Odor qualities, determining

Determination of retention indices Evaluation of odor quality... 

The extract of the volatiles is separated by high resolution gas chromatography (HRGC) and the odor of the compounds is assessed by sniffing the effluent of the GC column in parallel with the FID-detection. This technique allows the detection of odor-active volatiles, the determination of their odor qualities and, most important, the combination of these sensory data with an analytical parameter, the retention index (RI). In Figure 2, the results of... 

Statistical evaluation of the degree to which the synthetic sample (prepared by adding the above three compounds to nonirradiated enzyme-inactivated beef) differed from enzyme-inactivated irradiated beef, was determined. Using the score sheet given in Figure 4, panel members evaluated the odor quality of a standard sample (S) and two coded samples (one of which was identical with the standard) and indicated the degree of difference noted. Two sets of samples were tested in a single session. One had irradiated beef slurry as the standard sample (Set I, Table VII). The... 

A threshold of significant effect was considered to have been determined when a significant difference in odor quality from that of enzyme-inactivated nonirradiated beef slurry was noted. As before, a t-test for correlated pairs was used. The following quantities of methional, 1-nonanal, and phenylacetaldehyde were required. 

Natural stimuli are never block-shaped increases of concentration but rather continuous series of sharp rises and drops in concentrations across a wide dynamic range (Murlis et al., 1992). Odor quality may be encoded in the first 200 ms while the off-characterisitics determine the accuracy with which the end of stimulation and the separation of rapid odor pulses are detected. This has proven to be highly relevant for mechanism of oriented flight (Vickers and Baker, 1996). In fact such differences in ability to follow rapid sequences of odor pulses were demonstrated for two moth ORNs that respond to the same pheromone component but with different temporal accuracy (Almaas et al., 1991). If temporal patterns of activity in single ORNs depend on which odorant they respond to, some odors can be encoded with high temporal accuracy in one ORN, while leaving other... 

The properties of perfume materials are intimately related to their chemical constitution, but the mechanisms whereby chemical structure leads to odor perception involve, in crucial ways, a physical phenomenon the mutual attraction forces between molecules. These forces determine the rate of evaporation of odor materials from solutions or surfaces, they are the basis of fixation and substantivity, they explain why the odor quality of mixtures varies depending upon the solvent or base in which they are incorporated. They are also involved in the very process of odor perception, in the contact between the odorant molecule and the receptor cell. Moreover they are at the heart of distillation, extraction, solubility, and the mechanism of chromatography. In this chapter, we will briefly discuss the physical basis of some of these phenomena, showing also how the attraction forces between molecules are related to their chemical structure. 

The standard measurement procedure for odor determination (VDI, 1994) is called olfactometry. It uses the human olfactory sense (Gostelow et al, 2001) for the determination of odor qualities. The human nose is an extremely sensitive odor detector and is used in subjective and objective sensory measurements. The latter expresses the strength of odor in terms of the number of dilutions of odor-free air required to reduce the sample odor to threshold concentration (Gostelow et al, 2001). The threshold concentration is reached when the human nose can just smell the odorous substance. Because every nose has different sensitivity, the standard test procedure involves four people at the same time. Prior to olfactory... 

Sensory evaluation is a scientific discipline that uses humans to measure the acceptability and sensory properties of food and other materials. Sensory properties important in food products include attributes of appearance, odor, taste, and texture. The use of humans as measuring devices is necessary because only humans can define what is acceptable, and in many cases, no instmmental or chemical method can adequately measure or replicate the human response. For this reason, sensory evaluation is a vital component in any quality assessment program. In such programs, sensory evaluation can be used to monitor product quality determine effects of alternative processing, ingredients, or formulations evaluate packaging and determine product shelf life. 

Numbers correspond to those in Tables HI and IV. Odor quality as perceived during GCO. Retention indices calculated from GCO data, FFAP = Stabilwax DA column. Average logs flavor dilution (FD) factor (n = 2), neutral/basic fraction determined on DB-5MS and acidic fraction determined on Stabilwax DA column. Con ound tentatively identified based on con arison of odor property and retention indices with reference conq)ound. 2,5-dimethyl-4-hydroxy-3(2 -furanone. 3-hydroxy-4,5-dimethyl-2(5/0 ft iione. 3-methoxy-4-hydroxybenzaldehyde... 

Dale MS, Moylan MS, Koch B, Davis MK (1997) MTBE taste and odor threshold determinations using the flavor profile method. Presented at the Water Quality Technology Conference, 9-13 November 1997, Denver, CO... 

