By Michael Bristow
BBC News, Changpin County, Beijing
Hygiene is a top priority at the Changpin farm
Winters in northern China are cold, and nothing much is growing in the bare, brown earth.
But it is a different story at a farm in rural Changpin County, just north of Beijing.
Its greenhouses are full of vegetables, including peppers, pumpkins and tomatoes.
The farm is owned by one of the 36 companies that have been selected to supply food to athletes at this year's Olympic Games in Beijing.
It is a model farm that uses few chemicals, has on-site product testing and employs an electronic tagging system to track its vegetables.
That is why it has been selected as an Olympic supplier.
At a time when the world is increasing concerned about Chinese products, the last thing the country wants is an Olympic food poisoning scandal.
A worker at the Changpin farm inadvertently revealed just how determined China is to avoid serving Olympic athletes with tainted food.
As she packed vegetables, the employee suddenly realised she was not wearing the hat that keeps her hair away from the vegetables.
She quickly put it on before farm manager Lin Yuan could see her.
Hygiene is a topic that it is close to Mr Lin's heart, and he seems annoyed that foreigners often question the safety of Chinese food products.
"Some of the foreign media are biased against Chinese vegetables," he said.
He told the story of what happened recently while he was having dinner with a Japanese banker friend.
"A friend of the banker's called from Japan and asked him how he was surviving because Chinese vegetables aren't edible," recalled Mr Lin.
"Says who? I eat them every day," the banker apparently told his compatriot.
'Number one issue'
Mr Lin's Japanese friend may have been supportive, but the story reveals just how many foreigners are wary of Chinese food products.
And many of those people are preparing to come to Beijing for the Olympics.
"I think this is the number one issue facing our (Olympic) teams," said Mike Tancred, media director for the Australian Olympic Committee.
In order to prevent any food-related problems during the event, the Australians have advised their athletes what to eat, and what not to eat.
"We have recommended they do not purchase food from street vendors outside the Olympic village," said Mr Tancred.
Potatoes at Changpin farm are labelled 'delicious and safe'
The Australians are also bringing some of their own food, and have told athletes only to drink water supplied by Olympic sponsor Coca-Cola.
Despite the precautions, Mr Tancred revealed that a number of Australian athletes have become sick while taking part in Olympic test events in Beijing.
Back at the Changpin farm, Mr Lin oversees a complicated system that aims to make sure no disasters happen during the real event in August.
For example, vegetables are grown in special soil that reduces the need for pesticides and fertilisers, although most products do not meet official "organic" standards.
The farm produces 17 tonnes of vegetables a day, with most destined for foreign-owned or upmarket supermarkets in Beijing.
In order to produce the best vegetables, the company has sent officials on study trips to Australia, Japan, Canada and the United States.
Manager Lin says the company has prepared well for the Olympics, but even he admits he cannot guarantee everything.
"I worry about things I can't control, like the weather. I also worry that the products I use regularly, like pesticides, aren't up to standard," he said.
Unsurprisingly, given the high stakes, Mr Lin confesses he often has sleepless nights. He is not the only one.
Kang Yi, the woman in overall charge of catering at the Olympics, has also endured restless nights.
"I felt stressed at the start. So much stress I couldn't even sleep," she told the BBC.
"But then I realised the Chinese government is really paying attention to this issue and that's when I felt the pressure lift a bit."
Ms Kang is in charge of a system that will track Olympic food from farm to fork using the Global Positioning System.
Most of this food will be grown on farms around Beijing, like the one in Changpin County. But some of it will come from other provinces, and anything China does not produce itself will be imported.
It will be served up at Olympic venues by US catering firm Aramark, which has dished out dinners to athletes at 13 other Olympic Games.
China is anxious for the Olympics to run without a hitch
Like farm manager Lin, Ms Kang is sensitive when people suggest China's food is not up to scratch.
"I think the sheer volume of media reports last year about China's food safety problems are due to the fact that China's media is more transparent," she said.
"The Chinese government is confident about food safety" is a message the Chinese repeat over and over again, even on labelling.
Potatoes being packed at the Changpin farm carry a simple label that reads: "delicious and safe".
Foreign athletes, judges and spectators in Beijing for the Olympics will hope that proves right.