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Key Limes vs. Persian Limes

By Cook's Illustrated Published July 2006

What’s the difference in flavor between Key limes and Persian limes?

2 Types of Limes

Key lime aficionados herald the fruit's "distinctive" flavor and fragrance compared with conventional Persian limes, but we wondered if our tasters could tell the difference in a blind taste test.

Comparing Lime Juices

Sampled plain, the Key lime juice tasted slightly less tart and bracing than its Persian counterpart, and a quick lab test confirmed that impression (the juice from the conventional limes had a lower pH than the Key lime juice, indicating higher acidity).

Comparing Key Lime Bars

When we made Key lime bars with both varieties, once again the Persian-lime version tasted a bit more tart, though tasters were split over which variety made the better bar.

Lime Size is a Practical Factor

The deciding factor may be the amount of work involved: To get the half cup of lime juice called for in our bar recipe, we had to squeeze three Persian limes. With the Key limes, it took almost 20!

What About Bottled Lime Juice?

Both Key lime juice and regular lime juice are sold presqueezed in shelf-stable bottles, and we wondered whether these would do in a pinch. The short answer? No way. The four brands we tried were at best "bracingly bitter," and, in some cases, "just plain rancid." What's more, many baking recipes (including ours) call for the addition of zest—tough proposition with a glass bottle.