From the garden
Mmmm, good. Store-bought tomatoes just never taste as good as summer tomatoes from the garden. Storebought tomatoes cannot compare to the color, the aroma, the texture, or the flavor of a vine ripened tomato.
Why the difference? Its chemistry. Specifically, ethylene (E-thih-lene), a gaseous hormone involved in biochemical pathways of many developmental processes of a plant. With only 6 atoms, the ethylene molecule is a simple hydrocarbon: four hydrogen atoms bound to a pair of carbon atoms. Although ethylene has a simple molecular formula it is essential in the physiology of fruit development.
One of ethylene’s primary functions is its regulation of fruit ripening, which brings us back to the garden tomato.
As a tomato ripens the synthesis of ethylene substantially increases, triggering a cascade of biochemical reactions that lead to changes to the developing fruit: color is enhanced, tissues are softened, flavor is modified, and aroma is intensified. These reactions signal the transition from an unripe tomato to a ripe tomato.
Once ethylene synthesis begins, there is an exponential, self-magnifying increase in ethylene, leading to the acceleration of a tomato’s ripening process. The result of the acceleration allows a tomato to continue to ripen after being harvested from the vine.
Green tomatoes are starchy. As ethylene is initiated and increases starch molecules break down and sugars, mainly fructose, are synthesized. Organic acids are synthesized with the cascade of biochemical reactions. Sweet tomato varieties accumulate more sugars than acid, while other varieties accumulate acid molecules resulting in sharp flavor.
The first indication of a ripening tomato is a blush on the green tomato’s skin. An increase in ethylene signals the degradation of chlorophyll molecules and the fruit begins to redden. New carotenoid pigments are formed as the green pigment breaks down. The carotenoid lycopene gives tomato its red pigmentation, while other carotenoids confer yellow and orange pigmentation.
It takes several weeks for a green tomato to mature into fully ripe fruit. It is during this stage of development that the tomato’s chemistry switches into full gear. As ethylene production intensifies cell walls degrade, resulting in the softening of interior tissues; aromatic volatile compounds are synthesized resulting in the distinct ‘tomato’ aroma; and sugars and acids are synthesized conferring ultimate flavor.
Always store tomatoes at room temperature as refrigeration interrupts the biochemical processes that modify flavor resulting in bland tasting tomatoes.
Ellen Peffley Harp, a retired professor of horticulture at Texas Tech University, writes about gardening for several Texas newspapers.
