Doctor of Philosophy (PhD)


School of Nutrition and Food Sciences

Document Type



The objective of this research was to evaluate saltiness and bitterness perception in oil-in-water emulsion systems. For that purpose, three experiments were performed: A sensory threshold study, a descriptive sensory and physical property evaluation, and a psychophysical assessment of taste perception in emulsion systems. Experiment-I: Sensory detection and recognition thresholds of NaCl, caffeine, and KCl in aqueous-solutions vs. oil-in-water emulsions were evaluated. For saltiness recognition thresholds, KCl thresholds were higher compared to those of NaCl. For NaCl and KCl, emulsions did not significantly affect the saltiness recognition threshold compared to that of solutions. The bitterness recognition thresholds of caffeine and KCl in solutions were significantly lower than in emulsions. This study showed that, compared with solutions, emulsions did not significantly affect the saltiness recognition threshold of NaCl and KCl, but exhibited bitterness-suppressing effects on KCl and/or caffeine. Experiment-II: Saltiness and bitterness intensities of NaCl (0.50/0.75/1.00%), KCl (0.50/1.00/1.50%), and caffeine (0.05/0.10/0.15%) in emulsions were evaluated using the Spectrum™ descriptive method (N=16). The type of tastant (NaCl/KCl/caffeine) and its concentration had significant effects on saltiness and/or bitterness. NaCl had higher saltiness intensity compared to KCl. For both NaCl and KCl, increasing oil concentrations increased saltiness in emulsions. Oil did not significantly affect bitterness of caffeine in emulsions. Viscosity largely contributed to overall differences among emulsions. Overall, increasing oil concentrations exhibited saltiness enhancing effects on NaCl and KCl, but oil had a marginal effect on bitterness of caffeine in emulsions. Experiment-III: Saltiness and bitterness intensities of NaCl (0.5-1.0%), KCl (0.5-1.5%), and caffeine (0.05-0.15%) in emulsions were measured using a trained descriptive panel (N=16) and the Electronic-tongue (E-tongue). Linear regression and the Stevens’ power law were used to model the taste intensities against the tastant concentrations. For the trained panel, saltiness intensities in emulsions were higher than in solutions, demonstrating a saltiness-enhancing effect imparted by oil. Bitterness intensities in emulsions were lower compared to those of solutions for caffeine, but they were similar for KCl; this demonstrated that oil suppressed bitterness for caffeine. E-tongue saltiness measurements were corresponding to those of the descriptive data; however, E-tongue bitterness intensities of KCl showed an opposite pattern.



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Committee Chair

Prinyawiwatkul, Witoon



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