The god of small things is a man called Katz

Sandor Katz is a master of all things fermented and cultured. My go-to reference for fermentation techniques is Sandor's YouTube channel or his encyclopaedic work on the subject, The Art of Fermentation.

I have taken to making yoghurt at home using Sandor's advice (Sandor's Yoghurt Workshop). This method produces a pretty good yoghurt using a supermarket yoghurt as a culture. However, as Sandor advises, results will degrade dramatically for subsequent generations due to the lack of biodiversity in commercial yoghurts. I am looking for a good yoghurt culture, but in the meantime, I follow a buy one, make one pattern.

Your guarantee of live cultures in a supermarket yoghurt are the words "pot set". This means the milk and culture have been poured into the container to set, rather than being batch-set and then put into packaging. Batch-set yoghurt often undergoes further processing or has additives which may compromise the biota.

Ingredients

• 2L Milk - I have had success with UHT milk and with powdered milk
• 1 Tbsp Yoghurt with live cultures

Equipment

• Pot for heating milk >4L
• Thermometer (all I have is a candy thermometer, which is not ideal, but still works)
• Hot box: An insulated box which will maintain heat for a few hours. I use our, otherwise underutilised, car fridge. An esky (chillibin) will do, or even a box lined with a 5cm layer of crumpled newspaper, rags or reclaimed styrofoam packaging.
• Jars or other containers for the yoghurt

Method

Short version: Bring the milk to 80C. Cool it to 50C. Keep it above 40 for 8 hours or more.

1. Set the milk over a low to medium heat. Our target temperature is 80C (180F), but go slowly and stir regularly. This will take about 20 minutes. While you are waiting, prepare the next steps.
2. Wash your containers and lids really well. I don't bother to sanitise for yoghurt as we are not aiming for long-term storage. A rinse with the hottest tap water should be sufficient to pasteurise.
3. Part-fill a sink with cold water - we will use this to rapidly cool the milk
4. Heat your hot box to 45-50C (110-120F). I pour about a litre of boiling water and half a litre of room temperature water into my car fridge.
5. Take the pot off the stove and submerge it in the cold water in the sink. Keep stirring until the temperature drops to around 50C (120F)
6. Put the culture into one of your jars and half-fill with milk. Shake well, then pour this mixture back into the pot to inoculate the milk.
7. Pour the inoculated milk into the containers
8. Put the containers into the hot box
9. Check the hot box temperature after about 4 hours. I always need to refresh it by removing and replacing some of the water to bring it back to temperature.
10. Refrigerate the finished yoghurt.