Hazed and confused

Ken writes:


I started writing this post a year ago when I was about six months into a new job. We had  dreadful problems filtering beer for sale and very slow lauter times. I didn’t get round to finishing the post then, but we turned the problems around so I thought it might be helpful to anyone in a similar predicament to hear what we did.

The description of the problem.

The problem was basically two fold: It took forever to filter beer to remove chill haze, and it took forever to lauter the wort. Chill haze is a mild form of turbidity that forms when different compounds are precipitated out of the beer by cold temperatures and adhere together forming tiny particles. We had to filter one or two beers we brewed on contract and our own lager. A three thousand litre batch would take all day to filter despite the fact that the filter was rated for 3000 litres per hour. Some of the time was just setting the filter up and cleaning it down at the beginning and end of the work, but the time in the middle was dire. “lautering” is the process of separating the husks and other undissolved matter from the sweet wort after mashing. When it came to lautering, if we got the wort out in 3 to 3.5 hours we were slapping each other on the back and giving each other high fives. We were staggering our  starts because it took about 10.5 hours for a single brew. Everyone was exhausted.


Kettle and lauter tun


Lauter times

They say problems in the tank farm usually have their origin in problems in the brewhouse so I’ll talk about that first.

Although we had a really top notch 30hl Kaspar-Schulz brewhouse, we were running it on a manual basis because the automation program hadn’t been installed. The brewery was purchased second hand and the original automation program couldn’t be installed when the brewery was put it in. The local electricians weren’t up to the job and many of the wires connecting the sensors to the plc were connected wrong. The plant was capable of excellent lauter performance, but we weren’t using it correctly. We subsequently got our lauter run off time down to less than 90 minutes, so that shows what it was capable of.

Inside the lauter tun


We did a number of things to try to improve lauter performance. We opened up the mill settings to produce a coarser crush in the hope that this would provide a better filter bed. We tightened the mill settings to produce a finer crush (because opening the mill hadn’t helped—maybe unmodified gelatinised starch adhering to the husk was settling at the bottom of the tun and forming a layer of impermeable gunk).

We seemed to run the first worts off too quickly so we started slowing that right down. We would run off only with gravity and then throttle the flow in addition to that. But still it didn’t really help. We would eventually have to underlet and smash up the grainbed with the rakes and then recirculate for ages, which would compact the bed again, or let cloudy wort through to the kettle.

The bed was always pretty dense and settled like a slab on the base of the lauter tun. It seemed like every mash was a stuck mash.

The beginning of the solution was changing how we operated the mashtun/kettle. The kettle had paddles in the bottom to prevent the mash burning on to the base of the kettle during heating up between the various rests. We used the paddles at full speed when we mashed in to ensure there were no dough balls and to obtain and even heat throughout and full-speed while we were heating, but we continued to paddle at half-speed during the rests/stands. When we stopped doing this, the mash remained more buoyant when we transferred it to the lauter tun. It still settled on the base of the tun, but it had a certain buoyancy that had been missing.

The next change was in raking behaviour. We had played around loads with the rakes adjusting the height at which they operate and their speed but couldn’t settle on the right regime. Eventually we hit on it. We completely ignored the height adjustment and left the rakes at the bottom of the tun. The reason for this was that plenty of lauter tuns are actually designed with rakes set at a fixed height, so the height at which they operate couldn’t be very significant. The speed adjustment was important. We set the speed to one revolution every two minutes. This wasn’t enough by itself. The break-through was stopping the run off during raking. Running off during raking must pull fine particles lower and lower into the bed. Raking by itself served to loosen the bed without sending the fine particles to the base of the tun.

Once we discovered this, and obviously it would have been built into the original automation programme, we could speed up running off the first worts. We would run the first worts off in 25 minutes or so, add some sparge water and then rake to loosen the bed again, and begin running off after the raking had restored the pressure difference across the bed, as measured by two sightglass tubes, to near equality. I’m convinced here that the critical development was not running off while we were raking.

