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Master Brewers Association of the Americas > BREWING RESOURCES > Ask the Brewmaster
October 16
Ideal CIP Practices?
Q: I have some questions regarding CIP practices. I have heard the ideal CIP protocol is Caustic then Acid followed by a no rinse Acid Sanitizer.

Why is this ideal? Why not Acid followed by Caustic then Sanitizer? What are the considerations for this particular regimen? What are the benefits vs risks of doing it differently?

I really want to know why this regimen is preferred over others and why others would be harmful or less than ideal. I will likely have follow up questions. Thank you for your time,

A: You didn't specify what you are cleaning, so I will assume the application is for a CCT used for fermentation. Typically, caustic is used first to remove organic soil. The tank should be rinsed and inspected following the caustic cycle. If the soil wasn't fully removed, additional spot cleaning or another caustic CIP is necessary.

Next, acid (typically a phos/nitric blend) is used to remove beer stone. Some plants run acid during every tank CIP, others do it at regular intervals instead. The reason this is done after the caustic cycle is because it is difficult to remove beer stone if it is covered up by the organic soil. 

Then, of course, a sanitizer (often PAA) is used as a final SIP step on a fully cleaned and rinsed tank.

There are plenty of other CIP protocols for other applications and circumstancs. There is a CIP procedure similar to what you described known as "caustic override" in which acid is followed by caustic. The acid is drained but not rinsed. This procedure is primarly used when dealing with baked-on protein soils (like what you may find in a brewhouse) and would not make sense in a fermentation vessel. The acid is used to denature protein and the reaction between caustic and acid creates available oxygen (scrubbing bubbles). Another strategy for that type of soil is to add peroxide to caustic.

Here are just a few of the great MBAA resources relevant to your question:

October 15
Standard Acceptable Loss?

​Q: I am researching Standard Acceptable Loss Percentages for the Brewing and Packaging processes. I am looking to obtain information that will help to compare our losses to a set standard. I am looking for a breakdown of the percentages for each of the following steps: Boil – Whirlpool; Whirlpool – Fermenter; Fermenter – Filter; Filter – Brite; Brite – Pasteurizer; Pasteurizer – Buffer; Buffer – Filler; Filler – Finished Product.

I know that there are different factors that may vary these percentages such as the gravity of the beer; the different type of product or recipe; the accuracy of the measuring equipment; loss from purging of product from the pipes and “spare’ beer that is kept in the tanks for sediment. Could you also include any additional factors that may contribute to our loss.

Any information that you could provide me or if you could refer me to additional information would be a great help.

A: The increasing diversity in the types of beers produced and the methods for producing them makes this question impossible to answer. Any "standard" is outdated and likely only applies to lager/light-lager production. I recommend focusing on improving your own losses at each stage rather than attempting to benchmark to another brewer's process, which is likely not the same as yours.

Here are some MBAA resources that may help you on your quest to benchmark/reduce process loss:

August 18
Calibrating DO meters

Q: ​How important is the BBT ppb readings on the D.O. sensors? I have been using 99.999% nitrogen which was given to me by Hamilton to zero the sensors. When I look at the specs of the gas, it says that it can have < than 2ppm o2. I am not sure that is good enough if we are trying to zero and read ppb? Even the 99.9999% can still have .5ppm O2? I have a hard time understanding the correlation of O2 in nitrogen (ppm) and O2 in beer (ppb). Is there a calculation I can use to prove this out? Also the “0” calibration and the span “210000ppm 0r 21% O2”  seems like a huge span to then try and read accurately in the ppb range. If I could find it, I would love to get a “standard” D.O in solution of 25ppb to verify calibration.

A: Extremely important - decreasing DO in the BBT is absolutely necessary to produce the best possible beer. Most DO meters for this application are accurate to about +/-1 ppb.

For both gas phase and liquid phase (DO), the O2 content can be expressed in the unit ppm (which is very confusing). However, the unit for gas is ppm vol/vol and the unit for liquid (DO) ppm m/m, so these are completely different units. As rule of the thumb, the conversion of ppm vol/vol and ppm m/m is 20,000:1

Taking your specification of the class 5.0 nitrogen with a purity of 99.999% which still can have < 2ppm O2. These are 2 ppm vol/vol and equals 2/20,000 is 0,0001 ppm m/m = 0,1 ppb m/m DO. This gas is perfectly suited for performing a zero point calibration/verification. There are procedures for creating "liquid zero" standards, but this is less accurate than using the gas standard that you already have.

It may be challenging to create or purchase a 25ppb liquid standard. An option could be requesting a certified (or even better) accredited gas mixture of N2 with an O2 content of 50 ppm vol/vol which equals approx. 25ppb m/m DO (check its availability). During the O2 verification it's important that the gas and O2 meter have a very similar temperature and the gas flow is low, so you do not have pressure build up in the O2 meter.

If you want a more practical, lo-tech opton, many breweries keep an aged beer standard of known DO in house to use as a quick, rough calibration check.

Many thanks to Frank Verkoelen and Jeff Tocio (Pentair Haffmans), as well as Kevin Sudderth (Hach) for their invaluable contributions to this response.

