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Fermentation Going Off

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Kai

Fermentation Assistant
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I started a plum lager last night. Nothing fancy, a can of Coopers Lager and a can of Coopers light LME. I boiled around 2kg worth of halved ruby plums in ~2 litres of water for 20 minutes with around 200mL of dry malt extract thrown in at the halfway mark (just because it was there), and when signs of fermentation were present I threw the syrup in as well as the plum pulp & skins suspended in a nylon laundry bag.

My wort was probably very well aerated as I filled the fermenter by sticking it on the floor next to the kitchen benchtop and running a benchtop filter, so the stream falls a good 2-3 feet and generates a fair head of froth.

I added the plum syrup (frozen) and pulp (chilled) last night before bed. This morning, it started frothing up through the airlock. I took the bag with the skins & pulp out which dropped the level by 3 litres (back down to 21), but it kept galloping on at a fair pace and foamed over again an hour or so later. The temperature is a sedate 20C.

What do you reckon is causing it? I thought that the high fructose content of the plums might have set the yeast off down a path of rampant vigour, but that's pure speculation. I was worried it might have been a particularly virile wild yeast from the plums, but I thought that a 20 minute boil would have eliminated that risk.

Any thoughts?

Oh yeah, and a pic: airlock
 

Justin

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He he. Look at that airlock. I haven't done the calcs but that looks like a heck of a lot of sugar. What with the 2 cans, the plums and the half kilo of DME that should be pretty damn high in gravity. sound like those yeastie beasties are just going hell for leather on the sugars.

Maybe cool it down to 18oC to try and slow things up. I wonder what the final grav is going to be??

JD
 

Kai

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Forgot to add, the initial gravity appeared to be around 1046. I'm sure it was higher than that though, as I think more sugar came out of the plums overnight.

I'd say you're right, it's probably just a case of the yeast being like a kid in a candy store. I'll stick it outside tonight which should drop it a degree or so.

I don't think the plums provided too much fermentable material to the wort, though. That 2 kilo's worth would be almost 90% water, I'd think. And it was 200mL of DME. What's the density of that stuff?
 

PostModern

Iron Wolf Brewery
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What yeast? The Coopers kit yeasts (they are ale even in the "Lager" kit) just do that. Give them heaps of headroom or fit a blow-off tube to the fermenter.
 

Kai

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I realised after I posted that I should have specified. I just used the Coopers yeast.

The bulk of my brewing is done with Coopers kits. Before this, the only ones I've had trouble with the yeast being too happy is with the stout.

Anyway, I've got the old girl sitting outside in the cold. It's dropped from 22 to 18-20. I'll bring it in in a few more hours.
 

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