Lettuce: cutting vs tearing

Discussion in 'Food & Cooking' started by siduri, May 11, 2013.

  1. siduri

    siduri

    Messages:
    3,599
    Likes Received:
    46
    Exp:
    At home cook
    This has probably come up before, but i'm probably older than most of you and have the prerogative of forgetting or telling old stories over and over/img/vbsmilies/smilies/smile.gif

    I never got that thing about not cutting lettuce with a knife. 

    Supposedly it gets brown around the cut edge. 

    I have never had lettuce brown around a cut edge any more than it browns around a torn edge. 

    But tearing implies some rougher handling than the smooth cut of a sharp knife. 

    I think it's one of those old wives' tales, or rather, since most chefs are men, old men's tales. 

    I've heard two lines of reasoning: 
    1. the "metal knife" explanation - presumably because iron and steel rust, cutting with an iron or steel knife will make the lettuce "rust".  I don't know the science of this, but it would mean that there is a chemical reaction with the steel and the lettuce.  It seems unlikely, but I'd be curious as to the explanation.  And if that is true, then what possible chemical reaction would there be with a stainless steel knife? 
    2. the bruising explanation - presumably cutting with a knife bruises the lettuce.  Really?  And grasping lettuce in your hands and tearing it doesn't bruise the lettuce?  i think it bruises it more, tearing leaving more cells open, torn, more surface area on the cut side than a nice clean cut with a knife, and the holding in the fingers to pull it also would bruise it
    What i notice is that lettuce left in the fridge will "rust" around any open edges, whether intentional cuts or tears or just the wear and tear of being shipped and all. 

    Has anyone tested this?  Considering the excessive amount of time it takes to tear lettuce, as opposed to cut it with a good sharp knife, there should be some good evidence. 
     
  2. teamfat

    teamfat

    Messages:
    4,019
    Likes Received:
    434
    Exp:
    I Just Like Food
    I've heard that tearing keeps the individual cell walls intact, while cutting does not.  So torn lettuce stays fresher longer.
     

    But a few decades ago in a restaurant scene I used a knife, no time to stand there tearing all day.

    mjb.
     
  3. genemachine

    genemachine

    Messages:
    1,423
    Likes Received:
    123
    Exp:
    Home Cook
    I find this highly unlikely. I wouldn't expect the cells to separate cleanly along the walls when tearing. However, science to the rescue. I will get my trusty old microscope from the cellar and have a look later.
     
  4. pollopicu

    pollopicu

    Messages:
    1,201
    Likes Received:
    53
    Exp:
    Professional Chef
    This doesn't really answer your question, but I'm assuming the purpose of your inquiry is to find a method that doesn't turn lettuce brown. Last year I purchased this knife.

    http://www.usfoodsculinaryequipment...rce=googleps&gclid=CJnU-sONjrcCFaYDOgodcmEAqw

    It works like a charm.

    I remember the first time I used it I had to cut a bunch of lettuce for next day service, so I took a HUGE leap of faith, cut it, covered it and placed it in the reach-in. I think I lost sleep the might before, and when I went to work i made a bee line to the reach-in to see if the romaine had turned brown, and it had not. It was as if I had cut it fresh on the spot.
     
  5. maryb

    maryb

    Messages:
    2,501
    Likes Received:
    181
    Exp:
    Semi pro/retired now
    Rust on lettuce is water damage, not from a knife.
     
  6. siduri

    siduri

    Messages:
    3,599
    Likes Received:
    46
    Exp:
    At home cook
    I can't see buying a special knife for lettuce when a regular knife never gave me any problem
    That's what i think
     
  7. pollopicu

    pollopicu

    Messages:
    1,201
    Likes Received:
    53
    Exp:
    Professional Chef
    Of course a real knife works fine with lettuce, but the plastic allows more time to lapse before turning brown. BIG help when you're in the food industry. 

    I'll have to disagree about the water damage. If that were the case, then the entire surface of the lettuce would turn brown upon contact with water...not just the cut edges.

    Lettuce turns brown due to oxidation.

    http://blogs.mcgill.ca/oss/2012/11/18/why-does-lettuce-sometimes-turn-brown/

    I think tearing lettuce is a more effective way of preventing lettuce turning brown so fast, but I don't like the look of it. I prefer clean cuts knives make.
     
