It's kimchi-making season in South Korea, with households across the country preparing and laying down stocks of the ubiquitous spicy side-dish for the coming winter.

But many foreign visitors, including the most intrepid foodies, will probably leave without ever tasting a Korean-made version of the national dish of fermented, chili-soused cabbage.

That might be hard to believe for those who watched Wednesday as around 3,000 women wearing surgical hats and masks with rubber gloves and aprons, gathered outside Seoul city hall for a mass kimchi-making exercise.

In just four hours, they churned out 250 tonnes of kimchi that will be distributed to low-income families throughout the city.

Despite such prodigious feats of production, Korean kimchi is not that easy to come by in the country of its birth -- to the extent that it imports more of the pungent dish than it exports.

Apart from upscale restaurants, most food outlets in Seoul and other cities serve Chinese-made versions of the side-dish which, in its classic form, comprises salt water-marinated cabbage flavoured with a mix of powdered chili, salt, garlic, ginger and spring onion.

This is because Chinese kimchi is far, far cheaper, with a wholesale price of around 800 won ($0.75) a kilo (2.2 pounds) compared to 3,000 won for the homemade version.

And that huge price differential is largely responsible for what, since 2006, has become known as South Korea's "kimchi deficit."

Last year, South Korean kimchi exports totalled a record $106.6 million -- 80 percent of it bound for Japan, according to the Korea Agro-Fisheries and Food Trade Corp. (KAFTC).

But imports were even higher at $110.8 million -- with 90 percent coming from China -- for a deficit of $4.2 million.

That figure is expected to double in 2013, and already stood at $10 million at the end of September, partly due to a fall in exports to Japan because of the weak yen and strained relations between Seoul and Tokyo.

With the exception of 2009, South Korea has run a kimchi deficit every year since 2006.

Many see this state of affairs as an affront to the cultural heritage of a country where pride in the national dish cannot be overestimated.

South Korea boasts a global kimchi research centre, a kimchi museum and an annual kimchi festival -- and a fermented serving was even blasted into space with the country's first astronaut in 2008.

"It's regrettable that the locally made kimchi is disappearing at local restaurants," a KAFTC official told AFP.

"There have been concerns about food safety regarding made-in-China kimchi, and some restaurants fake the origin of their kimchi to customers," he said.

While something of an acquired taste, the side-dish has begun to make inroads overseas, beyond established Asian markets like Japan and China.

A flush of national pride was triggered in February when US first lady Michelle Obama tweeted a recipe for White House kimchi.

And the dish is widely expected to be given the official UNESCO stamp of honour as an "intangible cultural heritage" when the UN cultural body meets in Baku next month.

But for the women involved in Wednesday's event at City Hall, such advances are overshadowed by concerns that the tradition of communal, homemade kimchi production is in danger of dying out.

For generations, families and neighbours have gathered together in November to make the winter kimchi and share out the fruit of their joint efforts.

But changing family and social structures in a rapidly modernising country mean that the practise is becoming less prevalent, especially among younger South Koreans.

"It's sad that our traditional culture is disappearing like this," said Jin Hae-Kyung, her plastic gloves glistening with red chili sauce.

"I'd like our children to learn how to make it, just so they know this is how their grandmothers and ancestors have made delicious, fresh homemade kimchi for centuries," she added.