A vacuum is simply the absence of air. We can create a vacuum in a plastic bag or
container by sucking out all of the air and then sealing it to prevent air from leaking
back in. The single most important reason for creating a vacuum is to remove oxygen
from around the thing that we are going to store. This is because:
1. Air is made up of about 21% oxygen. Most bacteria associated with food spoilage
need oxygen to grow. The less oxygen that is available, the slower bacteria will
grow and the longer food will last before spoiling.
2. Oxygen is a highly reactive element and many of the organic compounds that
give food its flavour will react with it and make the food taste stale.
There are some other things to consider and these are dealt with later in this eBook, but removal of oxygen is the most vital.