Tuesday, 8 September 2015

Overcoming beer spoilage contaminations

Mikko Pludra

In the last five months or so, my beers were persistently contaminated with a beer spoiling organism, which caused an off flavour that can be described as Band-Aid or medicinal. As a result of that, I poured out about 5 kegs of beer. The first beer that I discovered this off-flavour in was the single hop pale ale I brewed for the Xmas party. Although it hadn’t manifested itself at the time it was served, I noticed it in the keg a few weeks later, and the bottles which Barry filled for a later tasting were contaminated as well.
The technical term for this type of off-flavour is chlorophenolic. It can be caused by chlorine/chloramines in brewing water, using bleach for sanitising, or bacterial contamination (commonly known as “infection”).
When I discovered that my beers were spoiling, I had already brewed 4 more beers, and the latest one, a German Pilsner, was showing the chlorophenolic off flavour in the fermentor, at 9°C. Previously the beers were clean out of the fermentor, but as I tasted them, one after another went bad. Now I had to find out what was causing it.
I ruled out a chemical source for the contamination, as I had used filtered water or let the water stand overnight to eliminate any chlorine/chloramines in the source water. I also don’t use bleach in the brewery. That left a bacterial contamination as the only explanation, which also fit the picture of the beers getting gradually worse over time.
Where in the brewing process can bacteria have an impact on beer? Anywhere on the cold side of the process, i.e. after the wort is chilled. As a first measure, I replaced my plastic fermentors. No luck, the next beer went bad as well. Next, I looked at other equipment that the wort and beer came into contact with: oxygenation wand and plate chiller. My oxygenation rig is stainless steel, so in the oven it went – 2 hours at 180°C should kill anything, especially as there were no visible soils.

A new, clean plate chiller cut open (image from www.hardware-360.com)


Then I turned my attention to the plate chiller (a Blichmann Therminator, copper and stainless steel plates brazed together), which I suspected to be the main culprit. Plate chillers are notoriously hard to clean properly. In professional breweries, plate chillers are taken apart on a regular basis, and even though they are cleaned with hot caustic after every brew, there is still a significant amount of crud and organic soils left in the small crevices of the plates.
To clean the chiller, I ran a boiling solution of PBW cleaner through it in both directions. Afterwards, I gave it to Barry to autoclave in his pressure cooker. I then repeated the cleaning process with boiling PBW. After the first round a significant amount of dirt was dislodged, but after the second round the cleaner came out the same colour as it went in. It had now been about 3 months since I had brewed last, and my kegs were running low! It was time to pick up the mash paddle again.
Two weeks later, my Rye Pale Ale came out clean, tasting of beautiful fresh hops and luscious malt. No Band-Aid phenolic to be found! The spoilage organism was successfully eliminated. But how could it get a foothold in the first place? I was determined to not let it happen again.

Inside a freshly opened plate chiller after extended use (image from www.wortomatic.com)

My previous cleaning and sanitising regimen of the plate chiller was as follows: During the boil, heat up water to 70°C and recirculate through the chiller for 15 minutes. After the wort was chilled, I would run tap water through in a reverse direction, followed by warm PBW and Starsan as a final rinse.
I redesigned the whole process, based on the assumption that somewhere along the line, hop debris, break material and sugars were not getting rinsed out properly, and that pasteurisation temperature was not hot enough to kill all organisms during the recirculation. This is my new cleaning and sanitation process, which so far has been successful in keeping the bugs out:
1.     During the boil, run boiling water from the HLT through the chiller for about 20 minutes. This should be enough to kill any beer spoiling organisms, provided that the chiller is clean in the first place. I tie a hop sack around the return hose, so that any dislodged chunks of matter will not be sucked back into the chiller.
2.     After the wort has been chilled and transferred, I mix PBW into the hot water in my HLT (at a rate of 5g/l), and run it through the chiller in a reverse direction. The initial outflow is discarded, as it contains the bulk of the hop matter, trub and break material left in the chiller. Once it runs clear, I start recirculating for about 10 minutes, with the hop sack in place to filter out any chunks.
3.     The flow direction is then reversed, to run in the same direction as the wort during chilling.
4.     After a further 5-10 minutes, the flow is switched off and I use the PBW solution for cleaning my boil kettle and hoses etc. After everything is cleaned, I run tap water through the chiller, followed by a quick rinse with Starsan.
5.     Every 3 months I clean the brew house thoroughly: take valves and pumps apart, give the kettle a good scrub, and also immerse the chiller upright in a hot PBW solution for a few hours.
Cameron suggested that the chiller could be stored in a sodium metabisulfite solution, which inhibits bacterial growth while not corroding copper, even with extended contact time. As my chiller is currently mounted on the brew stand, I have not gone this extra step, but if my current cleaning regimen turns out to be inefficient, I will consider it.
This aspect of cleaning and sanitising is of course only a small part of the whole process of guarding yourself against beer spoilage. Anything the wort touches after it is cooled needs to be rigorously cleaned and sanitised with suitable chemical agents. I use the products that I mentioned previously, PBW and Starsan, which are available at most homebrew supply stores. PBW is a non-caustic alkaline cleaner that can safely be used on copper and will not melt your hands off, if you happen to get some on you. Starsan is an acid based sanitiser, and will kill any beer spoilage organisms with a contact time of only 1-2 minutes. The key aspect to remember is that neither of the agents can do the other’s job, so clean with a cleaner first and then sanitise with a sanitiser.

Hopefully, this account of my encounter with a persistent bug will inspire you to review your cleaning and sanitation process as well. It is easy to get complacent and take successful brewing for granted, but it takes only a small oversight to allow beer spoiling organisms to ruin the brewer’s hard work.

1 comment:

Braden Hammond said...

Great article, @mikkopludra

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