Milk Kefir

Place the live kefir grains into a clean glass jar (do not use metal bowls or utensils with kefir — the grains are sensitive to reactive metals). Pour the whole milk over the grains at room temperature — if the milk is cold from the fridge, the fermentation will be slower and may take up to 36 hours. The ratio of grains to milk matters: about 1 tablespoon of grains per 250 ml milk is ideal. Too many grains ferment the milk too quickly, producing a very sour, thin result. Cover the jar with a cloth or paper towel secured with a rubber band — do not use an airtight lid during fermentation, as the CO2 produced needs to escape. Leave at room temperature (18–24 C) for 18–28 hours, tasting at 18 hours and again at 24 hours.

Pour the fermented kefir through a plastic or stainless-steel strainer (not fine-mesh — kefir grains need to pass through easily; use a coarse sieve with 2–3 mm holes) into a clean jar or pitcher. The grains will collect in the strainer. Stir gently with a plastic spatula to help the liquid drain through — do not force or press the grains. Once strained, rinse the grains very briefly under cool, unchlorinated water if desired (some fermenters do not rinse, which keeps cultures more diverse). Place the recovered grains into a fresh jar with fresh milk to begin the next batch immediately, or store the grains submerged in fresh milk in the refrigerator for up to 2 weeks. Seal the finished kefir and refrigerate; it will continue to ferment slowly and become more carbonated over 1–3 days in the fridge.