Why Do Eggs Turn Green?

• Scrambled eggs turn green because of a natural chemical reaction that occurs from extended exposure to heat. Hard-boiled eggs sometimes take on a gray-green hue around their yolks because of an incorrect cooking time. Other factors, such as the type of pan used and the freshness of the egg, also may cause greening.

How to Prevent Greening With Lemon Juice

• Lemon juice is effective in preventing greening, according to the American Egg Board. Beat eggs with a splash of lemon juice to avoid green hues, or whisk in a dash of citric acid crystals to achieve the same effect. Add lemon juice conservatively, but don't worry too much about offsetting the eggs' natural taste; many recipes intentionally combine lemon juice and eggs. You also may wish to use a liquid egg product rather than fresh eggs, since these products often contain citric acid.

Preventing Hard-Boiled Eggs From Greening

• Slight adjustments to cooking time and technique keep hard-boiled eggs from greening. Cooks Illustrated recommends placing eggs in a pot of cold water, bringing the water to a boil, and then immediately removing the pot from heat. The eggs should sit in the pot for 10 to 15 minutes. If they sit for longer than that, you risk a gray-green yolk.

Other Ways to Prevent Greening

• There are a variety of other ways to prevent greening. The American Egg Board advises using fresh eggs that are rated Grade A or AA; however, eggs that are too fresh may turn green and may be difficult to peel, according to “Joy of Cooking.” Since it can be difficult to accurately predict eggs' freshness, sidestep the risk of greening by cooking eggs in batches no larger than 3 quarts, avoiding prolonged exposure to heat, and using stainless-steel equipment and utensils.