What are key limes?

Are key limes the same thing as regular limes? I had never taken the time to really find out the answer because I usually use limes when making mojitos or guacamole (in which case the type of lime really doesn’t matter). I normally just pick up whatever limes are at the grocery store. However, a  coworker of mine was craving key lime pie and asked me if I had ever made it so I thought it would be a good opportunity.

I live in downtown Toronto and was quite surprised to discover that key limes can be pretty difficult to find. Not all grocery stores sell them. Luckily for me, I live close to the flagship Loblaws store at Maple Leaf Gardens which carries almost everything (including key limes). When I saw them in the produce section, I was shocked at just how different they looked! I have definitely never worked with key limes before.

Key limes are a lot smaller and rounder than regular limes. They’re about the size of a golf ball and remind me of the tiny oranges that you might see on orange trees around Chinese New Year.


Left: Key limes; Right: Persian lime

Key limes belong to a different species of lime that produces a smaller, more sour/tart and juicier fruit compared than their Persian counterparts. They have a thinner skin and turn yellow as they ripen. They get their name from the region from which they are grown (the Florida Keys) but this isn’t the only place they grow. Until recently, they were difficult to find outside of the United States.

If you can’t find key limes at your local grocery store, you can substitute key lime juice with regular limes to mimick the flavour. You can either do a straight 1:1 substitution if you don’t want the end result to be as tart, or use more Persian lime juice to try to mimic the tart/sour flavour of key limes.

I used both types of limes to make mojitos in order to compare the two. The differences were subtle. Here is a simple mojito recipe if you ever want to do a simple taste test on your own:

Classic mojitos – Makes 1 cocktail
From Allrecipes.com

10 fresh mint leaves
1/2 lime, cut into 4 wedges
2 tablespoons white sugar, or to taste
1 cup ice cubes
1 1/2 fluid ounces white rum*
1/2 cup club soda

Place mint leaves and 1 lime wedge into a sturdy glass. Use a muddler to crush the mint and lime to release the mint oils and lime juice.
Add 2 more lime wedges and the sugar, and muddle again to release the lime juice. Do not strain the mixture.
Fill the glass almost to the top with ice. Pour the rum over the ice, and fill the glass with carbonated water.
Stir, taste, and add more sugar if desired. Garnish with the remaining lime wedge.

*If you prefer a non-alcoholic version, just omit the rum.

I also took a wedge of each lime to taste the difference on their own. The key lime is definitely more tart and sour but has a ‘cleaner’ taste. The Persian lime isn’t as sour but has more of a lime taste (but this could be because I usually work with these limes and am used to their flavour).

Of course, knowing me, I will be doing a formal taste test using key limes (versus non-key limes) to make key lime pie. Like the mojitos, you probably wouldn’t be able to taste the difference unless you did a side by side comparison. But I like making two different versions and seeing what people will choose. Plus I’ll get to share the results with all of you. Stay tuned!

Do you ever use key limes as opposed to regular limes? How would you describe the difference between the two?