What Is a Tunnel Freezer?
Tunnel freezers are machines designed for rapid freezing operations in an ambient room temperature environment. Their shape allows food to pass through while cold air is blown directly over it, quickly freezing the food through a temperature range where bacteria multiply rapidly (50 to 140 °F). The interior is steam-sterilizable, making it suitable for clean room installation. Unlike batch freezers, tunnel freezers ensure consistent exposure to cold air, though spiral freezers, with their compact design, may offer less cooling efficiency.
Uses of Tunnel Freezers
Tunnel freezers are integral to the food industry, processing seafood, meat, confectionery, bakery items, and frozen foods. They facilitate individual quick freezing (IQF) for products like rice, vegetables, ground meat, shrimp, and fish, allowing for bulk processing without clumping. Some models provide enhanced quick freezing capabilities, ideal for larger items like crabs or pizzas, and can perform rapid surface freezing to maintain moisture and facilitate easy slicing.
Principle of Tunnel Freezers
Cold air is circulated over the products by a unit cooler, maintaining constant temperatures at entry and exit points to ensure efficient freezing. Refrigerants such as ammonia gas, liquid nitrogen, or carbon dioxide are used, with some models offering IQF functionality for piece-by-piece freezing. Regular defrosting is necessary to maintain cooling efficiency, with some models featuring automatic defrosting systems to prevent frost buildup.
Types of Tunnel Freezers
Models vary, with some equipped with clean-in-place (CIP) systems for automatic cleaning and defrosting. They are larger than batch and spiral tunnel freezers and should be chosen based on production needs.
How to Choose a Tunnel Freezer
Selecting a tunnel freezer requires consideration of production capacity, risk of food loss due to malfunction, and maintenance needs. They demand more intensive cleaning, especially when changing products, to ensure hygiene and prevent cross-contamination. Regular maintenance and possible backup refrigeration systems can mitigate production losses.
Structure of a Tunnel Freezer
While tunnel freezers minimize uneven freezing compared to batch freezers, nozzle direction and product placement need careful adjustment to ensure uniform freezing. Regular defrosting is essential to prevent frost buildup from impairing airflow and cooling performance.