Ways to tell ‘chemical ripe fruit’ and how to safely ripen fruits

Assortment of fruits (Photo: Courtesy)

When I was growing up in the village, I used to see my grandmother store bananas by covering them with dry banana leaves. Sometimes, she would keep the bananas in a room near the cooking place where fire was lit regularly. She did this to hasten ripening.

There is an old man in the village who used to dig a hole, place dry bananas leaves inside the hole and burn them. This was then followed by placing fresh leaves on top of burnt leaves and then bananas on top which are then covered with more leaves. The bananas would ripen in record time. That time, I never understood the science behind these fruit ripening practices. Later when I joined campus, I came to learn in one of the post-harvest lectures that what these practices were doing was to increase production and accumulation of high levels of ethylene to hasten ripening of bananas. Hastening ripening is such a simple process. I will explain.

During the growth and development period of fruits (bananas), there are many chemical and physical changes that occur. These have an impact on the fruit quality after harvesting.

Normally, ripening is the final stage in fruit maturation. During ripening, the fruit changes colour, flavour, texture and aroma to optimal eating sensorial and textural properties. The agent that triggers these changes during maturation of bananas is a chemical called ethylene. Ethylene is a gas naturally produced by plants.

How to tell ‘chemical ripe fruit’

Despite these traditionally proven methods, unscrupulous businessmen driven by greed are putting consumers of fruits health at a risk using chemicals to ripen fruits. Calcium carbide which is a strong reactive chemical and thought to contain carcinogenic properties is now being used to ripen bananas. This chemical, when it comes into contact with water it produces acetylene gas that hastens the ripening in a more similar way as the natural ripening agent ethylene.

To distinguish between artificially ripened fruits and naturally ripened, pay attention to colour. For instance, bananas which are ripened naturally are dark yellow and there are mostly small brown/black spots here and there on the bananas with the stalks being black.

Ripening gas

Bananas which are forced to ripen with carbide are lemon yellow and their stalks are green and moreover they are clear yellow without any black spots. Also, those ripened with calcium carbide are soft and have good peel/skin colour but poor in flavour. They also have a shorter shelf-life. There are proven other practices for safe ripening of bananas naturally. Placing avocados or bananas in an airtight paper bag will hasten ripening.

The ethylene produced by these fruits accumulates in the bag which accelerates ripening. As the fruits ripen, they produce more ethylene and the ethylene production process repeats itself. Sometimes, unripe bananas or avocados are placed together with a ripening passion fruit to hasten the ripening process.

Ripening bananas

Place the amount of bananas you’d like ripened in a brown paper bag and roll the bag shut. Doing so traps the ethylene gas that is naturally emitted by bananas that encourages ripening; by trapping the gas, you quicken the process. The packaging bananas are placed in creates its own atmosphere, affecting the ripeness, taste and colour. The different stages of a banana ripeness are indicated by the skin changing from green to yellow to brown, which is considered overripe. Control your banana’s ripeness by selecting the right kind of bag. However the best method to avoid the threat of harmful chemicals is to start your own fruit garden if you have space. Some fruits are easy to grow and require little or no gardening experience.

The writer is an expert on sustainable agriculture and agricultural solutions [email protected]