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jszydlow
12-10-2014, 10:22 AM
Does anyone have a general rule of thumb for how long a sanitized, pressurized keg stays sanitary? I am using caustic cleaning and a lactic-acid / oxine mix for my sani (the cycle runs each keg through these steps twice), then a C02 purge. Unfortunately, we are forced to store clean kegs outside, so they are subject to temperature fluctuations (they are wrapped and kept under cover though). Any input would be greatly appreciated!

gitchegumee
12-10-2014, 02:51 PM
Answers here:
http://discussions.probrewer.com/showthread.php?40622-How-long-will-sanitized-vessel-stay-sanitized
Hope this helps.

jszydlow
12-11-2014, 08:41 AM
Answers here:
http://discussions.probrewer.com/showthread.php?40622-How-long-will-sanitized-vessel-stay-sanitized
Hope this helps.

I did see that post but the answers seemed to apply to non-closed systems (e.g. fermentation tanks) vs. kegs, which are immediately purged and pressurized after sanitization and will not be exposed (internally) to potential contaminants until filling. Additionally, the only information in that thread about the half-life of sanitizer was for Star San, which works differently and therefore (I'd assume) breaks down differently than a hydroxypropanoic acid (lactic) mixed with chlorine dioxide (oxine).

panadero
12-11-2014, 12:05 PM
"Opinion based on experience/research"

I am in agreement with Phillip for the most part. The thread quoted does cover a lot, I think in the end you have to draw what you will from a conversation, and infer a bit more. My takeaway from it all is that your fermentors, brites, kettles, etc all have so many openings for the bugs to hide - I can see nine openings on my fermentor - that even though I sanitize after cleaning, I also sanitize just before use. My kegs, however have one entrance, and once washed, sanitized, and purged of oxygen with CO2, I spray sani on the head, and put on a clean sanitized cap, and send it to the cooler. I again spray sani on the head before filling, and haven't had a problem. I run a 10 bbl system, and keg off the serving tanks when they are down to two or three barrels, or whenever the next beer is ready to be transferred to a server. I know that peroxiacetic sani breaks down quickly, but with the CO2 purge, I feel I am covered.
In short, I have a rule of thumb, but is only as long as my thumb! I have filled kegs stored this way two months down, but usually fill them within a few weeks. There have been maybe five kegs in three years with off flavors, and I attributed those to the hoff stevens converted kegs with loose stems, and old orings. Once I replaced the orings I never had a problem again. The other caveat here is that my kegs are used in house, and once filled are gone within another month or two. So, no warm transport in a random distributors pickup truck, and no sitting unrefrigerated in a warehouse for any period of time.
The few guys I know who are up at the bigger distribution levels are using minikings, or something, to clean, sanitize, and fill in one go, getting rid of the issue. For what it is worth I have a keg washer setup based on the diy model you will find in these forums. A floor pump with a bunch of fittings, and a guy standing there - me - opening and closing valves, and counting out the time, erring on the long side to ensure cleanliness.

Hope this helps - not really an answer, but a description of my methods, and some sort of reason for them.
David

jszydlow
12-11-2014, 12:43 PM
"Opinion based on experience/research"

I am in agreement with Phillip for the most part. The thread quoted does cover a lot, I think in the end you have to draw what you will from a conversation, and infer a bit more. My takeaway from it all is that your fermentors, brites, kettles, etc all have so many openings for the bugs to hide - I can see nine openings on my fermentor - that even though I sanitize after cleaning, I also sanitize just before use. My kegs, however have one entrance, and once washed, sanitized, and purged of oxygen with CO2, I spray sani on the head, and put on a clean sanitized cap, and send it to the cooler. I again spray sani on the head before filling, and haven't had a problem. I run a 10 bbl system, and keg off the serving tanks when they are down to two or three barrels, or whenever the next beer is ready to be transferred to a server. I know that peroxiacetic sani breaks down quickly, but with the CO2 purge, I feel I am covered.
In short, I have a rule of thumb, but is only as long as my thumb! I have filled kegs stored this way two months down, but usually fill them within a few weeks. There have been maybe five kegs in three years with off flavors, and I attributed those to the hoff stevens converted kegs with loose stems, and old orings. Once I replaced the orings I never had a problem again. The other caveat here is that my kegs are used in house, and once filled are gone within another month or two. So, no warm transport in a random distributors pickup truck, and no sitting unrefrigerated in a warehouse for any period of time.
The few guys I know who are up at the bigger distribution levels are using minikings, or something, to clean, sanitize, and fill in one go, getting rid of the issue. For what it is worth I have a keg washer setup based on the diy model you will find in these forums. A floor pump with a bunch of fittings, and a guy standing there - me - opening and closing valves, and counting out the time, erring on the long side to ensure cleanliness.

