Color secrets in food

Have you ever felt this way, when we stood in front of the supermarket shelves and hesitated whether to take Coca-Cola or Pepsi, suddenly there was an invisible hand that prompted us to simply use color to complete the selection, completely abandoning the taste and price. influences. Or, when tangled with black tea or green tea, the eyes are constantly turning between red and green, and the invisible hand appears again, helping us to make a decision in an instant.

A similar scene will also occur in the selection of the restaurant and the choice of dishes. Styled restaurants tend to capture their hearts when consumers are not yet getting started. When ordering, they are all fish. Would you choose pickled fish or boiled fish? All are chicken, will you choose white chicken or will you choose spicy chicken? Whether you want to admit it or not, there is indeed an invisible hand that prompts us to make choices faster.

This invisible hand is actually our psychological role. To be exact, it should be the effect of color on people's psychology.

We often say that food is color, fragrance, and taste, and color is the first, because it is what we humans can feel the most quickly. Studies have shown that the color of food has an impact on people's appetite. For example, warm colors such as red, yellow, and orange tend to increase appetite, while cool colors such as blue and green reduce appetite.

There are thousands of colors in nature, and the colors of different foods are different. Today, let us explore the secrets of color in food.

How does the human body recognize color?

We know that the human eye can see objects because of the reflection of light. However, because different objects absorb light differently, the reflected light will be different, which leads to different objects having different colors.

For example, in natural light, milk is white because it does not absorb light and reflects all the light. These reflected light are superimposed and enter the human eye to form white; black rice is black because it All the light is absorbed, no reflected light enters the human eye, so it is black; the pineapple is yellow because it absorbs the yellow complementary color, purple, and reflects the yellow light, so the human eye It is yellow.

So, an interesting question arises, what is the substance that causes milk to show white, black rice to show black, and pineapple to show yellow?

Chromogenic substance in food

white

Display white potato beans: rice, yam, flour, etc.

Display white fruits and vegetables: pears, lychees, white radishes, winter bamboo shoots, cauliflower, etc.

Display white animal food: milk, chicken protein, etc.

Rice, radish, and milk can display white, on the one hand, because they contain more protein, carbohydrates, etc., which have poor light absorption ability, and can reflect all the light; on the other hand, they do not contain other Color matter. These two conditions are indispensable, otherwise it will not display white. For example, corn, although it also contains protein and starch, is yellow because it contains lutein.

I have read a post on the Internet before, saying that some people have compared the milk of a dozen different brands and found that different brands of milk have different colors, some are whiter and some are yellow (pictured above). What is it? What is the reason?

I think there are probably two possible reasons. One is the milk source problem. The feed or forage that the cow eats may contain carotenoids. The carotenoids are brought into the milk to make them yellow. The other is the reducing sugar in the milk. The Maillard reaction occurs with the free amino acid during sterilization to make the milk yellow.

Like flour, milk is also prone to yellowing. One of the main reasons for the yellowing of flour is that it contains a small amount of pigment, or it is mixed with some wheat husks during grinding. One is the action of polyphenol oxidase (PPO). The principle is the same as that of cut apples. In order to purify the flour, some flour companies not only use excessive food whitening agents, but even add some illegal additives. At present, in the sampling inspection at various levels, the banned whitening agent whitening block, benzoyl peroxide, potassium bromate, etc. have been the key inspection items.

red

Show red potato beans: peanuts, red beans, red sorghum, etc.

Display red fruits and vegetables: red heart dragon fruit, watermelon, red dates, tomato, pepper, etc.

Display red animal food: meat, cooked shrimp, crab, etc.

The natural red pigments that make foods red can be divided into the following categories according to their chemical structure:

One is carotenoids. It is a kind of rich natural pigment in nature. There are more than 600 kinds of known kinds, mainly composed of isoprene as the basic skeleton. The hydrocarbon is highly unsaturated, not only can be red, but also orange and yellow. Carotenoids also contain carotenoids, carotenoids (lutein), carotenoid lipids and carotenoids.

