My Brewing Log

Ever wondered what would happen if you let a yeast culture on agar grow? The result is called giant yeast colonies which in the past have been used to distinguish yeast strain. Differences in metabolism, flocculation characteristics and genetic stability lead to differences in the appearance of the giant colonies.

So I wanted to give it a try myself. Brewing Techniques featured an article on that topic which pointed out that the growth medium needs to be much thicker than the thin agar medium that is commonly used for Petri dishes. Not having deep mycological Petri dishes I used 4 oz canning jars. The growth medium was regular strength brewing wort solidified with agar. The BT article suggests using gelatin but that didn’t work for me, likely because I forgot about the advice not to autoclave the gelatin.

The agar surface was inoculated with very small amount WLP 002 (English Ale) yeast and allowed to grow for a few weeks at about 15-20 C (60-68 F). The result is shown below.

Apparent are “growth rings” which are considered typical for highly flocculent yeast. Another interesting feature is the wedge shaped change in yeast appearance (green arrow). This is likely caused by a mutation that happened to a cell at the tip of the wedge which caused it and the cells originating from it to grow differently than the other cells in the colony.

While growing giant yeast cells has little application in practical brewing it is one of those fun things that can be done with supplies that I have in the brewery anyway and I also plan to gow and document the giant colonies of other strains in my yeast collection.

On my last batch I put my dissolved oxygen meter to good use and tested the effectiveness of an wort aeration device that some brewers use. This device is a pipe with several small holes. As the wort flows through the pipe it pulls in air through the holes (Venturi Effect). The air then mixes with the wort and oxygenates that wort.

Building this device is simple. I used a 12 inch copper pipe in which I drilled 20 small holes. The holes are clustered around the top. The pipe was sanitized in boiling water and attached to the end of the vinyl tubing used for racking the wort from the boil kettle to the carboy.

The extract content of the wort was 11.0 Plato, its temperature 15 C and its volume 16 l.

I noticed that when wort is flowing through the device air is not necessarily drawn in. If this is the case some movement or shaking of the pipe is necessary to start the inflow of air which is accompanied by an audible gurgling. I did not pay attention to that at the beginning and as a result about ¼ of the carboy were filled without the device actually pulling in air.

Another problem was the substantial development of foam which required 2 pauses in order for it to settle so filling could continue.

Once the 5 gallon (18.9 l) carboy was filled to the 16 l mark. I swirled the wort around in order to provide some mixing action.

The resulting aeration in the carboy was about 4.5 ppm which is 3.5 ppm short of the 8 ppm that are recommended for most medium gravity ales and 7.5 ppm short of the 12 ppm that are recommended for lagers.

The problem with this device is that the air bubbles it creates are not small enough for an effective O2 transfer between air and wort. While a lot of foam was created, this foam had much larger bubbles than the fine foam that is created by using a mix-stir or a sintered stone for aeration. Both these methods have shown better performance in wort aeration (not yet published data).

To test this aeration method further, a 1 qt Mason jar was filled with about 1 pint of wort through the perforated pipe. The resulting oxygen content was about 3.5 ppm. Closing the jar and vigorous shaking it for about 30 s boosted the wort oxygen content to 7.3 ppm which is close to oxygen saturation possible with air (about 8.0 ppm).

It should be noted that these are the results of one limited experiment and that they can not necessarily generalized to say that aeration with a perforated pipe always leads to inadequate wort oxygenation.

Continuing the titration experiments I got a chance to titrate some mash tonight. The titration procedure was the same as described in the previous post and I won't repeat that here.

But here are the stats for the two mashes that were prepared. One for titration with HCl and the other for titration with NaOH:

• 100% Maris Otter Pale Malt pulverized with small coffee grinder
• 3 l/kg mash thicknes
• distilled water
• mash temp was ~61 C
• mash time was 15 min
• samples were both cooled to 25 C for the titration experiment

The results are shown here. This time I followed convention and plotted pH over the amounts of titrant that was added:

 This time the slopes leading up to the normal pH, which was 5.82, are pretty much the same. Based on A.J. deLange's feedback the large discrepancy these slopes in the wort titration experiment may have been the result of the fact that the normal pH for malt and wort is at the lower end of the pH where it buffers well. This happens around pH 7 and is very likely caused by the phosphate in the mash which has its 2nd pKa at 7.2. As discussed here weak acids buffer well around their pKas. 

I assume a repeat of the wort titration experiment is in order.

I finally got around to conducting two experiments which I wanted to do for a while now: the titration of wort and beer.

Titration is a process in which increasing amounts of a strong acid and/or base are added to a sample while the pH of the sample is monitored. This gives an indication of the pH buffer capacity of the sample at various pH points. It can also be plotted as a nice graph, a so called titration curve. More about the basics of pH and titration can be found here : An Overview of pH.

The set-up of the experiment was as simple as this: A diluted solution (~0.64%) of hydrochloric acid was prepared by mixing 37% Muriatic Acid with water. I don't like working with the concentrated form of this acid and the amounts of acid needed tend to be so small that they would be difficult to measure if the undiluted acid is used. In addition to that, a dilute solution (1.25%) of sodium hydroxide (NaOH), which is a strong base, was also prepared.

