odd flavor with some yeast strains?

[Legume]

So I reciently made a belgian pale ale with Belgian Abby II, and it has a distinct flavor that I have precieved in 2 other batches over the last few years.

I can only describe the odd flavor as sweet/malty and mushroomy. The final gravity of the beer is low enough that there should not be much percieved sweetness, but there is. The mushroomy flavor reminds me of the yeast autolysis flavors that are presant in good champagne. I am confident that these flavors are not due to yeast autolysis...but the mushroomy flavors in many champagnes are the closest thing I can relate it to.

I have had this same combination of flavors previously in a Dunkelweisen made with WPL300, and in a Belgian made with T-58 dry yeast.

To complicate things, I am a gluten free brewer and all of these were all-grain batches made with millet, buckwheat, and rice (no barley or wheat)...but I brew alot and dont normally get these odd flavors at all.

Any ideas where this is coming from or what is causing it (other than it is clearly related to these more charicterfull yeast strains).

Thanks,

 

[masonsjax]

The mushroom descriptor makes me think maybe it's an oxidation problem. If that's the case, be very careful about splashing the wort after yeast was added and especially during transfer or bottling/kegging.

If it's not oxidation, maybe it's stressed yeast. Are you pitching enough yeast and controlling the fermentation temperature?

 

[Legume]

Thanks masonsjax,

I am relativly carefull about oxidation, I dont secondarry, and I dont splash a lot when it goes from primary to keg...but it is possible that oxidation is a component of the problem.
There are definately people who go to furthur lengths than I do to avoide oxidation.

Stressed yeast is a posibility. Because I am brewing gluten free, I make several sucessive starters with sorghum syrup to culture the yeast away from the gluten in the liquid media it is sold in. Sorghum syrup wort is lower in available nitrogen than barley based worts.
It is possible that I stressed the yeast by culturing it over several generations in a wort with inadequite or borderline FAN.

Fermentation temperatures were maintained in the middle to high end of the range recomended by white labs (68 to 72).