Autoclaves in the Food Industry

Importance of autoclaves in the food industry

In the complex world of the food industry, the safety and quality of products are paramount. To achieve these goals, various preservation techniques are employed to eliminate or inactivate microorganisms that can cause diseases, with sterilization and pasteurization being particularly effective.

The thermal process of pasteurization is somewhat similar to sterilization but operates at lower temperatures, between 80ºC and 100ºC, typically at atmospheric pressure, and requires specific durations depending on various factors. These characteristics allow pasteurization to achieve a lower bacterial mortality rate than sterilization, yet sufficient to guarantee a packaged product’s market presence for several months.

In both cases, the primary goal is to ensure food safety and product quality, delay deterioration, prevent infections and public health risks, comply with existing regulations, and extend shelf life, which is longer when the product is sterilized.

At Gaictech, we manufacture autoclaves and pasteurizers for the food industry. We are fully aware of the importance of having these devices appropriately designed to meet the highest regulatory standards on the market.

Let’s look at the key points.

What are autoclaves?

Autoclaves are sterilization devices that use steam or superheated water, employed in the food and pharmaceutical industries to ensure the safety and quality of products.

Their operating principle is based on applying thermal treatment to the product using a conducting fluid, such as steam or superheated water, at temperatures above 100ºC along with the corresponding pressure, as dictated by physical laws. This process eliminates pathogenic microorganisms, such as bacteria, fungi, and viruses, from packaged foods, ensuring the safety of sterilized products for a certain period of time.

How do autoclaves work?

The operation of autoclaves relies on applying thermal treatment to the product by injecting either saturated steam or superheated water. The transported heat penetrates the food, eliminating microorganisms present in both the food and its packaging. Temperature and exposure time are carefully controlled to ensure complete sterilization with minimal impact on the product’s organoleptic properties.

Examining the process as a whole, it starts with loading carts or baskets with packaged products (glass jars, cans, flexible bags, and others), which are designed to withstand the temperatures and pressures of the process. These are then introduced into the autoclave, which is hermetically sealed to create a controlled environment.

Subsequently, the thermal process begins (with conditions varying depending on whether saturated steam or superheated water is used), until the specific conditions required for the different products are reached. These conditions are maintained for a specified time to ensure complete sterilization. In all cases, we are referring to:

• The initial phase of increasing and stabilizing the sterilization temperature (TRT – Target Retort Temperature) throughout the autoclave (CUT – Come Up Time).
• The second phase involves the actual sterilization time, which determines the bacteria lethality factor.

The duration depends on the type of product and the geometry of the containers, although this time can be reduced by increasing the temperature if the product allows.

The process then continues with controlled cooling to reduce the temperature and pressure within the autoclave, concluding with the opening of the equipment and unloading of the sterilized products for storage.

Working Systems in Autoclaves

There are various operating systems for autoclaves, each with its own advantages and specific applications. These systems primarily differ based on the fluid that supplies heat to the thermal process and how it is managed within the autoclave, affecting energy efficiency, the quality of the sterilization process, and the quality of the final product. The main operating systems used in autoclaves are described below:

1. Steam and Water Spray – SWS:

   This technology combines direct steam injection with the spraying of superheated water. Steam is introduced from the bottom of the autoclave, while superheated water is sprayed from the top and sides, kept in circulation by a centrifugal pump. This method ensures uniform heat distribution in an optimal time.

   Advantages	Disadvantages
   Suitable for any type of food container.	Does not recover steam condensates, which may imply higher energy consumption compared to other systems that do recover them.
   Provides uniform heat distribution with a smoother temperature gradient.	When working with superheated water and needing to provide counterpressure using compressed air to prevent container deformation, can result in small rust peaks in the sealing area of tinplate containers if the prior sealer is not well adjusted. This can be resolved by adding antioxidants to the recirculation water.
   Allows efficient cooling by installing a water-to-water plate heat exchanger. Additionally, cooling water can be reused through a cooling tower, dry-cooler, or recirculated from a large-capacity water buffer tank.
   The organoleptic qualities of the product are hardly affected as the temperature gradient can be more gently controlled during the heating and cooling phases, making it suitable for more delicate products.

