Preserving food lets you keep a summer harvest, buy in bulk or simply waste less. Every method works by slowing down or stopping the microorganisms and enzymes that spoil food: by removing heat, water or air, or by adding acid, salt or sugar.
Freezing
The easiest method for most foods. Freezing at 0°F (-18°C) stops bacterial growth (it does not kill bacteria, which become active again on thawing).
- Blanch most vegetables briefly in boiling water, then cool them in ice water before freezing; this stops enzymes that cause loss of color and flavor.
- Freeze berries spread out on a tray, then bag them.
- Remove as much air as possible to prevent freezer burn, and label everything.
Canning
Canning heats food in sealed jars to destroy microorganisms and create a vacuum seal. It is also the method where mistakes are most dangerous.
- Water bath canning is only safe for high-acid foods: most fruits, jams, pickles and properly acidified tomatoes.
- Pressure canning is required for low-acid foods: vegetables, meat, beans, soups. Only the higher temperature of a pressure canner reliably destroys the spores of Clostridium botulinum, which cause botulism.
- Use tested recipes and processing times. The National Center for Home Food Preservation publishes them for free.
- Discard any jar with a bulging lid, leaks, spurting liquid or an off smell, without tasting it.
Pickling
Vegetables preserved in vinegar (quick pickles in the fridge, or canned pickles) or by fermentation in salt brine. Quick refrigerator pickles are a great beginner project and keep for weeks in the fridge.
Fermenting
Lacto-fermentation uses salt to encourage beneficial bacteria that produce acid: sauerkraut, kimchi, fermented hot sauce. Keep vegetables submerged under the brine, and store finished ferments in the fridge.
Drying and dehydrating
Removing water stops microbial growth. A food dehydrator or a low oven works for fruit, vegetables, herbs and jerky. For jerky, the USDA recommends heating meat to a safe internal temperature (160°F for beef, 165°F for poultry) before or after drying.
Sugar and salt preserves
Jams, jellies and fruit butters rely on sugar plus heat; salt curing is used for meats and fish. Both need tested recipes.
Root cellaring and cool storage
Potatoes, onions, winter squash, apples and carrots keep for weeks or months in a cool, dark, well-ventilated place.
What not to do
Do not store garlic or herbs in oil at room temperature: it is a known botulism risk. Keep such mixtures in the fridge for a few days or freeze them. Learn more about herbs in how to store and use up fresh herbs. Preserving is one part of wasting less food, see the best ways to reduce food waste.