The second is flavonoids. At least 5,000 kinds are known at present, and can be classified into flavonoids, isoflavones, chalcone, flavans, anthocyanidins, flavonols and the like according to chemical structures. The most common ones that can be red are anthocyanidins. The basic structure is 2-phenylbenzopyran. According to the number and position of hydroxyl groups on the phenyl group, it can be divided into anthocyanins, broccoli and flowers. Cusu, on the basis of this methylation can also be derived from three pigments, namely methyl anthocyanin, 3'-methyl delusium and dimethyl delusium. Under normal circumstances, the flowering sunflower is brick red, the anthocyanins and methyl anthocyanins are purple-red, and the delphinidin, 3'-methyl delusium and dimethyl delusium are blue-violet. But unfortunately, this coloring condition is not stable. If the environment changes (pH, light, heat, etc.), their coloration will change.

The third is the scorpion. It has a basic structure of cyclohexylethylenedione, and is a red anthraquinone pigment. Its two carbonyl groups are generally in the ortho position, and most of them contain phenolic hydroxyl groups.

The fourth is porphyrins. It is a complex conjugated system in which the alpha carbon atoms of four pyrrole rings are connected by methine groups. The gaps between the four pyrrole rings combine with different metal elements to form different pigments. The intermediate metal is magnesium, which shows green (ie, chlorophyll), and the middle is iron, which shows red (ie, heme).

In addition, other natural red pigments, such as polyphenols other than flavonoids, red yeast red, etc., are not described here.

Red foods that contain red pigments are not the same, and may contain only one type of red pigment or multiple types. For example, red pigment in red beans and red sorghum is anthocyanidin, tomato and pepper are carotenoids, red dates are flavonoids, dragon fruit is beetin, meat is porphyrin, and cooked shrimp and crab are Carotene.

Orange

Display orange fruit and vegetables: carrots, oranges, cantaloupe, pumpkins, etc.

Orange is a color between red and yellow. The substance that makes food orange is mainly carotenoids.

yellow

Display yellow potato beans: soybeans, corn, etc.

Display yellow fruits and vegetables: mango, banana, alfalfa, etc.

Display red animal food: egg yolk, etc.

The boundaries between yellow and orange are not very obvious, and the substances that generally make food yellow are also carotenoids.

green

Showing green potato beans: mung beans, etc.

Display green fruits and vegetables: green, kiwi, green pepper, cucumber, oil, wheat, etc.

It is chlorophyll that makes food green. It belongs to porphyrin pigments. Chlorophyll mainly has two kinds of chlorophyll a and chlorophyll b. The difference is that chlorophyll a is a methyl group on the II ring, and chlorophyll b is an aldehyde group.

Many fruits are green when they are fruitful, but slowly turn yellow or red when they mature. This is mainly because chlorophyll breaks down during the ripening of the fruit, giving the fruit a color other than green.

blue

Display blue fruits and vegetables: blueberries, etc.

There are very few foods that can show blue in nature. The more classic ones should be blueberries. The blue color is anthocyanidins, mainly anthocyanins.

purple

Show purple potato beans: purple potato, etc.

Display purple fruits and vegetables: grapes, eggplant, onions, purple cabbage, etc.

Anthocyanins, which are mainly anthocyanins, which make foods purple.

black

Display black potato beans: black rice, black beans, etc.

Display black fruits and vegetables: black fungus, black cloth, etc.

Display black animal food: black chicken, etc.

Melanin, which can make food appear black, is a kind of mass and complex structure. It can be divided into two categories, one is the final product produced by the metabolism of compounds such as tyrosine and polyphenols, and the other is brown. Black anthocyanids. The first type of melanin can be divided into three types according to its nitrogen and sulfur content: true melanin, brown melanin and isomelan. Because the melanin structure is complex and often strongly bound with some macromolecules such as proteins and polysaccharides, it is difficult to study its chemical structure.

 Most of the plant melanin belongs to anthocyanidins, while the black pigment of black-bone chicken is a sulfur-containing heteropolymer mainly composed of anthracycline.

Why does the food color change?

Due to the influence of external factors during processing and storage, the nature of the pigment contained in the food may change, so the color of the food may also change. Let me give you a few more common examples.

