Infinium is collaboration between the Boston Beer Company and Weihenstephan brewery in Freising Germany. I had the beer once at a club meeting and didn’t think it was all that special. What interested me more, though, was the novel brewing process for which Boston Beer filed a patent application.
The problem in making a light high alcohol beer that complies with the German Purity Law (Reinheitsgebot) is that it has to be made from all malt and can’t use sugar to increase alcohol without adding body. Normal brewing procedures, even if aimed at high fermebtability, leave too much dextrins which would add too much body to the beer.
After not being able to find the patent or application on my own I asked around in my brewing club, with success:
The wort is brewed with a stepped mash that isn’t out of the ordinary. The patent application mentions long (150 min) rest at 63 C before a mash -out at 72 C is done. This will already produce a highly fermentable wort. Key to even higher fermentability, however, is the preparation of an enzyme rich solution from what they call “green” malt. “green” malt, also known as air-malt is malt that has been germinated and dried, but not kilned. The absence of high temperatures ensures that it is extremely rich in enzymes.
The enzyme rich extract is prepared my mashing the green malt at 57 C to preserve limit detxtrinase and b-amylase. The temperature is high enough to kill most micro organisms. The resulting supernatant can be added to the 65 C first wort in the kettle where the enzymes are able to continue to break down dextrines that were not broken down in the mash.
This by itself does not yet lead to a satisfactory fermentability and 24 hrs after the addition of the yeast another green malt mash is prepared. This time the supernatant is added to the fermenting beer where it is able to break down more residual dextrines w/o the enzyme life being cut short by the head of a mash or a boil. The patent appilication claims that all these processes can lead to a beer with an attenuation of 96%.
While this process seems fairly ingenious, a number of similar patents have already been issued. A simple patent search for “low calorie beer”, the main application for enzyme additions in brewing, lead me to this old Anheuser Bush patent:
It also talks about adding the enzyme rich supernatant from a secondary mash to fermenting beer in oder to lower residual extract or boost fermentation. The key difference to Boston Beer’s patent application is the use of green malt by Boston Beer. But I don’t think that this is all that crucial and that an Infinium like beer can easily be brewed without green malt.
In addition to that at what drying temperature is malt no more “green” malt but kilned malt?