Freezing on a massive scale
Solutions for every kind of crustaceans
Raw, shelled, and gutted shrimps may not lie on top of each other in a freezer unit, since the protein on the product surface would immediately bond them together. For this reason, tunnel freezers with IQF technology are used here (IQF means individually
quick frozen). Here, the shrimp are distributed uniformly and with sufficient intervals (usually automatically) onto a long conveyor belt, which takes them through the tunnel freezer. In the freezer, cold air blows from the top down through the conveyor belt. The product is kept in continuous motion until the surface is frozen and the fish can no longer stick together. The consumer can later divide up the shrimp into servings and can even take them out individually.
If boiled shrimp are frozen, it is almost always a case of “northern shrimp”. They are popular for being especially delicate and aromatic, but they are especially small: 200 to 500 ea. per pound, and broken. This classification “broken” refers to pieces
of the shrimp, since – even when great care is taken – it is not always possible to prevent breakage of the tail off the graceful shrimp. This of course has no effect on the taste, although the resulting “crabmeat” is sold for a lower price. For application here,
GEA offers tunnel freezers with tightly meshed conveyor belts. These systems are pre-assembled in the factory and are usually designed for capacities of one to two metric tons per hour. Larger shrimp (20 to 100 ea. per pound),
without heads but with tails, can be frozen in tunnel freezers: either raw or cooked, with or without shell. The tunnel freezer will be dimensioned according to the product size.
If the shrimp have both shells and heads, then we have to use our own heads to ensure proper freezing. It is essential to preserve the very long antennas on the finished products. Spiral freezers are most effective here. If the processor intends to freeze the individual animals, horizontal plate freezers and impingement freezers are also effective. Impingement freezers blow cold air under great pressure onto the shrimp, simultaneously from both above and from below. This ensures fast freezing and is especially
effective for flat products – which makes these systems ideal for the larger shrimp.
Crustacean products that have already been further processed – i.e., cooked in bread crumbs or battered – require especially careful treatment. Spiral freezers are usually the best solution, to ensure that the delicious surface remains intact. In many cases, this kind of freezer is still being loaded manually.
If the shrimp are not already provided with a tasty coating, they must often have a system exit temperature of less than - 18 °C / - 0.4 °F, so that they retain their last processing step: the ice glazing. A fine spray water mist produces this extremely thin, shiny layer of ice. This procedure automatically involves a slight warming of the shrimp, especially the smaller ones. As a result, one more “after freezer”, or “hardener” step is required after the glazing finish. This is an extra freezing step that pays off. Its purpose is by no means limited to optical enhancement, since the ice layer protects the shrimp from drying out in their frozen condition. The customer profits from the longer life of the product, and from better quality. Fast after freezing forms only small ice crystals. If the shrimp were frozen more slowly, larger ice crystals would develop and destroy the cell walls. Then, when the shrimp thawed out, water would flow out of the broken cell walls – leading in turn to drying out and loss of aroma.