2. Saturated Steam – SST:

   This is the traditional method of sterilization in autoclaves. It uses saturated steam to rapidly reach the sterilization temperature. It is particularly recommended for dense loads composed of small containers or where the external varnish quality of the packaging is not good.

   Advantages	Disadvantages
   Effective for small and rigid cans. Allows for rapid cooling through spray or water immersion.	Higher energy consumption compared to the SWS system.
   Total processing times are slightly shorter than the SWS system.	Limited to containers that can withstand the internal pressure of the container itself and subsequent deformation during the thermal process (mainly tinplate containers of good thicknesses). It is not recommended for current containers with thinner walls.
   Enables efficient cooling by installing a water-to-water plate heat exchanger. Additionally, cooling water can be reused via a cooling tower, dry cooler, or recirculated from a large capacity buffer tank.	The temperature gradient is less gentle than in the SWS system, which can affect the organoleptic qualities of some products.

3. Dual:

   This system combines two technologies: SWS and SST, providing users with the flexibility to choose between either method depending on the type of container and the product’s requirements.

   Advantages	Disadvantages
   Flexibility to process a wide variety of containers, ranging from small or large cans to aluminum, glass, or flexible containers, which may require different sterilization methods, saving space and optimizing energy resources.	The machine’s cost is slightly higher due to the integration of both systems.

4. Water Spray Heating:

   This method uses an external heat exchanger to indirectly heat the spray water instead of injecting steam directly into the autoclave.

   Advantages	Disadvantages
   Requires minimal maintenance.	CUT times are slightly longer compared to SWS and SST systems due to the indirect water heating.
   Recovers steam condensates, enhancing energy savings.
   Can be integrated into an SWS system.
   Allows efficient cooling using the same heat exchanger (water-to-water heat exchange in this phase), under the same conditions as indicated for previous systems.
   Generally, it is the system that implies the highest energy savings.

5. Water Cascade Heating: This system shares the same characteristics as the Water Spray system but circulates water through a ‘cascade.’ It is particularly suited for small-area containers and serves as a good alternative to the SWS or Water Spray systems if the product allows. Additionally, the initial investment is slightly lower.

The choice of autoclave operating system depends on the specific sterilization process requirements and the type of container to be treated, as well as the particular conditions of each client. Dual systems combining multiple technologies offer flexibility and efficiency, allowing users to optimize their sterilization processes without compromising product quality or safety.

The selection of working methods for the autoclave will ultimately depend on a detailed study of costs and productivity.

If you have any doubts about which autoclave is best suited for your plant and production process, at Gaictech, we can advise and offer the most suitable solution to meet your needs. Contact us for more information about our equipment.

How does the autoclave control system work?

In dual autoclaves, the PLC also allows the selection of the type of working system to be used for sterilization, whether it be saturated steam or water spray.

Additionally, all information related to the sterilization process can be recorded and exported. This data can be logged either analogically using circular paper charts or digitally, with the option to export to centralized management systems. This flexibility in data management facilitates audits and regulatory compliance control.

How are autoclaves integrated into the production line?

When integrating an autoclave into the production line, several factors and variables need to be considered: operational, economic, and sustainable, which provide a wide range of options. Integration solutions for the autoclave include:

• Loading and unloading systems for carts: manual, semi-automatic, or automatic
• Automatic loading and unloading circuits, for handling carts around the autoclaves
• Door opening systems vertical (hydraulic) or horizontal (pneumatic)
• Complete integration with existing production systems
• Automation studies for new or operational factories

These solutions ensure that the autoclave integrates seamlessly into the client’s workflow, enhancing efficiency and reducing downtime.

Specifically, at Gaictech, we can bring significant added value thanks to the flexibility and adaptability we offer to meet our clients’ needs. We can customize our range of autoclaves and develop bespoke solutions to integrate them into the client’s production environment. Moreover, our extensive experience in designing complete production lines allows us to better understand how to integrate the autoclave into the production system, maximizing space utilization and optimizing product flow.

Our specialized technicians oversee the entire installation and configuration process, ensuring that the equipment operates correctly and meets all client requirements. Additionally, we provide continuous support and training for the handling and maintenance of the autoclaves, ensuring optimal and long-lasting performance.

Types of autoclaves in the Food Industry

In the food industry, two primary types of autoclaves are used for processing and sterilizing food, static autoclaves and dynamic autoclaves, such as rotary or pendular autoclaves.

