Adventures in yogurt-making

[igenlode]

I looked at prices for a 'food flask' to replace the Thermos I was using solely for the purposes of making cheap yoghurt, and they cost about twenty pounds; I'd have to save an awful lot of money on commercial yoghurt (and be a lot inherently fonder of the stuff than I am) in order to justify that.

So I did a bit of looking-up on the Internet as to whether it was possible to make yoghurt by keeping it warm in the oven, say, and saw someone suggest a 'Dutch oven'. And I had a brainwave that it might be possible to use my really big earthenware pot; I can't heat it on top of the stove, but pouring boiling milk into it would both act as part of the necessary cooling-down process and help to transfer the reservoir of heat energy to the pot. Unfortunately it is so big that I had to use rather more milk than I would normally have done, i.e. more than a commercial yoghurt-pot full!

I let it cool down -- probably rather too much, as I got distracted on the computer -- and put in two tablespoons of yoghurt instead of just rinsing out the bottom of the pot as usual, and left it for about four hours to see what would happen. Nothing. There was just cool-ish milk with some grainy lumps of old yoghurt at the bottom.

I decided I'd probably let it cool down too far and that the pot didn't retain the heat adequately, put the entire pot in the microwave (where it just fitted) and reheated the milk to warm-but-not-painful -- I don't have a thermometer, but then neither did the women who used to do this -- wrapped the pot in a couple of towels, and left it to stand again. About midnight I unwrapped it and had another look. The pot had cooled down but it was still full of liquid milk.

One final attempt overnight: I heated the pot for three minutes at 440W, which is the setting I'd normally use to raise a single mug of milk to 'hot but not boiling' for drinking purposes, made a nest of four towels in a cardboard box, and left it for eight hours or so. Considerably to my surprise, when I opened the box this morning the milk had all yoghurted. Not the sort of grainy set yoghurt I'd been getting previously (and that I had put in as 'seed material'), either, but thick creamy yoghurt like the stuff in the shops.

According to my reading on the Internet, you're supposed to get a more creamy result by heating the milk slowly rather than quickly to boiling point in the first place; I have no idea if it was the multiple reheatings or the rate at which I initially warmed it, and whether I had simply failed to leave the yoghurt long enough on previous occasions, but this time it worked. (The milk was no longer warm and hadn't set, so I doubt that simply leaving it longer would have worked, but we'll never know.)

Anyway, I've now demonstrated that it is possible to make yoghurt in my remaining utensils without a continuous heat source, given sufficient insulation... now all I have to do is find sufficient containers to hold a litre rather than a pint of yoghurt!

Comments

[capri0mni]

*Nod* when I was a teenager, we had a dedicated yogurt maker, which was basically a countertop thermostatically-controlled heating unit with four wells that each held a pint-sized glass container (so you were making the yogurt in the same containers you'd store them in).

So after the milk was inoculated and cultured, it was kept at a steady temperature. And it always took about eight hours to fully set.

(Yeah, the yogurt maker was an extra gadget we probably didn't need, but it freed up the oven for bread making. And this was the 1970s, when yogurt was still fringe culture [Hey!], and gadgets were trendy)

[igenlode]

That's good to know -- so I need to aim to keep the pot insulated for a whole eight hours.

And I found an old plastic takeaway container which had been pressed into service as an auxiliary biscuit box, and which will serve quite adequately in the fridge to contain the extra yoghurt...

[capri0mni]

here's a recipe I found for homemade yogurt, using general equipment.

Bear in mind it was written for an American audience, and all the the temperatures are in Fahrenheit the range they give for keeping the yogurt culture for that time translates to ~43 to 44 C.

(You can see why yogurt started in desert, nomadic, cultures, where keeping warm things warm is easy.

[igenlode]

In the absence of a cooking thermometer none of the temperatures really mean anything to me anyway and I've no idea how hot 44C is: my mental scale goes from 0C = freezing and 100C = boiling where water is concerned, via 'less than 50F = too cold indoors' and '60-70F = comfortable jumper wearing weather', '70-80F = summer clothing needed' and 'more than 80F = too hot outdoors'. The 'butter thermometer' in the kitchen is pretty accurate over the narrow scale of human comfort, like an alcohol thermometer as versus a mercury one: butter too hard to spread means that it is uncomfortably cold, butter at spreading but still solid temperature (like today) means that you can sit around in your shirtsleeves -- the thermometer in here reads just on 70F, which is pleasantly comfortable -- and butter that squishes or looks oily means that it is too hot indoors :-(

So 115F actually sounds very hot, although it clearly isn't...

The yoghurt temperature scale I was going by was the one that says 'heat until just below boiling', i.e. when you get fine bubbles but not a roiling boil, then cool until it feels lukewarm but not hot, i.e. just above body temperature.

I suspect that On the back of the kitchen range was probably the normal method for this sort of thing in countries like Russia which have a tradition of cultured milk products and little sunshine -- but yes, I imagine that yoghurt, like butter, was the accidental result of carrying milk around without preserving facilities.

(My mother used to tell horror stories of carrying milk from the farmer around all day on camping trips, and discovering when it came time to pour it into the tea that it had revolting yellow butter bits floating in it: whole-cream milk, of course, and the jiggling up and down in a rucksack was enough to churn it en route.)

[capri0mni]

110F is in the range of "Ideal bath/shower temperature" for me on a winter day, when I need to get my feet warm when they've been stubbornly cold all day: hot enough to make my skin flush, and steam up the bathroom mirror, but below the risk of scalding/burning.

(in other words, a good bit above lukewarm, and a good bit below boiling).

So it sounds like the recipe you're using is going by a different method...

[igenlode]

It may not be that far above; human body temperature is only just under a hundred degrees, after all, and the descriptions of various people's Turkish mothers making yoghurt all involved them testing the temperature on the back of their wrists, the way people do for a baby's bathwater.

I could never understand why a 'normal' internal temperature sounded so incredibly high in terms of summer heat -- presumably because we don't normally run around naked?

[capri0mni]

I could never understand why a 'normal' internal temperature sounded so incredibly high in terms of summer heat -- presumably because we don't normally run around naked?

Mostly, it's because our skin temperature is considerably lower than internal body temperature (that's why we hold thermometers in our mouths and not against our wrists).

And our bodies keep from overheating by letting our internal heat escape through our cooler skin (which is sped up when our sweat evaporates). When the air outside us is just as hot as our internal temperature, we can't do that, and we get uncomfortable, and sometimes, die.

[watervole]

I suspect it began in desert cultures as a way of increasing the shelf life of milk.

[watervole]

Towels are surprisingly useful for cookery. We often cook rice that way. If you get the right amoutn of water, you can simmer it for a minute or two, then turn the ring off and pile towel on top of pan and end up with lovely fluffy rice that has soaked up all the water (and you can't burn the rice this way, even if you forget it)