Solvent and sample/rinse temperature effects on sweet and salty sensitivity in sensory difference tests

The study was undertaken to investigate the effects of sample/rinse temperature combinations and solvent (water or apple juice) on sweet and salty sensitivities of panelists in sensory difference tests. A modified signal detection technique was employed in the experiments. In one experiment apple juice containing sucrose or NaCl was presented at varying sample and water rinse temperature (6^°, 24^°, 50^°C and/or no rinse) combinations. Discrimination abilities of the panelists were measured by R-index values. No temperature effect was found among the sample/rinse temperature combinations in sucrose difference tests. Salty difference tests exhibited a temperature effect. R-index values were higher (greater discrimination) in 24^°:C samples than in 6^° or 50^°C; sample temperature had a greater effect on discrimination than did rinse condition (temperature or no rinse). Panelist variability in both sucrose and NaCl difference tests was attributed to motivation and differential sensitivities to the stimuli. In the second experiment, panelists' sensitivities to sucrose and NaCl in water and apple juice were monitored across a 200-stimuli test to determine if sensitivity in water indicated sensitivity in a food system. Panelist variability across the 200 stimuli had the greatest effect on the results. Repeated sucrose R-index values indicated equal sensitivity in water and apple juice, although the sucrose concentration was 3 times greater in apple juice than in water. Repeated NaCl R-index values indicated greater sensitivity in water than apple juice; the NaCl concentration was 3.5 times greater in apple juice than in water. Cumulative NaCl R-index values showed 8 of the 10 panelists to have similar sensitivities in water and apple Juice, yet variability was greater in apple juice (higher standard deviations) than in water. Cumulative sucrose R-index values showed sensitivity was greater in water than apple juice. It was concluded that sensitivity to sucrose or NaCl in water was not indicative of sensitivity in a food system (apple juice).