Canning is the process of subjecting foods to thermal sterilization and hermetically sealing them into containers, jars or cans. The foods are heated at the required temperature ranges to preserve them. Various foods including meat-poultry, fish etc, and vegetables can be preserved using this method.
How Canning Works
The high temperatures applied destroy micro-organisms and denature enzymes. This allows the safety and enhanced quality of a food. It is crucial to can at the recommended temperatures for each food to avoid microbes such as clostridium botulinum that cause food poisoning- botulism, that can be fatal.
Depending on type of food, acidity content, etc a food’s canning process may necessitate the enforcement of certain measures prior to canning. For example, certain acidic fruits require to be boiled before they’re canned. Others with low acidity require boiling and the addition of some acid i.e. from lemon or vinegar, before they are canned. Generally, canned foods have an extended shelf-life and can last for up to 18 months.
Factors that determine the canning process
- Type of food being preserved
- Size of cans
- Acid content of a food – acidity destroys micro-organisms at a faster rate when heated.
Types of canning
- Pressure canning-Pressurized steam releases heat that destroys micro-organisms in food.
- Water bath canning-the cans with food are placed in a water bath where they are heated. This destroys micro-organisms that are in the food.
Ensure that the canned foods are sealed, to create a vacuum and in turn prevent the entry of air, which can foster the development of micro-organisms. Once a food can is opened, it allows the entry of air that triggers microbial growth and as such should be discarded.
The foods selected should be fresh, neither unripe nor over-ripe. Canned foods should be properly sterilized and sealed to prevent the entry of air. Cans should be stored at temperatures below 24°C to retain the quality of foods.