what cause an apple that is cutted into pieces to turn brown?

Answer 1

apples, mushrooms, and potatoes all have high levels of the enzyme tyrosinase. when oxygen is present (i.e. when you cut/peel it), this enzyme converts tyrosine to melanin, which is a dark pigment. if you cover the sliced apple, potato, etc. with water in a bowl, it will keep it from turning brown.

Answer 2

Fruits and vegetables put on the buffet line often can change color and loose a certain eye appeal after being out on display for just a few minutes. Fruits such as pears, apples and banana may turn brown and look unappetizing.
In this experiment you will investigate a way to keep fruits good looking longer than usual using natural acids. The acid should help by stopping the cause of the color change.
The cause of the discoloration in fruit is usually due to oxidation of the fruit or vegetable; oxygen combining with the fruit.
Fruits such as lemon, lime and orange are called citrus fruits because they contain citric acid. Most of these fruits also contain ascorbic acid or vitamin C. You can measure the presence and strength of these acids using pH paper.
So one of the ways to keep cut fruits looking fresh longer might be to squeeze lemon or orange juice on the fruit, and keep them from quickly turning brown.
Browning fruit
Oxygen in the air causes fruit to brown. This is oxidation. The same thing happens when iron rusts. Oxygen combines with the fruit to turn it a brown color.

Answer 3

Apples undergo a process known as oxidative browning due to oxygen reacting with polyphenols released from the cut cells. Polyphenol oxidation takes place after physical injuries inflicted to fruits and vegetables during harvesting, storage or due to food preparation activities. For fresh fruits and vegetables, this is often harmful because the yellow and brown pigments impart an undesirable appearance. In some cases this color development can be desired,as during the harvest of dates or for some beverages (tea or cider). The first step of the browning is the oxidation of o-diphenols to highly reactive o-quinones. This reaction uses oxygen and is catalyzed by the enzyme polyphenol oxidase. The o-quinones go on to react with other compounds released at the cut surface by several different pathways to produce secondary products with the characteristic brown color. A technical review of this can be found in Nicolas JJ, Richard-Forget FC, Goupy PM, Amiot MJ, Aubert SY. 1994 Enzymatic browning reactions in apple and apple products. Crit Rev Food Sci Nutr. 34:109-57

A number of compound have been proposed to inhibit browning, mostly working as anti-oxidants to prevent the oxidation catalyzed by polyphenol oxidase. For a technical discussion of this you might read: Son S.M.; Moon K.D.; Lee C.Y 2001 Inhibitory effects of various anti-browning agents on apple slices. Food Chem 73:23-30

I hope this helps...

Answer 4

There are some chemicals in the apple that mix with oxygen in the air to turn it brown its called oxidation

Answer 5

Steel blade of the knife. Never use a knife to chop lettuce unless its going to be used up quickly. It will also turn brown

Answer 6

I think after air hits it and stuff it kind-of starts to rot.

Answer 7

oxygen and its a chemical reaction SAWEET!