I use organic milk which is £1.50 for 2 litres (a litre is roughly equivalent to an American quart) meaning that for 1kg (just over 2lb) yoghurt it costs me 75p which I'll round up to 80p to allow for cost of electricity, wear and tear on utensils etc. If I bought organic yoghurt ready made it would cost £2.09/kg and even if I bought the very cheapest non-organic yoghurt it would cost me 96p compared with about 65p for yoghurt made with non-organic milk.
Originally I used a recipe I found elsewhere but I found that it produced very inconsistent results and was usually much runnier than bought yoghurt. Over time I developed my own recipe which I have found produces a nice thick yoghurt every time:
- Time switch
- Spoon (any old eating spoon will do)
- Pint/Half litre jug for mixing yoghurt and milk the first time
- Insulation for crock from crockpot (I use one of these but a large towel would do)
- Containers for storing yoghurt (I usually use a couple of old 1kg/2lb ice cream tubs and an old 500g/1lb yoghurt pot)
- 3 British pints/2 litres/2 American quarts whole milk
- 1 small pot natural yoghurt or a cup of yoghurt left over from the previous batch*
1) Put 3 British pints (or 2 litres or 2 American quarts) of milk into your crockpot.
2) Set the time switch for 3 hours and turn the crockpot to low. (You can do it without the time switch but the time it is on for is a critical part so if you don't have one, make sure you set yourself an alarm to remind you to switch it off.)
3) Wait at least two hours after the heat has been turned off. (I usually aim for 2-4 hours but have left it for seven without affecting the results.)
4) Put the yoghurt in the jug
5) Ladle in an equivalent amount of warm milk.
6) Mix well and then pour half of the mixture into the crockpot.
7) Stir the warm milk (which now has some yoghurt added) and then repeat steps 5 &6 a couple of times before adding all of the yoghurt/milk mixture to the crockpot and stirring thoroughly.
8) Insulate using either a solar cooker or some large towels and leave overnight.
The Next Day
9) Remove slow cooker from insulation.
10) Ladle about one cup of yoghurt into the old yoghurt pot** and then put the remainder in the other tubs.
11) Place yoghurt in fridge.
* The longest I have kept yoghurt for the next batch is three weeks. Of course you should check for signs of mould and smell it to make sure it is okay. If in doubt, it is better to buy some fresh starter yoghurt than to risk getting ill.
** The cup of yogurt in the yogurt pot can be used for the next batch of yogurt. The milk can be mixed direct in the pot removing the need for a separate jug to be used.