Why does an apple turn brown when cut and how to avoid it?
Nothing can be more irritating and repulsive in culinary terms than the sight of a freshly cut apple turning brown in minutes. A logical question arises: why does this happen, and are there ways to prevent the fruit's flesh from changing color? Among the most common answers is that the apple is beginning to oxidize. iron, which is part of its composition. But it turns out that things don't happen quite that way. And besides, there are many ways to stop the fruit from browning.
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Why does an apple turn dark when cut?
Apple pulp contains a huge number of substances that belong to a group of antioxidants called polyphenols, which inevitably begin to oxidize the moment they reach the surface of the apple. cut.
This process is triggered by the fact that polyphenols are able to interact with almost any chemical element.
When the apple peel is damaged, oxygen begins to penetrate the fruit, which in turn activates the apple's "rusting" process. Surprisingly, this is how the fruit protects itself from various insect pests.
If, for example, the apple skin is damaged caterpillar, brown "rustThe "pesticide" that forms at the entry point forms a protective coating that prevents further damage. It also makes the fruit unpalatable to pests and can even cause digestive problems.
When cutting
When chopping an apple cutAny fruit that has been cut by a knife inevitably darkens. This process occurs faster in some fruits, slower in others. And this has nothing to do with the amount of iron in the fruit. Moreover, the product changes color only along the cutting line.
When the apple's integrity is damaged, oxygen gains access and triggers chemical processes the fruit needs to protect itself. The fruit, through the interaction of its components, will simply render the cut unpalatable.
In the air
When we cut or bite an apple, we "break" the cells of the pulp, thereby exposing the oxygen in the environment to polyphenol oxidase, a chemical component of the fruit. This, in turn, oxidizes polyphenols to quinones, which then begin to interact with anything they encounter, such as proteins. As a result, dark pigments form on damaged apples.
Why do some apples brown faster?
The rate at which apple flesh darkens depends directly on the fruit variety. Sweeter apples contain minimal amounts of enzymes that react. Sweeter varieties can be left in the open air for much longer without changing color.
Also, the rate of browning directly depends on the ambient temperature. If you take one apple and cut it into 2 parts, and place one in fridge, and the other half in a warm oven, you'll notice that the half exposed to elevated temperatures will begin to darken in a matter of minutes. But the apple part in refrigerator will remain in its original form for up to 10 hours.
How to prevent apples from turning brown when slicing
An apple that has changed its color due to natural chemical processes looks far from appealing. And if you're using the pulp as a component of, say, a fruit salad, this can be downright dangerous. Therefore, some effort should be made to prevent the browning process from starting.
Use lemon juice
Apples turn brown due to the onset of oxidation. This can be prevented with regular lemon juice, which contains citric acid, a powerful antioxidant.
You can use freshly squeezed or preserved lemon juice.
This method works best only on sweet apples, as the tart juice will add a slight tartness without destroying the delicate flavor. There are two ways to use this product to protect fruit from oxidation:
- Apply lemon juice directly to the cut apple by spritzing the apple pieces with the liquid and stirring them in a bowl to distribute it evenly. You can also apply the juice directly to the cut apple with a pastry brush.
- Mix 1 tablespoon of freshly squeezed juice with 1 cup of cold water and soak the sliced apples in the resulting solution for 5 minutes. Then drain and rinse the slices.
To prevent darkening, you can use lime juice, because it also contains citric acid.
Use citric acid
Citrus juice or fresh lemons aren't always readily available. However, powdered citric acid is readily available. It will easily preserve apple slices while adding a slight tartness. Simply dust the fruit lightly with the powder.
Use sugar syrup
To prevent apples from browning, prevent them from coming into contact with air. This method is ideal for those who take sliced apples to school or the office. Wash the apple, cut it in half, remove the core, and then stack the slices, generously brushing them with sugar syrup.
How to dry apples so they don't turn brown
You can store apples in winter not only fresh. An excellent alternative in terms of taste and health is drying, harvested in the summer and fall. However, dark slices will look unappetizing. To preserve the natural color of apple flesh when drying, use proven culinary life hacks.
By blanching
To prevent apple slices from browning during drying, you can blanch them. This procedure "disables" the enzymes in the pulp and prevents them from reacting with oxygen in the air. To do this, simply place the apples in a pan of boiling water for 5 minutes, then remove and rinse with cold water. Then dry the apples using your preferred drying method.
Using a saline solution
Salt is a natural preservative and will effectively protect apples from oxidation. Create a solution of half a teaspoon of dried salt per 1 liter of cold water. Submerge the sliced apples in the solution and let them soak for 5 minutes. Remove from the water and rinse thoroughly with a colander or strainer. The pieces will not change color significantly if they are dried further.
