Which of the following best describes enzymatic browning?

Enzymatic browning is best described as a reaction that causes fruits to darken upon exposure to air. This process occurs when the enzyme polyphenol oxidase (PPO) interacts with phenolic compounds in the fruit, leading to the formation of brown pigments known as melanins. This reaction is often noticed in cut or bruised fruits, like apples and bananas, that are exposed to oxygen.

The other choices do not accurately reflect the nature of enzymatic browning. For example, while some reactions are aimed at preserving food color, enzymatic browning typically results in a loss of appealing visual qualities as it turns food brown. Similarly, enzymatic browning is not a cooking method nor is it directly associated with enhancing sweetness or adding nutrients to food; rather, it can impact the overall quality and perception of freshness in fruits and vegetables.