What Is Rotting? — Who Makes Kimchi and Makgeolli

Rotting and ripening are the same thing

The answer first: they are the same event. The small neighbours from piece 1 are eating. They eat the sugar in milk; they eat the sugar in cabbage. As they eat they give off sour things, smelly things, and gas.

The difference is who ate, and whether we can eat what is left. When it goes a way we can still eat, we call it fermentation. When we cannot, we call it rot. To the microbe both are just lunch.

The fizz in the kimchi jar

First the cabbage is salted. This is the first job. Most microbes cannot stand salt. But one crowd likes it: the lactic bacteria. The salt is not there to make cabbage salty. It is a doorman choosing the guests.

The lactic bacteria that pass the door eat the sugar in the cabbage and radish. After eating they give off something sour — that is why kimchi sours. They also give off gas. That is the fizz when you open the lid, and the tingle on the tongue.

Why does kimchi sour more slowly in the fridge? The bacteria are not dead. They are cold, so they eat slowly. A kimchi fridge is a machine for setting the bacteria's eating speed.

Makgeolli — a drink that works twice in one jar

Wine is easy. Grapes already hold sugar. A small neighbour called yeast eats the sugar and gives off alcohol and gas, and that is that. One step.

Makgeolli is made from rice, and rice has no sugar. It has starch. Starch is a long chain of sugar beads strung together. Yeast cannot eat the chain; its mouth is too small. So makgeolli needs one more worker.

That worker is nuruk, a cake of crushed wheat left to grow mould. The mould snips the starch chain into sugar. Then the yeast eats the sugar and makes alcohol. Mould cuts, yeast eats — and both happen at once, in the same jar. Wine works once; makgeolli works twice.

Makgeolli is a living drink. The yeast keeps eating after bottling. That is why it foams when opened, changes taste with time, and keeps only briefly. Shake it and it turns cloudy: rice particles and yeast rising again. Few drinks in the world are drunk cloudy. This one is drunk with its workers still in it.

A letter from the brewery

In the 1850s brewers came to a French chemist. Their drink kept turning sour. He compared good batches and sour ones under a microscope. The good ones held round things — yeast. The sour ones had rods mixed in. Another neighbour had moved in, eaten the drink, and left something sour behind.

Here he found something important. Fermentation is not a chemical change that happens by itself. It is the work of living things. And spoiling is the same. So keep the unwanted neighbour out: warm the liquid gently and kill it. The word 'pasteurised' on your milk carton is this man's name.

One question remained. Where do these neighbours come from? People believed that broth left standing grew them by itself. He ended that with a flask whose neck curved like a swan's. Air could enter, but dust caught in the bend. The broth stayed clear for months. Tilt it so the broth touched the bend once, and it spoiled at once.

A little further in

If nothing rotted

Rot sounds like a bad thing, but without it the world stops. If autumn leaves did not rot, forests would drown in them. If dead things did not rot, there would be no soil. Microbes break the dead down and return them to soil and air. In that soil the next cabbage grows. The last piece of this series tells that story in full.

Kimchi's lactic bacteria, makgeolli's mould and yeast, the bacteria that spoiled the milk. Four neighbours in one piece. We called them all microbes — but how different are they? A mould and a bacterium differ as much as a person and a tree. And one has not appeared yet: the thing that gives you a cold. The virus. Next piece.

The question that remainsIf what we call ripening is really microbes eating — who made the kimchi, the person or the bacteria?