I have been making yoghurt for about 3 months now. I remember my Mum doing in the 70s or early 80s before plain yoghurt was so widely available.
I was prompted by our local (well 3/4 hour round trip) Sainsburys discontinuing the large pots of plain organic yoghurt. We try to do as much as is reasonable of our shop locally, milk, vegetables, fruit and meat, but had been doing a supermarket shop every 3 weeks or so, with the small tubs not only would the cost go up, but the fridge space occupied would be too much, especially with the vegetable glut season approaching… So I researched it on the net and got to it. Now I’m making yoghurt the supermarket shop has stretched to every 4 weeks or so, result!
You will need
a thermos flask, I have one for food with a plastic lining that I got years ago, you could use a ‘normal’ one but use a soft spatula to get the yoghurt out of the narrow neck.
a thermometer of some kind, a jam/sugar thermometer would be ok, I have an electronic one with a metal probe (also very good for jam and testing when a large piece of meat is cooked)
milk, I use organic, up to you, it can be skimmed or full fat, that depends on your taste and /or waistline!
some skimmed milk powder, optional, I have tried with and without, see notes later on
a dessertspoonful of live yoghurt (bought – any ‘probiotic’ one will work and once you have got going use some of your last batch).
It takes 1.5-2 hours to do, although you’re not busy all the time don’t start it just before bed!
It’s made in 12-24 hours, 12 hours gives a more mild taste, 24 slightly stronger. I tend to do it in the evening when I am in the kitchen anyway, then it’s ready the next morning (though still warm so not so good to eat straight away) and if I forget it in the morning we usually find it early in the evening when cooking.
Start by measuring enough milk (using the thermos) about 2 cm below the top, pour it into the pan. Add skimmed milk powder I have started to use 35g, the original recipe I read said 45g, if you don’t use any you will get a thinner yoghurt. Gently heat the milk to 85 degrees celsius meanwhile warm the thermos with a bit of boiling water put on the lid. When the milk is 85 degrees, pour out the water and pour in the milk quickly seal and leave for 30 minutes. If you forget it it doesn’t seem to matter. * see below
After 30 minutes pour the milk back into the pan, leave it to cool to 46 degrees, it takes about 25 minutes to cool, meanwhile keep the flask warm with a little boiling water and the lid on.
When the milk has cooled (if it cools too much just warm it very gently again), to 46 degrees add the dessertspoonful of yoghurt and stir or whisk, quickly empty the hot water from the flask and pour in the milk mix. Leave in the sealed flask for at least 12 hours, up to 24 hours.
When you are ready empty the contents into a bowl, whisk until smooth and transfer to a container and chill in the fridge, it doesn’t seem to separate even after a week or so, (it never lasts longer than that here). It is possible to strain the yoghurt at this point to get a thick more greek style yoghurt, I haven’t tried it yet, when I do I’ll add a section about that.
* It turns out that holding the milk for yogurt at ’about 85°C’ and ’holding it there for about half an hour’ both pasteurises the milk very thoroughly and ’denatures the whey proteins to some extent, unfolding the initially compact molecules into longer structures that increase the viscosity – thicken the texture – of the liquid. And in the case of yogurt, it results in a firmer gel that is less prone to separating into curds and whey.’ (thanks to Paul Marsden online for that brief synopsis of Harold McGee).
Things that can go wrong!
There is too much milk or froth that leaks out of the top of the thermos when you tighten the lid, just wipe off the excess, it might smell a bit of off milk, but shouldn’t get in the yoghurt when you pour it out.
I have forgotten the cooling milk and left it overnight. Warmed again, it seemed fine, though may have picked up some spurious bugs, I have refreshed my culture since by buying a fresh pot of Yeo Valley.
At about the same time the yoghurt went a bit grainy, I thought this may be because I had got a bit sloppy, heating it quickly and letting the milk boil, but it may not have anything to do with overheating… Maybe the extra bugs are what have been making us fart a lot! I thought it was an excess of peas and broad beans!
I hope this is useful, please comment if you have something to add…
Curing the graininess
So after a few more months of yoghurt making I think I have sussed out what was going on to make it grainy.
I have slowed down the heating up to 85 degrees and have made sure it NEVER goes above 85.
I have also found that cooling the milk in a sink of cold water is a great way to speed up the whole process. We have lovely thick and smooth yoghurt again.