This is the 10132nd most frequent Japanese word.
酸化
Oxidation.
In this sentence, '酸化' refers to the chemical process of oxidation where a substance reacts with oxygen.
鉄が酸化して錆びています。
The iron has oxidized and is rusting.
Here, '酸化' means the natural chemical reaction that causes fruits to deteriorate when exposed to oxygen.
果物を酸化から守るためにビタミンCを使います。
We use Vitamin C to protect fruits from oxidation.
In this case, '酸化' describes a chemical reaction involving oxidation that produces energy.