My salt-free fermenting adventures started when I wanted to make a low sodium kimchi. After many failed attempts, I have a recipe that I really love using whey from plain yogurt to ferment the napa cabbage. It's a slower, cold ferment (to keep it crisp) so it takes about 8-10 days of fermenting, but there is no salt or fish sauce and an entire quart-sized jar comes in at just 70 mg of sodium.
Servings: Makes 1 quart Sodium: About 70 mg for the entire recipe (see Notes, below) Time: 45 minutes plus time for fermenting
1 pound napa cabbage
1/2 cup daikon or carrots, julienned
1/2 medium apple or Asian pear, chopped
1 inch ginger, peeled
10 cloves garlic, peeled
1/4 cup gochugaru
1 tablespoon white sugar
1/4 cup water
Pinch bonito flakes
2 tablespoons white vinegar, plus 2 additional tablespoons white vinegar, divided
2 tablespoons whey from yogurt
1) Strain yogurt for whey - I got the idea to use whey to ferment from this Spruce Eats article. To extract whey (the liquid) from yogurt, strain some plain yogurt over a fine mesh sieve lined with cheesecloth and let it sit overnight. If you scoop out your yogurt so that you create a little bit of a well, the whey will pool up and that part will be easy to filter. I do this a day or two before I'm planning to make the kimchi. I keep the strained yogurt and eat it just as you would normal yogurt, it's just a bit thicker now that you're strained some of the liquid out.
2) Dry the napa - this first step is optional, but I've found that drying out the napa improves the texture. Quarter the napa cabbage, and let it sit in the sun for a few hours until you can bend a leaf without it snapping. Traditional kimchi starts with salting the cabbage to draw the moisture out, so maybe drying it does something similar. This is how my mom makes pickled mustard greens so she suggested I try it and I do find it improves the texture and flavor.
3) Prepare the marinade - separate the green from the white parts of the scallions. Cut the green parts into 1-inch pieces, and chop the whites small. In a blender, combine the chopped apple, white parts of the scallion, ginger, garlic, gochugaru, sugar, water, and bonito flakes and blend until you have a chunky sauce. I've used fuji apples and Asian pear for the marinade.
4) Wash the cabbage and cut it into 1.5 inch pieces. Put the cut cabbage, green scallions, and daikon or carrots in a very large bowl and add the marinade. Toss to combine. I use plastic food gloves when I do this so I can really coat the leaves with the marinade.
5) Divide the cabbage mixture into two quart-sized glass jars. Add 1 tablespoon whey and 1 tablespoon white vinegar to each jar, cover, and refrigerate.
You can also use a bigger sized jar, but I do this because after the first or second day, the cabbage mixture will wilt down quite a bit and I'll combine them into 1 quart-sized mason jar. The pictures below are for a double batch (which is what I normally make), so there were 4 jars to start with. One the second day (middle picture) I combined them into 2 jars, and then put fermenting lids on the two jars (last photo). You don't have to have fermenting lids, but if you don't, leave about 2 inches at the top of the jar so the kimchi has room to ferment and burp the jar daily.
And then you wait. After the first or second day, the cabbage mix will wilt down and you can combine them into a single jar. I usually check and taste the kimchi starting at day 3 or 4 when I start seeing bubbles. By about day 8-10, the kimchi has developed the right flavors and I add 2 tablespoons of vinegar to the jar. Give it one more day and then it's ready to eat! Here's a video of the bubbling...
This kimchi is a work in progress but after many attempts I'm really happy with this recipe. In my test runs, I was inspired by recipes by Kimchimari, Insane in the Brine, and @rustic_koreankitchen on Instagram. Insane in the Brine has lots of tips about fermenting equipment. I tried fermenting at room temperature, but the kimchi came out incredibly mushy. I've also tried with just vinegar and without the whey, and even after a month just didn't get the deep, umami flavor you get by fermenting. When I taste the kimchi at around day 8-10, it's a bit sweet so that's why I add that additional 2 tablespoons of vinegar. If you prefer your kimchi less sweet, you can easily omit the sugar altogether, or if you want to tone down the vinegar, add just 1 additional tablespoon of vinegar per day and taste as you go. I'd say this kimchi is pretty mild, so add more gochugaru if you want something spicier. Still experimenting with different variations of this but it's a great start for salt-free kimchi!
Finally, a note on the sodium. My estimate of 70 mg includes everything that is added to the kimchi, but I really don't know how much sodium is actually in the kimchi that you end up eating versus what remains in the marinade. I also didn't use carrots because they're higher in sodium. The bottom line is if you ate the whole jar, it would be about 70 mg of sodium.