This all started when I was preparing one of my presentations for ANHC-3 and I looked into the patent for Boston Beer Company’s Infinium and other patents for high attenuation beers. I found that an enzymatically active malt extract (basically wort with active b-amylase enzymes) can be added to the fermenter. I was skeptical about this approach since malt is full of beer spoilage organisms (which is why you should not handle or mill malt in your fermentation area) and brewers rely on boiling to kill these organisms. However, boiling would also denature all the enzymes. According to the patent I found holding the mash for 30 min at 60 C before pulling the enzyme extract should be enough to kill the microbes but preserve enough b-amylase to be a useful in the fermenter.

So when I had a low fermentability Weissbier I gave this a try in a small test fermentation. Here are the two blog posts on that topic

The result was that I did not spoil the beer and that the enzymes in wort don’t break down as much of the residual sugars, and possibly proteins, as Beano does. Based on these results I was planning to use this technique on a full 18 l batch.

Since I expected close to 100% apparent attenuation it had to be a big beer. High attenuation and thus lighter body works well with a Double IPA. In fact many brewers of good DIPAs use sugar as an adjunct to add alcohol without adding body. So I brewed a stronger version of my KaIPA using this recipe: KaIPA^2 on Brewer’s Friend. It uses lots of my homegrown Cascade hops and hop extract for the bulk of the bittering.

Key was an initial mash rest at 60 C for 30 min and then filtering some of that mash to collect about 500 ml enzymatically active wort. That wort was cooled immediately and used to wake up the yeast. Using it to wake up the yeast was not necessary but why not. That way the yeast could get a head start and I would not forget to add it later.

When diastatic enzymes are used in the fermenter the wort fermentability set during mashing doesn’t matter which is why I raised the mash temp to 70 C after the 60 C rest. That way conversion was faster. The rest of the brewing process was as usual. To check the spoilage potential of the enzyme extract I took two wort samples from the cast out wort. To one of these samples I added the enzyme extract. Both samples were incubated at about 20 C to perform a wort stability test. To my surprise the sample to which I added the enzyme extract showed signs of microbial growth at about the same time as the other sample, which was after 3 days. This means that the enzyme extract did not carry substantial more microbes than the cast-out wort. If you plan to try this technique you may also want to do a wort stability test with and without the enzyme extract.

The fast ferment test for this beer also got some of the enzymatically active wort which is important to get an estimation of the actual attenuation limit of the beer. In this case the FFT stopped at -0.2 Plato which is an attenuation limit slightly above 100%.

To keep the production of higher alcohols in check I started the fermentation at 14 C (58 F) which is fairly low for the used yeast (WLP 001 – American Ale). After a few days I raised the temperature to 16 and then later to 20 C. The production of higher alcohols happens when the yeast consumes wort amino acids and that only happens during the growth phase which is generally over once high Kraeusen has been reached.

8 days after pitching the beer reached 5.0 Plato (down from 19.6 Plato). I let it go for another week in the primary fermenter before I transferred to a keg with some of the yeast. Later, after some more fermentation in the keg, I added gelatin and put the beer on tap. I was a bit lazy with taking more detailed notes.

I have been enjoying this beer for the last 2 weeks. The actual fermentation reached only 2.1Plato (an attenuation of almost 90%) which is higher than I expected based on the fast ferment test and the next time I’ll have to let the beer ferment longer. Unfortunately this IPA wants to be enjoyed young and 30 days after brewing the hop character is starting to fade. I still have the option of dry hopping in the keg which I may want to do.


OE: 19.6 Plato

AE: 2.1 Plato

ADF: 90 %

ADF (limit): 102 %

ABV: 9.6 %

IBU: 54 (Tinseth estimation)

beer pH: 4.30


Tasting notes:

Because of its high attenuation the beer has the mount feel of a Pale Ale but the high alcohol is evident both in aroma and taste. The hop character is fading but I have not added any dry hops yet since I was hoping to be able to rely on the 30 min hop stand with about 40 g of whole flower cascade hops.

Future improvements:

There are a number of things I want to improve in the future. On top of the list is to get the yeast to ferment closer to the attenuation limit. That probably means more yeast, possibly with some O2 during fermentation, and longer primary fermentation time. I think 95% attenuation is a reasonable target. To keep the current mouthfeel of the beer at 95% ADF I want to use a substantial portion of wheat or rye malt in the grist. Wheat malt would provide protein and rye malt would add b-glucans. Neither of these compounds will be attacked by the enzymes and should provide an upper limit for the attenuation.

This experiment was a definite success. The beer is a high gravity beer that is very enjoyable. Any concerns I had about adding non boiled wort to the fermentation were not justified. I also did not produce the dreaded “rocket fuel” that many brewers seem to get when they use enzyme preparations like Beano. I encourage others to give this a try.  Maybe this will become an accepted method of brewing DIPAs that are extremely or even too drinkable for their alcohol content.


