Keratin, also known as canthaxanthin, is a carotenoid naturally existing in crustaceans, fish, algae and other organisms. It is an orange-red pigment with good stability. It is often used to color beverages, sauces, meat and other foods, which can make the color of egg yolk brighter and the color of animal meat more rosy. However, canthaxanthin is generally not used for food coloring, but mainly used for feed addition, which can be extracted naturally or synthesized artificially. Because of its small molecule, it can be synthesized exactly like nature. It is an international practice to feed animals with canthaxanthin. Because artificial synthesis is more economical than natural extraction, canthaxanthin as a feed additive is basically artificial. However, some farms that emphasize "pure nature" will use natural extraction.
The EU limits are: 80 mg/kg in feed; In the feed for laying hens: 8 mg/kg; Other poultry and salmon feed: 25mg/kg. After experiments, it was found that only a small part of canthaxanthin in food can be absorbed, and most of it will be excreted directly. The absorption ratio is related to the fat content in food. In animals, the absorption rate is only 3% to 8%. In human body, the absorption rate is between 9% and 34%. After stopping eating, the content in other tissues will disappear quickly, while the content in fat will decrease slowly. Overall, it takes 5 days to fade by half. Generally, the residue in animal meat is very low and will not have any impact on human body. The International Committee of Experts on Food Additives has set the safe limit of canthaxanthin at 30 micrograms per kilogram of body weight per day, which will not pose an obvious threat to health.
On the whole, in various safety experiments, canthaxanthin has performed well in lethal dose, genotoxicity, reproduction, carcinogenesis, organic lesions and sensitization, and its safety is still very good.
Egg yolk: feed changes color
In fact, when raising poultry, it is allowed all over the world to add colorants to feed to change the color of egg yolk or chicken. The colorants allowed to be used in the Catalogue of Feed Additives issued by the Ministry of Agriculture of China are carotenoids, including β-carotene, paprika, β-apo -8'- carotene aldehyde, β-apo -8'- carotene ethyl ester, canthaxanthin, lutein and so on.
This is easily used by some egg traders. If you want to change the color of egg yolk, you can completely rely on feed additives in the process of raising poultry. If you want the yolk to be red, you can add orange-red carotenoids, such as garlicin red, and if you want the yolk to be yellow, you can add yellow carotenoids, such as lutein.
In addition, in addition to adding feed additives, changing feed can also change the color of egg yolk, that is, feeding foods rich in carotene, such as corn residue, crushed carrots, etc. These natural foods themselves contain a lot of lutein and carotene. For farms, they can also claim that their eggs are "natural", so there are many such practices.
Egg yolk: color has little to do with nutrition.
Finally, consumers should be reminded not to judge the nutrition of eggs by the color of yolk. The yellow color of egg yolk is mainly a carotenoid-lutein. The yellower the yolk color, the higher the lutein content.
At present, nutrition research has found that lutein has good oxidation resistance, and it is also an important component of the retina of the eye, which is very helpful for preventing macular and some vision problems in the elderly. Lutein, which is beneficial to eyes and eyesight, is very advocated by the nutrition circle at present and is also of great concern to everyone. Because of this, lutein is also regarded as a healthy nutrient by many people. To some extent, it can be considered that egg yolk with more lutein will be better.
However, consumers should also understand that although lutein is good for health, the best way to get lutein is not eggs, but various vegetables and fruits. Lutein is a carotenoid, which is abundant in various orange-red vegetables and fruits, such as corn and carrots. The cholesterol content of eggs is high, and almost all of them are concentrated in the yolk. Eating more eggs and yolk is not good for health, especially for patients with hyperlipidemia and hypertension. It is suggested that if you are worried about eye health and vision problems and want to supplement lutein, you should eat more vegetables and fruits instead of egg yolk.