The Shanghai Food and Drug Administration registered more than 84,000 food-safety-related calls from concerned citizens in 2014.
The calls from informers almost doubled to 531, according to the report.
More than 28 percent of callers that give information about the anomalies in food handling and sanitation did not leave any information about themselves, that is why the authorities are having trouble in giving them due rewards.
An official also reported that although the anonymity of callers is guaranteed, many people do not leave details because of fear of reprisal.
It also reported that 60 percent of the calls in 2014 were food-safety issues, of which 66 percent were deemed accurate.
In January last year, the Chinese branch of Wal-Mart super stores issued a recall of donkey meat products after some of it was found to contain fox DNA.
In 2013, more than 10,000 dead pigs were found floating down a river in Shanghai that supplies tap water to the eastern Chinese city.
Public trust in food safety has been deeply undermined in China by the series of scandals, from contaminated baby formula to the widespread sale of "gutter oil" processed from garbage and scraps and sold to restaurants for cooking, Food Safety Tech website published.
In another case, a resident from an apartment building in the Pudong New Area called the 12331 hotline to report an illegal meat-processing business that is operating inside the building. The officials seized 1.1 tons of meat that contains Rhodamine, a chemical that is banned in food production.
More than 1,000 tons of contaminated pork and 48 tons of cooking oil produced from the meat have been seized across 11 provinces, according to the Public Security Ministry.
They also added that the seized products were valued at more than 100 million yuan ($16 million) and 75 suspects have already been jailed.