What it shows
Ripe fruits release a gas called ethylene that makes other fruits ripen faster. By keeping green bananas in different bags and with a ripe fruit, you see how trapping this gas speeds up ripening.
The science
Ethylene is a plant hormone, a gas that fruits make as they ripen. It tells the other cells to turn starch into sugar, make the peel yellow and make the flesh soft. A closed bag keeps the gas near the fruit and so speeds up ripening, while an open plate lets it float away.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- 6 green bananas of the same bunch
- 1 ripe banana or apple
- Paper bag, plastic bag and an open plate
- A notebook and a pencil
- Coloured pencils to match the peel colour
- A shelf in a room away from direct sun
Safety
For this project: Wash hands after handling fruit and do not eat any fruit that has gone mouldy or smells sour. Do not seal a child in or play with plastic bags near the face.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Pick six green bananas of equal size and break them apart from the bunch carefully.
Put two in a paper bag and fold the top, two in a closed plastic bag with a few small holes, and two on an open plate.
Add a ripe apple to the paper bag to see its effect, labelling it on the outside.
Place everything in the same room at the same temperature.
Every day look at the peel colour and colour in a drawing with your pencils.
Press the bananas gently and score them from 1 hard to 5 soft.
After a week compare the table to see which method ripened fastest and which slowest.
What you should see
The bananas in the paper bag with the ripe apple turn yellow first, those in the plastic bag come next and the open plate bananas are last. The daily colour chart shows the order clearly.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What gas helps ripening?
Ethylene.
2Why does a bag speed it up?
It holds the gas close to the fruit so it keeps working.
3Why was a ripe apple added?
Ripe fruit gives off more ethylene than unripe fruit.
4How do shops keep fruit from ripening too soon?
They keep it cool and ventilated to remove ethylene.
Take it further
Repeat with tomatoes or mangoes and compare which fruit responds most to the ripe apple.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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