1 Posted: Thursday, October 12, 2017 9:06 PM

Hi all,

I'm new to brewing and this is my first time posting on any forums so apologies if this has already been covered…

Basically, I've jumped straight into BIAB and have done five 20L batches in the past four months. I have been using the no-chill method and I have read about the need to adjust the hop schedule to counter the extra isomerisation of the hops as they are exposed to heat for longer. I have a basic fundamental understanding of this but have a question I hope someone can answer for me:

I am about to convert a 50L keg to a brew kettle so that I can brew bigger batches. I read somewhere that it isn't critical to use a food-grade plastic cube and some people simply cover the kettle or rack straight to primary and wait for the wort to cool before pitching the yeast. This appeals to me as it eliminates the need for an extra transfer from vessel to vessel and obviously eliminates the need for a cube altogether. I'm thinking that this should decrease the chance of infection or oxidation as wort only needs to be in two vessels throughout the entire process up to bottling time.

Basically what I need to know is: Will a 40L batch in one vessel take twice as long to cool than a 20L batch under the exact same external conditions? (I'm currently adjusting my hop additions by 10 minutes for 20L batches and if this is the case then I will just adjust by 20mins for 40L batches). OR.. is there some sort of exponential relationship between volume and heat loss that would mean I can't just double the time I delay the hop additions as I double the volume?

Any help with this would be much appreciated and I apologise again if this is a dumb newb question!

Cheers - Chris

2 Posted: Thursday, October 12, 2017 9:22 PM

Hi Chris, and welcome.

Firstly, I wouldn't be concerned about oxidation from transferring to a cube and then to the fermenter. That is a post fermentation issue; pre fermentation you actually want oxygen in the wort as it is beneficial to the yeast. It's probably advisable to try to limit splashing of the wort while it's hot, but many no-chillers pour the cooled wort into the fermenter from a height to splash it around and get some oxygen into it. I used to do that but now use an oxygen tank with a sintered stone to inject pure oxygen into the wort at yeast pitching time.

I don't think it works that way with cooling down taking twice as long for twice the volume. It probably does take longer, but I'm afraid I don't really know how much longer. The key though is how long it takes to drop below about 80C, as that's where isomerisation stops.

Leaving the wort in the kettle or in the fermenter is probably fine if you're only leaving it until the next day, but if the wort is going to be sitting for any period of time before being fermented then it's best in a sealed cube. The risk of infection is sweet FA if the process is done properly, i.e. wort transferred to the cube above 80C, preferably above 85C.

As for hop addition adjustments, it's not something I've ever consciously bothered with. However, I make up my own recipes so I've just played around with the late hop additions to achieve my desired outcome. I honestly think that's the best way to go about it rather than taking any notice of “hard and fast” rules that may not work for everyone's tastes.

Cheers

Kelsey

3 Posted: Thursday, October 12, 2017 9:23 PM

It will be a bit of trial and error, mate. I would keep the additions the same and adjust them in future batches if necessary. If you are risk averse then perhaps adjust the hop additions by 15 minutes.

40 litres will definitely take longer to cool than 20 litres but I am not sure if it will take twice as long.

I no chill but having always used a cube/Jerry can. I have never left the wort in the kettle to chill. I have read about people doing this without issues but I guess it has its own risks. Once the wort gets below a certain temp and it isn’t sealed then there may be more chance of infection.

4 Posted: Thursday, October 12, 2017 10:03 PM

Thanks guys, I suspected it might be one of those things that's near on impossible to quantify but now I can justify doing more brews in the spirit of ‘research’ :)

I think what I might do then is get enough ingredients to do an 80L batch and then do back-to-back 40L brews. One to get split into two 20L cubes and one to go straight into the primary until it has cooled enough to pitch the yeast. It will be interesting to see the difference in perceived bitterness between the two batches.

Just curiously Kelsey, you say that you use an oxygen tank with a ball to pump oxygen into the wort before pitching. In your experience, does this improve the environment for yeast to thrive compared to splashing it in from a height? The reason I ask is that my partner is an avid aquarist and I seem to have a shitload of those little pumps with the hose and balls that pump oxygen into fish tanks.

Cheers - Chris



5 Posted: Friday, October 13, 2017 2:37 PM

I have found it to improve fermentation performance yes. Beers taste a little cleaner, especially lagers.

I use an O2 cylinder that I got from BOC; attached to the hose on the regulator is a stainless steel ‘wand’ with a stone on the end of it. It's only turned on high enough to produce a small stream of tiny bubbles that slowly rise to the surface (maximum surface area etc.). If it's injected too quickly, the bubbles are too big, rise too quickly to the surface and the effect is nullified because the gas can't absorb into the wort very efficiently.

This is the tank I use (in that pic I hadn't received the wand yet), with a stone similar to the one underneath attached to the SS wand.





Last edited by Otto Von Blotto (Friday, October 13, 2017 2:37 PM)

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