What factor primarily affects the freshness of coffee?

The primary factor that affects the freshness of coffee is moisture and air. Coffee beans are hygroscopic, which means they absorb moisture from the environment. When coffee beans or grounds are exposed to air and humidity, they can go stale more quickly due to oxidation, which diminishes their flavor and aroma. Keeping coffee in an airtight container away from moisture prevents these negative effects, allowing the beans to retain their freshness for a longer period.

While store temperature, type of beans, and ground consistency can impact the overall quality and brewing process of coffee, moisture and air play a more direct and significant role in determining how fresh the coffee remains over time. Therefore, controlling moisture and air exposure is crucial for maintaining the desirable characteristics of coffee right up until it is brewed.