Hot Cube, in a keg?

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Karl Cotter

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As I filled my 15 lt plastic hot cube container recently, I wondered how much plastic was being infused into the beer. With the temp of the wort, around 98° some plastic must be coming off the container?
It got me thinking. I brew in a grain father which is stainless, ferment in a stainless steel fermenter & put it in a stainless steel keg, to avoid plastic where I can. But hot cube in a plastic container. So my question to the group, has anyone hot kegged? I not talking about fermenting in a keg, just hot cubbing. fill the keg with hot wort, then invert it, as you would with a plastic container, then stand it to let cool over a period, then pour it into a fermenter, as you would the normal way.
Any anyone done it?
 

Nullnvoid

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How are you going to remove all the oxygen out of the keg?

When I cube you either fill it to the brim and/or squeeze the living F out of it to get all the air out.
 

Dozer71

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You would likely need a reverse spunding valve or something to relieve the negative pressure (open PRV) as the wort cools, or you will buckle the kegs if sealed tightly. Both these methods will let oxygen in though, unless you hook it up to CO2 in some fashion. Have you seen the shapes of the cubes from addition of hot wort (slightly convex or bloated) and the next day when they are cold - slightly concave.
 

MHB

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I know a few people who have tried usually got infected. Point is that kegs are designed to hold pressure, not vacuum, they will leak air in through the Hatch O-Ring, the poppets in the posts and the PRV, with air come bugs and there goes your beer.
Even fitting a HEPA filter to a gas disconnect was at best partly successful, keeping overpressure from a CO2 bottle only worked most of the time.
I think there are just so many small nooks and crannies in the keg posts and other fittings that it would take a full pulldown and reassemble to get the hygiene standards necessary.
Its even possible that even once its cooled and taken off the CO2 expansion and contraction just from the temperature changes between night and day would be enough to let in a little air - it only takes 1 bug...

There are plastics and there are plastics, most cubes are made of food grade Polyethylene, the plasticiser they use is mostly Citric Acid.
I wouldn't be in the least concerned about putting hot wort in a food grade cube, I would take the time and perhaps even pay a little extra to make sure they were in fact food grade.
With good quality cubes the answer to your question is probably none.
Mark
 

Karl Cotter

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How are you going to remove all the oxygen out of the keg?

When I cube you either fill it to the brim and/or squeeze the living F out of it to get all the air out.
Thanks for the reply. I used to squeeze the bj's out of the cube as well, to try to get all the air out and got boiling wort over my hands. Then I noticed in the brew shops the amount of air space in the commercially made cubes. So I tried just filling an inch or so from the top, screwed the lid on as hard as I could and turned it upside down, between 2 bricks and just left it there to cool.. I've hot cubed dozens of times like this and never lost one. So it seems just turning the cube upside down and getting that wort all over must pasteurises the whole container. It must work, as one brew, for what ever reason I only 13 litres of wort and I put that into a cube, inverted it and it was fine.
Food for thought I suppose. Thanks for your thoughts.
 

Grmblz

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^ +1 I tried it using an aspirator, a device designed to exclude air by supplying CO2 to real ale casks without carbonating the beer. At a guess I'd say 1 in 5 was noticeably infected, the others probably were to a lesser extent, and that was for cooling only, couple of days max not cubing and coming back next week.
 

Karl Cotter

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^ +1 I tried it using an aspirator, a device designed to exclude air by supplying CO2 to real ale casks without carbonating the beer. At a guess I'd say 1 in 5 was noticeably infected, the others probably were to a lesser extent, and that was for cooling only, couple of days max not cubing and coming back next week.
Actually, that makes sense. As it cooled, it would suck air in via the ring pull valve on the lid wouldn't it. As they're designed to stop co2 etc leaking out. You've just saved me a wasted brew. Thank you.
 

Karl Cotter

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I know a few people who have tried usually got infected. Point is that kegs are designed to hold pressure, not vacuum, they will leak air in through the Hatch O-Ring, the poppets in the posts and the PRV, with air come bugs and there goes your beer.
Even fitting a HEPA filter to a gas disconnect was at best partly successful, keeping overpressure from a CO2 bottle only worked most of the time.
I think there are just so many small nooks and crannies in the keg posts and other fittings that it would take a full pulldown and reassemble to get the hygiene standards necessary.
Its even possible that even once its cooled and taken off the CO2 expansion and contraction just from the temperature changes between night and day would be enough to let in a little air - it only takes 1 bug...