A New Mash Chemistry and Brewing Water Calculator

When I started helping Brewer’s Friend as a technical adviser I couldn’t help but notice that the mash pH predicted by its brewing water calculator was way off. Since I have done extensive work on brewing water and mash chemistry already I took this as an opportunity to develop a new Mash Chemistry and Brewing Water Calculator from scratch. The goal was to build something that provides a simple and intuitive user interface yet implements the underlying chemistry to at a level of accuracy that is generally not done in brewing water calculators. In fact the only calculator that goes to that extent is A.J deLange’s NUBWS (Nearly Universal Brewing Water Spreadsheet).

Since Brewer’s Friend is an online recipe calculator the new calculator would also become an online tool. This worked very well in its favor since it is very cumbersome to model complex systems in spreadsheets. PHP, or any other programming language for that matter, makes that type of modeling much easier. In addition to that modern web browser technology makes it simple to create dynamic forms that can readily adjust the form to only asking the user for information that is actually needed based on the context.

That was 3 months ago and after many long nights of coding, re-coding, testing and even running more mash pH experiments version 1.0 has finally been released and is available on Brewer’s Friend.

When you first open the calculator it presents itself like any other basic water with sections for source water, salt additions, grist, mash pH and final water report following this flow chart:

Flow chart for basic use of the calculator

Flow chart for basic use of the calculator

But that’s not all. For those who need want to do more complex water treatment calculations, the full flow chart looks more like this:

Full flow chart for brewing water and mash chemistry calculator.

Full flow chart for brewing water and mash chemistry calculator.

All these additional section are hidden by default and can be shown on demand.



The first release features makes these features available:

  • Blending of two water sources
  • Bicarbonate/carbonate content can be set from either alkalinity or bicarbonate. pH can also be entered for increased accuracy
  • Electrical balance (ion balance) of the source water
  • Simple GH&KH measurements can be used as a crude way of specifying the source water.
  • Report of basic and advanced water parameters of the source water. Among the advanced properties are temporary/permanent hardness and CO2 partial pressure
  • supports all major salts (including magnesium chloride) as well as the hydroxides slaked lime and lye
  • Alkalinity reduction through boiling and slaked lime. These are features that rely on a more accurate implementation of the water’s carbo system
  • Wide range of supported acids including the less commonly used citric, tartaric and acetic acid.
  • Salt and acid additions can be made to all water or only the strike (mash) water
  • A different water source can be used for sparge water. In most cases that might be reverse osmosis water when the tap water is suitable for mashing.
  • Salt additions to sparge water or kettle
  • Sparge water acidification with a wide range of acids.
  • Detailed report of the treated mash water
  • Support for undissolved chalk.
  • Grist pH properties can be estimated from beer color or malt bill
  • Mash pH prediction based on balancing the various weak and strong acid systems that might be present (carbo system, weak acids and grist)
  • overall water report based on the mash and sparge water profile
  • target water comparison of the overall water report

For now this tool is only available as a stand-alone calculator but Brewer’s Friend is planning to integrate it into the recipe editor. This will eliminate duplicate entry of the beer’s malt bill. It will also allow the user to use saved source water profile(s).

Go ahead and give it a try. If you have feedback, positive or negative, please let me know:

Mash Chemistry and Brewing Water Calculator

In subsequent posts I’m planning to write more about some of the discoveries I made while writing this tool and how it’s mash pH prediction does compared to actual mash pH data that I have.


Another Doppelbock and oxygen tasting experiment

I finally got around to taste 4 bottles of my last Doppeblock that were treated differently with respect to yeast and oxygen. All 4 were bottled on 8/18/12 straight from cold conditioning (which lasted about 2 month) using a picnic tap and short racking cane. At the time of tasting they had been in the bottle for 4 month and 2 weeks.

The bottles received this treatment:

  • “no yeast/no O2” – did not receive additional yeast or O2
  • “no yeast/O2” – got a shot of O2 in the headspace shortly before capping
  • “yeast/no O2”  – received about 0.5 ml of WLP 830 yeast slurry and no O2
  • “yeast/O2”  – both yeast and a shot of O2

I did a tasting between  “no yeast/no O2”  and  “no yeast/O2” bottles 2 months ago. The results can be found here: Better Foam Stability Through Oxydation?. During that tasting I observed a distinct difference in foam stability that many readers contributed to a poorly cleaned glass. This time I made sure that the glasses were perfectly clean. That meant soaking in diluted vinegar to remove lime stains, washing with dish sop and a RO water rinse.


The 4 beers that were tasted. From left "no yeast/no O2", "no yeast/O2", "yeast/ no O2" "yeast/O2". The picture was taken during the foam stability test. The two samples on the right were poured 1 min after the samples on the left were poured.

