The Chinese ministry of commerce said in a statement on Monday that the three firms had dumped disodium 5'-inosinate, disodium 5'-guanylate and gisodium 5'-ribonucleotide - all used as flavour enhancers - on the market, damaging its own domestic industry.

It said that an investigation launched in 2004, prompted by Shanghai-listed Star Lake, had found evidence of a connection between "dumping of the investigated commodities and the injury of domestic industry".

In the first half of 2004, the investigated products captured 64 per cent of the Chinese market, and reached volumes of 18,046 tons, according to the ministry of commerce. This was a 131 per cent increase on the same period in the prior year.

However prices had dropped by 84 per cent in 2002, a further 15 per cent in 2003, and by 26 per cent in the first half of 2004, it said.

It has imposed a 25 per cent duty on Daesang while the other two firms face tariffs of 119 per cent. The duties were imposed from 12 May and will last for five years.

It is not the first time these companies have been subject to investigation. At the end of 2002 the European Commission fined the three companies for running a nucleotides cartel in the 1990s.

Ajinomoto, Daesang and South Korea-based Cheil Jedang were respectively fined €15.54 million, €2.28 million and €2.74 million each.

An employee in Daesang's export department said China is not its biggest market but represents a significant portion of its export sales. He declined to reveal the volumes sold in China.

Applications for nucleotide seasonings - largely produced from tapioca starch - include instant noodles (soup), soups and bouillons, seasoning mixes, and other processed foods, all seeing increasing demand in the Chinese market.

Daesang estimates the global market of ribonucleotide to be around 15,000 MT per year.