She took a dim view of chefs and writers who did not do the same, and her criticism could be withering. “They’ve not done the travel and the research that I’ve done,” she told Saveur. “None of them, not one. I have traveled this country, wandering — it’s why I’m not rich! — and taking time, and nobody else has done that. Nobody else has seen a certain chile at a certain stage in a market in Chilapa, and then gone back in six months and seen other chiles.”

Ms. Kennedy relocated permanently to Mexico in 1976, living first in Mexico City and later in an adobe house she built near Zitácuaro, about 100 miles west, where she gave intensive cooking classes.

Information on her survivors was not immediately available.

She continued to write such essential cookbooks as “Recipes From the Regional Cooks of Mexico” (1978), “The Art of Mexican Cooking” (1989), “From My Mexican Kitchen — Techniques and Ingredients” (2003) and “Oaxaca al Gusto: An Infinite Gastronomy” (2010).

In a food memoir, “Nothing Fancy: Recipes and Recollections of Soul-Satisfying Food” (1984), she interspersed such decidedly non-Mexican dishes as cold jellied tongue, Iranian broiled lamb and crumpets.

In 2020, she was the subject of a documentary, “Diana Kennedy: Nothing Fancy,” directed by Elizabeth Carroll, who followed Ms. Kennedy as she cooked and taught in her solar-powered home. The Times called it “a lively and uncritical portrait of a woman as passionate about composting as chilaquiles, one who will pitch a fit if you put garlic in your guacamole.”

In her later years, Ms. Kennedy worked with the National Commission for the Knowledge and Use of Biodiversity, known by its Spanish acronym Conabio, to record and digitize her collection of recipes, drawings and notes on both Mexican cuisine and the country’s native edible plants.

In 2010, she gave The Chicago Tribune a terse assessment of her work. “I am tenacious,” she said. “And I love to eat.”

Christine Chung contributed reporting.