For self-proclaimed “fermentation fetishist” Sandor Ellix Katz, fermentation is a subversive act. The age-old process—which involves preserving and metabolizing food by letting bacteria convert its starches and sugars into alcohol or acid, resulting in a distinctively tart taste—battles the pitfalls of big-factory food, cheap imports, and the fading away of elaborate, centuries-old culinary traditions. He details his wide-ranging experiences with, and reverence for, the practical procedure in his upcoming book, Sandor Katz’s Fermentation Journeys: Recipes, Techniques, and Traditions from Around the World (Chelsea Green Publishing), out next month. “Like any other manifestation of culture, fermentation practices must be used in order to maintain relevance and stay alive,” he writes. “We must cherish and celebrate the diversity of fermentation practices around the world, and document and share them.”