Too Much Chili Burns Out Flavor

In a painful series of experiments that you may not want to try at home, graduate student Chris Simons put capsaicin -- the hot chemical from chili peppers -- on one side of volunteers' tongues. The volunteers then rinsed with solutions representing the five flavors of salty, sweet, sour, bitter and "umami," the flavor linked to monosodium glutamate, and rated the intensity of the flavor.

"Capsaicin always suppressed sweetness, bitterness and umami. Saltiness and sourness weren't affected at all," Simons said.

Traditional tastes -- sweet, salty, bitter, sour, umami -- reach the brain through a completely different route than flavors such as hot chili and fizzy drinks, which are actually experienced as pain by the nervous system.

As you eat a hot curry, the pain gets less as pain receptors in the tongue get less sensitive. The flavor-dampening effect is separate from this numbness, said Simons. To control for numbing, the researchers re-applied capsaicin to get a consistent burning sensation.

In many cuisines, sour and salty flavors often accompany hot spices. While sweet flavors are reduced by chili, sugar also has a moderating effect on the hot flavor of capsaicin. Adding chili could be used to reduce the bitterness of some foods, said Simons.

The UC Davis research group, lead by neurobiologist Earl Carstens and food scientist Michael O'Mahony, studies how the nervous system experiences flavors.

The research is to be published in the journal Chemical Senses.