Duo, trio and tetrad methods: Is there a difference? H L de Kock Institute for Food, Nutrition & Wellbeign

unwanted change in the product Balance the risk cost saving unwanted change in the product Operations has identified a process change that offers the potential for substantial cost savings. Quality Control is concerned that the change may be noticeable to consumers and would represent a risk to business. To determine if a sensory difference can be perceived between products made using the two processes. 7 May 2019

Product with cost saving B Standard A Product with cost saving B We want to make a change to our product but we do not want consumers to notice. Will they notice? Difference Similarity 7 May 2019

What are the options? Paired comparison: Same-different Triangle test/ 3 Alternative Force Choice Duo-trio test Tetrad 7 May 2019

Paired comparison: Same-different You have received two tomatoes. Taste the tomatoes in the order presented and tick a box to indicate whether the tomatoes are the same or different. 348 912 SAME DIFFERENT We want to make a change to our product but we do not want consumers to notice. Will they notice? Difference Similarity 7 May 2019

Same/Different A B AB BA AA BB 7 May 2019

Triangle test/3 AFC You have received three tomatoes. Two of the tomatoes are the same and one is different. Taste the tomatoes in the order presented and circle the code of the tomato that is different from the other two. 348 912 We want to make a change to our product but we do not want consumers to notice. Will they notice? Difference Similarity 556 7 May 2019

Triangle/3 AFC AAB BBA ABA ABB BAB BAA 7 May 2019

Duo-trio You have received three tomatoes. One of the tomatoes is a reference sample (R). Taste R first, and then taste the two coded tomatoes in the order presented. Circle the code of the tomato that is most similar to R. R 912 We want to make a change to our product but we do not want consumers to notice. Will they notice? Difference Similarity 556 7 May 2019

Duo-trio RA AB BA 7 May 2019

Duo-trio RA AB BA RB 7 May 2019

Group the tomatoes in two groups of two based on similarity. Tetrad You have received four tomatoes. There are two groups of two similar tomatoes. Taste the tomatoes in the order presented. Group the tomatoes in two groups of two based on similarity. 348 912 Group 720 556 We want to make a change to our product but we do not want consumers to notice. Will they notice? Difference Similarity 7 May 2019

Tetrad AABB BBAA ABAB ABBA BABA BAAB 7 May 2019

The tetrad test is more efficient statistically than the triangle test or the duo-trio test. Tetrad > Triangle > Paired/Duo trio Practically, four vs three vs two samples 7 May 2019

Tetrad - steps Clearly define the test objective. Choose the number of assessors based on the sensitivity desired for the test. The sensitivity of the test is a function of three values: the risk of declaring the samples different when they are not (i.e, α-risk) the risk of not declaring the samples different when they are (i.e, β-risk). the maximum allowable sensory difference, δ Acceptable values of α and β vary depending on the test objective and should be determined before the test . 7 May 2019

Prior to conducting the test, select values for α, β, and δ 0 to 5 % (0.10 to 0.05) indicates “slight” evidence 5 to 1 % (0.05 to 0.01) indicates “moderate” evidence 1 to 0.1 % (0.01 to 0.001) indicates “strong” evidence that a difference was apparent β 1 to 0.1 % (0.01 to 0.001) indicates “strong” evidence that a difference was NOT apparent δ δ < 0.5 represent small values; 0.5 < δ < 1 represent medium sized values; δ > 1 represent large values 7 May 2019

Meaningful sensory difference for company Risk for Operations Meaningful sensory difference for company The company’s action standard for a meaningful sensory difference has been set at δ = 1.25. The analyst is equally concerned about failing to take advantage of the cost savings and unintentionally introducing a perceptible change in the product. Therefore, the analyst sets both the α-risk and the β-risk at 0.10. Risk for QC 7 May 2019

n = 36 respondents for the test in order to present each of the six possible serving orders of the samples equally often. 72 X A samples, 72 X B samples 36 scoresheets. 7 May 2019

Results A total of 15 of the 36 respondents correctly grouped the samples into two groups of two. 7 May 2019

Analysis and interpretation of results From Table, the number of correct responses for significance at the 10 % risk level with 36 respondents is 17. 7 May 2019

Conclusion Because 15 correct responses is less than the critical number, 17, Conclude with 90 % confidence that any difference that exists between A and B is less than δ = 1.25, so the new process can be implemented. 7 May 2019

Take home message Sensitivity required = n number of assessors Increasing the number of assessors increases the likelihood of detecting small values of δ. larger numbers of assessors when trying to demonstrate that products are similar compared to when testing for a difference = 40 to 50 Practical considerations Time available Number of assessor available Quantity of product available Resources incl. budget ASTM www.astm.com 7 May 2019