system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's the thing in berry juices (specifically cranberry) that make your tongue feel dry as an aftertaste sorta effect?
gpt
Proanthocyanidin is a bitter chemical found in cranberry juice. It’s also thought to be the reason in which we use CJ as a solution for urinary tract infections. 

Because of its bitter and acidic taste, it was believed that it provided an acidic environment in the urine, which didn’t allow for bacterial growth. It wasn’t until recently that we know it actually causes the bacteria to lose grip on the side wall of the tract, causing them to be expelled in the urine more easily.  

In the end, it’s bitter because it’s filled with proanthocyanidins.