Most of us have ancient packages of food stowed away in our kitchen cabinets that we just won't eat - or throw out. Either we've forgotten these relics exist or, like Chicago's Elizabeth Castro, we can't reach the top shelf without a stool.

"If something has been in there for a while, it loses all its appeal," said Castro, 38, who routinely ignores an unopened can of Campbell's vegetable soup from 2001.

But should the recession worsen - and pantry shopping become a necessity - Castro could eat her 8-year-old soup, even though it has long passed its "best-by" date, according to Martin Cole, director of the National Center for Food Safety and Technology at the Illinois Institute of Technology. As long as the can isn't damaged, dented, rusted or leaking, the issue is usually quality, not safety, said Cole.

To find out whether other non-perishables really do live forever, we dug deep into our own kitchen cabinets and rounded up our own pantry lurkers. Then we invited Cole to tell us whether we should eat these products or toss them out.

Here's a closer look at what he found:

Del Monte Lite Sliced Peaches

• Best by: July 31, 2008

• Expert assessment: Over time, canned fruits and vegetables first lose their flavor, followed by the color, texture and nutritive value. "Fruits tend to stand up longer in terms of quality." The shelf life ranges from one to three years. Try it.

StarKist Chunk White albacore tuna in water

• Best by: May 18, 2007

• Expert assessment: Canned foods that have been sterilized with heat - which destroys enzymes - are some of the safest products to keep. Try it.

Mashed potatoes

• Best by: No date. The owner purchased them in 2001 and moved them with her to Chicago from Washington, D.C.

• Expert assessment: The flakes are too dry to support the growth of microorganisms. No sign of bugs. Try it.

Brazos Legends Wild Peach Salsa

• Best by: no date

• Expert assessment: "If you hear a 'click!' when you open it and it still smells like salsa, it's probably OK," Cole said. Try it.

La Preferida Chile Chipotles

• Best by: March 2005

• Expert assessment: "There's rust on the outside, so put it in a plastic bag and trash it. Don't open it or handle it." Damaged or improperly canned food may contain Clostridium botulinum (which causes botulism). Toss it. Immediately.

Bisquick Complete Mix Buttermilk Biscuits

• Better if used by: Feb. 1, 2007

• Expert assessment: Some of the fat content might be rancid or have lost flavor. It's not a safety issue, though quality is uncertain. Try it.

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Edible or iffy?

• The "best before" or "use-by" date on canned and dried food is usually an indication of quality rather than safety; it's there to tell you when flavor, texture or nutrition value begins to decrease. Food companies are not required to date their non-perishable products.

• When checking food, use your eyes, nose and common sense. If the container is damaged or rusty, throw it out.

• Do not mess around with expiration dates on refrigerated items.

• High-acid canned foods such as tomatoes, grapefruit and pineapple can be stored up to 18 months. The can linings might discolor, but as long as the can is in good shape, it's probably safe to eat. Low-acid canned foods (meat, poultry, fish and most vegetables) will keep two to five years, as long as the can is in a cool, clean, dry place.

• Dried spices can be kept for a long time - whole about three years and ground about one - but they lose their potency.

• Products that have more water content - jams, cereal bars and syrups - get moldy when they spoil. "Don't scrape the mold off and eat the food," said Cole. "Mold can produce mycotoxins." The same holds true for cheese, unless it's molded deliberately like blue cheese.