Performance of perfume

The best way of quantifying the performance of perfume materials in finished products available today is through the adjusted odor value units discussed in Chapter 13. Tables of such units are only now beginning to be constructed. Experienced perfumers, however, have tables of this kind, based upon extensive practical experience, in their heads. These mental tables may be imprecise and nonexplicit, they are nevertheless an essential tool in the perfumer s work. 

The persistence of perfume materials on human skin has been the subject of some study (Wells 1960 Jellinek 1964). But, considering the importance of evaporation, and of the attraction forces between molecules, to the performance of perfumes in all conceivable applications, it is surprising how little attention has been paid to these subjects by the perfumery profession at large. 

Gaining this sort of experience is a lifetime s work for a perfumer, but it is possible to help the process by understanding the factors that govern the physical performance of perfume. One of the challenges for the physical chemist is to be able to predict what happens when a perfume is incorporated into different products in particular, how does the composition of the perfume headspace alter, and what will be the in-use perfume behaviour (for example, how to maximize a perfume s... 

Your entire life is affected when one whiff of perfume, fabric softener or fresh paint can result in a throbbing headache, brain dysfunction, an asthma attack, a convulsion or a myriad of other symptoms. Work performance, relationships and community ties collapse when your olfactory system is so heightened that you become ill from the smell of laundry products on the clothes of someone sitting all the way across the room. Fear overcomes you when suddenly carpeting, photocopies, car exhaust and other products produce the same effects, and the only way to protect yourself is through isolation. 

Encapsulation is an elegant way of improving the performance, such as sub-stantivity, tenacity or endurance, of perfumes in washing powders, tablets or conditioners. The performance of fragrances tends to fade by evaporation, interactions with other components, oxidation and chemical degradation. Encapsulation can be the answer to various problems ... 

To do justice to this, one of the most extraordinary of perfumes, we will break our self-imposed restriction on attribution by mentioning its creator, Jean Carles, by name, since the perfume reflects so completely every aspect of his art. Carles was also a talented conjuror who kept his pupils amused with the tricks he performed with cards as well as with those he performed with perfumery materials. 

Apart from its green character the perfume is immediately characterized by the use of orris as a major component, rather than as a modifying note as in the majority of perfumes in which it occurs. Over the past few years the price of this already costly material has risen dramatically and to find the right quality for such a perfume becomes increasingly difficult. Although synthetic irone, its major ingredient exists, the performance of the natural material is hard to emulate. Methyl ionone (6%) provides a perfect link between the orris and woody materials. 

The question whether the performance of a perfume depends only upon the performance of its indivic components, or whether the art of composition is also a major contributor to performance, has been li explored even though it really is basic to perfumery. In any case the skill to forge harmonious accord from individually highly performing materials is an essential part of modem perfumery technique. 

In the late 1950s several perfumers and perfume chemists proposed that fragrance performance, in all media and applications, is largely dependent upon the rates of evaporation of the individual perfume materials under the specific conditions in which the fragrance is evaluated (Pickthall 1956 Sfiras and Demeilliers 1956 Jellinek 1959). They stressed the importance of knowing the vapor pressures of perfume materials (Appell 1964). They suggested that differences in the performance of a given odorant in different media are caused by the attraction forces between odorant and product base, and that these forces could be understood and predicted from the chemical structures of the materials involved (Jellinek 1961 Dervichian 1961). 

Although it is possible to some extent to predict the stability and performance of certain types of perfumery material in any base—for example, the instability of esters in acid media—perfumers must usually rely on the experience gained from the testing of individual perfumery materials. This is a laborious undertaking and one that occupies much of the time of both the perfumer and the application chemist. As has been mentioned earlier, such testing is normally carried out at elevated temperature as well as at ambient temperature and in the cold. 

Assessing the results of such tests requires considerable experience. It is important, for example, to differentiate between the stability of a product and its performance. A material smelled in a sample of dry detergent powder may show poor performance and yet be stable, making a valuable contribution to the performance of a perfume on washed fabric. Its failure to perform in the base, even on cold storage, should not necessarily be attributed to instability. 

Forces of mutual attraction and hydrogen bonding occur not only among the molecules of any given material but also between the different kinds of molecules that make up mixtures and solutions. They directly affect the solubility of perfume materials in different solvent systems, their odor performance in these systems, and the odor character of the solution. 

In the normal applications of perfumes, concentrations come into play that lie far above the threshold values. Nevertheless, when used in conjunction with vapor pressure data, the threshold values of individual odorants can give the perfumer helpful information about their performance. Substances with low threshold values are generally more potent in odor than substances with comparable vapor pressure (volatility) and higher thresholds. 

Table 20.1 shows the detection thresholds of a number of perfume materials in air and in water. Note the tremendous range (from 0.002 parts per billion for beta-damascenone to 10,000 parts per billion for phenylacetic acid—both taken in water solutions), the large difference between optical isomers of the same substance (e.g., Nootkatone and alpha-damascone), and the large differences in thresholds reported by different investigators (e.g., benzaldehyde and vanillin). In substances with relatively high water solubility such as vanillin and ethyl vanillin, benzaldehyde, phenylethyl alcohol, and phenylacetic acid, the thresholds in water are very much higher than in air. In poorly water-soluble substances such as pinene and the macrocyclic musk cyclopentadecanolid, the reverse is true. The relative thresholds of a substance in different solvents indicate its performance in different application environments. Substances whose thresholds in water solution are much... 

Normally, the perfumer is interested in the performance of odorants at levels well above their threshold concentrations. How strong are they or, to put it more scientifically, how intensive is their odor perceived to be The answer obviously depends on their concentration in the perfume and in the finished product the greater the concentration, the higher is the intensity. 

In the present study, we will desribet the link between the nitridation parameters and the performances of oxynitrides for the synthesis of jasminaldehyde. Jasminaldehyde (a-amylcinnamaldehyde) is obtained through the aldol condensation of heptanal with benzaldehyde, in the liquid phase. It is a fine chemical of commercial interest [2], as it is used by the flavour and perfume industry. On top of its industrial interest, the aldol condensation reaction between heptanal and benzaldehyde is an interesting test reaction to assess the acid-base properties of heterogeneous catalysts. Heptanal is more reactive than... 

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