Lacto-Fermented Beets

Beets get mislabeled constantly. People say the red color is from anthocyanins — the same pigments in red cabbage. It is not. Beet pigment is betalain, a completely different compound class. Betacyanins (red-violet) and betaxanthins (yellow-orange) are nitrogen-containing compounds biosynthesized from tyrosine. Anthocyanins are flavonoids. Different chemistry, different stability profiles, different behavior under pH change.

Why does this matter for fermentation? Betalains are acid-stable and heat-labile. Cooking beets destroys a significant fraction of betalain content through thermal degradation. Lacto-fermentation drops pH without raising temperature — the brine never exceeds room temperature. A 2018 study (PMID: 29680057) confirmed that fermented beet products retained significantly more betalain activity compared to boiled controls, even though overall betalain content declined from enzymatic activity during fermentation.

The brine that comes out of this jar is deep magenta and tastes like sour beet juice. It is extremely useful in salad dressings, cocktails, and for staining anything you own that you care about. Use it deliberately or not at all.

Instructions

1. 

   1

   Prep the beets

   Wear gloves. Seriously. Beet juice stains skin, cutting boards, and grout for days. Peel the beets and cut into 1/4-inch coins or matchsticks about 2 inches long and 1/4 inch thick. Uniform thickness is critical — thicker pieces will still taste raw when thinner pieces are over-fermented. I use a mandoline set to 1/4 inch for coins, or cut matchsticks by hand for better jar packing.

   Chemist's note

   Golden beets ferment well too and produce a yellow-orange brine from betaxanthin pigments rather than betacyanin. The flavor is slightly milder. If you mix red and golden in one jar, expect an intermediate brine color and a conversation piece.

2. 

   2

   Weigh and dissolve the brine

   Weigh 480g of filtered water into a bowl. Add 12g of non-iodized salt — that's exactly 2.5%. Stir until completely dissolved. Beets have a high sugar content (9–10g per 100g) which drives fast fermentation. The 2.5% salt is conservative; some fermenters use 3% for beets because higher sugar content can accelerate pH drop unpredictably. I stick with 2.5% for flavor balance.

   Chemist's note

   If you've heard that beets need higher salt, that recommendation is usually for kvass — the thin fermented beet drink that uses much more water and ferments faster. For whole beet ferments, 2.5% is the sweet spot.

3. 

   3

   Pack the jar

   Place garlic, peppercorns, and caraway seeds at the bottom of a clean quart jar. Pack beet pieces tightly — the more compactly you pack, the less brine headspace, the less opportunity for surface kahm yeast. Beets shrink as they ferment and release their cell water into the brine, so pack aggressively at the start.

   Chemist's note

   Raw beets are dense and hard to pack in irregular chunks. Cut uniform shapes and stack them — coins stack vertically, matchsticks interlace horizontally. Both work. Chunks do not. Chunks leave gaps that become kahm yeast real estate.

4. 

   4

   Submerge and seal

   Pour brine over beets until fully submerged. The brine will immediately start turning pink-red as betalains leach from the cut surfaces — this is expected and correct. Place a fermentation weight on top. Seal with an airlock lid. If using a regular lid, loosen it or burp daily for the first week to release CO2 pressure.

   Chemist's note

   Beet ferment brine turns deep magenta by day 2. This is not contamination. This is betacyanin. The color is pH-sensitive — under the acidic conditions of fermentation it is stable, whereas in alkaline conditions it would shift toward brown-yellow. Your deep red brine is a real-time pH indicator.

5. 

   5

   Ferment 7–14 days, refrigerate when sour

   Store at 68–72°F. Bubbles should appear by day 2–3. Start tasting on day 5. Fermented beets at day 7 are tangy with earthy sweetness still intact. At day 14, they're fully sour with deeper complexity. When pH reads 3.4–3.8 and the flavor is right, move to the fridge. The brine is as valuable as the beets — use it as a shot, a salad dressing base, or a cocktail component.

   Chemist's note

   Save the brine. A 2024 study (PMID: 39752870) found that fermented beet juice from LAB fermentation showed enhanced antioxidant capacity and novel betalain derivatives (isobetanin, neobetanin) that weren't present in the raw material. The brine is where the action is.