How to Make Yoghurt in a Slow Cooker

Making yoghurt in a slow cooker sounds like one of those things that is either going to be ridiculously easy or end with a litre of warm milk and me wondering why I didn’t just buy a pot of yoghurt from Aldi.

Slow cooker yoghurt is actually fairly simple, but this isn’t one of those slow cooker recipes where you can chuck everything in, disappear for eight hours and hope for the best. Temperature matters because you’re trying to create the right conditions for the live cultures in the yoghurt to ferment the milk.

You only need two ingredients for the yoghurt itself: milk and a little plain natural yoghurt containing live cultures. I would definitely recommend using a food thermometer too. This isn’t the time to stick a finger in the milk and decide it feels about right!

If you usually buy yoghurt for overnight oats, making your own could be a fun experiment, especially if you get through quite a lot of natural yoghurt.

What you need to make homemade yoghurt

For approximately 1 litre of yoghurt you will need:

• 1 litre pasteurised whole milk
• 2 tbsp plain natural yoghurt containing live cultures

You’ll also need:

• a slow cooker
• a food thermometer
• a whisk or spoon
• a clean heatproof container with a lid that fits inside your slow cooker
• a clean towel

Whole milk is my first choice here because it gives you a creamier yoghurt. You can make yoghurt with lower-fat milk, but don’t necessarily expect exactly the same consistency.

The starter yoghurt is important. Check the label and make sure you’re buying a plain yoghurt containing live cultures rather than choosing one simply because it says “natural” on the front.

How to make yoghurt in the slow cooker

1. Heat the milk

Pour the litre of milk into your clean slow cooker and switch it on.

Heat the milk until a food thermometer reads 82–85°C. Give it an occasional gentle stir so the milk heats evenly and doesn’t catch around the edges.

How long this takes will depend on your slow cooker, which is why I’d go by temperature rather than telling you it will definitely take a particular number of hours.

Heating the milk isn’t just about making it hot. Heating it to this sort of temperature changes the milk proteins and helps give the finished yoghurt a better set.

2. Cool the milk

Switch off the slow cooker and allow the milk to cool to around 43°C.

Again, use your thermometer rather than guessing.

You don’t want to add your live yoghurt while the milk is still at 85°C because excessive heat can damage the bacteria you’re relying on to ferment the milk.

If you want to speed the cooling up, carefully transfer the milk to a clean heatproof bowl and stand that bowl in cold water, keeping the water out of the milk.

3. Add the live yoghurt

Put the 2 tablespoons of plain live yoghurt into a small clean bowl.

Add a little of your cooled milk and stir until smooth. Pour this mixture back into the rest of the milk and stir gently until combined.

Doing it this way is easier than trying to whisk a blob of cold yoghurt evenly through a litre of milk.

4. Incubate the yoghurt

Pour the yoghurt mixture into a clean heatproof container and cover it.

Clean the slow cooker if necessary and add warm water at approximately 49°C. Put your covered container of yoghurt into the slow cooker, making sure the water comes part-way up the outside of the container but cannot get inside it.

Put the slow cooker lid on and wrap the cooker in a clean towel to help retain the warmth.

Leave the yoghurt undisturbed for around 6–10 hours.

Don’t keep opening it and stirring it to see whether anything is happening. This is one of those occasions where interfering with it really isn’t helpful!

The longer yoghurt ferments, the more tart it can become, so once you’ve made a batch you’ll probably develop your own preference.

5. Refrigerate the yoghurt

Once the yoghurt has set, cover it and put it into the fridge promptly.

Don’t worry if it seems softer than the thick Greek-style yoghurt you might normally buy. It will firm up more as it chills.

I’d give it several hours in the fridge before deciding whether you’re happy with the final consistency.

Once it’s chilled, try it with fruit for breakfast, use it in overnight Weetabix, or keep some plain for savoury recipes. Yoghurt is also one of the ingredients I use in my slow cooker chicken tikka masala.

Why is my homemade yoghurt runny?

