See also: Article on Pineapples
You can't put fresh pineapple in Jell-O because the bromelain* content prevents gelatin from setting. Canned pineapple, on the other hand, can be added to Jell-O because the canning process destroys the bromelain.
*(Bromelain is an enzyme used as a meat tenderizer and is similar to papain in papayas).
Pineapples, like melons, do not have any starch reserves, so they do not get sweeter after they are picked. They must be harvested after they begin to ripen. The sweetest part of the pineapple is at the base.
Pineapples should be ripened at room temperature. Ripe pineapples can be stored at 40 degrees F. for several weeks.
Drink a glass of pineapple juice in the morning before work or school, eat a slice of pineapple topped with cottage cheese or add to your favorite low fat pizza for a fun treat.
Select pineapples with a nice fragrant smell. If possible choose pineapples that have been jet shipped from Hawaii or Central America because they will be the freshest. Avoid those pineapples with sour or fermented odors. It is really ripe if you can easily pull one of the leaves out of the top.
Store at room temperature for 1 or 2 days before serving to allow the pineapple to become softer and sweeter. Store in the refrigerator for 3 to 5 days or cut pineapple into chunks and store for up to 7 days. Cut up pineapple also freezes well.
CDC.gov - 5 a Day