Sterilization retort is equipment used for sterilizing products such as food and pharmaceuticals.

Sterilization Retorts

Sterilization retorts, also known as sterilization kettles or sterilizers, are equipment used for product sterilization in fields such as food and pharmaceuticals. The structure consists of a kettle body, kettle lid, opening device, locking wedge blocks, safety interlock device, track, sterilization basket, steam spray pipe, and multiple nozzles. The kettle lid seal uses an inflatable silicone rubber high-temperature resistant sealing ring, ensuring reliable and durable sealing. The inner kettle is made of austenitic stainless steel, equipped with pressure gauges and safety valves, offering both safety and corrosion resistance.

This equipment uses pressurized steam as the heat source, featuring high thermal efficiency and stable temperature control. Based on the control method, it is classified into four types: manual, semi-automatic electric, semi-automatic computer-controlled, and fully automatic computer-controlled, with temperature control accuracy up to ±0.1°C. Sterilization methods include hot water circulation, steam, and spray-type (shower-type), with the spray-type further divided into rotary and static types, among others. Structural classifications include six types such as single tank, double layer, vertical, and rotary. Materials are divided into full stainless steel, semi-steel, and carbon steel. Selection must consider temperature control accuracy, heat distribution uniformity, and product characteristics. For example, soft-packaged foods are recommended for spray-type sterilization, while packages containing gas require fully automatic control systems.

Classification by Control Method:

1. Manual Control Type: All valves and water pumps are manually controlled, including steps such as water filling, heating, heat preservation, and cooling.
2. Semi-Automatic Electric Control Type: Pressure is controlled by an electric contact pressure gauge, temperature is controlled by a sensor (PT100) and an imported temperature controller (accuracy ±1°C). The cooling process requires manual operation.
3. Semi-Automatic Computer Control Type: Uses a PLC and text display to process signals collected from pressure sensors and temperature sensors. It can store sterilization processes and offers high control accuracy, with temperature control up to ±0.3°C.
4. Fully Automatic Computer Control Type: The entire process is controlled by a PLC and touch screen. It can store sterilization processes; the operator only needs to press the start button, and an alarm sounds automatically upon completion of sterilization. Temperature control accuracy can reach ±0.1°C.

Classification by Sterilization Method:

1. Hot Water Circulation Sterilization: During sterilization, the food in the kettle is completely immersed in hot water. This method provides relatively uniform heat distribution.
2. Steam Sterilization: After loading the food into the kettle, steam is introduced directly for heating instead of adding water first. As air exists in the kettle during sterilization, cold spots can occur, making the heat distribution less uniform.
3. Spray-type (Shower-type) Sterilization: This method uses nozzles or spray pipes to spray hot water onto the food. The sterilization process involves spraying mist-like, wave-patterned hot water onto the food surface through nozzles installed on both sides or the top of the sterilization kettle. Therefore, it not only provides uniform temperature without dead angles but also achieves rapid heating and cooling speeds, ensuring comprehensive, fast, and stable sterilization of products in the kettle. It is particularly suitable for sterilizing soft-packaged foods.
   • Spray-type sterilization can be further divided into: spray-rotary type; spray-static type; pulsed side-spray type, etc.

Classification by Tank Structure:

1. Single Tank Sterilization Retort
2. Double Layer Sterilization Retort
3. Double Kettle Parallel Sterilization Retort
4. Vertical Sterilization Retort
5. Electric-Steam Dual-Use Sterilization Retort
6. Rotary Sterilization Retort

Classification by Kettle Material:

1. Full Stainless Steel
2. Semi-Steel
3. Carbon Steel

How to Choose:

1. Primary selection criteria are temperature control accuracy and heat distribution uniformity. If product requirements for temperature are very strict, especially for export products which require very uniform heat distribution, a fully automatic computer-controlled sterilization retort should be chosen whenever possible. Semi-automatic computer-controlled retorts offer the same temperature and pressure control as fully automatic ones but at about one-third of the price. For general requirements, a semi-automatic electric control retort can be chosen. Manual retorts are difficult to operate for sterilization, as temperature and pressure control are done manually, making it hard to control food appearance, resulting in higher rates of can (bag) swelling and breakage.
2. If the product is packaged with gas or has strict appearance requirements, a fully automatic or semi-automatic computer-controlled sterilization retort should be selected.
3. If the product is in glass jars or tinplate, because both heating and cooling rates need to be controllable, a double-layer sterilization retort generally should not be chosen.
4. Considering energy savings, a double-layer sterilization retort can be chosen. Its characteristic is that the upper tank is a hot water tank and the lower tank is the processing tank. The hot water from the upper tank is reused, saving a significant amount of steam. It is suitable for food production enterprises with a daily output exceeding 10 tons.
5. If the production volume is small or there is no boiler, an electric-steam dual-use sterilization retort can be considered. Its principle involves generating steam by electrically heating the lower tank, while the upper tank is used for sterilization.
6. If the product has very high viscosity and needs to rotate during the sterilization process, a rotary sterilization retort should be selected.