saison off flavour from heat mat?

[kirkcaldybrewer]

I just racked a split batch: 3 fermenters, 3 separate saison yeasts (WLP566, M29 and BE-134). I have two heaters (the flat mat type that goes under the fermenter) + controllers for each. The set-up I settled on was to control the WLP566 batch and M29 batch and then I balanced the BE-134 on top of the M29. (as in picture). I followed the "maltose falcon" protocol (maltosefalcons.com/tech/guide-saisons-and-saison-yeasts), controlling at 16C for 3 days. Then on the two "controlled" fermenters, ramped up over several days to ~1 degree below mfg max recommended temp (24C for 566 and 29C for M29). The uncontrolled BE-134 rose naturally to 22C.

Now, in tasting them all, the controlled ones both have unpleasant sulphur flavour/taste, while the *uncontrolled* one (BE134) smells and tastes delicious! The off-flavour is similar to what I've encountered with lagers, but never had it with a saison!

My theory is that the heat source, which is below the fermenters, cooked the trub leading to the off-flavour.

Does anyone have bad experiences with the direct heat from such a fermenter? Would it be better to have indirect heat (e.g. by putting fermenter in a box along with, but not touching the heat mat?

Any other advice?

 

[user 70770]

I’m gonna hop in on this thread. I just bought a heating mat that goes under the carboy but the information above makes me nervous about using it. I don’t want to overheat the beer and end up with nasty off notes.

 

[kirkcaldybrewer]

Normal duty for the heat mat is adding a little extra to get me from basement 16C to ~18-20C for standard ales. It does this admirably and I wouldn't hesitate to recommend using it for such.

However, heating up to 25-27C for this saison obviously had the potential to pump significantly more heat into the trub.

Next chance I get, I'll re-brew (I top-cropped both M29 and WLP566) but will heat indirectly this time. Will re-use same fermenters etc to try to isolate the heat-mat effect. Will post back the results.

I'll also report back on the off-flavour. I'm still hoping it fades in the keg as it does with lagers...

 

[Jtk78]

I went with wraps for my heating source. I figured I would get better all around even heat, and wasn't a fan of trying to heat the wort through the trub. I've used mine to get into the low 80s on a saison batch, and have not noticed and off flavors. I'd be interested in hearing how these turn out and if you brew again.

 

[kirkcaldybrewer]

Hi all, time for an update. Well this was more complicated than I though: after a couple of weeks, both unpleasant tasting batches began to taste nice, while the tasty one has developed a strong rotten egg aroma. So I’m thinking now, whatever my issue is, it may not have been the heat pads.