They are the first major sentences to be handed down in one of the worst food safety scandals in China in decades.

The Intermediate People’s Court in Shijiazhuang, in the northern province of Hebei, said the defendants had intentionally produced or sold dairy products laced with a toxic chemical called melamine, which was used to give falsely high protein readings but which caused kidney stones and other ailments in about 300,000 children last year.

Among those to receive the death penalty was Zhang Yujun, a dairy middleman who the government called one of the “principal criminals” in the scandal. He was convicted of selling 600 tons of melamine-tainted “protein powder” to dairy companies.

Another dairy producer, Geng Jinpin, was also sentenced to death. A third man, Gao Junjie, received the death penalty with a two-year reprieve, which means he could be spared execution.

Tian Wenhua, the 66-year-old former chairwoman of the Sanlu Group, one of China’s largest dairy companies, was sentenced to life in prison for her failure to stop producing and selling the tainted goods even after her company learned that the products were flawed.

Ms. Tian was the highest-ranking corporate executive to have been brought to trial in the scandal. She pled guilty in December to charges that she had acted improperly in the case and was also fined about $3 million. All the deaths in the milk scandal so far have been linked to Sanlu, which was found to have sold the milk products with the highest concentrations of melamine.

Three other former executives at Sanlu were sentenced to five to 15 years in prison. One of those executives, Wang Yuliang, had appeared at the court in Shijiazhuang in December in a wheelchair after what the Chinese state-controlled media said was a failed suicide attempt.

The tough sentences were the government’s latest effort to deal with a scandal that erupted last September, triggering a global recall of Chinese-made dairy products, shaking consumer confidence and devastating the nation’s fast-growing dairy industry.

But parents of some victims of the scandal protested Thursday afternoon outside the courthouse in Shijiazhuang, where Sanlu is headquartered, saying they were dissatisfied with the verdict.

“I feel sorry for them, but they are just scapegoats,” said Liu Donglin, 28, who says his 21-month old son suffered from kidney stones after drinking tainted milk powder. “The ones who should take the responsibility are the government, like the quality supervision bureau and the Health Ministry. I spent nearly $3,000 taking care of my son and the government only compensated me with $300.”

Some lawyers and victims of the scandal have accused Beijing of failing to properly regulate the nation’s dairy industry and some believe the government covered up the scandal before the Beijing Olympics last August, disclosing the news in September.

Former Sanlu officials acknowledged in testimony last month that they knew there were complaints and serious problems with their dairy products as early as May of last year.