The 4 beers that were tasted. From left “no yeast/no O2”, “no yeast/O2”, “yeast/ no O2” “yeast/O2”. The picture was taken during the foam stability test. The two samples on the right were poured 1 min after the samples on the left were poured.

Here are my tasting notes. When I refer to “dark beer aroma/taste” I mean the type of aroma/taste one gets from a good Doppelbock. Think of dried fruit mixed with black currant. I’m also listing pH, refractometer reading in Brix (I didn’t feel like taking hydrometer readings and the foam stability number* )

  • #1 – “no yeast/no O2” –  nice “dark beer aroma”. The aroma intensity is about the same as #2. (pH = 4.72, 10.4 Bx, foam = 5:30 min)
  • #2 – “no yeast/O2” – I made a note that the aroma is slightly stronger than #1, but than I made an opposing note on #1. I cannot conclude that it was objectively stronger (pH = 4.72, 10.4 Bx, foam = 8:30 min)
  •  #3 – “yeast/ no O2” – noticeably higher carbonation that #1 and #2, noticeably less of the dark beer aroma/flavor that #1 and #2 exhibit. Thinner mouthfeel than #1 and #2 (pH = 4.72, 10.1 Bx, foam = 10+ min)
  • #4 – “yeast/O2” – noticeably higher carbonation that #1 and #2, slightly less aroma than #3 (not confirmed in blind tasting), similar taste to #3 (pH = 4.68, 10.0 Bx, foam 10+)

After this tasting I did a blind tasting where I poured 2 glasses of each beer, scrambled the total of 8 glasses and attempted to match them to their respective beers. This is the groups I ended up with

  • group 1: one of #1 and one of #2
  • group 2: one of #1 and one of #2
  • group 3: one of #3 and one of #4
  • group 4: one of #4 and one of #3


This experiment solidifies the theory that the presence of yeast slows the development of the typical Doppelbock flavor. It does not show that the addition of oxygen, which is presumed to be the cause of this flavor, enhances this flavor of the beer after 4.5 months of aging. After 2 months of aging there appeared to be a more noticeable difference  (see  Better Foam Stability Through Oxydation?) At 4 months the addition of Oxygen did not make as much of a difference as the presence of yeast. This became apparent in the blind tasting where I could not keep the O2/no O2 versions apart but was able to identify the yeast/no yeast versions.

In future batches I do want to expand this experiment to developing a time line that shows when the “Doppelbock” aroma starts appearing depending on treatment. Maybe it makes sense to add O2 to 1/3rd of the bottles, no O2 and no yeast to another 1/3rd and yeast to a 3rd. This may allow brewers to control when the flavor/aroma of a Doppelbock (or other strong dark beer) peaks. An aspect that is very important for competitions.

It also shows that the beer was not completely fermented. Hence the continued fermentation when yeast was present which lead to higher carbonation and a lower refractometer reading.


* when I determine foam stability I take a Koelsch glass and pour the beer straight down the middle until the foam reaches the top.  The foam stability number is the time it takes until the foam opens up and the surface of the beer can be seen. Anything above 7 min is really good. Below 4 min, there is a problem with the foam stability.

Interesting paper on dry hopping

A few days ago, on the Homebrewer’s Association forum, I came across a link to this Peter Wolfe’s thesis on dry hopping. As with most papers, there useful information could be found in both the discussion of existing knowledge and the experiments themselves. Here are a few things I took away from it:

1.3.1 Hop Essential Oils: Hops produce the monoterpene mycrene, one of the major hop aroma compounds, immediately in the young cones. Mycrene is the largest essential oil fraction (up to 70%). “As the cone ages oxygenated terpenes are formed followed by the synthesis of sequiterpenes. Mumulene and Caryophyllene are the doninat sequiterpens and are also the send and third largest constituent of the overall oil”. – This supports the idea that hop cones need to “ripen” in order to develop their full aroma potential. An aspect that is important to those of us who go our own hops.

1.3.3 Hop alpha and beta acids: Bitterness contribution through isomerized alpha acids does not exist in dry hopping due to the lack of isomerization. In their unizomerized form alpha acids are not expected to add to the perceived bitterness based on work that has been done. My experience has been that hop pellets to taste bitter but that may also be due to the extremely high density of alpha acids compared to beer. Later it is mentioned that polyphenols extracted from the vegetal matter may add to perceived bitterness by themselves and synergistically with iso-alpha acids.

1.3.5 Glycosides: these are the combination of hop oils with a sugar molecule. Glycosides are less volatile than the hop oils themselves and thus provide the hop plant with a means of transport and storage. In brewing glycosides are extracted during boiling and survive that boil better than the essential oils. Hydrolysis of the glycosidic bond is know to occur in beer and most likely the low pH environment is the cause. Once the clycosdic bond is broken the essential hop oil is freed and able to contribute to hop aroma. In my brewing I commonly observe more hop aroma in the finished beer than what was present in the wort.

