SAY this about Sandor Ellix Katz: the man knows how to get you revved up to eat bacteria.

“Oh, this is nice kimchi,” he said on a summer afternoon at Momofuku Noodle Bar, using chopsticks to pull crimson-coated knuckles of Napa cabbage from a jar. “I like the texture of the sauce. It’s kind of thick.”

Kimchi, like sauerkraut, is one of the world’s great fermented foods, and Mr. Katz, a resident of Tennessee, was curious to see what David Chang’s team of cooks in the East Village would do with it. Lately Mr. Katz has become for fermentation what Timothy Leary was for psychedelic drugs: a charismatic, consciousness-raising thinker and advocate who wants people to see the world in a new way.

A fermented food is one whose taste and texture have been transformed by the introduction of beneficial bacteria or fungi. And Mr. Katz, who turned 50 this year, considers it a big part of his mission to remind us that the tangy delights of that metamorphosis surround us — and always have, if you look back at the arc of human evolution.

“I don’t believe there’s a restaurant in the world that doesn’t have products of fermentation on their menu,” Mr. Katz said. “If you have bread, you have fermented food. If you have cheese, you have fermented food. If you have salad dressing or anything with vinegar in it, you have fermented food. If you have alcoholic beverages, you have fermented food. I mean, you really can’t get through the day without eating something fermented.”