SFT), were used to obtain the extracts. One extraction temperature in TSE, 60C, and two extraction temperatures in MAS, 60C and 100C, were tested. The DPPH (2, 2'-diphenyl-1-picrylhydrazyl) method demonstrated that the MAS-100C was the most efficient extraction in the group, thereby serving as MAS sample against the TSE and supercritical-treated samples.

For the treated samples, oat bran was exposed to supercritical CO2 before extraction. Three different temperatures of CO2 were tested, 25C, 50C, and 75C. The treated samples then underwent MAS-100C to gather extracts for analysis. The experimental results for the DPPH test favored the SFT-75C treatment at a 40μl concentration. Therefore, SFT-75C served as the treated sample in the final three experiments.

Antioxidant activity was further tested using two other methods: cholesterol oxidation and the DHA model. The total phenolic content was determined using Folin-Ciocalteau Method. The SFT-75C treatment showed statistically higher results for antioxidant activity in both the cholesterol oxidation and DHA oxidation experiments over the TSE-60C or MAS-100C. In terms of total phenolics, the SFT-75C treatment showed statistically higher results than TSE or MAS-100C in terms of catechin equivalency, but no statistical difference was seen among the treatments when compared on the basis of total phenolics per gram of original oat bran sample. However, extraction techniques can be evaluated based on extract yield, which this research demonstrated would be SFE-75C.

In conclusion, the SFT-75C treatment was the optimal extraction based on antioxidant activity, catechin equivalency for total phenolics, and sample yield. This information could be used in the future development of food products as a natural antioxidant source.

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