I'm doing my first sour batch this weekend (plan on pitching Roselare in the primary) and had a quick question about the airlock. Specifically, do I leave it in the whole time? My initial research has come up with many references to the little beasts liking oxygen... so should I be letting some in, or is the head space enough to keep them happy for a year or so of fermenting and aging? Also, do I rack to a secondary? Or would that eff up the pellicle? Thanks!
If doing a Flanders style ale then it goes into the secondary. If you leave it with too much oxygen you run a big risk of producing a ton of acetic acid and therefore turning it into vinegar. Brett likes O2, but pedio can die from too much O2 exposure and Lacto D reproduces with or without the presence of O2.
keep the o2 to a minimum, there are other things than vinegar that are produced in the presence of oxygen and they are far worse (ethyl acetate)
tough balance as the different bugs like different things. one way to deal with it is to add brett first when theres oxygen and then add your other bacteria later. although that does cost more money. if you're going to be pitching the roselare then i would say just pitch it and let it go. if you ever add any fruit/oak/etc...you'll get a little oxygen in then as well. don't worry about the pellicle, its mostly a sign that theres oxygen in the carboy. and even if it gets messed up it will come back and the beer will keep working. also, be patient. i'm 7 months into a sour and while its got an extremely sour smell, the taste is mostly tart at this point. i'm really not sure what its going to take to get it to that really sour point...maybe just more time.
I have a Flanders Red that I let age 9 months on Roselaire and dregs from a La Roja bottle then transferred onto 4lbs of tart cherries for another 9 months. Aside from the transfer the beer was constantly under an airlock. Just tasted it last week and it's pretty damn good and tart. No off-flavors or aroma.
awesome, thanks for the pointers guys! two more question: i'm going to be using a glass carboy because that's what i have, so: 1) should i be keeping the beer out of direct light since the UV effect has way more time to set in? 2) say i did a 9 month primary and a 9 month secondary.. would bourbon (or maybe even red wine?) soaked oak chips in the secondary be a good substitute? thanks again!
1) I keep my Lambic in the garage with a t-shirt over it so that any light doesn't get to the beer since it will still skunk the hops. 2) Red Wine soaked French Oak plays very nice with the sour beers, just don't add too much at first. You can't take oak flavor out, but if it isn't oaky enough for your palate, you can always add more when you get closer to bottling.
The higher the temperature, the more the souring bugs are active, the lower, the more refined the balance. There is a reason the Lambic and Flanders brewers brew in the Fall and Spring to avoid the heat. It will see the heat of Summer in a few months and with that heat the Pedio will more than likely kick up and sour the beer some more, as will the Brett in funkdifying it. Then again, mine is a spontaneous fermentation and I didn't use commercial bugs, so who knows what will happen with mine
They most certainly are temp sensitive. I have a flanders red going right now with Roselare Yeast. It has been going for 4 months with very little activity. Now that it is getting warmer and the inside of my house is over 65 the bugs have become activated again. A nice pellicle has begun to form on top of the beer that was not present at first. I think it has got to be the increase in temp that is doing that.
From what I understand the souring bugs like very little oxygen, like the amount that can seep through barrel staves over the aging process. I had a friend let his air locks run dry on a few of his sours and they progressed way too quickly. There is a specific bug that begins with an A (can't remember the name) that takes over with too much oxygen and will provide the vinegar characteristics. I use plastic buckets with a spigot so that I can sample without disturbing the yeast cake and supposedly a little oxygen can seep through. The other thought would be not racking the beer to secondary. They bugs will feed off the dead sach cells. I have done this a few times with no adverse affects (cantillon style). The bugs are temp sensitive but in a good way, with slow controlled temps wings the yeast will develop fully.
I think you are referring to acetic acid which is a by product of some of the bugs when they get too much oxygen.
Found it: acetobacters which produces acetic acid or is in the same family but produces vinegar flavors.
Just to clarify, acetic acid is vinegar. Most of the proper bugs, brett, lacto and pedio, are anaerobic and thus do not need oxygen for metabolism. Acetobacter is aerobic, and by limiting oxygen (no splashing during racking, always keep airlocks topped up with water, etc), you'll prevent acetobacter from becoming dominant.
