Do pineapples ripen after they are picked? I had alway thought you could leave them on the counter to ripen, however, I recently heard they don't ripen after they are picked.
Pineapple softens, but not sweeten on shelf ripening.
Fruit ripening is usually due to exposure of unsaturated hydrocarbons e.g. ethylene. This phenomenon occurs in fruit known as "climacteric fruits". Well known examples are banana, avocado, tomato, apple, pear, kiwi, to name a few.
Pineapple is not a kind of climacteric fruit. However, ethylene exposure will activate chitinase (which is a type of enzyme that breaks down chitin, a structural material inside plants), and cause softening of the pineapple. To achieve this a simple method is to place a ripe banana with the pineapple which release ethylene.
According to Dole and Cooking for Engineers (which has an excellent article on a variety of fruits) pineapples do not ripen after picking but do change color. So it will be just as sweet when it is green and fresh as when it sat and turned yellow.
I tend to disagree with many of the opinions. I consider softness to be an important aspect of ripeness in the pineapple. While they claim it wont get sweeter, softer pineapples that are fragrant from the base (usually tend to have the leaves pluck off easy and show a little more yellow), are always sweeter and juicier to me than a green one with firm leaves. I actually dont like chewy hard pineapple, so allowing some shelf ripening for softness is critical to me.
I also agree that a green pineapple with no scent to it when you smell it is not a ripe pineapple. There are three ways to tell when a pineapple is ripe. If you wait a few days and it turns to a yellower color and if you sniff it and you can actually smell the pineapple and the leaves on top can be plucked without having to pull so hard, that's when a pineapple will be at its best. It is definitely definitely sweeter And juicier than green hard pineapples. Plus this way you don't get the nasty chewy stringy hardness that an all green, hard, non-smelling pineapple in a store would give you. Unless you buy it already nice and ripe , just be patient and in 2-4 days depending on the pineapple itself, you'll know what it is to eat a delicious ripe fresh pineapple.