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.

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

Discussion:

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.

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.

Conclusion:

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.

Update:

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.

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:

Conclusion:

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.

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:

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.

Conclusion

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.