Odor qualities from component

This procedure allows the differentiation of odor active compounds from odorless substances within a complex mixture of volatiles. For decades this procedure has been successfully applied for aroma analyses of foods (Grosch, 1993). The mixture of volatile compounds either collected in a purified organic solvent extract or in a defined headspace volume is separated into its different components by means of GC and the effluent gas flow at the end of the GC capillary column is split between a FID and an experienced test person s nose. By sniffing the column effluent, the human nose is able to perceive the odor active compounds contained in a complex mixture and the test person can mark the corresponding spot in the FID chromatogram recorded in parallel and attribute a certain odor quality. A sample GC—O chromatogram of a solvent extracted material is shown in Figure 8.7. 

Figure 24.3 Temporal analysis of responses measured simultaneously in five different antennal lobe neurons in the moth Manduca sexta. The matrices show patterns of neural synchrony evoked by either of two pheromone components or a binary mixture at two concentrations. The number of synchronous events was averaged over 20 trials and calculated for 500 ms from stimulus onset. The gray scale ranges from 0 to 3.8 coincident spikes per stimulus. The horizontal displays below the matrices show the averaged spiking rate in each single neuron (gray scale ranges from 0 to 5.5 spikes per stimulus period). Neural synchrony was influenced not only by the odor quality but also by both stimulus intensity and blend interactions (redrawn from Christensen eta ., 2000).

It is well known that the aroma extract dilution analysis (AEDA) is a nsefnl method for the recognition of the odor quality and odor intensity of each component." Especially the AEDA is a useful method for the identification of trace amonnts of the component that significantly affects the flavor of tea drinks. The odor intensity of the flavor component is expressed by the flavor dilution (ED) factor, that is, the ratio of the concentration of the flavor component in the initial extract to its concentration in the most dilnte extract in which odor was detected by gas chromatography-olfactometry (GC-0). Therefore, hereafter, from the viewpoint of sensory evalnation, the change in the flavor of tea drink dnring heat processing by AEDA will be mainly discnssed. Furthermore, in order to inhibit flavor deterioration of tea drink, the stndy of flavor precnrsor in a variety of foods, including tea drinks, will be proposed. 

Acyclic terpene and sesquiterpene alcohols occur in many essential oils. These alcohols were formerly isolated from oils in which they are major components. Currently, large-scale synthesis of terpenoids permits production without the uncertainties associated with isolation from natural sources. However, the odor qualities of synthetic products often differ from those of compounds isolated from natural sources, since the desired natural product often is not separated from small amounts of compounds with similar physical properties but different odor quality. 

POs have become crucial materials not only for low-cost packaging, but also for durable and semi-durable automotive and medical components. The surface aesthetics of these molded or extruded PO products are attractive and consumer-friendly in a number of uses. But these products aesthetic qualities can be harmed by abrasive handling, moisture, or microscopic organisms. Even the odor coming from a PO product s surface might need to be modified for its end use. 

As has previously been reported for rabbits (Goodrich et al., 1978), mice also responded consistently at the front, and on the tail, of some large chromatographic peaks (see Fig. 7). Since odor quality is often dependent on the concentration of eluting volatiles, presentation of odor components in concentrations which vary greatly from those which mice would perceive under natural conditions could result in false behavioral responses in the animals. 

Rose Rose is one of the most important florals in perfumery, the most valuable derivatives of which are produced from Rosa damascena, which is grown principally in Bulgaria, but also in Russia, Turkey, Syria, India, and Morocco. The concrete, absolute, and steam-distilled essential oil (rose otto) are particularly valuable perfume ingredients. Careful handling and processing of freshly picked flowers are required to produce materials of warm, deeply floral, and rich odor quality. They are complex mixtures of which citronellol (9), geraniol (8), phenethyl alcohol [60-12-8] (24), and (3-damascenone [23726-93-4] (25) (trace component) are important odor constituents. 

Our neurophysiological studies have focused on three important properties of the sex-pheromonal signal its quality (chemical composition of the blend), quantity (concentrations of components), and intermit-tency [owing to the fact that the pheromone in the plume downwind from the source exists in filaments and blobs of odor-bearing air interspersed with clean air (47, 48)]. Each of these properties of the pheromonal message is important, as the male moth gives his characteristic behavioral responses only when the necessary and sufficient pheromone components A and B are present in the blend (44), when the concentrations and blend proportions of the components fall within acceptable ranges (49), and when the pheromone blend stimulates his antennae intermittently (39, 50). In our studies, we examine how each of these important aspects of the odor stimulus affects the activity of neurons at various levels in the olfactory pathway. 

Certain aroma components from fruits are responsible for the characteristic odor of many wines. An example is the typical aroma of many V. labrusca grapes which often gives their wines a distinctive aroma and flavor. Furthermore, some volatile constituents are characteristic of certain varieties and their wines are recognized by these distinctive aromas. This is significantly important for varietal wines (grape) where their distinct aromas are a prerequisite in rating the quality at the highest level. In addition to the importance of variety in the aroma and flavor of wines, other variables known to influence the volatile components within the fruit variety are maturity, location, climatic conditions, and cultural practices. 

Flavor is the complex effect of three components taste, odor, and feeling factors. It is usually associated with the pleasure of savoring food or beverages and has, subsequently, suffered from considerable imprecision in definition. Flavor is a sensation with multidimensional components involving subjective and objective perceptions. The sensory perceptions are both qualitative as well as quantitative and, therefore, can be measured. Webster s New Collegiate Dictionary defines flavor as the ... quality of something that affects the sense of taste,. .. the blend of taste and smell sensations evoked by a substance in the mouth. This definition is correct, but incomplete, and should be redefined to include feeling factors. 

In situ conversion of essential N A flavor components from one molecular form to another, as a result of ion pairing, is common in food and drug products. Therefore, the inadvertent conversion of flavors between types during drug formulation studies (e.g., effect of pH, salts, and temperature) can present a serious challenge in flavor-quality assessment. The fact that one and the same N A flavor component can deliver several flavor and odor impressions implies that a blend of several flavor compounds would be preferable. Such blends show improved stability. In addition, flavor impressions from N A flavor blends are usually... 

As for the potent odorants in green tea (sen-cha) drinks, the eleven components shown in hgure 17.7 are found to be important contributors to its characteristics. Using the AEDA method, the characteristic sulfur components, such as 4-methoxy-2-methyl-2-butanethiol, 4-mercapto-4-methyl-2-pentanone, and methional, were identihed from the green tea for the first time. Among these eleven components, P-damascenone and methional were reported to increase after the heating process (hgure 17.4), then theorized to have a remarkable effect on the tea drink quality. 

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