Lemon preserves the color of cut fruits due to its high content of vitamin C, a natural antioxidant that helps slow down the oxidation of fruits and prevents them from browning.
When you cut an apple or a banana, they quickly turn brown: this is due to the oxygen in the air reacting with substances in the fruit. These substances are called polyphenols, and because of the oxygen, enzymes known as polyphenol oxidases come into play. They quickly cause the formation of brown compounds: this is enzymatic oxidation, responsible for this not-so-appetizing color. The more finely the fruit is cut or mashed, the larger the surface area exposed to air, and the more easily it browns. Temperature, pH (acidity), and humidity also play a role in the speed at which this reaction occurs.
The citric acid found in lemons acts by lowering the pH of cut fruits. This change in acidity disrupts the activity of certain enzymes, particularly polyphenol oxidase (PPO) responsible for browning. Basically, these enzymes can only function efficiently at a certain pH, and the acidity of the lemon messes with their routine. When the environment becomes too acidic, they slow down or completely stop their reactions, thus preventing the formation of the brown pigment called melanin. That’s why spraying lemon juice prevents your cut apples or avocados from turning ugly.
Lemon is packed with natural antioxidants, the most well-known of which is vitamin C (ascorbic acid). These antioxidants act like chemical bodyguards: they trap and neutralize reactive oxygen molecules, which are responsible for the browning of sliced fruits. Less reactive oxygen means less oxidation, so your pieces of apples or avocados stay nice, fresh, and colorful for much longer. Handy, right?
Simple scientific studies show that lemon juice clearly slows down the browning of cut fruits. For example, when pieces of apples are immersed in a lemon-based solution, their color remains stable for significantly longer. This mainly occurs at the enzyme level, such as polyphenol oxidase: the citric acid found in lemon strongly inhibits their activity by lowering the pH, which quickly prevents the formation of dark pigments on the surface of the fruits. Some research has also specifically tested the potential of lemon's antioxidants (such as vitamin C), proving that they directly help protect fruit cells from the oxygen that oxidizes them.
Before cutting your fruits, prepare a small bowl in advance with freshly squeezed lemon juice mixed with cold water. Quickly dip the fruits in it or brush them as soon as they are cut; this effectively slows down their browning. If you prefer a quicker method, squeeze a few drops of pure juice directly onto the exposed surfaces: just be careful not to overdo it to avoid an overly sour taste! You can also rub a slice of lemon directly on the surface of the cut fruits, which is handy when you're in a hurry. To store already cut fruits in the refrigerator, place them in a closed container after adding a bit of lemon juice: this will help preserve their freshness, texture, and of course, their beautiful color.
Lemon juice can temporarily replace vitamin C in certain cut fruits, thereby slowing down the nutritional loss caused by oxidation.
The enzymatic browning reaction of cut fruits can also be slowed down by storing the fruits in a cold environment, in addition to using lemon.
Apples dipped in lemon juice can retain their colors up to twice as long as those left exposed to air if they are properly refrigerated.
Other natural juices such as pineapple, orange, or kiwi can also slow down browning, but lemon juice remains the most effective due to its high citric acid content.
Yes, lemon juice is also effective in slowing down the oxidation of certain cut vegetables such as avocados, potatoes, or artichokes. However, the effect and intensity of flavor it provides can vary depending on the vegetables.
Yes, other acidic ingredients, such as orange juice, fresh pineapple, or even ascorbic acid (pure vitamin C), can also effectively slow down the browning of cut fruits.
It varies depending on the fruit and the surrounding conditions, but generally, the use of lemon can significantly slow down browning for several hours, thus prolonging the fresh appearance for up to an entire day in some cases.
The browning of cut fruits mainly affects their appearance. Although the majority of nutrients remain intact shortly after cutting, prolonged exposure to air and light can lead to a slight decrease in oxidation-sensitive vitamins, such as vitamin C.
Subtly, yes. The lemon adds a slight acidity, but when used in moderation, it pleasantly enhances the natural flavor of the fruits without masking their taste.
Yes, it is possible to use diluted vinegar (like apple cider vinegar), but be careful with the dosage, as its flavor is stronger than that of lemon. Use it sparingly to avoid significantly altering the taste of the fruit.
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