Soy Sauce

Soy sauce is a fermented brine, roughly 15 percent salt, and salt that strong preserves itself: sealed, it keeps indefinitely, and it's on the field guide's Indefinite 15. Opened, it slowly darkens and loses its aroma, and even then it's soy sauce. A bottle beside the rice bucket is the difference between a bowl of rice and a meal, and it is the cheapest umami there is for canned meat, beans and the soups that come out of a food store.

Naturally brewed soy sauce (the label says brewed, or lists only soybeans, wheat, salt and water) keeps longest and tastes best; chemically made soy sauce (hydrolyzed protein, caramel color) keeps as long and tastes flatter. Tamari is wheat-free and keeps the same. Buy in glass; the large plastic jugs are fine sealed but take on a plastic taste once opened for months. Low-sodium soy sauce has less salt and a shorter opened life; keep it in the fridge. A gallon per family per year is a generous stock.

Sealed bottles in a cool, dark cupboard. Once opened, the cap tight and the bottle away from the stove; the fridge holds the flavor longest but the counter is safe. Wipe the cap; a crusted cap is where the rare mold starts. It freezes without harm if that is where the space is.

Darkening and a flatter, less aromatic taste are age and oxidation, not spoilage. The sauce is done only if there is mold at the cap or on the surface, which is rare and happens when the cap sat open and dirty, or if it smells sour and off rather than salty and savory. Sediment at the bottom of a brewed sauce is normal.

A tablespoon in a pot of rice, beans or lentils replaces the salt and adds the savory depth that canned and dried food lacks; it's a marinade for canned or fresh meat, a dipping sauce with vinegar, a stir-fry seasoning and the base of a dressing with oil, all from the field guide's list below. A teaspoon in a cup of hot water with a pinch of sugar is a broth when there is none. It's also a brine: a cup of soy sauce in a quart of water with a little sugar cures a chicken or a pork loin overnight for the smoker.

Nothing changes; soy sauce is a pantry item in every climate. It is the flavor that keeps the rice and beans going in week three.

• Flavor enhancer
• Meat marinade
• Stir-fry seasoning
• Dipping base
• Dressing

Shelf-life figures are from the Survival Foods field guide; fridge, freezer and pantry times are from the USDA cold and pantry storage charts. Run the look, smell, taste check before eating anything past its date.