Why You Should Use Freshly Squeezed Juice For Key Lime Bars
If you think you are going to save a few steps and get away with anything other than freshly squeezed juice in your Key lime bars, or any other key lime dessert, we are here to disappoint you. Key lime pie and its variations are simple and classic American desserts that work for one big reason: it takes the citrusy tartness of limes and mellows it into a smooth and creamy cooling treat that is a perfect balance between tangy and sweet. In other words, it is a lime delivery device, first and foremost.
Working with quality ingredients is going to elevate any baked good, but for a dish based around one ingredient as Key lime bars are, they take on even greater importance. You can't hide subpar citrus with Key lime custard either; it's just sugar, some thickeners, and limes, and in bar form, you won't even have a dollop of meringue helping you out. If you use bland ingredients, you are going to be disappointed with your dessert.
You probably already suspect freshly juiced limes are the best option for this dessert, but why is bottled lime juice so different from fresh?
Fresh lime juice has much brighter lime flavor than bottled
The sad reality is that no matter how nice the bottle of lime juice you buy is, it's never going to be anywhere as good as fresh limes. Citrus juices degrade very quickly, losing a lot of their flavor within a day. Citrus juices also get much more bitter as they age, so they lose that bright tartness you want in a Key lime bar. To combat this, bottled lime juices use plenty of additives and preservatives, which alter the flavor. That would be bad enough, but even with those preservatives what is left of the lime flavor in bottled juice is pretty bland and bitter. Just one side-by-side test will show you citrus juices have one of the biggest drop-offs in quality when comparing fresh to pre-squeezed.
On top of all this, even the fresh limes you use aren't as good as they used to be. The original rise of Key lime desserts came about because the soil in the Florida Keys produces limes with a well-rounded, mellow acidity and exceptional flavor. Today, the limes (even "Key" limes) you get in the grocery store are usually not the same as the ones used in the past. They're likely from Mexico and thus grown in different soil. If you want the true Key lime experience that turned the pie into a classic, nothing but the best will do so toss your bottled lime juice, and hunt for the highest quality Key limes you can find.