OSAKA — Duskin Co. has pledged to refrain from opening new Mister Donut shops until March following public outcry over the company's handling of a banned antioxidant found in its meat dumplings.

"We would like to concentrate on improving the quality of our products," Duskin President Takeshi Ueda told a news conference on Friday.

Duskin runs a franchise network of 1,319 Mister Donut shops. The company started the franchise in Japan in 1970 through a tieup with Mister Donut of the United States.

Sales at Mister Donut shops fell by an average 20 percent during an 11-day period starting May 21, after the presence of the banned additive t-butyl hydroquinone became public knowledge, Ueda said.

On May 23, police raided the head office of Duskin in Suita, Osaka Prefecture, and questioned Duskin executives and officials in charge of sanitary and legal affairs.

Duskin admitted recently it sold more than 13 million meat dumplings containing the banned additive in 2000.

Even after Duskin learned of the additive's presence, it withheld the information from the government for about 18 months and continued sales of about 3 million dumplings.