The application of calibrated difference-from-control for sensory quality control of distilled beverages
Sensory quality control is an essential mechanism for ensuring the sensory integrity of a product is not compromised. By conducting sensory testing throughout the distilling process it becomes possible to detect and reject faulty raw ingredients and intermediate products before these advance to the next stages, resulting in further contamination.
Many producers of distilled spirits conduct sensory quality control using the difference from control (DFC) test method. DFC assessors, usually employees, are presented with a control sample and a test sample and instructed to quantify the difference from the control on an ordered categorical scale. Amongst several trials involving test samples is a blind control sample. Conventional training involves demonstration of exemplar taints and control samples. Feedback on DFC results is provided in a delayed manner. It is not atypical for scale usage calibration and taint identification to be practiced during the initial training but not on an ongoing basis, which may diminish the overall effectiveness of the sensory quality program.
Given that incorporating immediate feedback into training has previously been observed to raise assessor engagement and reduce training times, we propose doing so in DFC training. We propose ongoing monitoring of assessor performance, with remedial and intermittent training as appropriate using spiked training targets with target responses that span the scale. Giving immediate onscreen feedback during computerized data collection in both the training and maintenance phases of the panel is recommended, with the aim of calibrating assessors, reducing biases which in particular tend to occur near endpoints, and creating a meaningful objective scale. We further propose using this objective scale to make go-no go-retest decisions, using business-relevant effect sizes to guide decisions regarding products, assessors, and further refinement of the sensory quality control program.
Castura, J. C., King, S. K., & Findlay, C. J. (2017). The application of calibrated difference-from-control for sensory quality control of distilled beverages. 6th Worldwide Distilled Spirits Conference. 29 May – 1 June. Glasgow, Scotland.