Sesame odours

So from my latest batch of all grain brown ale I'm getting slight sesame oil odours. Anyone got any ideas where this is coming from? (recipe - pale malt, crystal malt and goldings hops, dried yeast).

Walker was talking about getting this in a Wolaver's Organic Oatmeal Stout...my best guess it comes from a darker grain. In any case, I tried a WOOS at a beer festival last weekend, and while I could detect a slight sesame flavor, I didn't mind it at all. Is it offensive to you?

No, not really, I just wish I knew where it was coming from. I was wondering if some rogue bacteria was causing it. The beer is quite a dark and caramally so maybe it's from the crystal malt in it.

I don't think it's bacterial as I noticed it in a commercial brew and someone else did, as well, in what was assuredly a different batch. I had another thought last night after I posted, and that's that 'sesame flavor' comes from the oils in the sesame seeds. I'm thinking it could potentially be a combination/interaction of the flavor compounds from the darker grains plus some oil from the hops. Although hop oils are generally said to contribute 'floral', or 'citrusy', or 'spicy' flavors, perhaps in some combination and/or processing with grains it is possible to wind up with a 'sesame' type flavor.

It is quite a hoppy batch. Maybe those hop oils are contributing. It's strange but sesame oil and caramel flavour are very similar. Maybe the hop oils are just pulling the caramel flavour from the grains into the sesame flavour.