The Effect of Rousing on Attenuation and Yeast Behaviour

[dlprice45]

After reading a bunch of (often conflicting) message board comments about rousing yeast to help a stuck fermentation I found this old 1939 Journal of the Institute of Brewing article on experiments with rousing. It suggests that rousing is indeed effective, especially slow continuous stirring of fermenting wort (impossible for most home brewers). It's a bit of a read but if you're interested check it out.

This gives me hope that my stuck 1.022 nut brown ale will lose a few more gravity points now that I've raised the temp and given it a good swirl with my mash paddle.

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1938.tb05836.x/pdf

 

[roastquake]

I thought the title sounded like a journal article

 

[BigFloyd]

After reading a bunch of (often conflicting) message board comments about rousing yeast to help a stuck fermentation I found this old 1939 Journal of the Institute of Brewing article on experiments with rousing. It suggests that rousing is indeed effective, especially slow continuous stirring of fermenting wort (impossible for most home brewers). It's a bit of a read but if you're interested check it out.

This gives me hope that my stuck 1.022 nut brown ale will lose a few more gravity points now that I've raised the temp and given it a good swirl with my mash paddle.

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1938.tb05836.x/pdf

I hope your mash paddle isn't wood and that the "good swirl" you gave it was a gentle one so as to not mix any air into already-fermented beer. I've done this before and it was a very, very gentle scooping of the yeast off the bottom with a sanitized metal spoon.

You weren't by any chance using S-04, were you?

 

[dangerbrew]

There are breweries in England that would commonly swirl their yeast during fermentation to rouse it due to how flocculent the strains tended to be.

I've not tried doing it myself other than just a few gentle swirls during primary, so can't say if it really helps a lot or not, but I've never had problems with my fermentation while doing it. Heck, why not? Rouse the sucker.

 

[roastquake]

I think I read that Samuel Smith's old brewery does this because their strain is highly flocculent, and if not roused it wont fully attenuate. I don't know if there are strains available to homebrewers that are so flocculent they need to be roused. I also wouldn't do it with a wooden mash paddle

 

[EarlyAmateurZymurgist]

I see that you fermented that batch with Mangrove Jacks Newcastle Dark Ale yeast. There's no way that that product is Scottish & Newcastle's yeast strain. I have the real thing in my yeast bank, and it is a beast.