The aim of this research was to investigate the relationship between the odorants in the model drink and the odorants reaching the olfactory epithelium using the Retronasal Flavor Impression Screening System (R-FISS). By application of the R-FISS to the odorants in the model drink, it was found that a methylthio ether [1-methoxy-3-methyl-3-(methylthio)butane] was detected with the original volatile thiol (4-methoxy-2-methyl-2-mercaptobutane) in the air exhaled through the nostrils via the nasal cavity after the model drink (including the original thiol) had been swallowed. In addition, this phenomenon was also observed in other volatile thiols (furfuryl mercaptan, ethyl 2-mercaptopropionate, 2-methyl-1-mercaptobutane, and 4-mercapto-4-methyl-2-pentanone). These compositional changes in thiols that were observed in the air exhaled through the nostrils could be affected by the chemical structure of each tested thiol and individual differences. These results pointed to a possibility that the odorants reaching the olfactory receptor via the throat during consumption of foods could not always retain their original chemical structures and compositions in foodstuffs. Therefore, the characteristic odor of volatile thiols might be perceived due to the stimuli of multiple compounds. To understand in detail flavor perception during the consumption of foods, not only the compositions or amounts of odorants in foodstuffs but also the compositional changes in odorants induced by biological reactions (reduction or methylation) need to be taken into consideration.

The objective of this study was to develop a new approach that can be used to estimate the in-mouth release characteristics of odorants in chewing gum. This technique, called the "Retronasal Flavor Impression Screening System (R-FISS)," is based on a modified dynamic headspace gas sampling technique. By application of the R-FISS technique, the in-mouth release characteristics of odorants during the chewing of gum was indicated by the peak area ratio, which was calculated by comparing the peak area for 10 min to the peak area for 1 min, of each odorant exhaled from the human nose. In addition, a good overall regression coefficient was found for the correlation between the peak area ratios of each odorant in the model chewing gum obtained by R-FISS and the retention indices on a polar stationary phase GC column (DB-Wax). Therefore, the in-mouth release of odorants in chewing gum seems to be capable of being predicted by their RIs on a polar stationary phase GC column (DB-Wax), and these results appear to suggest that two parameters (vapor pressure and hydrophobicity/hydrophilicity) are the key factors for determining the in-mouth release of odorants from chewing gum.

The aim of this study was to investigate the influence of milk on the aroma release and aroma perception of coffee. The amounts of in-mouth odorants exhaled through the nostrils during the consumption of black coffee and milk coffee were compared using the Retronasal Flavor Impression Screening System (R-FISS) by 3 trained panelists. As a result, it was found that the amounts of most in-mouth odorants including the potent odorants in brewed coffee did not significantly differ between the black coffee and milk coffee. However, the amounts of furfuryl methyl sulfide (FMS), difurylmethane, and furfuryl pyrrole exhaled through the nostrils during the consumption of milk coffee were significantly lower than those of the black coffee regardless of the panelist. It has been previously indicated that FMS could result from the methylation of 2-furfurylthiol (FFT), one of the most important potent odorants in brewed coffee. Based on these results, FFT and FMS were added to milk coffee so that the amount of FMS exhaled through the nostrils was about the same as that of black coffee, resulting in improved intensity of the coffee-like aroma quality for the milk coffee. The present results suggested that the significantly decreased intensity of the coffee-like aroma quality might result from decreased aroma release of a few odorants, including FFT, by the addition of milk to the coffee. Moreover, it was inferred that the difference in aroma release of FFT would have an especially significant impact on the perception of coffee-like aroma quality between the black coffee and milk coffee.Keywords: flavor release, aroma release, aroma perception, retronasal aroma, R-FISS, coffee, milk IntroductionFlavor release from food has been acknowledged as an important factor in determining the perceived flavor quality of various foods. It is well-known that aroma perception is the result of odorant/receptor interactions that take place in receptors on the olfactory epithelium in the human nasal cavity. Therefore, in order to understand aroma perception during eating and drinking, it is important to determine the composition and amounts of odorants that reach the olfactory epithelium from foodstuffs or their behavior (Taylor and Roozen, 1996;Taylor and Linforth, 1997). In order to analyze the odorants exhaled through the nostrils, several analytical techniques have been developed, such as nosespace analysis by APCI-MS , PTR-MS (Roberts et al., 2003a), EXOM (Buettner and Schieberle, 2000), and R-FISS (Kumazawa et al., 2008). These analytical techniques have been used to reveal the relationship between the intensity of the aroma perceptions and the aroma release during the consumption of foods and drinks (Gwartney et al., 2000;Hollowood et al., 2000;Lethuaut et al., 2004;Linforth et al., 1999;Mestres et al., 2005;Saint-Eve et al., 2009;Weel et al., 2002). In addition, Beauchamp et al. and Fransnelli et al. also developed other analytical techniques capable of analyzing the odorants passing through the nasopharynx and reaching the olfactory ...

