How can you tell if a man works with pineapples? He’ll have no fingerprints.
Pineapples and pineapple plants, you see, contain a certain enzyme known as bromelain. Bromelain is really good at digesting proteins. It doesn’t just denature them like cooking, wherein clumpy bands of proteins are separated and loosened, it actually chops them up into smaller bits. This action will happen on any protein that comes into contact with bromelain, so when the workers touch the stems or process the pineapple plant juices the sap literally starts to digest their fingerprints. Neat, no?
This action also means that pineapple juice is a good meat tenderizer (a lot of powdered tenderizers are, in fact, bromelain), it is impossible to make pineapple gelatin (it’ll keep the gelatin from setting), and can occasionally make your mouth feel raw if you eat way too much of the stuff. Just to counterbalance, I should also note that bromelain also has some medicinal uses, including as a skin care product and dietary aid.