It all seems so simple now, but it took us a long time to identify the decisive measures while we were struggling because there were so many possible things that could have played a part. Different malt bills were certainly relevant, with the lighter beers being easier to manage than the darker ones. There seemed to be recipes that were particularly bad and we experimented with using malts from different manufacturers and even changing the recipe completely (leaving only the final colour the same). It took such a long time to get feedback regarding any change. Raking in the wrong way can do lots of damage to the lauter performance, but you don’t discover this until the damage is already done.

Chill Haze filtration

There can be a number of reasons why you may have trouble filtering beer. We had a filter skid set up with a 3 micron, 1 micron and 0.5micron sequence of ever tighter filter cartridges to yield a virtually sterile product. The tighter cartridges could be bypassed if we only wanted to filter out yeast. The 3.0 micron was only nominally rated, meaning that some particles smaller than 3.0microns could pass the filter (just not very many). The 1.0 micron and 0.5 micron cartridges were absolute ratings (nothing smaller than the rated size should be able to pass through).

We occasionally had problems with the 3.0 micron filter but generally did not. If we fined the beer and moved it into a dish-bottomed conditioning tank before filtering, then we had no problems. Filtering straight out of a CCV caused problems when a large plug of yeast would dislodge itself and get sucked into the filter housing and then block the filter cartridge immediately.

The 1.0 filter was there to protect the 0.5 micron filter. It did its job very well and we hardly ever had to change the 0.5 micron cartridges. The 1.0 micron filter always blocked. We wondered if it was yeast passing the 3.0 micron filter so we put 2.0 micron cartridges in before the 1.0 micron to see if that would make a difference, but it didn’t help. So the haze creating particles were smaller than 2 microns but bigger than 1.

They say problems in the tank farm are almost always traceable back to problems in the brewhouse and it sort of was that way for us too. We noticed that certain recipes never gave us any trouble filtering so we looked what they had in common and they all involved a low-mashing in temperature and a protein rest. As a result of this, we introduced a number of steps to reduce the amount of protein in the finished beer. We mashed in at 45˚C (to allow some beta-glucanase activity) and then heated through to the saccharification temperature at 62˚C, and then a starch rest at 72˚C, and then mash out temperature of 78˚C. This didn’t involve a protein rest as such, but gave the proteases scope to work. (We were mindful that we did not want to degrade the proteins responsible for beer foam too much as the boss had a very strong preference for good foam on beer). We also brought the mash pH more under control. The best lauter performance seemed to be at around pH 5.4. The feeling was that if the lautering goes easily that will be better for filtering as well because the wort will already be cleaner. We boiled for 15 minutes prior to adding hops to get lots of foaming in the kettle. We slightly increased the amount of kettle finings we used and we changed the way we transferred the kettle contents to the whirlpool to avoid breaking up large protein flocs. Finally, we started using a colloidal silica solution in the conditioning tank when the beer was cold. of these measures, I believe the protein rest/low mash in temperature made the biggest difference.

There were a couple of cul de sacs. Adding Brewtan B, a solution of tannic acid, to the mash or to the boil did not seem to help much. It could be however that it had a positive effect but for some unrelated reason this was cancelled out by something else. You have to remember that we were still producing beer at a very hectic pace throughout this time and there was a gap between brewdays and filtering days and so day-to-day demands on our attention meant it wasn’t always easy to relate what we were seeing in one part of the brewery to what had happened a couple of weeks ago somewhere else. We had loads of problems with our tank farm cooling so we always seemed to be lurching from one problem to another. That got sorted in the end. Buíochas le Dia.


Happy Ending

It’s incredibly satisfying when you feel you have solved a problem in the brewery. It’s such a complex operation and so interconnected that you can never really take an off-the-shelf solution from what you’ve read or found elsewhere. I was lucky to have a number of really quite eminent brewing scientist friends who could be called on to help me understand the problems but no one was able to just walk in and diagnose and treat the problem straight-away. You have to know the brewery equipment fairly intimately. Even purely physical things like vessel dimensions and materials, agitator speeds, pump types, pipework, heating capacity can make a difference, to say nothing of the chemistry of the different processes. But it all serves to make you feel even better when you do finally get it right.




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