Ask The Brewmasters

This message was posted by a user wishing to remain anonymous

We recently had plates sampled from one of our brite tanks show substantial growth on UBA and LMDA plates (showing substantial acid production by the CFUs).  We immediately scrapped plans to package this beer. Subsequently our Lab Manager re-plated and again saw rampant growth on LMDA both aerobically and anaerobically.  Isolated CFUs were stained and diastase test performed.  Under the microscope the bacteria appeared to be rod-shaped and gram-positive leading us to believe that it was Lactobacillus.  Additionally, we inoculated HLP media with samples from this brite tank and they returned with substantial colonies of comet-like CFUs…also indicating Lactobacillus.  We then sent samples to our yeast supplier to run PCR and they confirmed the presence of hop tolerant Lactobacillus.  We have plans to destroy this beer (despite evidence now showing that the infection is isolated to the sample valve…but more on that later).  So, I'd like to run through my plans to safely remediate this infection and get your feedback.  ALL other tanks in the cellar have come back clean and free of contamination, with repeated platings on LMDA and HLP. 

My plan is to use 1/2" tubing run to our drain to slowly drain the tank so as not to tax our wastewater.  Once drained we will acid wash, then fully de-gas, fully evacuate the tank of CO2, then run a caustic cycle.  All gaskets will be replaced.  Post CIP we will confirm cleaning with an ATP swab.  Once passed, the tank will then get filled with water which will be pushed out of the tank to fully purge the vessel and rid it of most of the oxygen.  The tank will then be sanitized under pressure using PAA to the appropriate strength.   

Does this course of action seem sufficient?  Overkill?  Just right?  Suggestions on a better course of action?  We have been fortunate to have never encountered this issue before and hopefully won't ever again.  

Getting back to the sample valve…it is a Perlick-style valve with rubber cup seal, rather than the old school swivel style zwickel.  A subsequent plating on LMDA and HLP of a sample taken from the bottom of the tank showed zero growth.  Absolutely clean.  Obviously this points to bacterial build up in the sample valve gasket AND/Or introduction of hop tolerant lactobacillus THROUGH the sample valve, most likely from an over-pressurized and contaminated Zahm.  So, the follow up question here is… is there anyone out there sanitizing their Zahm prior to use?  How are you doing so?  Other than a few gaskets on the interior of the Zahm, would their be any reason we couldn't or shouldn't pack the Zahm in iodine-based sanitizer or PAA?  Is there a "best practices" article regarding Zahm cleaning, maintenance, use, and sanitation?

Hi Anon,

When you say "appropriate strength" of PAA, what ppm level does that mean?  It might be a good idea to go a little stronger than normal to be on the safe side.  I would suggest using 300-500 ppm active peracetic acid.  It is still in the post-rinse sanitizer range but will be more effective if the organism is used to seeing PAA in the 100-200 ppm range.

Hope this helps, please keep us in the loop.

Dana

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Dana Johnson
Technical Director, Craft Brewing
Birko - A Diversey Company
Henderson CO
(303) 289-1090, ext. 117
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Hello-

I have seen examples of diastaticus coming from a contaminated CBOX into a BBT. We worked with the manufacturer to develop a cleaning and sanitation protocol to prevent it from happening in the future. It's important to use chemicals that are compatible with the instrument you are cleaning. I would wager the Zahm is much more resilient to chemicals compared to the CBOX. 



Here's a video of cleaning from Zahm. Good luck! 

