discoloring of onions, blackness

[kartman35]

But the OP says that he washes the knife between vegetables and is still having this issue...Perhaps not often enough?
How often should we be wiping the knife to prevent this? In between each onion? Every 5 onions? Or in this case is it because the specific cladding that Tojiro uses is more reactive than other carbons as has been suggested by some of the replies?

[Jmadams13]

Not quite sure it's only the cladding. I've done tests by only putting the exposed edge into an onion, apple, pear, artichoke heart, and they all turned black or greenish, with only contact with the edge. Yeah the cladding is bad, but that's not the only thing reacting.

[Jmadams13]

Im pretty sure it's possibly a lower quality white steel Tojiro uses in this line to keep the cost low

[JBroida]

The more reactive the steel and the more acidic the food, the more wiping

[kartman35]

Im pretty sure it's possibly a lower quality white steel Tojiro uses in this line to keep the cost low

Are there differing qualities of white #2? I was under the impression that white #2 is always Hitachi steel company's same white #2...

Or did you mean that the steel was hardened less optimally ?

[Squilliam]

Try running boiling water over the knife. It sorted out my stripped 210 ITK.

[Jmadams13]

I've done that too, only worked on the stripped knives. I don't have a problem with it, I've gotten used to it, I just was sharing experiences with the OP.

I'm not sure of different quality whites, just what I have seen

[kalaeb]

Not all white steel is created equal. General wiping should help with black onions. How often do you wipe your blade? When I first get a carbon knife, I wipe frequently until a patina forms. But it sounds like maybe even that is not enough. Good luck

[Timthebeaver]

iirc there used to be white #2 type A and B but not any more. All white steels have the same specs for impurities (P and S) iirc, only the carbon content differs ( #1 highest C, #3 lowest).

[mpukas]

+1 to the cladding being reactive, in my experience.

Different carbon steels and claddings are going to react differently with different foods, and will also take patinas differently. The Yusuke white #2 knives I use have built up patina and still have mild reactivity to onions and cabbage. Iron cladding reacts much more strongly than a good quality carbon hagane. KU finish helps reduce reactivity, so stripping yours off only makes it worse.

I've seen Jon's vid, and I think his suggestion for wiping a carbon blade on a damp towel while cutting reactive foods is a good technique, however, I don't think it's always practical in a pro kitchen if you have to do large quantites - it'll suck up valueable time. Seconds add up.

I know a chef/owner who won't allow ANY carbon knives in his kitchen, as he doesn't want to risk the reactivity w/ foods. It may be safe, but the off color and odor are not acceptable.

I'm under the impression that white #2 steel is a product of Hitachi, therefore there are not "other" white steels (same for white #1, white #3, blue #1, #2, #3, etc). But as always I could be wrong...

To the OP, unfortunately, you may have to look to other options in semi-SS or SS. There are certainly not enough options out there for a carbon core and semi-SS or SS cladding.