Detection thresholds for quinine, PTC, and PROP measured using taste strips

Area of Science:

• Sensory science
• Human physiology
• Genetics

Background:

• Bitter taste perception is mediated by various bitter taste receptors (TAS2Rs).
• Phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) are common bitter taste stimuli, but genetic non-taster status is frequent.
• Quinine is often used clinically, but tongue region-specific sensitivity to different bitter tastants is not well understood.

Purpose of the Study:

• To investigate and characterize bitter taste sensitivity differences between the anterior (front) and posterior (back) tongue.
• To compare tongue sensitivity to quinine, PTC, and PROP across different bitter taste receptors (TAS2Rs).
• To evaluate the suitability of quinine as a bitter taste screening stimulus.

Main Methods:

• Taste strips with seven concentrations of quinine, PTC, and PROP were used.
• Stimuli were applied to both the front and back of the tongue in 203 healthy participants.
• Detection thresholds for each tastant and tongue region were measured.

Main Results:

• Lower detection thresholds for bitter tastants were observed on the front of the tongue compared to the back.
• Inability to perceive quinine was less frequent than for PTC and PROP, confirming quinine's utility.
• Strong correlations were found between PTC and PROP thresholds, and also between quinine and PTC/PROP thresholds.

Conclusions:

• Determining taster status for quinine using taste strips on the front of the tongue is a suitable method for screening ageusia (loss of taste).
• This method offers a practical approach for assessing bitter taste perception in clinical settings.
• Findings highlight regional differences in tongue sensitivity to bitter compounds.