Sour Cream

Opened sour cream keeps 1–3 weeks refrigerated, often past its printed date. Do not freeze it.

Store it on a shelf with the lid tight, not in the door. As with yogurt, serve from a spoon rather than eating from the tub — introducing saliva and crumbs is the fastest way to cut the window short.

Some people store the tub upside down, which creates a partial vacuum at the surface and slows oxidation and mold. It is a minor gain but a free one.

Sour cream separates on freezing and thaws watery and grainy, because the emulsion breaks irreversibly. It is salvageable in a cooked sauce or baked dish where it will be blended, and unusable as a topping.

Sour cream is cultured cream — cream deliberately fermented with lactic acid bacteria until the pH drops to around 4.5. That acidity is the preservative, and it works: below about pH 4.6 most foodborne pathogens cannot grow, which is why sour cream outlasts the cream it was made from several times over.

The tang is therefore not a sign of age but the product working as designed. Sour cream does not "go sour"; it starts that way.

What acidity does not prevent is mold and wild yeast, both of which tolerate acid environments easily. Mold is the practical failure mode, and because sour cream is soft and high in moisture, visible mold means discard the entire container rather than scooping off the spot.

Watery liquid on the surface is whey and is normal — the same separation that happens in yogurt. Pour it off or stir it back in.

The signals that matter are a sharp yeasty or fermented-alcohol smell, a fizzy texture, any mold at all, and pink or yellow discoloration. A pronounced increase in sourness beyond the usual tang also suggests the culture has run well past where it should be.