Inspired by my brother-in-law doing the same, and by eating pots and pots of Skyr in Iceland, I've taken up the yoghurt-making challenge. Although you can buy kits and commercial starters to make your own yoghurt, I found a method that uses tools I had to hand. All you need is a slow cooker, a digital thermometer, a blanket, a small pot of your favourite Greek yoghurt, and two litres of milk.
Wash the slow cooker bowl and sterilise it in the oven (assuming it's a removable ceramic bowl), then put it back in the slow cooker, pour in the milk and turn the cooker to High. It should take around two hours to come up to temperature: the target is 82–85°C, and you need it to stay there for ten minutes. I let it hit 83°C or 84°C and then switch it off, as it'll stay in range for long enough as it cools. It then has to cool to 42–45°C; you’ll need to pop back and forth a bit to check on it. Keep washing the thermometer as you use it, to avoid contamination. Meanwhile, allow 100g of the yoghurt to come to room temperature in a clean bowl—this takes a couple of hours too.
When the milk is in the 42–45°C range, remove any skin that’s formed. Take out a cupful of milk and mix it into the yoghurt, then drizzle this mixture back into the milk. Put the lid on the slow cooker and lift the whole ceramic bowl out carefully and wrap it in a blanket; I put a doubled blanket on the kitchen table, then place the bowl on it and wrap the blanket carefully around it. You’re doing this to insulate the cooker and keep the milk in the target range for as long as possible. If you start the process around 7pm you’ll usually reach this point around midnight, and can then leave it until morning—it needs to sit for seven or eight hours.
In the morning you should have a big pot of set yoghurt. Put a colander on top of a mixing bowl and line it with muslin, then carefully pour in the yoghurt to strain out the excess whey. The longer you strain it, the thicker the yoghurt; an hour usually does it for me. When it's how you like it, spoon the yoghurt into jars and pop them in the fridge. For any Aussies or expat Aussies with a supply of them, 500g Vegemite jars with the plastic screw lids work well for this—I can fill about three of those per batch. Or you could visit Iceland, wash and save your Skyr pots, bring them home in your carry-on luggage and use those.
If you keep the whey (in a container in the fridge), you can use it in cooking: it works well in waffles in place of milk or buttermilk. I tried using it in breadmaking, but it makes the bread a bit tough.
The yoghurt will keep in the fridge for a week or two. When making it, you can use whole milk, semi-skimmed, skimmed or a mixture; half whole, half semi-skimmed works well. I even tried it using skimmed milk powder, but the yoghurt wasn't as creamy as I like it. FAGE yoghurt is a great starter (if you’re in the UK or US), but I’ve had decent results even with supermarket own-brand Greek yoghurt.
To make sweetened yoghurt, add a little jam, syrup, honey or chopped fruit to a dish of plain yoghurt. I’ve been making fruit compotes of stewed sliced apple and sultanas with cinnamon and raw sugar to add to mine.
One trouble-shooting tip: my first batch tasted fine, but had an unpleasant stringy consistency, with thin strands dripping from the spoon. I saw various possible reasons for this online; the most likely seemed to be that it was from wild yeast or some other form of contamination. I eliminated it by taking extra care with sterilizing the slow-cooker beforehand, and holding the milk in the 82–85°C range for the full ten minutes before cooling it.
Of course, you could skip all the faffing around and just buy one of these... which writing this post has now prompted me to do. I’ll report back in the comments on how well it works.
Sorry for the unwitty post title, it's my feeble attempt at search-engine optimisation. Make Your Own Yoghurt in a Slow Cooker Yoghourt Greek Yogurt Skyr Fage Chobani Jalna I Call it Frogurt.
Added by Rory on 16 June 2017.
Thanks - very interesting. Will try one day. You might be interested in kefir. Easy and can also use as starter for cheese, sourdough or sauerkraut. I did David Asher's course and it was fantastic.
Added by JJ on 16 June 2017.
Coooool! We get through about 2kg greek yogurt a week so this is very interesting! Can I ask what is it like, taste and texture wise? More like Total or Skyr?
Added by Shauna on 20 June 2017.
Kefir sounds good, JJ, thanks. Will have to try that too.
The texture is more like Total, Shauna, but if you strain it for longer it should get thicker.
Reporting back on the electric yoghurt maker: it’s great! Saves running back and forth to check temperatures, and if you start off with UHT milk you don’t need to heat and cool the milk first. If you can find one on sale for eleven quid, it’s well worth it.
Added by Rory on 20 June 2017.