Furthermore, the absolute-value smell will compare the data from an electronic nose with the data from other electronic noses. The data from current electronic noses are relative values, since they have different sensors in each nose. The concept of absolute value smell is applicable to other electronic noses and will help gather data and build data bases. For more useful information, selection of appropriate standard gasses remains as one of the key issues to be clarified. In this study, we selected the gasses from odorants related to environment offensive odours. In order to detect odorant from microorganisms sharply, GC or GC/MS data in past and current odour studies will support the selection. Although we examined only yeast and lactic acid bacteria in this report, if scientists continue to collect smell data from different microorganisms using these methods, the resulting database will undoubtedly prove helpful in improving the safety and quality control of foods and drink. To compare and assemble such smell References 1. Tanaka T, Muramatsu K, Kim H, Watanabe T, Takeyasu M, et al. (1998) Comparison of Volatile Compounds from Chungkuk-Jang and Itohiki-Natto. Biosci Biotechnol Biochem 62: 1440–1444. 2. Centeno JA, Tomillo FJ, Fernandez-Garcia E, Gaya P, Nunez M (2002) Effect of Wild Strains of Lactococcus lactis on the Volatile Profile and the Sensory Characteristics of Ewes’ Raw Milk Cheese. J Dairy Sci 85: 3164–3172. 3. Natale CD, Paolesse R, D’Amico A (2003) Food and Bevarage Quality Assurance. In: Pearce TC, Schiffman SS, Nagle HT, Gardner JW, eds. Hand- book of Machine Olfaction: Electronic Nose Technology. Weinheim, Germany: Wiley-VCH. pp 505–524. 4. Persaud KC, Dodd G (1982) Analysis of discrimination mechanisms in the mammalian olfactory system using a model nose. Nature 299: 352–355. 5. Buck L, Axel R (1991) A novel multigene family may encode odorant receptors: A molecular basis for odor recognition Cell 65: 175–187. 6. Lancet D, Ben-Arie N (1993) Olfactory receptors. Curr Biol 3: 668–674. 7. Dryer L, Berghard A (1999) Odorant receptors: a plethora of G-protein-coupled receptors. Torends Pharmacol Sci 20: 413–417. 8. Axel R (1995) The molecular logic of smell. Sci Am 273: 154–159. 9. Keshri G, Voysey P, Magan N (2002) Early detection of spoilage moulds in bread using volatile production patterns and quantitative enzyme assays. J Appl Microbiol 92: 165–172. 10. Gibson TD, Prosser O, Hulbert JN, Marshall RW, Corcoran P, et al. (1997) Detection and simultaneous identification of microorganisms from headspace samples using an electronic nose. Sens Actuat B 44: 413–422. 11. Tanaka M, Aguri H, Nonaka A, Kataoka K, Nagata H, et al. (2004) Clinical Assesment of Oral Malodor by the Electronic Nose System. J Dent Res 83: 317–321. 12. Gardner JW, Craven M, Dow C, Hines EL (1998) The prediction of bacteria type and culture growth phase by an electronic nose with a multi-layer perception network. Meas Sci Technol 9: 120–127. Real-Value & Metaphor Smell data, we believe that the key is using absolute values and propose the use of our combination method for the measurement of smells to assemble these databases. Acknowledgments We thank Dr. Tadayoshi Tanaka (Kyoritsu Women’s University) for his useful advice regarding volatiles produced by bacteria. Ms. Miki Noji (Tokyo University of Agriculture) for providing useful bacterial knowledge and Mr. Kazuyuki Ito (IMCJ) for helping us to revise our manuscript. Author Contributions Conceived and designed the experiments: EA JiK YA TO YM KY. Performed the experiments: JiK YA TO. Analyzed the data: KF JiK YA. Contributed reagents/materials/analysis tools: JiK YA TO. Wrote the paper: KF KY. 13. Rakow NA, Susllck KS (2000) A colorimetric sensor array for odour visualization. Nature 406: 710–713. 14. Rock F, Barsan N, Weimar U (2008) Electronic Nose: Current Status and Future Trends. Chem Rev 108: 705–725. 15. Thaler ER, Kennedy DW, Hanson CW (2001) Medical Applications of Electronic Nose Technology: Review of Current Status. Am J Rhinol 15: 291–295. 16. Pavlou A, Turner APF, Magan N (2002) Recognition of anaerobic bacterial isolates in vitro using electronic nose technology. Lett Appl Microbiol 35: 366–369. 17. Winquist F, Hornsten EG, Sundgren H, Lundstorm I (1993) Performance of an electronic nose for quality estimation of ground meat. Meas Sci Technol 4: 1493–1500. 18. Schweizer-Berberich PM, Vaihinger S, Gopel W (1994) Characterisation of food freshness with sensor arrays. Sens Actuat B 18–19: 282–290. 19. Capone S, Distante C, Francioso L, Presicce D, Taurino AM, et al. (2005) The electronic nose applied to food analysis. J Argent Chem Soc 93: 123–135. 20. Fechner GT (1966) Elements of Psychophysics. Adler HE, translator; Howes DH, Boring EG, editors. New York: Holt, Rinehart & Winston. 286 p. 21. Kita J, Aoyama Y, Kinoshita M, Akamaru H, Okada M (2007) Role of ‘‘FF-2A’’ Electronic Nose and its Applications - focusing on Odor Monitoring. Shimadzu Rev 64: 63–73. 22. Aoyama Y (2006) An electronic nose and application to smell evaluation of food and dink by it. J Integrated Study Dietary Habits 17: 266–270. 23. Dubourdieu DT, Tominaga T, Masneuf I, Peyrot des Gachons C, Murat ML (2000) The role of yeasts in grape flavor development during fermentation: the example of Sauvignon blanc. Seattle, WA. pp 196–203. PLoS ONE | www.plosone.org 5 November 2009 | Volume 4 | Issue 11 | e7939