Tesi Johnson, Gleaner Writer
A SIZEABLE East Indian mango hangs from the tree, and over a number of days, possibly weeks, it transforms from its bland green colour to a collage of reds, oranges and yellows - an indication that it is ripe and ready for the picking. Then it will be soft, sweet and succulent, much unlike its previous hard, stainy state. This transformation is induced by a naturally occurring plant hormone, called ethylene.
Ethylene, also called ethene, is a gaseous hormone in plants which stimulates the ripening of fruits, the opening of flowers, shedding of leaves, and other results. Our primary concern is its role in the ripening process in fruits.
HOW DOES IT WORK?
Ethylene is highly concentrated in the tissues of ripening and ripened fruit, as fruits often experience a burst in ethylene production just before ripening. The presence of ethylene then triggers the creation of enzymes that cause starches and acids in the fruit to break down into sugar. These enzymes are also responsible for the degradation of chlorophyll and appearance of other new pigments like carotenoids, which change the skin colour. They also cause breakdown in cell walls, thus softening the fruit. Ethylene also causes abscission (or shedding) of fruit by inducing thickening of the stem.
HOUSEHOLD AND COMMERCIAL USES OF ETHYLENE
Returning to the young East Indian mango you've been eyeing for days. Let's suppose that you are competing with bats for the ripe mango. You might pick the fruit before it is fully ripe to avoid losing it to the flying pests. The common practice is to place the mango in a brown paper bag or wrap in newspaper to encourage ripening. Then, you are actually making use of ethylene to ripen the fruit.
The bag or newspaper traps the ethylene close to the fruit, causing it to ripen faster while still allowing for ventilation. If you wish to further augment ripening, enclose a ripe banana, or an American apple in the bag, and these fruits will introduce more ethylene to the environment and thus speed up ripening.
In the commercial fruit production, ripening is induced by introducing the fruit to gaseous ethylene in a controlled environment. Fruits for export or sale are usually harvested when underripe. Then they have low ethylene concentrations, but can be induced to ripen, often at a faster rate than if on the tree, by exposing them to ethylene in a controlled environment.
Commercial producers have long exploited this so that fruits can be ripened just as they go for sale. For example, bananas are picked green, when there is low ethylene production. In this state they keep well during shipping. When they get to the warehouse, the bananas are exposed to a commercial form of ethylene and in a few days the bananas ripen fully.
Ripening by ethylene gives the fruit all the qualities obtained by natural ripening in a shorter time and allows for uniformity in the state of ripeness and appearance. Apart from bananas, other commercially produced fruits that are often ripened by ethylene are papayas, tomatoes and mangoes.
MANGOES AND ETHYLENE
Mangoes are highly sensitive to ethylene, and like bananas, mangoes that are picked when green, can be ripened using ethylene.
In the commercial process, they are triggered to ripen by injecting gaseous ethylene injected into the atmosphere surrounding the fruit. Temperature then controls the pace of ripening. The common household method is to wrap in newspaper, or store in a brown paper bag to induce ripening. As aforementioned, this process may be augmented by enclosing a ripe banana or American apple with the fruit.
Within three to five days after introducing ethylene, the fruit will ripen.
