China's food safety watchdog is still open to proposals from the public and research organizations at home and abroad on gutter oil testing and identification, said a senior official.

Yan Weixing, secretary-general of the safety committee under the China National Center for Food Safety Risk Assessment, made the remarks after the Ministry of Health announced it was looking at four types of equipment and three quick on-site testing methods for the illegally processed oil.

But they still need further assessment and improvement, according to the ministry, which oversees China's food safety.

"It's still difficult for the methods and equipment to perfectly screen out potential gutter oil, though they have shown great promise," Yan noted.

Gutter oil is the generic term for cooking oil that has been used and then resold.

"We are still open to public proposals and ideas concerning the testing," he said.

In December, the ministry and the center began to solicit effective testing methods for gutter oil from the public and so far have received 762 related proposals, including 315 testing methods submitted by 281 organizations and individuals.

They include several from abroad, according to Yan.

"Given the extremely complex components of such oil, which also might vary from place to place, it's hard to figure out one single method to identify it," he explained.

He also pointed out that ensuring food safety cannot simply depend on testing methods.

"Instead, the authorities should constantly enhance supervision and management over the chain of food production and processing to avert food safety crises," he added.