For a fruit to ripen naturally or artificially, it needs the hormone ethylene. Ethylene gas speeds up the ripening and activates the changes in the color, texture, and flavor of the fruit. But why should you know ethylene producing fruits?
Ethylene-producing fruits are those that can ripen off the tree eg: pears, apples, and bananas just to mention a few. Ethylene gas helps the fruits to ripen faster, however, it’s advisable to store them separately once they ripen and away from ethylene-sensitive foods as the gas can cause overripening and speed up rotting.
Ethylene works by breaking down chlorophyll, which is responsible for the green color on the skin of most fruits. When chlorophyll breaks down, the fruit produces and accumulates anthocyanin which is responsible for purple and blue hues in fruit. Other fruits will produce and accumulate carotenoids, which are responsible for yellow and orange hues of some ripe fruit.
Here is all you need to know about ethylene, the fruits which produce it and the role it plays in the ripening of fruits.
Do All Fruits Give Off Ethylene?
All fruits produce some amount of ethylene. However, there are a few fruits that produce a lot more ethylene than others.
The fruits that produce less ethylene are also more sensitive to the gas, which is why one bad fruit in a basket makes all the others go bad.
Ethylene gas leads to fruit ripening and eventually spoiling in the following ways:
- The softness of a fruit depends on the condition of its cell walls, and the cell walls are made hard by the presence of polysaccharides. The most common polysaccharides are cellulose, hemicellulose, and pectin.
- Enzymes that are activated by ethylene break down these polysaccharides and the cell walls soften. This is why we feel the softness of fruit to determine its level of ripeness.
- When the ethylene is produced in excess, your fruit will soften beyond normal levels, and start going bad.
An easy way to differentiate between fruits that produce high levels of ethylene and those that are highly sensitive to the gas is the classification into climacteric and non-climacteric types.
Climacteric fruits: These are the fruits that ripen after being picked from the tree eg: Apples, Avocados, Bananas, Plums, Peaches, Pears, Tomatoes, blackberries, apricots, and Kiwifruit.
Non-climacteric fruits: These are the fruits that ripen on the tree eg: Oranges, Raspberries, Grapes, cherries, melons, lemons, pineapple, and many others.
Ethylene producing foods
Almost every other fruit produces ethylene gas. This is the gas that’s responsible for the ripening of every fruit. Some fruits produce very little amounts while others high amounts of ethylene. This is why some fruits will be slow at ripening while others ripen fast.
Here’s a list of some common fruits that produce ethylene gas:
Apples, ripe bananas, apricot, tomatoes, cantaloupe, avocados, mangoes, pears, prunes, papaya, plums
Ethylene sensitive foods
Carrots, cabbage, unripe bananas, lettuce, potatoes, peas, cucumber, broccoli, eggplant, okra, watermelon, peppers, and cauliflower.
Which Fruits Produce the Most Ethylene?
Apples, bananas, apricots, and pears are known to produce the most ethylene gas. Try to store these away from other vegetables and fruits even if you are preserving them in the fridge. Apples, for example, can make vegetables and other fruits go bad quickly if stored together because of the high amounts of ethylene they produce.
Fruits that produce their own ethylene save you the process of having to use artificial chemicals to induce ripeness.
However, the ones that produce the gas in high concentration also have another problem, the ripening process does not stop because they have been plucked from the tree.
How to control ethylene production in fruits and veges
One of the ways that you can stop high ethylene-producing fruit from going bad fast is through refrigeration. Fruits release ethylene gas in high temperatures. Therefore, when you store it in low temperatures the gas remains concentrated on the fruits hence prolonging their shelf life. However, it’s advisable to refrigerate juicy fruits like kiwi and mango when fully ripe to retain their juice.
If you grow your produce for sale, you can use climate-controlled vehicles which will keep them from ripening and going bad during transit.
The other way that you can slow down the ripening effect of ethylene gas is by keeping your fruit in an environment with less oxygen and more carbon dioxide. Oxygen is necessary for the ripening process, and its absence stops the process.
How to Test for Ethylene Gas in Fruits
There are two main scientific methods used to detect the presence of ethylene gas in fruits, gas chromatography and photo acoustic spectrometry.
However, these methods are only applicable for large horticultural and scientific application. A simpler and cheaper way to detect the presence of the gas in fruits is the use of fluorescent probes.
The probes are made using Carbene, a transition metal which is able to detect as low as ethylene levels of 0.9 parts per million in the air. The probes have fluorescent molecules whose color changes when they come into contact with ethylene gas. When you place the probe in a room with high concentration of the ethylene gas molecules, its color changes, indicating ethylene presence.
What Does Ethylene Do to Fruit?
Ethylene is an aging hormone in plants. It leads to breakdown of the polysaccharides which make the skin of a fruit hard when it is unripe. When these polysaccharide chains are broken down, the skin of the fruit softens.
The sugars stored inside the cells of the fruit also change into fructose, which is sweet. This changes the taste of the fruit from sour to sweet.
The color of the fruit changes, and it becomes smooth, and enticing. The whole process is supposed to facilitate seed dispersal because once you pluck the fruit and eat it, you disperse the seeds, and naturally, they will grow into new trees.
What is the effect of ethylene on other fruits and vegetables?
Ethylene gas is responsible for yellowing, increase in toughness, softening and rotting of vegetables such as kale, peppers, potatoes and tomatoes.
Vegetables are non-climacteric, when you pluck them from the tree, they do not continue to ripen like the way bananas do. Instead, they use up the sugars and water stored in their cells for respiration and end up flaccid. The presence of ethylene further breaks down chlorophyll, leading to browning, and rotting.
Ethylene is crucial to the fruit ripening and aging process. However, when in excess, it can lead to the same fruits and vegetables getting spoilt before consumption. Learning how to manage its production helps keep fruits and vegetables fresh for a long time.
References
- Plantphysiol: Quantitative Study Of Ethylene Production in Apple Varieties
- International Society of Horticultural Science: The Role Of Ethylene In Fruit Ripening