What characteristic is essential when considering key lime for culinary use?

The essential characteristic of key lime for culinary use is its unique flavor. Key limes, known for their distinct tartness and fragrant aroma, are prized in various dishes, particularly in desserts like the famous key lime pie. This flavor profile sets them apart from standard Persian limes, making them a sought-after ingredient in recipes that emphasize their zesty, sweet-tart taste.

While size and juiciness are factors in evaluating limes, the key lime's recognition stems primarily from its flavor, which is central to its culinary identity. Availability and regional growth conditions can vary, but the unique flavor is what chefs and home cooks seek when using key limes in their dishes.