1.3.6 Biotransformed hop compounds: It has been shown that yeast activity is able to change hop aroma compounds. This changes the dry hopping character depending on when the hops are added to the fermenter.

1.6.1 Packaging and its potential ability to scalp dry-hop flavor: “The hydrophobic nature of hop aroma compounds makes them vulnerable to adsorption and absorption by hydrophobic polymers”. The most common occurrence of this is in cap liners. The extent depends on the type of polymer. In one study mycrene and humulene were found to have completely migrated into the cap liners of examined retail beers. This is an interesting aspect to those of us who bottle beers and don’t pay much attention to the type of bottle cap we are using.

2.3.3 Long Term Dry Hop Aroma Extraction: In long term experiments a model solution of 6% ethanol in water buffered to a pH of 4.2 was dry hopped and the linanol and mycrene content was measured on day 1, 4 and 7.  The solution was not agitated. The amount of these compounds dissolved did not increase over time. It actually decreased which suggests that the maxium extraction is reached after one day of dry hopping.

2.3.4 Short Term Dry Hop Aroma Extraction experiments were performed in shaken flaks and showed that the maxium concentration of mycrene and linanol is already reached after 240 minutes. This supports the idea that aroma extraction in dry hopping happens much faster than brewers think. Although it is mentioned that temperature can play an important role and that extraction at lower temperatures is expected to be slower. In general more hop oils were extracted from pellets compared to whole flowers of the same batch of hops. This is contributed to the fact that in pellet processing the hop material, including lupulin glands, is crushed.

Some of the aroma compounds were stable while others showed a decline even during the exanimated extraction times.

Brewery trials

Brewery trials were performed in conicals equipped with a pump that circulates the beer. All yeast was removed before dry hopping.

The trials showed that beer agitation (pumping) significantly improved hop aroma extraction. This was observed in the overall hop aroma of the beers and the measured hop oil levels. Again, pellets lead to more hop aroma extraction compared to whole cones. When whole hop cones were used extraction was also slower and reached its max not until around day 6. Polyphenol extraction was also higher with hop pellets compared to whole cone hops.

Estimating yeast growth

Recently there has been a lot of focus on yeast growth calculators for starters. But most of the various calculators out there base their data on work published in Chris White and Jamil’s yeast book. Unfortunately the yeast growth example given in that book was only for a non agitated starter. When a starter is constantly stirred all the yeast is kept in suspension in a homogeneous nutrient environment. That is not true for non agitated starters where yeast will sediment and only evolution of CO2 will cause agitation. As a result stirred and still starters are expected to show different growth behavior that cannot be simply approximated by adding a constant scaling factor to yeast growth.

Jamil’s pitching rate calculator supports stirred starter fermentation but the growth curve used for that mode is a simple scaling of the growth curve for non agitated starters. Jamil never published how he arrived at the model used in his calculator. As a result I have to draw conclusions based on what I can observe when I run data points through his calculator.

Before I get into comparing growth curves, I need to explain how I look at yeast growth. The primary factor in yeast growth is the available sugar. Within a practical range of wort concentrations the actual concentration of wort will have little impact on yeast growth. I’m still going to test this in a controlled experiment but observations from yeast propagation in my brewing seem to support that. Because of that I focus not not how many Million yeast cells are in a ml of wort, but rather how many Billion yeast cells get to share a gram of extract (sugars, proteins, minerals, etc) that is dissolved in that wort.

As for yeast growth, I care about how many new cells of yeast can be grown from that gram of extract. In their yeast book Chris and Jamil use a yield factor defined as new yeast growth in Million/ml per degree Plato drop of apparent extract. This takes into account that different worts can have different attenuation levels and with it varying amounts of fermentable sugars. While this is correct it requires knowledge of the wort’s fermentability and most brewers don’t know the fermentability of their starter wort. Furthermore the uncertainty of starter wort fermentability is likely +/- 5 % and this is well within the imprecision that one can expect from yeast calculators. I expect yeast growth calculators to have an error of +/- 15% or more. Because of that I feel confident in using Billion cells growth per gram of extract (B/g) as the yeast growth metric that should be tracked. Assuming a starter attenuation of 75%, the conversion factor between  “yield factor” and specific growth (B/g) is 13.3:

1 B/g = 13.3 M/(ml*P)

Now that I established how I plot yeast growth I can show some charts.

This one compared Mr Malty data for simple starters and stirred starters with the simple starter data from the Yeast book as well as a 2.7x scaled version of the simple starter data:

It is apparent that the growth curve for simple starter matches the data from the book, which makes sense. What surprises me, however, is that the stir plate data is not just scaling the yield for a given innoculation rate, but it also scales the inoculation rate. This means that the yeast growth calculator has different optimal innoculation rates for simple and stirred starters. That is something I don’t follow and my data contradicts that. More on that in a moment.

