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?
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.
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.
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.
Julie
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.
The problem is your buying a bag of salad. The head of lettuce has been broken apart a week, or two ago. If you want your salad to last longer buy a head of lettuce. Break it apart with your hands. If you use a knife the edges will turn brown. Once you break it apart you can add any additional ingredients you like.
My salad is:
1 Head of lettuce (broken by hand)
1/2 onion (sliced into 1/2 circle slices
Carrots ( I use a peeler and peel it with short strokes)
cucumber sliced
tomato wedges
As some posters have already mentioned, it’s the ethylene gas that is causing the browning/wilting of lettuce. Buying it shredded doesn’t help either as they usually use older produce that are visually unappealing for customers to buy whole. The easiest improvement you could make, (other than to buy fresh, whole lettuce), is to use those green produce bags that absorb ethylene. Wash and dry your lettuce and keep them in the green bags to keep it fresh for a week or longer. I add a dry paper towel in mine just to absorb extra moisture.
I’ve heard this too about cutting with a blade, regardless of metal or plastic. But I thought this was an old wives’ tale. As far as I know, there’s been no scientific basis or proof to support this.
Or maybe it’s zombie lettuce.
I grew up thinking the rusty spots were a kind of diarrhea concentrate.
Neither have I. I think it’s one of the many myths of chefs.
Anyway, since when I don’t cut the lettuce I;m going to eat it within a half hour, how much browning of the edges can happen? And will I even notice it, when it’s all mixed up with carrots, cucumbers, peas/beans, dressing, etc.?
I believe that the idea is that cutting with a knife causes individual cells to burst open, allowing their contents to react to oxygen, while tearing separates cells without breaking them.