canning

Canning is a method of preserving food by placing it in sealed jars or containers and applying heat to destroy spoilage microorganisms and inactivate enzymes. The sealed container creates a vacuum as it cools, inhibiting microbial growth and allowing storage at room temperature for extended periods.

There are two main methods: water bath canning and pressure canning. Water bath canning uses boiling water to achieve temperatures sufficient to kill spoilage organisms in high-acid foods such as fruit, jams, pickles, and acidic sauces. Pressure canning uses a pressurized vessel to reach higher temperatures needed for low-acid foods such as vegetables, meats, poultry, and seafood, where botulism risk is a concern.

Key equipment includes glass canning jars with metal lids and rings, a jar lifter, a rack, and either a boiling-water bath canner or a pressure canner. Before processing, jars and ingredients are prepared, rims wiped clean, lids applied and tightened. Jars are then processed for a specified time at a specified pressure, with altitude adjustments as needed. After processing, jars are cooled undisturbed to allow sealing; vacuum seals indicate successful processing.

Safety and quality: Canning should be done using tested recipes and approved processing times to prevent botulism. Do not reuse lids once sealed; store canned foods in a cool, dark place. Properly processed foods can last about a year or longer, though quality generally declines over time.

History: Canning originated in the early 19th century, with practical methods developed by Nicolas Appert and later refined in commercial and home settings. This led to standardized practices and guidelines widely used by home canners and food safety organizations.