Ancient Sauerkraut

You may remember when I embarked on my lactic acid fermentation, back in September 2014. Soon after the kraut was sufficiently sour for my taste (a month-ish), we binged on sausages and kraut for quite some time. I even bought a new head of cabbage, and back-sloshed a new batch of sauerkraut with the old culture. Well, it was technically back-sloshing, in the most basic sense of the term.

Back-sloshing is where you take some of the juice from your old culture and put it into a new culture. This speeds up the fermentation process, and produces a much more sour product. But instead of a dilution of 1:10 or anything like that, I just ate most of the sauerkraut out of the old culture, shredded up some more cabbage, and stuffed that into the same jar. The culture was technically diluted by the juice of the new cabbage, but that’s it. This back-sloshed kraut turned out super delicious, so we ate up most of that pretty quickly as well.

But then, I guess we stopped eating at home as much or something, and the last little bit of Kraut was forgotten about and abandoned in the jar. And yet, I still thought it could be more sour, so I refused to move the kraut to the fridge. I left it in the cupboard until today. So, about 5 months. I finally decided to crack it open and finish it off today because Doc bought some sausages. I was a bit curious, and a bit hesitant, about this culture I dubbed “The Ancient Sauerkraut.”

There was a huge film of beige sum on the top and on the bottom of the culture. But no mold, it looked like it was all just dead bacteria, so that was promising. Loads of dead bacteria. When I opened the lid of the jar, carbon dioxide bubbles burst to life, like they would when opening a beer. This surprised me, as I kept the water trap installed on the jar for the full 5 months, so I had assumed that any carbon dioxide would have escaped. But maybe the trap got jammed or gummed up with something? I guess it was a good thing I opened the Ancient Kraut now, before more pressure built up inside it.

And then, there was the flavor. The flavor had transformed more in those 5 months than I would have imagined (based on the trajectory of flavor changes that I tasted over the course of a month or so). There were so many intensely fruity, light, complex flavors going on in that ancient kraut. I’m assuming these were the esters that I’d read can be produced in late-stage lactic acid fermentation. The kraut really wasn’t even all that sour anymore – or at least, that wasn’t the main taste. The flavor really blew me away; the Ancient Kraut was the most amazing, complex, and delicious sauerkraut I had ever tasted. Of course I’m keeping the juice, to back slosh some cultures in the future.

The Ancient Brussels Sprouts and Carrots. Note the film of bacteria on the top and on the bottom of the culture.

And guess what? I also some some 5-month-old Ancient Brussels Sprouts and Carrots. Since the brussels sprouts had a high sulfur content, I had always found the fermented brussels sprouts’ flavor a bit more objectionable (and stanky) than the kraut, but now I am curious to see if they have been similarly transformed.

Lactic Acid Fermentation Bacteria: Under the Scope

The little guys chowing down on my cabbage to make sauerkraut
The little guys chowing down on my cabbage to make sauerkraut. I made this GIF from microscope images of my fermentation.

Well, I got a chance to peek at the bacteria in my sauerkraut and sauerprouts jars! Just as I had expected, the kraut juice had a MUCH higher cell density than the sprouts. The sprout juice was like a desolate wasteland. I guess that’s the problem with putting whole sprouts in without chopping them… not enough sugars from the vegetables escape into the juice to feed the microbes. Looks like it might mostly be Lactobacillus bulgaricus and Leuconostoc mesenteroides in there.


Lactic Acid Fermentation at Home

My homemade sauerkraut in progress. Mmm-boy, look how turbid that brine is! Those bacteria are really going to town. There are also tons of CO2 bubbles constantly forming in this one (which you can’t really see from the photo)

I’ve been fermenting a batch of cabbage to make sauerkraut, as well as a batch of Brussels sprouts to make (wait for it)… fermented Brussels sprouts. Yea, turns out there is not a special name for this delicacy.

