what's the reason behind a cut apple's turning brown when exposed to air for a few minutes?

Answer 1

Apples and other produce (e.g., pears, bananas, peaches, potatoes) contain an enzyme (called polyphenol oxidase or tyrosinase) that reacts with oxygen and iron-containing phenols that are also found in the apple. The oxidation reaction basically forms a sort of rust on the surface of the fruit. You see the browning when the fruit is cut or bruised because these actions damage the cells in the fruit, allowing oxygen in the air to react with the enzyme and other chemicals.

Answer 2

Apples and other produce (e.g., pears, bananas, peaches, potatoes) contain an enzyme (called polyphenol oxidase or tyrosinase) that reacts with oxygen and iron-containing phenols that are also found in the apple. The oxidation reaction basically forms a sort of rust on the surface of the fruit. You see the browning when the fruit is cut or bruised because these actions damage the cells in the fruit, allowing oxygen in the air to react with the enzyme and other chemicals.
The reaction can be slowed or prevented by inactivating the enzyme with heat (cooking), reducing the pH on the surface of the fruit (by adding lemon juice or another acid), reducing the amount of available oxygen (by putting cut fruit under water or vacuum packing it), or by adding certain preservative chemicals (like sulfur dioxide).

On the other hand, using cutlery that has some corrosion (as is seen with lower quality steel knives) can increase the rate and amount of the browning by making more iron salts available for the reaction.

Answer 3

in case you're cooking it, it is named "carmelization". The sugars interior the apple are reacting with the warmth. in case you decrease an apple and it is uncovered to air, it is, opposite to undemanding theory, not oxidation. The bacteria are uncovered to the apple, using fact the exterior is what retains the apple secure. The exposure to air helps the bacteria breath, the only oxidation in contact is the bacteria getting the air they desire. The bacteria will banquet on the abundance of sugars interior the apple, and the brown is the eaten factors, coated with, er, bacteria "poo". i'm hoping that I helped!

Answer 4

I can't recall the name of the chemical, or the reaction, but I just saw on the food network (Good Eats - alton brown) that it's the same process that causes avacados and bananas to turn brown. Use citric acid (lemon juice) to prevent it. The show said it's also the same chemical that is activated when people tan....check out Foodnetwork.com - goodeats- guacamole....

Answer 5

The brown you see is a kind of "rust". Iron in the apple changes to a different type of iron when exposed to air.

http://www.wikihow.com/Keep-a-Cut-Apple-from-Turning-Brown
"An apple will soon turn brown when cut, due to the conversion of ferrous iron to ferric iron."

Answer 6

The cut surface oxidizes.

Answer 7

Sugar and air do not mix well. Use a little lemon juice to keep this from happening.

Answer 8

oxidisation...add lemon...it won't turn brown

Answer 9

oxidation... not really sure.