Belgian Quad won't stop fermentation

[Paddybrewer]

Hi All

I'm a new member, but brewing for 6 years and I have always found myself reading various threads when I need advice on something over the years, so I thought I'd start my own.

I brewed a Quad at the end of June. OG was 1.090 (had aimed for 1.110, so was way off). My FG estimate (according to Beersmith) was 1.020. As of today (more than 5 weeks later) I am on 1.008.

My mash temp was good for a medium bodied beer, so it can't be that. I pitched 2 packs of Mangrove Jacks Belgian Ale M41. Fermentation went as expected in the beginning and slowed down as it approached 1.020, but then just kept going slowly and just doesn't look like it wants to end. I always taste the beer every time I check gravity and it tastes fine.

There was quite a bit of sugar in the recipe 500g Brown Sugar and 500g Candi Sugar (22l batch). I have used those amounts before without any problems, and anyway, I would expect that those sugars would have been eaten very quickly early on.

Anyone have any ideas?

Cheers!

PS: Excuse the metric units - I'm from Cape Town, SA

 

[Gnomebrewer]

I'm not familiar with that yeast, but it sounds like it could be a diastaticus strain. That means it can produce enzymes that cut some longer chain sugars into shorter, fermentable lengths. This can be a slow process, so (as you've experienced) fermentation can continue slowly for a while. At 1.008 it's probably about done though.

 

[Paddybrewer]

I'm not familiar with that yeast, but it sounds like it could be a diastaticus strain. That means it can produce enzymes that cut some longer chain sugars into shorter, fermentable lengths. This can be a slow process, so (as you've experienced) fermentation can continue slowly for a while. At 1.008 it's probably about done though.

Thanks Gnomebrewer
According to their website they say "Very High Attenuation", which most people will say is probably diastaticus. I'm happy with the flavour though - no fusels noticeable, so it's going to be a very easy drinking light-bodied beer at around 11%ABV. I better put a warning label on the bottles. Haha.

 

[Gnomebrewer]

it's going to be a very easy drinking light-bodied beer at around 11%ABV.

Dangerous stuff!

 

[davidabcd]

You got nearly the same attenuation so it looks normal in that respect. It's the drawn-out time, as you mentioned, that's puzzling. Do you ferment at the high end temp for your Belgian's? I'm very interested to watch this thread play out to see what the other knowledgeable people have to say.
Mostly, your post just makes me want to try Mangrove Jack.
Welcome to the forum.

 

[Protos]

At the end of June I made a Strong Golden ale with MJ M41. It's a beast of a yeast, it chomped the 1.070 wort down to 0.998. It took quite a time to fully ferment this.
Got exactly the same impression: tasty, clean and deceivingly easy drinking. I liked the resulting ale very much, it's bottle conditioning now.

I deep clean my fermenting and bottling equipment every time after brewing with M41 and M29, as the diastaticus could become a contaminant if it makes its way into other batches. I even separate empty bottles after drinking my diastaticus beers as I believe they need more thorough cleaning before reusing them.

 

[sweetcell]

I brewed a Quad at the end of June. OG was 1.090 (had aimed for 1.110, so was way off). My FG estimate (according to Beersmith) was 1.020. As of today (more than 5 weeks later) I am on 1.008.

don't trust those FG estimates. they're worthless. 1.020 for a quad is way to high, i can't believe beersmith would even put that number out there. that's more typical of a stout.

Anyone have any ideas?

diastaticus yeasts can take a while to complete their fermentation as the enzyme that breaks down long sugars does its work. so a long fermentation would be normal in this case.

only other thing that comes to mind is infection: if you got something else in there, like a wild yeast or brett, those could be chomping down.

PS: Excuse the metric units - I'm from Cape Town, SA

no apologies needed, it's the global standard. don't make excuses for the bubble that is the US

 

[rawl28]

Reading BLAM, this doesn't sound odd at all. I think these yeasts can't take their time to finish up especially on these larger beers. In the book he wrote, "Let the fermentation finish, perhaps at a higher temperature. It can often take as long to get the last few points of attenuation as it does for the first 80%"