Possible Clues:

• Sensor locates son in gallery with American friend
• Umami or sweetness receptor
• It could be on the tip of your tongue
• Nerve to sample American beer?
• It might be right on the tip of your tongue
• Sensor on the tongue
• Sensory organ on the surface of the tongue
• Tongue's flavor detector
• Flavor sensor
• It may be on the tip of your tongue