    Last edited: May 12, 2013
  8. petalsandcoco

    petalsandcoco

    Messages:
    3,207
    Likes Received:
    156
    Exp:
    Private Chef
    There is an interesting article at Livestrong.com entitled : What Causes Rust on Lettuce ? The answers to me made perfect sense. I don't know about you ? What are your thoughts ?

    What is commonly known as rust on lettuce is technically known as "russet spotting." Rust on lettuce doesn't make the greens inedible, but it does make them unattractive. Russet spotting occurs because of a chemical reaction that involves ethylene gas, and it can be minimized with certain handling and storage practices.

    Ethylene Gas

    Ethylene gas is thought to regulate growth in plants and coordinate their ripening, Cornell University reports. Tractors, trucks and other machinery that have internal combustion engines also give off ethylene gas and can cause plants to ripen faster and develop rust spots. Fruits such as apples, bananas, peaches and tomatoes give off the highest levels of ethylene and greatly affect vegetables such as lettuce, which exude low levels of ethylene. Ethylene gas causes greens to yellow faster and causes rust on lettuce. It also causes carrots to become bitter and potatoes to sprout faster

    Minimizing Exposure

    Lettuce harvesters can reduce rust on lettuce by vacuum-cooling their harvest and storing it just above freezing temperature at about 34 degrees Fahrenheit. Cold temperatures reduce respiration rates in lettuce and slow the ethylene reaction. Well-ventilated coolers can help minimize ethylene exposure. Avoid storing your lettuce along with fruits, Cornell University advises. Potassium permanganate products can be used to absorb excess ethylene gas.

    Minimizing Damage

    It isn't simply the presence of ethylene gas that causes rust on lettuce; it is damage to the lettuce itself. This may occur during harvest, handling and transport. Bruised lettuce is more susceptible to the chemical reactions that occur with ethylene gas according to the University of California. Websites such as Salem Farms recommend tearing rather than cutting lettuce to minimize russet spotting, while other websites, including Recipetips.com, advise using plastic knives rather than metal to deter rust on lettuce. However, damage is damage, McGill University's Office for Science and Society reports, in any way it is done: Simple aging will lead to rust spots on lettuce.

    Why It Occurs

    Russet spotting occurs as plant compounds known as polyphenols react with enzymes present in the lettuce. Normally, the polyphenols and enzymes don't come into contact with each other, but damage due to aging, handling and ethylene exposure allows the compounds to mix. The oxidizing effect allows polyphenols to link together and produce the reddish-brown pigment we know as lettuce rust, McGill reports. No one is truly sure about why russet spotting occurs, but the commonly-held belief is that this reddish-brown pigment offers some defense against plant attackers such as fungi and insects, the historical causes of plant damage.
     
  9. pollopicu

    pollopicu

    Messages:
    1,201
    Likes Received:
    53
    Exp:
    Professional Chef
    Yes, this is what happens when lettuce is cut, in any form, over a short period of time.

    I can't stand eating rusty lettuce. I don't serve it, and if I'm out I won't eat it. Not because it tastes different, but because it's unappetizing, to me at least.
     
    Last edited: May 12, 2013
  10. siduri

    siduri

    Messages:
    3,599
    Likes Received:
    46
    Exp:
    At home cook
    Yes, it all makes sense to me.  And what it means is that the question of tearing vs cutting is simply an aesthetic one. I actually think ragged looking lettuce looks better, but not better enough to be worth the effort.  And as for damage, it seems to me that the extra handling needed to tear it is going to damage it more than what would occur with a clean cut with a sharp (metal) knife through the whole head.  It makes it easier to wash too, since small pieces can slosh around in the water much better than large leaves, that can hold the various contaminants like dirt, bugs and snail droppings  (bla) in the folds and crevices of the leaves. 

    I never have occasion to wash lettuce in advance anyway. 
     
  11. ed buchanan

    ed buchanan

    Messages:
    3,355
    Likes Received:
    44
    Exp:
    Culinary Instructor
    I agree with the ethylene theory.    If you have flowers that are not opened if you put a wedge of apple  in a plastic bag then put flowers in it they will oen real fast. If you put apples next to bannannas  in a fruit bowl they will brown or ripen quickly. Apples are full of ethylene gas . Here in Florida Tomatoes are picked green whenthey want to ripen them  bingo a blast of ethylene gas.
     
  12. genemachine

    genemachine

    Messages:
    1,423
    Likes Received:
    123
    Exp:
    Home Cook
    The ethylen theory sounds plausible to me. I finally found the time to get out the microscope - at the tear edge of salad leaves, the cells definitely are ruptured.