The story, supposedly shot with a hidden camera, was broadcast on Beijing Television and relayed nationwide by China Central Television.
It also created a buzz on the internet, with chatroom users expressing shock and disgust.
Zi's footage appeared to show a makeshift kitchen where people made bao zi, or traditional steamed buns, stuffed with 60 per cent cardboard that had been softened by a bath of caustic soda and topped up with fatty pork and flavouring.
|The court heard that Zi paid four |
migrant wokers to prepare the buns
The Beijing court heard that Zi paid four migrant workers from China's northern Shaanxi province to prepare the buns according to his instructions, Xinhua said. The buns were then fed to dogs.
China has stepped up its efforts to reassure trade partners amid international criticism over contaminated products such as toothpaste and seafood.
Chinese officials have blamed foreign media for exaggerating the issue but have also admitted there is a serious problem with food hygiene and safety standards in the nation of 1.3 billion people.
But some netizens have expressed scepticism over the government's allegations and believe Zi's story was authentic.
"Baozi with cardboard in them have been around for many years already, how can this be fake?" a posting on the Sohu.com website said.
Another on the website tianya.cn said: "Anyone who uses their nose on this one would know that the report was definitely real.
"They're addicted to fooling the people, and it really seems like they think the people are idiots!"