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Journalism of Courage
Brown, over-ripe bananas often end up in dustbins, even when they are perfectly edible. This has led to scientists developing a new genetically-engineered banana which has a longer shelf-life, and does not brown as much.
Tropic, the UK-based biotech company which has developed these bananas, claims that their fruit remains fresh and yellow for 12 hours after being peeled, and is also less likely to turn brown when bumped during harvesting and transportation.
Bananas boast a colourful life cycle — they start at a deep green, change to a delicious yellow, and end (if not consumed beforehand) at an unappetising brown. These changes are a product of their ripening process, which is caused by a hormone called ethylene.
Although many fruits produce ethylene, bananas produce a lot of it. And unlike melons and citrus fruits, they keep producing ethylene even after being harvested. Contact with ethylene triggers the activity of a number of genes, including one which linked to the production of the enzyme polyphenol oxidase (PPO).
It is this enzyme that makes bananas turn brown. PPO coming in contact with oxygen breaks down the yellow pigment in bananas to a brown hue. Bruising of the fruit — as is common during its handling — leads to the production of higher quantities of ethylene, and thus speeds up the ripening and browning process.
How was a non-browning banana produced?
The company made precise changes to existing banana genes such that the production of PPO is disabled. This does not stop a banana from ripening, but helps keep up appearances so that the fruit continues to look appetising for longer.
The same gene was silenced in Arctic apples developed by Okanagan Specialty Fruits Inc. These became the first genetically engineered fruits to be approved for commercial sale in the US, and have been sold in the country (and elsewhere) since 2017. The browning of apples is also caused by PPO.
“Blocking the production of polyphenol oxidase has also been shown to work in tomatoes, melon, kiwifruits and mushrooms,” an article in The Guardian said.
Why does this matter?
Bananas are extremely perishable, with some estimates saying that as much as 50% of the crop goes to waste each year. A UK government survey from 2017 suggests that British people bin roughly 1.4 million edible bananas every day, The Guardian reported.
This is financially wasteful and harmful for the environment. Food waste is a major contributor of greenhouse gas (GHG) emissions, which are causing global warming. Preventing bananas from browning may reduce food waste by encouraging people to eat older but edible fruit.
According to the company’s press-release, “Tropic’s non-browning bananas… can support a reduction in CO2 emissions equivalent to removing 2 million passenger vehicles from the road each year”.
