Freezing in homogeneous mass or “blast freezing”, in 2 kilo or five-pound boxes of shrimp, is relatively low in cost.  When product is individually frozen, commonly known as IQF freezing, this value-added process is more labor intensive and requires costlier freezing equipment.  Large items such as chicken parts, or hamburger patties work well in spiral freezers with mechanical refrigeration systems.  Cryogenic freezing systems, which usually employ liquid nitrogen or CO2 gas are also very effective, but due to the high cost of the gas, are usually limited to high dollar product.

Quick freezing of food pieces individually, or IQF Freezing in mechanical freezers, of items such as cut broccoli and cauliflower, peas, diced vegetables, berries, etc. presents a variety of problems.  The quantity to be frozen in pounds per hour of different varieties is dependant the specific heat of the product, the size and shape, the temperature when entering the freezer and the free water content.  In order to attain some degree of efficiency in mechanical freezers, a combination of three major processes are necessary to effect instant crust-freezing of the product so that the articles will not stick together or stick to their conveyance.  These processes are:

·         Controlled low temperature

·         An efficient air-blast pattern through the articles

·         A means of Rotating or Tumbling the product in the initial stage of freezing

These three processes are augmented and rendered more efficient by use of proper variable speed conveyance in even distribution across the in-feed conveyer, with shakers or other means, and de-watering devices to control free water content.

The purpose of these processes is to instantly crust-free the product as it enters in the initial freezing phase in a single layer.  As this is accomplished (so that the articles do not stick) they are then conveyed to the second phase where they may be several inches thick, while still in a low temperature air-blast.  The product is then in a state known as “deep fluidization”.  This final phase freezes the product totally, where it may be packaged, stick- free like “marbles in a sack”.

Freezing systems for particular operations require consultation to be sure that there is a balance between amount of product to be frozen and the cost of the equipment.  Some flexibility should be considered so that the bulk of your product can be frozen with a minimum equipment investment and consideration given to the growth of production capability.