Interview with Michael Tonsmeire, the Mad Fermentationist.

Michael Tonsmeire, the Mad Fermentationist

Michael Tonsmeire, the author of American Sour Beers-Innovative Techniques for Mixed Fermentations (Brewers Publications, 2014), is an award-winning homebrewer, certified beer judge, beer blogger (, and writes the Brew Your Own Advanced Brewing column. 

Tonsmeire has consulted and collaborated with a dozen of America’s best craft breweries including Modern Times Beer Co. ( in San Diego where he develops the recipes, processes, and microbes to produce their sour beers), and Commonwealth Brewing Company.   

He has presented at the last two AHA National Homebrewers Conferences, as well as homebrewing conferences in Norway and Brazil .  Michael Tonsmeire resides in Washington, D.C.

If you are interested in sour beers, you really must follow Michael Tonsmeire’s blog The Mad Fermentationist (Click the link to subscribe to his blog).  I’ve been a fan of his for a long time and I look forward to his emails letting me know when he has posted a new .  He is super busy with book tours and other appearances around the country and elsewhere.  Check out his Twitter page and make sure you go to one of his appearances near you. 

He was gracious enough to take the time to answer these questions about sour beers for the readers of  If you want to learn more, click the link to his book (on the right) and purchase the definitive book on American Sour Beers, already a classic.

Interview with Michael Tonsmeire:

1.  Q:     For those who think the only sour beers are Flanders red and brown, lambics, gueuze and Berliner Weisse, can you explain how you can make a sour beer from just about any style?

MT:   While those are a few of the classic acidic styles, they are not the only sour beers. Much of the fun I have brewing comes from taking flavors from several styles and figuring out how they fit together. As with any beer, determining the ideal balance is the most important step. For example, assertive sour and bitter clash, so for a sour IPA you’d need to either back down on the typical bitterness or focus more on funky aromatics with light acidity. A roasty beer benefits from some balancing sweetness, so for a sour stout select microbes or a process that doesn’t result in a completely dry beer.

2.  Q:     Which styles would you not want to turn into a sour beer?

MT:   Anything strong, dark, hoppy, or spiced are tricky but there are no firm rules. As above, these beers might require stabilizing to preserve sweetness, blending, or specific microbes.

3.  Q:    When adding the “dregs” from other sour beers to fresh yeast and bacteria, what are you hoping to gain?

MT:   It depends. In many cases the microbes in commercial beers are more aggressive than those from yeast labs, so they can be helpful for higher alcohol sours. They can also add flavor variety if you are souring several beers to blend. I usually call them microbes with a resume, the beer gives you an idea of what sort of flavors to expect.

4.  Q:     How do sour beers age? Which flavors drop out and which might come forward?

MT:   Generally they age well. This is mostly because Brett will continue to scavenge oxygen, reducing the risk of oxidation. Generalities are tricky, but usually they get funkier and fruitier as they age, although actual fruit will fade. 

5.   Q:    Do you think it would be beneficial to come up with an objective scale of acidity (possibly with associated pH), similar to the SRM color scale or the IBU level, that everyone can relate to when describing sour beers?  We could call it the Tonsmeire scale…

MT:   IBUs and SRM like pH (or titratble acidity) aren’t subjective, they are objective. As more breweries include these measures on their bottles, people will learn how they correlate with their impression of acidity. 

6. Q:    Can you tell us which you prefer, fermenting a whiskey or rum barrel, or fermenting in a wine barrel? 

MT:   Both work, it just depends on the flavor you want. I tend to like wine barrels for paler beers, spirit barrels are wonderful for darker beers.

7. Q:      How do you handle your yeast/bacteria cakes for subsequent brews? 

MT:   I sometimes repitch a scoop of slurry along with some fresh brewer’s yeast, but more often I just pitch dregs from a favorite batch along with whatever Sacch I have on hand. I also have a house saison culture that I harvest from the bottom of the keg after it kicks (not ideal, but it has worked well so far)!

8.  Q:     Why do you think some yeast/bacteria blends produce better beers only after the first or second batch is finished?

MT:   Often commercial blends are designed for mellow acidity, repitching tends to favor quicker-growing Lactobacillus. It’s about preference, not better and worse.  

