A method of adjustment for preferred levels of capsaicin in liquid and solid food systems among panelists of two ethnic groups and comparison to hedonic scaling

Preferred levels of capsaicin were determined by a method of adjustment and acceptability scaling in two groups, American descendants and Mexicans living in the United States in two food systems. Four chicken stock and four rice samples with different concentrations of capsaicin (0, 4, 8, and 16 ppm) rated for degree of liking. Groups of subjects with monotonically increasing, monotonically decreasing and peaked functions of liking across the concentrations were observed in both ethnic groups. Chicken stock and rice samples were also adjusted by each panelist to their preferred level of hotness. In the first study this was accomplished by mixing with a concentrated version of the food item. In the second study adjustment was made by adding a concentrated solution of capsaicin to the food base, much like adding a hot sauce to food. Adjustment and scaling methods agreed in that a higher concentration was preferred in the rice sample as opposed to the concentration in soup. Estimated optima from adjustment and scaling were positively correlated in both studies. However, adjustment yielded lower estimated optima than scaling. Reliability estimates, based on correlation across replicates, were similar for the two methods. In the first experiment (mixing with a concentrated food), reliability for soup and rice adjustment gave r-values of +0.77 and +0.52, respectively. In the second study (adjustment by a concentrated `sauceʹ), r-values were +0.82 for soup and +0.89 for rice. The adjustment method provides a reliable and flexible technique for determining preferred heat levels in food systems.