The following is a chart with my data. I have been using WY2042 since it is a low flocculant lager strain. Most of that has been presented in a previous blog post (Yeast growth experiments – some early results). What’s new is the non agitated data points and a few data points for using yeast that was stored in the fridge for 5 days before being used.

When the data is potted as growth in billion cells per gram over initial billion cells per gram, the data makes more sense. As the amount of extract available to each cell of the starting population approaches the amount of extract needed to grow a new cell, the growth per extract starts to fall. This is because the initial population is in a resting state and when sugar becomes available all vital yeast cells start to consume the sugar. A cell will not start budding unless it consumed all the resources needed to grow a new cell. If this was an ideal culture, where every cell consumes sugar at the same rate and needs the same amount of sugar to grow a daughter cell, cell growth would stop once there are more cells per gram of extract that it takes to grow the same amount of cells. This is because none of the cells would have access to the amount of nutrients needed to grow a new cell. But this is not such an ideal culture and some cells will consume nutrients faster than others and will be able to grow daughters while others can’t.

I also expect that yeast growth of a large population of older cells is reduced compared to young cells since the old cells will need to fill their reserves before they can start accumulating nutrients for growth. I don’t have enough data on that yet to quantify this effect.

This effect of dropping yeast yield is not as pronounced for a non agitated culture. This is because in such a culture not all yeast cells have the same access to wort nutrients due to sedimentation. Yet another reason why one cannot estimate the yeast growth characteristics in a stirred starter from a non agitated starter.

Based on my observations and knowledge of yeast growth so far, I think the following yeast growth model should be used for calculating expected yeast growth in stirred starters:

If (initial cells < 1.4 Billion/gram extract)
  yeast growth is 1.4 Billion / gram extract
If (initial cells between 1.4 and 3.5 Billion / gram extract)
  yeast growth is 2.33 - 0.67 * Billion initial cells per gram extract
  no yeast growth

For non agitated starters a growth rate of 0.4 Billion per gram should be assumed over the full initial cell density range (0 – 3.5 B/g). I don’t think that starters with more than 3.5 Billion cells/g  are practical. I expect the growth rate in starters to be affected by the shape of the vessel, the volume of the wort and more. The 0.4 Billion new cells per gram proposed here is a rough guess based on the data points I have so far.


The proposed model for stirred starters has been implemented in:


Better Foamstability Through Oxidation?

Oxidation experiments, again. This time on the latest batch of Doppelbock. Frequent readers may have seen the earlier posts on the subject of oxidation during Doppelbock aging: The effect of yeast on the flavor development of Doppelbocks and Follow-up on the Doppelbock yeast vs. no yeast in bottle experiment in which I tasted the same batch of Doppelbock with and without added yeast. This year I not only bottle some of the Doppelbock with yeast, but two bottles also has pure O2 added to the head space.

Last night I tasted a version bottled normally and one where I purged the head space with O2. The intend of the O2 in the head space was to see if it speeds up the aging process. Both beers were carbonated at bottling time and free of yeast. This tasting was 2 months after the beer was bottled and 6 1/2 moths after it was brewed.

comparing the color. bottled without oxygen (left) vs. bottled with oxygen (right)

The oxygenated version had a darker color as can be seen on the image on the left hand side and below. This color in crease is a known effect of oxidation and I have also observed this when I oxygenated and force aged a Pilsner. The increased color in the picture was not just because the oxygenated beer had a closed foam cover.

A better picture for comparing color.

But the biggest surprise was the incredibly poor head retention of the normal beer. It annoyed me during attempts to take a good picture for comparing color since the foam cover would quickly break open while it stayed close on the oxygenated beer. The shadow of the foam skews the color and darkness of the beer.

So I took another set of glasses and performed my standard foam stability test where I pour beer straight down the middle until foam reaches the top. I did this for both beers and waited for the foam to settle.

Foam stability test. Note the coarse bubbles on the non-oxygenated beer.

Foam stability test only one minute later.

The non-oxygenated beer clearly showed very coarse foam that collapsed quickly. Generally it would take 7 – 10 min between pouring and opening of the foam cover to show beer surface. But for the non oxygen beer it took just about 2 minutes. That was very surprising and I have no explanation for that. An internet search for foam stability and oxidation did not reveal any useful leads. It is certainly possible that something else, other than oxidation, was to blame for the poor head retention. I do have another normal vs. oxygenated pair and plan to taste this in a few weeks along with a bottle to which I added yeast.

As for taste, the normal beer did have a slight “dark malt” aroma. It’s bitterness was rather sharp and lingered a bit. The oxygenated version had notes of black currant (common oxidation aroma) and a slightly more pronounced “dark malt” aroma. It did not taste like cardboard or sherry. It had more of the desirable Doppelbock character than the non oxygen version and I would consider it definitely the better beer of the two. It won in both, taste and appearance.


