Yogurt and Sour Cream

Yogurt and sour cream are cultured milk: bacteria have already soured them on purpose, which is why they outlast fresh milk and why a slightly sharper taste near the date is not the same as spoiled. They are fridge foods with no place in the deep pantry, but they earn a spot on this site for two reasons: a tub of live-culture yogurt is a starter for the next gallon, and in a short outage they are the first things worth eating.

Plain whole-milk yogurt with live and active cultures on the label, in the largest tub you will finish in two weeks. Flavored and fruit-on-the-bottom yogurts carry sugar and a shorter clock. Greek yogurt is the same milk with the whey strained off, so it holds its texture longer and freezes better. For sour cream, full fat keeps its body; the light and fat-free versions separate sooner. Skip anything with a dented or domed lid.

Back of the fridge, not the door, where the temperature swings every time it opens. Keep the lid on and use a clean spoon every time; a dirty spoon is how mold gets into a tub that would otherwise last. Once a tub is open, a piece of plastic wrap pressed onto the surface slows the watery whey and the skin. Yogurt can be frozen in the tub or in an ice cube tray for cooking later. Sour cream is better used up than frozen.

Mold on the surface or the sides of the tub, in any color, and the whole tub goes, because the threads run deeper than the spot you can see. Pink, orange or yellow patches are bacteria or yeast and mean the same thing. A thin layer of clear liquid on top is whey and is normal; stir it back in. A sharper, yeasty or bubbly tub that smells like beer has fermented past eating.

Plain yogurt is breakfast, a marinade that tenderizes meat, the base of a raita or tzatziki that stretches a small amount of meat, and a sour cream substitute everywhere. Two tablespoons of live-culture yogurt stirred into a quart of milk warmed to about 110°F and held warm for 6 to 10 hours is the next batch; save two tablespoons of that for the one after. Sour cream finishes soups, chili and baked potatoes and is the fat in biscuits and quick breads when the butter is gone. Neither one belongs in a 72 hour kit; both belong in the first day of a blackout, eaten before they warm.

A closed fridge holds under 40°F for about 4 hours. Yogurt and sour cream are among the first things to eat in that window, after the milk. Past four hours without ice, they are done; cultured or not, the rule for dairy above 40°F is two hours. If the freezer is still frozen, move the tubs there with the ice packs and they buy another day.

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.