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Thread: discoloring of onions, blackness

  1. #1
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    discoloring of onions, blackness

    Greetings,
    I have a Tojiro Shirogami ITK 240mm knife. It dis-colors my onions. They turn blackish or are dirty looking. I work in a restaurant and the cooks are pissed What should I do to make this better?

    I wonder if i should force a patina with hot vinegar bath or something. Any input would be wonderful... the cooks hate me.
    Andy

  2. #2
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    a forced patina should help. do you use a damp towel after every few slices to keep the dirt and contamination between other food items down? perhaps coating it with a light film of mineral oil could help. i forced a patina on my 1095 steel chef knife and keep it regularly oiled and that seems to keep discoloration down.

    my other chef knife that's monosteel carbon came with a patina since i bought it used so that doesn't discolor food at all.

    let's wait for the others to chime in.

  3. #3
    Senior Member Jmadams13's Avatar
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    I have a few from that line, so I have some input, and some bad news...

    It will probably never stop. I have forced countless types of patinas, and a lot of natural patinas, and they still react like a mofo. How I get around it, dot cut anything with them that's not going to be cooked, unless I'm at home, then I don't care.

    It's even worse after you remove the KU finish. The steel does take a blazing edge though, so its kind of a trade off

    Sorry this isn't very helpful, just feel the need to be honest.
    "This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption.. Beer!" -Robin Hood, Prince of Thieves, Friar Tuck

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    Senior Member stevenStefano's Avatar
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    I've never used a carbon knife that didn't turn onions black. Even knives with heavy months-old patinas and many different steels, it didn't matter. Cut onions with a different knife

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    I've never used a carbon knife that didn't turn onions black. Even knives with heavy months-old patinas and many different steels, it didn't matter. Cut onions with a different knife
    my 1095 old hickory after i thinned it and exposed more "new" metal and it turned onions grey. but never black. but after cutting with it more and wiping it down every few cuts then letting the knife steel's patina settle a bit, the reaction pretty much went away. but i just had to be safe and forced a patina anyway.


    It will probably never stop. I have forced countless types of patinas, and a lot of natural patinas, and they still react like a mofo. How I get around it, dot cut anything with them that's not going to be cooked, unless I'm at home, then I don't care.
    holy crap on that! i've never heard of knives to get that bad that it won't stop reacting to food. is monosteel shirogami really like that? or is it just tojiro's? maybe it's coz of their heat treat or whatever

  6. #6
    Quote Originally Posted by stevenStefano View Post
    I've never used a carbon knife that didn't turn onions black. Even knives with heavy months-old patinas and many different steels, it didn't matter. Cut onions with a different knife
    I'll have to check again, but I think my Marko 52100 doesn't really discolor onions no matter how long the sit.

    As for the OP, I'd get stainless, but that's just me...

  7. #7
    Senior Member stevenStefano's Avatar
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    I've used carbon knives that seemed to be ok, but then the odd time the onions would discolour, which is still unacceptable to me.

  8. #8
    Senior Member brainsausage's Avatar
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    All of my carbons start out this way. IME you just have to put up with it till the patina sets in. Try cutting a lot of raw red meat/hot meats. Seems to help set a patina.
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    Senior Member DeepCSweede's Avatar
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    My 52100 ZK never had an issue so maybe 52100 is a different beast.

    My Shig had some off smells and discoloring in the beginning but I cut a lot of proteins with it and haven't had a problem since.

  10. #10
    Senior Member Jmadams13's Avatar
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    It's not that it's carbon. I have plenty of carbons that don't react. I think just Tojiros white. Only on my ITK line is this a problem. On my 210, Kiristsuke, petty, and 240 gyuto. Some with the KU removed, some not.
    "This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption.. Beer!" -Robin Hood, Prince of Thieves, Friar Tuck

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