Pasteurizing kegs? Maybe SO2?

[LagerBear]

Hi everyone
I'm brewing a 10 bbl batch of beer for a client of mine (I am a contract brewer) and the recipe calls for backsweetening. I can handle bottle pasteurization in my brewery, but not sure how to tackle the kegs. (I don't have an inline pasteurization system). Any ideas of how can I pasteurize a SS keg? Is there another option for killing all yeast like adding Sulfites? I'm really worried about fermentation starting again in the packaged product after I back sweeten the batch.
Thanks in advance for any input!

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[jebzter]

First question, why back sweeten the beer? Proper mash profiles, etc should yield the correct sweetness.
Other ideas:
Why not back sweeten with something of low fermentablility. Lactose perhaps.
Many homebrewers use Sodium Metabisulfite to kill yeast.
If the beer is sulfited, you have to label it as such, and there are probably limits, I dont know what the rules are here it is not something that I would do.
Why not filter the beer?-Probably the best idea next to not backsweetening.

[LagerBear]

First question, why back sweeten the beer? Proper mash profiles, etc should yield the correct sweetness.
Other ideas:
Why not back sweeten with something of low fermentablility. Lactose perhaps.
Many homebrewers use Sodium Metabisulfite to kill yeast.
If the beer is sulfited, you have to label it as such, and there are probably limits, I dont know what the rules are here it is not something that I would do.
Why not filter the beer?-Probably the best idea next to not backsweetening.

Well because it's not really a beer it's a Ginger beer...
I do not have a filter in my brewery.
But Lactose is a good idea! Thanks!


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[jebzter]

I don't know if there is an equivalent forum for ciders, but that is something they definitely do. Most that I know of run their cider through a sterile filter before kegging, or they will pasturize the cider in cans.

[LagerBear]

Say I go with pasteurization, is it possible to pasteurize a keg?

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[jebzter]

It is possible to pasturize them, the seals and everything can take the heat. I think the bigger issue will be cooling them back down quickly. Cans can cool much faster, kegs have a much larger volume. You would also need a very large vessel to cook them in, or be forced to do it one at a time. I think if you dont want to filter, getting a flash pasteurizer might be the best way to do it. Probably more expensive than a filter.

[dick murton]

Sure, you can heat them up to pasteurisation temperatures, and cool them down again. But the effectiveness of pasteurisation is based on time and temperature, the number of bugs, and the thermal susceptibility of those bugs. Without circulation currents in the kegs, which will be minimal the beer towards the outside of the keg is going to have be way over pasteurisation temperature for far too long for the beer in the centre to be at pasteurisation temperature for sufficient time. And unless you have virtually sterile beer, effective pasteurisation will require silly amounts of PUs (heat and time). The excess heat will effectively destroy the flavour of the beer.

This is one reason why no-one bothers pasteurising large, say 1 litre + bottles of beer (apart from the weight / strength / and therefore cost of the heavy duty bottles). When I first stated in the industry, I used to bottle UK quart (2 UK pint) bottles, but these were not pasteurised, but the pints, half pints etc. were.

My view is don't even consider attempting it. I strongly recommend, though I realise you are reluctant to do so, simply to filter the beer, if necessary "sterile" filtering using 0.45 micron membrane filters afterwards. This will have less effect on the flavour, and be more reliable, and probably a damned sight cheaper in energy and time. Larger brewers use flash pasteurisers to give them far more reliable control of PUs and thus consistent kill, energy and time.

To put in sufficient metabisulphite, or other biocide such as used in many fruit juices to kill the bugs, will also affect the flavour - and then you run into labelling / purity / ethical problems with your customers as well.