Amplifying Trigeminal Flavour: Enhancing Spiciness and Coolness by Electrical and Olfactory Stimulation

Paper Title

Amplifying Trigeminal Flavour: Enhancing Spiciness and Coolness by Electrical and Olfactory Stimulation

Publication Info

• Topic area: Human-Food Interaction (HFI) and digital flavor modulation
• Keywords: Trigeminal flavors, spiciness, coolness, electrical tongue stimulation, olfactory stimulation, multisensory integration, Human-Food Interaction, flavor modulation, digital flavor systems, sensory enhancement

Background and Problem

• Problem / challenge: Prior research in digital flavor modulation has focused on basic tastes (sweet, sour, salty, bitter, umami), leaving trigeminal sensations like spiciness and coolness underexplored. Existing methods for enhancing these sensations rely on chemical additives, which can have adverse health effects.
• Significance: Spiciness and coolness are critical components of food and beverage appeal, influencing consumer preferences and gastronomic experiences. Enhancing these sensations without chemical additives addresses both sensory and health concerns.
• Motivation and related work: Previous studies demonstrated the potential of electrical tongue stimulation (ETS) for taste modulation but faced limitations in enhancing trigeminal sensations. Multisensory integration principles suggest that combining ETS with congruent olfactory stimuli could overcome these challenges, providing a healthier and more versatile approach to flavor enhancement.

Solution

• Proposed approach: An integrated multimodal framework combining electrical tongue stimulation (ETS) with congruent olfactory stimuli to enhance trigeminal flavors (spiciness and coolness).
• Novelty:
  1. Development of a multimodal method that coordinates ETS and olfactory stimuli to selectively enhance spiciness and coolness.
  2. First empirical evidence that coolness perception can be computationally enhanced using ETS combined with congruent olfactory stimulation.
  3. Expansion of the design space for digital flavor modulation beyond chemical additives, enabling healthier and personalized eating experiences.
• Procedure and key techniques:
  • Electrical tongue stimulation using a custom-built constant-current stimulator.
  • Controlled olfactory stimulation via a custom-built display delivering congruent odors (lemon for coolness, black pepper for spiciness).
  • Psychophysical experiments to evaluate perceived intensity of spiciness and coolness under various conditions.

Results

• Concrete findings:
  • Coolness: Combining anodal ETS with lemon odor significantly enhanced perceived coolness (median difference = 20.3, p_adj = .008).
  • Spiciness: Anodal ETS alone significantly enhanced perceived spiciness (median difference = 10.5, p_adj = .008), but adding black pepper odor did not provide further enhancement.
• Advantage over baselines:
  • Coolness enhancement required multimodal integration (ETS + lemon odor), outperforming unimodal methods.
  • Spiciness enhancement was robust with ETS alone, simplifying hardware requirements for this sensation.
• Experiments / evaluation:
  • Two user studies with 24 participants each, using within-subject designs to evaluate coolness and spiciness enhancement.
  • Participants rated perceived intensity using a 100-point visual analog scale (VAS) across four experimental conditions (control, odor-only, ETS-only, ETS + odor).
• Limitations and future work:
  • Fixed electrical stimulation parameters limit generalizability; future studies should explore varying waveforms and intensities.
  • Lack of incongruent odor conditions prevents full isolation of neural mechanisms.
  • Current hardware form factor (spoon electrode, nasal tubes) disrupts natural eating behaviors; future designs should focus on miniaturized and integrated interfaces.

Summary

This study introduced a multimodal approach for enhancing trigeminal flavors (spiciness and coolness) by combining electrical tongue stimulation (ETS) with congruent olfactory stimuli. Psychophysical experiments demonstrated that coolness perception required multimodal integration (ETS + lemon odor), while spiciness was robustly enhanced by ETS alone. These findings establish a foundational framework for digital flavor modulation, enabling healthier, personalized, and immersive dining experiences. Future work will focus on optimizing stimulation parameters, expanding cross-modal interactions, and designing interfaces suitable for everyday use.