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Comment by 4ad | Hacker News Reader

Article claims this fridge is colder than a regular one "to facilitate fermentation", but this doesn't make any sense. Fermentation is completely stopped in a regular fridge, you need higher temperature for fermentation.

Also this is not corroborated by any of the references in the article, which make no such claims about temperature. I am sure there are interesting reasons why one might want such a dedicated fridge, but the wikipedia article doesn't elucidate this mystery. The wikipedia article is basically garbage.

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IIRC this is actually the main purpose of one of these, they run slightly warmer to keep fermentation going while still being cold enough to preserve. Traditonal kimchi was stored underground so maybe a temp close to those conditions.

That makes it warmer than regular fridges, while wikipedia claims the opposite.

Not really, the advertised temperatures of most brands' kimchi fridges[1] are -1°C (with lower -0.5°C band of stability as well), which is supposed to be mimicking "buried outside in Korean winters" condition.

[1] Example here https://www.lge.co.kr/support/product-manuals?title=manual&m..., see table on page 10, it's between -0.7°C and -1.7°C for kimchi.

I think a better expression would be "to regulate fermentation." Kimchi lasts quite a bit longer when stored in kimchi fridge, because (I assume) fermentation almost stops, due to consistently low temperature. But obviously you don't want it to freeze (frozen kimchi tastes absolutely terrible), so the fridge must stay just above the freezing temperature, for it to work well.

And in my experience, every kimchi eventually goes sour in regular fridge (or even in a special kimchi fridge, if you keep it long enough), so I don't think fermentation completely stops at those temperatures.

Of course when it's going sour it almost becomes a different food and entirely different recipes open up (like Kimchi Jjigae, Budae Jjigae, or basically anything with stir fried pork).

Maybe it should say something like: to assist in halting the fermentation process, which otherwise could cause the Kimchi to spoil.

Assuming that’s correct, I’m no Kimchi Engineer.

I like to eat my kimchi at room temperature, so I tend to keep a small amount out of the fridge ready for my next session.

Yeah, if you read the Korean language article[0] (or the Namu.wiki article[1]), they both refer it the function as preserving and storing kimchi, not really going for further fermenting. Most folks I know buy prepared kimchi and use the fridge to store / have it last a while (as well as using it as a secondary fridge). Given that optimal kimchi ripening goes from 2d to 35d changing the temperature from 20°C to 4°C[2], I suspect it would take an enormous time trying to ripen it purely in the -1°C fridge (typical kimchi fridge temperature).

[0] https://ko.wikipedia.org/wiki/%EA%B9%80%EC%B9%98%EB%83%89%EC... [1] https://namu.wiki/w/%EA%B9%80%EC%B9%98%EB%83%89%EC%9E%A5%EA%... [2] https://ift.onlinelibrary.wiley.com/doi/abs/10.1111/1750-384...

> Fermentation is completely stopped in a regular fridge, you need higher temperature for fermentation.

My understanding as a hobbyist brewer and fermenter is that this is not true. Fermentation is greatly slowed at lower temperatures, but you should have things happening above freezing. Lager beers, for example, go from pure sugar to beer at 35F. And kimchi matures at fridge temperatures in ways that I'm pretty sure are caused by fermentation.

A short and dubious description I've read on a magazine article decades ago claimed that these have a temperature profile to go between heating and cooling for desired effects over time, by the tone in scale of weeks to months. I don't know how or what they do with Kimchi in Korea but there are probably lots of obviouses around it that needs context to realize.

https://en.wikipedia.org/wiki/Onggi

They sit outside year round.

Yeah, you're right.

A kimchi fridge I've owned had a temperature dial with a little chart next to it, that if I recall advised around 1-4C for halting fermentation for long-term storage and around 11 or above for active fermentation, and encouraged being mindful of the stage in your kimchi's, uh, lifecycle.

Pretty interesting to find a flat-out-wrong Wikipedia article in this day and age!

Thanks, that is interesting to know. I don't like kimchi (it's just worse sauerkraut) but I ferment other things and I always wanted a fridge just for that. I didn't know these things existed.

Can't you just leave it outside to ferment, then bring it into the fridge to halt?

Not really, no. The microbial culture composition is strongly dependent on temperature. Yeast prefers high temperature while bacteria in general prefers a lower temperature. Each specific thing you ferment has an optimal fermentation temperature. Plus there are other temperature effects unrelated to the culture itself. For example, enzymatic activity, which is also dependent on temperature, might destroy whatever you are trying to ferment before it ferments enough.

In practice, you will get a poor result if you ferment at high temperature. Texture goes off first, but you can also get weird alcohols or formaldehyde forming.

From my experience, the lower the temperature (and the slower the fermentation), the more complex the flavor. This rule seems to hold for almost everything, from vegetables, to kombucha, to bread, etc. For beer, it depends what kind of beer you like. You can get very funky beers at high temperatures.

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