The discrimination of thousands of odorants is mediated by several hundred olfactory receptors (ORs). It is generally accepted that the main strategy in encoding odor quality is a combinatorial receptor code scheme, in which odorants are discriminated by different sets of ORs. In the present study, we classified 12 test odorants by their receptor codes and perceived odor qualities to examine whether odorants showing similar receptor codes are also similar in their odor qualities. Similarities of receptor codes between odorants were estimated by the overlapping responses of murine isolated olfactory sensory neurons. In contrast, we conducted a human sensory test to classify the test odorants according to their odor qualities. Despite the difference in species, the groupings of the test odorants were well conserved between receptor code and odor quality. These findings indicate that odorants that are discriminated by murine receptor codes are perceived as different odors by humans and further suggest that similarity of receptor codes correlates with that of odor quality, at least in our test odorants at the concentrations tested.

An extraction method using a high vacuum distillation extraction apparatus coupled to a canister was newly developed for the analysis and sensory test of tobacco leaf volatiles. We extended the application of the canister that is used in environmental analysis, to the extraction of the aroma components in tobacco leaves. The volatile components with vapor pressures higher than 0.1 mmHg were easily evaporated under decompression and then trapped into the vacuumed canister. After the collection of volatiles, the canister was pressurized by a slow stream of inert gas in order to emit the whole aroma under a controlled flow. Applying a preconcentrator--gas chromatography/mass spectrometry (GC/MS) and sensory test to the headspace gas components, the aroma alteration between 0 and 2 weeks of storage was simultaneously or individually evaluated. As a result, after the storage, alcohols such as 1-hexanol, linalool, and benzyl alcohol decreased significantly. The amount of carotenoid derivatives that have the characteristic tobacco leaf aroma had not changed. Sensory evaluation of the same headspace gas with that used for GC/MS demonstrated the alternation of the aroma quality before and after storage. The main changes were the decrease of greenness and smoothness in aroma and the decrease of ethylbenzene, 2-pentylfuran, 1-hexanol, benzaldehyde, and linalool concentrations.

Single puffs of cigarette smoke with a wide continuous range of volatility are directly analyzed using a new system. The system consists of a smoking machine, an online thermal desorption system (TDS), and a multidimensional gas chromatograph-mass spectrometer (MDGC-MS) system. The online TDS with the smoking machine collects the single-puff cigarette smoke with glass beads as the cryogenic adsorbent. The MDGC is composed of three capillary columns, Poraplot Q, and DB-WAX for separation and a deactivated capillary column for pressure balance, which enables simultaneous separation of the two different phases. The smoke desorbed from the TDS is divided into vapor and semivolatile phases and analyzed individually with each column by the MDGC. Thus, the system enables the overall analysis of the two phases simultaneously, including acetaldehyde and 1,4-benzenediol. This system also provides more appropriate analysis for compounds crossing the two phases such as toluene and pyridine. For the approach of introducing internal standards, a gas mixture of toluene-d(8) and o-xylene-d(10) is applied and the compounds are detected in the vapor and semivolatile phases, respectively.

We developed an internal standard-based method to analyze the vapor phase components of mainstream smoke. This method collects vapor phase components from sample cigarettes, which are smoked by a linear automatic smoking machine in a sampling bag. An internal standard gas was introduced to the bag. A 6-port valve with a 2-ml sampling loop was placed between the vapor phase smoke outlet of the smoking machine and the bag to regulate the volume of the internal standard. The mixed gas sample was then introduced, by an automatic injection device developed in-house, to a gas chromatograph (GC) for ten successive analyses. The sample in the bag was analyzed every two hours to assess the time serial changes of vapor phase smoke components as well as of the internal standard. After 18 hours, in the tenth analysis, the amounts of 37 vapor phase components decreased by less than 5 % from those in the first analysis. The repeatability of the sample analysis was assessed and 45 vapor phase components had coefficients of variation of less than 5 %. The overall reproducibility of this method including tobacco samples and instruments was also assessed using five other sampling bags and achieved coefficients of variation of less than 6 % for 42 vapor phase components. The advantages of this method include capability to handle 10 tobacco samples in a serial manner, capability to collect both the vapor phase and semivolatile components, and precise, easy and continuous component analyses. We also present the results of multivariate analyses for the vapor phase and semivolatile components from 59 sample cigarettes.