A vacuum pack machine removes the air from a bag and then seals it shut. With less air, the food keeps fresh longer and the pack is smaller and easier to store.

1. You put the food in a vacuum bag.
2. The machine draws the air out with a vacuum pump.
3. It heat-seals the bag while the air is gone.

• Chamber vacuum machines: the whole bag goes inside a chamber, and the air is removed from the chamber and the bag together. This gives a strong vacuum and works for liquids and wet foods, so it's the professional choice.
• External vacuum machines: only the open end of the bag sits in the machine, which draws the air out through the bag opening. They're simpler and cheaper, and better for dry foods.

• Butchers, fishmongers and kitchens storing meat, fish and prepared food.
• Sous vide cooking, where food is vacuum sealed and then cooked in a water bath.
• Marinating, and portioning for freezing.