I believe many people will encounter such things. The black rice, purple rice, mulberries, strawberries, etc. they bought fade after washing! This made many people panic, thinking that the things they bought were added with artificial pigments and were dyed?

I believe many people will encounter this kind of thing. The black rice , purple rice, mulberry , strawberry , etc. I bought will fade as I wash it! This made many people panic, thinking that the thing they bought was that the artificial pigment was added with and it was dyed?

But in fact, Koko wants to tell you that this may be a normal phenomenon...

1. Food fades and discolors.

may be because it has natural pigment

Food can present colorful colors because the food itself contains pigments of various colors, and the pigments in the food will fade.

. Natural pigments are divided into four categories:

①Tetrapyrrole pigment , including heme and chlorophyll , which is the largest and most widely distributed type of pigment in nature.

② carotenoid , including carotenoid and lycopene . Some yellow-orange foods, such as carrots, pumpkins, oranges, oranges, peppers, etc., usually contain a large amount of this pigment.

③Polyphenol pigment , such as Anthocyanin , widely present in dark vegetables and fruits such as strawberries, blueberries, cherries, and purple potatoes.

④Beet color , including beet red, beet color , etc.

. The solubility of natural pigments determines whether foods will "discolor"

The pigments in food can generally be divided into water-soluble and fat-soluble according to their solubility.

①Water-soluble pigment

Phenol pigments and beet pigments are both water-soluble . When they dissolve when water is dissolved, "color fading" will occur.

*anthocyanin , such as mulberries and blueberry , causes cell damage when washed, so fading is normal.

*beet red , such as red amaranth , red dragon fruit, when treated with water, the pigment will dissolve into the water.

②Fat-soluble pigment

Like carotenoids belong to fat-soluble pigment , so they will not fade when washed with water. But they are easily soluble in oil, so the oil of fried carrots and will turn yellow, and the soup of scrambled eggs with tomatoes will turn red.

Some people may wonder why there are also anthocyanins, black wolfberry fades when it is soaked, but black bean does not fade easily?

This is related to the different tightness of food epidermal cells in . Like black beans, the cell structure is relatively tight, so it will not fade in a short time. Once is soaked for a long time, the water temperature will increase, and the cells will gradually absorb water, and anthocyanins will slowly dissolve .

. Discoloration is related to the stability of pigments

In addition to color removal, there are many foods that have discoloration, which is related to the chemical stability of natural pigments, that is, will change when encountering acid, alkali, heat, etc.

like anthocyanin will turn red under acidic conditions, and will generally turn blue under alkaline. There may also be transitional colors such as purple, green, or even purple-black in the middle. When encountering some metal ions, they can also turn dark green, dark brown, gray-black, etc.; chlorophyll will turn dark yellow-green when encountering acid. If you add some copper ion , the color will be greener and will not change for a long time.

There are also some foods that contain colorless polyphenol pigment precursor , but during cooking or processing, they will be transformed into colored anthocyanins or flavonoids. For example, after apples are boiled, the flesh turns yellow, and the yam and the lotus root cause a small amount of blue-purple appear after steaming, which is normal.

3. Natural pigments have many benefits to us

Natural pigments are not only harmless to the body, but also have many benefits. Let’s take the most common anthocyanins, lycopene, and carotene as examples to specifically talk about it:

, anthocyanins

① Delay aging

① Delay aging

Anthocyanins are one of the most effective antioxidant biological active agents discovered by humans. The antioxidant ability is 50 times that of vitamin E and 20 times that of vitamin C. can help remove excess free radical in the human body, balance metabolism, and delay aging.

②Protecting cardiovascular and cerebrovascular

Anthocyanins have a high antioxidant properties that also help restore vascular elasticity, and to a certain extent, it has the effect of in preventing atherosclerosis .

③Relieve eye fatigue

It can activate and promote the synthesis of " rhodopsin " that promotes our normal vision, help improve vision sensitivity and protect eye health.

Note : Anthocyanins are not heat-resistant and stable in an acidic environment. Therefore, it is recommended that be cooked in by blanching or quick stir-frying, which can better reduce nutrient loss. At the same time, you can also add a few drops of vinegar or lemon juice to during blanching.

, lycopene

lycopene is also a strong antioxidant, can also delay aging and protect blood vessels, and has certain anti-cancer effects. Research from Harvard University in the United States found that people who eat 10 servings of tomato or tomato products a week have a risk of prostate cancer 45% less than those who eat less than 2 servings of tomato products; a large-scale study by Singapore confirmed that compared with 1/4 people who eat the most 1/4 people who eat the most have a risk of primary liver cancer 37% less .

, carotene

After carotene enters the human body, it can be converted into vitamin A and absorbed and utilized by humans.

① When vitamin A is sufficient, skin and body protective layer (such as gastrointestinal tract, respiratory tract, and reproductive tract epicortum) can maintain normal anti-infection ability and natural barrier effect against foreign invasions.

② Carotene is an ingredient in visual cells. Eating carotene moderately can improve vision, especially dark vision level .

. How to distinguish whether food is artificially dyed?

It is normal for some fruits or crops to fade, but it is inevitable that some bad merchants may dye the food manually, so you can't eat it!

So how do we tell whether food is artificially dyed?

①Look at the appearance . The color of natural foods such as purple rice and black rice is generally not very uniform. Some particles are darker, and some are shallower. The surface of the particles should be shiny and will not be dark. The dyed color is the same as the shade, and the surface does not have a natural luster.

②Draw lines . You can prepare a piece of white paper and use black sesame seeds, black rice, etc. to mark the paper. If the color is light or not, it means that it has not been dyed; if the color is very dark like a pencil print, there may be a problem.

③Add acid and alkali . Anthocyanins have a special property: they turn red when they encounter acid and turn blue when they encounter alkali. For example, if you add an appropriate amount of vinegar to the water soaked in black rice, the color will turn dark pink. If you add a certain amount of alkali or baking powder , the color will turn blue and purple again. If the color does not change, it can be judged to be dyed.

It is recommended that you try to buy at regular supermarkets, and you can also check product information when purchasing.