Before You Start

Set up a sous-vide precision cooker (or an adjustable yogurt maker) that can hold a rock-steady 106°F (41°C). This temperature is the crucial compromise that keeps all three strains alive: L. reuteri thrives around 97–100°F and dies above 109°F, while L. gasseri and B. coagulans prefer it warmer, so 106°F keeps everyone happy. Preset yogurt makers and Instant Pots run at 108–120°F and will kill the L. reuteri — don't use them. Verify the real temperature with an independent thermometer.

Prepare the Cultures

Crush 10 BioGaia Gastrus tablets to a fine powder. Open one L. gasseri BNR17 capsule and one B. coagulans capsule and empty them out.

Make the Starter Slurry

Whisk the crushed tablets and capsule contents together with 2 tablespoons of inulin and about 2 tablespoons of your half-and-half until completely smooth. Whisking a smooth slurry first is crucial — it distributes the cultures evenly and prevents clumping.

Combine and Jar

Stir the remaining half-and-half into the slurry until fully blended. Pour into clean wide-mouth Mason jars and seal with plastic lids — never metal, which reacts with the acidic yogurt.

Ferment at 106°F

Place the jars in your water bath at 106°F and ferment for 36 hours. Keep the water below the lid line, or leave the lids slightly loose, so a little gas can vent.

Chill and Set

Refrigerate the jars. The yogurt thickens as it cools and is usually perfect by the next morning. For a Greek-style texture, strain through cheesecloth for 4–6 hours.

Reculture Your Next Batch

Instead of buying starters again, stir 1/3 cup of this batch into your next quart of half-and-half and prebiotic. The triple-strain blend stays balanced for about 8–10 generations before the strains drift and it's worth starting fresh.

A Note on Your First Batch

First batches often separate into curds and whey — this is normal, not a failure, and the yogurt is still fully potent. Whisk it smooth and use it to seed batch two, which comes out thicker and creamier.