Designation: E679 - 04 (Reapproved 2011) INTERNATIONAL Standard Practice for Determination of Odor and Taste Thresholds By a Forced- Choice Ascending Concentration Series Method of Limits1 This standard is issued under the fixed designation E679; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. Anumber in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. INTRODUCTION The obtaining of odor and taste thresholds requires the sensory responses of a selected group of individuals called panelists. These thresholds may be determined in order to note the effect of various added substances on the odor and taste of a medium. They may also be determined in order to characterize and compare the odor or taste sensitivity of individuals or groups. It is recognized that precise threshold values for a given substance do not exist in the same sense that values of vapor pressure exist. The ability to detect a substance by odor or taste is influenced by physiologicalfactors and criteria usedinproducing a response bythe panelist.Theparameters of samplepresentation introducefurthervariations.Thus,theflowrateof agaseous,odorous samplehas an influence on the detectability of an odor. However, a concentration range exists below which the odorortasteofasubstancewillnotbedetectableunderanypracticalcircumstances,and abovewhich individualswithanormal senseof smellortastewouldreadilydetectthepresenceof the substance. The threshold determined by this practice is not the conventional group threshold (the stimulus level detectable with a probability of 0.5 by 50 % of the population) as obtained by Practice E1432, but rather a best estimate not far therefrom. The bias of the estimate depends on the concentration scale steps chosen and on the degree to which each panelist's threshold is centered within the range of concentrations he or she receives. The user also needs to keep in mind the very large degree of random error associated with estimating the probability of detection from only 50 to 100 3-AFC presentations. 1. Scope 1.4 The medium may be a gas, such as air, a liquid, such as water or some beverage, or a solid form of matter. The medium 1.1 This practice describes a rapid test for determining may be odorless or tasteless, or may exhibit a characteristic sensory thresholds of any substance in any medium. odor or taste per se. 1.2 It prescribes an overall design of sample preparation and 1.5 This practice describes the use of a multiple forced- a procedure for calculating the results. choice sample presentation method in an ascending concentra- 1.3 The threshold may be characterized as being either (a) tion series, similar to the method of limits. only detection (awareness) that a very small amount of added 1.6 Physical methods of sample presentation for threshold substance is present but not necessarily recognizable, or (b) determination are not a part of this practice, and will depend on recognition of the nature of the added substance. the physical state, size, shape, availability, and other properties of the samples. 1.7 It is recognized that the degree of training received by a I This practice is under the jurisdiction of ASTM Committee E18 on Sensory panel with a particular substance may have a profound influ- Evaluation and is the direct responsibility of Subcommitee E18.04 on Fundamen- ence on the threshold obtained with that substance (1).2 tals of Sensory Current edition approved Aug. 1, 2011. Published August 2011. Originally approved in 1979. Last previous edition approved in 2004 as E679-04. DOI: 2 The boldface numbers in parentheses refer to the list of references at the end of 10.1520/E0679-04R11. this practice. Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States 1 M E679- 04 (2011) 1.8 T