http://www.quisqualis.com/Climacteric.html
Non-climacteric fruit (e.g. oranges), even if treated w/ethylene, will not ripen past the point of harvest. They will only begin to decay.
Fromhttp://www.internationalrecipes.net/article/En ... e%20Season
Examples of such fruits are: apples, pears, plums, peaches, melons, avocados, bananas, mangoes, passion fruit, persimmons, guava, nectarines, plantains, apricots, and tomato. Examples of non-climacteric fruits that will not ripen further after being picked are cherries, berries (including strawberries, blueberries and cranberries), grapes, citrus (including oranges, lemons, limes and grapefruits) pineapple, watermelon and cucumber. Tomatoes and cucumbers are listed botanically as fruits although their usage is categorized for vegetables.
Many people have trouble choosing a ripe melon (a climacteric fruit) and the pineapple (a non-climacteric one). In selecting a melon, fragrance is the most important factor. Pick up a cantaloupe, honeydew or watermelon and smell the entire fruit to include both blossom and stem end. A sweet fragrance is a good indicator of a ripe, sweet fruit. Cantaloupes should not be green but have an even orange-gold color. Honeydew should be a pale creamy green or creamy yellow color. Watermelon should have uniform color and a shrunken and shriveled stem end, which indicates maturity and ripeness. Actually, when buying melons, checking the stem end is also important. The area should be a bit indented and yield a bit when press with a finger.
Choosing a good pineapple is much harder to determine. A good pineapple is a heavy fruit, with uniform golden color and a sweet fragrance. These qualities are the best indicators for ripeness. Despite popular perception, pulling off the center leaves is not an accurate way of determining ripeness.
Fruits such as peaches, pears, plums, nectarines, avocados and kiwis should have an even color. They may be feel hard when first purchased but will soften, may change color and become juicy or soft in several days at room temperature. Tomatoes ripen and develop color with warmth and not sunlight; refrigerate when ripe.
Citrus fruits should feel heavy and not hollow. Thin-skinned citrus have more juice than do thick-skinned citrus. Refrigeration will not harm these types of fruit.
The chemical responsible for the ripening process is a hormone called ethylene. Apples are a good example of a fruit that have the power of ethylene. Many have learned the trick to include a ripe apple or banana in a bowl with some unripened fruit as a means of causing the other fruits to ripen more quickly. Another simple solution to hasten ripening is to place fruit in a brown paper bag (prick a few small holes in the bag–include an apple or banana if desired) and seal. The trapped gas causes ripening and the fruit should start to ripen within approximately 8 hours. Fruits such as green bananas and hard tomatoes may be shipped to remote places and then sprayed with ethylene to hasten the ripening process before they reach the supermarket.
At normal room temperature most climacteric fruit ripens from one to four days. Once ripe, fruit should be refrigerated if not eaten within a day or so. Don't be surprised if fully ripened fruit rots quickly. If a fruit gets overripe, remove the individual piece from the remainder of the fruit. Because ethylene is very powerful, the remainder of your fresh fruit would soon spoil. Once fruit starts to ripen, the chemical process of “respiration“ occurs (rapid use of oxygen and production of carbon dioxide) and is quite efficient. Even refrigeration may not be a complete deterrent for overripe fruit. In other words, the end stage of ripening is eventual decay. So enjoy your fruit at its peak!