alll the way lime green!! but the orange!! hehehe
The Key lime (Citrus aurantiifolia, Citrus aurantifolia, or Citrus x aurantiifolia (Christm.) Swingle), also known as the Mexican lime, West Indian lime or Bartender's lime, has a globose fruit, 2.5-5 cm in diameter (1-2 in), that is yellow when ripe but usually picked green. It is smaller, seedier, has a higher acidity, a stronger aroma, and a thinner rind than that of the more common Persian lime. It is valued for its unique flavor compared to other limes, with the key lime usually having a more tart and bitter flavor. It is perhaps most distinguished as an ingredient in the Key lime pie.
A key lime is a lime that is indigenous to the Florida keys. They are about half the size of a regular lime. They also provide a bit more tart than a regular lime. They are the key ingredient in key lime pie. mmmmmmmmm!
To me, a key lime is small and looks simialr to a kumquat, about as big around as a quarter (US 25 cent piece). I have heard them described as Mexican limes, but those are larger. Even larger still is the Persian lime. Kaffir limes you would not mistake, since they are lumpy. The other limes have smoother skins, although the Persian limes are not as smooth as key limes and Mexican limes. I generally use Mexican limes for regular lime usage. Key limes I save for key lime juice, freezing any extra juice I have for later. I don't care for Persian limes and Kaffir limes I only use in Asian cooking. You can buy key lime juice in bottles, but it is better to buy them while they are at the market, freezing any juice you don't need right away. Check out this pic, it is just about right. The one on the left would be the Mexican lime, and the one on the right would be the Key Lime. Oh, and key limes are less tart than others.
In response to the other responses, the key lime is smaller, but I would say it's much more tart. Even though it's smaller, I would use no more than half as many key limes to substitute for normal limes in a recipe. The taste can be overwhelming if used in excess.
Key limes are from the keyes in Florida. They are small and round and has some yellow and sometimes more yellow then green. Where I am from they aren't available everywhere speciality gourmet markets. If making a Key lime pie just use regular limes if the key lime isn't available.
