mystery contamination issue!

[Amit]

Hi all,
I am brewing four different styles in a brewpub, surprisingly the pilsner and stout which I am fermenting using similar yeast haven't had any LAB contamination issue. Yet. However the wheat and ale styles get contaminated.
I first suspected the fermentation temperature, which being higher for ale and wheat tends to promote lactic acid growth, thus we fermented the new wheat batch at 12C, to my surprise there was no contamination till the third day. However today I picked up LAB contamination again!!!!!!!!!
Any ideas on what could be causing this? And how I can get rid of LAB contamination. I brewed this recipe elsewhere with the same WB 06 and the beers came out fantastic no sourness ever.

[brewmaster 2011]

My first question is why are you fermenting a wheat beer at 12C? You should be fermenting at 20C. Second how you sterilizing and sanitizing everything?

[Amit]

@Brewmaster - To avoid bacterial growth, I fermented it lower. I usually prefer 18 C. I also noticed that bottom fermenting styles which were fermented lower had no issue of contamination. Plus I read here by fermenting lower we can minimize the chances of unwanted growth.

@ Alex - Hello there, Thanks for the input, I have answered most of your questions below.

1. describe your cleaning SOP, what chemicals are you using, temp, water hardness, recirc time, flowrate? Hot water, Caustic 80 C - 2%, Hotwater, Nitric at R.T 2%, Hot water recirculation twice, water hardness - fluctuates in the range of 30 - 50 ppm, 20 mins of recirculation, flowrate not measured but we use a 2 HP - 3 phase pump and I know it provides sufficient pressure.

2. pitching method, dry or slurry, how many grams per hL are you dosing? what is the manufacturing date on the yeast packet, how has the yeast been stored.- I pitch Dry, depending on the yeast, anywhere between 50 -80 gm/hl, also depends on the temperature we ferment at, the packets were checked upon delivery for expiry (2014) and refrigerated 4 C,

3. aeration/fermentation details - what is the sugar profile of your wort, is it aerated, if so with O2 or Air, do you have filters inline to purify your aeration source - We haven't done any test for sugar profile, if required a HPLC analysis can be done but if that was the issue why are bottom fermented styles not being contaminated, I use O2 cylinders that are normally used for medical purpose, supplier does the sterilization, I din't have problems before using this method and no we don't have any way of doing inline purification system. I will be taking samples to detect the source .

4. what is the wort temp when you pitch? +/- 20 C

5. Do you CIP the PHE before knocking out? are you using 1 stage or 2 stage PHE? is your ambient water stage UV sterilized...are you including your hoses, sight glass, and other hardware in your KO line into your CIP cycles? Two stage PHE, I include all the lines used for delivering the wort in cip, we use hot caustic 2% to rinse it twice, first in the direction of the wort, then in the reverse order, this includes everything, PHE, sight glasses, o2 injection, yeast tank. UV has been commissioned for installation at the end of line but even prior to this lab reports have shown 0 cfu for water. I knockout hot water at 85 C to give a final rinse to the whole wort channel and flush the tank once before I finally transfer

6. Are you sure its an LAB issue? what are the off-flavours you are sensing? could it be something else...? like a meat-cellar flavour from your yeast. are you draining yeast from your unitank as it finishes fermentation and crashes? We confirmed it by doing a Lab test, the off flavour is usually the sourness, I drain the yeast by the third - fifth day after crashing it at 0 C. We haven't had the autolysis issue hence.

7. is the fermentation getting stuck? what is the OG and FG? any idea of the attenuation? No fermentation doesn't get stuck, sometimes takes longer to start but attains the attenuation. Depending on the yeast we use, some like S 04 have a higher attenuation upto 75%, OG is maintained at 13 P, and for lighter styles upto 11.5- 12 P. Final gravity for wheat is generally in the range of 1-2 P.

8. is sourness the only off-flavour or complaint with the beer? what type of sourness? are we talking vinegar? or is it astringency...? or un-refined bitterness...these can all be symptomatic of different issues. Yes sourness seems to be the only problem, Not a complaint because most people are liking it surprisingly, I would define it as tartness but some wheat beers do have a slight tartness but this one is a little overwhelming thou compared to previous brews.

