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Old 10-10-2003, 09:14 PM
Wesley Clark Wesley Clark is online now
Join Date: Aug 2003
why does lettuce turn brown

If i get a bag of shredded lettuce it turns brown in a couple of days, why does it do this? is it due to Oxygen, water or what? Ive heard and discovered that a paper towel in the bag will slow down the rate of browning but how does the paper towel work. if browning is due to moisture i can understand how it would work but if its due to oxygen that makes no sense. Do any companies sell little h2o and/or oxygen absorbing packets (like the kind you find in bags of beef jerky) that you can put in lettuce bags?
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Old 10-10-2003, 10:49 PM
eunoia eunoia is offline
Join Date: Apr 2001
From here.

Russet Spotting. A common disorder due to exposure to low concentrations of ethylene which stimulates the production of phenolic compounds which lead to brown pigments. Russet spots appear as dark brown spots especially on the midribs. Under severe conditions, russet spots are found on the green leaf tissue and throughout the head. The disorder is strictly cosmetic but makes the lettuce unmarketable. Ethylene contamination may occur from propane fork lifts, transport in mixed loads, or storage with ethylene-generating fruits such as apples, pears and peaches.

Brown Stain. The symptoms of this disorder are yellowish-reddish-brown large, depressed spots on the midribs mostly. These may darken or enlarge with time. Brown stain also appears as reddish-brown streaks in some cases. Brown stain is caused by exposure to above 3% CO2 atmospheres, especially at low temperatures.
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Old 10-11-2003, 04:03 AM
Ice Wolf Ice Wolf is offline
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Join Date: Jan 2001
Location: Auckland, New Zealand
Posts: 8,378
According to this site, it's best not to store lettuce leaves with apples, pears or bananas, because they release browning ethylene gas, also. Best to store in plastic wrap in your refrigerator.

The paper towel addition could be to absorb extra moisture. However some sites recommend using damp paper towels, so YMMV.
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Old 10-11-2003, 08:12 AM
Shrinking Violet Shrinking Violet is offline
Join Date: Jun 2003
Re: why does lettuce turn brown

Originally posted by Wesley Clark
If i get a bag of shredded lettuce it turns brown in a couple of days, why does it do this?
Perhaps it has been shredded with a metal blade - this causes browning, tho' I'm not sure why. Lettuce should always be cut with a plastic blade, or better still just "torn", to prevent this.

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Old 10-11-2003, 09:11 AM
Roches Roches is offline
Join Date: Aug 2003
My mother used to tell me the spots were iron -- I think so I wouldn't refuse to eat spotted lettuce. I never found out what it really was.

Shrinking Violet: I have a plastic 'lettuce cutter', which is horribly ineffective and tends to turn lettuce into a runny, green pulp. Since I like to shred lettuce into very thin strips, I prefer to use a sharp chef's knife instead. It doesn't turn brown if I use it quickly.
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