If you said there’s isn’t one! then you’re one of those extreme chocolate snobs of the kind I’m married to, and right now you’re recoiling before this photo like a vampire before a sunrise. It burns! It burns! But that’s a nice question, reader Walter! Let’s get to it.
The main difference between a high quality white chocolate and a lower quality white chocolate is the percentage of cocoa butter the chocolate contains. Of course other factors play into it: the care with which it’s formulated and processed and so on. However if I had to boil it down to any one thing, cocoa butter would be it. Cocoa butter what makes the difference between a silky chocolate and waxy chocolate. Lower quality chocolates have some cocoa butter — chocolates without at least a little can’t legally be labeled “chocolate” in the US — however they can contain other types of fats, like palm oil.
Which raises the question: what’s the difference between palm oil and cocoa butter? Mainly melt point. Cocoa butter is famous for its low melt point, which is just below body temperature. It’s also famous for its “sharp” melt point, which is a related quality. A sharp melt point means an almost instantaneous change of phase from solid to liquid.
In general, solids that are more uniform in their composition are the ones with the sharpest melt points. Palm oil is composed of dozens of different types of lipids, all of which have different melt points, some low, some high. As a result it takes a fair amount of time, once the palm oil is heated, before all the various lipids melt completely. Cocoa butter likewise has several different lipids in it, however its composition dominated by just three of them, and they all melt right around 91 degrees. Put cocoa butter in your mouth and boom, it immediately starts to run.
So while lower quality white chocolate does have its uses, if you just wanted to eat some, you’re better off with a higher quality item. Not only will it probably taste better, you’ll tend to savor each morsel as the cocoa butter melts, coats your mouth and tongue, and extends the sensory experience. Thanks for the question, Walter!