Homemade Yogurt

We eat a lot of yogurt. Sidney and his dad eat some after every meal (currently mixed with a little apple compote), and I join them more often than not. Plus we ate Bircher muesli with yogurt every morning for most of the summer. We used to buy Greek yogurt from the supermarket, which is delicious but not often organic, and I’d read so much about how easy it is to make it at home that we decided to give it a try.

Yogurt is just milk and culture. It’s nothing more complicated than that. There are lots and lots of methods for making it at home, but the key to all of them is temperature. You need to heat your milk to 80˚C and then cool it to around 45˚C, at which point you add a spoonful of yogurt. Then you’re done.

What’s tricky is maintaining the temperature for long enough to set the milk. Heating the yogurt kills off any bad bacteria and changes the protein structure so that it sets firm rather than splitting, plus it gives a richer flavour. You need to cool it because if it’s too hot it will kill the active cultures that make it yogurt. You want to maintain a temperature of between 43˚C and 35˚C long enough for the proteins to multiply and set the yogurt.

We tried several methods. First I put plastic pots in the oven, but mine isn’t sensitive enough to maintain such a low temperature consistently. Then I tried keeping jars warm in a rice cooker. That didn’t work either. I tried the oven again, this time pouring the yogurt into a terracotta pot. That worked a bit better, but it took quite a bit of effort to maintain the right temperature and the yogurt was a little thin in the middle. It was too fiddly for me to bother doing it regularly (plus there was a nasty aftertaste from the pot).

Finally I tried the simplest method I’d read about. I poured the yogurt into pots again and kept them warm in a picnic cool bag. It sounds counterintuitive, but what keeps food cool will also keep it hot. It worked perfectly and we had smooth, creamy yogurt all through the summer.

Then autumn came, the temperature dropped and our delicious yogurt refused to set. It just wasn’t warm enough in the kitchen to keep the temperature inside the cooler high enough for long enough. Plus I think the yogurt was cooling too quickly during the jarring process.

But I soon found a trick to make it work, inspired by Nigel Slater who wraps his jar in a towel with a hot water bottle. Into the cooler goes my hot water bottle to warm it up while I heat the milk. Once the jars are filled (smaller ones than I use in the summer) they go into the cool bag and I stuff the hot water bottle in the top before zipping it up and storing it in the airing cupboard for a few hours.

It’s a makeshift system, but it works, and we have a ready supply of organic yogurt that gets better and better with every generation. I reckon it takes about 20 minutes to make, then you just wait for the magic to happen. It’s that simple.

Here’s how we make it.

Homemade Yogurt

Makes 5 jam jars

2 pints organic milk (we use whole milk)

a small pot of organic live yogurt, at room temperature (the first time you make it, after that you can use a little of the previous batch)

You will need

sterilised jars (I use bigger ones in the summer, smaller in the winter)

thermometer (get one that clips to the side of your pan and adjust the height so that the tip is suspended in the milk and not touching the bottom of the pan. You’ll get a more accurate reading this way)

Pour about a centimetre of water into the base of a medium pan and bring to the boil. This will help prevent the milk sticking to the pan.

Pour in the milk and bring to 80˚C, then turn off the heat and cool to 43–45˚C. To speed up the process I fill the sink with a few inches of cold water and sit the pan in it to cool down.

As soon as the temperature hits 43–45˚C, spoon the live yogurt into the milk and give it a stir.

Quickly pour the mixture into the jars. (A wide funnel will help speed things up and lessen waste.) Transfer the sealed jars to a cool bag and leave for 5 or 6 hours to set. If your kitchen is cold you might want to store the bag in the airing cupboard with something warm inside (such as a hot water bottle, see above).

If you open your jars and find they’re only set in the middle, take the lids off and sit them in a pan of boiling water. Reheat until the yogurt reaches 43˚C and return to the cool bag. The texture might be a little grainier, but they should set all the way through.

There’s no need to buy more yogurt, simply save portions from each batch to make the next. Once your yogurt is set, scoop out a couple of tablespoons straight away and store them in a separate container ready for the next batch. You can also freeze this portion, but bring it back to room temperature before adding it to your milk.