The aim of this study was to investigate the relationship between the influence of sweeteners on the in vivo aroma release from beverages and aroma perceptions. Equi-sweet and lemon-flavored model beverages were prepared using sucrose, acesulfame potassium (ACK), aspartame (ASP) and sucralose. The amounts of in-mouth odorants exhaled through the nostrils during the consumption of the model beverages were compared using the Retronasal Flavor Impression Screening System (R-FISS) by 4 trained panelists, and the relationship between the in vivo aroma release and their aroma perceptions was evaluated. As a result of the sensory evaluation using quantitative descriptive analysis, the lemon-like aroma of the beverage containing ACK was perceived to be significantly weaker, while the green aroma of the beverage containing sucralose and the spicy aroma of the beverages containing ASP and sucralose were perceived as significantly stronger than the other beverages. In contrast, there were no in-mouth odorants showing significant differences in their amounts that were common to the 4 panelists. Therefore, it was found that the sweeteners could have a small impact on the in vivo aroma release from the model beverages. These results suggested that differences in aroma quality of the model beverages by the types of sweeteners could result from factors other than the in vivo aroma release. Furthermore, it is highly likely that the taste-aroma interactions caused by the aroma and taste compounds would be one of the factors having a significant impact on the different aroma perceptions of the beverages containing the different sweeteners.

The aim of this study was to develop a new approach that can be used to estimate the elution characteristics of odorants from chewing gum into saliva during chewing using a chewing apparatus and to apply the approach to the prediction of their elution ratios. The odorants eluted from the model chewing gum were analyzed by a gas chromatography-flame ionization detector using the adsorptive column method and Headspace-solid phase microextraction (HS-SPME). It was found that the quantitative data obtained from each analytical method are in proportion and that the measured value obtained from HS-SPME, which is easy to operate, could convert the quantitative data obtained from the adsorptive column method. Therefore, it was demonstrated that the amounts of odorants eluted from chewing gum and their release curves could be easily determined by a combination of the two methods. In addition, it was recognized that there was a good overall regression coefficient between the elution ratio of the odorants in the model chewing gum after a 20-min chewing run and the difference between the retention indices on the polar and apolar stationary phase of GC columns (ΔI). Therefore, ΔI is the most important factor for predicting the elution ratio of odorants in chewing gum during chewing.Keywords: flavor release, elution characteristic, chewing gum, chewing apparatus *To whom correspondence should be addressed. E-mail: itobe.takafumi@ogawa.net IntroductionFlavor is one of the primary factors determining the quality of a foodstuff. Flavor is a more important factor for the quality of chewing gum than for that of other foodstuffs, because the flavor of chewing gum is strongly required as an excellent characteristic of in-mouth release, which is the immediate flavor impression and the duration of perception of odorants during chewing, in addition to an excellent odor quality and an appropriate intensity. The sensory response to an added flavor in chewing gum is mainly affected by the rate and extent of the in-mouth flavor release during consumption, and the driving forces of the release are the partition between the different phases (chewing gum -saliva -air) and mass transfer velocity (De Roos, 1990;De Roos, 2000;Harrison, 2000). Therefore, detailed understanding of the in-mouth release characteristics of odorants in chewing gum during chewing is extremely important for the production of high quality chewing gum products.