Ask The Brewmasters

Hello fellow brewers,

Portable meters that are used throughout a brewery can be notorious 'bug traps' (ie., home for bacteria and yeast).  They are prone to nasty biofilms.

Proper cleaning of these meters tends to be a 'fool's errand' since meters usually cannot tolerate high pressures, high temperatures, nor aggressive chemicals.  Also, the cleaning path through a meter is a torturous path riddled with fittings, obstacles, and chambers that inhibit or mitigate turbulent cleaning flow.

We have a few Haffmans Gehaltemeters (c-DGM).  Nice units that are incredibly valuable to our daily operations.  We were cautioned by Haffmans not to be too aggressive on the unit when cleaning and that daily rinses should suffice.  We all know this ain't enough to keep brewing equipment clean!  We can prove this by collecting rinse water on the meter outlet and plating for microbiology... guaranteed to have nightmarish results.

I feel the risk for contaminating a tank or beer line by attaching a dirty meter is a real threat.  Even with good procedures for hooking up meters (eg., making sure you have positive flow path on the meter outlet before you open a zwickel) the threat of cross-contamination is real.  We like to say "Bacteria like to swim upstream"...  That is, positive flow and positive pressure is not a guarantee against bacteria working in the opposite direction.

Meters are typically hooked up to multiple locations such as fermenters, packaging tanks, various beer lines, and de-aerated water sources.  If a meter is contaminated, 'spreading the disease' is going to happen.  Just like the common cold spreading throughout a community of people.

Question to instrument manufacturers and brewers:  Do you have any clever ways to ensure hygienic standards on your portable meters?

Challenge to instrument manufacturers:  Design a truly HYGIENIC portable meter;  one that can easily & effectively be cleaned daily.

Cheers,

Randy Thiel

New Glarus Brewing Company

Randy,

Has your lab traced a contamination event back to a meter specifically?

We've got an Anton Paar Cbox QC, a Pentair c-DGM, and a Pentair Oxy-2-Go at our facility.  Usual cleaning route is to use some potassium hydroxide based non-caustic alkaline cleaners (Cell-R-Master for us) in warm (< 40C) RO water.  The c-DGM and Oxy-2-Go manuals (Section 8.2.1, Special cleaning) both state that so long as you are below 2% concentration and 60C you can use NaOH to clean your meter.  Anton Paar are slightly more restrictive, stating "glassware cleaner (pH <10)".  They also state that you should clean with said chemical daily after use (Section 13.2 of the Cbox manual).  I use a KOH based cleaner on our Cbox and Alcolyzer and consistently get comments from the AP technicians about how clean the internals of our equipment are during the annual Preventative Maintenance visits.  We are currently doing chemical cleaning cycles monthly-ish on our meters which is sufficient for our needs.  If the thought of KOH is a bit much, Tergazyme works wonderfully as an alternative.  While I've used Alconox I found it less effective than the other cleaners mentioned above.  Sounds like whomever you talked to at Haffmans hadn't thoroughly read their own literature.

Regarding the bacterial threat from meters, if you have sufficient product pressure (even simple hydrostatic pressure is often enough; pressurized headspace is ideal) and are opening and closing your flow paths appropriately during sampling, there is virtually no chance of cross-contamination from a meter.  While I have had multiple incidents stem from fouled sampling valves I have never traced a contamination source back to a meter.  This is why we keep sanitary butterfly valves behind every single sample port in our facility.  Expensive?  Yes.  As expensive a single turn of contaminated product?  Not even close.

I will also say as a trained microbiologist I have never heard from any reputable source that bacteria "like to swim upstream"; rather they "go with the flow".  Even motile bacteria, which are rare in brewing, can't "swim upstream" counter to any sort of flow.  Positive pressure and flow are as close to foolproof as you're going to get for sampling in a brewing setting short of moving to true sterile sampling (massive overkill, massive $$$$$).

Sounds to me like the cheapest, fastest, most effective fix would be to update your SOPs to include routine chemical cleaning of your meters per manufacturer instructions.  Perhaps some retraining as far as appropriate aseptic sampling techniques could be beneficial as well as we can all use refreshers from time to time.