The physiology of the pineapple is such that it cannot sweeten or ripen after harvest.  The pineapple has no starch reserve, so there is no material to convert to sugar after cutting from the plant.  It is such a starch reserve that allows fruit like bananas and pears to attain excellent texture and palatability when ripened after harvest.  while the pineapple will never be any sweeter after harvest, it may have less acid which can be lost through respiration.  s time goes on after harvest, the shell color changes and the fruit becomes soft.  This is a reflection of deterioration, not ripening.  Therefore pineapples need to be harvested as nearly ripe as possible, rushed to market, and eaten as soon as possible.

In choosing a pineapple, select one that is plump and fresh looking and as large as possible.  The larger the fruit, the greater the proportion of edible flesh.  Thus a 2 to 3 lb. pineapple has less than 30 percent edible flesh, while half of a 5 lb. pineapple has more flesh than a 3 to 3 1/2 lb. fruit

Fresh deep green crown leaves are a good sign, while old, dry or brown looking leaves should be avoided.   Fragrance is a good sign, but usually the fruit is kept too cold to be fragrant.  Ease of which leaves can be pulled out is not a sign of good quality.  The thump test is of no value.  Shell color is not an indication of maturity.  The grower can rely on a test of the sugar, using an instrument called a refractometer.  Probably the best criteria for selection is the brand of shipper.

Pineapple ripened on the plant have increased sugar, an increase in acid, an increase in color, as well as a qualitative change in the volatile flavor constituents.  Of the four quality factors, the only one usually observed by the consumer is the change in color, but in the harvested fruit, the change in color of the shell does not mean that the other three factors have also improved.