Hope this helps - not really an answer, but a description of my methods, and some sort of reason for them.
David

David,

Thank you for your detailed account. I feel a bit better now about letting my kegs sit around for a bit. Unfortunately, our cooler space is insufficient to store empty kegs (we have 800 or so right now!). We sani the bungs after washing and of course before kegging, and they stay capped in that interim, so I am not too concerned with threats from the outside.

Obviously, in an ideal world, I would keg the same day I cleaned my kegs, but when we are dealing with turning over 80 bbl each day, their is no way I can accomplish that with a single-tap keg washer. Also, labor is another factor: on intensive packaging days, we can't have a dedicated keg washing person. This is, of course, problematic since that is precisely when we would want to be washing kegs. So, given these obstacles, I have to wash kegs for many days, sometimes weeks in advance. It is evident that our capacity is definitely outpacing our ability to clean and store kegs but it's a bit above my pay grade to make decisions about equipment upgrades... Thus why I am testing the waters to see how much I can get away with.

Brandjes
12-11-2014, 02:35 PM
I'm going to set aside a couple cleaned and purged kegs and have one of my local chemical guy test it in a few weeks. I'll post results

jszydlow
12-12-2014, 08:53 AM
I'm going to set aside a couple cleaned and purged kegs and have one of my local chemical guy test it in a few weeks. I'll post results

Eric,

You're the man!

Bainbridge
12-12-2014, 11:14 AM
Experimental Research instead of Internet Conjecture?!? Madness! I gotta get over to Enumclaw sometime.

soia1138
12-12-2014, 03:41 PM
In order for a test to give you any information of value I think you would need a much larger sample size than a couple of kegs. We have both cleaned, sanitized and purged well ahead of time and on the day of kegging, as well as at the same time as. No issues either way. All the kegs done ahead of time, sometimes days in advance, get a sanitized keg cap and a spray of sani just prior to the fill. As with most things in this business it seems all dependent on the situation. Kegs being stored outside in fluctuating temperatures I would be a little cautious with personally. Metal expands and contracts as well as pressures rise and fall possibly creating vacuum and together conditions favorable to nasties entering what seemed like a sealed environment. You do what you can with what you have and keep a close eye, if problems arise then it's time to change your process to correct it.

Brandjes
12-17-2014, 11:27 AM
I have set aside 2 1/6bbl kegs that have been in service about 1 year to do the testing on. Not a great sample size but better than nothing. The kegs were cleaned following the process below and were pulled from the middle of the run. A run is 6 1/2bbl and 6 1/6bbl. I recirculate the solutions by setting the keg on a bucket and using a "pond" pump to spray up into the keg.
I will let them sit for a couple of weeks and then test one. If it's negative for contamination I'll let the other go for a few more weeks. I will highlight the testing process with the results.
Keg Cleaning Process
1. Remove Spear ( submerge spear in cleaning solution while all kegs are washed).
2. Hot water rinse (130*F) for 45 seconds
3. Recirculate cleaning solution (130*F) for 90 seconds
a. Cleaning solution – Nitric/Phosphoric Acid (12%/4%) 1oz/gallon plus non-foaming detergent 1tsp/gallon
4. Hot water rinse (130*F) for 45 seconds
5. Leave keg top down to drain for approximately 30 minutes
6. Recirculate sanitizer for 90 seconds (PAA @ 150pmm)
7. Leave keg top down to drain for approximately 30 minutes
8. Rinse spear (130*F) inside and out (open valve using decommissioned tap)
9. Submerge spear in sanitizer (minimum 2 min)
10. Re-install spear
11. Fill Keg to 13psi with CO2 (not filtered)
12. Allow keg to sit for 30 minutes
13. Slowly purge CO2 down to 1-2PSI
14. Refill keg to 13psi with CO2
15. Spray fitting with sanitizer and cap

Brandjes
02-05-2015, 12:32 PM
Testing performed by Jeff Wagner of CH2O. Jeff was a founding member of 5 Star and has over 30 years of food and beverage plant cleaning and sanitation experience.
This testing was only on 2 kegs so it is anecdotal, but it might spur someone to do further testing
The test we ran was an ATP test using the Hygiena EnSure ATP meter and UltraSnap swabs. This test gives a measure of all contaminates and does not isolate bacteria, mold etc. from inert proteins and “dirt”. The unit presents a reading of Reflective Light Units (RLUs). A general pass/fail range is 0-10RLU = clean, 11-30 is marginal (monitor for future failure) and 31+ is fail. Some facilities will set boundaries that are much higher than this. As a point of reference – an unwashed keg will give a reading in the thousands to tens of thousands.
I washed two kegs on 12/17/2014. Keg 1 tested 24 RLU after wash. Keg 2 tested 0.
On 1/18/2015 Keg 1 tested 64 RLU. This could be from bacterial growth or the swabbing hit an area that was dirtier than the first swabbing. We would have to plate it to know and I wasn't planning on going that in depth.
On 1/27/2015 Keg 2 tested 0 then retested to get a 7. This keg stayed “clean” for almost 6 weeks.
Take from this what you want.

claponsie
02-05-2015, 01:20 PM
Awesome information. What kind of environment did you store the kegs in? Can you approximate what temperature the kegs were during the 6 weeks of storage?

