It took me several hours of searching to find this, even though I started with the correct terms. Turns out the answer is so obvious I should have just thought a little more. The white connective pith is a pectin, and the enzyme that dissolves it is one of the pectinases (duh). it's sold as a commercial product called Peelzyme, among others.
You can use it to make flawless supremes, but you can also separate out the individual vesicles, which is what I want it for (both illustrated).
Here's an article explaining it (it repeats in English halfway down the page):
But why stop there: Here's where you can buy it, for $9:
Having tiny encapsulated citrus flavour-bombs to play with has me rather giddy. My first idea has them in a fish burrito, where just citrus juice alone would start cooking the fish.