Fruit Ripening: A Quick Guide
My friend Jack
Growing up, my friend Jack would always get into trouble. He would yell, draw on walls, talk over others and end up in the principles office by 10 AM. It's safe to say that Jack was one of those students that would make a primary school teacher question their life choices. One evening my teacher, Mrs. H, pulled me aside and said, “Rahul, always remember, the rotten apple spoils his companion.” I could clearly see Jack was not a fruit (pun intended), so I didn’t really understand what she meant at the time. However, growing older the mysterious case of the bad apple analogy always lingered in my mind. Besides being a metaphor for life, what was the actual science behind one rotten apple spoiling others around it?
One Bad Apple
I’m sure we all have dealt with the neglected fruits that have laid dormant at the very bottom of our fruit bowl for days on end. It’s usually an apple that you prepare to sacrifice into the depths of your stomach. Picking the apple up and turning it around you notice browning and blemishes across the skin, you immediately throw it in the bin. You proceed to pick up the orange next to it and realize it too has ripened beyond its time, in fact, the whole layer of fruits at the bottom of your fruit bowl has gone bad! You think to yourself what on earth is going on? Is it just bad luck that all your fruits ripened at the same time? Or is it that they got tired of being seen as soulless objects, only fit for human consumption. Well, let’s find out!
How fruits ripen
In nature, the ripening of fruits makes them attractive to animals. The green pigments (chlorophyll) are degraded and colorful pigments such as carotenoids are produced increasing the fruit’s visibility against leafy backgrounds. Starch, tannins, and organic acids decrease leaving sugar and aromas to increase, making the fruit palatable. A key factor in fruit ripening is triggered by ethylene. Ethylene is a colorless gas produced in climacteric fruits, with very little production in non-climacteric fruits.
Climacteric vs. non-climacteric fruits
Essentially non-climacteric fruits only ripen whilst attached to the plant. The fruits do not respond or produce ethylene once they have been picked. To put this in simple terms, if you have harvested your non-climacteric fruits too early, there is nothing you can do. You may see signs of change in the fruit that mimics maturation e.g, change in color or softening of the fruit. Don’t get too excited this is just the fruit decaying. Alternatively, climacteric fruits react readily with ethylene gas, whether produced on their own or from friendly neighboring fruits. Some hardcore climacteric producers of ethylene are bananas, apples, mangos, and peaches. So be careful when placing all these fruits together over a period of time, especially amongst ethylene-sensitive foods such as broccoli, cabbage, and cauliflower.
Avocados: an honorable mention
Avocado fruits are an exception to climacteric fruits. It basically says “stuff you” to the ripening process and only ripens when picked from the tree. You might be thinking, “So what does it do in the meantime?”. I'm glad you asked! Whilst attached, most of the avocado tree's efforts go into developing the nutritious oil within the fruit. This feature of the avocado fruit makes it advantageous for growers, packing house operators, shippers, and retailers as they do not need to worry about getting complaints from Karen on how her fruits have already rotted.
How we play god with ethylene
Interestingly, ethylene was discovered by chance. In the 1800s, illuminating gas was widely used for lighting. Near the end of the 1800s, a Russian scientist by the name of Dimitry Neljubow noticed pea plants in his labs swelling and growing sideways. He assumed it was the result of leaking illuminating gas. I’m not quite sure how, but Neljulbow, with his godly chemistry skills, later determined that ethylene from the illuminating gases was responsible for the unfortunate growth of his poor retarded pea plant. You might be thinking, why on earth is this of any importance to us? Well, I can give you 3 simple reasons
- Money
- Convenience
- A chance to play god
With the discovery of ethylene, we as humans can determine when we want our harvested fruits to ripen. Having the power to control the soul of every single fruit makes it convenient for someone halfway across the world to enjoy biting into the juicy melon that may not exist in their country and in turn we receive a tonne of cash for it. It's the circle of life people.
Examples of how ethylene gas is used/exploited in the food industry include:
- Ripening rooms — here, unripened fruits are placed into large chambers that are secured from the rest of the building. The doors are tightly locked and ethylene gets pumped into the room supercharging the ripening process for the fruits locked inside. Once the process has completed (after a couple of days) the fruits exit looking all jacked and charged up like Captain America.
- Ethylene absorbers — As we know climacteric fruits love to signal over to their neighbor and encourage them to start ripening. For this, we have also come up with a solution. Some fruits are packed with ethylene absorbers, meaning that the fruit won't ripen until its surrounding plastic has been pierced.
BBC Earth has a great video on incorporating the mechanics of ethylene in the food industry, check it out here.
Now it's your turn
Knowing all this information is great and all, however, I want you to apply this knowledge to your own fruits, go on this is your chance to show em’ who’s boss. If you bought an avocado that won’t be ready for Sally on Tuesday morning, then fear not for I have the solution. Simply place your avocado inside a brown paper bag along with a banana. Leave the bag on the counter for a couple of days and watch as the avocados magically ripen right up. Soon enough Sally’s going to be telling the whole town how she's never had a more perfect avocado on toast than yours.
Alternatively, be wary of keeping climacteric fruits around sensitive fruits and vegetables, you may just end up wasting your hard-earned money. My primary school teacher was right, the rotten apple really does spoils his companion. Those are fruits are communicating. They’re smelling each other. Keep the bananas away from the broccolis otherwise, you may be inviting a war to break out sooner than expected.
