The Anatomy of Flavor

Pineapples get their taste partly from hydroxyvaleric acid. But they are also a mixture of other acids, esters, alcohols, and a protein-splitting enzyme (bromelin) that will eat the skin off a man's fingers if given half a chance.

In the current Engineering and Science Monthly, a Caltech flavor chemist, Hoiland-born Dr. Arie J. Haagen-Smit, tells how he vacuum-distilled 6,000 pounds of pineapples and ended up with a few grams of powerful pineapple essence. He took the essence apart bit by bit, identifying microscopic amounts of flavor-giving compounds. Then he mixed a cocktail of the chemicals he had spotted. The result was a "satisfactory reproduction" of fresh pineapple smell.

Dr. Haagen-Smit did his laborious job for the Hawaiian pineapple growers, who believe that they can grow and market better pineapples if they know the chemical origin of the fruit's admired flavor. But Dr. Haagen-Smit's main interest is to find out what flavor really is.

Scientists know that the nonvolatile compounds in food are tasted; the volatile ones are both tasted and smelled. But why they taste or smell the way they do is still unknown. The chemical characteristics of a compound may have little to do with its taste. Cane sugar (sucrose) contains only carbon, oxygen and hydrogen, but it tastes much like saccharin, whose quite different molecule has nitrogen and sulphur atoms too.

Dr. Haagen-Smit believes that the shape of a compound's molecule is important in determining what it smells like. The nose, he thinks, contains "receptors" which are designed to respond to molecules of certain shapes. When one of these comes along, the receptor recognizes it by its shape, and sends a nerve message which the brain interprets as an odor.

Dr. Haagen-Smit hopes that his work may develop into a new technique of flavor preservation. When vegetables are dehydrated, for instance, many of their volatile flavoring compounds are lost. After chemists have learned what these compounds are, they may be able to devise tricks for capturing and restoring the natural flavor to dehydrated food.

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