The wort, and later beer, sample was weighed and placed into a glass cup along with a stir bar. The pH meter probe was affixed to the glass cup using masking tape. (Masking tape seems to be a very useful tool in my brewery). While being stirred on a stir plate the pH was constantly measured. To determine the amount of acid/base that has been added a small cup was filled with the acid/base solution and placed onto a digital scale which provided a resolution of 0.01 g. The scale was zeroed while the cup, titration solution and a pipette was on the scale. By doing so the total amount of titration solution removed from the scale would be shown as a negative weight.

The wort sample had an extract content of 12.7 Plato.

The initial pH was measured and recorded. After that a small amount of acid was added and once the pH reading stabilized this reading and the amount of acid added so far was recorded as well. The process was repeated until the sample reached a pH of less than 2.0.

Titration of a fresh sample using a the strong base (NaOH) and acid/base titration of a beer sample followed. The beer sample had an original gravity of 12.0 Plato and an apparent extract of ~3.0 Plato. The beer and wort samples were from different batches.

Using a spread sheet acid and base additions were converted to milliequivalents of acid/base per extract weight in the case of the wort sample and per original extract weight in the case of the beer sample. This was seen as a suitable approach since the pH characteristics of the samples are largely determined by the dissolved substances.

Using this data the added amounts of acid (negative mEq/kg) or base (positive mEq/kg) were plotted over the pH of the samples which resulted in the following chart (click for larger version):

As expected the wort sample had a higher initial pH (5.18) than the beer sample (4.62). But what is also apparent is that around that pH the beer sample has a higher buffer capacity than the wort sample. Buffer capacity is the amount of acid that is needed to change the pH by a given amount. The unit I like to use is mEq/(pH*kg) which is milliequivalents of acid/base for each pH shift of 1 unit and for each kg of substrate. The latter doesn't count the water. For beer this buffer capacity was 92 mEq/(pH*kg) when adding the base and 76 mEq/(pH*kg) when adding the acid. Ideally they should be the same but measurement errors could have lead to this difference.

In the case of the wort sample, however, there was a distinct difference between the buffer capacity when adding an acid (29 mEq/(pH*kg)) and when adding a base (64 mEq/(pH*kg)). I don't know how to explain this and this is not the first time I noticed this discrepancy. It also appeared to me during my mash pH experiments. In order to double check my titration solutions I calculated how much of the NaoH solution I would have to add to a sample of the HCl solution to neutralize all the acid. I then performed that experiment and found that the actual amount I had to add was within 1.5% of the expected amount. So my titration solutions had their expected strength. At least in relation to each other.

The beer sample also shows an area of strong buffer capacity around pH 6.5 (where the curve is steepest between the two flatter sections). It is possible that this is the 1^st pKa of carbonic acid, which is at pH=6.4, since the beer sample was slightly carbonated.

While the beer and wort samples were not from the same batch it is very likely that fermentation creates additional pH buffers which are the cause of stronger buffer capacity of beer.

Conclusion

This experiment does little when it comes to finding ways to make better beer, but it gives insight into the pH buffer characteristics of both beer and wort. One thing to take away is that around the normal pH for wort and beer there is a nearly linear relationship between the amounts of acid/base added and the pH shift. This means that if the addition of X amount of acid drops the pH by Y the addition of 2X acid will also drop the pH by 2Y. Within the pH range that is practical in brewing there won't be a case where the addition of a little bit more acid causes the pH to suddenly “fall off a cliff”.

Some of you may have notied that there have't any updates to the wiki or the blogs here on Braukaiser.com. This is because I had to take a break from home brewing for a while. Although I brewed a few batches in the past to keep me supplied I didn't even take as many pH readings or determine the pitching rate with the microscope. Yes, other obligations took that much time away from brewing.

But I'm starting to get back into brewing and the science of it. The first batch of the next side-by-side is fermenting away and I have been updating my blog software. The goal is to finally get the spamming under control so I can enable comments to the blog posts. So stay tuned.

I also hope go become active on at least the AHA mesage board again. 

Many brewers wonder what difference bottle conditioning makes in brewing. One aspect of bottle conditioning is the presence of live yeast its effects on the aging beer.

Based on an on-line discussion, which I had with fellow brewers, I designed an experiment where I added a small amount of live yeast to my Doppelbock when I bottled the carbonated beer after cold conditioning.

The recipe, which I brewed about 7 month before this sampling, was very similar to the recipe posted on braukaiser.com. It was brewed with an enhanced double decoction. The first week of primary fermentation was done at 8 C (46 F) and the 2^nd week was done at 10 C (50 F). This was followed by a 1 month maturation at 12-13 C (54-56 F) during which time the beer was racked off the primary yeast into a Cornelius keg with shortened dip tube where it was allowed to reach its final gravity of 4.8 Plato. To help this maturation the beer was kraeusened with WLP830 (German Lager) 2 weeks into this maturation rest even though the primary fermentation itself was done with WLP833 (Ayinger Lager). The attenuation going into the following cold conditioning was 73% while the attenuation limit of the wort was 76.6%. During the maturation rest the beer also built up natural carbonation.

The beer was cold conditioned for about 1 month and 2 weeks and then bottled straight from cold conditioning at 1 C (34 F) into chilled bottles. The bottles were not purged with CO2 prior to filling. Oxygen scavenging caps were used because these were the only ones I had at hand. 3 of the bottles received about 300 Million cells of an active WLP830 (German Lager) culture. This yielded about 1 Million cells per ml in these bottles. No sugar or other fermentables were added since the beer was already carbonated.

