Home-made Yogurt
I've been doing this for at least twenty years in the same wide-mouthed Thermos flask.
I've had it so long that the plastic screw threads for the lid have all broken off. :-)
But you can make yogurt in an ordinary, narrow-necked flask too, it's just a bit more awkward to wash.
And failing Thermos flasks, I have often made yogurt in a thick pottery bowl with a plate or saucepan lid as cover.
Anyway, on to the method: this is for one litre (my flask holds a litre, as do many containers, so it is a handy size.)
Heat a litre of milk in a saucepan until it is just below boiling point.
"Nearly-boiling" - the surface gets bubbles and shakes or shivers as if threatening to rise, but it does not.
This is easily the trickiest bit: over the years I have scorched pans and boiled over milk.
A large pan with a fairly heavy base works best: I usually rinse it out with cold water first - some kind of magic, LOL
I also use one of those milk-boiler disks - I don't even know why but the milk has not burnt or boiled over on me for years so something is working!
Of course, you can nearly-boil the milk in a bowl in the microwave too.
And if you dread the thought of the nearly-boiling, you can buy UHT milk which has been already scalded. Warm slightly, then use as is.
Back to the saucepan; watch it until at the nearly-boiling point, count to thirty as it shivers, and take off the heat.
Cool for about 45 mins until lukewarm.
How lukewarm is lukewarm? About 40C, if you care to test, or 100F, or less than this: not more.
You can test with a thermometer, if you have one - even a clinical thermometer as used for sick children, will do.
but I usually just stick a clean finger in.
If the milk is too hot, it may kill the bacilli. That feels like, a tang of hotness. Hot enough to wash hands in = too hot.
If stone cold, the bacilli will be slow to work and may not breed very much.
Any lukewarm kind of tepidness is right. Soup that is far too cool to drink? (Recipes often say "blood heat" but I can't tell blood temperature by feel)
Add to this lukewarm milk 2 good tablespoons of Glenisk Low-fat yogurt. Natural, organic. Say 30 or 40 ml.
Many other kinds of yogurt will work as a "starter" but I give here one that is very reliable and that I am pretty sure will work every time.
Whisk the yogurt into the lukewarm milk.
Preheat your flask by swirling a little hot water round in it, (pour this away); pour in the yogurt/milk mixture. Cover closely. Wrap in a few layers of woolly blanket or similar - I use sleeves cut off old woolly jumpers.
Place in a not-too-cold spot and DO NOT MOVE IT FOR AT LEAST FIVE HOURS. (Or overnight)
When the time is up, uncover and test to see if it has set: shake the container slightly, it should be jellyish.
If there is a little watery liquid visible at the edges, you may carefully pour off this whey. You don't have to, but the yogurt is a little thicker if you do. Be careful not to spill the whole batch down the sink if you do this delicate operation #voiceofexperience
Pour into a bowl, and whisk or stir thoroughly: it may appear quite thin and runny, or grainy, but should amalgamate and get smooth.
Cover and place into fridge and chill thoroughly. It is inclined to thicken as it cools, but may not "set firmly" in the manner of commercial yogurt.
Enjoy!
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Footnotes:
Yogurt is made from tiny living creatures so of course it can be unpredictable.
I have made yogurt using quite acid-tasting starter but the yogurt came out tasting bland and custard-like. In fact this is one of the commonest results, and not one that pleases me much, though children may like it.
My own taste is for yogurt that is not very sharp or sour but still has a "tang" - one that can be pleasantly paired with a little honey or fresh fruit: or alternatively, used in savoury cooking such as Indian food or salads.
Experiment with different cultures as starters - sometimes the result comes out tasting quite different than the starter - I don't know why but there are always surprises.
If you have no flask, you can use a pudding bowl: a thick one that will hold the warmth is best. Cover it with a warm plate or lid, and wrap carefully in a few layers of insulation.
Many people put this in eg an airing cupboard or near the boiler, to be sure it stays just warm enough. This is fine, though it really is important to NOT MOVE IT during the setting time. Five hours or more undisturbed in a warm spot.
With a flask it stays warm inside anyway, so that doesn't matter so much - I leave mine on the kitchen counter with a note pinned to it giving the finishing time and the warning "Not to be moved before 7.30!"
I took a stack of photos to illustrate this but most are currently inaccessible. These are the things I use.
Will answer all questions.