On the other hand, there are pasteurizers, which perform a thermal process at lower temperatures, offering a shorter shelf life for the product (several months) but are suitable for various products. Pasteurizers can be batch-type (similar in design to autoclaves but operating at lower temperatures) or continuous horizontal types (custom-designed based on production needs and the format of the product to be pasteurized).

The selection of autoclave type will depend on factors such as:

• The type(s) of product(s) being processed.
• The container(s) used.
• Specific sterilization requirements.
• Production capacity.

Static autoclave

It is the most common and traditional type in the food industry, capable of pasteurizing and sterilizing, offering an excellent cost-benefit ratio. In this equipment, the packaged products placed on carts remain stationary throughout the process, without any movement applied to them. It is suitable for products that do not require movement during the sterilization process and where most of the packaged product is solid or highly viscous.

The static autoclave is ideal for

• Canned foods (vegetables, fruits, meats, fish, and seafood)
• Flexible packaging (filled with vegetables, fish, and meats, and/or ready-to-eat products or recipes)
• Preserved meat products
• Seafood products (tuna, sardines, squid, etc)
• Pet food (canned or flexibly packaged foods for dogs and cats)
• Other products where the majority percentage is a solid or highly viscous product

At Gaictech, we manufacture static autoclaves with diameters of 700, 1000, 1300, 1500, 1800, and 2000 mm, capable of holding up to 12 baskets. These autoclaves are made from AISI-304L/316L stainless steel with thicknesses of 6 and 8 mm. They operate at a maximum working temperature of 150ºC and a maximum working pressure of 5 bar, parameters that can be adjusted based on process requirements or customer requests. Our autoclaves comply with the strictest manufacturing standards and are certified under CE regulations.

Rotary autoclave

The rotary autoclaves incorporate an internal slow rotation system for the carts up to 360º, which is designed to move the packaged products during the sterilization process. Throughout this process, the carts are immobilized, as are the containers placed within them, ensuring their integrity and preventing damage. This method allows for a more uniform heat distribution and accelerates the sterilization process, especially for products with high liquid or semi-liquid content.

The rotary autoclave is an excellent option for food processing, such as:

• Juices and beverages (including fruit juices, nectars, fruit-based drinks, and other packaged liquids)
• Sauces and condiments (such as tomato sauces for pasta, dressings, and other packaged liquid or semi-liquid products)
• Jams and preserves (jellies and compotes packaged in jars or similar containers)
• Dairy products (such as yogurts, dairy desserts, and more)
• Purees, creams, and a variety of broths
• Ready meals (pre-cooked dishes, ready-to-eat meals, soups packaged in cans and/or flexible containers, among other products)
• Certain pet foods

Gaictech rotary autoclaves are designed to process products packaged in cans, glass containers, or flexible packages, with the capability to rotate carts from 0 to 360º. This makes them versatile equipment suitable for sterilizing products that require full or partial rotational movement. Additionally, they can be supplied with various sterilization systems (from System 1 to System 4), ensuring energy-efficient operation and an excellent cost-benefit ratio.

At Gaictech, we manufacture rotary autoclaves with diameters of 1500 and 1700 mm, accommodating up to 6 baskets. These autoclaves are made from AISI-304L/316L stainless steel sheets with thicknesses ranging from 6 to 8 mm, with a maximum working temperature of 160ºC and a maximum pressure of 5 bar. These specifications can be modified according to process requirements or customer requests. Our autoclaves are built to the highest manufacturing standards and hold CE certification.

A distinguishing feature of our autoclaves is the option to include a second door, thanks to the innovative rotation system of the baskets, which is not installed at the rear of the autoclave. This design allows the use of the rear for a second door, enhancing the continuity of the production process. More detailed information is available in the Rotary Autoclave datasheet.

Pendular autoclave

The pendular autoclave has characteristics similar to the rotary autoclave, but the carts are subjected only to a pendular movement with limited degrees of swing. It is used in the processing of a variety of packaged food products (especially those of vegetable origin or with mixed ingredients where a significant percentage is liquid or of low viscosity), where this slight movement accelerates temperature distribution and reduces the overall cycle time.