9.   Q:    What does the presence of a pellicle tell you about a sour beer?  Does whether a pellicle drops or not make any difference as to when the beer is ready to drink? 

MT:   I think of a pellicle like airlock bubbles, a general indicator of what is happening but not something to trust fully. A thick pellicle indicates excessive oxygen in the head space, which is something I try to avoid as it can lead to the production of acetic acid. Steady gravity and flavor are the only factors I look at for timing blending , fruit, and bottling. 

10. Q:  It almost seems like the descriptors used for Brett beers are for insiders only.  Descriptors like farmyard, funk, funky, barnyard, horse blanket can only be understood by those who have tasted a beer fermented with brett.  Do you think anyone will come up with better descriptions that even sour beer virgins can understand?

MT:   Those are the best flavor descriptors that I’ve heard for those aspects of Brett (there simply aren’t more common corollaries in modern living), but Brett can also produce esters reminiscent of pineapple, guava, juicyfruit etc. What is produced all depends on the strain, how it is used, and what substrates are available. 

11. Q:   Can you describe the difference between a beer that has been acidified naturally with lactobacillus and acetobacter bacterias and one that has been artificially acidified with lactic acid, vinegar, and possibly malic or citric acid? 

MT:   More natural souring processes tend to produce more rounded flavors. There is nothing wrong with a little bottled acid to enhance the acidity, but alone in high quantities food-grade lactic acid can come off as artificial/chemical/salty. For me it also misses the point of what makes sour beers so interesting, like adding hop extract with no late boil or dry hop additions. I added phosphoric acid to many of my clean beers for pH adjustment, this is where refined acids shine.

12.  Q:   Why do you think adding fruit is so popular when making or drinking sour beers?  Are they so one dimensional that you need the fruit to add some complexity and balance?

MT:   Fruit is naturally acidic, so it makes an easy pairing with an acidic beer. Fruit is especially popular in quickly soured beers that don’t have any interesting character from Brett, barrels, etc. For some classic brewers it also provides an option for barrels that turn out bland, I’d never add fruit to my best base beer, but I also wouldn’t waste it on unpalatable beer. It covers up those subtle funky and fruity flavors that are produced by the microbes and aging.

13. Q:  Can you give us some generalities on what fruit goes best with what kind of sour beer?  Ie. Stone fruit with lighter beers, or cherries with dark sour beers, etc.

MT:   I tend to prefer lighter flavored fruit in paler beers (e.g., citrus, peaches, nectarines, white wine grapes) and more assertive fruits (raspberries, cherries, blackberries) in darker beers. I’ve always preferred gueuze over kriek and framboise, because it showcases those subtle mineral and lemon notes that the brewer has taken so long to create. If I wanted a pale beer with 3 lbs of raspberries per gallon, I’d quickly sour it and then load in the fruit!

14. Q:   If someone wanted to try and make a beer inoculated with wild yeast, what can they do to increase their chances of getting good results?

MT:   Making starters exposed to the air is a great way to build up microbes to avoid catastrophic results. Once they are built up evaluate and pitch the ones that don’t have major off flavors. Dropping the wort pH below 4.5 is another option, as this inhibits some of the less-positive early residents. 

15. Q:  If you were going to inoculate with wild yeast, would you prefer to bring the wort outside and let nature fall into it, or would you rather inoculate and ferment a small batch of st15. Q: arter outdoors, taste it to make sure it is ok, then add that to your wort?

MT:   Lambic brewers have been cultivating microbes in their breweries, equipment, and barrels for decades or centuries. If you haven’t, your odds of success are much lower. Best to give your wild beers as much advantage as you can at the start. 

16. Q:  If you were going to suggest a first sour beer for a homebrewer to try and brew, what would it be and how would you suggest it be brewed? Ie. What bugs and yeast combination and are there any special requirements such as temperature, aeration, racking, or bottling that need to be addressed?

MT:   I’d suggest diverting a gallon of a favorite clean recipe, something <1.060, <25 SRM, and <20 IBUs and pitching dregs and/or a blend along with whatever yeast the recipe usually calls for. This could be anything from American blonde to Belgian wit, to English brown.  Get a few going to evaluate different microbes and open up blending options. If any are wonderful, repitch the microbes in a larger batch!

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