After bottling the bottles were stored in the basement. The ambient temperature started at about 13 C (56 F) at bottling time and rose to about 17 C (64 F) over the following 3 months. 2 days before sampling the bottles were cooled to 10 C (50 C).

3 month after bottling and about 7 month after brewing I sampled a bottle that was bottles without additional yeast (non-yeasted sample) and a bottle that was bottled with additional yeast (yeasted sample) side-by-side. At the time of sampling I knew which was which but didn't know what to expect from the yeasted sample.

Aroma:

The non-yeasted sample showed the typical dark fruit (including black currant) and malt aroma of a German Doppelbock with a hint of alcohol while the yeasted sample showed a much more restraint aroma. The malt notes and dark fruit notes were rather faint. The aroma was more that of the young beer. There was also a hint of alcohol in its aroma.

Appearance:

Both beers were clear at serving temperature. The yeasted sample formed a thin, yet dense, yeast layer on the bottom of the bottle.

Foam stability:

My standard foam stability test is to take a Koelsch glass, pour the beer down the middle to let it foam up until the foam reaches the top of the glass. Then the time it takes for the foam to collapse and show the beer surface is taken. For both samples it took more than 13 min for that to happen.

Taste:

The taste experience was similar to the aroma experience. The non-yeasted beer showed a much stronger and more complex taste while the yeasted sample was more subdued. Both samples did not exhibit any off-flavors. In both cases the bitterness was low and did not linger into the finish. The non-yeasted sample was a bit sweeter which was also reflected in its lower attenuation

Mouthfeel:

Both samples exhibited the same mouthfeel.

Stats:

The yeasted beer did ferment a little further since at bottling time a small amount of residual fermentable sugar was available as can be seen from the attenuation to attenuation limit difference of 2.6% for the non-yeasted beer.

Conclusion:

The result of this tasting did surprise me yet supports my thinking that the hallmark flavor of German Bocks and Doppelbocks is in fact the product of oxidation and staling of the beer. It is assumed that the yeasted beer sample did not exhibit that flavor as strongly since the yeast was able to scavenge the oxygen that had been introduced during the bottling process.

The added yeast did not affect the head retention negatively in this case. One way it can do this is by releasing excessive amounts of Proteinase A into the beer which can break down foam proteins.

The pH was not negatively affected either which is a sign that there was not an excessive amount of yeast autolysis or not enough yeast to make a difference.

The idea that big dark beers benefit from small amounts of post fermentation oxygenation has also been brought up by fellow home brewer Fred Bonjour and warrants further investigation into optimal oxygenation rates ad well as aging times.

Many articles about foam stability, like this BYO article for example, mention that foaming during beer production can hurt the head retention of beer. The explanation is that foaming consumes the foaming compounds in the beer. I wanted to see if I can demonstrate this with a simple experiment.

I took two 500 ml PET soda bottles and filled each with about 300 ml of 1 C carbonated beer using a beer gun like device. The beer was batch A from the Kraeusen Experiment. Both bottles where then purged of air by squeezing and closing them once all air was squeezed out. To fill the head space with CO2 and provide the same storage conditions for both beers both bottles where shaken up once. After that they were stored in a 8 C fridge. The control was not shaken anymore but the “shaken” beer was shaken 3-4 times a day over the next 3 days. Each time the foam was allowed to fall back into the beer before it was shaken up again. Including the initial shaking, which was also done for the control, the “shaken” beer foamed up 10 times. This is 9 more than the control.

Shortly after shaking up the "shaken" sample.

On the 4^th day, after the foam has settled completely I filled the beer into 4 Koelsh glasses (2 for the control and 2 for the “shaken” beer) using a funnel that was held about 12 inches above the bottom of the glass. Each glass was filled until the foam reached the upper rim of the glasses. A timer was started when the first glass was filled. “shaken 1” was done filling at about 5s, control 1 was done at about 12s, control 2 was done at about 20s and “shaken” 2 was done at about 25s.

Here are images I took while the foam was collapsing.

Shortly after the glasses were filled. The two glasses on the left are the "shaken" beer and the 2 glasses on the right are the control. The order of filling them was 2, 3, 4, 1 with 1 being the left most sample and 4 the right most.

2 minutes into the experiment

After 8 min. All samples appear to have the same amount of head left. The numbers in the lower section of the picture indicate the order in which the glasses were filled. 

 Looking onto the top of the beer. In all samples the surface of the beer starts to show.

 After 9 minutes the foam in all samples receded to a point where beer is visible.

For both beers it took about 8-9 min until some beer showed through the foam when looking into the glass from the top. There was no significant difference in foam stability between the two beers. The same was true for lacing. While this method of evaluating foam stability is not as precise and repeatable as the ones performed by beer analysis labs, it is good enough to provide an objective assessment of the foam stability of a beer using.

Conclusion

I'm not saying that foaming does not affect foam stability at all but I was not able to demonstrate this using this simple experiment. It is possible that other factors play a role or that the effect is too small to be detected with such a crude approach. But for now, I would not worry about heat retention being reduced noticeably when the beer happens to foam during the brewing process.

Common brewing advice in American home brewing is to let the Kraeusen fall back into the beer after primary fermentation finishes. Very few brewers question this advice. However, all the German books I have read about brewing and some American home brewing books state that the bitter gunk on top of the Kraeusen should be removed. If it is allowed to fall back in the beer it will impart a harsh bitterness. As a result I have always fermented in 5 gal carboys and removed the Kraeusen through blow-off.

