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"
What
causes the flavor of vegetables to change when cooked?
"
Dear
Anne and Sue,
What causes the flavor of vegetables to change when
cooked? For example, whether I boil, steam, or fry a
green bean, the flavor is markedly different from the
raw bean. I am assuming that there is a chemical reaction
involved. If this is true, what is the reaction? If
it is only a physical change, please explain the science
involved.
Thank you.
— Dr. Linda B. Knight, Katy, TX
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Dear Linda,
The flavor of vegetables is comprised of various combinations
of acids, sugar, polyphenolic compounds, and volatile
oils. Some of these components decompose during cooking
and evaporate with the steam that's created during boiling,
steaming, and even baking.
Flavor
changes are brought about mainly through exposure to
heat and water. In the case of beans, the longer they
cook, the more flavor they lose—some by evaporation,
and some by dissolving in the cooking water.
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Just-picked, young green beans may cook in as little as
two minutes. Their fragile sweetness is quickly lost as
sugar dissolves in water, so however you cook young produce,
make it brief and minimize exposure to water to maximize
flavor retention. Fatter, older beans with more mature
fibers, may take 6 to 8 minutes to cook.
Flavors also vary according to the intensity of the temperature
you use in cooking. If you choose to roast or grill those
beans, they'll reach much higher temperatures than they
do when cooked in water. As they brown, complex reactions
create entirely new volatile flavor components that are
not present in the raw bean. Thus, roasted vegetables
are quite different in both appearance and flavor than
the same vegetables cooked by steaming.
Our perception of flavor also includes the dimensions
of aroma, texture and color. These too, change according
to the cooking method and each change exerts a strong
influence on one's perception of flavor.
What takes place in our kitchens is indeed both complex
and intriguing.
Regards,
Anne & Sue
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