Specialty Fermented Breads: Kvass, Rye Sourdough & Soda Bread

Once you are comfortable with a basic wheat loaf, fermentation opens up a much wider world. Some of the oldest and most distinctive breads — and even a drink made from bread — sit just outside the standard sourdough recipe. This guide looks at three specialty ferments: tangy rye sourdough, the bread-based drink kvass, and quick soda bread, which earns its place here through cultured buttermilk rather than yeast.

Each one teaches something different about how fermentation, acidity, and grain interact. If you have already worked through a no-knead loaf, these are the natural next experiments.

Rye Sourdough: Fermentation Doing the Structural Work

Rye is the specialty grain that most rewards a sourdough approach. Where wheat builds an elastic gluten network you can stretch and fold, rye has almost no usable gluten. Instead it is rich in pentosans — gums that soak up water and turn the dough into a sticky, clay-like paste. You cannot knead rye into a smooth ball, and trying to will only frustrate you.

What holds a rye loaf together is acidity. A well-soured dough firms up the pentosans, controls the enzymes that would otherwise make the crumb gummy, and gives rye its characteristic deep, malty tang. This is why rye is almost always made as a sourdough rather than with commercial yeast — the sour is structural, not just flavour.

Building a rye dough

A few things change compared with a wheat bake:

• Use a wetter, stickier dough and wet hands. Rye dough is shaped, not kneaded. Wet or oil your hands and bench rather than adding flour.
• Lean on your starter. A rye-fed starter ferments quickly and deepens the flavour, but a healthy wheat starter works too. Get it lively first — see the active sourdough starter guide.
• Mind the hydration. Rye drinks far more water than wheat. If you are scaling a recipe, the hydration calculator keeps the flour-to-water balance sane.
• Watch the bulk closely. Rye ferments fast and can over-soften, so don’t push it as long as a wheat dough. The bulk fermentation guide covers reading the signs.

Baking and resting

Rye holds a lot of moisture, so it needs a long, thorough bake. Use a thermometer rather than the clock — check the internal temperature guide for targets. Then comes the hardest part: wait. A dense rye loaf needs up to 24 hours of resting before slicing so the crumb can set. Cut it warm and it will seem gummy even when perfectly baked.

Kvass: A Drink Made From Bread

Kvass is one of the most resourceful ferments in the European tradition — a lightly fizzy, low-alcohol drink built from stale rye or sourdough bread. For centuries it was the thrifty answer to the question every sourdough baker eventually asks: what do I do with the heels and the loaves that went hard?

The method is simple:

1. Toast stale rye or sourdough bread until deeply browned — the colour drives the flavour.
2. Steep it in hot (not boiling) water with a little sugar, and let it cool to lukewarm.
3. Ferment the strained, sweetened liquid with wild yeast, a pinch of baker’s yeast, or a spoonful of active starter for one to two days at room temperature.
4. Bottle it, optionally with raisins or fruit, and chill.

The wild cultures eat the sugar and produce carbon dioxide and a touch of alcohol — usually around 0.5–1%, similar to a kombucha. The result is tangy, faintly sweet, and refreshing. If your starter maintenance leaves you with extra culture, a spoonful of discard makes an excellent fermentation booster for the steep, though the baked bread should still carry the flavour.

Kvass closes the loop on a sourdough kitchen: the same wild fermentation that raised the loaf can turn its leftovers back into something worth drinking.

Soda Bread: Fermented Flavour Without the Wait

Soda bread is the outlier in this trio. It is not yeast-fermented — it rises chemically, when baking soda meets the acid in buttermilk and releases carbon dioxide in the oven. There is no starter, no bulk fermentation, and no proofing. You mix it fast and bake it immediately, because the reaction starts the moment wet meets dry.

So why include it among fermented breads? Because its defining ingredient is a ferment. Buttermilk is cultured, soured dairy, and that lactic tang is exactly what both flavours the bread and powers the rise. Without a fermented acid, the soda has nothing to react with. In that sense soda bread borrows the product of fermentation rather than the process.

A few practical notes:

• Don’t over-mix. Bring the dough together just until it coheres. Overworking develops toughness and lets the gas escape before baking.
• Use real cultured buttermilk (or soured milk) for both the lift and the flavour. Sweet milk plus soda won’t rise the same way.
• Bake at once. Get it into a hot oven immediately to capture the gas while the reaction is active.

For a baker used to the patience of sourdough, soda bread is a refreshing change of pace — a fermented-tasting loaf on the table in under an hour.

Three Routes From One Skill

These breads look very different, but they all grow out of the same fermentation literacy. Rye uses the sour itself as structure. Kvass turns finished bread back into a living ferment. Soda bread leans on a cultured dairy product for both lift and tang. Together they show how flexible “fermented bread” really is.

If you want to keep exploring, the sourdough FAQ and glossary defines the terms you will meet along the way, the active starter guide keeps your culture strong enough for a rye bake, and the feeding and hydration calculators handle the arithmetic so you can focus on the craft.