Food Preservation

Supermarkets are full of foods that have undergone one or more processes to delay spoilage. Refrigerators and freezers provide cold storage. Aisles of packaged goods are stocked with foods preserved by various methods, often with chemical additives to make them shelf-stable.

Excerpts from FSIS.USDA.gov  Shelf-Stable Food Safety

Foods that can be safely stored at room temperature, or "on the shelf," are called "shelf stable." These non-perishable products include jerky, country hams, canned and bottled foods, rice, pasta, flour, sugar, spices, oils, and foods processed in aseptic or retort packages and other products that do not require refrigeration until after opening. Not all canned goods are shelf stable. Some canned food, such as some canned ham and seafood, are not safe at room temperature. These will be labeled "Keep Refrigerated."

In order to be shelf stable, perishable food must be treated by heat and/or dried to destroy foodborne microorganisms that can cause illness or spoil food. Food can be packaged in sterile, airtight containers. All foods eventually spoil if not preserved.

Except for infant formula and some baby food, product dating — having a "use-by," "sell-by," or "best-if-used-by" date —
is not  required by Federal regulations. Dating is for quality, not safety. [Click to read more from FSIS.USDA about Food Product Dating.]

Will commercially canned goods last forever?  [NO!]

Commercial canning is done under tightly controlled conditions — careful sanitation and the necessary time and temperature under pressure, but there are still limits to how long it will preserve food. There are several factors that limit the shelf life of canned foods. First, cans can rust over time. Shipping accidents, where cans fall and dent or are crushed, also cause container problems.

Then there's can corrosion. In all foods, but especially in high-acid foods like canned tomatoes, natural chemicals in the food continually react with the container. Over several years, this can cause taste and texture changes, and eventually lower the nutritional value of the food.

High temperatures (over 100 °F) are harmful to canned goods too. The risk of spoilage jumps sharply as storage temperatures rise. In fact, canned goods designed for use in the tropics are specially manufactured.

Store canned foods and other shelf stable products in a cool, dry place. Never put them above or beside the stove, under the sink, in a damp garage or basement, or any place exposed to high or low temperature extremes. Temperatures below 85 °F are best. Check your pantry every few weeks and use canned goods you have had on hand for awhile. Don't purchase bulging, rusted, leaking, or deeply dented cans.

No matter why we choose to preserve at home, we want the results of our efforts to be of good quality and safe to eat. The USDA and extension programs have published guidelines for safe home food preservation methods and recipes based on research and extensive testing. Watch UC Master Food Preserver Food Safety Training (a series of 11 videos that the University of California has made available to the home consumer) to understand the science behind food quality and safety. Video topics include food spoilage, microorganisms found in food the can be hazardous and environmental factors that affect the rate at which they multiply. Research is ongoing, so recommendations may change. Look for the most current recommendations at the National Center for Home Food Preservation (NCHFP).

Start with food of good quality and adhere to food safety guidelines: clean - separate - cook - cool. Remember: If food doesn't look or smell right, it is better to throw it out than to risk your health.

Historical Origins of Food Preservation describes Drying, Freezing, Fermenting, Pickling, Curing, Jam and Jelly, and Canning. Our web pages cover drying, freezing, and canning of pickled foods and jams and jellies. Our produce-specific pages have sections on storage when you bring food home and these food preservation techniques, when applicable.

Know where to Store Fresh Fruits and Vegetables for Better Taste. 

Cold Storage (Refrigeration and Freezing)

Reducing the temperature at which food is stored slows the growth of food spoilage microorganisms and enzymatic reactions within food.
Many, but not all foods benefit from cold storage.

Drying (Dehydration)

Drying (dehydrating) food is one of the oldest and easiest methods of food preservation. Dehydration is the process of removing water or moisture from a food product. Removing moisture from foods makes them smaller and lighter. Dehydrated foods are ideal for backpacking, hiking, and camping because they weigh much less than their non-dried counterparts and do not require refrigeration. Drying food is also a way of preserving seasonal foods for later use.

Pickling, Fermentation

Canning