Stephen Chen (left), Joyce Chen (center) and Helen Chen appear in a family photo together in the 1970s. Provided to China Daily

The mission to continue to popularize Chinese food fell to her children. Joyce Chen Restaurant closed in 1998, partly due to intensifying competition from a surging number of Chinese restaurants, some of them run by people who once worked for Joyce Chen.

The business, Helen said, was also too time consuming. "It is one of those businesses that are 24/7," she said. "You don't really have the family life that people who just work nine to five, Monday through Friday have."

Stephen is now running Joyce Chen Foods, a sauce, condiment and frozen food brand. Through co-packagers, the products are available in stores all over the United States.

"We try to be organic, gluten free, lower in sodium, all natural, all quality," he said. "My mother's name is on it, and I don't want to do anything to embarrass her name."

Helen was initially running Joyce Chen's cookware business, but sold it to a Chicago company in 2003, as more capital was needed to keep the company growing.

"At a certain point, many companies that have been established by families or individuals eventually sell," she said. "You just cannot keep on growing and growing, and just have the family run it. You can stop growing if you want, but the business will eventually fail."

Instead, Helen has written three cook books herself, and she created her own cookware brand, "Helen's Asian Kitchen", which is distributed by Harold Import Company in Lakewood, New Jersey.

Helen has also inherited her mother's idea of making the food business "not just a business, but a cultural exchange center". She is now teaching cooking at Boston University, and also giving classes to children interested in cooking with the help of a non-profit organization.

"I explain about the cuisine, but I also try to put together how the culture, the geography and history of China are really expressed in the food," she said.

She told China Daily that a lot of knowledge was behind food. For example, when Chinese people refer to meat, they usually refer to pork instead of beef. It is partly because of China's geography, with only around ten percent of land arable.

"The land cannot be put aside for grazing animals. We may have a lot of cows in the Mid-west and Argentina, but not in China," said Helen.

When the last of Joyce Chen's restaurants closed, Boston Business Journal said the "last pieces of the Joyce Chen empire fell."

Her eldest son Henry's retail store "Joyce Chen Unlimited" was closed in 2008 one year after his death. But Stephen told China Daily that what he and Helen are doing is "touching more people than having a restaurant".

"In a restaurant, you are limited by how many people can sit down. But now, we sell to supermarkets and cookware stores around the country. And you just gain a big audience," he said.

Both Helen and Stephen are continuing to spread Chinese cuisine and the culture behind it. "It's not just about passing on Joyce Chen, but the spirit of what she was doing, which is the legacy of the Chinese food culture, said Helen. "China is the only living old civilization in the world."

Lu Huiquan in New York contributed to this story.