I'm looking to build a baking station for some serious bread baking and wanted to have a wooden butcher block countertop since it was softer, warmer and cheaper than wood. Of course, I fell in love with black walnut wood and can't imagine using anything else.
Unfortunately, my husband pointed out that there is a substance in Black Walnut trees called Juglone that is toxic to most plants, and is antibacterial, antiviral, antifungal, etc. It's found mostly in the leaves, husks of the seed, and the roots, but there is also some in the wood/bark. It's so powerful that the juglone from black walnut also is a great natural remedy for Candida yeast infections!
Which brings me to my main concern. If I am needing dough and letting dough rise on a black walnut counter top will the juglone actually kill my yeast and ruin my bread? I am NOT sealing the countertop with polyurethane, but simply using a mixture of mineral oil and beeswax.
I really want to put a black walnut countertop in, but if I can't bake bread on it what's the point?! Thanks for any thoughts anyone might have or experience with baking bread on black walnut counters or bowls.
Sincerely, Concerned
First, congrats on picking out a walnut baking station you love. Second, I seriously doubt that the walnut wood will have any impact on your sourdough, and I am virtually certain it won't kill your yeast. I read a link to the treatment as an antifungal, and that required that the boil the husks then extract the fluid, which means they greatly concentrate the stuff from the walnut. In contrast, you are using a walnut board, that usually will have flour on it. The walnut will at most be in contact with some extremely limited portion of your dough, and your dough is filled with yeast. When you say you will be using the counter, how do you intend to use it? If you use slap and folds, yes, there will be a fair amount of contact with the walnut, though it still won't account to much. If like most you use an electric mixer, or autolyse and then stretch and folds, and then just shaping on the counter, then a very minute part of the loaf will come in contact with the walnut.
I have not actually tried forming dough on black walnut, and will be out of town for the next few weeks, but if you like I will do an experiment, and form a loaf on black walnut.
... and I mean really not a tree expert, but I see that there's a lot of conflicting information about black walnut. All that disagreement makes me think the whole issue is over-hyped.
One of the things I read, one that at least seemed respectable, said that the actively-growing parts of the tree have most of the juglone, and the inner wood has less. Also - what happens to juglone when it's exposed to air and water? I certainly don't know.
I suspect you'll just have a strong and pretty work surface, with no real problem from walnut chemistry.