Don’t assume you’ve failed just because your yoghurt isn’t as thick as a supermarket Greek yoghurt. Homemade natural yoghurt can be considerably softer, particularly before it has chilled properly.

If it is still very runny after chilling, there are several things to consider.

Check that your starter yoghurt contained live cultures and was fresh, that you heated the milk sufficiently before cooling it, and that you didn’t add your starter while the milk was still too hot.

The incubation temperature matters too. Too hot isn’t good for the cultures, but neither is letting everything become too cold.

And make sure everything you’re using is properly clean. Making yoghurt relies on encouraging the bacteria you actually want rather than introducing bacteria you don’t!

How to make thicker Greek-style yoghurt

If your yoghurt has set nicely but you simply want it thicker, strain it after chilling.

Put a clean muslin or other suitable fine cloth into a sieve over a bowl, add the yoghurt and leave it to drain in the fridge.

As the whey drains away, the yoghurt becomes thicker. Check it periodically because the longer you leave it, the thicker it will become. Straining it gives you something closer to the thicker texture you might associate with Greek yoghurt, although I’ve got a separate guide explaining the differences between Greek and plain yoghurt if you’re interested.

Don’t pour away the whey immediately either. You can use it in smoothies, bread and some baking recipes if you fancy experimenting.

Can I use semi-skimmed or skimmed milk?

You can make yoghurt using lower-fat milk, although the texture can be thinner than yoghurt made with whole milk.

If thickness is important to you, I’d start with whole milk for your first attempt so you’ve got a useful benchmark. Once you’ve successfully made that, experimenting with the milk is much easier because you’ll know what the process should look like.

Can I make slow cooker yoghurt with plant-based milk?

I wouldn’t simply replace the dairy milk in this recipe with a litre of almond, oat or coconut milk and expect identical results.

Plant-based milks behave differently and homemade plant-based yoghurt recipes can require different cultures, thickeners or techniques.

This particular recipe has been developed around dairy milk, so if you need dairy-free yoghurt I’d use a recipe specifically designed for the type of plant milk you want to use.

When should I add fruit, honey or vanilla?

Afterwards!

I’d keep your yoghurt completely plain while it is fermenting. Once it has set and chilled you can divide it into portions and add whatever you fancy.

Berries, banana, jam, honey, maple syrup and vanilla are all easy options. Keeping the main batch plain also means you don’t have to commit a whole litre to one flavour.

Plain yoghurt is useful for savoury recipes too. Try it in dressings, dips, sauces and marinades, or simply spoon it onto spicy food instead of adding cream.

Can I use homemade yoghurt as the starter for my next batch?

You can use some freshly made homemade yoghurt to start another batch, providing the cultures are still active.

I’d set aside the amount you need before adding fruit, sugar or other flavourings.

If you make yoghurt regularly, using a little of one batch to begin the next is a lovely idea. If a batch doesn’t set properly, smells unusual or you’re in any doubt about it, though, don’t use that as your next starter. Go back to a fresh pot of commercially produced plain yoghurt with live cultures.

How long does homemade yoghurt keep?

Once it has fermented, homemade yoghurt needs to be refrigerated.

Keep your homemade yoghurt covered in the fridge at 5°C or below. I prefer to make an amount I’ll use fairly quickly rather than leaving homemade yoghurt hanging around at the back of the fridge.

Remember that homemade yoghurt hasn’t got quite the same controlled production and packaging as the pot you pick up from a supermarket, so good hygiene and refrigeration matter.

A few things I’d remember for your first batch

The thermometer is probably the most important piece of equipment in this recipe. Don’t try to judge the temperatures by eye.

Use fresh pasteurised milk, a fresh plain yoghurt that definitely contains live cultures and clean equipment.

Most importantly, don’t be disheartened if your first batch isn’t exactly like the yoghurt you usually buy. Once you know how your particular slow cooker holds its temperature and how long you like to ferment your yoghurt, the whole process becomes much less mysterious.

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