There are plastics and there are plastics, most cubes are made of food grade Polyethylene, the plasticiser they use is mostly Citric Acid.
I wouldn't be in the least concerned about putting hot wort in a food grade cube, I would take the time and perhaps even pay a little extra to make sure they were in fact food grade.
With good quality cubes the answer to your question is probably none.
Mark
Yes, I agree with you, it all makes sense kegs are made to hold in pressure. Also, regarding the plastic thing, I'm probably worrying about nothing in the overall scheme of things. Thanks for your thoughts. It's appreciated.
 

Karl Cotter

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You would likely need a reverse spunding valve or something to relieve the negative pressure (open PRV) as the wort cools, or you will buckle the kegs if sealed tightly. Both these methods will let oxygen in though, unless you hook it up to CO2 in some fashion. Have you seen the shapes of the cubes from addition of hot wort (slightly convex or bloated) and the next day when they are cold - slightly concave.
Dozer71. You are right, they are concave when they're finally cooled. That's why they just use a plastic container, simple and works. Thanks for the response.
 
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I've done it quite a few times without issue.
I do a full breakdown on my kegs at least once every 2nd or 3rd clean. And pressure cook everything that'll fit, excluding the PRV (the cheaper ones will melt).
I brim fill hot, and then put 3 bar of top pressure, and top up for the first few hours while it cools.
I also pitch it the next morning, or as soon as it's below 40ºC.
I also make sure it gets a healthy yeast pitch, so there is minimal lag.
I typically use kveik, so I know my yeast will out compete anything else that might have got in.
I probably wouldn't do it if I was making a lager though.
 

damunch

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I used to do this a lot but with a 50l. I'd boil a little water in it, with a jar/cup over the top to steam sterilise it and dump the hot wort in. I capped it with a tri-clover clamp, cap and a silicon seal when hot and dumped that in trub to cool it with a hose running at a trickle from the bottom. I could keep it for as long as I wanted like that. The only issue was getting the cap off without cutting the seal as it was really clamped down. It's a not a game you can play with a stuffed shoulder+knee though as handling 60kg+ when hot is pretty challenging. I'd also brew in them. Cleaning out was done with a high pressure hose with a plumbers pipe cleaner that I made up.
 

Karl Cotter

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I've done it quite a few times without issue.
I do a full breakdown on my kegs at least once every 2nd or 3rd clean. And pressure cook everything that'll fit, excluding the PRV (the cheaper ones will melt).
I brim fill hot, and then put 3 bar of top pressure, and top up for the first few hours while it cools.
I also pitch it the next morning, or as soon as it's below 40ºC.
I also make sure it gets a healthy yeast pitch, so there is minimal lag.
I typically use kveik, so I know my yeast will out compete anything else that might have got in.
I probably wouldn't do it if I was making a lager though.
Sounds a bit of business to do, but at least you got it to work, so I suppose it can be done to a real lesser extent than the traditional way. The thing is, if I hot cube, I may leave it for a couple of months and or I might have a few cubes sitting in the garage. So it's traditional way I suppose I will continue to do it.
Thanks for your response.
 

Karl Cotter

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I used to do this a lot but with a 50l. I'd boil a little water in it, with a jar/cup over the top to steam sterilise it and dump the hot wort in. I capped it with a tri-clover clamp, cap and a silicon seal when hot and dumped that in trub to cool it with a hose running at a trickle from the bottom. I could keep it for as long as I wanted like that. The only issue was getting the cap off without cutting the seal as it was really clamped down. It's a not a game you can play with a stuffed shoulder+knee though as handling 60kg+ when hot is pretty challenging. I'd also brew in them. Cleaning out was done with a high pressure hose with a plumbers pipe cleaner that I made up.
You're not wrong, wow, a guy could get hurt if you didn't have a friend to help you there, My son & I used to brew 80 ltrs every fortnight or so and there's no way a you could do that much beer on your own, having said that, some of the pulley systems that I've seen on this site are very impressive. Looks like I'm staying with the traditional hot cubing method I suppose Damunch. Thanks for your response.
 

YAPN

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Looks like I'm staying with the traditional hot cubing method
Just a question there Karl, do you fill the plastic cube straight after the boil, at 100C, or bring it down 80C first?
 

Karl Cotter

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Yapn, I tried both ways, 1. Left GrainFather chugging away boiling as I pumped it into the cube & turned it off at half full mark.
2. Turned off the boil for a couple of minutes, did a whirlpool then pumped it into the cube. The second way I feel is quite ok. But the amount of trog left in the GrainFather is negligible, so the whirlpool might be a bit of a wasted effort????
 

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