|
Measurement of the relative pleasantness/unpleasantness of odours is another valuable assessment in some circumstances.
Hedonic Tone assessments according to VDI3882 (modified)
The German guidelines VDI 3882 Olfactometry; Determination of Hedonic Odour Tone was used as a basis for the assessment of hedonic tone of selected samples from each days sampling.
The guideline calls for a group at least 15 assessors, the assessors sensitivity is not a criterion for panel selection, to be used and 6 presentations of the odour sample be made to the assessors. The concentrations presented should be the mean odour threshold concentration and 5 higher concentrations steps that differ by a factor of approximately two. The diluted sample can be presented in any order. The responses to the stimuli are recorded by the assessors on a category scale -4 to +4. Extremely unpleasant is -4, zero is neither pleasant nor unpleasant and extremely pleasant is +4.
The hedonic tone assessments made for this work used the odour panel that had made the odour concentration determination thus between four and six assessors were used and they were selected for their sensitivity to n-butanol according to the criteria in BSEN13725. Eight presentations of each sample at a step factor of approximately 1.75 were made inorder to span the same range of concentrations as 6 presentations at a step factor of 2. The forced choice olfactometer was used to present the sample randomly from the right or left horn, the assessor had to select the correct horn and evaluate the odour according to the category scale.
The results are presented in the form of a graph that shows the mean panel responses to the odour concentration presented.
The last three services are outside the scope of the UKAS accreditation.
|
