When being exposed the meat from certain fruits to the action of the air we can observe how it is darkened lapsed some instants.
This happens with fruits like the apple, the pear, the banana… and with other foods like the potatoes or the mushrooms, to put algunoes examples.
This pardeamiento process calls himself oxidation, because it is the result of the action of the contained oxygen in the air in combination with the chemical compounds of the fruit, in short on the fenoles.
In the reaction an enzyme intervenes as catalyst: the polifenol oxidasa (PPO), thanks to which the fenoles combines with the oxygen to become quinonas that you polimerizan or they react with groups amino of different compounds forming colorful compounds that you/they receive the name of melanins and that they have properties antimicrobianas, and that they could be a mechanism of defense of the vegetables against infections.
The citric acid is oxidized with great easiness and it can be used to eliminate the oxygen and to avoid that the fruit is darkened. For it, if it is soaked in lemon juice the apples cut in sheets they will remain clear for much more time.
In the same way, if we seek to prepare a Macedonian of fruits we will begin obtaining the orange juice and to go introducing in him the apple, pear and banana, because the acid will avoid them to be darkened.
He/she notices sabionda: The compound fenólicos classified as secondary metabolitos of the plants, is those products biosintetizados in the plants that possess the biological characteristic of being secondary products of their metabolism, and the chemical characteristic of containing a group fenol at least in their molecular structure. Many are defense products before herbivores and patógenos, others provide mechanical support to the plant, others attract polinizadores or dispersores of fruits, some of them absorb the ultraviolet radiation, or they act as agents alelopáticos influencing in other plants.
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