Some vegetables are rich in this kind of pigment, which will turn into different colors when they meet acid and alkali, so they can be used as acid and alkali indicators. A typical example is anthocyanin, which is rich in grapes, purple potatoes, purple cabbage and other foods.

The reason why most natural foods fade after washing is the dissolution of pigment. It is easy to fade when washed with water, because the pigment in food just dissolves in water. For example, polyphenol pigment and beet pigment are water-soluble pigments, which will fade when dissolved in water.

Extended data:

Among all kinds of foods, there are four kinds of natural pigments.

1, tetrapyrrole pigment: including heme in meat and chlorophyll in green vegetables. They are good at capturing and transmitting light energy, and also like to "capture" some metal ions.

2. Carotenoids: including a series of pigments from yellow to orange to red, such as carotene in foods such as carrots, oranges, mangoes and pumpkins, and lycopene in watermelons, tomatoes and blood oranges.

3. Polyphenol pigments: including anthocyanins and other flavonoid pigments, such as flavonoids. Anthocyanins are a big family, but their styles are very similar, from purple to purple to blue-purple to purple-black.

4. Beet pigment: including beet pigment and betaflavin. In fact, lycopene is not uncommon. The rosy hue of red beet head, cowhide (leaf beet), red amaranth and red pitaya is brought by lycopene.

People's Network-Fruits and vegetables that will change color? It turned out to be pure natural "magic"