Fermentation Store

A fermentation store is a room kept at a steady mild temperature so that vegetables, dairy or meat preserve themselves. Bacteria already on the food eat its sugars and turn them into lactic acid, and that acid stops anything else spoiling it. It needs no compressor and no pressure vessel, and costs little to run.

It is not a cold room, and building it like a cellar is the usual mistake. Sauerkraut works best at 21 to 24 degrees C (70 to 75 F), finishing in three or four weeks; at 16 to 18 degrees C (60 to 65 F) it takes about six weeks, below that it may not start, and above about 27 degrees C (80 F) the product goes soft and spoils. Salt is the other control, a safety setting and not a seasoning: about 2 to 2.5 percent of the vegetables' weight for sauerkraut, or a brine of 15 to 20 percent that must not drop below 12 percent as the ferment runs. Too little and harmful bacteria are not held back; too much and the ferment never starts. Everything must stay under the liquid, held down by a plate or filled jars, in a vessel that will not react with acid - stone, glass or food-grade plastic, never copper, iron, galvanised metal or lead-glazed pottery.

A ferment must run right through its succession of bacteria to reach a stable acidity; stopped partway it is sour, not preserved. What comes out will not keep in the room that made it, so the store is really two spaces - the mild room where the ferment runs and a cold place or a canner behind it. It pairs with a root cellar for what is not canned, and with a garden timed to deliver its glut of cabbages, cucumbers and roots. Upkeep is skimming the crock two or three times a week while a ferment is active, topping up brine, and reading a thermometer rather than trusting the walls. Soft product means too much warmth or too little salt, mould means something sat above the brine, and an off smell means discarding, not tasting.