1 Scope
This document gives guidelines for
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— obtaining data on the detection of stimuli that evoke responses to odour, flavour
and taste by a 3-AFC (three-alternative forced-choice) procedure, and
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— the processing of the data to estimate the value of a threshold and its error bounds,
and other statistics related to the detection of the stimulus.
Typically, the procedures will be used in one of the following two modes:
(Although experiments can encompass both modes.)
Examples of the first mode include studies of the differences among individuals or
specified populations of individuals in sensitivities and of the effects of age, gender,
physiological condition, disease, administration of drugs and ambient conditions on
sensitivity. Examples of the latter mode include
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— studies in flavour chemistry and the impact of specified chemicals on the flavour
of foods,
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— classification of chemicals for their impact on humans, if present in the environment,
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— studies on the relationship of molecular structure to capacity of a chemical to act
as a stimulant,
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— quality assurance of gaseous effluents and of water, foods and beverages, and
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— studies in the mechanism of olfaction.
In both modes, the way in which probability of a correct response changes with intensity
of stimulus, i.e. the slope of the dose/response curve, could be an important aspect of the study
as well as the threshold value, and the data processing procedures described here
provide this information.
The focus of this document is on data requirements and on computational procedures.
Regarding the validity of the data, the text is restricted to general rules and precautions.
It does not differentiate between detection and difference thresholds; fundamentally,
the procedures measure a difference threshold because a test sample is compared with a reference sample. Typically, the reference sample is not intended to contain the stimulus under investigation, but the guidelines do not exclude experimental design in which
the reference could contain the stimulus, or it might not be known if the reference contains the stimulus. The guidelines do not measure a recognition threshold as defined in ISO 5492. They do not address the standardization of methods of determining air quality as
discussed in EN 13725.