On Food and Cooking

freshly cut leaves in a pot of water at
115ºF/47ºC for three minutes before chilling
and bagging them. Boiling temperatures will
destroy the enzyme, so cooking will eliminate
the problem. However, high temperatures can
encourage phenolic oxidation in the absence
of enzymes: this is why the water in which
vegetables have been cooked sometimes turns
brown on standing. Various sulfur compounds
will combine with the phenolic substances and
block their reaction with the enzyme, and
these are often applied commercially to dried
fruits. Sulfured apples and apricots retain
their natural color and flavor, while
unsulfured dried fruits turn brown and
develop a more cooked flavor.