Circulation during fermentation

[The-Engineer-That-Brews]

I read (Yeast Propagation and Maintenance: Principles and Practices | Maltose Falcons) that continuous stirring is beneficial to yeast activity - indeed that seems to be standard practice for developing a starter.

I'm also thinking that when it comes to controlling the temperature of a 25 litre fermentation in a plastic bin, relying on air conduction from the environment (e.g. inside a fridge) is going to be a pretty slow process.

So I'm wondering about killing two birds with one stone and recirculating the fermentation via my heat exchanger. My objective would be to (a) efficiently control the temperature by conduction and mixing; and simultaneously (b) continuously 'rouse' the FV to get a more complete fermentation.

I suppose I could also do either one without the other - e.g. by putting a magnetic stir-bar in the FV; and/or using an immersed coil for the heat exchange...

Anyone got any thoughts on this?

 

[DarrenSL]

I think re-circulation wont add much benefit but at the same time could increase risk of oxidation and infection (more equipment to sanitise). In a yeast starter you want to get lots of oxygen in and to maximise the sugar conversion to get more yeast. The wort from the yeast starter isn't important and is usually thrown away.

An immersion coil for heat exchange has merit (and some fermenters come with this type of solution). Afaik commercial breweries don't stir or recirculate and control temperature with a glycol jacket.

 

[Neil Whittaker]

I was thinking of moving the Wort / Beer in the FV, from so that when I dry hop i could increase my hop utilization within my 2-3 day window. Since my FV is a FermZilla, oxygen exposure is not an issue. However, large amount of dry hops introduced via the collection jar sometimes get stuck. Maybe introducing a stir bar to the collection jar might help.

 

[DarrenSL]

You might find your stirrer bar gets stuck. If you want to circulate the hops more, you could force some CO2 up through the wort from the bottom tap (as suggested by the Verdant head brewer here... ). I don't know if that would lift the hops out of the collection jar though.

 

[The-Engineer-That-Brews]

Thanks for the observations all - yes... on reflection I'm tending to agree that circulating the wort doesn't add a lot. Might do a small scale trial just to see what happens.

On the other hand I do like the idea of fitting a dedicated heat exchanger coil inside the fermenter, and I can easily do that with a couple of 1/4" bulkhead fittings. It sounds better than using the immersion chiller anyhow.

Supplementary question: is it going to be OK to use copper pipe in the FV, or would plastic be a better bet? EDIT: OK, having checked, it is NOT a good idea to use copper in the FV (here's why)

 

[peebee]

I've done it! It wasn't a great experience and I'm unlikely to do it again.

I used the disinfected production coils of a shelf cooler and recirculated through them. What I did wrong was used silicon tubing to connect cooling coils to fermenter. I had no idea then how permeable silicon rubber is to oxygen. Yeast growth went into overdrive and clogged up the pipes. Any beer in the silicon pipes oxidised to vinegar either through the action of yeast (it can do that, but only after depleting sugars) or else the action of otherwise latent acetobacter (probably the latter - at a guess). The clogged pipes were a blessing, preventing the bulk of beer (45L) turning to vinegar.

There is increasing paranoia associated with copper pipes, to the point that copper is being ripped out of buildings and replaced with SS or plastic (especially in the USA). Copper will dissolve into acid water (and therefore beer) and over time could possibly (?) build to toxic levels??? I wouldn't worry much about copper, but perhaps would avoid it in a fermenter when alternatives are available.

Interestingly (perhaps) while preparing the water for my last brew, I recirculated through the jacket of my HERMS coil as per usual. My HERMS coil is not in the HLT, instead the HLT water is pumped around the HERMS coil's "jacket" It is constructed from copper. Water treatment includes acidifying the sparge water (until below pH 5.5). I forgot I was doing it for 4-5 hours and the water ended up tinted a very pale blue!

 

[Tony Palmer]

Stirring or re-circulation in an active fermentation is not a good idea. There are in any case natural convection currents in a fermenter, and it is particularly important to maintain good mixing before adding the yeast. Gentle stirring is only used commercially in yeast storage plants to prevent local heat build up in the stored yeast.

 

[foxy]

I read (Yeast Propagation and Maintenance: Principles and Practices | Maltose Falcons) that continuous stirring is beneficial to yeast activity - indeed that seems to be standard practice for developing a starter.

I'm also thinking that when it comes to controlling the temperature of a 25 litre fermentation in a plastic bin, relying on air conduction from the environment (e.g. inside a fridge) is going to be a pretty slow process.

So I'm wondering about killing two birds with one stone and recirculating the fermentation via my heat exchanger. My objective would be to (a) efficiently control the temperature by conduction and mixing; and simultaneously (b) continuously 'rouse' the FV to get a more complete fermentation.

I suppose I could also do either one without the other - e.g. by putting a magnetic stir-bar in the FV; and/or using an immersed coil for the heat exchange...

Anyone got any thoughts on this?

Not needed on a home brew scale, as mentioned above there is enough movement from the exothermic action of the fermenting yeast. Commercial scale with the tall fermenters, yes, they have paddles continuously stirring the yeast. I believe it relieves the pressure too.

 

[Tony Palmer]

Paddles in tall fermenters are fob breakers to control over foaming and they do not stir the medium.

 

[SteveH]

Sounds similar to a Yorkshire Square process for rousing - I can't imagine much need for that on a homebrew scale though, where the yeast activity naturally mixes the fermenting wort in a relatively small container?

 

[Neil Whittaker]

My last brew which I got the hops stuck in the collection jar, I picked the whole FermZilla up and shook it for 10 minutes. This got all the hops into suspension and was a good work out for the arms. My NEIPA which is in the keg now, tastes great.

 

[peebee]

… Supplementary question: is it going to be OK to use copper pipe in the FV, or would plastic be a better bet? EDIT: OK, having checked, it is NOT a good idea to use copper in the FV (here's why)

Actually that link doesn't say it's a bad idea to use copper in the FV. But I can't see anywhere where it suggests it's a good idea either! It has been known for a while that allowing paranoia to dictate the removal of all copper from the hot-side equipment has lead to problematic fermentations and advice to chuck a length of copper pipe into boilers that have mistakenly had all the copper purged from them (or use nutrient salts that contain copper).

But thanks for the link! What I didn't say in my last post was I used the "pale blue brewing liquor" anyway! The link confirms half the copper content that would harm a human would kill the yeast, and then I wouldn't have the beer to drink anyway!

I can spread rumours that copper is lethal to Covid-19, and then no-one will hesitate drinking the beer. Or I can slap Hazchem warnings on it and keep it all for myself!

 

[The-Engineer-That-Brews]

Actually that link doesn't say it's a bad idea to use copper in the FV. But I can't see anywhere where it suggests it's a good idea either! It has been known for a while that allowing paranoia to dictate the removal of all copper from the hot-side equipment has lead to problematic fermentations and advice to chuck a length of copper pipe into boilers that have mistakenly had all the copper purged from them (or use nutrient salts that contain copper).

But thanks for the link! What I didn't say in my last post was I used the "pale blue brewing liquor" anyway! The link confirms half the copper content that would harm a human would kill the yeast, and then I wouldn't have the beer to drink anyway!

I can spread rumours that copper is lethal to Covid-19, and then no-one will hesitate drinking the beer. Or I can slap Hazchem warnings on it and keep it all for myself!

Haha!! Splendid idea :-) :-)