The word "aseptic" means the absence or exclusion of any unwanted organisms from the product or package. Examples include microbes, spores and other elements which can cause food to spoil and affect our health.

In an aseptic carton, all that is good stays in, while nothing harmful, such as light, air or bacteria, can get in. Hence, even the most perishable products, such as milk, can stay fresh for many months without the need for preservatives or refrigeration (until opened).