Food - Drink
The Reason Sourdough Bread Takes So Long To Go Stale
What makes the hearty, tangy, typically robustly-crusted sourdough bread sour is the natural fermentation process that creates it. As it turns out, that same fermentation process is responsible for sourdough's long shelf life compared to other unfermented, commercial loaves of bread.
Per Consumer Reports, the fermented bacteria and yeasts that sourdough doughs incorporate from the flour and air pre-baking produce acids and other compounds, which leaven the bread and lend it its distinctive tang. Those acids stay intact after baking, warding off mold and keeping the bread from staling.
These naturally antifungal and antibacterial acids also make properly maintained sourdough starters (flour-and-water slurries) last for centuries. One example of sourdough’s long shelf life is from Italian chef and cookbook author Sara Papa, who claims to bake her loaves from a Milanese starter dating back to 1848.