Home fermentation: sauerkraut, pickles and kombucha, done safely

Before refrigeration, fermentation was how a harvest lasted. Cabbage became sauerkraut or kimchi, cucumbers became pickles, milk became yogurt and cheese, and grains became sourdough and beer. Microbes turn sugars into acids, gases or alcohol, and the acid both preserves the food and changes its flavor and textureMarco 2017.

Today the interest is mostly in live microbes. A small Stanford trial found that eating more fermented foods raised gut microbe diversity and lowered inflammatory markers in healthy adults Wastyk 2021. It is one trial, so treat the health side as a pleasant possibility and the flavor as the sure thing. More on the evidence is on the fermented foods page.

This follows the National Center for Home Food Preservation method, adapted from the USDA Complete Guide to Home Canning Nchfp.

1. Use firm, fresh cabbage, ideally within a day or two of harvest. Work with about 5 pounds at a time.
2. Remove outer leaves, rinse, quarter, core and shred thinly.
3. In a clean crock or food-grade container, mix the cabbage with 3 tablespoons of canning or pickling salt per 5 pounds. Pack firmly until the salt draws out the juice.
4. Keep the cabbage under its brine. If there is not enough juice, top up with boiled and cooled brine made with 1 1/2 tablespoons of salt per quart of water.
5. Weigh it down with a plate and a brine-filled bag, and cover with a clean towel.
6. Ferment at 70 to 75°F: it takes about three to four weeks. At 60 to 65°F it takes five to six weeks; below 60°F it may not ferment, and above 75°F it may go soft.
7. When bubbling stops, refrigerate the finished kraut, tightly covered. It keeps for several months.

In quick vinegar pickles, acid from the vinegar does the preserving, and low-salt versions can be made safely. In fermented sauerkraut and brined pickles the bacteria have to make that acid themselves, and salt is what lets the right ones win. The NCHFP is blunt: do not try to make sauerkraut or fermented pickles by cutting back on the salt Nchfp. For pickles and relishes, it also warns never to alter the vinegar, food or water proportions in a tested recipe, because a minimum, even level of acid is what stops botulinum bacteria growing.

Kombucha is sweet tea fermented by a SCOBY, a mat of bacteria and yeast. The NCHFP tested recipe sanitizes equipment, measures the starter’s pH, cools the sweet tea below 95°F before adding the culture, ferments for 7 to 10 days at 68 to 77°F under a breathable cover, then bottles, refrigerates and uses the kombucha within 30 days Nchfp. Sealed bottles build up pressure and can burst, so check them.

If you are starting from scratch, Kombucha Kamp sells live SCOBY cultures and glass brewing vessels. Two cautions before you do. Home kombucha contains a variable amount of alcohol, so it is not for pregnancy, children or anyone avoiding alcohol. And it is barely studied: a 2019 systematic review found a single human study Kapp 2019, while a 1995 CDC report described two cases of unexplained severe illness, one fatal, in people drinking it daily CDC 1995.