Utilizing the R‐Index Measure for Threshold Testing in Model Soy Isoflavone Solutions

Twenty‐eight untrained panelists used the signal detection rating method to determine thresholds for daidzein and genistein. Five concentrations of genistein and daidzein were suspended in starch solutions. The starch solution represented the noise, and isoflavone suspensions represented the signal. Blindfolded panelists received 15 replicates of noise and signal. To determine group detection thresholds, the concentration at an R‐index of 75% was calculated. The group thresholds for genistein and daidzein were 4.006 × 10 −3 M and 2.921 × 10 −3 M, respectively. These results indicate a much higher threshold value than reported in the literature and in soymilks. This strongly suggests that daidzein and genistein individually do not contribute to bitterness or astringency in soy food products.