Red Cabbage Health Benefits, Anthocyanins, and Indicator Fun
Important Pigments in Red Cabbage
Cabbage of any colour is a healthy and nutritious addition to the diet. Red cabbage has an extra benefit compared to its green relatives due to the presence of red, purple, or blue pigments called anthocyanins. Scientists are discovering that anthocyanins in plants may have many health benefits, including helping to prevent cancer, improving heart and blood vessel health, improving brain function, vision, and diabetes, relieving inflammation, and boosting the immune system. Anthocyanins also have the interesting ability to change colour at different pH values, which makes them useful in science experiments.
Anthocyanins are present in other vegetables (such as purple potatoes, purple corn, and red onions), fruits (such as strawberries, blueberries, red and purple grapes, and blood oranges) and grains (such as red and purple rice). Hundreds of different anthocyanins have been discovered. Scientists still have a lot to learn about the effects of these chemicals inside our body. However, the discoveries made so far have convinced nutritionists that we should all be eating a wide variety of anthocyanin-containing foods for their potential health benefits.
Cabbages of all colours and varieties have the scientific name Brassica oleracea. Cauliflower, broccoli, and Brussels sprouts have the same scientific name. The vegetables are different varieties of the same species.
Colour and pH
Red cabbages may actually be purple or even bluish instead of red, since anthocyanins change colour as the pH changes. The pH scale ranges from 0 to 14 and indicates how acidic or basic a substance is. The scale works as follows.
- A neutral substance, which is neither acidic nor basic, has a pH of 7.
- An acidic substance has a pH of less than 7.
- The lower the pH, the more acidic the substance.
- A basic or alkaline substance has a pH of greater than 7.
- The higher the pH, the more basic the substance.
The pH of the liquid in soil controls the colour of the red cabbages that are growing in the soil. Anthocyanins inside red cabbage are red in an acidic solution, purple in a neutral solution, and blue in a basic solution. A little vinegar added to the container in which red cabbage is cooking will keep the cabbage red, since vinegar contains acetic acid.
Anthocyanins and Health
Thirty-six different anthocyanins have been found in red cabbage. Lab experiments have shown several potentially useful effects of these chemicals. In test tube reactions they are antioxidants. One experiment showed that red cabbage anthocyanins protected nerve cells from damage in lab dishes and may have a useful role to play in the treatment of Alzheimer’s disease. This is a hopeful discovery, but it needs to be confirmed by other scientists. In addition, it’s not known if anthocyanins have the same effect inside the brain as they do in lab equipment. Clinical trials in humans are required.
In a lab cell culture, red cabbage anthocyanins prevented colon cancer cells from multiplying. This may also be good news, but once again the results need to be confirmed. Scientists don’t yet know if eating the anthocyanins will cause the same effect in our bodies.
Red cabbage juice has also been found to reduce inflammation, possibly due to protein components in the juice as well as the anthocyanins. In addition, some of the anthocyanins in the cabbage may have benefits similar to those in other vegetables and in fruits. Tests on humans are needed. Red cabbage is still a nutritious food, though, even without benefits from its pigments. It's a great idea to include it in the diet.
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Nutritional Benefits of Red Cabbage
Raw red cabbage is rich in nutrients. It's an excellent source of vitamin C and of vitamin A in the form of beta-carotene, which our bodies convert into vitamin A. The cabbage is also a great source of vitamin K and a good source of vitamin B6, riboflavin, folate, and thiamin. In addition, it contains a useful amount of certain minerals, including manganese, potassium, calcium, magnesium, and iron. The vegetable contains fibre and a small quantity of natural sugars. It's almost fat free.
Since water-soluble vitamins leach into the water when cabbage is boiled, red cabbage should be eaten raw. If it's boiled, the boiling water should be drunk. Water-soluble vitamins include vitamin C and the vitamin B complex. Steaming is a gentler way to cook cabbage. A small amount of a healthy oil should be eaten with the cabbage to enhance the absorption of the fat-soluble vitamins in the small intestine. Vitamins A and K are fat-soluble vitamins.
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Cabbage is known for the unpleasant odour that it produces while it's being cooked. The chemical responsible for this smell is dimethyl sulphide.
Additional Health Benefits of the Vegetable
Cabbage belongs to the family of flowering plants known as the Brassicaceae, which is sometimes known as the family Cruciferae. The members of this family have molecules called glucosinolates in their cells, as well as an enzyme called myrosinase. When the cabbage is cut or chewed, the myrosinase reacts with the glucosinolates to produce potential cancer fighting molecules called indoles and isothiocyanates.
Both red and green cabbages produce an isothiocyanate called sulforaphane. Sulforaphane has been found to inhibit the growth of cancer cells in lab dishes and slow the growth of tumours in mice.
