Yoghurt (joghurt, yogurt, jogurt) and how to make it

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We can put a man on the moon but we can’t fix a spelling for cultured milk. My mother made it. Indian friends made it. Making yoghurt has been a fact of life for me.

Yoghurt in pots in the supermarket was invented fairly recently, by Isaac Carasso in 1919. He called his company Danone. I make my own yoghurt and never really thought about it. Recently I looked on the internet and found only yoghurt recipes that involve sterile pans, control of temperature, precise times, and generally make it all look rather difficult.

Let me share a yoghurt recipe with you. Go to a good supermarket and get a carton of milk with some kind of resealable cap, and a small and expensive tub of plain (unflavoured) live yoghurt; I’ll call this the starter culture and I’ll explain later why it should be expensive.

The milk will be cold. Heat it for two minutes in the microwave, still sealed in the carton. Shake the milk. If it feels cold to the touch through the carton, put in for another two minutes. Now wash your hands carefully, open the carton, pour off a little of the milk (into some tea perhaps) and pour in half the tub of starter culture (eat the rest with fresh figs, grapes, sliced peaches, or blackberries). Reseal the carton and shake to mix.

Now leave the milk for 24 hours in a warm place. What’s ‘warm’? Anything that isn’t cool; put it in the boiler cupboard, or take it to bed with you, or just leave it wrapped up in a blanket (don’t forget to wrap around the bottom of the carton, too). Yoghurt is a living thing which produces ‘body heat’. If it’s well-wrapped and starts off warm, it’ll actually stay warm by itself.

After 24 hours the milk should have gone gloopy. Refrigerate and eat whenever you like. That’s it.


  • If the yoghurt separates out (straw-coloured liquid) then your ‘warm’ was actually my ‘too hot’. Try again.

  • If the milk goes slimy, or nothing happens, then your starter culture was not live or wasn’t expensive enough; another bacteria took over (see below). Don’t use a flavoured yoghurt! Try again.


Why should the starter culture be expensive?

Cheaper ‘live’ yoghurts may use slower-growing cultures because these last longer on supermarket shelves, but they won’t grow quickly enough to make yoghurt from scratch.

Should I add salt?

This isn’t just for taste; yoghurt-making bacteria tolerate salt well whereas some ‘bad’ bacteria don’t. By adding salt you give the ‘good’ bacteria the edge.

Is yoghurt healthy?

They say so. I personally find it easier to digest than e.g. milk. Debate continues whether live yoghurt does or does not protect your gut flora (the ‘good’ bacteria living in your digestive system). My understanding is that yoghurt will make no permanent difference; it does have a temporary effect but only by displacing the gut flora (not by adding to it), so the benefits are debatable. However, if you’re on antibiotics then I say eat the stuff, it helps. Of course it’s also a cure for thrush, athlete’s foot, and other infections, and a great moisturiser. At least, so I’m told.

Is home-made yoghurt safe?

Yes, at least when I make it. There’s an easy test: if the result looks, smells, and tastes like yoghurt, then it is yoghurt. If it looks, smells, and tastes like slime, old feet, cheddar cheese, or stilton, then the it might be edible — cheddar and stilton are fermented milk too — but it isn’t yoghurt. Just as I ask for no reward for your pleasure if you read this essay and make good yoghurt, so I accept no liability if you read this essay and it goes wrong. If you harm yourself or somebody else — that’s tough cheese.

What is yoghurt?

Yoghurt is milk that’s been partially digested by yoghurt-making bacteria. The bacteria eat lactose (human readers need a gene for the enzyme to digest this, without which they are milk-intolerant) and convert it to lactic acid — that’s the sour taste. It’s an anaerobic process, which means that it does not require oxygen, so can happen without air, e.g. in a special sealed yoghurt-making machine. Other examples of anaerobic processes are: conversion of ethanol to acetic acid (wine turns to vinegar), in tired muscles (glucose sugar converted to lactic acid in muscles short of oxygen), and conversion of glucose to ethanol and carbon dioxide (bread-, beer-, wine-, and spirits-making).

We take all this for granted now but it’s high technology; it’s just very old high technology so it’s cheap. Good.