Judging from the shell, the shell of salted duck eggs containing Sudan red is reddish, while the shell of normal red-hearted salted duck eggs should be yellow-white or bluish-white.
Color: The color of the egg yellow under the duck will change with the season. ? In spring, the yolk is reddish. In summer, the red color of egg yolk becomes lighter. In autumn, the yolk is yellow at this time. In winter, it is all fed by feed, and the yolk is light yellow.
Moreover, even the eggs laid by the same batch of ducks will have different shades of yolk. However, after ducks ate Sudan red feed, there was no difference in the color of egg yolk in four seasons. ?
When boiling eggs: normal duck eggs (including natural red-hearted duck eggs) 10 minutes can be cooked, and the yolk is powdery. However, the red-hearted duck eggs contaminated with Sudan Red 4 are not easy to cook. Beat the eggs into the pot and bring them to a boil. Egg yolk is hard to cook 10 minute.
Because the artificially added pigment is easy to separate, it will float on the water surface or dissolve in water. If the color of the water changes when the egg is boiled, it means that it is probably artificially added pigment, and it is best not to eat it.
When cutting eggs: duck eggs with natural red yolk, the yolk is "red with yellow", and after cutting, red oil can be clearly seen flowing out, which is delicious. However, the yolk of "Sudan Red" duck eggs is bright red. Salted duck eggs made from it can smell cornmeal after being cut, and the yolk is hard and dry.
Look at the color of the yolk: salted duck eggs containing Sudan red are scarlet, indicating that the yolk of ordinary duck eggs is yellow.
Consumers should not pursue "face value" excessively when buying food. "When you encounter foods with very bright colors and unnatural red, you should be careful, such as Chili products that look very red and attractive, and duck eggs with very red yolk."
Extended data:
Because the food dyed with Sudan red is very bright, not easy to fade and can arouse people's strong appetite, some illegal food enterprises add Sudan red to food. Common foods containing Sudan red include Chili powder, Chili oil, red tofu, red-hearted eggs and so on. ?
Under normal circumstances, the yolk of poultry eggs, including the yolk of chickens, ducks and birds, will show a range from yellow to orange or even red. It is found that the color of egg yolk is mainly caused by oxygen-containing carotenoids. Egg yolk generally contains one or more carotene, so it appears "color".
Free-range ducks, because of their rich biological species, contain more carotenoids that tend to be red, and the yolk is usually red. Therefore, it is not necessary to talk about "red change" to say that "color is not the source of all evil".
Sudan red is a chemical dye, not a food additive. Its chemical composition contains a compound called naphthalene with azo structure. Due to the nature of this chemical structure, it is carcinogenic and has obvious toxic effects on liver and kidney organs of human body.
References:
Baidu Encyclopedia-Sudan Red
China Economic Net-The Better Duck Eggs Are in Huang Yue? Never pursue "face value" and beware of Sudan red.