In order to find out how much taste difference that makes I set out to conduct an experiment. I brewed two batches of my Altbier. Both were fermented in buckets. On the first batch I allowed the Kraeusen to fall back into the beer. In fact I helped it a little towards the end since I needed to rack the beer before it was completely fermented. This however should not invalidate the results since most brewers leave the beer in their carboys well past the end of primary fermentation and until all Kraeusen has fallen back. For the second batch I skimmed the brown gunk off the Kraeusen regularly.

Both batches finished fermentation during a maturation phase in a corny keg before they were moved to 4 C to settle the yeast and precipitate haze. Since they were still cloudy after 2 weeks I added 3.5 g (½ pack) dissolved gelatin to each keg which helped clearing the beer.

The following table outlines the brewing process used for both beers:

 *) that pH value doesn't make sense to me. It should not be higher than the pre-boil pH and not that much different from the pH for batch B. But I did take the pH measurement on a sample of wort that had been standing unpitched for 24 hrs as opposed to the batch B post boil pH which had been taken the same day.

Both batches were fermented in buckets. A clear pot lid kept contamination out and provided easy access to the Kraeusen. The picture shows the batch A. The opening in the blue bucket lid was later enlarged to allow regular Kraeusen skimming for batch B.

The beer was partially naturally carbonated during maturation and then force carbonated during cold conditioning. The carbonated beer was bottled straight from the cold conditioning kegs.

I presented the beer as a double blind (participants didn't know the difference ) triangle test to 7 club members. Only 3 were successfully able to tell the difference. Those who were able to separate the beers correctly reported the following:

I was very surprised how few were able to tell a difference which appears so clearly to me. So I poured myself 3 triangle tests and have to admit that I only got 2 correct. Though I knew what to look for it wasn't as easy to keep the beers apart since the lingering bitterness of A seems to stick with one for longer enough to affect the taste of the next beer.

While this was a double blind triangletasting at a club meeting it was fairly unorganized. I didn't not get to start before many of the participants already had other beers. The setting was also not as quiet and free of distractions as one would expect for a taste testing.

The difficulty to differentiate the beers in blind tasting may explain why some brewers, who have tried this experiment before, found no difference and thus claim that it doesn't matter if the brown Kräusen gunk is removed or not. The type of beer may also play a big role. I can imagine that a hop dominated highly bitter IPA may not show the difference or may even provide a case where the beer, which didn't have the Kraeusen removed, is preferred. Having done this experiment and tasted the difference I'm convinced that the Kraeusen needs to be skimmed or blown off for any German style beer. The type of harsh and lingering bitterness, which I experienced in A, is considered a flaw even in the more bitter German styles like Northern German Pils and Altbier. The bitterness should be clean and linger only little. When it fades in the after taste is should never reappear later. The only German beer where I had this happen to me was Oettinger Pils which is one of the cheapest beers you can by there.

The results are in line with similar experiment reported in Zymurgy. The article can be read at the AHA forum.

When I sat down for lunch today I had 2 bottles of this beer and thought I poured the good one. After taking the first gulp I noticed that I got the wrong one. To me the taste was so bad that I poured it down the drain and poured the other beer which I was able to enjoy. I'll likely only finish beer B and pour out beer A.

Conclusion

Removal of the bitter Kraeusen gunk makes a difference in the quality of the beer even though it may not be detected by all brewers. The outcome of this experiment is enough to suggest that interested brewers try this on their own to see if it can improve the quality of their beers.

updates:

(1) to make up for my own failure to pass 3 triangle tests with this beer I set up a different taste test tonight. I took 12 identical glasses. 6 were filled with batch A and 6 filled with batch B. I then asked my wife to set up a random line of all 12 glasses. Taking my time and cleansing my palate with bread and water I went though each glass and took one to two sips to determine which beer it was. In the end I was able to separate them precisely based on both their hop taste and lingering bitterness. It shows that if I take my time I'm able to tell them apart reliably. 

(2) 1 month after the initial taste testing I brought samples to a club meeting and was surprised to see that the difference, which was very clear to me earlier, has aged away to some extend. Knowing what to look for I was still able to taste a difference but at this point I would not be surprised if others can't tell them apart.

This is a blog entry I have been thinking about a while. How precise is the ppg (points per pound and gallon) based efficiency calculation really. The reader should see this as something that is interesting to know and more of an exercise in using Plato and sg rather than something that any brewer needs to worry about

When calcylating efficiency (American) home brewers usually use:

(1) Eff = 100 * (gravity points of wort * wort volume) / (grain weight * grain extract potential)

Wort volume is given in gallon, grain weight in pound and extract potential in ppg. But that's not how efficiency is actually defined. It is defined as the ratio between the extract weight in the kettle vs. the extract potential of the grain:

(2) Eff = 100 * extract weight in kettle / grain extract potential

The grain extract potential is simple. It is its weight multiplied with the extract content determined in the laboratory mash. For most base malts it is about 77% (80% dry basis extract and 4% moisture content). Going forward I will call the grains extract potential "e". The weight of the extract in the kettle is a bit more complicated. For that we have to look at the Plato scale. Many brewers know degree Plato as another way of expressing wort strength. To be exact: the wort strength in Plato is the ratio between the weight of the extract dissolved in the wort and the the total wort weight:

