Going out to buy salted duck eggs, I heard that there may be “Sudan Redâ€; buy a box of tea, I heard that there may be “artistic greenâ€... In recent years, the media has exposed a number of industrial dyes related to food, Let people know what to do.
Although industrial dyeings have great harm to human health, we have no way to deal with dyed foods. Is there any easy way to identify dyed foods? Some people say that with blisters, if they fade, they must be dyed. Natural foods will not fade. Natural food does not fade? Are the faded foods necessarily colored?
Why dye food?
After the exposure of dyed foods, many people said that they could not understand that food pigments only changed the color, only "good-looking" role, why must do this? And this is not the case. The color of food can change people's taste experience of food and influence the choice of food.
One area in modern food technology is to study how the various properties of food influence how people feel about food. Foods with the same ingredients and processes are simply different in the colors they use. This can lead to significant differences in people’s ratings and affect people’s choice of food. In fact, the Chinese people's pursuit of good food coincides with the following: The ancients said that food should be full of "color and fragrance," and this "color" actually refers to the color of food.
The use of pigments to dye food is not a product of the modern food industry, nor is it after a food safety incident has been exposed. In China, long-term use of vegetable juice dyed tofu. However, the use of synthetic pigments is indeed the result of the development of the modern food industry.
In general, a synthetic pigment undergoes complex evaluation experiments before it is allowed to be used in food. In terms of safety, there will be a large number of toxicological tests to assess and confirm that it is harmless to the human body before allowing use. In addition to toxicological experiments, there are basic suitability experiments that examine whether the pigment can be applied to the dyeing of common foods.
What is suitable? We know that food must go through a long journey from production to the end of our mouth. For example, during storage, it undergoes tests of temperature, light, oxygen, and other harsh environments. The pigments in food naturally escape. These tests. A synthetic pigment that is suitable for use in a food must be able to survive these tests and be well preserved. This requires that they have good stability, are not easily discolored and cannot be easily decomposed, and cannot be discolored due to temperature changes, oxidation, or light, or produced. Other harmful substances.
Taking into consideration the safety, the consumption of synthetic pigments also requires a very bright color with a small amount. Therefore, synthetic pigments that can be used in foods require a strong coloring ability, do not fade easily, and have good stability. This is also the reason why most natural pigments are not widely used. Natural pigments are mostly unstable and can easily fade or fade.
Some natural foods will also fade
When the strawberries were washed, the water turned red. When the mulberry was washed, the water became dark. When the purple rice was washed, it was found that the water became dark. Are they dyed? Some people will inevitably be nervous when they see the food fade.
Or why do some foods fade? There are many kinds of pigments in nature, their structures and properties are different, so they will have different colors. Due to the different structures, some pigments can be dissolved in water, while others cannot. When washing with water or when soaking, the color drops out and the water changes color because the pigment dissolves into the water. Conversely, if a discoloration occurs, it is certain that there is a certain pigment in the food that can dissolve into the water.
Food pigments can be classified into natural pigments and synthetic pigments according to their sources. Natural pigments can be divided into plant pigments, animal pigments and microbial pigments according to their sources. Since animal pigments are generally relatively small, most of the pigments in daily life are plant pigments.
Plant pigments are a very complex class of chemicals. The variegation in the natural world is largely due to plant pigments. For example, the roses, blueberries, etc. we see are all natural pigments in plants.
Although strawberries, mulberry, and purple rice vary widely in color, shape, and plant organs, they all contain the same pigments, namely anthocyanins. Anthocyanins are a group of polyphenol pigments. They are widely distributed in various parts of the plant. The just-emerged toon buds, the bright red rose petals, the falling red maple leaf, and the red beans of acacia all have anthocyanins. .
Anthocyanins are also a major natural colorant in the food industry today, such as radish red, red rice red, black bean red, roselle red and mulberry red. Anthocyanins can be dissolved in water, and they are usually stored in the vacuoles of plant cells. When the cells break, they dissolve into water. This is the fade that we usually see.
Some foods also change color magic
In addition to fading, natural foods have a lot of interesting discoloration. In fact, they are all related to the nature of natural pigments, not necessarily artificially added pigments.
For example, when making purple sweet potato cake, the purple cake embryo will turn blue-green after adding baking powder. This is because anthocyanins become red when they are acidic, they are more stable when the pH is >4 (about 4), but they turn blue when the pH of the environment is alkaline. The purple of purple sweet potato is actually anthocyanin, and the baking powder is alkaline. Making cakes and baking flour is to make the surface better, but the anthocyanin can't stand it, so it changes color.
For another example, the cut apple has a dark brown layer on the surface of the pulp. This phenomenon also occurs when potatoes and pears are cut. How is this going? Is it also dyed? In fact, this is also a color change reaction of natural pigments. The chemical structure of natural pigments mostly contain unsaturated double bonds and other oxidizable groups. Under the action of air oxidation, an enzymatic reaction occurs and brown substances are generated. Cooking boiled green bean soup often turns red, because the natural pigment in mung bean soup is oxidized.
Also, some metal ions also affect natural pigments. Generally, a small amount of Na+ and Ca2+ have little effect, but Cu2+ and Zn2+ have a greater effect, especially Fe3+. For example, cooking peaches in an iron pan at home will turn grayish black, because polyphenolic pigments will form dark complexes that become red, dark brown or even black after encountering some metal ions such as iron ions. . Although this reaction will not lead to poisoning, the fact is that it affects appetite very much.
Although there have been many food dyeing incidents in recent years, people still cannot think of discoloured food as being dyed. After mastering some scientific common sense, it will not be frightening and afraid.
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