Tag Archives: KMS

Brewing with Potassium Metabisulphate and Potassium Sorbate

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Perhaps it was during a Basic Brewing Radio episode,  maybe it was a wine making class I took at Brooklyn Homebrew, or simply having a roommate that is a sommelier, but treating beer like wine is an approach that i have been interested in using for the better part of a year.  In wine production, sometimes after fermentation is complete, chemicals like Potassium Metabisulphate (KMS)(K2S2O5) and Potassium Sorbate (C6H7KO2) are used to not only stabilize wine, but also to slow oxidation.  If anyone that you know is allergic to Sulfites, their trouble with wine is caused from this practice.
The purpose of adding KMS is to add self life to wine, since this treatment kills off lots of microorganisms, but it also slows the process of oxidation, which is tremendously important when aging wine for decades.  Potassium Sorbate stops yeast replication, so even after treatment, fermentation can continue, but the yeast do not reproduce and they eventually die.
For my first step into this technique, I brewed a basic wheat beer.  Once fermentation was done, I then treated 2.5 gallons of the batch with both KMS and Potassium Sorbate.  I made a chunky puree of fresh cherry’s from the corner store with about 2 lbs of Cherries and 2 cups of white sugar.  The puree went into both batches of beer.  The treated beer ended up with a Final Gravity of 1.014, while the untreated beer finished off at 1.011.  To treat the 2.5 gallon batch, I used 3/4 teaspoon of KMS and 2.5 teaspoons of Potassium Sorbate

Untreated (left) vs Treated (right)

Tasting of Treated vs Untreated:

Untreated:

appearance: a hazy pink that has a very white head.  There is almost an orange hue to the pink

nose: A very light scent of wheat with undertones of cherry

flavor: very light in flavor, a slight hop bitterness slips into a dry finish of wheat and cherry.

mouth feel: nice and balanced with a light body, the head does leave quickly but the carbonation is medium

overall: very pleasant summer beer.  The balance of the wheat and cherry works really well and the dry finish.  7.5/ 10

treated:

appearance: the head stays around longer than the untreated beer.  Color is identical

nose: Very similar to the untreated beer, but a very very slight chemical scent is at the end of the nose

Flavor:  that’s definitely sweeter than the untreated. The white sugar sweetness removes the dryness from this beer completely.  The wheat character is also faded.  The Cherry perception is increased.

mouthfeel: a rounder body with that chemical taste that is nearly undetectable. Medium bodied and the carbonation seems higher.

overall:  This worked better than I thought it would, the white sugar and the slight chemical flavor really brought out the carbonation and the cherry flavor.  Next time I will use a different sweetener and less chemicals, but this was a worthwhile endeavor.  This opens up very many possibilities!!!!

This process definitely worked, but it needs a lot of tinkering to make beer that is truly outstanding.  Luckily, I learned a whole lot about this process on my recent visit to Sam Adams. The end product I am hoping to make is a fruit beer that actually tastes sweet enough to be considered a dessert beer, but one that tastes very similar to the fruit used.  This could also really help in my cider, which I have yet to be fully satisfied.  Much more to come.

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“Coaching” Session at Boston Brewery

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One of the perks of winning last autumn’s Brooklyn Wort was a one on one coaching session with an employee of Boston Brewing. By the way, the next Brooklyn Wort is being held in Manhattan in October and entries start Aug 11 for the preliminary round.  Details are here. (http://www.brooklynwort.com/)

I was offered a bunch of options, like a phone conference with a marketing specialist, but I was really interested in speaking with a brewer that could help me out with some of the more experimental things I’m playing with in my kitchen, I mean brewery. I was hoping that one of the biggest Micros would be willing to let me take up an hour of time to really pick a pro brewers brain.

After months of failure trying to work out a date that I could make it up to Boston to actually get face time with someone, summer finally came to my rescue.  I grabbed two friends who happened to have a weekday off and drove up to Boston.

Rolling up to the “Boston Brewery” I was immediately taken back by how small the scale was.  It turns out that they only use a 10 barrel system up in Boston, be it a nice one, the vast majority of their beer is brewed at two other major breweries in other parts of the country.

that’s it?

The shock of that quickly wore off when I learned that the Boston Brewery is responsible for their cask room releases.  The brewery is all set up for nice tours and cool pictures with plenty of history about Sam Adams and lots of awards that they have won hung above.  I would recommend a visit for someone who hasn’t really toured breweries before, you get to smell hops, check out grains, and walk the floor of the brew house.

big barrels!

Luckily, the majority of my visit was spent with Grant,  a recent addition to Boston Brewing, who is one of the brewers there.  After a few minutes, Grant figured out that I wasn’t there for some fun chat about pitching rate, but that I had a few more in depth questions that I would like to discuss.

Grant dropping knowledge

The talk very quickly turned into a great coaching session with ideas being shared about wild yeast identification and pH adjustment, with a little bit of info about KMS and stabilizing bigger beers.  Having someone with this kind of brewing knowledge really explain some of the science behind my ideas essentially leapfrogged my experiments about 2 years forward.  On the way out, he even hit me up with a couple of online resources that are exactly what I was looking for.  Grant made the four hour drive worth it.

This experience really renewed my affection for Sam Adams.  Sam was one of the first Micros that I ever tasted and many times, it was their brew that was my first exposure to different styles of beer.  Having them treat me with such a high level of respect and openness really boosted this beer back to the top of the pile for me. I know what I’ll be drinking next time I’m at a normal bar.  Much more on the information that I learned about in the coming posts, I hope Sam Adams starts a beer school!

Many thanks must be said to both Michelle and Grant.

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