Monday, August 18, 2014

Introduction for Pre-Primary Souring

I'm headed out to sea for a couple weeks of work and I wanted to get another blog post in before I go. This post is an introduction to one of my big projects for the next year of brewing - pre-primary souring. I've got one batch in bottles where I've used one of the approaches here but I'll have to wait until I come back to write up the brew day and give my tasting notes. This is pretty text heavy and picture poor, but I'll update it with pictures as I take more of these various approaches again with a camera around.

My goal with pre-primary souring in my homebrews is to get a controlled amount of tartness into  beers in the same sort of time frame as a typical primary fermentation. And also to not have live souring microorganisms in the fermentation and bottle. I am not try to make a quick sour beer or re-create the sort of fermentation profile you find in classic sour beers like flemish sours and lambics. And I am not trying to do 'pre-primary' sour in lieu of live souring during my primary (or in a secondary) fermentation. I think for beers you really want to be sour, putting in the time and letting the longer mixed fermentation will contribute more to the final flavor profiles you're looking for. Instead I'm interested in pre-primary souring to add lower levels of acidity to beer styles which I think would benefit from it. I'd like to get a controlled mild to moderate tarntess into certain beers like some of my saisons. In scenarios where I am really going for more of a sour character I may use this sort of approach to help out the microorganisms I want (as some microbes like Brettanomyces and Lactobacillus benefit from a lower initial pH), but when I am looking for a real acidic beer I'll stick with the long mixed fermentation of bacteria and yeasts and I feel that contributes to the flavor profiles I'm looking for in addition to the tartness.

So what do I mean by pre-primary souring? It is introducing some acidity to the beer before I begin my primary yeast driven fermentation. This can be achieved in a couple of ways, and the reason that I'm targeting souring before the primary is that it gives me the control I want. I'd like a more controllable/repeatable level of acidity as well as independent control of bitterness and acidity. If I were blending an acidic beer post-primary with a hoppy beer, I lose this control. The more acid beer I add, the less hoppy beer I get. But souring before my primary, and boiling (or re-boiling) the soured wort allows me to adjust the hop levels to what I want after the acidity is set. Some of the ways that you can do sour a beer before the primary are by adding lactic acid or acidulated malt, by sour mashing, or by 'sour worting'.

Adding lactic acid - I won't really cover this as I think it is pretty simple. Basically if I were going to add lactic acid for residual tartness (not mash pH) I would do it to taste after primary fermentation is done. This may influence yeast character as the yeast would be fermenting at normal pH rather than lowered pH (as is the case in all other methods below). Basically lactic acid is the most one dimensional approach and that's not really what I'm going for.

Adding acidulated malt - This is a step up from adding lactic acid in my mind. Maybe not a considerable step but I think there are some important differences. Although Weyermann doesn't give the details on their website, I believe the lactic acid character in acidulated malt is achieved by spraying the malt with lactic-fermented wort. Whatever the method, it is derived from natural lactic acid production by bacteria, meaning that any 'impurities' (other flavor compounds one might get from lactic acid bacteria) would also make their way onto the malt. Some of these may volatilize off in the boil, but it is still less pure than lactic acid. For simple tartness I lean this way as it doesn't take any extra time and requires only a minor amount of extra work over adding pure lactic acid (though I suppose you do lose a bit of control). Sourness form acidulated malt is pretty one dimensional but for achieving mild tartness I find it clean and pleasant.

Although I may add up toward about 10% (by weight) acidulated malt into a batch, I usually don't add more than about 6-8 oz (170-227 g) into a main mash for ~5 gallons/19L. I'll do my mash with this first bit of the acidulated malt and then add the remainder with about 15 minutes left in my mash when the bulk of my conversion is done so that I don't alter the pH drastically and affect conversion for my whole batch. With my water as it is and the salt additions I usually do, the first portion brings my pH to around 5.2 in a pale grist. I haven't measured pH after I add the second portion so I don't know if it would really affect conversion, but the method I use seems to work well for me. I find that I get fine conversion on the second portion added (I usually don't mash out hot enough to denature enzymes so the acidulated is converting for 15 minutes and then through my whole lauter and sparge). Adding 7-9% acidulated by weight seems to give some mild tartness, but not to the degree or complexity as one may achieve from the next two methods. Even so, this is the normal go to method I use for many beers at this point.

Sour Mashing - I've tried this approach and I liked in in the recipe for my saison named Soma and also another saison. The approach I took is detailed in the Soma recipe. Basically I did a small stovetop mash a day or two before brew day and then incubated it at 100-120 F (37.8-48.9 C) until I was running off my main mash, at which point I blended the sour portion back in. It is very important to keep out O2 in a sour mash, and dropping the initial pH a bit with acidulated malt and/or lactic acid helps select for the bacteria that you want. Sour mashing can give you the most complex flavor profile but that isn't always a good thing. It is the least controlled of these methods and the most difficult to do repeatably.

The remaining sour wort portion after most has been added to the kettle
'Sour worting'  - I first heard this term from the Mad Fermentationist (there's some info from him here and here). It is sort of taking an approach that one might find in Berliner weisse brewing process where pure lactic acid bacteria are added to wort without any Saccharomyces (or any type of yeast for that matter). From this point when the fermenting wort reaches the desired pH the wort can either be re-boiled, killing off the bacteria, or yeast can be added. This approach with blending back the souring portion into a boiling wort allows the most control as pH can readily be monitored and the blend volumes can be controlled well to lead to the beer you want. Blending in the boil also allows independent control of hoppyness (same for the above methods) as the souring is done, the bacteria are killed off and hops can be added to whatever degree you like (it is slightly more complicated than this, but I'll get to that later). It also has the added benefit of allowing you to leave a bit behind in a carboy which you can later top up with cooled wort, giving you a head start for a 'live' sour beer.

When I've taken this approach (for example in this saison) I made a bit of extra unhopped wort from a beer with a similar grist and pulled it off before hopping it. Then I pitched the lacto and waited until it was around where I wanted it before brewing the beer it would be blended into. This takes the luxury of a flexible brewing schedule, but if you are less flexible you can always wait longer and let it get more sour than you want and then use less of the sour wort to a similar final result.

Alright, so there's a quick rundown of approaches for adding acidity to a beer before a primary/yeast fermentation. When I get back from work at sea I'll write up my experience so far with the sour worting approach and get to work with some more trials.

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