How does air exposure affect the freshness of coffee?

Air exposure significantly impacts the freshness of coffee through the process of oxidation. When coffee beans come into contact with oxygen, a chemical reaction occurs that gradually breaks down the compounds responsible for the coffee's unique flavors and aroma. This oxidation process leads to the development of stale flavors, diminishing the overall quality of the coffee over time. Therefore, to preserve the freshness and flavor of coffee, it is crucial to minimize its exposure to air.

The other options do not accurately reflect the effects of air exposure on coffee freshness. For instance, while some may think that air exposure could improve aroma or retain flavor, the reality is that the opposite occurs due to oxidation. Additionally, air does not enhance the acidity of coffee; instead, oxidation tends to mute the vibrant qualities associated with fresh coffee.