Friday, August 19, 2011

A Yeast Starter w/o Yeast?

I am preparing to make a beer in 3 weeks that will not have yeast added to it for fermentation... well, not directly; I will be adding fruit directly to the unfermented wort to do what is called a Spontaneous Fermentation. Spontaneous fermentation is used in Belgium to make Lambics; the hot wort is pumped into a cool ship (a flat, shallow steel container with no lid) that sits high in a pathway for good night time breezes and awaits the breeze to bring local microflora: wild yeasts, and beer souring bacteria. After a night of cooling and being innoculated with these wild strains, it is transfered into a wooden barrel that is home to wild yeasts and bacterias, and it ferments here for years.

I will be doing something like this, but not quite. The wild yeasts and bacteria that are in the air used by Lambic brewers are mostly from fruit. Fruit have all the organisms needed to make a wild ale: Saccharomyces, Lactobiccilus, Pediococcus, and Brettanomyces. My plan is to add the fruit with these microflora on them directly to the beer and allow the resident critters to do what they naturally do. The fruits contain sugars that will be eaten and increase the alcohol in the beer as well as helping to dry it out, and they contain acids that will help add another layer of sourness to the finished product. I am going to use blackberries and peaches, the blackberries will give a nice acidic and fruitiness, and the peaches will have a large amount of Brett living on the fuzzy skins. I also will be adding French Oak cubes to primary to add some more depth, as well as any microflora living in the wood.

One huge risk I run by doing this is if there is too much oxygen, acetobacterer can grow which can turn the beer to vinegar. So to avoid a slow start to fermentation, I am taking a precaution. I am making starters from the fruit, that I will pitch along with more fruit when it comes time to ferment. So far I have made the starter wort: 200ml Simply Apple Juice and 800ml of water, to 50 grams of light DME, boiled with yeast nutrients. To this I added 15-20 fresh blackberries from my neighbor's bush. It has been 4 days, and it has hit high krausen, has a substantial amount of yeast on the bottom, and is forming a pellicle. It tastes great. Lots of fruit, light alcohol, clean sourness that is more than straight tart blackberry. Here is a progression:
12 Hours - Some signs of growth as the slurry on the bottom is larger than before.

24 hours - the blackberries are starting to float around a bit, and there is quite a bit of yeast (I assume) on the berries on the cores.

36 hours - many of them floating on top and what appears to be fermentation signs on the top. Progressing nicely.

44 hours - definite signs of a good fermentation.

48 hours - krausen has formed, and smells of fermentation.

84 hours - fermentation seems about done, there is a substantial amount of yeast on the bottom, and I see signs of a pellicle forming on top.

I will be updating again soon as I do the starter for the peaches (the Farmer's Market was sold out the other day, hoping to get some tomorrow morning), and again as I step them up, and of course, brew day!

NOTE: This beer took 1st place in Sour Beers and BEST OF SHOW in February 2014 at the KLCC BJCP comp.

No comments:

Post a Comment