The stark difference in foam stability is interesting and will require attention in subsequent samplings of this beer. The accelerated aging of the oxygen beer was expected. I was just surprised that the beer did not taste oxidized given the fact that it was actually bottled with a head space full of O2. Dark beers are known to withstand oxygen better due to the antioxidative properties of melanoidins.


I took one of the non O2 beers and a carefully cleaned glass and repeated the foam stability test again. This time the foam did not fall that quickly, but it still showed unusually large bubbles. There is a good chance that the glass I used for the test was not clean enough and skewed the results. I’ll try this again when tasting the other bottle with added O2.

Tasting of the enzyme beers

I finally got to taste the experimental beers that were treated with enzymes to fix an unexpectedly low attenuation limit (see Enzymes in the Fermenter).

This was after the beers were allowed to carbonate at room temperature for about 10 days. After that they were stored at about 10 C (50 F) for about 3 weeks.

The control, which had only water added to correct the  OE (original extract) to the same level as the others, had a very full mouthfeel. It did not taste sugary sweet but had a distinct full mouthfeel which did come with some increased sweetness, though. At time of tasting this beer had an apparent attenuation of 76% (final extract was 4.2 Plato)

The beer, to which enzymatic malt extract was added, did not open with a loud “plop”, but did gush and poured with lots of foaming. Looks like there was some additional fermentation in the bottle. The beer had a very nice light body that did not show alcohol hotness or seemed too thin. At time of tasting this beer had an apparent attenuation of 90% (final extract was 1.8 Plato)

The beer which had Beano added did also gush out of the bottle after opening and also poured with a lot of foam. It tasted even lighter than the beer with enzymatic malt extract. But it made the beer thinner than it should be. There were also some sharp alcohol notes, but I would not characterize it as “rocket fuel” either. At time of tasting this beer had an apparent attenuation of a whopping 96% (final extract was 0.8 Plato)

Here are the stats:

control malt extract Beano
corrected starting extract 17.8 17.7 17.7 Plato
Extract 4.2 1.8 0.8 Plato
ADF 76.4% 89.8% 95.5%
Alcohol 7.2% 8.5% 9.0% w/w
pH 4.4 4.37 4.34


The ezymatic malt extract worked very well for this beer. It did not spoil the beer as one would fear when adding non-boiled wort. It also did not go as far as Beano treatment which leaves sufficient residual body. Beano’s glucoamylase seems to be able to break more dextrins than the enzymes that were present in the malt extract.

Going forward I plan to employ enzymatic malt extract treatment in the fermenter on a full size batch. This would work well for a double IPA or an imperial Pilsner.

Yeast growth experiments – some early results

For a while now, actually ever since I got the microscope, I have been keeping track of yeast growth in starters, fast ferment tests and some beer fermentations. In some cases I was too lazy and did not record any data. But what I found is that the new growth per gram of extract (stuff dissolved in wort), measured in Billion per gram, was all over the place. Initially I thought I could come up with a simple formula to estimate cell growth based on wort volume and extract content. But that doesn’t seem to be the case.

So I started examining the issue in a more controlled environment. For my first set of experiments I prepared 6 l of ~10 Plato wort from old malt extract and some left over wort I had in the freezer. This was frozen in three 2 l soda bottles. I then grew some WY2042 from a slant to use in these experiments. WY2042, Danish Lager, works well since it doesn’t flocculate when its done fermenting. To conduct the experiment I would thaw one of the bottles with wort and keep it in the fridge. I then take ~230 ml of that wort innoculate it with yeast and place it on a stir plate covered with foil. The initial cell count was determined with a hemocytometer and the yeast was allowed to complete fermentation for 1 to two days. Then the final cell count is taken and the sample is allowed to settle in the fridge. For the next experiment some of the yeast sediment is kept in the flask and fresh wort is added. The amount of wort added is recorded as well as the initial cell count. Using this approach allows me to run a series of experiments with yeast of consistent freshness and only one stir plate. To eliminate age effects I went back and forth over the starting cell density range of 1 through 270 Million cells per ml. In the chart below you see Billion cells per liter, which is the same.

Here are the results:For reference I also added numbers I got from Jamil’s and the Wyeast pitching rate calculator.  The dashed lines show which experiment provided yeast for the next experiment.

There are notable differences at low and high starting cell densities.  In my experiments the specific growth I got at high starting cells counts (>150 B/l) was much less than the two pitching rate calculators predicted. The low growth makes sense since more sugar will be needed to feed the larger population during its lag phase. I think that this might be more pronounced with older yeast cultures where glycol reserved are lower (these yeast cultures sat only 1-2 days between propagation).

I also saw larger than expected growth at low starting densities.

