The Life of Food

• While not technically living organisms, diary products have a shelf life -- how long they're safe to use. While some foods, such as oils, simply turn rancid and taste bad once their shelf life has passed, others, such as animal products and vegetables, become dangerous if eaten after decomposition has begun. Mold and bacteria that grow on food can cause foodborne illness, and they're not always visible.

The Dating Dilemma

• To educate people on the freshness of their products, manufacturers use date stamps on the outside of product packaging. For sour cream, manufacturers may use a sell by or best if used before date. The date indicates when the sour cream should be taken off the shelf at the grocery store. If stored properly, sour cream can be safely used for an additional two weeks past the stamped date.

The Cold Shoulder

• Because sour cream is perishable, handling and storing it correctly can help keep it fresh for longer. The biggest factor in prolonging the life of dairy products is refrigeration. Milk products left in the danger zone -- temperatures between 40 and 140 degrees Fahrenheit -- spoil within a few hours. Sour cream should be kept covered in the original container and stored in the back of the refrigerator for optimal shelf life. If you see mold on the sour cream, throw out the entire container.

Why Sour Cream Is Sour

• Sour cream is made by introducing "good" bacteria into fresh cream. The bacteria turn the lactose in the milk into lactic acid. Acid has a sour taste, and the more acid in a product, the more sour it will taste. These "good" bacteria help slow spoilage by changing the product's pH -- making it more acidic -- which makes it less hospitable to "bad" bacteria. This is why sour cream lasts longer than sweeter dairy products, such as milk or cream.