All fruits have a relatively short shelf life but bananas ripen particularly quickly and will typically only last up to five days when stored at room temperature.
And if you cut into a banana but don’t eat it all at once, then the fruit will turn bad even faster and you’ll be left with a brown and mushy mess before you know it. But if you’re partial to a bit of banana on toast, or enjoying adding the fruit to your porridge in the morning, there is a way to keep it fresh even after you’ve cut into it. It’s generally recommended that you only cut into a banana if you’re planning to eat the whole thing, but if you do end up with some leftovers that you want to store for another day, all you need is a bit of pineapple juice to keep it fresh. Once bananas are peeled and exposed to the air they start to turn brown quickly due to a natural enzyme called polyphenol oxidase which reacts with oxygen. But if you coat the banana with a drizzle of pineapple juice you can effectively slow this process down.
This is because the citric acid in pineapple juice lowers the pH of bananas, creating an environment that inhibits the enzymes responsible for browning from functioning, thereby keeping the fruit fresh and yellow for longer.
The acid also creates a barrier on the surface of the banana which prevents oxygen from reaching the enzymes, further helping to prevent browning.
Of course coating the banana with pineapple juice will alter its taste slightly so it’s recommended that you only apply a light layer. Pineapple, like banana, is very sweet but it’s more subtle than other citrus fruits like lemon or orange which can taste quite sharp, so it’s more of an inoffensive flavour profile to go for.
Experts at Food Republic explain: “The browning process for bananas begins during preparation, as soon as the flesh is exposed to air. The more scientific term for this color change is enzymatic browning, a result of the enzymes within the fruit coming into contact with oxygen. The same reaction occurs when other fruits like apples and peaches are cut.
“To prevent this process from happening so quickly, you need to disrupt the enzyme’s reaction to the air. One of the most popular and effective methods is to coat the fruit in lemon juice, which changes the pH of the fruit. This reduces the enzyme’s ability to cause the fruit to brown.
“While the effects of the lemon juice won’t last forever, it should preserve the colour of the bananas for the length of time the dessert can be stored.”
The experts add: “While lemon juice is possibly the most commonly used ingredient to slow the browning of bananas, other acidic juices work well too. Consider using another citrus fruit juice like orange, or try pineapple juice instead.”
Once you’ve coated your sliced banana in a layer of pineapple juice, simply place the slices in an airtight container and store this in the fridge to keep it fresh.
Experts at Real Simple add: “Sliced bananas discolour quickly, so it’s best to avoid cutting into them until you’re ready to eat. However, if you sprinkle them with a little lemon or pineapple juice, it lowers the pH levels and will keep browning at bay.
“Following the juice trick, put them in the fridge, either wrapped in plastic wrap or in an airtight food storage container or bag. Stored this way, sliced bananas can stay fresh for three to four days.”
