The Tetrad test is a forced choice discrimination method that has recently gained popularity in the sensory evaluation of foods. It has demonstrated superiority over the triangle test both in theory and practice with its proven relatively large statistical power. Tetrad does have one potential drawback, the use of a fourth sample that may cause panelist fatigue. There have been many studies comparing the Tetrad method with other difference tests such as triangle, 3- AFC, and 2- AFC however, there has been little research comparing the Tetrad and Degree of Difference test (DOD). This project compared the precision and power of Tetrad and DOD by measuring the flour tortilla quality from two different manufacturing lines in one commercial plant to determine if a sensory difference exists. The same group of panelists evaluated tortillas from the two manufacturing lines using the Tetrad and DOD methods. Results showed that the statistical power of Tetrad was higher then DOD at 22% and 18.5% respectively. This higher power indicates that Tetrad may be substituted for DOD to achieve its’ same power using fewer panelist. In addition, Tetrad had a smaller variance of d’ than that of DOD (0.13 vs. 0.28) suggesting that Tetrad was more precise. Therefore, Tetrad is a viable alternative to DOD in determining differences in flour tortilla quality by improving the precision and accuracy of sensory results. The subsequent reduction in the number of panelists required will also reduce the cost of product testing.
Futalan, Kristine; Toto, Criselda; and McDonald, Heather, "Comparison of Tetrad and Degree of Difference Sensory Testing Methods in Evaluating the Quality of Flour Tortillas" (2014). Student Research Day Abstracts and Posters. 61.