Vacuum sealing is a popular method of food preservation that greatly extends storage times. Vacuum sealing also can protect non-food items such as manufactured goods, important papers and backpacking supplies from environmental damage. Vacuum packaging once was the domain of commercial processors, but in recent years machines for household use have come on the market.
Why It Works
Vacuum packing extends the shelf life of food products three to five times by removing the oxygen that normally would react with the contents to spoil them. It also retards growth of spoilage bacteria and keeps out mold, mildew and insects. Vacuum sealing preserves the normal moisture content of foods and prevents freezer burn, but it also keeps moisture away from items that must be stored dry. Vacuum sealing extends the shelf life of refrigerated and frozen foods but is not a substitute for cold storage. Vacuum-packed meats, dairy products and other foods that must be kept cold still have to be refrigerated or frozen to prevent growth of pathogenic bacteria that cause food poisoning.
One of the benefits of vacuum sealing is that you can buy foodstuffs in lower-priced bulk quantities and repackage them into meal-sized portions. The longer storage life made possible by vacuum sealing helps with food budgeting. For instance, frozen fish, cuts of meat and ground meat typically become freezer burned if kept in the freezer more than six months. But if they are vacuum sealed they can be kept frozen for two years with no loss of quality. Vacuum sealing roughly triples the cold storage or room temperature storage life of foods like flour, sugar, rice, hard cheeses, coffee, fresh fruits and vegetables, cookies, crackers and nuts.
Vacuum sealing machines sold for the home use special plastic pouches that can hold a vacuum and be heat sealed. After you fill the storage pouch, the machine clamps the open end of the pouch over a vacuum nozzle connected to a vacuum pump that sucks all the air out of the pouch. The machine then heat seals the pouch to preserve the vacuum and the pouch contents. Some models have an external vacuum port for vacuum-sealing items in containers. Most home vacuum sealing machines are meant to process solid items, not liquids.
Commercial vacuum sealing units employ a vacuum chamber with a lid rather than a vacuum nozzle. The item to be preserved is put in a pouch that is clamped to a heat-sealing bar within the vacuum chamber and the chamber lid is closed tight. A vacuum pump evacuates the entire chamber. The pouch is then sealed, air let back into the chamber and the sealed pouch removed. Unlike units with vacuum nozzles, vacuum chamber machines can process products that come in liquid or slurry form.
Original article from: http://www.ehow.com/info_12149455_vacuum-sealing-work.html