Bromelain separates the peptide bonds that connect collagen's proteins. Since collagen provides muscle tissue with its shape, as the collagen breaks down the muscle tissue becomes less firm. Bromelain is a mixture of two protein-digesting enzymes, or proteases, that is found in pineapples, according to How Stuff Works.
Bromelain's ability to break down collagen makes it an effective meat tenderizer, explains How Stuff Works. The enzyme should be used shortly before cooking so that it softens the meat for eating without making it overly mushy. The enzymes are neutralized around 158 F, so after reaching this temperature, the enzymes stop working.
Bromelain also breaks down gelatin, notes How Stuff Works. If a fresh piece of pineapple is placed into Jell-O as it is cooling, the Jell-O remains in liquid form and does not gel. When a person consumes bromelain, the enzyme begins to break apart the peptide bonds that allow amino acids to become proteins on a person's tongue. A person's body regenerates these cells, so no permanent damage is done. After a person has eaten pineapple, a person's body metabolizes it and it is not harmful.
Those who cut and harvest pineapples experience extensive hand damage, reports How Stuff Works. People once thought that bromelain destroyed fingerprints, but this is false. Unless a person's finger is completely destroyed, such as through a severe burn, the fingerprint always returns.
Bromelain is added to beer to keep it from becoming cloudy, states How Stuff Works. At 32 F, the proteins in beer form bonds with other elements, giving the beer a cloudy appearance. Manufacturers add bromelain to prevent these bonds from forming and keep the beer clear.