From this vantage, soy-sauce packets appear not to be optimized for the substance they contain—a substance that, it should be noted, isn’t even technically soy sauce. Packaged soy sauce is often a cocktail of processed ingredients that resemble the real thing: water, salt, food coloring, corn syrup, MSG, and preservatives. But soy sauce, strictly defined, refers to a fermented combination of soybeans and wheat whose earliest direct predecessor was first mentioned in writing in the year 160. (Less-direct ancestors of modern-day soy sauce existed in China as far back as about 3,000 years ago.)

In the millennia since, arguments have brewed over what exactly constituted soy sauce. William Shurtleff and Akiko Aoyagi trace these disputes in their book History of Soy Sauce (160 CE to 2012). The manufacturers of traditional fermented soybean paste at one point banded together and, through a proposal authorized by the Japanese government, contested the right of companies such as La Choy and Kari-Out to call their products soy sauce. These old-school outfits outlined an elaborate classification system for varieties of the product. In the end, it was too hopeful, and the proposal was withdrawn in 2005.

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Even though the soy-sauce packet’s origin is an unsolved mystery, the story of how it became popular is not. That’s the story of Howard Epstein, who, as the founder of the dominant soy-sauce brand Kari-Out, is seen as the ambassador of packaged American soy sauce.

Epstein became interested in food packaging because his father manufactured the long, flimsy plastic packaging for freezer pops. Epstein's first venture into his father’s trade was a popcorn-packaging business, which he bought for $5,000 over 50 years ago.

That business failed to gain traction, and Epstein, now 81, was looking for a change when one of his father’s salesmen, who sold tea bags, suggested he consider the soy-sauce-packaging business. In 1964, Epstein founded Kari-Out, and he says he arrived to the industry right as it was becoming commercially viable. He ran his new business out of the popcorn factory he owned.

At first, Epstein was regarded with suspicion, primarily because he, a Jew from the Bronx, was different from most people in the industry. “No one trusted me because it was the old times. The Chinese ran the business,” Epstein says. His attempts to sell his packets to wholesalers were met with apathy and even cold-shouldered silence. “I had one potential customer,” he says. “I went in and asked him if he would be interested in selling my soy sauce. He didn’t speak. He never talked to me.”

But Epstein persisted, and his familiarity with freezer-pop packaging proved helpful in solving the problems with soy-sauce packets at the time: They leaked and they were too flimsy. “The only difference is a freezer pop has a much longer bag,” Epstein says.