For Jews and gentiles alike, the concept of kashrut—or kosher law—can often be a murky subject. Taking the podium at the Jewish Community Center in Manhattan earlier this month for a Culinary Historians lecture, Roger Horowitz—the author of Kosher USA: How Coke Became Kosher and Other Tales of Modern Food—recalled an orthodox woman who allowed her husband to eat pork sausage in the house, but only over a piece of newspaper. Another similarly observant woman would permit her daughter to snack on pizza every Sunday, just as long as she kept it in the basement.

“It’s not about dos and don’ts; it’s not the Ten Commandments,” Horowitz told the crowd, as a handful of men and women sipped cups of Manischewitz wine and snacked on salted Israeli chocolates. “You can follow different rules, I think, and still consider yourself Jewish. Now some people will say, ‘You’re not doing it right.’ Well, that’s part of being Jewish. We like telling people what’s right and what’s wrong.”

There has often been heated debate between the Ashkenazi and Sephardic traditions when it comes to which foods are and are not kosher (sturgeon’s status, for example, continues to vary depending on who you ask). In America, adherence to kashrut tends to wax and wane with assimilation. But just as the new world let some Jews feel less guilty about the occasional slice of pizza in the basement, kosher law has also greatly influenced the evolution of the American food industry over the last 100 years. Through his work, Horowitz—a historian and food expert with the Hagley Museum and Library in Delaware—has been able to chart just how kosher cuisine became a symbol of food safety and health standards in mainstream America following the waves of Jewish diaspora.

Non-Jewish consumers saw Kosher products as a guarantee of clean, quality ingredients, paving the way for organic labeling in the 21st century.

Surprisingly, Kosher’s long trek out of religious dogma and into supermarkets begins with one of the country’s oldest and most iconic brands: Coca-Cola.     

“Coca-Cola filled a sort of interesting place in our own rituals. Coke was not something we had at home all the time in our fridge. Coke was something we had at Shabbat dinner and on Passover,” Horowitz explains. “I began to wonder, how could Coke become kosher? What was the story in which Coke could become acceptable?”

Though Coke had been targeting the Jewish community in advertisements since the prohibition era in the 1920s, along with brands like Aunt Jemima and Uncle Ben’s, it wasn’t until an orthodox rabbi named Tobias Geffen came along that the company received official kosher certification. A prominent religious leader in Atlanta, Georgia, where Coke’s production facility was located, Geffen was tasked with examining every ingredient in the company’s recipe after receiving hundreds of letters from Jews around the country. Ultimately, Geffen was the first rabbi to use chemistry and science to determine a product’s kosher status, and convinced Coca-Cola to switch from using a non-kosher, animal fat-based glycerin to a vegetable-based glycerin.

In the 1930s, the majority of observant Jews would continue to turn to ethnically Jewish companies like Manischewitz for their food products. But by the 1950s, 80 percent of those buying Manischewitz wine were actually gentile, and soon large national companies began to follow Coke’s precedent. Not too long after, a more cohesive, nationwide certification was developed, and a wider array of household products were given kosher trade symbols if they met the requirements. At a time when food safety regulations had yet to truly take hold in America, non-Jewish consumers saw Kosher products as a guarantee of clean, quality ingredients, paving the way for organic labeling in the 21st century.

“[In the 1980s], only one-in-four consumers of kosher foods are Jews, and by 2000, it’s one-in-10,” says Horowitz, pointing out Muslim and lactose intolerant shoppers, who want to be reassured that dairy and pork products aren’t mixing with their food. “There’s a general sense that if you have these orthodox rabbis looking at this stuff, there’s another set of eyes and it’s going to be more reliable.”

“These rabbis are strict,” he adds. “You can trust them.”