Filtering homebrew

I recycled the yeast from a previous fermentation without proper consideration to the amount of yeast required to ferment the new batch. As a result the final beer had so much yeast in it you just about had to chew it. Honestly, it was undrinkable; and I don’t mind a bit of yeast in a craft beer.

Filter with corny keg line-out disconnect

Filter with corny keg line-out disconnect

I bought the housing off eBay for $30AUD inc. postage, and some 12.5mm PVC tubing from the local hardware store (food safe at cold temperature) and fitted the tubing to a cornelius keg disconnect using a stainless steel hose clamp. The 12.5mm tubing went over the top of the standard 6-8mm tubing connect area after soaking the tubing in hot water. The connectors between the tubing and filter are standard garden irrigation system threaded connectors to 13mm barbs. These should also be fine regarding food safety at the filtering temperature.

The idea for sanitising was that the lid, tubes and disconnect could all be sanitised as one item after removing the poppet from the disconnect with a screwdriver.

Source keg (LEFT) and destination keg (RIGHT) with filter (MIDDLE)

Source keg (LEFT) and destination keg (RIGHT) with filter (MIDDLE)

I filtered at roughly 100kPa and it took about 5-10min to filter the entire keg.

Destination keg overflowing from froth

Destination keg overflowing from froth

The batch had been stored in the fridge prior to filtering and since I had originally naturally carbonated the keg with 70g of dextrose it was not properly flat. You do not want to filter a fully carbonated keg. For all intents and purposes the beer was flat, but it still frothed a lot. I believe a major factor was that the cold beer holds dissolved CO2 more readily – it would have been preferable to keep the keg to be filtered at room temperature and use the release valve daily for a few days to make sure all dissolved CO2 had been removed from the liquid.

Filtering complete, this was the final state of the overlfowing destination keg

Filtering complete, this was the final state of the overlfowing destination keg

You can see from the patch of liquid on the ground that it didn’t really overflow that much. It was a simple job to fit the lid through the froth, then rinse the keg under an outdoor tap before putting it into the refrigerator.

Here is the uncarbonated (but cold) filtered beer

Here is the uncarbonated (but cold) filtered beer

The final finished beer was not exactly clear (although there is condensation on this glass from the cold liquid, so it is hard to tell) however it was a whole lot clearer than the original. I will probably look at 0.5 micron rather than a 1 micron filter in the future. The filter that I used said that it captures 85% of 1 micron sized particles. My research found that yeast was typically 3-5 microns across, so most if not all yeast should be removed and I am satisfied that the remaining cloudiness is probably just some heavier proteins.

The 1 micron filter immediately after filtering

The 1 micron filter immediately after filtering

The filter actually looked really clean after filtering. I couldn’t see any visible chunks on it. It was rinsed thoroughly and then re-assembled into the filter tank with water and no-rinse sanitiser and the disconnect and attached tube was removed while the filter-out tube was filled with water and wrapped around back onto the filter-in 13mm barb to make a loop so that the filter and tube was filled with sanitised solution. It will be stored this way until next use and properly sanitised again immediately before use. One advantage of the 1 micron filter is that water passes through very easily so it is simple to sanitise.

The waste poured out of the filter housing immediately after filtering

The waste poured out of the filter housing immediately after filtering

The liquid that came out of the centre of the filter (the waste) was quite thick but didn’t really differ in resemblence to the original unfiltered beer (yep, it was that bad!). Still, I wouldn’t drink this!

About Pinky

Computers, programming, new music and all things science, tech and sport
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