August 10
Removing Fine DE

​Q: Brewmaster,

My Operations Manager has decided to remove the fine Kieselguhr from our filtration pre-coat and body feeds and replace it with coarse Kieselguhr as a cost saving measure. Prior to this decision we were using approximately a 2:1 ratio of coarse kieselguhr to fine in the pre-coats and body feeds. Is there a significant difference in effectiveness of filtration of fine vs coarse kieselguhr? Could removing of the fine kieselguhr cause filtration problems? Additional info: We use a frame type filter press. We currently do two pre-coats consisting of  a mixture of coarse and fine kieselguhr. and 4 body feeds for approximately 100 hl of beer

A: In regards to the effectiveness of your filtration, eliminating the fine DE will result in a coarser filtration. Yes, this may be a significant difference. Look at your spent cake and compare it to what came out of the beer previously during the finer filtrations. Whether allowing more particles to pass through your filter into the finished beer is acceptable can only be determined by the load of your unfiltered beer (what and how much of it needs to come out) and your product specifications (desired level of clarity/acceptable haze, colloidal stability, shelf life, etc.) for that given brand. There's no one-size-fits-all answer since there are so many different types of beer on the market and strategies for producing them.

Could removal of the fine DE cause filtration problems? To answer this question I reached out to MBAA member Tom Thilert, who has many years of experience in filtration. Here's a summary of what Tom mentioned:

Since you are using a plate and frame filter, you most likely have (non-active) filter sheets between the frames. Non-active filter sheets contain no DE (they are mostly made of cellulose) and only serve the purpose of supporting the cake. Removing the fine DE might cause blinding of the filter sheet if there are a lot of fines to remove. Otherwise, this should be no problem.

If after removing the fine DE, the sheets don't plug, you have no issue with releasing the cake from the sheets, and the filtered beer meets your product specifications, then there is no problem with removing the fine DE. With no fine DE, you can get away with a single precoat and use the same DE for the entire run. 

Please note: If you are using active sheets for an extra polish filtration, then it is very likely these will plug without the fine DE.

July 28
Batch Carbonation

​Q: Dear Brewmaster, 

I work at a brewery on a Caribbean Island, we are having problems with dialing in our CO2 levels in the bright beer tanks. We usually end up with about 100-95HL in our bright beer tank. Coming out of our fermenter our beers usually have 3.5-4.5 grams per liter of CO2. We filter one day then package the next (about a 12-16 hours between end of filtration and beginning of packaging). We generally leave our beers under 1-2 bars of pressure depending on the volume in the tank and time until packaging. On the day of packaging, if our CO2 levels are low we pump more CO2 in from the bottom of the tank. If we are high, we have to release all the pressure from the tank and purge CO2 out of the beer then re-pressurize the tank. (This is very costly for us, and a waste of CO2).

Are there any formulas we can be using that factor in Time, Temp., volume and initial CO2 levels to help us hit our carbonation range in bright beer tank?

Thank you for your insight!

A: Typically, these questions are answered electronically; however, due to your location I think we should consider a site visit to fully assess your situation. 

It sounds like your filtered beer has fairly typical CO2 levels (~1.8-2.3 volumes) compared to what I've seen in the average US microbrewery. You didn't mention your target CO2 spec for packaging, but it's got to be at least a bit higher than the upper end of the range you gave for your filtered beer. Unless your carbonation stone is undersized (or soiled) or cooling is inadequate, hitting your packaging spec in 12-16 hours, without wasting CO2 during the process should be no problem.

First, it's critical to understand that the volume of CO2 dissolved in your beer at any given moment is always equibilrating toward a theoretical value determined by the conditions (temperature and pressure) at that moment. For example, if you were able to maintain 12psi of CO2 head pressure and 35F in your BBT, you'd eventually end up with the 2.73 volumes listed on the charts that come with CO2 volume meters. This would be true regardless of the starting carbonation value; however, it might take days or even weeks to reach 2.73 volumes, depending on your starting value. Since none of us have that kind of time, we use carbonation stones and attempt to optimize temperature and pressure to hit carbonation specs faster. Take note from the chart that, given enough time, beer left under 1-2 bar at cold temperatures will become substantially over-carbonated.

As soon as filtration is complete, record all of the usual suspects: volumes of CO2, beer temp, bbl/hl of beer, tank head pressure, DO, and verify cooling is on the BBT. I'll assume your BBT head pressure at the end of filtration is ~1 bar. If it's low, plug the current temperature and CO2 volumes into your chart to solve for pressure. You'll want to immediately top up head pressure to at least this value to prevent degassing (ie if you have 36F beer and 2.20 volumes CO2, get the head pressure to at least ~7psi). If you will be intentionally venting the tank (to scrub DO) at the beginning of carbonation, be sure head pressure never falls below this point.

To get flow through a carbonation stone, you'll need to set the regulator pressure higher than your desired equilibrium pressure on the chart because you have to overcome hydrostatic pressure (depends on the height of the column of beer in your BBT) and capilary pressure of your porous carbonation stone (depends on the stone, but usually ~5psi). Avoid the temptation to just set the pressure high and let it rip. CO2 injection must be slow to create small bubbles that are readily dissolved. If you go fast, many of the large bubbles created won't dissolve. This results in foaming (which damages foam positive proteins), unnecessary scrubbing (loss of hop aroma/desired volatiles), and a huge waste of CO2. There are 2 common approaches to limiting CO2 flow at higher regulator pressure settings: either step up regulator pressure in small increments over several hours or install a needle valve of some kind (better). Some brewers also use an adjustable PRV on the blow off arm of the BBT so they can set it to blow off at a desired equilibrium pressure. This helps to prevent both over-carbonation (by limiting the max head pressure) and degassing (by limiting venting/the min head pressure). Blow off valves simply left cracked open for venting can cause the head pressure to fall too low - which results in degassing instead of carbonation. Our friends at the Brewers Association put together a very good lecture about carbonation a while back - you might want to check that out for some additional information.
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