Tongue and Nose Work Hand in Hand

There are four tastes that can be recognize by the tongue: sweet, sour, bitter and salty. Our tongue has taste receptors that can detect the tastes, but these taste receptors do not act alone. They are aided by the small receptors. Our smell receptors can recognize thousands of different scent molecules. With your nose closed, you are relying on the taste receptors on your tongue alone. Some of these receptors recognize “sweetness” when the hydroxyl groups (-OH) of the sugars in the candy bind to them. Other receptors recognize “sourness” when they come into contact with the hydrogen ions of the acidic compounds in the candy.

In a similar way, the ions in salts stimulate “salty” receptors and the nitrogen-containing alkaloids stimulate “bitter” receptors. The perceptions of sweetness and sourness provided by the tongue are not enough to allow a person to identify flavors. After you have sucked on a candy for a while, you may be able to identify the flavor because the olfactory receptors may begin to come into play. But also, the scent molecules from the candy volatilize and travel into the nasal passages through a “backdoor” – a passage at the back throat. These molecules arrive at the olfactory bulb, a part of the brain that houses the olfactory receptors. The olfactory bulb contains at least 1,000 different types of receptors that allow the average person to distinguish among about 10,000 different scents.

The flavor sensations typical of hard candies- cherry, orange and so on- are produced by specific “flavor” molecules that are recognize by receptors in the olfactory bulb, and not by the tongues taste receptors. After you open your nose, the olfactory bulb can do its job unhindered, and sensing the flavor molecules in the candy becomes relatively easy.