Acetobacter

San Miguel top-off

(Disclaimer: This post actually took place approx 3 months ago – Sept 2014)

 

The San Miguel top-off is not a newly formed, crazed sexual position, though it sounds like it could be fun. Rather, it is simply me, topping off the barrel with a bit more beer. This serves not only to add more complexity (hopefully) to the beer already in the barrel, but also replaces some of the beer lost to absorption from the wood, and evaporation. If exposed to copious amounts of oxygen, a bacteria known as Acetobacter can gain a strong foothold. Acetobacter turns alcohol into acetic acid in the presence of alcohol, and acetic acid is essentially vinegar. So, but reducing the headspace in the barrel by topping off with more beer, we are also limiting the effects of Acetobacter.

For this topping off, I have chosen to use a beer that I have been aging for approx a year now. It is a simple Farmhouse style ale that was soured with Lactobacillus bacteria, Lactobacillus brevis to be specific.

Here is the Recipe for that beer:

Recipe Specifications
--------------------------

Batch Size (fermenter): 4.00 gal   
Bottling Volume: 4.00 gal
Estimated OG: 1.048 SG
Estimated Color: 6.4 SRM
Estimated IBU: 6.3 IBUs


Ingredients:
------------
Amt                   Name                                     Type          #        %/IBU         
4 lbs 8.0 oz          Brewers Malt 6-Row (Briess) (1.8 SRM)    Grain         1        69.2 %        
1 lbs 8.0 oz          White Wheat Malt (2.4 SRM)               Grain         2        23.1 %        
8.0 oz                Caramunich I (Weyermann) (51.0 SRM)      Grain         3        7.7 %         
0.50 oz               Crystal [4.10 %] - First Wort 20.0 min   Hop           4        6.3 IBUs      
1.0 pkg               Farmhouse dregs (SN Ovila Saison)        Yeast         5        -                    
1.0 pkg               Lactobacillus Delbrueckii (Wyeast Labs # Yeast         6        -             


Mash Schedule: Evan's Step Mash - Light Body 
Total Grain Weight: 6 lbs 8.0 oz
----------------------------
Name              Description                                Step Temperat Step Time     
Protein           Add 6.50 qt of water at 140.1 F            131.0 F       30 min        
Beta- Sacch       Add 1.82 qt of water at 188.3 F            141.0 F       30 min        
Alpha - Sacch     Add 3.28 qt of water at 179.5 F            150.0 F       30 min        

Sparge: Batch sparge 







The beer was then aged for close to one year before I added it to the barrel. It had developed a nice, yet mellow sourness, a little surprising considering the amount of time it had had. Will be interesting to see how this changes the beer in the barrel. 
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