The use of microwave technology as an alternative blanching method for peanuts could potentially reduce energy costs and processing time, and lead to products with better nutrient retention. However, an off-flavor was found in peanuts which were microwave-blanched at high temperatures. As a result, the objective of this research has been to determine the impact of different microwave blanching parameters on the properties of roasted peanuts, and to characterize the off-flavor observed during high-temperature microwave blanching using a descriptive sensory panel and analysis of volatile flavor compounds. The processing parameters best suited for microwave blanching of peanuts were determined based on energy absorbed during processing, internal and surface temperatures, loss in moisture content, and blanchability. The best blanchability resulted from higher process temperatures and lower final moisture content. However, peanuts which reached the highest internal temperatures during blanching also developed an off-flavor, which was characterized by increased intensities of stale/floral and burnt/ashy notes. Solvent extraction / solvent assisted flavor evaporation (SAFE), gas chromatography-olfactometry (GC/O), gas chromatography-mass spectrometry (GC/MS), aroma extract dilution analysis (AEDA), threshold testing, and model systems were used to examine the chemical compounds which may be responsible for this microwave-related off-flavor. Analysis revealed an increased formation of guaiacol, phenylacetaldehyde, and 2,6-dimethylpyrazine in the off-flavored peanuts as compared to a process control, which led to the burnt and stale/floral characteristics noted by descriptive sensory panel. These compounds were only a small fraction of over 200 aroma-active compounds which were found to contribute to roasted peanut flavor using GC/O. This research illustrates the importance of the relative concentrations of the many aroma-active compounds found in peanuts. These findings could aid in training sensory panels to evaluate processing-related off-flavors, because guaiacol and phenylacetaldehyde could be used as chemical standards to define the burnt/ashy and stale/floral off-flavors which can occur during high temperature processing. Through this project, it was determined that it is possible to achieve acceptable blanchability in peanuts using microwave blanching while minimizing the possibility of an off-flavor.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-07052006-113250 |
| Date | 18 July 2006 |
| Creators | Schirack, Andriana Vais |
| Contributors | Dr. MaryAnne Drake, Dr. Donn Ward, Dr. K.P. Sandeep, Dr. Tim Sanders |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-07052006-113250/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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