That mystery can of food or home-canned jar found in the deepest recesses of the pantry is a topic of many kitchen encounters during the COVID-19 stay-at-home orders. So when and under what conditions is an expiration or "sell by" date meaningless? We consulted food and nutrition experts to get the final word on safety regarding home-canned foods and store-bought canned foods. There are surprising answers as to what foods are safe to eat past a "sell by" date.

Related: 30 Cheap and Easy Recipes From Canned Foods

How should we interpret the 'best by' dates on canned goods?

Food and nutrition expert and consultant Amanda Webster cautions: "These dates are on the very strict end of the spectrum. It is also worth noting that the age of food is not what makes you sick, it is whether the food becomes contaminated. If they taste, look and smell fine, they pose very little danger. Most 'best by' dates have little to do with food safety and more to do with food quality and are provided by the manufacturers, not by any overseeing organization. They're meant to let the consumer know how long they can guarantee optimum freshness and taste."

How long does canned meat last?

Maya Feller is a registered dietitian nutritionist who says: "According to the USDA, canned meats should be stored in a cool and dry place. Canned meats can keep their best quality for two to five years."

What about properly stored canned meats eaten after their expiration date?

Feller says, "When stored in a cool and dry place canned meats are safe indefinitely. Cans with visible signs of damage such as dents, rust or swelling are not safe to eat." And the absolute longest you can safely keep canned foods if stored in a dark, dry pantry? She says: "Indefinitely."

How long is canned crab meat good for?

Getty Stewart is a professional home economist who educates the public on safe handling of food, including how to decide if canned food is safe or not. Stewart says: "If cans show any sign of dents, punctures, swelling or rust, do not eat, regardless of the 'Best If Used By' date. If the container bursts open or the crab meat looks or smells off, do not eat. When stored in a cool, clean, dry place and cans are in good condition, canned crab meat will retain good quality for three to five years. As long as the can is in good condition, it will be safe to consume indefinitely."

How long do canned dairy, custard, coconut milk and puddings last past expiration date?

Stewart says, "All commercially canned foods, regardless of what's in the can, will be safe to eat indefinitely as long as the cans are in good condition. However the quality — color, texture, flavor and nutrient content —  of the food inside the can will change at different rates. Dairy products, high-acid foods like tomatoes and tomato products will start to lose quality after about 18 months."

Related: Food Expiration Dates and Food Freshness Labels Explained

Types of home canning and preservation

There are three approved methods of canning for home food preservation. Pressure canning, water bath canning, and atmospheric steam canning. All use heat to ensure food in sealed jars is hot enough to destroy bacteria. Meats and low acid foods need pressure canning for best preservation.  Use a boiling water bath or atmospheric steam canner for all high-acid foods.

Related: Thinking About Home Canning? Here's Everything You Need to Get Started

Sodium awareness with canned foods

Webster adds that canned foods can have health concerns other than age. She says, "Many brands of canned beans have up to 1,000 milligrams of sodium per cup. Soaking and rinsing only eliminates a few hundred calories at best and the ideal daily limit is 1,500 for adults. Even the low-sodium options can have up to 400 milligrams per serving. Add spices and herbs for flavoring instead."

Rules of thumb when opening an expired can

Kevin Smith, senior adviser for food safety in the FDA's Center for Food Safety and Applied Nutrition, advises people to "routinely examine foods in their kitchen cabinets or pantry that are past their 'Best if Used By' date to determine if the quality is sufficient for use." The FDA further recommends that if the food items have changed in "color, consistency or texture," people should avoid eating them.

Do food pantries take expired canned foods?

Some will and some won't; you will have to directly enquire. The rule of thumb is, if the can is rusted, dented or bulging, it must be tossed out. Feeding America lists all major food banks by state with contact information you can call to ask if you are unsure.