When is a modified atmosphere needed?
With modified atmosphere vacuum packaging (MAP), the air is removed from the bag and a measured mixture of gases is added, which effectively contrasts the natural decay of the product, increases shelf life, controls the level of humidity and prevents the product from being crushed (e.g. fresh pasta).
At times, red meat may darken and this problem is counteracted by the addition of oxygen mixed with nitrogen and carbon dioxide, which helps preserve the colour for many days.