Superior performance of constant-saltier-reference DTF and DTFM to same-different tests by consumers for discriminating products varying sodium contents

Reducing sodium content in foods and beverages has become very important, and great efforts are being made to achieve this while maintaining overall taste/acceptance of food. This requires more robust sensory discrimination test methods in terms of operational power because discrimination tests using food/beverages with high sodium contents might be more prone to adaptation and memory bias which might reduce the operational power of the test methods. The operational test power of six versions of the duo-trio test method (two different versions of replicated tests under three reference modes - constantly stronger-reference (S_R) vs. balanced-reference vs. constantly weaker-reference (W_R)) were investigated using a pair of tomato juices with different sodium content in comparison to the same-different tests using a balanced-design. The two duo-trio versions were the traditional duo-trio with a reference presented first (DTF) and the duo-trio with the reference presented both at the first and in the middle between the two alternative test samples (DTFM). An examination of the d' estimates indicated that discrimination significantly improved across all duo-trio tests and the same-different tests when using naïve consumer subjects and when the sample in the first position in a test was a stronger (saltier) sample. This observation granted operational superiority to the DTF and DTFM in comparison to the same-different test, using the stronger (saltier) product as a constant-reference for discriminating products with high sodium content.