Yogurt

Traditional Bulgarian Yogurt (Kiselo Mlyako)

Bulgarian yogurt (kiselo mlyako) is the original 'sour milk' that defined the modern yogurt we know today. The traditional method relies on two specific live cultures - Lactobacillus bulgaricus and Streptococcus thermophilus - that thrive in a long, slow ferment, producing a thick, tangy, slightly nutty yogurt quite different from the softer, sweeter supermarket style.

Prep

10 min

Cook

30 min

Total

40 min

Serves

makes about 1 litre

Difficulty

Medium

Recipe ingredients

• •1000 ml (4¼ cups) whole cow's milk, Fresh, full-fat (minimum 3.5% fat); do not use ultra-high-temperature (UHT) milk as it leaves yoghurt thin and pallid
• •30 g (2 tbsp) live Bulgarian yogurt, Must contain Lactobacillus bulgaricus and Streptococcus thermophilus; a small tub of authentic kiselo mlyako from a Bulgarian shop is the gold standard. Commercial homogenised yogurts often fail to set properly.

Steps

1. 1 Pour the milk into a heavy-bottomed stainless steel saucepan and heat slowly over medium-low until it reaches 82 °C / 180 °F, stirring occasionally so a skin does not form. This step denatures the whey proteins, which is what gives Bulgarian yogurt its characteristic dense body.
2. 2 Remove from the heat and cool the milk down to 42–45 °C / 108–113 °F. Use a clean food thermometer; cooling too far will stop the cultures, cooling too little will kill them. To speed this up, you can set the pan in a sink with a few centimetres of cool water.
3. 3 Spoon about 120 ml of the warm milk into a small bowl, add the 30 g of live Bulgarian yogurt, and whisk until completely smooth. This tempers the starter so it does not sink in clumps to the bottom of the pan.
4. 4 Pour the tempered starter back into the pan of milk and stir gently but thoroughly with a long spoon for about 30 seconds. Do not stir again.
5. 5 Pour the inoculated milk into a clean, heat-proof glass or ceramic pot (a 1-litre clay pot is traditional if you have one). Cover with a tight-fitting lid.
6. 6 Maintain the pot at a steady 42–45 °C / 108–113 °F for 6 to 8 hours. The traditional Bulgarian method is to wrap the pot in a thick woollen blanket or several clean towels and place it near - not on - a warm oven or radiator. Alternatively, use an oven with just the light on, or a yogurt maker.
7. 7 Check at 6 hours: the yogurt should be set (a spoon pushed in at an angle holds its shape) and smell clean, tangy, and slightly yeasty. If it still looks liquid, leave it for another 1–2 hours. Do not let it ferment past 12 hours or it will become unpleasantly sour.
8. 8 Once set, refrigerate immediately - uncovered for the first hour so a thin yellow film of whey can form on top; then cover. The yogurt will firm up further as it chills. It keeps for 5 to 7 days in the refrigerator.
9. 9 To strain a thicker version resembling Greek-style yogurt or the Bulgarian katak, line a sieve with muslin set over a bowl, spoon in the yogurt, and drain in the fridge for 2 to 4 hours. Reserve the whey for bread dough or soups.