+1 on making the yogurt. I have been making L. reuteri yogurt (or fermented milk, technically) for a few months. I started with some BioGaia Gastrus tablets in batch 1 and now just use a tablespoon or two of batch n - 1.
I recommend getting a sous vide device for precise temperature control. Initially, I used a the "Yogurt" function on an Instant Pot pressure cooker and about half of the batches failed, separating into whey and curds.
The article linked by parent says to use new BioGaia Gastrus tablets every 4-5 batches so as not to grow unwanted bacteria. Have you had any trouble reusing the same batch indefinitely?
The yogurt has the same taste and consistency as it did in the beginning, so I haven't had any trouble in that sense. However, it does seem prudent to restart periodically.
I started with Dr. Davis' recipe. It's described in his book "Super Gut" and is also available on his website [1]. My current method is a bit simpler:
- I buy full fat milk in a glass bottle so that I can make the yogurt directly inside without having to sterilize another container. I have had more success with UHT milk than pasteurized milk.
- I add two tbsp. (~40g) of my previous batch to one liter of milk. Close lid and shake.
- Put bottle in a pot of water, submerging most of the milk bottle. I leave the lid on, but untightened so that gas can escape.
- I add a sous vide "wand" to the pot and leave it for 24 hours at 38°C (100°F)
I deviate from Dr. Davis' recipe by not adding inulin to the milk and fermenting for a shorter duration. This probably results in fewer bacteria present in the final product, but the above takes me less than 5 minutes to prepare.
I recommend getting a sous vide device for precise temperature control. Initially, I used a the "Yogurt" function on an Instant Pot pressure cooker and about half of the batches failed, separating into whey and curds.