(3) P = 100 * extract weight in kettle / wort weight in kettle

Extract weight in kettle is what we need for (2) but I still need the wort weight weight in the kettle. For that I simply remember that sg (specific gravity) is nothing else than the density of the wort in kg/l. It follows that the wort weight in kg is the product of wort volume in l and its specific gravity:

(4) extract weight in kettle = sg * wort volume in kettle

Now I can calculate the actual efficiency by using (2), (3) and (4). First some clean-up and shorter notatons for the variables:

• Eff_ppg = Efficiency calculated using gravity points and ppg for extract potential
• Eff_% = Efficiency calculated using Plato and extract % for grain extract potential
• P = wort strength in Plato
  
• sg = wort strength in specific gravity (1.xxxx)
  
• GP = wort gravity points ( = (sg - 1)*1000)
  
• V_l = wort volume in liter
  
• V_gal = wort volume in galon
  
• m_kg = grain weight in kg
  
• m_lb = grain weight in lb
  
• e_% = extract potential of the grain in %
  
• e_ppg = extract potential of the grain in ppg

With that the two efficiencies are:

(5) E_ppg = 100 * GP * V_gal / (m_lb * e_ppg)

(6) E_% = 100 * sg * P * V_l / (m_kg * e_%)

Grain lab analysis results don't show the extract as ppg but as percent of dry weight. To get the ppg equivalent I need to find a formula that calculates e_ppg from e_%. Since it is assumed that both efficicncy calculations (5) and (6) are equal I can set them equal:

(7) E_ppg = E_%

Now the busy work. They both use weight and volumes but in different units. That will be fixed by assuming these conversions:

(8) V_l = V_gal * 3.78
(9) m_kg = m_lb * 0.45

For simplicity I'll be using the simplified Plato to sg conversion. I'll later discuss how much that makes a difference.

(10) P = GP / 4 = (sg - 1) * 250

After putting all this into (5) and (6) I end up with this huge equation:

(11) 100 * (sg - 1) * 1000 * V_gal / (m_lb * e_ppg) = 100 * sg * (sg - 1) * 250 * V_gal * 3.78 / (m_lb * 0.45 * e_%)

Luckily this can be cleaned up considerably. V_gal and m_lb exist on both sides and fall out. So does (sg-1). All the constants can be consolidated into one. What's left is this:

(12) 0.476 / e_ppg = sg / e_%

solving this for e_ppg gives:

(13) e_ppg = 0.476 * e_% / s_g

This equation means that the extract potential in ppg depends on the grains extract potential in %, which is to be expected, and the specific gravity of the wort for which efficicncy is calculated. This was not expected. Here are a few examples. If sugar, which has an extract potential of 100%, is used to make a 1.040 sg wort it has an extract potetial of ~ 46 ppg. If it was used to make a 1.080 sg wort it has an extract potential of only ~ 44 ppg

The same is true for a base malt with 80% dry basis extract and 4% moisture. The actual extract content is 76.8%. If used for 1.040 wort its ppg extract potential is ~36.0 ppg. When used for 1.080 wort the extract potential is ~34.6 ppg.

As a final exercise lets look at a chart that plots the two efficies over the gravity of the wort. The wort volume is held constant while the grain bill is scaled such that the "%" based efficiency remains constant. In addition to that, the sg to Plato conversion is done using the officicial ASBC conversion formula which is a polynominal fit of their sg to Plato tables [deLange]:

(14) P = -616.868 + 1111.14 * sg - 630.272 * sg^2 + 135.997 * sg^3

While there are many similar formulas out there, this is the official one given by the ASBC (American Society of Brewing Chemists) and it should be seen as the standard.

This is the chart I came up with



It plots 3 curves. "Eff_% using the exact sg to Plato conversion" uses (14) to convert between sg and Plato. It is constant at 70% because this formula is used to calculate the necessary grain weight for the given volume and specific gravity. "Eff_% using the simple sg to Plato conversion" uses (10) to calculate the sugar content (Plato) from the specific gravity. "Eff_ppg" calculates the efficiency using gravity points and an extract potential of 35.7 ppg.

Despite the existing discrepanacy and incorrectness of the ppg based efficiency calculation, which I discussed earlier in this text, it tracks very well with the actual efficiency of 70% over a wide range of specific gravities. The reson for this is simple: while I showed that technically the extract potential in ppg also depends on the specific gravity, I also simplified the sg to Plato conversion by using (10) instead of (14). Both errors compensate each other to some extend. This also becomes clear when looking at the efficiency which is calculated using the simple sg to Plato conversion. It already shows an error of ~4 percent point at a specific gravity of 1.100.

Conclusions

Does it really matter in brewing whether you use the ppg based forumla or the Plato based one? Not really. If you always use the same formula for efficiency calculation and subsequent recipe design it doesn't matter at all. It may matter when discussing and comparing efficiency with other brewers. In this case the ppg based approach is within 1% of the actual efficiency for all realistic gravities. That error, however, is too small to be a conern in home brewing. Using the % based efficiency calculation with a crude sg to Plato conversion, on the other hand, can overestimate efficiency significantly. Thus care needs to be taken when converting Plato or Brix readings into specific gravity readings. That is in particular true for high gravity worts.

