im planning on using glass demi johns, its probably not worth while at all, but I dont want to wait 2 year to find I should have done it.
So I think ive found a solution, Ive found 2 co2 bottles from my old plastic barrels, so they should do the job.
Check out this link, which includes the section below:
MANAGING OXYGEN EXPOSURE
Oxygen plays a dual role in sour beer fermentations, both as a vital requirement for healthy Saccharomyces and Brettanomyces growth, as well as a potential source of off-flavors. This duality leaves us wanting to optimize oxygen exposure at differing times in a sour beer’s life cycle. Here are some general guidelines regarding oxygen:
- We want thorough wort oxygenation at the early stage of active Saccharomyces or Brettanomyces fermentation. This is vital to cell growth and appropriate levels of cell growth help to develop the fermentation characteristics we are looking for while avoiding off-flavors.
- We want very low, yet present, exposure (micro-oxygenation) during Brettanomyces aging. Unlike Saccharomyces, Brettanomyces cannot actually ferment sugars into ethanol in a completely oxygen free environment. This curiosity, known as the Negative Pasteur Effect, is the reason why these yeasts thrive in oak barrels, an environment that continually allows them access to low levels of oxygen. This is not to discourage the use of carboys or conical fermenters for Brettanomyces aging. In practical applications, it is nearly impossible to create an aging environment so oxygen-free that Brettanomyces can no longer ferment.
- After a beer has matured, or is ready to be packaged, we want to eliminate all oxygen exposure if possible. At this point, oxygen can increase acetic acid production or create staling of malt or hop compounds.
At the beginning of active fermentation, sour beer wort should be oxygenated using the same practices employed for clean beer fermentation. While many homebrewers aerate their wort via shaking or a sintered air-stone, I prefer to employ a small oxygen tank and a sintered stone while swirling the wort for about 1 minute. For even more repeatable results, an oxygen flow meter can be combined with a sintered stone or in-line oxygenation during wort transfer. This last practice is the standard used by professional brewers. Professional brewers may also measure the oxygenation of wort at the beginning of fermentation with a dissolved oxygen (DO) meter. In my opinion, such a meter would be cost-prohibitive and unnecessary for homebrewers.
Regardless of the choice of vessel, minimization of oxygen exposure should be the goal during a sour beer’s aging. When using carboys, this means that after any sampling the headspace should be purged with CO2. When aging in barrels, sampling is typically done via a small “Vinnie” nail installed into the head of the barrel. Professional brewers tend to be split into two camps in regards to whether or not to top-off a barrel after months of aging (beer volume will be naturally lost to evaporation through barrel walls). I have no personal experience with the issue, but can say that I’ve had excellent beers from different breweries using both methods as well as overly acetic beers from breweries using both methods. I therefore tend to believe that topping-off a barrel or not topping it off has much less of an effect than factors such as barrel wall thickness, strain selection, and sampling methods. Regardless of vessel choice, remember to regularly top-off any airlocks (if used). In my experience, a dried up airlock is surely a sign that the beer within has become too acetic (vinegary).
For homebrewers, Cornelius Kegs make an excellent choice for aging sour beer. These vessels can maintain a very low oxygen environment, offer easy sampling, and can be used to ferment under mild pressure which may help to encourage or subdue fermentation character depending upon the microbes employed.