1. Why do the cut apples and potatoes become darker after being left for a while, or even brown and black?

The main reason is enzymatic browning. In the case of apples, in the apple fruit, there is an enzyme called polyphenol oxidase, which can oxidize the phenolic substances in the apple fruit into strontium, which accumulates and further oxidatively polymerizes to form a brown color visible to the naked eye. Of course, this process requires oxygen to participate. If the apple is not cut, the reaction cannot occur under anaerobic conditions, and the apple does not brown. However, if the apple is cut open or an incision occurs, the oxygen in the air will come into contact with the incision, thereby allowing the enzymatic reaction to proceed.

In addition to apples, the browning and blackening of fruits and vegetables (especially incisions) that can be seen in daily life are basically the result of enzymatic reactions.

2. Why is the color of toast and roast duck deeper and deeper?

The appetite-free white-faced crickets and ducks, after entering the oven, turn into mouth-watering breads and roast ducks. The difference in feeling is inseparable from the color change. The reason for this color change is non-enzymatic browning. Non-enzymatic browning is also called non-enzymatic browning, that is, the process of darkening and browning of food has nothing to do with enzymes. It is divided into three types of reactions, one is a caramelization reaction, one is a Maillard reaction, and the last is an ascorbic acid oxidation reaction.

When baking bread and roast duck, the color changes involve the caramelization reaction and the Maillard reaction. Maillard reaction means that the reducing sugar having a carbonyl group and the amino acid having an amino group undergo condensation, polymerization and the like to finally form melanoid; the caramelization reaction means that the carbohydrate dehydrates at a high temperature in the absence of an amino acid. , degradation, further condensation to produce a dark brown product reaction.

Since both the bread and the duck contain reducing sugars and amino acids, mild caramelization and Maillard reaction are easy to occur during the baking process, resulting in an attractive golden color on the surface of the bread and roast duck.

3. Why do shrimp and crabs turn red when cooked?

Live shrimp live crabs do not show red, but once cooked, shrimps and crabs turn red, because the shrimp shells contain astaxanthin. As mentioned in the previous article, the red shrimp in the cooked shrimp and crab is called astaxanthin. In fact, astaxanthin and astaxanthin are the same thing. The difference is whether the protein in the shrimp and crab shell is combined.

The free form of astaxanthin is red (also known as astaxanthin). In living shrimp and crab, astaxanthin is blue-blue due to the combination of protein. Once cooked, the protein in shrimp and crab Degeneration occurs, astaxanthin is separated from the protein, and astaxanthin becomes free, so it shows its original color - red.

These examples are common in ordinary life. In practice, the color change of food is ever-changing. As long as the conditions of temperature, pH, oxygen, light, etc. change slightly, it may lead to a large color of food. change.

Conclusion

The color of the food is colorful, and it not only objectively reflects its appearance quality (such as freshness, maturity, processing degree, etc.), but also affects people's choice of food. For this reason, in order to make the food have bright colors, it is easier to capture the hearts of consumers, and different colorants came into being. It should be noted that whether it is a natural pigment or a synthetic pigment, as long as the amount added is within the relevant standards, we do not need to consider their safety issues.

According to the relevant regulations, the colorants currently available in foods have the following:

White pigment: titanium dioxide

Red pigment: red peony red, tomato red, lycopene, black bean red, blackcurrant red, red yeast red, peanut red, chili red, chili oleoresin, red rice red, blue sassafras red, radish red, safflower red , roselle red, grape skin red, mulberry red, acid red, jujube color, amaranth, new red, cochineal red, carmine red, bayberry red, iron oxide red, temptation red, bilberry red, lac red, comfrey Red, beet red, sorghum red

Orange: Capsicum orange, annatto, β-carotene, natural carotene, β-apo-8'-carotene aldehyde

Yellow pigment: citrus yellow, riboflavin, safflower yellow, turmeric, curcumin, medlar yellow, lemon yellow, sunset yellow, sea buckthorn yellow, quinoline yellow, lutein, corn yellow, gardenia yellow, red yeast yellow Chrysanthemum yellow extract

Green pigment: chlorophyll copper and its salts

Blue pigment: indigo, bright blue, algae blue, gardenia blue

Purple pigment: purple sweet potato pigment

Brown melanin: cocoa shell color, sorbet brown, acorn shell brown, caramel color, iron oxide black, plant carbon black