One last word about ppg or "points per pound and gallon". It should be called "point gallons per pound" or pgp since it is an expression of how many "point gallons" (gravity points multiplied with gallons) one can get from one pound of grain, sugar, etc. Its actual unit is gal/lb. 

[deLange] A.J. deLange: Specific Gravity Measurement Methods and Applications in Brewing.

This was the first time that I compared dissolved chalk against undissolved chalk in a 5-gal "production" batch of beer. Up to this point I have only done small scale experiments. Those experiments suggested that chalk dissolved with CO2 would be twice as potent in raising the mash pH as undissolved chalk is. As a result I new that I should cut the amount of chalk needed in half when it will be dissolved with CO2.

To brew the Schwarzbier I used the following grist. This is my standard recipe for a Schwarzbier:

• 53% Pilsner malt

• 40% Munich Type II malt

• 4% CaraMunich III malt

• 3% Carafa I special

The water was prepared from reverse osmosis water by adding the following salts. Version A uses undissolved (i.e. suspended chalk) while version B used dissolved chalk

The resulting profile was calculated as follows. Note that I do have an old analysis of the reverse osmosis water which I included in the calculated mineral profile:

*) There is some ambiguity as to how much calcium is actually contributed by undissololved chalk since it contributes only half its alkalinity potential, it may also contribute only half its calcium. These results assume that the chalk contributed all its calcium. The result is a lower residual alkalinity compared to the water with only half the chalk but dissolved.

The salts were then weighed. For beer A, they were mixed into the strike and sparge water. Since the chalk was not dissolved the water remained cloudy. Water treatment for the strike water was done in the mash kettle.

For beer A the salts were added to 2 liter soda bottles and reverse osmosis water was added. Then the bottles were carbonated with a carbonator cap. Once sufficiently carbonated the water cleared overnight which was a sign that the chalk got dissolved. This water was then added to the remaining reverse osmosis water for mashing and sparging. The mash water was prepared the night before to allow residual CO2 to escape. No chalk precipitated during that time, There was also no precipitation of chalk during the heating of the strike water or the sparge water.

The resulting pH values during the brewing process are shown in the following table. All pH values were measured with a sample cooled or heated to 25 C

For both beers the pH dropped during mashing which I contribute to the continued release of acidic compounds from the dark specialty malts. One oddity is that for batch A, which used undissolved chalk, the kettle full pH is lower than the cast out pH. Generally the pH falls during boiling. This is something worth paying attention to in future batches although it may also have been a measurement error. The initial mash pH of batch B is greater, which supports the fact that the residual alkalinity of its water should have been higher. This is the case if all the calcium added by the chalk is considered for undissolved chalk as it was done in the aforementioned water analysis.

I have not yet done a final tasting with these two beers. But preliminary tasting of both batches during their fermentation and conditioning did not show any significant differences

Conclusion:

To achieve roughly the same mash pH, only half the chalk is needed when it is dissolved with CO2.

After last year's Maibock, this is the 2^nd experiment where I compared a beer brewed with decoction mashing and a beer brewed with infusion mashing.

This time I wanted to see if there is a more pronounced flavor difference if the majority of the grist was composed of highly kilned base malts. This is one type of grist for which decoction mashing is still fairly common in Germany. test test test . So I chose a basic Dunkel recipe and the brewing process is outlined after the mash diagram for the 2 beers (click the diagram for a larger version).

It should be noted that the Dark Munich malt caught me by surprise and the mash for Dunkel II resulted in a rather unfermentable wort (attenuation limit 71%) which was compensated for during the mash of Dunkel III (see longer maltose rest). As a result the wort for Dunkel III was more fermentable. But both beers finished with a similar attenuation (67% and 69%). The poor fermentability was attibuted to the enzymatic weakness of the Best Malz Dark Munich which took a long time to convert (see the 40 min 70C rest of the decoction) and showed similar attenuation problems in subsequent beers.

3 ½ months after brewing Dunkel II and 3 months after brewing Dunkel III I tasted the beers side-by-side. It should be noted that at the time of this tasting I was not aware that I brewed one with decoction and the other one without. I had brewed quite a number of other beers in between and actually forgot how I mashed these beers and thought that they were both brewed with decoction until I checked my notes.

As you can see I did notice differences berween the beers but it is difficult to tie them to the decoction alone. I contribute the better clarity, lower head retention and thinner mouthfeel of the more intensely mashed Dunkel III to the stronger protoelytic activity in the mash. Its increased sweetness stems from the larger amount of residual fermentable sugars (see attenuation delta) compared to Dunkel II. I even considered Dunkel II (the non-decocted, more precisely only 3 min thin decoction boil) to be the more malty of the two beers.

Conclusion: This experiment was not as conclusive as the Maibock experiment and I would even call it inconclusive. There were too many differences between the analytic parameters (in particular the attenuation numbers) of the two beers to tie their slight taste differences to the more intensive mashing (including a 35 min decoction boil) of the Dunkel III. A future experiment needs to increase the decoction boil time to 60 min and attempt to keep the original extract, attenuation limit and attenuation and fermentation the same.

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When reading up on brewing Weissbier (also known as Bavarian Wheat) one of the suggestions is a ferulic acid rest. This rest around 43 C (110 F) works best at a pH > 5.7 and liberates ferulic acid into the wort. This ferulic acid is the precursor to 4-Vinyl-Guajakol which is responsible for the the clove flavor produced by Weissbier yeats. The more ferulic acid there is in the wort the more 4VG should be produced by the yeast and the more clove character the beer should have.