Another Tc value was determined using recognition thresholds rather than detection thresholds. Recognition thresholds (Ter) were measured by sensorially recognizing two kinds of odor differences, the concentration and the odor quality, of individual chemicals presented to panel members. 

During the last decade parathion has been the most used organo-phosphorus insecticide. It has been proved to be valuable in crop protection 27). However, using this compound so much has also resulted in numerous accidental intoxications, and many have been lethal 28). In aquatic environments parathion hydrolyzes to yield p-nitro-phenol or oxidizes to yield paraoxon (25, 26). Baker (29) has shown that substituted phenols aflFect the odor quality of drinking water. p-Nitrophenol may be chlorinated at a water treatment plant to produce an odorous product. The U. S. Public Health Service has adopted 1 /xg/liter as a limit for phenolic compounds in water (10). Paraoxon is more toxic to insects and mammals than the parent compound parathion (27). The lethal dose (LD50) for male white rats is 14 mg/kg for parathion while that determined for paraoxon is only 3 mg/kg (30). Bioassay studies with fathead minnows indicated a Median Tolerance Limit (TLni) (96 hours) for parathion of 1.4 mg/liter and 0.3 mg/liter for paraoxon. 

A relationship was found for Ramcin spectra, however. Excunination of Raman spectra from 100 cm to 1000 cm weis done to determine if molecules with similar vibrational frequencies have similar odor quality as suggested by Wright ( ). For the stimuli here, it was found that vibrational frequencies in this range were highly predictive of the "goodness" or "badness" of the odor but they were not helpful in further differentiations of the quality. 

Approach was used in deriving mechanistic information about odor intensity as well as insight into how this biological activity may be predicted. This paper will first briefly describe the history of QSAR, the QSAR parameters used, and how substituents for QSAR studies are selected. Several examples of the Hansch Approach used in taste and odor quality studies will next be presented. The balance of the paper will deal with the development of quantitative structure odor intensity relationships which will further expand upon the earlier study reported by this author (11). For example, the use of relatively new QSAR steric parameters in correlations with odor intensity data, and correlations of log P with literature odor intensity data determined on animal panels will be presented. This will be followed by conclusions derived from those studies, and areas of future work. 

If one individual deposits a scent mark on top of the mark of another individual, then the top scent is necessarily fresher (more recent) than the scent that was deposited first. Thus, relative scent age is one way that mammals (or other species) could evaluate scent over-marks to determine which animal had marked most recently. The hypothesis that mammals use scent age as the relevant cue is attractive because it is already known that changes in odor quality may provide information about scent age. Although there has been little research that demonstrates how individuals of any species perceive or use this information, it is clear that some rodents respond differently to fresher versus older scents (Johnston Lee, 1976 Johnston Schmidt, 1979 Wellington et al., 1981 Ferkin et al., 1995a). There is also evidence suggesting that dogs may be able to determine the direction of a human scent trail by differences in scent quality due to differences in age of footprints along the trail (Steen Wilsson, 1990). 

In the case of chiral aroma substances, elucidation of the absolute configuration and determination of the enantiomeric ratio, which is usually given as the enantiomeric excess (ee), are of especial interest because the enantiomers of a compound can differ considerably in their odor quality and threshold. The compound 3a,4,5,7a-... 

Many psychophysical approaches have been proposed to obtain quantitative estimates of individual percepts. Some studies focus on measurements of threshold sensitivity [29] others focus on the use of suprathreshold stimuli [30] both can be important in determining overall impact. Interests also lie in hedonic evaluations, odor quality and odor (aroma) acceptance in the academic (understanding the workings of the brain), marketing (understanding how to influence and motivate the consumer), and corporate... 

The first element, dynamic dilution, provides a reproducible sample for each panelist. The system must minimize the loss of the odorant to the walls of the delivery apparatus, provide clean dilution air of odor-free quality, maintain a constant dilution ratio for the duration of a given test, and have no memory effect when going from high to low concentrations or switching between odorants of different character. The type of mask or port and the delivery flow rate have been found to influence the response of panelists in determining odor threshold and intensity. 

White or yellowish-white, woolly powder, prepared from the best quality of hide from which the hair has been removed with lime and which has been thoroughly washed. Hide powder should have but a slight odor and should lie specially free from odors of decomposition products. It is used for tannin determination. 

The quality of individual gums is mainly determined by color and taste or odor. Many gums are colorless when secreted, but darken on aging. Most gums are usually tasteless unless contaminated by the bitter flavors of tannins which precludes their use in foods. 

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