How to Tell If Milk Has Gone Bad

A sour smell, unexpected curdling or a change in appearance can indicate spoiled milk. However, normal appearance and smell do not prove that milk is safe. Do not taste suspect milk or try to make it usable by boiling it.

How Can You Tell If Milk Has Spoiled?
Do not use milk with a distinctly unpleasant smell, unexpected texture changes, mold or damaged packaging. Curdling in a hot drink is not a reliable safety test on its own. Consider how and for how long the milk has been stored, its date label and the instructions for use after opening. Microbes that cause food poisoning do not always change the smell or appearance.

How Should Milk Be Stored?
Promptly refrigerate milk sold chilled after shopping; keep it at or below 4 °C / 40 °F. For unopened products suitable for storage at room temperature, follow the package instructions; do not apply that storage condition to opened milk. After opening, close the lid and return the milk to the refrigerator after each use. Do not leave milk that requires refrigeration at room temperature for more than two hours, or one hour when the temperature is above 32 °C / 90 °F; discard it if that limit has been exceeded even if it smells normal.

How Long Does Opened Milk Keep?
There is no several-day or one-week period that applies to every milk product. Follow the product's storage and use-after-opening instructions. A use-by date concerns safety, whereas a best-before date concerns quality; do not confuse them. Do not use a smell check to approve milk past its use-by date.

Common Mistakes
Checking only the date, relying only on smell or assuming boiling can compensate for improper storage is not sufficient. Noting the opening date and buying a pack size suited to your needs can help you use the product within its stated period. Do not use milk whose storage history you are unsure of.