BullzEye
02-05-2015, 02:28 PM
I don't mean to sound like an ass, but I think you asked the wrong question. If you sanitize a keg and keep it under pressure, why would it become unsanitary? Consider for example sterilization, in which everything is killed, including spores. To assume anything would survive or enter into a sterilized and pressurized environment assumes the existence of spontaneous generation, or at the very least that external pressure exceeds internal pressure!

Now, brewers don't typically sterilize, they sanitize. But if you have a keg or a tank and you performed your sanitation step effectively, why would you do it again? You can't sanitize something twice. For example, I don't understand why so many brewers like to run a PAA step twice on fermentors, once after cleaning and again before filling. PAA isnt effective at removing organic solids, so what is the purpose of using it twice, other than to waste chemicals, energy, and time? I run a caustic CIP, strip all my parts off the tank and soak in caustic then Iodophor. After returning the parts to my tank I run a passivation cycle with a nitric/phosphoric blend, rinse well and then seal the tank with 3 psi of pressure. I use PAA before I brew. I do this on my brites everytime as well, and I brew lagers and sour beers in the same brewery without issues.

Sanitation should not be a problem when storing your kegs for an excessive period after sanitizing. I think you should be more concerned with flavor tainting. Some residual water remains in your kegs after cleaning and sanitizing. Ideally your water is pure, but even reverse osmosis water will eventually result in a minor calcium carbonate scale inside your kegs. I don't know how long it will take to develop a significant enough scale to affect beer flavor. I would remove the spear of one of your kegs after a few months and take a look inside. If there is no issue maybe wait another month and check a different keg. If you see or smell anything foul, you need to look at your cleaning and sanitizing regimen.

claponsie
02-05-2015, 02:44 PM
I always wondered if there would be any significant bacterial growth in a keg after sanitization, because like you said, there are residual bacteria. Because we are not sterilizing, a small precentage of bacteria remains in the keg. I shared the same curiousity the OP had about the subject. It would have been more interesting to have a statistical-driven analysis of many kegs over a period of time and at different temperatures, but the OPs experiment is still useful. After we clean and sanitize our kegs, we have the luxury of storing them cold. We only fill 2-3 kegs at a time and everything is manual, so sanitizing immediately prior to use is pretty labor-intensive. It's much easier to sanitize as part of the cleaning cycle for us, since we already have the spears removed. Eventually, we will have a keg washer, but for now, we have not had any (known) contamination issues with our method of cleaning/sanitizing kegs and storing them in the cooler.

Brandjes
02-05-2015, 03:18 PM
Stored the kegs inside at the brewery at 64'.
There was a lot of conjecture to the OPs post so I decided to try and actually test the idea that a clean and sanitized keg should stay sanitized over time. More a sanity check than an experiment. I hope someone with the resources will take this idea and do an actual test

jszydlow
02-17-2015, 09:08 AM
Stored the kegs inside at the brewery at 64'.
There was a lot of conjecture to the OPs post so I decided to try and actually test the idea that a clean and sanitized keg should stay sanitized over time. More a sanity check than an experiment. I hope someone with the resources will take this idea and do an actual test

Eric,

Thank you for the sanity test. I am working with our newly hired QA/QC guy to design an experiment like the one you staged (but with more kegs, so we can get some statistical significance). If we get this off the ground I will definitely post results.

I appreciate everyone so far for weighing in. What I've summed up from the conversation is that best practice is to sanitize as soon as possible before filling (obviously) but perhaps there is a degree of paranoia with regards to what is "sanitary" and how long something can or can't remain so (especially under pressure). I think there is a tendency to strive for sterilization when, as a previous poster pointed out, that is not really the end goal in most CIP processes. There will always be foreign contaminants in the process, but it's a question of whether or not they are measurable and, most importantly, if they are of a magnitude that will affect the quality of the product. I thank you for including your explanation of the ATP levels and standards for what is considered sanitary - I believe this is exactly the kind of approach you need when considering that we are measuring the cleanliness of a sanitary environment (e.g. acceptable target range) vs a sterile environment (e.g. pass/fail for contamination).