Is Fermented Food Safe? The Science of Safe Fermentation

Is fermented food safe? Leaving vegetables at room temperature to change on purpose can sound risky. Done properly, it is one of the oldest ways to preserve food, and here is the science of why.

Fermented, not spoiled

Fermentation is not rot. It is a controlled process in which salt, acidity and the right microbes create conditions that are hostile to unwanted bacteria. People around the world have used it to preserve food for thousands of years, long before anyone understood the microbiology behind it.

The three guards of a safe ferment

Three things stand guard in a good ferment. Salt sets the environment, lactic acid bacteria produce acids that lower the pH, and that low pH makes life very difficult for the microbes that cause food poisoning. Working together, they make the jar an unwelcoming place for harmful bacteria. Read more about the role of salt in lacto-fermentation.

How to tell if a ferment has gone bad

A healthy ferment smells sharp, sour and clean. Off or rotten smells, a slimy texture, or fuzzy, coloured mould are the rare signs to stop and start again.

The old rule holds: when in doubt, throw it out. In practice, with enough salt and acidity, it rarely comes to that.

Why we don't pasteurise

Pasteurising would kill the very cultures that make a ferment special. So instead of heating our kimchi, we keep it cold, fresh and alive from our lab to your fridge. It takes more care, but those live cultures are the whole point.

Done properly, fermentation is one of the oldest and most reliable ways to preserve food. In a very real sense, the sourness is the safety.