While western countries such as the United States worry about the tide of cheaply produced consumer goods flooding their markets, Chinese products are quietly flooding into the global food supply as well.

A pizza crust consumed in New York will probably contain l-cysteine derived from Chinese hair strands. It was a small part of the worldwide amino acid market, which was forecast to reach US$7.45 billion this year and $9.73 billion in 2009, Freedonia Group said.

'China is the biggest food additives producer in the world today,' said Krishna Kumar, managing director at industry researcher Giract. 'There's hardly any area [of the market] they are not looking at.'

Mr Krishna said mainland producers first entered the ingredients market as suppliers of bulk goods such as glucose syrup, which could account for as much as 25 per cent of a food product.

Chinese suppliers then quickly moved up the value chain into 'low-dosage' speciality ingredients, which appeared in small quantities and served a specific purpose. In the case of l-cysteine, it is to make dough more elastic.

There are as many as seven suppliers of l-cysteine in the Shanghai area alone, and dozens more across the country, which rely on barber shop clippings for hair.

One such firm is Golden Harvest Fine Chemical, although a company official said it was switching to cheaper duck feathers and pig hair. It sources its human hair from a Suzhou-based collection firm.

Due to the gross-out factor, food producers are unlikely to tell customers they are consuming a product derived in part from hair.

'Human beings don't like to be told that. You have to be very delicate,' Mr Krishna said.

Food labelling laws vary from country to country. In markets with tough rules, the ingredient may appear as l-cysteine or l-cysteine hydrochloride. But even then, it may not be clear whether the baking agent comes from human hair or another source, such as chicken feathers. In other places, the package label may simply note the use of a baking agent but offer little other information.

Although the mainland is the world's largest source of l-cysteine, there appears to be little awareness of this among consumers. In January, China Central Television created a stir when it reported on a Hubei company that made a soya sauce ingredient from human hair.

China has not always been the top source of human hair for amino acid production.

That title once belonged to the world's second-most populous country, but like other industries such as software outsourcing, India has felt pressure from its neighbouring competitor.

Indian Hair Industries managing director Vank Ravindra said three years ago he had no problem selling barber shop cuttings from India to mainland customers.

The market changed after amino acid producers began to source human hair domestically.

'There's no more demand for barber hair from India. They're buying local hair,' he said. 'It's very cheap, less than one [yuan] per kilo of hair.'

Three years ago, a tonne of barber clippings fetched US$400, but the price had dropped to less than $100 today, he said.