Braukaiser.com – Blog

I just learned that it is always a good idea to check the correction factor that applies to your refractometer. A commonly accepted correction factor for converting a refractometer’s Brix reading to a hydrometer Plato reading is 1.04. I was always under the impression that the Brix reading has to be multiplied with this value, which works for me, but Sean Terril pointed out to me that the commonly accepted formula divides the Brix value by this correction factor to covert to a Plato reading. (Refractometer Calculator)

Since my approach was working for me I had to check what’s going on here. I thus tested water, a 20 Plato sugar solution and a 20 Plato wort with both the hydrometer and my refractometer. All solutions and the refractometer had the same temperature.

hydrometer in water	This is the hydrometer in water. I have a table that I use to correct the hydrometer reading in Plato for temperature and the slight offset that the hydrometer has
water on refractometer	water measured with the refractometer
hydrometer in 20.4 Plato sugar water	The sugar water (~40g table sugar, 160g water) read after correction 20.4 Plato
hydrometer in 20.4 Plato wort	The wort read after correction 20.4 Plato as well
20.4 Plato sugar water on refractometer	In the refractometer the sugar water read 19.4 Brix. Since refractometers are calibrated for sugar water, it should have read 20.4 Brix
20.4 Plato wort on refractometer	In the refractometer the wort reads 19.5-19.6 Brix (remember that water read slightly under the zero-line). To get the hydrometer reading I have to multiply this reading with 1.04

The reason why my correction factor is different is that the scale on my refractometer is off. I.e. there is already a conversion factor for sugar water that is not 1. But since I checked my refractometer against my hydrometer at various wort gravities and found that Plato is Brix * 1.04 I can still use this refractometer in brewing.

BTW, the ATC of this refractometer is also broken. For every brewing session I have to re-calibrate it with water. Since this is done very quickly, it doesn’t bother me too much.

Conclusion:

If you buy cheap gear, check its calibration.

This may sound crazy, but I commonly hold the “Diacetyl rest” at 22 C (72 F) for my lagers. When reading through some German brewing papers I notices that some of them referred to a fermentation schedule where the lager was fermented at 8 C (46 F) for about a week and after that the beer temperature was raised to 22 C for 1-2 days before the beer was crash cooled to near freezing for cold conditioning.

In my brewing it takes a bit longer than a week for the beer to be done with primary fermentation. It also doesn’t reach final gravity as fast as it was shown in those papers. To make maters worse, fermenting the last few fermentable sugars until the attenuation is close enough to the attenuation limit always tends to take longer than I want it to.

To speed things up I started holding the “Diacetyl rest” rest around 20 C. I intentionally put diacetyl rest in quotes since for most of us the primary benefit of this rest is not diacetyl reduction but speeding up yeast’s consumption of those last fermentable sugars.I prefer to call this rest a maturation rest and may hold it for up to a week, if the beer is still too far away from its attenuation target. (If you don’t know how to determine final extract or gravity target of the beer, check out the Fast Ferment Test.)

Warm fermentation and lagers doesn’t seem to go together, but don’t worry. Low fermentation temperatures are only needed during primary fermentation when the yeast is actively growing and its metabolism shows activity along many different pathways that can leak excessive esters and higher alcohols if the temperature is too high. Once the yeast is done growing and all nitrogen sources have been assimilated, the fermentation temperature can be raised without the risk of creating the flavor compounds that are generally associated with high temperature fermentations.

keg with heating pad and temperature sensor

I do these maturation rests in kegs for a number of reasons. First, I can easily heat them with a heating pad controlled by a temperature controller. Second, I can use this fermentation to carbonate the beer. Lastly, the yeast will consume all the oxygen that is introduced during racking.

The image above shows how the heating pad (you’ll need one that doesn’t have an automatic shut-off) is attached to the bottom of the keg. At the top of the keg I attach the temperature sensor, covered with a piece of foam.

When the beer is racked to the keg, I make sure plenty of yeast is transferred as well. The kegs have a shortened dip tube, which allows for transferring the beer and leaving behind the yeast sediment later.

Finally the whole thing is wrapped in a blanket for further insulation:

Keg wrapped in a blanket

A pressure gauge is attached to monitor the pressure build-up and allow controlled CO2 release.

I finally ran a brewing experiment again and am dusting off this blog to post the results.

The experiment was a repeat of a standard experiment that evaluates yeast growth in still, intermittently shaken and stirred starters. I like how easy it is to set up and plan to repeat it again.

Setup

919g of 12 Plato wort were aerated to 100% air saturation on a stir plate. Then 7.8 g WLP 830 yeast sediment from a primary fermentation was added and allowed to un-flocculate completely. The cell density was determined as 22.3 Million/ml with a hemacytometer. If you do the math you find that the slurry contained a total of about 20 Billion cells which means its density was 2.63 Billion/g. Previous slurry density assessments for slurries from yeast propagation ranged from 4-5 Billion/g for this yeast. I assume that trub played a big role in the reduced cell count in this slurry.

Once the yeast was evenly distributed in the wort, the wort was evenly divided into 3 500 ml Erlenmeyer flasks. The flasks were labeled with their empty weight and covered tightly with aluminum foil. I didn’t tighten the cover intentionally. I noticed that this happens when I grab the flasks at their neck to shake them. I made sure that all of them had tightened aluminum foil caps, even though only one would be shaken intermittently.

All starters were allowed to complete fermentation. One sat still, one was shaken intermittently (1-2 times in the morning and 3-5 times in the evening) the last one was placed on a stir plate and stirred continuously. A vortex formed on the stir plate, but was eventually covered with foam when CO2 started escaping. The ambient temperature was around 18 C.

