Quick question about the fermzilla. My father in law is keen for me to have a crack at mead. I was going to do the primary in a plastic bucket, then want to transfer for clearing/aging. How is the fermzilla for long term storage? Is there much risk of oxygen ingress over 6-12 months of aging? Or is it better to buy a glass carboy, recognising that their is no perfect answer, except maybe a keg, which I don't want to use?
PET that has no oxygen barrier is not designed for long term storage of beer as you get a small amount of oxygen ingress through the PET plastic wall. Dont get me wrong, PET is still a great O2 barrier and way better than PE, PP or other commonly used plastics. In fact it is orders of magnitude better than HDPE that many customers still use for fermenters. HDPE is like a sponge letting gas pass in both directions.
For Pilsners, NEIPA, or other light color and light flavored beers I would not put the beer into the fermenter for more than 2 months and I am confident you will get less than 1ppm ingress through the wall of a
30L all rounder.
For Ales, slightly darker beers you can allow your beer to sit in the fermenter for about 4 months and you will get about 2ppm ingress
For dark beers like stout, English ales, Triple, Porters you can store them in the Fermzilla for more than 12 months. At 12 months you will get 6ppm ingress but some of these dark beer styles are very robust to oxidation and even high exposure to oxygen might not be anywhere near as noticeable.
Some retailers sell the FermZilla products or other competing PET fermenters/kegs as suitable for long term storage but the reality is they are not. Also some customers think that if you positively pressurize the vessel it will not let oxygen through the wall of the vessel but this is also not true. Oxygen will permeate into the beverage even if the container is under pressure. Pressure doesn't solve this problem.
So really you have to look at your product and determine how oxygen sensitive is it. Is 1ppb the limit or 100ppm? I have limited understanding of Mead but to my understanding mead is much more tolerant to oxygen exposure than beer so I would have thought that even upto 10ppm or more would still have no noticeable effect on the flavor of mead but I am not an expert in mead.
The issue with corny kegs is the large lid o-ring. This large lid o-ring can also allow gas to permeate through this seal. We have been actively been doing some research on this exact topic and I think we will be making some improvement to
corny kegs to tackle this in the future.
Even with glass carboy I often see people use these thinking they have no oxygen ingress. The reality is that the glass is impermeable but the silicone bungs have high oxygen transmission rate making it even worse than the PET alternative. Some bung materials are way better and some are way worse but often when you purchase the bung insufficient information is supplied to determine what the material is and thus make it difficult to determine the oxygen transmission properties.
As you know we have these
8L PCO38 kegs where we use a blend of plastics to greatly increase the barrier properties and prevent oxygen ingress. Even with this product we do not recommend storage in this keg for more than 6 months.
After writing this post I really think more education is necessary on this topic and I think it might help if we do a video on topic as oxygen exposure is clearly becoming a more important subject especially as home brewers continually chase higher quality.
