I’m thinking mostly of turşu (torshi) and kimchi.
Traditionally, these vegetables are able to ferment fully sealed for weeks, months, or even years. My family ferments turşu for 6 weeks and they fill that bottle to the brim with no problem. But I have seen many reports of people doing European style fermentation who have popped lids and made a mess because they didn’t “burp” the jar.
So what is the difference that makes them not need to release pressure? Can they be made in a metal lid mason jar?
Also, there is vinegar in turşu solution - anywhere from 10% to 50% volume depending on the recipe. Some recipes boil the solution before adding to the jar. I have read many people say both vinegar and boiling will kill your culture, but I have seen both done and they definitely work. Any insights on this?
If you can create a waterproof seal odds are it is not capable of venting. The vacuum created by a cooling liquid is going to be trivial compared to the amount of gas being produced by any fermentation process - for context a teaspoon of fermentable sugar in a 250ml mason jar would put the glass at risk of shattering, and at the very least cause it to gush foam when opened. Last time I did fermented chillies for hot sauce I put the lid on too tight and when I loosened the mason jar ring I filled my kitchen with aerosolized scorpion pepper pulp, 0/10 would not recommend. Also note that fermenting in a sealed container is very dangerous - if too much pressure builds, handling the glass can cause it to explode and you could lose a hand
Vegetables will naturally off-gas with age, which may be what is causing the mild amount of pressure build up you are describing? This is decomposition, not fermentation
I haven't heard anything about chickpeas absorbing carbon dioxide - I know chick pea water is viscous and it may behave similarly to Irish moss/isenglass/agar/gelatin etc in that it acts as a fining agent - it binds to the vegetable proteins in solution and slowly settles to the bottom so all the cloudiness in the solution is concentrated into a thin layer on the bottom instead.
I'm not an expert on vegetable fermentation but I will say if you are adding near boiling water you are definitely killing 100% of the yeast and the majority of the lactobacillus - yeast will die between 40-60C and the more temperature tolerant lactobacillus species between 55-65C - I would look into getting a fermenting lid with a water filled air lock to visualize what is going on. During an active fermentation you should be able to see a near constant stream of bubbles floating up to the surface of the water.
Yes, they do bubble. And yes, the jar is watertight.
Let me share a couple of random English turşu recipes from a quick google search. You can see they all say to cap the bottle and put it away for days/weeks. No mention of burping even though these are all fermented. Only open when ready to eat.
https://hello-alanya.com/tursu-time/
https://fermentation.love/en/einfache-rezepte/karisik-tursu/
https://www.seriouseats.com/mixed-vegetable-pickles-recipe-7976002
This is exactly how my family does it, too. So how is it possible these don’t require burping? There is still some pressure build up, but certainly not nearly enough to break glass or pop a screw lid. I’m convinced I’ve misunderstood something.
@yoyolll @bjorney from what I understand, screw top jar lids like with Mason jars are a lot more airtight (and therefore more likely to explode) than twist-off lids, which are more common in Europe. With these the most extreme pressure can escape.
Probably depending on how tightly you close them.
@yoyolll @bjorney Jars with replaceable rubber seals are also not completely pressure resistant. The seal works like a gasket for extreme pressure, leaving moderately high pressure behind. I only use Weck jars now, because it works so well. (Will write a blog post soon…) Other brands are Le Parfait and so on. #fermentation
We do use those jars primarily - the ones with rubber seals. I was wondering if there’s some kind of positive pressure selectivity in this mechanism which would explain why it is watertight under most circumstances, especially at the start while the solution cools and creates negative pressure. If that’s the case, I should expect it to leak slowly if I left it upside down for a long period of time (not brave enough to try though).
I’m looking forward to your blog post.
@yoyolll @kimchiconcept which ones do you use, Weck or Le Parfait-style? Guess they both work great and it’s a matter of taste and if it’s easy to get them.
What do you mean by positive pressure selectivity?
Le Parfait style. It has a replaceable rubber seal.
I mean like the seal is not normally permeable, as evidenced by being watertight (for a period of time) even with some negative pressure inside the jar created by the cooling solution. However, once there is enough positive pressure from fermentation gasses inside the jar, it becomes permeable. In other words, it’s selectively permeable for positive pressure. I suppose that might be due to momentary one-way deformation of the rubber at a certain pressure which might be why you’re not supposed to reuse them for fermentation, and why it’s so important not to open the jar until it’s ready to be eaten. Basically, it might be acting as a very simple one-way airlock. But this is just a guess. And I am probably overthinking it.
@yoyolll @kimchiconcept
> it might be acting as a very simple one-way airlock
That’s what I think it does! If the pressure goes above a certain point, the rubber temporarily gives way. It never completely goes to normal, there’s always a higher pressure inside, once it has gone up. And this way all the oxygen gets displaced, so you end up with a protective atmosphere. At least for long enough until you want to open and eat what’s inside.