Making yoghurt at home is simpler than most people expect. The process has two variables that matter – temperature and starter culture – and once you understand why they matter, the rest is just following a straightforward sequence of steps. Homemade yoghurt is milder than commercial yoghurt (you control the fermentation time and therefore the acidity), contains more live cultures (commercial yoghurt is often heat-treated after fermentation), and costs a fraction of the commercial equivalent. It’s also one of the most satisfying things you can make in a kitchen because the transformation is genuinely remarkable: warm milk and a spoonful of culture become yoghurt overnight without any further intervention from you.
What You Need
1 litre of whole milk (full-fat UHT works, but fresh pasteurised gives a better result), 2 tablespoons of plain yoghurt with live cultures as your starter (use store-bought to start – any yoghurt with live cultures will work), a thermometer (a digital probe thermometer is best; a jam thermometer also works), a heavy-bottomed saucepan, a clean jar or container with a lid, and a way to maintain warmth for 6-8 hours (options below).
The Method
Heat the milk in a heavy saucepan over medium heat, stirring frequently to prevent scorching, until it reaches 85°C. Hold it at this temperature for 5 minutes – this denatures the whey proteins and produces a thicker, more cohesive yoghurt than milk heated only briefly. Remove from heat and allow to cool to 43-46°C (this is the key temperature range – the bacteria in the starter are active and multiplying between 40-46°C, but die above 50°C, so accuracy here is important).
Whisk the 2 tablespoons of starter yoghurt into a small amount of the warm milk to temper it, then stir this mixture into the rest of the milk. Pour into your clean jar or container and seal. Now keep it warm at around 43°C for 6-10 hours. Options: wrap the jar in a thick towel and place in a turned-off oven with just the light on; use a yoghurt maker (purpose-built and foolproof); place in a thermos flask; or use an Instant Pot on the yoghurt setting. A longer fermentation produces a more acidic yoghurt; shorter produces a milder result. Check at 6 hours – if it’s set (the jar tilts without sloshing), it’s done.
Straining for Thickness
Fresh homemade yoghurt is thinner than the commercial variety. To thicken it: pour into a colander lined with cheesecloth over a bowl and refrigerate for 1-4 hours. Strain for 1 hour for a texture similar to commercial yoghurt; 2-3 hours for Greek-style yoghurt; 4+ hours for labneh. The liquid that drains off is whey – keep it for bread, pancakes, or smoothies. Don’t discard it.
Saving Starter for the Next Batch
Reserve 2 tablespoons of your finished yoghurt in a separate sealed container before using the rest. This becomes the starter for your next batch. A continuous cycle of homemade yoghurt, where each batch seeds the next, can be maintained indefinitely. The culture does gradually drift in flavour and potency over time – if your yoghurt stops setting reliably after many cycles, buy a fresh commercial yoghurt to restart. Some people maintain the same culture for years; others refresh it every few months.
Choosing Your Milk
The milk you start with shapes the yoghurt you end up with. Full cream dairy gives the thickest, richest result because the fat and protein both contribute to body. Skim milk will set, but the yoghurt is thinner and sharper, and usually wants straining or a spoon of milk powder to firm up. Fresh pasteurised milk gives a cleaner flavour than UHT, though UHT is convenient and lets you skip the heating step, since it has already been heated hard during processing. For your first few batches, steer clear of ultra-filtered or lactose-free milk, as the altered sugars and proteins can give an unpredictable set.
Plant milks are a separate story. Soy, oat, coconut and almond milks do not contain the lactose and casein that dairy cultures feed on and bind to, so they will not set the same way. You can make plant-based yoghurt, but it needs a starter made for plant milk and often a thickener like tapioca or agar. If you want plant yoghurt, treat it as its own recipe rather than a swap.
Keeping It Warm: The Methods Compared
The one thing that makes or breaks a batch is holding a steady warmth of around 43°C for the whole ferment. A few ways to manage it, from least to most reliable:
- Oven with the light on: wrap the jar in a thick towel and sit it in a turned-off oven with just the interior light running. In most kitchens the light gives off enough gentle heat. Free, but check your oven actually holds the warmth.
- Esky or cooler box: sit the jar in an esky next to a jar of hot water and close the lid. The insulation holds the warmth for hours, which is handy in a cold kitchen.
- Thermos flask: pour the cultured milk straight into a wide-mouth thermos. It holds temperature beautifully, though you cannot check the set without tipping it out.
- Yoghurt maker or multicooker: a purpose-built maker, or the yoghurt setting on a multicooker, takes the guesswork out entirely. If you make yoghurt often, this is the easiest path to a consistent result.
Troubleshooting
It didn’t set. The two usual causes are heat and culture. If the milk was still above about 46°C when you stirred the starter in, the heat will have killed the bacteria. If your starter was old or had no live cultures, there was nothing there to do the work. Use a fresh plain yoghurt that lists live cultures, and let the milk cool to the low 40s before adding it.
It’s too thin. Thin yoghurt is normal before straining. For a thicker set next time, hold the milk at 85°C for a full five to ten minutes, which firms up the proteins. Straining through cloth for an hour or two will thicken any batch.
It’s too sour. Sourness comes from time. The longer it ferments, the more acid the bacteria produce. If your yoghurt is sharper than you like, pull it out of the warmth earlier next time, checking from the four hour mark.
It’s grainy or lumpy. This usually means the milk got too hot, or it was stirred too hard once the culture went in. Heat gently, stir the starter in softly, then leave it alone to set.
It’s stringy or slimy. A ropy, stretchy texture points to a culture that has drifted over many reuses, or a stray contaminant. Start again with a fresh commercial starter and clean equipment.
Common Questions
Is homemade yoghurt safe to eat? Yes, when made with clean equipment and fresh milk. The acidity the cultures produce actively holds off spoilage bacteria. Trust your senses, though. If a batch ever smells off, looks mouldy, or tastes wrong, throw it out.
How long does it keep? Stored in a sealed container in the fridge, homemade yoghurt keeps for one to two weeks. The flavour sharpens over that time as the cultures stay slowly active.
Can I flavour it? Yes, but add anything sweet or fruity after the ferment, not before. Sugar and fruit during fermentation can throw the cultures off. Stir through honey, vanilla, or fruit once the yoghurt has set and chilled.
