Strange scent after baking oak branches

[JaxonPhoto]

I decided that I'd like the look of oak branches in my vivarium, so I soaked them in boiling water for 30 minutes, then baked them at 425-450°F in the oven for 1 hour. I've done this in the past, and each time the branches come out, they produce this unpleasant smell with the slightest touch of water. I'm sure some of you know exactly what I'm talking about and I have no clue how to resolve this problem.

Any tips would be greatly appreciated, thank you!

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