Sign up for Weekday J and get the latest on what's happening in the Jewish Bay Area.

When is this unprecedented surge of interest in kosher foods and products going to wane?

It's a question most appropriately addressed to Joan Nathan, the award-winning Jewish food writer, who visited the Bay Area last month to promote her new cookbook, "The Jewish Holiday Baker."

Nathan is the ultimate source on such matters.

She is also the author of "The Jewish Holiday Kitchen," "The Children's Jewish Holiday Kitchen" and "Jewish Cooking in America," which won the IACP Julia Child Award for Best Cookbook of the Year in 1995 and the James Beard Award for Best American Cookbook.

Because kosher food has become associated with other trends favoring healthy lifestyles, Nathan predicts that interest won't cool off anytime soon.

"Kosher is no longer weird," Nathan explained, sipping a diet Coke in a cozy booth at Saul's Deli in North Berkeley. "It used to have a negative connotation." That's no longer so, she said. The prevailing sentiment today is that to be kosher is "a cut above."

Certainly there is mounting enthusiasm for the subject among Jews in the process of rediscovering their heritage. But it isn't observant Jews who have launched kashrut into the national spotlight, Nathan said, adding that there is little evidence of a growing number of kosher-keepers. Vegetarians and Muslims, whose dietary laws also forbid pork products, comprise the fastest-growing segment of the market for kosher products.

They are attracted to the idea that "we answer to a higher authority," added Nathan, quoting the slogan of one of her sponsors, a producer of kosher meat products. Such a slogan is just the sort assurance of cleanliness and purity that these people demand from the foods they buy.

Nathan's presence in the deli seemed to affirm kashrut's elevated status. Since flying in from Washington, D.C., where she resides, she had been rushing to speaking engagements throughout the Bay Area. Yet, despite her tight schedule, she made an unplanned visit to Saul's to scope out a location for her 26-part television series, "Jewish Cooking in America with Joan Nathan," which is to air on public television stations throughout the country starting around Rosh Hashanah and concluding the following Passover.

Clearly, the national appetite for Jewish food is voracious, and, as Nathan has discovered, eclectic as well, for she has already embarked on a new project that takes her outside the diverse Jewish American repertoire.

Next up is "Foods of Modern Israel," in which Nathan will emphasize the Jewish state's penchant for "salad-oriented" and fast finger foods. But she will not confine her definition of Israeli cuisine to the Jewish population. In her own view, Nathan is as much an "enthnographer" as she is a food specialist. "The Jewish Holiday Baker," for example, pairs life stories with recipes from a baker's dozen of Jewish bakers. In the same appreciative spirit, Nathan's Israeli cookbook will include the kitchens, stories and savories of Israel's Bedouins and its Christian and Muslim Arabs alongside their Jewish counterparts.

Given the country's disparate cooking styles and brief history, does the author think she will be able to discern a distinctive Israeli cuisine for her readers?

"I think they're still defining themselves," she said of Israel's cooks.

Good thing Nathan will be there to help us make sense of it all.