1. Start simple.
Salted vegetables is probably the easiest project for beginners. Salt inhibits the growth of bad bacteria and encourages lactobacilli growth. Basically, the process involves chopping crunchy vegetables such as cabbage, onions, and carrots, salting them liberally, pounding them to release their juices, and packing them in a crock or jar. (See our recipes for simple sauerkraut and kimchi).
2. Keep it clean.
The key to fermentation is to encourage the growth of good bacteria while preventing bad bacteria and mold. Make sure hands, tools, workspace, and containers are clean before you begin, and keep fermenting foods away from compost or other sources of bacteria. Use clean utensils when stirring and tasting, and be sure not to "double-dip" to avoid bacterial contamination.
3. Watch your temperatures.
The ideal temperature for fermentation is 65-72°F. Too cool, and beneficial bacteria can't grow and thrive. Too warm, and spoilage sets in. Generally, fermentation readily occurs at room temperature. If you're not sure, invest in a simple thermometer and test your fermenting area.
4. Seal out air.
Beneficial bacteria thrive in an oxygen-free environment, so your fermentation procedure should keep oxygen away from food. Some fermenters rely on specialized equipment with fancy vacuum seals and other accessories. But people have been fermenting for centuries with nothing more complex than a Mason jar. Two key factors: First, be sure your food is completely submerged in brine. This allows lactic acid bacteria to develop and prevents the growth of harmful bacteria. Second, seal Mason jars with a lid, but be sure to allow at least one inch of head room for expanding gases. Some fermenters prefer to loosen the lid once per day to release built-up gases.
5. Pitch it if it's funky.
Here's the thing with fermented foods: if you did it wrong, it stinks. Literally. Your fermentation should have a light, clean, fresh smell and taste, with a little tang. Telltale signs that something's wrong: slimy texture, pink hue, browned or dried out vegetables, funky odor, white or creamy film, or mold. When in doubt, toss it out.