One of the end of day rituals I most clearly remember growing up was the process of mixing and setting a bowl of yoghurt for the next day. I forgot about this little tradition for a while when I started living on my own after graduating and starting my own design practice. Supermarket-bought commercial brands of yoghurt made going through the motions of setting one’s own seem quite pointless and not worth the effort.
I eventually did start setting my own yoghurt, since I realised that the two quantities I would get at my supermarket would always end up being way too much or too little for my day to day usage.
Before we dive into the nitty-gritties of setting yoghurt, I’m going to quickly cover what the whole process entails, from a biological point of view. The conversion of milk into yoghurt is the work of a few varieties of Lactobacillus bacteria. They basically consume the lactose (the disaccharide sugar present in milk) and convert it to protein and lactic acid. The lactic acid is what gives yoghurt its characteristic tang. I think different strands or varieties of Lactobacillus produce subtly different varieties of yoghurt. I’d recommend purchasing a small quantity from your local dairy or from a restaurant that serves fresh, nice tasting dahi on the menu, the best of which I’ve come across have been in Udipi restaurants. All you’d need to “acquire” would be about a teaspoon’s worth. I’d recommend taking a little zip-lock bag with you the next time you visit an Udipi restaurant. Bag some like you’re secretly bagging forensic evidence. Good luck with that.
I tried using commercial varieties, but I’m pretty sure they add pima and other thickening agents to it, which ends up giving you very flaccid and unhealthy looking yoghurt. The variety of Lactobacillus they use (and this I found in more than one brand) results in a terribly slimy, stringy sort of yoghurt. This happens because the bacteria (the particular variety they use) exist in long strands, or have elongated polysaccharide complexes along their outer casing.
I put about 300ml of milk to set overnight. This is how I do it:
The list of needed items is quite small. You need:
300ml milk (toned/whole milk, whichever your arteries prefer)
½ teaspoon yoghurt (dairy-bought or from a restaurant, keep in mind a lot of restaurants use commercial yoghurt, that’s not the type you want)
Ceramic or glass bowl.
Crock pot or any heavy bottomed vessel big enough to contain the bowl with space to spare; should have a lid.
Put the empty bowl in the crock pot or vessel and fill the space outside the bowl with enough water to bring the water level just about a quarter inch below the mouth of the bowl. Remember this quantity of water so you won’t have to measure it this way every time you do this.
Heat the water to scalding temperature (this is exactly what it sounds like..not hot enough for it to bubble or boil, but hot enough to make you want to pull your finger away quickly when you dip it in the water). Once you put the water to heat, spoon the half teaspoon of yoghurt into the bowl, with a few tablespoons of the milk. Stir or whisk the little lump of yoghurt into the milk with a small spoon till its completely dissolved. Pour in the rest of the milk and stir. Place this in the hot water bath inside the crock pot or vessel and close the lid.
I recommend a heavy bottomed vessel to retain the heat a little longer than usual. Be careful not to get the water too hot, because that might end up killing the bacteria or scalding your fingertips when you place the bowl of milk-yoghurt mix into the vessel.
Let this sit for around 8-10 hours. Re-heat the water when it cools down in a few hours. The warmth keeps the Lactobacillus cosy and warm so that it does its job extra quick.
I usually mix the solution up around midnight, wake up in the morning and re-heat the water around 8 or 9 am and put it in the fridge to set around 10 or 11. Yes, I know that amounts to nearly half a day of setting, but I always have curd that’s practically thick enough to cut with a knife.
A few more tips:
- Do not use more than the specified quantity of “seed culture” (the half teaspoon of yoghurt). This will not speed up the process they way you’d want it to, it’d just result in an overfermentation with the Lactobacillus multiplying to much too soon. Think of a slowly filling up theatre for a play and an overcrowded, busy train station…which do you think would smell better?
- The warmth is what keeps the process active, even in places where the temperatures drop well below 20°C. I heat the water up more often during the winter months. Too much heat will kill the bacteria and cook the yoghurt, so keep an eye, or a fingertip in this case, on the temperature.
- Pick the initial strain from a restaurant or dairy where you like the taste of the yoghurt. Udipi restaurants serve it set in little vessels, so you know that its freshly set, not spooned in from a tub of commercial yoghurt.
- Run a knife through the yoghurt before you spoon it out of the bowl, if you’re looking for those large, chunky, iceberg-like blocks of yoghurt.
- Using warm milk does help speed up the process.