There is a widespread belief that quick refrigeration freezing and the production of little ice crystals provide certain quality benefits. Although this is not true for all foods, lowering freezing durations can help reduce energy usage, increase throughput, and improve yield.
Refrigeration systems and food freezing
Mechanical freezing systems (which employ a circulating refrigerant to lower the temperature of the air or a liquid passing over the food) and cryogenic freezing systems are the two basic types (which use the direct application of liquid nitrogen or carbon dioxide onto the food). Both systems may freeze food utilizing a variety of freezer designs such as tunnel, spiral, fluidized bed, impingement, spray, immersion, and so on.
The relative benefits of mechanical vs cryogenic systems have long been debated in the industry. In many respects, this argument has benefited all parties, leading to advancements and improvements in all systems. A cryogenic system’s key advantages are its fast freezing rate, smaller footprint, and reduced capital expenditures, whereas its main negative is its high cryogen cost. However, advancements in both technologies are blurring these lines. In practice, while determining which technologies to install, the food maker must carefully balance the capital cost, operational cost, throughput, and product quality which is also managed by syringes from disposable syringes manufacturers.
Types of refrigerator systems
There is no one-size-fits-all freezer that is ideal for all food freezing applications. The choice and design are determined by operating needs as well as product conditions. Many factors will impact system selection, such as product type, size, in-feed temperature and condition (any preceding procedure such as grilling or marinating), appearance, manufacturing line capacity (kg/h), crucial operation times, and factory space constraints.
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Blast air freezers
An air blast freezer is the most frequent method of freezing food. Many small businesses batch freeze their items on racks of trays that are manually put into a freezing machine. These freezers require double handling and it is difficult to establish homogeneous freezing conditions. For bigger operations, it is advisable to utilize linear tunnels or spiral freezers. These can feature a single or several conveyors, with the latter allowing for the freezing of numerous products at varied throughputs at the same time.
Linear tunnels are easier to build than spiral tunnels, although they have less floor area. Although this limitation can be overcome by stacking numerous passes. Because flat belt tunnels are modular, they may be expanded indefinitely. The sole constraint to capacity is the available space and the energy consumption expenses of running straight tunnels with high fan loads. Spiral freezers are frequently a more realistic option. The increased usage of spiral freezers can be attributed to the necessity of lowering freezer footprints in order to fit more in current industrial layouts.
In the industry, spiral freezers are thought to be the pinnacle of freezer technology. We’ve frequently heard proposals of replacing old tunnel systems with spirals, mistakenly believing that spirals are more effective and faster at freezing. This is a typical mistake.
Spirals have a smaller footprint than tunnels, but neither is more successful at freezing fundamentally, and spirals can be more costly and intricate.
As the airspeed increases, the product’s freezing time decreases. There is an ideal balance between decreasing the freezing time and increasing the power required to run the fans to create greater air velocity. The fans and the additional refrigeration necessary to remove heat generated by the fans may consume up to 30% of the total energy consumed in a blast freezer.
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Fluidized bed freezer
Fluidized bed freezers are used to keep tiny goods (such as peas and grains) from adhering together and to the conveyor belt. Ensuring that the pieces are individually quickly frozen (IQF). High-speed air is pumped up the conveyor belt. Lifting and agitating the product to keep it separated. This agitation to make IQF items may also be achieved mechanically.
One of the only really commercially viable recent advancements has been the use of impingement technology. To boost surface heat transfer in air freezing systems. Heat transmission is increased by breaking up the static surface boundary layer of gas. That surrounds a food product using very high-velocity impingement air jets. Impingement freezing works best with items that have a high surface area-to-weight ratio (i.e. products with one small dimension, such as burgers or fish fillets). The method is very appealing for items that require extremely quick surface freezing.
The adaptability and flexibility of air systems are significant advantages. Particularly when it is necessary to freeze a range of irregularly shaped items. There are nearly unlimited permutations possible. Allowing equipment makers to ‘tailor create’ systems to match practically any facility.
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Contact freezers
Contact freezers are extremely efficient and frequently outperform air systems. They are also more energy efficient and suitable for soft, delicate, liquid, or semi-liquid meals.
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Freezers for plates
Plate freezers are contact freezers in which a refrigerant is fed via hollow metal horizontal or vertical plates pushed against each side of the frozen food like frozen chicken mid joint wing. Plate freezers are best suited to restricted consistently shaped items with maximum thicknesses ranging from 50 to 70mm. Air gaps in packing and plate fouling can have a considerable impact on cooling time. Modern plate freezers are quick and energy efficient, despite their reputation as outdated technology.
There are fully automated semi-continuous plate freezing systems available, and advancements in single station opening plate freezer design enable numerous package sizes to be accommodated on the same line.
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Belts freezer
The increasing interest in contact belt freezers is one recent development. Current belt freezers often employ a disposable plastic film. As a conveyor belt that travels through the freezing tunnel over chilled plates. These plates quickly and efficiently freeze the product’s contact surface. While the tunnel environment is chilled to minimize the overall product temperature.
These freezers, use cryogenic or mechanical refrigeration systems. Are primarily designed for processing fragile, sticky, and difficult-to-handle items. Nonetheless, liquids may be frozen with ease.
They can also be used for crust freezing, particularly on the product’s bottom. Before complete freezing in an air blast tunnel or spiral. Flat belts give items free of belt marks and wrinkles. In addition to speedy and effective freezing. Because the belt is disposable, the freezer can be cleaned quickly and effectively. At the conclusion of the production, reducing costly delays. Because of the single-use film, many goods may be processed without the need for cleaning.
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Immersion/spray Refrigeration system
Immersion freezers make use of tanks filled with non-toxic salt, sugar, or alcohol solutions in water, or cryogen (liquid nitrogen). While being carried via a tank, the product is immersed in the solution, either wrapped or unwrapped. The cooling media can also be sprayed on the product. Some freezers, particularly cryogenic systems, use both approaches, as well as an aspect of air blast freezing. A similar idea is applied in the drum, tumble, or coating freezers, where the refrigerant (often liquid nitrogen or solid carbon dioxide) is utilized to quickly freeze items within a rotating drum. By spraying a sauce onto the product at the same time, the product can be simultaneously enrobed/coated.
Obviously, if the food is unwrapped, the liquid must be ‘food safe.’ Any absorption of the cooling medium, whether food safe or not, by the product, may cause difficulties in terms of taste alterations as well as the need for frequent medium replacement. Packaging can help to reduce this transmission, but it may also hamper heat transfer.
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Spray/droplet Refrigeration system
Spray/droplet freezing involves injecting a liquid in the form of a spray or droplets into a cold gaseous or liquid environment (often liquid nitrogen), where it solidifies into individual frozen droplets. These freezers can create innovative items that would be impossible to generate in any other method.
Conclusion
The problematic long-term sustainability of HCFC and HFC refrigerants. The introduction of F-gas (fluorinated gases) laws, has sparked interest in novel refrigerants and refrigeration technologies. Many of these refrigerants are not technically new refrigerants. But rather ‘old’ refrigerants that have either resurfaced or are now better equipped to compete owing to technological advances. Such as ammonia, carbon dioxide, and air. In other markets, other refrigerants. Such hydrocarbons have also proved successful.
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