Regular lime juice, from the Persian lime, is used to impart tartness to all sorts of dishes. Key lime juice is the most important ingredient in one of Florida's most famous culinary treats--the key lime pie.
Persian limes (the source of regular lime juice) are the most commonly found in markets. Although they become yellow when they are fully ripe, they are sold only when they are still bright green.
The key lime is an Asian species that was brought to the Florida Keys by the Spanish in the 1500s, says What's Cooking America. A 1926 hurricane destroyed most of Florida's key lime plantations, and today most of the commercial crop is grown elsewhere.
Differences in Appearance
Key limes are smaller and contain more seeds than the Persian lime. Also, Persian limes have a thick, vividly green skin, while the skin of the key lime is thin and yellowish.
Differences in Taste
According to Tony Tantillo on the Farm Fresh website, key lime juice is more aromatic and intense than that of the Persian lime.
Persian limes and regular lime juice are available in grocery stores year-round. It can be difficult to find fresh key limes, because they are in shorter supply and do not store well. However, bottled key lime juice is available in specialty shops and online.