Why do purple snap beans turn green when cooked?
We often get snap beans from the CSA (Community Sponsored Agriculture) that are either entirely purple or mottled purple. When cooked (at least when steamed or blanched), however, the purple color disappears and they turn to a bright green color. As far as I can tell, this happens with any purple podded snap bean.
Why does this happen? Are there any methods of cooking purple beans that retains their original color? Are there other types of vegetables that have the same color changing reaction when cooked?
Best Answer
This is another case for anthocyanins, the same compound that causes garlic and ginger to turn blue. Anthocyanins are pH sensitive, only appearing blue or purple when in the presence of acidity. As you cook the beans, the cells begin to rupture and lose water, which causes the acid around the anthocyanins to be diluted. As this happens, they lose their color allowing the green chlorophyll (which was always present) to show through.
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Quick Answer about "Why do purple snap beans turn green when cooked?"
What is this? The heat breaks down the plant cells, diluting the acidity of the cell sap as the pigments are dispersed in a more neutral solution (water). What's left behind is green chlorophyll, which was always present in the beans but masked by the plant's anthocyanins.Why do my purple beans turn green when cooked?
Anthocyanins change color with changes in acidity, and eventually turn colorless as acid levels drop. Two things happen during cooking to make Royal Burgundy beans turn from purple to green. A direct effect of the heat is to cause decomposition of anthocyanin. Less anthocyanin means less purple.Do purple beans change color when cooked?
We often get snap beans from the CSA (Community Sponsored Agriculture) that are either entirely purple or mottled purple. When cooked (at least when steamed or blanched), however, the purple color disappears and they turn to a bright green color.Do purple beans turn green when pickled?
Sadly the purple ones turn a dull grayish green after they're boiled. It's super easy to pickle your own beans, they make a yummy snack and I love the way my jaw muscles clench up when I take a bite of their crunchy, dill and pickled goodness.How do you keep green beans color when cooking?
To retain the green, cook the vegetables in lots of boiling water. There are enzymes in green vegetables that break down chlorophyll, which are released when you cut vegetables or cook them.When cooked purple beans turn green
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Answer 2
I can't answer WHY but I can say that there is no trick to keep them purple after cooking. They always turn green when cooked.
So why Purple ? They have a different taste, they cook fast and are easier to harvest because of the color difference with the leafs.
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