Data:

Once fermentation was complete the yeast was allowed to settle into a dense cake until the beer on top cleared. The beer was poured off and the flask’s weight with yeast and stir bar (in one of the flasks) was determined. From that, the empty weight and the stir bar weight the yeast weight was determined:

I only recorded the yeast weight and did not count the yeast with the microscope. Simply, because I did not want to spend too much time on this. To estimate the number of cells grown I assumed that the sediment had a density of 4.7 Billion/g, an average of the numbers I had assessed in earlier experiments.

Discussion and Conclusion:

The wort volumes for the three starters were not exactly the same, hence the difference in the extract weight.

I was surprised to see that the sill and shaken starters showed no difference in the amount of yeast that was gown from the available extract. This is different from the data reported by others (e.g. the great Maltose Falcon article on yeast propagation: Yeast Propagation and Maintenance: Principles and Practices) where a shaken starter grew significantly more than a still starter and a stirred starter outperformed a shaken starter by about 4x. The caption to the chart mentions that the data point for the still starter was taken from a different experiment, though.

Data I recorded on past yeast propagation steps (usually stirred)  and fast ferment tests (usually shaken) show more difference in extract utilization for yeast growth, but there are also a number of other parameters that have been different for those experiments. Most notably the starting gravity and the initial cell density.

I’ll have to repeat this experiment in the future to see what covering loosely with aluminum foil does and what an airlock would do to the extract utilization that can be achieved. And maybe I also find the time to count the final number of cells.

I finally found the time to fix the images on the wiki. Most of them I was able to get back from a back-up. The rest I simply had to upload again from my disk at home. Let me know if you notice anything else broken.

A few days ago I received a note that my site was hacked and used for a phishing scheme. I asked the support staff to remove the files, but apparently that did some damage to the images for the Wiki. I’ll look into fixing this. The site has been backed up, so I should not have a problem restoring the lost images.

Kai

Getting back into brewing seems to be plagued with all sorts of obstacles. This time I ran out of propane before getting the wort to a boil. And yes, it was at night again and I was far from being in the mood for a midnight propane run.

But this time I got the wort up to 98 C, which is hot enough to pasteurize it and I decided to go a different route – the no chill approach. While the wort was still hot I covered it with aluminum foil:

The wort sat this way over night on the deck and I moved it into the house in the morning. After 24 hrs the temperature dropped to 32C. During that time the pH fell from 5.27 to 5.14. I’m not sure if this is sign of an infection, but it smelled just fine. So I brought it to a boil. A lot of coagulation already happened in the hot wort and an oddly brown layer of trub developed during heating:

Other than that the boil seems to be going as normal.

Last night I was finally able to brew again. I was done mashing and lautering the Weissbier wort when I pulled out my turkey fryer burner just to find out that it stopped working. Despite a full propane cylinder no propane would come out of the regulator and after tinkering with it for a while an deciding that this is not the kind of stuff I feel comfortable fixing myself I had to look for other options.

I was also 9:30. Not enough time to rush and buy a new burner and I was also not in the mood of starting a wood fire and boil the wort that way. So I decided to cool the wort down and put it into my fermentation chest where it will be sitting at ~0-4 C until I can resume brewing it, which will most likely be tomorrow.

Could there be something stronger than the IPA (or KaIPA for this matter) itself?

Yes, the beer that can be squeezed from the spent dry hops. Something only a true brewing geek knows to enjoy. Besides being murky like the Ganges in the rainy season, the aroma is pronounced but not overpowering. The bitterness, however is much harsher than the actual beer. It particularily lingers in the back of the throat, which I don’t appreciate too much.

Prost

Some of you may have wondered what happened to braukaiser.com between April 1st and April 6th. Well, I forgot to check the e-mail account associated with that domain and let my domain name expire. After the initial shock, which included the fear that I lost my rights to that name, I realized that it was simply a matter of paying the renewal fee and getting braukaiser.com to point to my hosting account again.

Everything should be running just fine again and I can also receive e-mails from my braukaiser.com account. This certainly taught me a lesson about staying on top of these administrative tasks.

Last weekend I brewed my annual Maerzen using 75% Best Malz Vienna, 20% Weyermann Munich II and 5% CaraFoam. When designing the brewing water I went by my past experiences with a similar grain bills that used Weyermann Vienna and the surprise came when I tested the mash pH. Instead of the expected 5.5o I got 5.77. I’m generally not off by that much and was doubting the pH meter until I also tested the mash pH with colorpHast strips. During the decoction the pH fell to 5.71 and I added another 2 ml 88% lactic acid to bring it down to 5.58, which I considered ok for a Maerzen. The boil pH was later reduced as well with some lactic acid.

After testing the distilled water pH of this Vienna malt I found that is was way off from the pH one would expect from a base malt slightly darker than pilsner malt. It was 5.8. Below is a chart of the distilled water mash pH for various base malt samples that is taken from my mash pH paper:

The pH is slightly higher than pale or pilsner malts and more than 0.2 pH higher than the Weyermann Vienna that I tested a while back. This goes to show that the color/pH correlation is even weaker than I thought and that one should not rely on the accuracy of color based mash pH estimations for grists that contain a mix of base malts. The color based mash pH prediction works much better for grists made of pale/pilsner base malt and a mix of specialty malts since the pH properties of the latter are more predictable.

More predictable was the amount of lactic acid that I had to add to lower the pH. With 0.32 ml per kg and 0.1 pH drop it was well within the 0.25-0.42 ml range that I show here.

The malt analysis sheet for this batch of malt reported a pH of 5.9 for the congress mash. While I noticed this I assumed that the pH of the congress mash, which is diluted to 8 l/kg towards the end, would not be that useful for predicting mash pH. In hindsight this could have been an indication for the higher than expected mash pH.