How to Make Yogurt at Home: The Complete Method
Homemade yogurt costs approximately 30 to 40 pence per 500g (using own-brand whole milk at approximately 70 to 80 pence per litre), compared to £1.00 to £1.50 for standard commercial yogurt or £1.50 to £2.50 for Greek yogurt. Beyond the cost, homemade yogurt can be made without stabilisers, thickeners, or preservatives, contains live bacterial cultures (unlike some commercial yogurts that are heat-treated after fermentation), and can be made to any thickness from pourable to very thick strained Greek-style. The process is straightforward once the temperature management is understood. The two critical variables are temperature (the bacteria require 40 to 45°C to ferment; too hot kills them, too cool produces slow or failed fermentation) and sufficient fermentation time (4 to 12 hours depending on desired tartness).
What You Need
- Milk: 1 litre whole milk (full-fat gives the creamiest result; semi-skimmed works but produces a slightly looser texture; UHT milk works adequately if fresh is not available, though the flavour is slightly different)
- Starter culture: 2 tablespoons of plain, live, full-fat yogurt with active cultures (any good-quality live yogurt, e.g., Yeo Valley plain, Total Greek, or a dedicated yogurt starter sachet from health food shops). After the first batch, use 2 tablespoons from your own homemade batch as the next starter.
- Thermometer: Essential. An instant-read thermometer is ideal; a jam/sugar thermometer works. Temperature accuracy is the most important variable.
- Incubation equipment: A warm, stable environment at 40 to 45°C for 4 to 12 hours. Options: a yogurt maker (approximately £20 to £40), a turned-off oven with just the oven light on (approximately 35 to 40°C), a warm airing cupboard, a wide-mouth insulated flask, or a dehydrator set to 43°C. The oven light method is the simplest without dedicated equipment.
The Method
- Heat the milk: Pour the milk into a saucepan and heat to 82 to 85°C (approximately 180°F) while stirring occasionally to prevent scorching. The purpose of heating above the fermentation temperature is to denature the whey proteins (particularly beta-lactoglobulin), which allows them to bind to casein micelles during fermentation and produces a thicker, more stable yogurt. Do not boil. If using UHT milk, you can skip this step and begin at the cooling stage.
- Cool to 40 to 46°C: Remove from heat and allow to cool, stirring occasionally. This takes approximately 15 to 30 minutes at room temperature; placing the pan in a cold-water bath speeds this to 5 to 10 minutes. Use the thermometer; the target is 40 to 46°C. Above 46°C will kill the bacteria; below 38°C will produce very slow fermentation.
- Add the starter: Scoop 2 tablespoons of starter yogurt into a small bowl. Add 3 to 4 tablespoons of the warm milk to the starter and stir to combine (this tempers the starter and prevents curdling). Pour the tempered starter into the warm milk and stir gently to distribute.
- Incubate: Pour the inoculated milk into your incubation vessel (a glass jar, ceramic bowl with a lid, or the yogurt maker's pots). Keep at 40 to 45°C for 4 to 12 hours. Short fermentation (4 to 6 hours) produces mild, less tangy yogurt; longer fermentation (8 to 12 hours) produces a more tart, tangier result with a lower pH. Check at 4 hours: the yogurt is ready when it has set and wobbles as a single mass when the container is gently tilted. It will not be as firm as cold commercial yogurt; it firms further when chilled.
- Refrigerate: Transfer to the refrigerator without disturbing (moving it too much before it has fully chilled can break the gel structure). Allow to chill for at least 4 hours. The yogurt will continue to firm as it cools.
Making Greek Yogurt (Straining)
To turn standard homemade yogurt into Greek-style strained yogurt:
- Line a colander with a double layer of cheesecloth or a clean muslin cloth and set it over a bowl large enough to catch the whey.
- Spoon the chilled yogurt into the cheesecloth. For a thick but still creamy result: strain for 1 to 2 hours in the refrigerator. For very thick yogurt similar to labneh: strain for 4 to 8 hours or overnight. The yogurt will reduce to approximately 50 to 60% of its original volume.
- Transfer the strained yogurt to a jar or container. Use within 1 to 2 weeks.
Troubleshooting
| Problem | Likely cause | Fix |
|---|---|---|
| Yogurt hasn't set; still liquid | Temperature too low; dead starter; too short fermentation time | Verify temperature; use fresh starter with visible active cultures; ferment for longer |
| Yogurt is very thin and watery | Milk not heated before fermentation; semi-skimmed milk used | Heat to 82°C before cooling; use whole milk; strain to thicken |
| Whey separating at the surface | Normal; occurs particularly in homemade yogurt without stabilisers | Stir back in; or drain off; not a fault |
| Very sour/acidic taste | Over-fermented; too long at fermentation temperature | Reduce fermentation time; refrigerate earlier |
| Grainy or curdled texture | Milk too hot when starter added (bacteria killed partially); over-acidification | Cool to below 46°C before adding starter; reduce fermentation time |
Perpetuating the Culture
Each batch of homemade yogurt can be used as the starter for the next batch: reserve 2 tablespoons before the batch is consumed and store in a small jar in the refrigerator (use within 7 days as a starter, or freeze in 2-tablespoon portions for up to 3 months). After several generations, the culture composition shifts and the flavour may change slightly; refreshing with a commercial live yogurt every 4 to 5 batches maintains culture diversity and consistent flavour.
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