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Roughly 2 percent of Americans are Jewish, and only a small fraction of them keep kosher. Yet between one-third and  one-half of all packaged food in an American supermarket has a kosher label on it. How did kosher law become big business? Join us this episode as we find out how ancient Jewish dietary laws have shaped and been shaped by the science of processed food, from Coca-Cola to Jell-O and beyond.

The definition of "kosher" is simple: It means "fit and proper." But deciding which foods are kosher for Jews to eat is anything but straightforward. Following a handful of basic statements in the Torah (the five books of Moses), such as which animals are unclean, rabbis have spent thousands of years and written millions of words arguing about such questions as whether honey is kosher, despite the forbidden bee legs that accidentally get caught in it, or how long to wait after eating meat before consuming milk.

For Roger Horowitz, author of the new book Kosher USA: How Coke Became Kosher and Other Tales of Modern Food, these debates were personal: His own family was split on the vexed question of whether sturgeon was fit and proper. (In short: Under Jewish law, only fish with fins and scales are kosher. Sturgeon seem to have scales, but they are so deeply embedded in the fish's flesh that scraping them off with a knife is impossible—so do they still count as scales? Jews have debated this question for more than a millennium.)

Arguing over sturgeon scales is one thing, but, as Horowitz points out, “at least a fish could be looked at and examined.” What about products with multiple ingredients, many of which are invisible and unidentified? This is exactly the dilemma 20th-century American rabbis faced, when their congregants, eager to enjoy all the processed pleasures of the modern food system, began plying them with questions about the kosher status of Campbell's soup, or the popcorn at the movie theater. Suddenly, knowledge of kosher law was no longer enough; rabbis needed to understand science and engineering.

Through the stories of how Coca-Cola became kosher, how Jell-O became treif, or non-kosher, and how the first kosher label was invented, we see how Jewish life has adapted to industrial food, and how industrial food helped shape American Judaism in return. But we also see how this niche set of concerns has had an outsized impact on the food we all eat, from ingredient sourcing to the rise of food labeling. From economics to ethics via traceability and assimilation, the contents of American grocery store shelves make an entirely new kind of sense when viewed through the lens of kosher law. Listen in to find out why.


This article appears courtesy of Gastropod, a podcast co-hosted by Cynthia Graber and Nicola Twilley that looks at food through the lens of science and history.

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