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oxidation.
the oxygen in air reacts with the surface of the newly cut lettuce and turns it brown.. i think the surface of the knife can have a small layer of oxidation on it too, so that can affect the lettuce as well or at least that's what i think happens....... you can get plastic lettuce knives....
Most fruits and vegetables have two chemicals called enzymes and poly-phenols. When these two chemicals combine, they "oxidizes" which turns fruits and vegetables brown. These two chemicals are usually separated by a cell wall which breaks down over time, but cutting and tearing can damage these cell walls causing browning at the edges.
Usually metal knives are thought to brown lettuce faster then tearing or using plastic lettuce knives though there is very little support for this. Either method will cause browning, and lettuce is usually consumed quickly after being cut thus browning is not an issue.
Wiki User
∙ 12y ago
Wiki User
∙ 8y agoThe most common reason for browning on lettuce is a chemical process known as oxidation. Enzymes activated by cutting the leaves or stems produce compounds that result in brown stains, especially at the base or anywhere the leaves are damaged during harvest and storage.
Wiki User
∙ 16y agoLettuce turns brown when it goes bad and rotten because air traps odors and bad air that makes it go bad and stuff.
Wiki User
∙ 11y agonbjbb
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Why does lettuce turn brown when you cut it with a metal knife?
The lettuce does not turn brown due to it being cut with a metal knife. It turns brown due to oxidation.
Does it make a difference whether you shred lettuce or cut it with a knife?
Not as far as nutritional value. Lettuce that is torn doesn't turn brown as fast though.
Why is it important to cut lettuce with a sharp knife?
It is actually better to tear lettuce than it is to cut it, especially if you want it to stay fresh. Cutting lettuce makes it turn brown and wilt faster then it does when you tear it. But if you do cut it use a sharp knife because that will keep the edges clean, instead of being ragged. Also the metal in the knife causes a reaction that will make it wilt and go bad.
Why do you tear instead of cut mushrooms?
Like lettuce, if you cut mushrooms with a stainless steel knife the cut edges tend to brown or discolor. They are also delicate so when cutting through thicker pieces bruising may occur.
Should you cut lettuce with a knife or rip it by hand?
* Yes, you should rip the lettuce because the metals in a knife blade will react with the lettuce and cause oxidation, which will speed the browning of the lettuce. If the lettuce is to be used right away, then cutting with a knife is fine; but if not, then tearing is the best method. * People rip lettuce because a stupid salad-dressing commercial from the '70s said to do so. There is no good reason to rip vs cut. The answer above is incorrect: Some knives do what it says they do, and others do not. Oxidation occurs whether you rip or cut. For lettuce, it does not speed browning. Test it yourself. * The previous answer is incorrect: Metal knives do cause oxidation of lettuce and other vegetables. There are specially made serrated plastic knives for cutting lettuce. If you don't wish to purchase one of these knives, the best method is to tear your lettuce. == ==
How do you remove brown from lettuce?
You just cut that leaf off, hope it helped! X
If you put raw cut up potatoes in marinade will they turn brown?
no they will not turn brown
What causes rust color on iceberg lettuce?
Iceberg lettuce changes color because of enzymes. When lettuce is cut, enzymes from cells are released. One enzyme, polyphenoloxidase, reacts with polyphenol molecules in the lettuce, forming brown pigments.
Why does lettuce lose its vitamins and nutrients when it's cut with a knife?
Because your cutting it open and as you do that the juice comes out and they come out with that but it doesn't have a huge amount of them
Do kiwis turn brown after you cut them?
no, kiwi doesn't turn brown after you cut it
How do you cut romaine lettuce?
I have always heard it is best to tear lettuce into bite size pieces rather than cut it with a knife. Tearing it will break the bonds between the cells, making for less water loss. Cutting lettuce slices through cells, allowing the water to escape. I have also heard that cutting lettuce (especially with a metal knife) will cause it to turn brown more rapidly, possibly due to a chemical reaction between the metal and the lettuce. It is much better if you tear it into the desired size. Some also prefer to tear the green leafy parts off the center rib, as the rib can be a little tough. Bite-size pieces are usually around one inch in diameter so they are easy to fork up and don't have to be folded to get them in your mouth. Edit: I cut about 15 heads of romaine a day where I work and I'll tell you preservation is not a problem if you buy fresh, store chilled and eat it in a reasonable amount of time. Even after being cut it's not uncommon for romaine to be fine into the third day if you just don't abuse it with hot or cold temperatures. The trick is just to cut what you want, and eat what's left tomorrow, you'll be fine. Also, I cut Romaine with a Zwilling Henckels 9 1/2in bread knife, and I have to say that if the lettuce is washed and spun after cutting then it really shouldn't matter. By the time you're seeing browning on the edges, that lettuce is going to be altogether past its prime anyway. The most important part there is spinning! Spin the heck of out of that lettuce.
When do apples turn brown?
when cut and exposed to air. lemon prevents browning. when extremely ripe they turn brown.
