Odor value

The sesquiterpenes found in essential oils have low volatilities compared with monoterpenes and so are isolated mainly by steam distillation or extraction, but some are also isolated by distillation or crystallization. Most of the sesquiterpene alcohols are heavy viscous Hquids and many crystallize when they are of high enough purity. Sesquiterpene alcohols are important in perfume bases for their odor value and their fixative properties as well. They are valuable as carriers of woody, balsamic, or heavy oriental perfume notes. 

Patchouli alcohol. Patchouli oil comes from Pogostemonpatchouli and the main constituent is patchouli alcohol [5986-55-0] (105) or patchoulol. Another component of the essential oil is norpatchoulenol (106), a norsesquiterpene derivative as a minor (3—5%) constituent, important ia determining the overall odor of the essential oil (197). The price of patchouli oil ia 1995 was 20.90/kg from Indonesia (69). Alarge proportion of the oil (40—60%) is comprised of sesquiterpene hydrocarbons that do not have much odor value. World production of the oil was at about 750 t ia 1984. It is valuable ia perfumery bases because of its characteristic woody, herbaceous odor (198). 

Although the behavior of the base perfume, and thus the odor value (OV) of each component, can be known, the OV in the new mixture will change because the OV depends largely on the solvent and the remaining aromatic components present in the perfume mixture. This is due to molecular size and in great extent to physical interactions at the molecular level, such as polarity forces (i.e. ion-dipole, dipole-dipole, hydrogen bonding forces, and others), in other words to the structure. 

The intensity of a fragrant compound i can be expressed in terms of its odor value, OVj, which is defined as ... 

Consider that the odor perception by human nose is correlated with the odor value, OVj, in the headspace above the liquid. If a specific OVt distribution values is wanted, the perfume composition can be determined with the help of Equation (2). This methodology can facilitate the optimization of perfume compositions, reducing in this way some trial and error time and chemical wastes. Clearly, the problem is determined by structural decisions because the perfume composition depends on the interaction of the different perfume components. 

For estimating the contribution of volatile compounds to bread aroma Rothe and coworkers (S) defined "aroma value" as the ratio of the concentration of some volatile compounds to the taste threshold value of the aroma. This concept was further developed by Weurman and coworkers (9) by introducing "odor value", in which aroma solutions were replaced by synthetic mixtures of volatile compounds in water. These mixtures showed the complexity of the volatile fractions of wheat bread, because none of them resembled the aroma of bread. Recently two variations of GC-sniffing were presented (10-11), in which the aroma extract is stepwise diluted with a solvent until no odor is perceived for each volatile compound separately in the GC effluent. The dilution factors obtained indicate the potency of a compound as a contributor to the total aroma. 

ODOR. An important property of many substances, manifested by a physiological sensation caused by contact of their molecules with the olfactory nervous system. Odor and flavor are closely related, and both are profoundly affected by submicrogram amounts of volatile compounds. Attempts to correlate odor with chemical structure have produced no definitive results, Objective measurement techniques involving chromatography are under development. Even potent odors must be present in a concentration of 1,7 x I07 molecules/cc to be detected. It has been authentically stated that the nose is 100 times as sensitive in detection of threshold odor values as the best analytical apparatus. 

A more general approach to estimate the importance of a flavor compound in a particular food is the calculation of the ratio of its concentration to its flavor (odor and taste) threshold (9) or to its odor threshold (1 , 11) The result is denoted "aroma value" 19), "odor unit" (10) or "odor value" (11) the higher the value or unit, the more intensely this component contributes to the flavor or odor of the food. 

To get an insight into the compounds of the synthetic mixture that cause the fermentation odor, Mulders (11) calculated their odor values. Acetaldehyde showed the highest odor value followed by dimethyl disulfide, ethanol, 2-methylpropanal and 3-methylbutanol. 

The "perfumery grade" qualities of geraniol from the two sources actually have considerable differences in odor value because neither is chemically pure. Geraniol from a natural source contains small amounts of many other materials carried over from the source material. Synthetically produced geraniol is a reaction mixture, frequently containing a large proportion of nerol and other substances not found in the natural product. 

Inherent Odor Strength, Odor Value and Odor Volume... 

Odor values are only approximate relative measures of intensity and performance the reasons for this are explained in Chapter 20. A more realistic but still rough measure of intensity is the adjusted odor value OV which we define as... 

We can define the inherent odor strength of a perfumery material as its adjusted odor value in its undiluted state at room temperature. Table 13.5 provides such values for a few selected materials. 

An illustration of the use of odor values as measures of performance in a specific application is given in Fig. 13.2. The ten odorants were all present at the same level (3.6%) in the model mixture that was incorporated in the fabric softener. However, their odor values in the head space over the fabric softener differ, from the most effective (Aldehyde C12 MNA) to the least effective (phenylethyl alcohol), by a factor of several thousand. The differences are even more pronounced in the wet, the dry, and the rewetted laundry. 

As a rough indication of relative cost effectiveness in a given application, the "cost per unit of adjusted odor value" may be calculated. Table 13.6 shows these costs for the ten odorants in the example shown in Figure 13. 2, both for the odor over the fabric softener, which comes into play when a prospective buyer sniffs at the product before deciding whether to buy it, and for the headspace over the rewetted laundry,... 

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 odor value (OV) concept and its uses were discussed in Chapter 13. The odor value, being defined as... 

Obsession, 103,105, 123,125-126,139, 270 Odor effects diagram, 151 Odor intensity, related to concentration, 247-249 Odor strength, inherent, 163. 166 Odor value, 163,166, 249-259 Odor volume, 152. 153. 162 Olfaction anatomy, 76 evolution, 75 and odor recognition, 25 Olfactometer, 244 Olfactory sensitivity, see Sensitivity... 

Formaldehyde odor values of below 500 ppm, as measured by AATCC Test Method 112-1979, are normal on finished fabrics which have been treated with DANSET JS. Formaldehyde odor in the finishing plant is also low with DANSET JS. 

Odor thresholds of some organic compounds in foods and beverages were reported by Guadagni et al. (78). The odor thresholds were measured in aqueous solutions. They applied this method for measuring odor value, which is expressed as the odor concentration divided by the odor threshold. 

For individual named eompoimds, additional information eomprises synortyms, unique identifiers (CAS registry number, FEMA GRAS number, etc ), molecular weight and molecular formula molecular stractures are also shown when available. More than 18,500 Kovats Retention Indices are given, on four types of gas chromatographic columns (differing in polarity). Finally, approximately 2800 odor values are cataloged. 

Compound positively identified by comparison of RI values, odor values, and mass spectum with reference compound. 

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