About our equipment! we had to reweld the inside of FV's because the dome and conical weld joints had black holes as it was not finished properly, those that could have potentially become pockets for bacterial infection so I got them refilled, the inner tank has no mirror finish thus need to be scrubbed manually, The tanks have external level indicators and is a huge mess to clean. Hmm not to forget the metal pieces that had to be pulled out and rebuffed from the surface of sampling and dispensing areas o_O. Given all this, we take the tank apart before we begin CIP and scrub all the butterfly valves, DIN connecters and sampling taps and leave them in bucket containing nitric for couple of mins, sanitize the valves with 70% ethanol and cotton wool and places that I feel will not be effectively cleaned during CIP, including O2 sinters

I have seen experienced brewmasters who don't clean as much and had no contamination issue but in a different set up ofcourse. So maybe we have an undetected source perhaps which can be detected through methodologically taking and plating samples.

Cheers
Amit

[jfulton]

It sounds to me like your tank is full of places for bacteria to hide. Once they've gotten into a crevice and covered up with biofilm, you may never get rid of them in a poorly welded/designed tank.

[BlackLocustHops]

Is your infection only happening in the same FV's. You said that other beers were not getting infected, were they in the same FV?

[Amit]

Che' - Yes I brewed in the same tanks the same styles. But this time more vigorous cleaning was employed.
What are you suggesting?

[BlackLocustHops]

I was just trying to make sure that the contamination was not associated with every recipe fermented in the same tank. Sounds like something inline from HX to FV is not getting clean. Or the FV is contaminated as was already suggested. Try bringing the tank up to pasteurizing temp with water from your HLT, that should kill anything hanging around in the tank, just to rule that out. Here is a quick chart for time and temp.

63ºC (145ºF) 30 minutes Vat Pasteurization
72ºC (161ºF) 15 seconds High temperature short time Pasteurization (HTST)
89ºC (191ºF) 1.0 second Higher-Heat Shorter Time (HHST)
90ºC (194ºF) 0.5 seconds Higher-Heat Shorter Time (HHST)
94ºC (201ºF) 0.1 seconds Higher-Heat Shorter Time (HHST)
96ºC (204ºF) 0.05 seconds Higher-Heat Shorter Time (HHST)
100ºC (212ºF) 0.01 seconds Higher-Heat Shorter Time (HHST)
138ºC (280ºF) 2.0 seconds Ultra Pasteurization (UP)

[Aaron Taubman]

What is the OG, alcohol, and IBU's of the different beers you make? Its likely that the higher alcohol and IBU brands are inhibiting the growth of the bacteria and this is why you are only seeing it in wheat beers. Hops are very good at inhibiting bacterial growth!

Have you actually verified that the bugs are present in the fermenter? Perhaps you are picking them later on in bright beer tank or in the kegs? Don't assume anything!

[Bbump22]

Maybe try replacing every single gasket/valve on those 2 tanks and replacing the PRV.

[dick murton]

Have you checked for pinhole leaks in the FV cooling jackets or in the PHE? The wort pressure in the PHE should be higher than the coolant if at all possible as added security against pinhole leaks. Unfortunately of course, this can't be so easily achieved in the FVs. The difference may simply be due to the amount of time coolant is running through cooling jackets. Check the PHE first as your comment about lack of contamination when fermenting colder suggests to me the contamination is more likely to be introduced early on, and simply doesn't grow as fast due to cooler conditions.

Also, as suggested, check pump and joint seals, particularly on the suction side of the wort pump. You have got hygienic pumps haven't you? You aren't using general liquid (non hygienic pumps) are you? If (and I doubt if you have them) using water lubricated seals, then the seals must be checked, and the cooling / sealing water must be sterile (potable normally OK rather than absolutely sterile)

Cheers

[Amit]

Thanks everyone for your valued suggestions.

@jfulton @ Che - I was thinking of using a steam generator can that help me attain these temperatures also under pressure steam can disinfect and remove biofilms too. Injecting this during CIP can heat up the solution more easily. Is it a better, economical and wiser option to consider?

@Aaron - I am going to take swab samples of the tank and the PHE area after CIP and see if there anything still living in there!