Around initial densities of 100 B/l, the experimental results agree with the other two calculators which is good and means that there is some predictability.

You also see one data point for a 2nd series of the experiment. In that series I started a new culture from a slant and want to see if it behaves similarly.

The error bars get lager for higher starting densities since the error for counting the initial population plays a larger role when that population is large. E.g if the starting population is 1 Billion and has an error of 10% (+/- 0.1 Billion) and the final population is 100 Billion with a 1o% error (+/- 10 Billion) the error for the new growth of 99 Billion is ~ 10% or +/- 10 Billion. But if the starting population is 101 +/- 10 Billion and the final population is 200 +/- 20 Billion the difference is still 99 but with an error of +/- 22.

Stay tuned for more data as I have it ready for publishing.

Yeast un-flocculation for cell counting

One problem in cell counting is that the cell culture needs to be evenly suspended in its volume and any cell clumps need to be broken up. That is not an issue with poorly flocculating yeasts like German ale yeast. But heavy flocculators like English Ale yeast (WLP 002)  provide a challenge. I knew that any yeast can be un-flocculated in the presence of maltose since maltose inhibits flocculation. This makes sense since it it more advantageous for the yeast cells to float freely when food is available. However, adding fresh wort to a yeast slurry simply for counting its cells seems a bit wasteful.

So I asked White Labs about this and their response was to use sulfuric acid or EDTA (Ethylenediaminetetraacetic acid). A search on EDTA revealed that it is a chelating agent. This makes sense in the context of preventing yeast flocculation since it is able to chelate the calcium necessary for flocculation.  This gave me ideas for other chemicals that might work.

Tonight I spent some time in my lab/fermentation room to test a variety of chemicals for their ability to un-flocculate WLP002, the heaviest flocculator I have encountered so far. I had some WLP 002 sediment from the fast ferment test for a pale ale I brewed last weekend.

The experimentation set-up was simple. I added a little bit of WLP002 sediment, water and the de-flocculation agent I wanted to test to test tubes. Then I closed the test tubes and sloshed the contents around to see if the clumps are breaking up. When the sample was un-flocculated I inspected a sample under the microsope to check if there are truly no clumps of cells left. Here is what I found:

  • water: this was the control. While the yeast clump did break up it only broke up into small floccs of yeast. This was not good enough for counting.
  • fresh wort: it didn’t take long for the yeast clumps to break up into individual cells after brewing wort was added. This is the best option if the yeast sediment needs to be suspended anyway for pitching or as another stage of yeast propagation. This method does not kill the yeast and the viability can be assessed with methylene blue.
  • glucose: clumps broke up slowly. This method does not kill the yeast either, but it is not very practical since there are better options.
  • sulfuric acid: works very well. Clumps broke up very quickly and it doesn’t kill the yeast which allows for methylene blue staining. But sulfuric acid is a hazardous chemical and needs to be handled with care
  • PBW: Yes, Five Star’s Powdered Brewery Wash. I got the idea to use this since it also contains chelating agents. It works very well and the cells were quickly suspended as individual cells. It does not dissolve the yeast immediately but kills them. When stained with methylene blue a significant number of cells stained blue while the culture had a known viability of 95+%. PBW is much safer to handle than sulfuric acid and many brewers have it at hand.
  • GH test solution: since calcium chelation is the key for many of these agents and general hardness (GH) tests do just that I also gave this a try. It worked very well but is not practical due to its cost. The amount that can be found in a simple GH/KH test kit for $6 would only be enough to un-flocculate a few yeast sediment samples.
  • disodium EDTA: I haven’t tried this yet but plan to test it when I order from a place that sells it. I expect that it works and that it does not kill the yeast either.
  • Phosphoric acid: (mentioned by Northwestbeer in the comments for Yeast pitching by weight) Works very well, is generally available in a home brewer’s lab and does not kill the yeast. When I tried it I used about 2% phosporic acid (1 ml 10% phosphoric acid, 3 ml water and 1 ml yeast sample)

For now I’ll use fresh wort when I need to re-suspend the yeast in wort anyway and I’ll use PBW when I only need to count the cells in a given slurry of yeast without plans to use the yeast later.

Enzymes in the fermenter

You may remember the recent post about the Infinium’s patent pending brewing process and its mention of enzyme extracts in the fermenter. I recently brewed a Hopfen Weisse inspired Weissbier IPA where the wort fermentability was unexpectedly high. I decided that this was an opportunity to test the use of enzymes in the fermenter. So I took about 1800 ml of the young beer after primary fermentation and split it into three 600 ml batches. One became the control, one received an enzymatic malt extract and the last one got some Beano. I heard that Beano has the tendency to create “rocket-fuel” and I wanted to test this.

mashing the enzymatic malt extract

The instructions for the enzymatic malt extract came from this patent for low calorie beer where an enzymatic malt extract is prepared using a 30 min mash at 60 C. This kills most of the bacteria but keeps enough b-amylase active to be useful in the fermenter. Killing bacteria is important since the extract will be added directly to the fermenter without any boiling. I was curious if this really works since spent grain, which is raised to even higher temperatures for longer times during mashing, seems to be loaded with microbes. A fact for which I get a pungent reminder when I open a mash tun I forgot to clean on brew day.

