Additive Effect of Sub-Threshold Concentrations of Some Organic Compounds Associated with Food Aromas

Behavioural Brain Research

Abraham

2005

The investigation explored the olfactory detectability of two chemically and structurally similar esters, ethyl propanoate and ethyl heptanoate, presented singly and in mixtures. Initially, we measured concentration-detection (i.e., psychometric) functions for the odor of ethyl propanoate and ethyl heptanoate presented singly. Using this information, we prepared binary mixtures of the two chemicals in varying complementary proportions and, also, selected concentrations of the single compounds, such that, if a rule of response-addition (i.e., independence of detection) were to hold, the stimuli (mixed and single) should approximate equal detection. Next, we measured the actual detectability of these stimuli within the same experiment. The results were analyzed in terms of response-addition (or -additivity) and of dose-addition (oradditivity). The outcome revealed that at low levels of detectability the mixtures approximate response-addition, that is, independence of detection, whereas at high levels of detectability they approximate dose-addition. In the light of previous findings for the olfactory detection of the more dissimilar chemical pairs 1-butanol/2-heptanone and butyl acetate/toluene, we conclude that the described outcome generalizes across a variety of chemical pairs.

Section: Introductionmentioning

confidence: 99%

Odor detection of single chemicals and binary mixtures

Behavioural Brain Research

Abraham

2005

“…An early report testing organic compounds associated with food aromas (principally saturated, unsaturated, and branched aldehydes but also a limited number of other compounds: dimethyl sulfide, octanol, butyric acid, and butylamine) found that a simple rule of sub-threshold additivity fitted the results quite accurately [24]. Since then, other studies have found various degrees of sub-threshold additivity in olfactory detection, including some possible cases of synergism or hyperadditivity [4,31,38,40].…”

Section: Introductionmentioning

confidence: 99%

Dose-addition of individual odorants in the odor detection of binary mixtures

Behavioural Brain Research

Abraham

2003

In a series of experiments, we have explored the rules of olfactory detection agonism between the odorants butyl acetate and toluene. First, we obtained the concentration-detection function for the odor of the individual compounds. Second, we selected the concentrations of the two substances producing three levels of detectability (low, medium, and high) and, for each level, tested the comparative detectability of the two single chemicals and three mixtures of varying proportions. In each case, the mixtures were prepared in such way that, if a rule of complete dose addition were to hold, all five stimuli (two single, three mixtures) should be equally detected. The outcome revealed complete dose addition at relatively low detectability levels but fell short of dose addition at medium and high levels. A recent analogous study on trigeminal chemosensory detection via nasal pungency and eye irritation of these same stimuli have shown a similar trend but showed a less dramatic loss of dose additivity with increased detectability. These results on detection of mixtures suggest a more selective window of chemical tuning (i.e., less dose-addition) in olfaction than in trigeminal chemoreception.

“…The very early peaks appear even in "blank" squeezebottles containing odorless mineral oil or deionized water. stimulus agonism (Guadagni, Buttery, Okano, & Burr, 1963;Patterson, Stevens, Cain, & Cometto-Mufiiz, 1993) with some cases of synergistic stimulus agonism as number ofcomponents increased (Baker, 1963;Laska & Hudson, 1991;Rosen, Peter, & Middleton, 1962). Simple stimulus agonism in, for example, a balanced 3-component mixture implies that when the substances are presented mixed, each needs to be at only one third of its individual threshold concentration for the mixture to be perceived.…”

mentioning

confidence: 99%

Agonistic sensory effects of airborne chemicals in mixtures: Odor, nasal pungency, and eye irritation

Perception & Psychophysics

Hudnell

1997

Threshold responses of odor, nasal pungency (irritation), and eye irritation were measured for single chemicals (Lpropanol, l-hexanol, ethyl acetate, heptyl acetate, 2-pentanone, 2-heptanone, toluene, ethyl benzene, and propyl benzene) and mixtures of them (two three-component mixtures, two sixcomponent mixtures, and one nine-component mixture). Nasal pungency was measured in subjects lacking a functional sense of smell (i.e., anosmics) to avoid interference from olfaction. Various degrees of stimulus agonism (additive effects) were observed for each of the three sensory channels when testing mixtures. As the number of components and the lipophilicity of such components in the mixtures increased, so did the degree of agonism, Synergistic stimulus agonism characterized the eyeirritation response for the most complex (the nine-component) and the most lipophilic (one of the sixcomponent) mixtures. Physicochemical properties playa large role in the determination of sensitivity to airborne chemicals, particularly to their ability to evoke irritation. Whilethis has revealed itself previously with respect to single chemicals, it seems to have relevance to mixtures as well.Airborne chemicals in the environment are detected by humans through two sensory channels: olfaction and the so-called common chemical sense (CCS), or chernesthesia. The sense of smell is mediated by the olfactory nerve (cranial nerve I), whereas the facial CCS (from the various mucosae: ocular, nasal, and oral) is principally mediated by the trigeminal nerve (cranial nerve V).Since almost any odorant-at a high enough concentration-evokes not only odor but also chemesthetic sensations, an issue in human chemoreception entails distinguishing between a purely olfactory and a combined olfactory-trigeminal nasal response. We have begun to clarify this matter by measuring nasal detection thresholds to airborne compounds in subjects with a normal