Foods maintain their texture and appearance, because microorganisms such as bacteria mold and yeast cannot grow in a vacuum.

Freezer burn is eliminated, because foods no longer become dehydrated from contact with cold, dry air.

Moist foods won't dry out, because there's no air to absorb the moisture from the food.

Dry, solid foods, such as brown sugar, won't become hard, because they don't come in contact with air and, therefore, can't absorb moisture from the air.

Foods that are high in fats and oils won't become rancid, because there's no oxygen coming in contact with the fats, which causes the rancid taste and smell.

Insect infestation is eliminated, because insects require oxygen to survive and hatch.

Meat and fish will marinade in minutes when vacuum packaged in canisters, because as air is being removed from the canister, the pores of the mat or fish open up and allow the marinade to penetrate.

Food bills are reduced because food lasts longer (so less spoiled food will need to be thrown away), and because food can be purchased in lower-priced bulk quantities and re-packaged at home into smaller portions.

And non-food items are protected from corrosion and moisture-damage. Like your antique silverware, which won't tarnish when vacuum packaged. Or wool sweaters, to keep bugs away, and to shrink them for minimal storage space.

These systems consist of a small manually-operated pump which can be used to extract air from canisters and bottles only. They do not usually indicate when a vacuum has been achieved.

Although they do not completely remove the air from the container, they do help food last longer. Glass or glazed ceramic containers work best.

Bag sealers with a fan.

These systems utilize small rotary fans to extract some air out of plastic bags before they are sealed. Some systems include polyethylene bags. Others provide sheets of plastic from which bags of different lengths can be made by "welding" the seams with a heated wire bag-sealing mechanism.

The fans don't have enough suction to create a vacuum. The amount of air removed is comparable to using a straw to suck air out of the bag. The plastic will shape itself loosely to the contours of the food in the bag, but it will be obvious that air remains in the bag. The type of bag material (polyethylene is best) and the strength of the seal will determine whether oxygen is able to re-enter the bag.

Less-air is better than out-in-the-air. Remember, however, that plastic does breathe, so storage life will be limited.

Electric pump systems.

These are the only storage systems that eliminate exposure to oxygen. They are also the most expensive, of course.

They utilize electric-powered piston pumps to extract air from the container, and seal with container to prevent air from re-entering. And, ideally, they indicate when a vacuum has been achieved.

When food is vacuum packed in bags, the effect of the pump is highly visible, because the bags will shape themselves tightly around the food. Not so when vacuum packed in a jar, which is when a vacuum gauge is most helpful and will keep the jar from imploding.

In order to maintain the vacuum, containers are constructed of special materials which provide an oxygen barrier.

Vacuum packaged food will taste fresher and last longer than food stored in conventional containers.

 But because the food is not devoid of moisture or potentially lurking pathogens, it is important to remember that vacuum packaging is not an alternative to refrigeration.

Of course you don't need to refrigerate vacuum packaged cereal. But you do have to refrigerate meat, dairy and other products that require it.

Shelf life of vacuum packaged foods