Title page for ETD etd-09282004-153221


Type of Document Dissertation
Author Powell, Jodi
Author's Email Address jopowel4@vt.edu
URN etd-09282004-153221
Title Evaluation of Initial Flavor Fade in Fresh Roasted Peanuts using Gas Chromatography-Flame Ionization Detection, Gas Chromatography-Olfactometry, Sensory Analysis, and Chemosensory Techniques
Degree PhD
Department Food Science and Technology
Advisory Committee
Advisor Name Title
O'Keefe, Sean F. Committee Chair
Duncan, Susan E. Committee Member
Eigel, William N. III Committee Member
Mallikarjunan, Parameswarakumar Committee Member
Williams, Robert C. Committee Member
Keywords
  • solid phase microextraction
  • gas chromatography-olfactometry
  • roasted peanuts
  • Pyrazines
Date of Defense 2004-08-27
Availability unrestricted
Abstract

Preventing flavor fade requires an understanding of the relationship between carbonyl amine and lipid oxidation reactions. The polyunsaturated fatty acid content of lipids in peanuts makes them more susceptible to lipid oxidation. The major by-products of the oxidation reaction are nonanal, hexanal, octanal, and decanal. These chemicals are associated with cardboardy, painty, and oxidized flavors associated with flavor fade. The carbonyl-amine reaction yields a variety of pyrazines with positive flavor attributes.

Initial flavor notes were explored through sensory work, Gas Chromatography-Olfactometry, and chemical analysis. The fresh roasted volatiles produced from roasted peanuts and the aldehydes resulting from oxidation were also evaluated using GC-FID to quantify and identify the pyrazines and hexanal over a 21 day storage period. Electronic Nose was used to determine differences between storage periods.

Gas chromatography-Olfactometry identified potent pyrazines contributing to fresh roasted peanutty aroma in fresh peanuts. Using GC-FID a significant decrease (p<.05) in 2-ethylpyrazine and 2,3-diethylpyrazine concentration was found over a 21-day period. No significant difference (p>0.05) was noted in the other pyrazines evaluated. A significant increase (p<0.05) was noted in the hexanal concentration over a 21-day period. The peroxide values and sensory analysis correlated directly with the GC-FID results with a significant increase (p<0.05) in peroxide value at Day 14 and Day 21, and a significant decrease (p<0.05) in fresh roasted peanuty flavor from days 0-21 and a significant increase (p<.05) in painty, cardboardy and bitter from days 7-21. The electronic nose successfully separated Day 0 and Day 21 samples from Day 7 and 14, which were also separated, but with minimal overlap.

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