The mash consisted of 70 g milled Pilsner malt and 360 ml reverse osmosis water. I was not too concerned about getting the correct mash pH. After all, I only needed enzyme extraction  and  some level of pasteurization. Set in a water bath I was able to hold a steady temp of ~60 C for 30 min. Temperature control of small volumes is challenging. A well insulated and pre-heated thermos may work too.

Filtering the enzymatic malt extract

The malt extract was filtered through a paper towel set into a funnel. Its extract content ended up being 10 Plato. This amounts to 75 % conversion efficiency. Not that this efficiency matters much, but I took the extract content of the malt extract into account when calculating the corrected starting extract for the beer. 53 ml of this malt extract was added to the 600 ml beer. About 8% of its volume. There was no science behind this ratio. Too much and I would dilute the beer too much and too little I would not add enough enzymes.

The Beano I used came in pill form and I dissolved one pill in 100 ml water. Beano’s strength is measured in GAU (GlucoAmylase Units). One Glucoamylase Unit (GAU) is the amount of enzyme activity that will liberate on (1) gram of reducing sugar as D-glucose per hour under the conditions of the GA Assay (Vri 511.002). (source http://vitallifeproducts.com). 22 ml of this solution went into one of the beer samples which added about 110 GAU per liter beer.

20 ml water were added to the control to lower its original extract since the other 2 experiments also lowered the starting extract of the beer.

The 3 fermentations immediately after being prepared

The following morning (about 10 hour later) I noticed strong fermentation activity in the fermentation with malt extract. The Beano fermentation showed some low activity. But since I did not control the actual amount of enzymes that went into each, it is perfectly reasonable that the Beano fermentation ended up will less enzymes than the malt extract fermentation.

10 hours later, the malt extract fermentation shows the most activity

After 9 days I concluded that all fermentations were done and I bottled the beers.

After 9 days

To carbonate the beer I added 4.3 g dissolved table sugar to each 500 ml bottle and some yeast.

I also got an opportunity to measure the current extract and pH. Most importantly I was able to taste uncarbonated samples. Here are the stats:

control malt extract Beano
corrected starting extract 17.8 17.7 17.7 Plato
days fermented 9 9 9 days
Final extract 4.3 2.5 2.2 Plato
ADF 75.9% 85.9% 87.6%
pH 4.48 4.4 4.35

As expected the addition of enzymes boosted attenuation. Beano seems to digest more dextins than a malt extract. I wonder to what extent the difference is caused by limit dextrins (1-6 glucose links), which can only be broken by limit dextrinase, an enzyme which likely did not survive the 30 min mash at 60 C. Beano’s glucoamylase is likely able to cleave both the 1-4 and the 1-6 links found in starch leaving only glucose and no limit dextrins.

It was surprising, however, that even with enzyme use during fermentation the apparent attenuation stayed in the mid 80’s. This suggests that the low wort fermentability may not have been the result of incomplete starch and dextrin break-down during the mash. After all, I was going for very fermentable wort and held 30 min rests at 55 C, 63 C and 65 C followed by a 45 min rest at 72 C. I was expecting to get an attenuation limit in the high 80’s with this mash schedule.

There was also a drop in pH. I contribute this to the extended fermentation activity, which was longer for Beano compared to the malt extract.

So much for the metrics, here are some brief tasting notes:

control: No noticeable off flavors. While this was a Weissbier yeast, it is a yeast that produces only limited amounts of phenolics. The mouthfeel is rather thick and the beer does not have the refreshing IPA character that I was going for

enzymatic malt extract: No off flavors. Whatever surviving microbes came in from the malt did not take hold and spoil the beer. I’ll have to see how this develops as the beer sits in the bottle for a month. The mouthfeel was much lighter and more  easy drinking than the control. This was the taste I was shooting for.

Beano: No off flavors either. The mouthfeel was even lighter than the malt extract version. But it was not the dreaded “rocket fuel” that others have gotten from Beano before. I think this version felt a bit too thin in its taste, though. I’ll have to defer to tasting a carbonated sample.


I think enzymatic malt extract in the fermenter works. It appears to be a viable option for creating highly attenuated high alcohol beers and I plan on using it on a full size batch in the future. I don’t know if it is a practical option for fixing low wort fermebtability in lower gravity beers since they may become too thin. After all, the enzymatic reactions will continue until all substrate, i.e. dextrines,  is gone.