how is curd formed - #42269

Curd is formed through the fermentation of milk by beneficial bacteria, primarily lactic acid bacteria. When you boil the milk and cool it, what you’re doing is prepping the environment for these microorganisms. The temperature of the milk should be just warm to the touch, about 110°F (43°C). If it’s too hot, it can kill the bacteria; too cool, and the bacteria won’t activate properly.

The magic here lies in the bacterial cultures, usually Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. These bacteria ferment the lactose present in milk into lactic acid, which then causes the milk to thicken and form curd or yogurt. Yes, in theory, if you leave milk out, it might eventually curdle due to bacterial action, but it wouldn’t be safe or controlled like using a starter.

For your runny yogurt, a few things could be tweaked. First, ensure the milk you are using is not too low in fat, as higher fat content tends to lead to thicker yogurt. You might also try using a bit more starter or a fresh batch of starter if you suspect the one you used wasn’t potent enough. Importantly, the fermentation time needs attention. Letting it sit longer, up to 8-12 hours, can help, but keep it in a warm, draft-free spot. In Ayurveda, the North or East directions are preferred for placing your fermentation process due to energy flows.

Check that the container is well insulated; wrapping it in a towel might help maintain a consistent temperature. Make sure the starter culture is evenly mixed before setting aside the milk to ferment. Good luck with your next batch, looks like you are on a flavorful culinary adventure!