This is what I wanted to test. So I brewed a Weissbier recipe twice. Once with a simple Hochkurz mash and another one with an additional 30 min 43C rest at a pH > 5.70. For the second beer acid malt was added at 61C. This is above the optimal range for protoelytic activitry since I also wanted to limit the protein degradation during the time the mash spent in the 45-55C range.

The following table lists the process steps taken for the 2 beers:

Note that the fermentation for the 2nd batch slowed down signficantly after it reached a gravity of 6 Plato. At this point I decided to pitch a lager yeast and I cooled the beer for the time it took to propagate that yeast. This was to drop out most of the original yeat and limit autolysis. This was unplanned and I hope it is not the reason why the results of the experiment are like they are.

Tonight I tasted the two beers:

Conclusion: For the chosen yeast holding the ferulic acid rest didn't make any noticeable difference in the clove flavor that was produced during fermentation. While additional experiments should be made to confirm these findings it is very much possible that this rest is not worth the additional work.

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This is an experiment that I wanted to try for a while: Sparge a mash with cold instead of hot water.

Based on my understanding of the lauter process sparging with cold water should have no or only little impact on the efficiency if all the sugars, that will be dissolved, are dissolved during the mashing process. While a colder sparge could slow the speed of the run-off by causing the wort to be more viscous and flocks of coagulated protein be smaller it should not affect how many sugars are left behind. Especially in batch sparging where there is no concern about channeling through the grain bed.

I decided to give the cold water sparge a try on one of my Schwarzbier recipes. But since I also wanted to change the grain bill slightly it is not a true side-by-side where only the temperature of the sparge water changed. Here is what I did for the two beers:

The things to note is that the conversion efficiency was very high on both batches. Almost all of the extract potential was realized in the mash which is an indication for good and complete mashing. The lauter efficiencies (percentage of dissolved extract that made it into the kettle) for both beers were very similar and as a result the efficiencies in the kettle were very similar as well. The differences that can be seen are easily within measurement errors.

This shows that a cold water sparge does not necessarily lower your efficiency. 

It should also be noted that the 2nd runnings, which were the cold runnings, never cleared up. The remained hazy throughout the sparge. 

Tonight I tasted the beers. Here are pictures that show the color and clarity of the beer

And the taste notes:

The cold sparged beer is definitely a slightly more hazy than the hot sparged version. This may actually have been the result of the cold sparge although I don't have a solid explanation for this. If the haze results from an increased protein content it may also explain the slightly better head retention and fuller mouthfeel.

Conclusions:

• Cold sparging does not have strong adverse effects on efficiency and beer quality
• when a mash-out is performed it has no apparent effect on the fermentability of the wort. I don't know if this is still the case when no mash-out is done.
• it may make the beer more prone to haze
• it does not really save time since the wort at the end of the lauter will be colder and require more time to be heated to boiling temperatures
• it can save the need for a pot for heating the sparge water
• Since the spent grain temperature is lower at the end of a cold sparge less energy is wasted.

While this was an interesting experiment I don't plan to repeat it in the near future. At this point I don't see any benefit in this practice except for cases were I forget to heat the sparge water.

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A few weeks back I decided to write another brewing water calculation spread sheet. The formulas were mostly taken from the literature and existing spread sheets. Then I decided to add a cation (positively charged ions) to anion (negatively charged ions) balance check just to see if the water profile that I created made sense. This is when I noticed an imbalance when creating brewing water from scratch by using distilled water and salts. The resulting water should not show an imbalance and every cation should have matching anion. But it was showing an imbalance when chalk was used. So I gave the fomulas used for chalk a closer look.

 And found that 1 mol (a unit that is proportional to the amount of molecules/ions of a particular substance) of CaCO3 was assumed to add one mol of bicarbonate to the water. And that in most spreadsheets and calculators the bicarbonate contribution was later used to calculate the alkalinity as CaCO3. But that didn't seem right. If CaCO3 adds only one bicarbonate, it also needs to add one hydroxyl ion (OH-):

(1)  CaCO3 + H20 -> Ca2+ + HCO3- + OH-

Since this would liberate hydroxyl the pH of the water would need to rise. If that is not happening then chalk can also be dissolved in the presence of CO2

(2)   CaCO3 + H2O + CO2 -> Ca2+ + HCO3- + HCO3-

In this case each mol of chalk would add 2 moles of bicarbonate. Yet another reaction is possible in the presence of acid and free protons

(3)  CaCO3 + H+ -> Ca2+ + HCO-

(4)  HCO- + H+ -> H2O + CO2

If neither of these reactions hapen the chalk won't dissolve. And that is clearly happening in brewing: If you add chalk to the brewing water it just turns the water cloudy and it will eventually settle. 

But does it really matter if the chalk dissolves or not? No. Because the bigger picture is that we added the chalk to give the water+chalk mixture more "alkalinity" I.e. acid buffering capacity. That acid buffering capacity is needed to reach a targeted mash pH once the malt, and with it acid buffers, has been added. At that point reactions (3) and (4) can take place. Whichever reaction is happening (1)..(4), chalk can neutralize 2 equivalents of acid and for all intents and purposes 1 ppm of chalk should therefore raise the alkalinity by 1 ppm as CaCO3. 

