Oxygen in the air can cause sliced fruit to brown, a process called enzymic browning (an oxidation reaction). Phenols and the enzyme phenolase are found in the cells of the apple, and when these are exposed to oxygen in the air, for example through slicing, the oxygen causes a reaction.
Symptomatic treatment, supportive care, supportive therapy, or palliative treatment is any medical therapy of a disease that only affects its symptoms, not the underlying cause.