It has been 3 weeks of fermentation for these jars, and we tasted them for the first time last night. I really liked the Brussels sprouts, they were getting soft and sour and everything I had hoped for. Doc didn’t like the Brussels sprouts, he liked the sauerkraut better. I thought the sauerkraut was OK, but not nearly as far along as I would like. It was only slightly sour and still very crunchy and salty. Over time, as the juices get pulled out of the plant tissues, the culture gets less salty-tasting and the plant tissues get less crunchy. So salty saurkraut is often a sign of not-finished sauerkraut. I’m reserving judgment on the saurkraut for a few more weeks.

Fermenting Brussels sprouts. Note the brine-filled sandwich bag I use as a weight to keep all the vegetables submerged. It is filled with brine in case it leaks. These have been fermenting more slowly, and with fewer CO2 bubbles, due to their not being shredded. But I tasted one yesterday and they are definitely getting sour and tender. Also notice how much less turbid the brine is here. Must be a lot less bacteria.

Unlike homemade yogurt, where you pretty much have to add a starter culture (ie: mix in a little bit of already-made-yogurt into your milk), the process of fermenting vegetables feels way cooler because the lactic acid bacteria are commensurate with the vegetables, and are already hanging out on their surface. Waiting. All you do is make a super salty brine, plop your vegetables into the brine, and let the bacteria have at it for about four weeks (whenever you enjoy the taste, just move the jar to your fridge to slow/stop the fermentation – the longer the bacteria ferment, the more sour the vegetables will get).

The main purpose of the brine is to suck the juices out of the vegetable tissues via diffusion. Basically, the brine is way saltier than the inside of the cabbage cells, which are housed in semi permeable membranes, and so the liquids get sucked out through the membrane as the outside and inside approach an equal ion concentration. And then your bacteria buddies go to town. It also happens that many of the lactic acid bacteria are halotolerant (salt-tolerant), so the brine also gives you the added benefit of inhibiting the growth of many pathogens and other agents of spoilage, whilst not hurting the lactic acid bacteria. Note that the lactic acid bacteria are not usually halophilic (halophilic organisms need high salt to live), so it is possible to ferment things without a brine (consider, if you will, sour beers and yogurts which are not salty), but you would run a high risk of spoilage.

The lactic acid bacteria are non-respiring, which means that all they can do is ferment. Technically they are aerotolerant anaerobes, which means that oxygen does not kill them or harm them, but they don’t use the oxygen in any way. They don’t even notice the oxygen (or lack thereof). Since fermentation yields a lot less energy than respiration (which doesn’t always require oxygen, but let’s assume for simplicity’s sake that it does; especially since we are not likely to have loads of metals in our brine), fermenters can easily get out-competed in aerobic environments by oxygen respirers.

So, to give my bacterial buddies a leg up on the competition, I sealed off the jars and put a vent system in with a water trap. Fermentation produces CO2, you see, and I didn’t want the jars to build up pressure to the point of explosion. I want to eat the sauerkraut, not blow up my kitchen with it. With this set-up, CO2 can leave through the vent, but no new oxygen can get in. This means, once the undesirable aerobic bacteria use up the tiny bit of oxygen left in the jar, they won’t be able to do anything else. They’d have to either switch to fermentation themselves (in the case of facultative anaerobes – bacteria that will use oxygen if present but will switch to fermentation in its absence), or sporulate to wait around for more oxygen, or just die. And there will be no more respiration out-competing fermentation.

Lactic acid bacteria are a diverse bunch, spanning several genera and many of the species do slightly different things. They all ferment the sugars from the vegetable tissues, but some only make lactic acid, while other species might make other compounds in addition to lactic acid. You can even get esters and other weird things produced if you let the culture go on long enough, which can really contribute to a unique flavor.

Supposedly the most common player in fermented vegetables is Lactobacillus plantarum, but I will attempt to identify the bacteria I have growing in my fermentation jars. Will they be monocultures? Will they be mind-bogglingly diverse? Will the Brussels sprouts have a completely different community compared to the cabbage? Obviously, different strains will be dominant at different stages in the fermentation.

Stay tuned! I will share all of my results, and even some super awesome photos of the bacteria growing in my fermentation jars – taken with a microscope. Will they be coccoid? Bacilloid? Spirilloid? Probably not spirilloid, but still. WILL THEY BE ALL OF THE ABOVE? How will you handle the suspense?