1. Staff photo Objective Assessment of the Influence of Low Impact Odorants in Mixtures Via Model Neurological Studies D. Ryan 1, J. B. Thomas 1,3,4, M. Dubaj 2, J. Patterson 2, P. D. Prenzler 1, A. J Saliba 1,3 1 National Wine and Grape Industry Centre, Charles Sturt University, Australia. 2 Swinburne University of Technology, Australia. 3 School of Psychology, Charles Sturt University, Australia. 4 School of Social Work, Charles Sturt University, Australia. ACKNOWLEDGEMENTS This work was supported by the Winegrowing Futures Program, a joint initiative of the Grape and Wine Research and Development Corporation (GWRDC) and the National Wine and Grape Industry Centre (NWGIC). INTRODUCTION Low impact odorants are generally considered unimportant in aroma perception, however there is evidence that suggests such compounds are significant in global odour perception (e.g. Escudero et. al. 2004). Gas Chromatography- Olfactometry (GC-O) is commonly used for the analysis of odour extracts; however low impact odorants cannot be detected at the olfactory sniff port. ‘Reconstruction discrepancy’ (Bult et al. 2001) describes the phenomenon that the perceived smell of GC-O reconstructed mixtures differ from that of the original aroma of the whole sample, despite the fact that concentrations of the key odorants are identical in both mixtures. The purpose of the present study was to objectively assess how low impact odorants modify the perception of the high impact odorants in an odour mixture through sensory and neurological model studies (Ryan et al. 2008). REFERENCES Bult, J. H. F., Schifferstein, H. N. J., Roozen, J. P., Voragen, A. G. J., & Kroeze, J. H. A. (2001). The influence of olfactory concept on the probability of detecting sub- and peri-threshold components in a mixture of odorants. Chemical Senses, 26, 459-469. Clark, D. L., Boutros, N. N., & Mendez, M. F. (2010). The Brain and Behavior: An introduction to Behavioral Neuroanatomy. Cambridge University Press, Cambridge. Escudero, A., Gogorza, B., Melus, M. A., Ortin, N., Cacho, J., & Ferreira, V. (2004). Characterization of the aroma of a wine from Maccabeo. Key role played by compounds with low odor activity values. Journal of Agricultural and Food Chemistry, 52, 3516-3524. Ryan, D., Prenzler, P. D., Saliba, A. J., & Scollary, G. S. (2008). The significance of low impact odorants in global odour perception. Trends in Food Science & Technology, 19, 383-389.. Participant Number Odour Presentation Perceived Aromas 1ABCSweet smell; Sunscreen and coconut; Not sweet and woody. 2CBACoconut/timber; Floral/Disinfectant; Mint/herbaceous/citrus. 3BACUse socks/aldehydes; Not fruity or grassy but more pleasant. 4CABStrong floral (rose); Weaker floral (rose). 5BCA Perfume, Juicyfruit/sharp; Plant-like/musty; A mixture of juicyfruit and plant-like. 6ACB Banana; Cleaning solution/chemical; Faint and indistinguishable scent. Table 1: Participants' perceived aromas METHODS AND MATERIALS The participants included six male staff of Charles Sturt University. In order to continually monitor brain activity, participants were connected to a 64 channel electroencephalogram (EEG) while they were exposed to three aroma treatment conditions. At least 40 presentations of each odorant was delivered, and at least one control stimulus was delivered between each odour stimulus. Participants were then asked to report on their perceptions. A combination of the two allowed comparison between subjective self-report responses and objective neurological responses to the aromas. The three aroma treatment conditions were: A) isoamyl acetate (fruity), B) whiskey lactone (woody), and C) isoamyl acetate with a sub-threshold level of whiskey lactone (altered fruity). SUMMARY The present study found that the perception of isoamyl acetate (fruity) was modified due to the presence of sub threshold concentration of whiskey lactone (altered fruity), and that fruity, woody and altered fruity aromas were perceived differently in the brain. These results were clearly demonstrated using “objective” neurological monitoring via EEG; results from “subjective” sensory evaluation were not clear cut. It is important to note that the present study was a pilot study and that further analysis is required in order to corroborate the current findings. However, this work not only highlights the importance of low impact odorants in global aroma perception, but the value of objective neurological monitoring in sensory evaluation. RESULTS AND DISCUSSION Within each treatment condition, differences were observed between the EEG responses to the odorant and an odourless control stimulus, essentially validating the measurement technique. Additionally, differences were observed between the EEG responses to ‘fruity’ and ‘altered fruity’ conditions in the frontal and left temporoparietal scalp regions. This result indicates that perception was influenced by the presence of the sub- threshold compound. Importantly, the brain area activated has previously been implicated in the processing of sensory information (see Clark, Boutros & Mendez, 2010). Differences in EEG responses to ‘woody’ and ‘altered fruity’ conditions were also observed, though this was to be expected as the two primary compounds were different. Participants perceived aromas can be located in Table 1. Olfactory sniff port Teflon® bag