I have been making yoghurt for around four years on and off. I had a batch going in New Mexico that lasted for over two years without ever having to buy a new starter culture.
I don't use a machine and I didn't used to use a thermometer but after having a failed batch in this country I checked other recipes on line to find the common method of making yoghurt.
Ingredients: 2pints of full-fat milk
4Tblspn live yoghurt
3Tblspn dried milk powder
So to make 2 pints of yoghurt: bring 2 pints of full fat milk with 3tablespoons of dried milk powder whisked in gently up to the boil. You just want to get it to the point where the bubbles are forming on the edge of the pan. Don't burn burn the milk on the bottom of the pan!. If you have a sugar or jam making thermometer it should read 82c/180f. Take off the heat and let the milk cool in a glass bowl or large jar. Cover the bowl to stop milk forming a skin. when the milk has cooled down to about 43c/105f. or where it feels warm to the skin but not hot stir in 4 tablespoons or 75g of yoghurt. This has to be a yoghurt that states it has live culture in it, or it won't work. I used Sainsbury's Greek style natural yoghurt. Re-cover your bowl or jar and place in a large pan with enough warm water to reach up the sides of your bowl. Grab a couple of towels and wrap the pan up to keep your yoghurt warm. The yoghurt should set within 8 hours depending on the temperature in your house. Some people put the yoghurt in a wide mouthed thermos to keep it at warm temperature, might do this in the winter. Check every few hours to see if the water is still warm, mine stayed warm so I didn't have to refill the pan.
This is the size pan I used but put it on the work surface with a towel under it and put another towel over the top.
This yoghurt has set really well and it has a pattern of bubbles on top!
Just showing off now.
What better way to serve yoghurt than with some stewed cherries that were picked fresh off the tree for free.
Don't forget to save some of the yoghurt to start a new batch. You can freeze the yoghurt in an ice cube tray and save in a bag or container so you always have a starter culture when you need it.
Here are my calculations for the cost of making yoghurt.
Milk if bought from Asda 4pints for 1 pound = 50p for 2 pints
Sainsbury's Greek natural style yoghurt 200g pot for 55p so 75g needed = 21p
Asda dried skimmed milk powder 340g for 1.88 so 20g needed = 11p
grand total of . . . 82p for 2 pints but next time it's cheaper as you will have the starter yoghurt so it will only cost 61p.
You don't have to use dried milk in a recipe, as I never have before but it did make it a bit thicker and smoother textured. I might try with just 2 Tbsps. next time to see how that works out.
I find it keep in the fridge for up to 10 days.
Note for American readers: An English pint is 20 fl.oz