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Many companies, including McDonald's, are removing artificial colors from their foods. Colors send important signals about food, and companies aren't going to stop using them.
Cheese
Check the packages of most cheeses, and there is likely an ingredient called annatto (胭脂红) listed. The practice dates back to when cheesemakers in England removed the butterfat from milk to make butter. The leftover milk was whiter，so cheesemakers added annatto to create a golden coloring.
Egg Yolks
Many home cooks think darker egg yolks are fresher or more nutritious. But the color may be the result of coloring products in chicken feed. Darker yolks aren't necessarily healthier. The belief that they are healthier is likely rooted in the idea that yolks are darker when hens are fed a diet of fresh plants, which contain the pigments (色素).
Salmon
Bright pink flesh may signal freshness to shoppers eyeing salmon，which is why salmon may have been fed synthetic astaxanthin (虾青素). For example, at Costco, tickets of farmed salmon are saying "Color added through feed".
"People used to get all the coloring all over their fingers. We now kind of laugh at that，" said Richard Matoian, director of a food trade association. Americans, therefore, apparently aren't entirely ready to say goodbye to the artificial colors in various kinds of food. Companies are expected to take new measures in response to customer demand.
A. Without it, cheese would be off-white.
B. But producers know the difference colors can make.
C. It's easy to change yolk colors by simply varying hens' diet.
D. But don't expect your cheeseburgers to look much different.
E. Yolk colors vary when chickens live in different climates as well.
F. Producers are asked to declare on tickets if artificial colors were used.
G. Some companies even offer various shades of pink to help judge flesh colors.