But that is not what most water treatment spreadsheets assume. They assume that 1 mmol/l CaCO3 adds 1 mmol/l HCO3- (bicarbonate) which drops one negative charge on the floor and caused the imbalance that I noticed. And then they go ahead and convert the ppm HCO3- to alkalinity as ppm CaCO3 by multiplying with the factor 50/60. In the end the addition of 1 ppm CaCO3 raises the alkalinity by only 0.5 ppm as CaCO3. This certainly seems wrong and I thought I had it all figured out until I decided to confirm this theory with an experiment.

The experiment is seemingly simple. Make small mashes with 3 different waters that are supposed to have the same residual alkalinity and test their pH. The first water (A) would be reverse osmosis water and serve as the control. The second water (B) would be reverse osmosis water with chalk and calcium chloride added such that the added residual alkalinity is 0 if the chalk contributes 2 alkalinity equivalents. The 3rd water (C) has chalk and calcium chloride added such that the added residual alkalinity is 0 if chalk contributes only one alkalinity equivalent. Whichever water that causes a mash pH to match the RO water mash pH the closest would have used the correct formula for alkalinity contributions by chalk. Here is a summary of the waters used:

• water A: reverse osmosis tap water
• water B: RO water + 80 ppm CaCO3 + 290 ppm CaCl2*2H2O; this increases the Ca2+ content by ~110 ppm
  • if 1ppm CaCO3 adds 1 ppm alkalinity as CaCO3 then the water's residual alkalinity (RA) increases by 0.0 over the RO water's RA
  • if 1 ppm CaCO3 adds 0.5 ppm alkalinity as CaCO3 then the water's RA decreases by 2.2 dH (German Hardness) or 40 ppm as CaCO3
• water C: RO water + 150 ppm CaCO3 + 150 ppm CaCl2*2H2O; this increases the Ca2+ content by ~110 ppm
  • if 1ppm CaCO3 adds 1 ppm alkalinity as CaCO3 then the water's residual alkalinity (RA) decreases by ~4.4 dH or 80 ppm as CaCO3
    
  • if 1 ppm CaCO3 adds 0.5 ppm alkalinity as CaCO3 then the water's RA remains unchanged compared to the RO water

200ml of each water were taken and heated to ~64C in the microwave. Then 50g of crushed pilsner malt were added to each water sample and stirred in. The mashes were occasionally stirred and a 15ml sample was taken from each mash after 5 min and cooled to 22C when it was measured with a pH meter. The results were surprising:

• mash A : pH = 5.76
• mash B : pH = 5.69
• mash C : pH = 5.77

According to these results the chalk added only 0.5 ppm alkalinity as CaCO3. And the pH shift for mash B is even in the range that would have been expected from the 2.2 dH RA drop. According to Kolbach the shift is 0.03 pH units for each dH which would be 0.066 and the results show ~0.07.

I couldn't believe it and started to ponder why that would be the case. Why is the added CaCO3 only neutralizing 1 equivalent of acid and not 2? Maybe it has something to do with the chalk not being dissolved.

So I conducted another similar experiment. This time between a control, water with suspended chalk and water with dissolved chalk. The chalk would be dissolved with CO2 which is brought into solution through shaking. Here is what I did. I added 0.24 g chalk and 0.88g calcium chloride to 1.5 l of reverse osmosis water. This is twice the salts added to water B in the previous experiment because I wanted to pronounce the effect of the residual alkalinity difference. I then shook this water and the added salts in a 2l soda bottle until the calcium chloride was dissolved. Immediately after shaking, without giving the chalk a chance to settle, I poured off 200ml for sample B. I then removed another 300ml in order to increase the head space. This headspace was then filled with CO2 and the bottle closed. When I started shaking the bottle, it immediately contracted which was a sign of the CO2 going into solution. After some shaking I let the bottle sit until the water became crystal clear again. This was not the result of the chalk settling but it being dissolved in the water. I then took 200ml of that water for samle C:

• water A: reverse osmosis
• water B: RO + 160 ppm CaCO3 + 580 ppm CaCl2*2H2O
  • RA = -4.4 dH or 80 ppm alkalinity as CaCO3 if chalk adds 1 alkalinity equivalent
  • RA = 0 dH or 0 ppm alkalinity as CaCO3 if chalk adds 2 alkalinity equivalents
• water C: water B + CO2
  • RA = -4.4 dH or 80 ppm alkalinity as CaCO3 if chalk adds 1 alkalinity equivalent
  • RA = 0 dH or 0 ppm alkalinity as CaCO3 if chalk adds 2 alkalinity equivalents

I then heated both samples to 68C, added 50g crushed pilsner malt to each and rested (with occasional stirring) them for 10 min. After that I took 15 ml samples and cooled them to 20-21C:

• mash A : pH = 5.67
• mash B : pH = 5.47
• mash C : pH = 5.66

So it appears that dissolving the chalk in the mash water changes its alkalinity potential. undissolved chalk has less alkalinity potential than dissolved chalk since mash B showed a much lower mash pH which could only have been the result of a lower RA than the 2 other mashes.

But why is this? Does not all the chalk dissolve in the mash as commonly assumed? And if yes why is that? And would it always be 50%? Shouldn't there be enough acid for this to happen via reactions (3) and (4)?

For now I don't have an answer to this.