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.


10 thoughts on “KaIPA^2

  1. Thanks for the followup post. I’ve been intrigued since seeing your initial posts on this topic. I’d love to see a side-by-side comparison between a traditional IIPA (using simple sugar to increase fermentability), versus the enzymatic wort method.

    I’ve found that beers that I’ve FWH’d tend to hold onto their hoppiness a bit longer than ones that I haven’t. I think with an extended fermentation, you may want to include a FWH addition, and plan on doing a dry hop as you near 80-90% attenuation to help keep the hop level high by the time the beer is ready. Also, maybe you might consider pitching a small starter at high krausen as the initial fermentation starts to slow down to help speed through fermentation since a beer this hoppy really want to be consumed as young as possible.

  2. I’ve been mulling over your results, and trying to understand why unboiled wort wouldn’t be subject to both DMS, as well as spoilage. The only thing I can think of on the spoilage side is that most of the mash spoilage organisms are lacto in nature, and that is typically inhibited greatly by hops, 54 ibu should be plenty to hold it at bay. I’d be interested in your thoughts about dms, but perhaps it’s just wort volume that made that not a factor.

    • The DMS is a no issue because of the smaller wort amount that is added. It is not enough to push the DMS level over the taste threshold.

      Spoilage might be held in check by the hops, but I got this idea from a patent for light american lager, so the 30 min at 60 C may be sufficient to kill enough of the beer spoilage organisms.

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  4. Very interesting technique! All malt, nearly 20°P beverage with 90% apparent attenuation. That sounds like an amazing beer.
    Maybe I missed it and you could just point it out, but what is the advantage to breaking down the sugar in the fermentation vessel instead of the mash tun? Such as with an overnight mash at a low temperature?

  5. How would your mash schedule look like if you could sterile-filter 500 mL of the wort after collection (i.e. not thermally inactivate the microbes)? All you need is enzymatic activity, right? Would you jump straight to you 70 °C mash temp to save time?

  6. I missed this comment because I didn’t have to approve it.

    I think I’d mash the same. the rest at 60 C not only kills the microbes but also indicates proteinases which may degrade the beer protein too much.

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