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How to Keep Red Cabbage From Turning Blue

Kristie Leong M.D. is a family practitioner who believes in the power of nutrition and a healthy lifestyle to prevent and fight illness.

How to Stop Red Cabbage Turning Blue

Cabbage is a staple in many cuisines around the world. It's been cultivated for thousands of years and grows easily in most climates. This vegetable comes in dozens of varieties, each with its unique flavor and texture but none is so visually pleasing as red cabbage.

Have you wondered how to keep red cabbage from turning blue when you cook it? It’s frustrating when you cook this brilliant purple vegetable and it loses its brilliance. The natural color of red cabbage is a rich reddish-purple, but it often doesn't keep that color when you cook it.

When you heat red cabbage, you might notice that it turns a dull blue and loses that rich purple color that it’s famous for. If your cabbage turns colors when you cook it, don't panic! There are ways to help your red cabbage retain its rich purple color.

Add a Weak Acid

Cabbage gets its red-purple color from anthocyanins, compounds in red cabbage, and other purple fruits and vegetables. These healthful compounds have antioxidant and anti-inflammatory activity and potential health benefits for humans.

But their purpose for the cabbage plant is to protect it against stressors such as predators or drought. The reason cabbage changes color is because anthocyanins in cabbage change their chemical configuration.

One of the simplest ways to keep your beautiful red cabbage from turning a lackluster blue when you cook it is to add a mild acid, such as vinegar or lemon juice, to the pot while preparing it. If you like lime better than lemon, it's an option too since it too is acidic. Why does adding a weak acid work?

Why Acids Work

Under alkaline (or basic conditions), anthocyanins undergo a structural change (a shift in electrons) that causes them to interact differently with light. Thus, these compounds change color. Instead of a brilliant purple, the anthocyanins change to a duller shade of blue.

This can happen when you cook cabbage in water that's alkaline. But if you sprinkle lemon juice or vinegar into the cooking water, it will prevent or reduce this color change and preserve the brilliant color of your cabbage.

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The color you end up with depends upon how much acid you add. If you lower the pH of the cooking water into the acidic range, you’ll get a light purple, red, or brilliant pink color, rather than drab dark blue cabbage that doesn't look as appealing. If you don’t add acid and cook red cabbage too long, you could even end up with brown cabbage.

The Cooking Water Matters, Too

Cooking cabbage in hard water makes it more likely that your beautiful red cabbage will turn dark blue or brown since hard water is more basic and will raise the pH. By adding lemon juice or vinegar you lower the pH and make it more acidic, thereby preserving its vibrant color.

You can use any type of vinegar, from apple cider vinegar to balsamic vinegar, for this purpose. You can even use fresh lemon or bottled lemon juice. All should give a similar effect.

Sauteing Can Cause a Color Change

Do you like your cabbage sauteed with olive oil? Sauteing cabbage can also cause it to turn a dull blue or brown shade, reducing the visual appeal of the cabbage. That's because some of the acids in red cabbage evaporate during cooking and the cabbage becomes more alkaline.

To prevent this, add a little vinegar or lemon juice to the saute skillet. You can even revive some of the color brilliance lost during cooking by adding lemon juice or vinegar after cooking.

You could also change the way you cook red cabbage. Steaming is one of the best methods for preserving cabbage's color. Boiling can make the outer layer mushy and discolored so avoid this method. It also reduces the nutritional value.

Choose the Right Cookware

Here’s another tip. To keep red cabbage from turning blue, use a non-reactive pot that doesn't contain iron or aluminum. If you don't, acids can react with the metals in the pan and cause the cabbage to change color. Stainless steel pots work well because they are easy to clean and do not react with foods as aluminum does.

Keep Your Cabbage Bright and Vibrant

Now you know how to keep red cabbage from turning blue when you cook it. It all depends on how acidic the cooking environment is. Add a small quantity of lemon juice or vinegar to lower the pH and you'll end up with more vibrant cabbage the next time you cook it. Enjoy!

References

  • Petre A. What Is Anthocyanin? Foods List, Benefits, and More. Healthline. Published February 24, 2022. Accessed July 2, 2022. https://www.healthline.com/nutrition/anthocyanin
  • Mattioli R, Francioso A, Mosca L, Silva P. Anthocyanins: A Comprehensive Review of Their Chemical Properties and Health Effects on Cardiovascular and Neurodegenerative Diseases. Molecules. 2020 Aug 21;25(17):3809. doi: 10.3390/molecules25173809. PMID: 32825684; PMCID: PMC7504512.
  • "How Red Cabbage Changes Color – The Science of Blue, Pink and pH." https://foodcrumbles.com/colour-science-ph-red-cabbage/.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

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