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Food sterilization destroys all micro-organisms, including spore-forming bacteria. It also extends food shelf life. Finally, sterilization reduces the risk of microbiological contamination.
A closer look at the characteristics and 4 stages of the food sterilization cycle.
The sterilization process: characteristics and objectives
Nicolas Appert perfected the appertization method in the 18th century. Subsequently, scientists used steam to sterilize food. This led to the invention of autoclave sterilization in the early 20th century.
Here’s a quick reminder of the principles behind this heat-based food preservation process.
The aim of food sterilization
The aim of food sterilization is toextend the shelf life of products. To achieve this, they are subjected to a temperature in excess of 100°C. Any type of food product can be sterilized: vegetables, fruit, milk-based recipes, etc. Once sterilized, preserves can be stored at room temperature. Shelf life can exceed 12 months, depending on the recipe.
Food safety and hygiene
The food sterilization process protects consumers from hazards associated with food processing. This method guarantees food safety. All pathogenic micro-organisms are destroyed by sterilization.
Water spray sterilization vs. steam process
Two different processes can be used for food autoclave sterilization: the water spray process and the steam process. Here’s a comparison of the two techniques.
The water spray sterilization process
The water spray process generally distributes heat more evenly throughout the autoclave. It is best used for fragile products, to avoid the impact of steam’s more “aggressive” heat.
The steam process for sterilization
The steam process is used for products that need to be heated quickly and intensively (e.g. : pet food). It is likely to consume less energy than water spraying, but it all depends on the installation.
Food preparation before sterilization
Before sterilization, food products must be prepared in compliance with food hygiene and safety regulations. Products must then be packaged in suitable containers (e.g. Weck cans and jars). These are then hermetically sealed to ensure effective sterilization.
Phase 1: food autoclave purging and filling process
The purging phase removes air from the autoclave (for the steam process). As air is insulating, its presence leads to poor heat distribution in the autoclave.
Phase 2: Heating up the food autoclave
This phase brings the autoclave up to temperature. Heating time depends on the energy input. Each temperature phase is associated with a counter-pressure. As products rise in temperature, the pressure inside the packaging increases. To counteract swelling and prevent deformation of the packaging, compressed-air counter-pressure is added.
A degassing phase may be necessary. This allows glass jars to be vacuum-packed with rubber (Weck or Le Parfait jars). An initial heating phase takes place to 90°C at 0 bar. These parameters are then maintained for 10 minutes. This phase allows the air to escape from the jars. A bar of back pressure is then added as quickly as possible to close the jars. They are now under vacuum.
Phase 3: temperature maintenance stage of the food autoclave
The phase of maintaining the sterilization temperature corresponds to the cooking phase. This is the most important and critical phase of the heat treatment. Compliance with the time/temperature pairing is essential. Heat is diffused into the products in two ways.
- By conduction: heat conduction takes place from the hottest to the coldest zones. Heat transfer is slower and less uniform throughout the product.
- Convection: natural movements in fluid products, combined with forced diffusion through agitation, ensure rapid, even heat transfer throughout the product.
Stage 4: cooling the food autoclave
Cooling depends on the cold water flow rate injected, and also on the products to be sterilized. It reduces the temperature of both the autoclave and the products. The start of the cooling phase is critical. Thermal shock can damage packaging or affect product texture.
The benefits of sterilization technology for canning quality
The appertization or sterilization technique offers many advantages for food preservation. The jars or preserves produced are easy to store, with no need for additional energy expenditure; there’s no need to put them in the fridge or freezer, for example. Simply protect the glass from violent shocks to ensure the safety of the food contained. The variety of products of products that can be heat-treated is another advantage.
At the end of the autoclave sterilization process, sterilized canned food must be stored under appropriate conditions. The aim is to maintain their quality. If the cycle steps are followed and the lid is watertight, you can store them for several months.
Do you have any questions about the autoclave sterilization process?
