Problembeginnerdraft

Herbs turn black

Also searched as: basil turns black, herbs darken, pesto turns dark

In short: Cold, bruising or air damage the leaf cells, and enzymes turn them dark.

Picture it

Like a bruise on an apple: where the cells are hurt, it turns dark.

What happened in your kitchen?

Question 1

Were the herbs in the fridge?

Stored too cold
Basil and other herbs from warm climates suffer damage below about 10 °C.
Next time: Keep basil at room temperature in a glass of water
Cut or chopped with a blunt knife
Bruised cells release an enzyme that forms brown pigments with oxygen.
Next time: Sharp knife, cut through only once
Too long in the air
Chopped herbs and pesto darken in the air.
Next time: Chop just before serving · Cover pesto with oil

Sources · 1