Among the main products processed in this type of autoclave are the following: meals (pre-cooked dishes, ready-to-eat meals, and prepared dishes in general), packaged soups (in pouches or other flexible containers), products with sauces (stews, casseroles, and similar items), and products with both liquid and solid content (prepared dishes, stews with pieces of meat or vegetables, among others).

Pasteurizer

A pasteurizer is a piece of equipment used in the food industry to perform thermal treatment on a wide range of products. The aim is to eliminate pathogenic microorganisms (such as Escherichia coli, salmonella, listeria, among others), reduce enzymatic activity in foods, and extend the product’s shelf life. The pasteurization process involves heating the food to a specific temperature, between 80°C and 100°C, under atmospheric pressure, for a specified duration, and then rapidly cooling it to prevent bacterial growth.

The shelf life provided by pasteurization spans several months, which is shorter compared to sterilization, yet still suitable for numerous products.

Among the main food products processed in pasteurisers are:

• Dairy products (milk, cream, cheese, yogurt, and others)
• Beverages (fruit juices, soft drinks, and beer)
• Liquid eggs
• Processed meats (sausages and ham)
• Molluscs packaged in flexible pouches
• Baby food

Gaictech’s pasteurisers, which employ Water Spray heating systems up to 98ºC, are designed as continuous tunnels divided into two zones (pasteurisation and cooling). Within these zones, additional sections for pre-heating and pre-cooling can be incorporated. They feature both visual and acoustic alarms to ensure production safety and continuity, as well as food quality.

Their versatility allows for processing foods in various types of packaging (can, glass, plastic, flexible pouch, and flexible trays), and adapting to the needs and specifications of the client, production process, and product type, always with the support of our team of specialized technical advisors.

For more information, contact our sales team, who will provide solutions tailored to your production needs anywhere in the world, ensuring uniform temperature distribution, energy efficiency, regulatory compliance, and customer service that only we can offer.

Parts of the horizontal autoclave

A horizontal autoclave primarily consists of the following parts:

• The loading area: This section holds the carts or baskets with the products to be sterilized. Loading can be manual or automated, depending on the customer’s needs.
• Control Panel (PLC): This automated system controls and monitors all autoclave parameters related to the sterilization cycle (pressure, temperature, time, F0, as well as safety measures). Some autoclaves are designed to integrate with centralized data management systems, allowing for more efficient control and supervision from a control room.

• Autoclave door: Doors can be vertically (hydraulic) or horizontally (pneumatic) operated. The choice depends on the specific needs of the cart management system. Doors are designed to close and lock automatically before the sterilization process and to open safely at the end of the cycle.
• Autoclave body: This is the sealed chamber where the sterilization cycle occurs. The body must be sturdy and capable of withstanding high temperatures and pressures and be ready for situations involving partial vacuum.
• The heat exchanger: Connected to the primary circuit (circulating water used for sterilizing or cooling containers), this component enables indirect heating and cooling of the water used for the thermal process. For certain work systems, the circulating water, hot or cold, passes through it to be directed to the spraying or cascading system that distributes heat evenly over the containers. In SWS or SST systems, the heat exchanger is only used for the cooling phase. In the secondary circuit of the heat exchanger, steam and/or cold water is introduced to heat and/or cool the recirculating water in the primary circuit, depending on the working system.

• Recirculation pump: This pump recirculates the water from the primary circuit within the autoclave, creating a closed loop. It sends water from the bottom of the autoclave to the heat exchanger and returns it inside the autoclave through the Spray or Cascading system, depending on the working system used.
• Devices for measuring temperature, pressure, and time: These devices continuously monitor the internal conditions of the autoclave to ensure each sterilization cycle meets the established parameters. They come with Calibration Certificates issued by an Official Entity.
• Necessary valves for the process: These include steam inlet valves, condensate outlet valves, water inlet and outlet valves, air inlet valves, pressure release valves, and various valves for liquid drainage. These valves are essential for regulating the internal environment of the autoclave during the sterilization cycle and adjusting to the programmed work curve. Depending on their function, they can be isoproportional or fully open or closed.
• Safety systems: Various mechanical, pneumatic, and electronic safety systems, some redundant, are installed to ensure that the process is carried out under total safety and control. This includes both visual and acoustic alarms.