@ Dick - Yes the pump is hygienic, its open impeller with gaskets and everything. The suction is from the Whirlpool end But when the wort comes in contact with the pump its still at 90+ C .. Are there still chances of contamination during transfer or only right after cooling?

I am quite doubtful too about my PHE, I guess keeping higher pressure in the PHE could prevent things from entering. The cooling water is collected back and used in general flushing and this water is potable considering we treat it with R.O.

How about I pressurize the tanks along with PHE line to .400 mPa with Steam? before I transfer. Isn't steam supposed to be a good sterilant?


Thanks
Amit.

[dick murton]

Contamination can occur5 in the PHE at any time once th etemperature is below about 35 C, or about 2/3 through the PHE. Are you cleaning the PHE at the correct speed - typically, the flow required is backward (which I know you said you were doing) at 130 to 150% of nominal forward flow rate for cooling wort. Caustic cycle time typically 20 minutes plus at this flow.

[MashHead]

Maybe try replacing every single gasket/valve on those 2 tanks and replacing the PRV.

+1

Small dents and cracks in gaskets are definitely a place for bacteria.

[OneMoreBrewer]

I wouldn't start replacing anything until you've sourced the contamination. We all need new equipment for something and I hate to see people buy things they don't need. Stainless can be cleaned. If anything I would do as Che (I believe) said and review cleaning procedures. Time, temp, concentration. Raise your caustic temp, or concentration, and extend the time of cycle. We actually use a cold caustic cycle (not ideal) but we run 30 mins at 3.5%. Also large swings in Ph will kill most anything that can live. Caustic, rinse well, strong acid, rinse well, sanitizer. A biofilm "can" be impossible to break down with chemicals only. You "can" prevent biofilm.

I would suggest agar plates. Swab every process point you can. Maybe, hot (sterile) wort in kettle (as control), before transfer pump, before chiller, before fermentor, also be sure to check your sample ports on the fermentor.
I have seen false concerns of bacteria when the sample port must have been contaminated post valve causing only the samples to show growth, but resulting beer from tap not. (This does not seem to be your case)

Was your FV work done correctly with a good purged weld and same grade stainless by a sanitary welder? This is my first suspect.

[Amit]

I wouldn't start replacing anything until you've sourced the contamination. We all need new equipment for something and I hate to see people buy things they don't need. Stainless can be cleaned. If anything I would do as Che (I believe) said and review cleaning procedures. Time, temp, concentration. Raise your caustic temp, or concentration, and extend the time of cycle. We actually use a cold caustic cycle (not ideal) but we run 30 mins at 3.5%. Also large swings in Ph will kill most anything that can live. Caustic, rinse well, strong acid, rinse well, sanitizer. A biofilm "can" be impossible to break down with chemicals only. You "can" prevent biofilm.

I would suggest agar plates. Swab every process point you can. Maybe, hot (sterile) wort in kettle (as control), before transfer pump, before chiller, before fermentor, also be sure to check your sample ports on the fermentor.
I have seen false concerns of bacteria when the sample port must have been contaminated post valve causing only the samples to show growth, but resulting beer from tap not. (This does not seem to be your case)

Was your FV work done correctly with a good purged weld and same grade stainless by a sanitary welder? This is my first suspect.

No FV was not welded correctly, it was quite easy to make out the poor welding job. The welds between the three sections of the FV had black dents, huge gaps and pockets which had to be filled by sending a welder inside. They used argon welding and ss 304 strips to fill this gap and finished it to make it smooth and continuous. They did a pretty good job. I know of a plant that was installed by the same consultants in the nearby city. They hired a German brewer who actually had the tanks cut open and rewelded, almost everything in the tank was rewelded!

The pressure gauge and PRV are installed in the side arm, these don't come in contact with the wort at all.

We dismantle the sampling ports, keep them in nitric acid solution and then clean it with R.O water and disinfect them with cotton saturated with 70% ethanol. But yes what do I do if I use the sampling ports everyday during fermentation to check gravity and pH mostly. how do I clean post that? I was thinking a way to temporary cap the end of sampling port and remove it before using.

I have used cold caustic before and yes they can be enough to clean tanks that are welded properly. I am brewing next week and will try to implement most of the techniques here and see if it helps me get rid of these bioflims.

Cheers