Odors evaluation

Initial evaluations of chemicals produced for screening are performed by smelling them from paper blotters. However, more information is necessary given the time and expense required to commercialize a new chemical. No matter how pleasant or desirable a potential odorant appears to be, its performance must be studied and compared with available ingredients in experimental fragrances. A material may fail to Hve up to the promise of its initial odor evaluation for a number of reasons. It is not at all uncommon to have a chemical disappear in a formulation or skew the overall odor in an undesirable way. Some materials are found to be hard to work with in that their odors stick out and caimot be blended weU. Because perfumery is an individuaHstic art, it is important to have more than one perfumer work with a material of interest and to have it tried in several different fragrance types. Aroma chemicals must be stable in use if their desirable odor properties are to reach the consumer. Therefore, testing in functional product appHcations is an important part of the evaluation process. Other properties that can be important for new aroma chemicals are substantivity on skin and cloth, and the abiHty to mask certain malodors. 

Subjective evaluation of odor emission is made difficult by the phenomenon of odor fatigue, which means that after persons have been initially subjected to an odor, they lose the ability to perceive the continued presence of low concentrations of that odor. Therefore, all systems of subjective odor evaluation rely on preventing olfactory fatigue by letting the observer breathe odor-free air for a sufficient time prior to breathing the odorous air and evaluating its odor content. Usually an activated charcoal bed is... 

Fontenot, J. L., Kraft Board Odor Evaluation by Gas Chromatography and... 

Odor evaluation, in perfumes, 18 379 Odor impacts, air pollution dispersion modeling for, 26 725 Odorous compounds controlling, 10 75 in wastewater, 26 723t Odor panels, 26 724 Odor pollution, 26 669 Odor removal, adsorbents for, 1 611 Odors... 

The authors show differences in aroma profiles and odor evaluation due to the effect of temperature. 

The odor of the resulting synthetic irradiated beef slurries was compared with an equal quantity of freshly irradiated and slurried beef. Comparisons were made informally by persons experienced in sensory evaluation and familiar with irradiation off-odor. It was obvious almost immediately that some of the compounds contributed little or nothing to irradiation odor, while others affected it greatly. Trial and error mixing of compounds and concurrent odor evaluation led to the opinion that when added to a slurry of 100 grams of enzyme-inactivated beef in 75 ml. of distilled water, the following mixture caused very close approximation of irradiation off-odor. 

This article will review the development and progress of analytical procedures of material odor evaluation, analysis and identification during recent years and the knowledge gained about compounds responsible for odor in the area of material science. 

Figure 8.2 Experimental set-up for material odor evaluation using an emission test chamber.

Figure 8.3 Odor evaluation scales for (a) intensity (VDI 3882-1) (b) hedonic odor tone (VDI 3882-2) and (c) acceptance (Clausen etal., 1996 Clausen, 2000).

The ideal number of untrained panelists recommended for such an investigation is between 20 and 40. Panelists can be selected and their suitability checked following ISO 8586-1 (1993). A simple test can be performed according to ISO 8587 (1988) before using them as subjects for odor evaluation as described by Clausen et al. (1996) and Wargocki et al. (2003). 

If the panelists have some experience in odor evaluation in addition they might be able to state the perceived odor quality (musty, smoky, fatty, fruity, rubber-like, etc.). 

Application of the Combination of Odor Evaluation and Odor Analysis for Product Optimization... 

The information gained by application of odor evaluation and odor analysis of indoor environment and material samples not only serves the purpose of knowledge accumulation, but can also be used as a tool for air quality and product improvement. The combination of the two methods has the potential of a systematic approach to developing odor optimized technical materials. One example is given here. 

Table 8.2 Result of the odor evaluation of an odorous and odor improved PPO.

Mair, S., Mayer, F. and Breuer, K. (2005) Comparison of the measurement uncertainty of static and dynamic odor evaluation processes. Proceedings of the 7th... 

The relevance of this chemistry is demonstrated by the sensory impressions of linseed-oil based linoleum. Jensen, Wolkoff and Wilkins (1995) studied the autooxidation products emitted from linoleum and identified saturated and unsaturated aldehydes and fatty acids. An odor evaluation of the identified 2-alkenals and the fatty acids as contributing most to odor intensity (Jensen, Wolkoff and Wilkins, 1995), although many odorous products may not be quantified by traditional analytical methods (Knudsen et al., 2007) Knudsen et al. (2007) showed that linseed oil based products exhibited a more negative sensory perception than similar product not containing linseed oil, and that the negative perception persisted for at least a year. 

Characterization of linoleum Part 2 preliminary odor evaluation. Indoor Air, 5, 38-43. 

Aznar, M., Lopez, R., Cacho, J.F., Ferreira, V. (2001). Identification and quantification of impact odorants of aged red wines from Rioja. GC-olfactometry, quantitative GC-MS, and odor evaluation of HPLC fractions. J. Agric. Eood Chem., 49, 2924-2929. 

Polymer films have been very widely applied to modify the surfaces of chemical sensors both for solution and gas phase measurements. Solution coating has been used to coat quartz crystal oscillators [91-93, 112] and SAW devices [113, 114] with various polymeric adsorbates and polymer/lipid mixtures [90, 94] to prepare arrays of sensors for use in gas sensing and odor evaluation and discrimination. 

With a wider range and number of far infrared absorption spectra and more of the requisite expert evaluations, it would doubtless be possible to extend and eventually to clarify our understanding of the complexities of human odor evaluations. The existence of these complexities is at once an obstacle and a challenge and is a consequence of the fact that the messages coming into our consciousness are complex because the molecules in which they are conveyed are themselves complex. What is important is the fact that the sensory inputs can be put in a one-to-one relation with the molecular-vibrational attributes of the stimuli that induce them. 

In many cases of odor evaluation, there are big differences between the results among the individual evaluators, since they have a widely varied background of experience. 18.1.6 MEASUREMENT OF ODOR IN MATERIALS AND INDUSTRIAL PLANTS... 

Smell There are various modes of odor evaluation. In the case of wine, it is recommended not to swirl first, as the most volatile compovmds are perceived in this way. The nature and intensity of odors is recorded according to the rating system. Successive swirling should promote release of the heavier polar compounds that are retained in the hydroalcoholic solution more than in the apolar ones. Some tasters hold the glass between the hands when the beverage is too cold. The impressions are recorded yet again. 

Table 11.26. Effect of iron fortification on pentane formation and odor evaluation of infant cereals stored for 3 months at 37°C ...

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