This is an easy way to make yoghurt that does not require the expensive pre-packs of EasiYo powder (like the bag in the picture), using only UHT milk, milk powder and a yoghurt culture. No heating is required other than boiling water. I am using the EasiYo equipment but this technique works just as well using your own containers and insulated pots.
The basic equipment is:
yoghurt container/pot (1 litre- screw top so it doesn't pop open when warmed)
UHT whole milk (1 litre)
whole milk powder (4 rounded tablespoons)
natural yoghurt culture (1-2 tablespoons)
kettle for boiling water
Make sure everything is clean! Containers and utensils do not need to be sterile, normal washing and a rinse in clean water is fine for yoghurt making.
I made this yoghurt with my primary school class so the pictures are not perfect- and we are in Hong Kong, hence English and Chinese on the pack. It is UHT whole milk from Australia.
Step 1: Making the Thickened Milk
It is good to have all the ingredients at room temperature. UHT milk is already sterile so do not heat the milk, a step normally required to kill off bacteria in the milk.
To thicken the milk and produce thicker yoghurt, add around 25g of (about 3 rounded tablespoons) per 500 ml of whole milk powder. This can be adjusted to taste, more makes thicker, less makes thinner yoghurt.
Pour about half the milk at into the yoghurt pot.
Whisk until fully dissolved- I'm in Hong Kong so I use chopsticks as they can get right into the corners... Gok Wan calls it "the oriental whisk"
You may wish to add a teaspoon of sugar to slightly sweeten the yoghurt- I don't.
Step 2: Making the Yoghurt Mixture
The final step is to add the yoghurt culture. I use shop bought yoghurt but it must be "live' yoghurt, often labelled as "bio". Experiment with different brands of yoghurt to get a home-made product you like; each brand has it's own strains of Lactobacillus bacteria.
Add a 2 tablespoonfuls of yoghurt (usually enough but more does not cause problems).
Whisk in, then top up the yoghurt pot with UHT milk until almost full.
Put the lid on, invert the yoghurt pot a few times for a final mix. Place in the yoghurt pot in the thermos pot and add boiling water to about half-way up the yoghurt pot.
Place the cover on and leave for at least 12 hours. Longer will produce a thicker yoghurt.
The yoghurt will be thick and set like Greek yoghurt when done. It keep in the fridge for 10-14 days. Before you finish the tub, use some to make your next batch!
This yoghurt is great with honey, fresh fruit, for smoothies or can be used to make Bircher muesli.
The yoghurt will keep in the fridge for at least a week.
If the yoghurt does not thicken:
-add fresh warm (not boiling hot) water to the insulated container; leave for a few more hours
-if you still don't have yoghurt in a few hours, your yoghurt primer may not have been live.
-next time add more milk powder or more yoghurt culture
Yoghurt making requires milk, a culture and a water bath so you can easily improvise and do not need the specially made equipment here. The EasiYo system is cheap and effective though so well worth the purchase and I still buy the occasional EasiYo pack of powder as it is a great product.