Originally published on NourishingTreasures.com in 2012.
After completing Sauerkraut Survivor, I knew there was more I wanted to find out about fermenting jars. When I opened the Fido I was impressed with the amount of CO2 it holds (it was bubbling for minutes after I opened it, as you can see on this YouTube video I made). I had to do more experimenting.
In particular, I wanted to know: since the Fido has the advantage of holding in more CO2 than other airlock systems – could that be an advantage that would perhaps allow the sauerkraut to be spoilage-free with no weight at all? It can be difficult to find something that keeps those floaters down – and floaters seem to attract spoilage. It would be handy to not need a weight.
The Test
On July 8th, I filled a 1/2 liter Fido jar with salted cabbage (to make sauerkraut) – with no weight or even a cabbage leaf – and let it sit on my counter for four weeks.
At the same time I filled a 1 liter Fido jar the same – only I used the food-safe dehydrator screen as a weight so there was no cabbage floating. I love how clear the brine is with these screens!
The Results
On August 10th (yup, two days past 8/8) I opened them. All month long I was checking them for spoilage, seeing none, but I knew the big test would be checking the brine under my microscope. Sometimes the ferment can be visually spoil-free, and yet have traces of mold or yeast in the brine once you look at it under the ‘scope.
The photo above [not here] is the 1/2 liter Fido opened after 4 weeks. You can see the cabbage is clear out of the brine – we’re talking more than just floaters! If there was ever a set-up that would attract mold, this is it.
And yet, there was no spoilage!
This wasn’t even the freshest cabbage I could have used. You can see there isn’t much green in my ‘kraut. I used up the last two heads that were left over from Sauerkraut Survivor, and had to shed the outer wilted leaves to the point not much green made it.
And still, no spoilage!
Beyond there not being spoilage, the LABs were thriving like crazy. They love the protection the extra CO2 gives.
The difference between the Fido airlock and other airlock systems
The difference between the built-in airlock the Fido jar has and other airlock systems is this: your typical 3-piece airlock (like this one) airlock is installed on the top and filled with a small amount of water. The water acts as a barrier to prevent oxygen from getting to your ferment. At the same time, it allows the CO2 to escape through the water barrier. Any amount of CO2 pressure can work its way right out with very low resistance.
Similarly, the Fido’s vulcanized rubber gasket is an airlock. It keeps the oxygen out, while allowing CO2 to escape. The difference, though, is this: the CO2 needs to build up more pressure before the lid is lifted and the CO2 escapes between the rubber gasket and the glass rim. This allows for a certain amount of CO2, which is produced by the lactic acid bacteria, to stay inside the jar, acting as a blanket of protection.
Once you open the jar, you will hear the pleasant “pop” sound – you know you did it right :)
Fido jars defying science?
So can Fido jars really defy science? It seems so. From everything I have read, and experienced, you really do need a brine covering to prevent spoilage. Low brine levels caused several of the jars in my Sauerkraut Survivor series to spoil – and with good reason. As I explained in The Science Behind Sauerkraut Fermentation, moisture is one of the key elements in keeping spoilage at bay. Too low a water level will give oxygen-loving bacteria, yeasts, and mold the right environment to grow.
I encourage you to give Fido Fermenting a try! I was inspired to create a Facebook group for Fido Fermentation – feel free to join :)