Considerations
Although the two are often confused, vacuum packing is different from so-called modified atmosphere packaging, which relies on an inert nitrogen atmosphere to delay spoilage of food items. Manufacturers must choose the plastic for vacuum packaging carefully, because not all plastics are equally impermeable to gas. Over time, air inevitably seeps back into the package, and delaying this process extends shelf life. A smaller surface area or a double-layer of packaging material helps reduce the rate at which air enters the bag.