Lag time for Kale-Kohlrabi-Napa Cabbage Kimchi

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Lag time for Kale-Kohlrabi-Napa Cabbage Kimchi

Postby dciolek on Mon Jun 11, 2018 6:49 pm

I am 56 hours into my first Kimchi ferment, and am noting that the behavior is quite different than most of my sauerkraut ferments to date. Wondering if a LONG lag time before the LAB activity kicks in (at room temps) is typical (like 30 hours).

Recipe was combined from a two different ones I found for the type:

Spicy Kale-Kohlrabi-Napa Cabbage Kimchi

1 lb kale, fresh from garden
1 ea lemon, juiced
1 tbsp raw local honey
1 inch ginger root, minced
2 tbsp sesame seeds
1 tbsp olive oil
4 tbsp rice flour
8 cloves garlic
1 ea onion, diced
1 tbsp fish sauce
1 tbsp bhut jolokia hot chili powder
3 tbsp ancho chili powder
3 ea kohlrabi, diced
1 ea carrot
1 ea leek, sliced thin
1 head napa cabbage, large, shredded
2 tbsp kosher salt, add to taste (prob 3-4 total)
1 bunch scallions (mostly whites not stems)

Based on estimated weights of the salt and vegetables -- I think this ended up somewhere between 2-3% which seems typical for Kimchi.

But I was wondering if adding the lemon juice at the beginning dropped the pH pretty heavily at first -- and then had the effect of it rising for the first 30 hours. The attached graph shows that it pretty dramatically dropped once the LABs took over the ferment -- going from ~4.8 to ~4.2 in the next ten hours at average temps around 67.

First question -- is this long lag typical (if Kimchi is made from the raw veggies only with no starter). Second -- I put the Kimchi in an insulated cooler with a little ice, but at 4.1 pH now -- I am thinking it needs to be jarred and stuffed in a 37 degree fridge rather than letting it continue. Third -- is adding olive oil really a good idea preferement?

Any advice? I have read that tasting it at the beginning of the ferment (when raw) and after it is done (fully fermented) are fine -- but that in the middle might not be as pleasant. Will taste anyway! :)

The attached graph is from data points taken via a Raspberry Pi with ambient temp, ferment temp and pH sensors logging every 15 minutes.
Kimchi Ferment - pH and Temp vs. Elapsed Time.jpg
Kimchi Ferment - pH and Temp vs. Elapsed Time.jpg (56.9 KiB) Viewed 233 times
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Re: Lag time for Kale-Kohlrabi-Napa Cabbage Kimchi

Postby dciolek on Tue Jun 12, 2018 5:44 am

The batch was jarred, filling 3 quarts and 1 pint. After placing in the fridge overnight -- ferment is at 42 degrees now and the pH has dropped to 3.67.

This is well below the target ranges I have seen for kimchi, so it seems it may end up too sour by the time everything settles down.

Maybe the idea is to get it in the fridge as soon as the pH starts to turn (after the lag period) so the full length of the ferment can happen much slower. Or maybe lose the lemon juice from the recipe so there is no other source of acid (citric vs. lactic) in the starting conditions?

I have seen the suggestion to use overly sour Kimchi to make a Korean stew called Kimchi Jjigae, so all is certainly not lost. It was certainly tasty and a bit effervescent when testing -- but pretty tart, which I don't mind at all.
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Re: Lag time for Kale-Kohlrabi-Napa Cabbage Kimchi

Postby Christopher Weeks on Tue Jun 12, 2018 7:23 am

First of all, your data collection system is really neat. I should look into setting something like that up to play with.

I've never measured my pH, but I doubt that "too sour" is even a thing. And if you like the flavor as it is, I'm not sure what you even mean with the phrase.

I typically measure my kimchi fermentation times in weeks and months, not hours. I don't consider kimchi interesting to eat for three weeks and sometimes I leave it a year for extra funk. I don't know about the pH rise in the first 30 hours -- does the citric acid transform into other compounds over time? But I don't typically see much happening in that time period -- I think that's just the colony of microorganisms reproducing explosively before it really gets to work.

I have never made kimchi with any of: lemon, honey, oil. Each of those seems like they could play some role in altering the mixed culture's behavior and timing.

Is your mix incredibly spicy? I haven't used bhut jolokia but I have the sense that it's just insanely hot and a 1T seems like a lot for a relatively small batch. But maybe I just don't know.

Did you brine and drain the veggies and then coat with porridge? Or some other technique?

If you're new to kimchi, I'd suggest picking a simple recipe and making a learning batch. Anticipate keeping it in the kitchen for six weeks and taste it every two or three days just to learn about the changing flavor profile.
Christopher Weeks
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Re: Lag time for Kale-Kohlrabi-Napa Cabbage Kimchi

Postby dciolek on Tue Jun 12, 2018 10:00 pm

Thanks -- I'll put some details up on another post re: the Raspberry Pi system with probes that collects the data.

But you bring up a good point -- all the data and all the science on what pH is ideal for Kimchi doesn't put proper boundaries around what is pleasing to your personal palette. Thanks for the reset. :)

Maybe the next batch I will leave at room temp for a lot longer just to see the difference in progression and flavor development. Maybe most of the articles I was reading which had target ranges in 4.0 to 4.2 range were designed for commercial products that need to be more standardized for a wider range of palettes. Dunno -- my first batch...

I am also going to eliminate the lemon, honey and oil. No need to have these playing a role in starting conditions or fermentation speed. Nature pretty much knows what it is doing, so why go around it?

Strangely -- the mix did not turn out incredibly spicy. It ended up 3.5 quarts finished -- so maybe had a teaspoon per quart. I think the powder is a couple years old -- so probably lost some strength. Nicely spicy in the kimchi, not overpowering.

I first bruised the kale and minced the kohlrabi, then let that marinate with the lemon and salt and oil for a bit to let that work on the kale's waxy coating, then drained the extra liquid. I then added the shredded napa cabbage and the gelatinated rice flour mix and the rest of the goodies and mixed well by hand before putting it in a shallow plastic tupperware for the initial ferment. Lots of surface area, covered in plastic.

I think I will also test the next batch using some innoculation from this batch to see if it kick starts faster. A rising pH and a long lag time at room temperature doesn't sound like an ideal environment unless the salt level is relatively high (and certain).
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