Surveys of large numbers of people have found that those who regularly eat vegetables from the Brassicaceae family, such as any type of cabbage, cauliflower, broccoli, kale, and Brussels sprouts, have a lower risk of developing cancer than those who don't eat many of these vegetables. Correlation isn't causation, but in this case it's certainly interesting.
Cabbage may have additional benefits. Drinking cabbage juice has traditionally been used to help treat peptic ulcers. In one experiment, cabbage was found to help lower the blood cholesterol level.
Red Cabbage in Science Experiments
Red cabbage juice is popular in school chemistry experiments due to its anthocyanins that change colour at different pH values. The juice is an indicator. In chemistry, an indicator is a chemical that has one colour when it’s added to an acidic substance and a different colour when it’s added to a basic substance. The indicator can therefore be used to “indicate” whether a substance is acidic or basic.
The starting colour of the red cabbage juice depends on the pH of the water used to extract the anthocyanins. The juice can indicate the approximate pH of a substance instead of simply whether it's acidic or basic. The juice is red or pink in an acidic solution, purplish or violet in a neutral solution, and blue, green or yellow in a basic solution, depending on the pH.
How to Make an Acid-Base Indicator From Red Cabbage
There are three methods to obtain the juice from a cabbage. The only parts of the preparation that offer any risk for children are the use of a knife to cut the cabbage, the use of a blender, and the use of boiling water in methods one and two. The third method described requires warm but not boiling water.
The best water to use for pigment extraction is distilled water. This is sold in drug stores and supermarkets. Distilled water is neutral, whereas tap water may be slightly acidic or slightly basic.
- Boil chopped red cabbage leaves in a small amount of water for five to ten minutes. Remove the cabbage leaves once they’ve released anthocyanin pigments into the water.
- Pour boiling water on chopped red cabbage leaves in a container and allow the leaves to soak for at least ten minutes. Remove the leaves once the water has a rich colour.
- Place red cabbage leaves in a blender. Add warm water, blend and then filter out the cabbage leaves with a strainer. A good ratio to use is one large cabbage leaf per two cups of water.
Testing Solutions to Identify Acids and Bases
It’s fun and easy to use a red cabbage indicator in school or home science experiments. A small amount of cabbage juice can be added to test solutions to see what colour they turn. The solids should be added to distilled water and stirred to make a test solution. An alternate procedure is to add the test solutions to containers of cabbage juice.
Some examples of acids and bases that could be tested are listed below. Children enjoy choosing their own liquids to test, too.
- Acidic: lemon juice, vinegar, cream of tartar
- Neutral: Distilled water
- Basic or Alkaline: antacid tablet, baking soda, milk of magnesia
Red cabbage juice is safe and so are the test solutions above, although lemon juice and vinegar will irritate the eyes if they enter them. A child shouldn't perform this experiment unsupervised, however, in case they choose dangerous liquids to test. Muriatic (hydrochloric) acid is acidic and bleach and household ammonia are basic, for example, but they are all potentially dangerous. Use them in a heavily diluted form if you decide to use them at all and consider wearing safety goggles.
Using Red Cabbage to Indicate pH
Making Indicator Paper
Red cabbage juice can be used to make indicator paper strips resembling those used in school science labs. All that's needed is concentrated red cabbage juice and filter paper strips. A coffee filter works well for creating the strips.
The strips need to placed in the cabbage juice until they have absorbed the pigment and then hung up by a clothes pin to dry. (Red cabbage juice can stain clothing as well as paper, so it might be a good idea for a child to wear a protective apron when experimenting with the juice.) The indicator paper should be dried indoors so that it isn't bleached by sunlight.
Once the indicator strips are ready, drops of test solution can be placed on the strips and the colour change observed. The video below describes another way to create and use indicator paper made from red cabbage.
Making Red Cabbage Indicator Paper at Home
A Versatile Vegetable
Red cabbage is an interesting and versatile vegetable. It's both nutritious and healthy. Researchers and nutritionists agree that we should eat cabbage and its relatives frequently, in both raw and lightly cooked forms. In general, the darker the cabbage the more nutrients it contains.
The red version of cabbage is also useful because of its ability to change colour. This colour change is interesting to see during food preparation in a kitchen. It's also a fun and educational feature for children. As I know from experience, both younger and older students enjoying experimenting with red cabbage juice and observing its effects.
- US Department of Agriculture. (2008, March 11). When It Comes To Red Cabbage, More Is Better. ScienceDaily. Retrieved July 29, 2017 from www.sciencedaily.com/releases/2008/03/080307081409.htm
- Bioavailability of anthocyanins from the NIH (National Institutes of Health)
- Isothiocyanates and cancer risk from Oregon State University
- Cabbage and cholesterol level from the NIH
© 2011 Linda Crampton