There are hundreds of Korean pickles that fall under the kimchi moniker ranging from bland radish to explosively spicy squid but the main season for Kimjang (or kimchi-making) starts just before the onset of winter, both as cabbages come into season and the weather begins to cool to the perfect fermenting temperature of 5°C.

Traditionally, families would pool together to make huge quantities of the chili-laden pickle with a few hundred heads of cabbage enough to sustain the kimchi needs of a family for winter. The pickle would be buried in large clay jars to lengthen the kimchi's lifespan as well as develop their full fermented flavor. Most cities still have temporary cabbage markets for kimjang and it is not unusual to spot the earthenware jars used to age the pickle sitting on urban balconies in Seoul rather than underground in a more traditional manner. The advent of the kimchi refrigerator has however taken some of the impetus away from needing to pickle at any particular time of the year.

The average South Korean family eats almost a whole head of pickled cabbage a day, approximately 200 grams per adult. Apart from rice, there are few other national dishes that are eaten with the same addicted fervour at every single meal of the day. No meal is imaginable without it.

At its most basic, kimchi is made from cabbage, garlic, red pepper powder, spring onion, ginger and salt. From this simple concoction comes a product that has a fresh, crisp and intriguingly carbonated taste when younger; sourer and more pungent as it ages. There is chili aplenty and although many kimchi neophytes find it overpowering, after a few years of kimchi, you can barely notice the heat.

How on earth does kimchi ferment but not become godawful cabbage and chili vodka over winter? Where does that carbonated flavor come from?

Fermentation in kimchi is caused by the various microorganisms present in the raw ingredients, especially strains of heterofermentative lactobacillus - a group of bacteria that convert the sugars in the raw ingredients into not just lactic acid (which accounts for the sourness) but also considerable amounts of ethanol, acetic acid and carbon dioxide (which accounts for the carbonated flavour intrigue). They out compete most of the organisms that would turn those sugars into either cabbage vodka or botulism soup. The salt and cold also helps to suppress them - but not suppress them too much.

As the kimchi gets older, more lactic acid builds up accounting for the sourer tastes, and yeasts tend to get a foothold causing some of the pungency but also softening the texture of the cabbage. There aren't many fermented foods that have a more complex microbiological process underlying a relatively simple recipe for storing a seasonal ingredient.