Interactive lesson

Kvass and boza, step by step

Interactive lesson: boza, bread kvass and elderflower champagne — clean equipment, fermenting in the warm, pressure bottles and the PET test bottle.

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The whole lesson as text

1. Living drinks

Boza, kvass and elderflower champagne are made from next to nothing, in a day or two.

The same pattern — Sugar from fruit, bread, flour or added, then yeast or a starter, warmth and time.
The other drinks — Ginger beer and water kefir ferment with yeasts. Beet kvass is a lactic fermentation, like sauerkraut, and has almost no alcohol.
Starter from the last batch — A cup of the last boza goes into the new one. When you get a batch you like, keep 200–300 mL in the fridge for the next.
Warmth and time — Most ferment for 1–3 days at 20–25 °C (68–77 °F). In the fridge they keep 1–3 weeks; kvass and boza 3–5 days.

Why: Yeasts and lactic acid bacteria eat sugar and give the drink a tangy taste, bubbles and a little alcohol. All these drinks follow the same pattern; they differ in their base and in how long they ferment.

These drinks contain roughly 0.5–3 % alcohol; the longer they stand in the warm, the more.
If the starter goes off, start again with yeast.

2. Bottles under pressure

A drink fermenting in a closed glass bottle can shatter it like a bomb.

Pressure bottles only — Thick glass with a swing-top or PET bottles from fizzy drinks. Never jars, or juice, wine or cordial bottles.
The PET test bottle — One small PET bottle in every batch. Squeeze it every day.
Hard: all into the fridge — When the test bottle is rock hard, all the bottles go straight into the fridge. A fridge at 5 °C (41 °F) or below almost stops the yeast.
Place and opening — Keep fermenting bottles in a box with a lid, below eye level, away from children. Open a chilled bottle slowly, over the sink, neck away from your face.

Why: Yeast in a closed bottle makes carbon dioxide, so the pressure rises by the hour. After two or three days in the warm it can be higher than in a bottle of champagne.

Don't shake a bulging bottle: a few hours in the fridge, then open it in the sink wrapped in a thick cloth, with your face turned away.
Pregnant and breastfeeding women and drivers don't drink fermented drinks; small children only fresh ones, a little and rarely, or none.