Why do my potatoes go black after cooking? | Kitchen aide

"The darkening of cooked potatoes is caused by the combination of iron ions, a phenolic substance [chlorogenic acid] and oxygen, which react to form a pigmented complex. Make the pH of the water distinctly acidic, which McGee does by adding cream of tartar or lemon juice after the potatoes are half-cooked."

"Reactive metals such as a carbon steel knife or aluminium pan may also be the cause of the issue, which is why he recommends using a non-reactive metal (think stainless steel) instead. Leaving the cooked potatoes in water is also a bad idea, as they are like little sponges."

"The potatoes will absorb the water and turn soggy and less fluffy and never refresh them under cold water or in a cold plunge, either, unless it's momentary. Much better to drain those cooked spuds, spread them out on a rack and leave to steam dry with a tea towel over them."

Blackened potatoes result from a harmless chemical reaction between iron ions, phenolic substances, and oxygen that creates a pigmented complex. This darkening worsens when potatoes cool slowly in cooking water. To prevent blackening, make the cooking water acidic by adding cream of tartar or lemon juice after potatoes are half-cooked. Reactive metals like carbon steel or aluminum cookware can also cause discoloration, so stainless steel is preferable. Leaving cooked potatoes in water causes them to absorb moisture and become soggy. Instead, drain potatoes immediately, spread on a rack, and steam-dry them under a tea towel for optimal texture and appearance.

Read at www.theguardian.com