Sub-threshold effects were studied in binary and tertiary mixtures
comprising a panel-recognition-concentration odorant and sub-threshold odorant(s).
Sub-threshold condition was maintained by controlling the sub-threshold
concentration as percentages of subjects' individual detection threshold. The
perceived intensities (overall intensity and several descriptors) of recognizable
odorants were rated using magnitude estimation.
Sub-threshold suppression was common and concentration independent in
mixtures comprising odorants with different functional groups. Suppression was
observed at the lowest sub-threshold concentration tested (30% level). At sub-threshold
concentrations, acetic acid suppressed the perceived intensity of acetaldehyde and ethanol but not vice versa. Acetaldehyde and ethanol, however,
suppressed each other when one was at sub-threshold concentrations in binary
mixtures. Enhancement was observed in tertiary mixtures containing acetaldehyde
at panel recognition concentration and was dependent on sub-threshold
concentrations of acetic acid and ethanol.
In mixtures that contained aliphatic acids with different carbon chain
lengths (acetic acid, propanoic acid and n-butanoic acid), sub-threshold
enhancement and suppression depended on concentrations and molecular similarity
of mixture components. Sub-threshold effects were not observed when the acids
were two carbon-atoms different. 50% and 70% sub-threshold levels caused sub-threshold
enhancement; however, higher concentrations caused decrease in
intensity. Sub-threshold suppression was observed in mixtures containing n-butanoic
acid as a recognizable odorants with propanoic acid at a 10% level in a
binary mixture and acetic acid and propanoic acid in a 30%-30% combination in
the tertiary mixture. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27222 |
| Date | 06 September 2002 |
| Creators | Lopetcharat, Kannapon |
| Contributors | McDaniel, Mina R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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