https://www.youtube.com/watch?v=dFFOH7gpv4U  

WB

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Wade Begrow
Microbiology and Food Safety Manager
Founders Brewing Company
Grand Rapids MI
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Dear Fellow Brewer
I'm sorry to read of this situation.
Although not uncommon it is none the less scary. Most of us have been there but we don't like to talk about it.
It often happens in the fall after a long, hot summer. Especially in certain beer styles with low hopping, unfiltered, low ABV, low attenuation, or higher pH etc. Weiss Bier, Amber Fest Beer etc
Your plan is certainly not "overkill"
It is the only rational course of action.
You are right to suspect the sample valve. These should be strip cleaned every time the tank is emptied for CIP. We autoclave these valves after every use as Zwickels are a real weak point. But also look for the ultimate source. Check the instruments that you attached to this sample port. For example, Z-N CO2 Tester or other CO2/DO instrument. They can get really dirty. You actually need to develop a CIP program for your instruments! This is especially true in the fall after a hot and humid summer when such events are very common. Other weak points are the various rubber good on tank fittings - for example, at level transmitters, butterfly valves. PRV's etc. Bourdon style (non-sanitary!!) pressure gauges with NPT ends are notoriously bad (use should really outlaw them in your brewery)!! Check the tank itself for presence of beer stone that indicates incomplete CIP and/or insufficient brewing water treatment. UV Lamps as are found at Dairy Equipment supply houses are helpful for spotting low levels of stone. Beer/Milk stone fluoresce in such light. Lastly, bring along some test tubes of saline with sterile swabs so you can swab all suspect surfaces as you find them. Plate these on relevant media. This helps you identify the ultimate source and a great way to learn how to avoid a repeat next fall! Keep the offending bug in your library so you know if it shows up again. L. brevis, for example.
Good Luck,

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Daniel Carey
Brewmaster
New Glarus Brewing Company
New Glarus WI
(608) 527-5850
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It's a little pricey up front, but we found it extremely helpful to invest in enough butterfly valves that each side-port on our tanks get a butterfly. That way the sample valve doesn't have to live attached to the tank. We had a few leaking perlicks over the years that pushed us to this solution, now it's extremely useful because our lab guy autoclaves all the sample valves he uses to pull samples for plates and PCR, one less spot for "false" positives.

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Colin Vent
Brewmaster
Seventh Son Brewing Co
Columbus OH
(614) 596-0913
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With the exception of replacing all the gaskets, your cleaning program sounds like what you should do every time you empty the tank.  As others have noted, it is important to break down all the little parts on the tank and give them a detailed cleaning.  I have worked at facilities where we sterilized the sample ports and considered them useful for just one aseptic sample collection.  Currently, we use bonnet-style Perlik valves with the following sample procedure:

1. Flush about a liter of the tank's contents quickly through the sample valve.
2. Clean the spout completely with 70% iso-propyl alcohol and Q-tips.
3. Burn off the alcohol and heat-sterilize the valve with about 10 seconds action with propane torch.
4. Wait about 20 seconds for the heat to sink in and kill microbes.
5. Cool the valve by running about 1/2 pint through it.  Be careful to avoid contamination by back-splash.
6. Quickly collect sample to sterile jar, using good aseptic practice.

Dumping the whole batch might be a little over-kill, especially if you think it was a false positive from a soiled sample valve.  More testing might help inform your cost vs. risk assessment.

I think you bring up a very good point about the dirty Z&N tester.  Those things get really gross on the inside, and they have the potential to contaminate your bright tank.  We have a sample valve installed on the process piping of our centrifuge, and have recently started cleaning our CO2 testers on a regular basis by flushing them through during CIP.   Maybe you can work a clean/sani of your Z & N into one of your routine CIP procedures?  Just be sure not to exceed the maximum temperature of the Z & N, especially if it is the old-style with the glass thermometer.

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Cullen Dwyer
QA Manager
Wachusett Brewing Co
Westminster MA
(978) 874-9965x160
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Original Message:
Sent: 10-12-2022 12:59
From: Colin Vent
Subject: Best practices for CIP following infection in a tank

It's a little pricey up front, but we found it extremely helpful to invest in enough butterfly valves that each side-port on our tanks get a butterfly. That way the sample valve doesn't have to live attached to the tank. We had a few leaking perlicks over the years that pushed us to this solution, now it's extremely useful because our lab guy autoclaves all the sample valves he uses to pull samples for plates and PCR, one less spot for "false" positives.

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Colin Vent
Brewmaster
Seventh Son Brewing Co
Columbus OH
(614) 596-0913
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