What Causes Fruit To Ripen?

 
Crate of Fresh Fruit

Posted: 15/11/2017

Updated: 15/11/2017

Have you ever wonder why all of a sudden, all your fruits are rotting faster than expected?

 

One bad apple can actually spoil the (whole) bushel. You might be storing all the wrong fruits and vegetables together.

 

Most fruits and vegetables produce a natural plant hormone called ethylene naturally throughout their life cycle and also in response to a variety of stresses such as being damaged mechanically or by disease, drought, flooding and so on (1).

 

Ethylene released in the form of gas influences the growth, development, and ageing (senescence) of all plants. It acts as a natural ripening agent to help make fruits to softer and sweeter and ready for consumption (2).

How to Control Ethylene to Prevent Quick Spoilage

 

However, high ethylene exposure can cause fruits and vegetables to turn yellow or brown and the riper it is, the more ethylene gas it produces.

 

  • Thereby, if a fruit is going off, you should remove it from other fruits and vegetables so that it does not accelerate the ageing (rotting) process for others.

 

Not all fruits and vegetables produce the same amount of ethylene gas. In general, fruits tend to produce more than vegetables do. In addition, some fruits are more sensitive to these gases meaning it would take a shorter time to ripe than others. A list will be provided below.

 

  • Keep ethylene-producing fruits and vegetables separated from ethylene sensitive fruits and vegetables

 

Additional response to ethylene gas (3)

  • Browning and russet spotting of fresh produce

  • Yellowing of cucumbers, broccoli and Brussel sprouts

  • Loss of crunchiness in apples

  • Citrus fruits rind breakdown

How to Use Ethylene to Speed up Ripening

 

On the other hand, if your bananas are green and avocados are hard but you wish to eat them soon, ethylene can come to the rescue.

  • By placing an unripe fruit in a container or paper bag, it concentrates ethylene which speeds up the ripening process

  • Add another high ethylene producing fruit such as a ripe banana in the bag can also speed this up

 

Safety

Ethylene is considered safe unless at high concentrations (>1000 ppm) which can cause dizziness and can be highly explosive.

 

In contrast, calcium carbide that is used in some countries is NOT. When it comes into contact with moisture in the air, it produces acetylene gas which is an artificial ripening agent. Industrial-grade calcium carbide may contain traces of arsenic and phosphorus which is highly toxic to human health making it illegal in most countries (4, 5).

List of Fruit and Vegetables

 

Fruit & Vegetables

Ethylene sensitivity

Ethylene production

Very High

High

High

High

Very Low

Moderate

High

Very High

Moderate

Moderate

Low

Low

Low

Low

Very Low

High

Very Low

High

Very Low

High

High

Moderate

Very Low

High

Very Low

High

Low

High

Low

Moderate

Very Low

Moderate

Moderate

Low

Very Low

Very Low

Low

Low

Low

Moderate

Low

Moderate

Very Low

Moderate

Low

High

Very Low

High

Very Low

Moderate

Very Low

High

Moderate

Moderate

High

High

Very Low

High

Very Low

Low

Very Low

Moderate

High

High

High

High

High

High

Low

Low

Low

High

Moderate

Very High

Very Low

Moderate

Moderate

High

Low

High

Low

Low

Low

Moderate

Low

Low

Very Low

Low

High

Low

Very Low

Very High

List of ethylene producing and ethylene sensitive fruits and vegetables (6, 7, 8, 9).

Source: Postharvest Ripening Physiology of Crops