Cryogenic freezing is one of the most important food preservation techniques, allowing the organoleptic and freshness properties to remain intact over time. In essence, by slowing down the main enzymatic processes in food, spoilage decelerates.
The benefits of freezing are obvious, particularly in the efficiency of the various steps in the agri-food chain of the cold chain, reducing waste, improving safety and helping to enhance the nutritional qualities of food, bringing not only economic benefits but also a practical solution to reduce food waste.
Over the years, research in the field of food preservation has identified innovative ways to implement the freezing process. Cryogenic freezing is a practical example of this; it is one of the most sophisticated techniques offered by SIAD, the Italian chemical group specializing in the production of food gases and the provision of related equipment and services.
In this article we delve into what exactly it means to freeze food, at what degrees freezing takes place, and, in particular, how cryogenic freezing works and with what systems and plants it can be accomplished.
Cryogenic freezing (or cryosurgelation): what it consists of and what food cryogenics is
Cryogenic freezing (or criofreezing ) is the process of lowering the temperature of the food to -18°C at the core of the product. Specifically, this process of heat removal allows the transition from the liquid to the solid state of the water contained.
The faster this step is, the better the quality of the frozen food will be, this is because the speed of the process makes it possible to reduce the formation of macrocrystals that are responsible for the rupture of cell membranes and the loss of fluids.
In fact, the main application of cryogenic freezing is precisely related to the food industry, which is why it is referred to as food cryogenics.
Cryogenic freezing exploits the characteristics of liquid nitrogen and liquid carbon dioxide (CO2), and this great cooling power of the two gases greatly reduces freezing times (unlike traditional mechanical methodology) and allows better maintenance of nutritional properties.
In addition, at low temperatures, bacterial proliferation and all related enzymatic reactions stop: the most fragile proteins remain intact, and food safety benefits significantly.
Cryogenic Freezing and Mechanical Freezing: differences
Thus, the main difference between cryogenic freezing and mechanical freezing lies precisely in the speed at which the change of the state of water occurs. Using cryogenic liquids (down to -196°C) results in a faster process than mechanical refrigeration (down to -48°C), thus obtaining a frozen product with fewer macrocrystals and reduced liquid loss.
Cryogenic freezing: all the advantages
Cryogenic freezing is a very advantageous solution to preserve food properly, bringing benefits for both product quality and production process efficiency.
In particular, cryogenic freezing:
- Keeps the temperature constant and even
- Preserves the taste and quality of the product
- Increases the shelf life of the products
- Reduces weight loss of frozen product
- Improves production efficiency
- Ensures savings and cost reduction
- Ensures contained maintenance and cleanliness
- It is flexible and enables multiple applications
- It is environmentally sustainable
Freezing systems: what are the best freezing systems?
The freezing plants offered by SIAD each meet the different needs of the food supply chain by providing different advantages:
- Consistent and uniform temperatures
- Preservation of aroma and product quality
- Uniformly frozen products remain flexible for easy transportation
- Continuous line processing
- High production capacity and effective heat transfer for time saving
- Optimization in the use of paved space
- Ease of operation, maintenance and cleaning
Here are the main solutions:
Cryogenic cabinets
This system is particularly advantageous in batch or discontinuous operations. Food is fed into the processing cabinet in stainless steel carts consisting of plates, grids, trays or containers, depending on the type of food to be frozen. An automatic system adjusts the nitrogen input, depending on the temperature and duration of the cycle.
SIAD freezing cabinets have a temperature probe, with which the rate of cold reduction can be monitored, and thus keep the temperature inside the cabinet constant. With internal fans and efficient cooling systems, refrigerated cabinets cool food quickly.
The advantages of this system are:
- Optimized production capacity
- Rapid cooling
- Protects the nutritional properties of the food
- Small footprint
- Facilitated cleaning and maintenance
- Low operating costs
Cryogenic spiral freezers (or freezing spirals)
A freezing spiral is able to rapidly chill, freeze and harden a wide range of foods evenly thanks to a special fan that reduces temperature variations and ensures undifferentiated freezing. In addition, the system’s control options allow for varying quantities of products to be frozen.
The conveyor belt is developed vertically, optimizing the space required, resulting in excellent results with minimal space requirements.
Cryogenic spiral freezers (or food cooling spirals) are the ideal equipment for the large production of:
- Meat pieces and poultry parts (meat freezing plant)
- Baked goods
- Meatballs
- Fish fillets
- Meat dishes
- Pasta
- Pizza
The advantages provided by this facility are several: first and foremost, the versatility, with the ability to adjust temperatures according to the needs of the food to be processed, but also theefficiency, since theliquid nitrogen comes into direct contact with the product and generates optimal and uniform heat transfer, and finally the ability to automation of the process, in fact the system automatically balances the steam at the inlet and outlet of the belt, optimizing its performance.
Freezing tunnels (or cryogenic freezing tunnels)
Freezing tunnels involve a modular design. In the case of freezing small quantities, production capacity can be gradually increased, while for large quantities a wide range of products can be quickly processed or cooled.
Each tunnel freezer is equipped with internal fans that recirculate liquid nitrogen or CO2 as cooling agents at the end and the base of the product.
As the product moves through the system on a continuous conveyor belt, the cryogenic liquid impacts it at high speed, achieving high heat transfer. Cryogenic temperatures can be as low as -195.56°C, with the internal temperature of the freezer reaching as high as -90°C.
Similarly, in the case of in-line processing, modular cooling, automatic operation, and ease of cleaning and maintenance are favorable.
Cryogenic liquid nitrogen or liquid carbon dioxide tunnels are particularly suitable for the freezing of:
- Meatballs
- Ready meals
- Focaccine
- French fries
- Pizzas
- Ravioli
Drum Freezers
Drum freezing systems effectively freeze food products at a uniform temperature and, by rotating, keep individual pieces separate.
They are most widely used in the vegetable and fish industries for the purpose of rapid, accurate and uniform processing that maintains product integrity, aroma and texture. Moreover, after this freezing process, the food is already ready for shipment or transfer to other processing.
The main features of the drum freezer are:
- Product cooling and pre-freezing
- Rapid installation
- Welded stainless steel structure
- Display on all product surfaces
- Freezing of small products
Freezing processes: frosting, crusting and other modes
There are other freezing processes apart from the systems described above:
- Cryomechanics: combines cryogenic and mechanical processes. The former enable effective freezing and surface hardening, while the latter complete the temperature chilling. Cryogenic freezing pre-cools the food, removing its heat and sealing it from moisture.
- IQF (Individual Quick Freezing): enables freezing of individual pieces; therefore, it is suitable for freezing small-sized products, such as berries, mozzarella, etc.
- Immersion: uses equipment with a conveyor belt that passes through a “bath” of liquid nitrogen. By adjusting the soaking time, the percentage of frozen products can be varied.
In addition, SIAD systems are suitable for partial freezing techniques: frosting and crusting.
- Frosting is used to create a protective barrier against contamination, reducing phenomena such as dehydration and browning. It is suitable for creamy products to stabilize the shape.
- Cryogenic crusting (crusting) enables surface freezing of the product. It is used particularly in fresh products such as meat, for the packaging and portioning , resulting in a significant reduction of waste
With the experience and expertise of skilled technicians, SIAD provides state-of-the-art cryogenic gases and liquids, applications and technological solutions to protect product quality and productivity.
It also ensures maximum flexibility in identifying the most suitable freezing system and the support of trained technicians to advise on production processes, as well as constant technical assistance and scheduled maintenance.
Learn more about our offer or to find out more write to: foodandbeverage@siad.eu.
