Principles of Hydro-cooling

Hydro-cooling works by pumping chilled water into contact with warm produce. The produce can be immersed in the water or a shower or cascade of water can fall over it. It can be in containers or individual pieces. Occasionally the produce can be shipped in the containers in which it was cooled.

The water that is warmed in the removal of heat is then filtered, re-cooled and re-cycled. For cooling the water, hydro-coolers need a refrigeration system. The heat exchange component is an integral part of the hydro-cooling equipment. But the refrigerant compressor and condenser elements may be dedicated to the equipment or incorporated in a larger, multi-purpose refrigeration system.

Many types of produce respond especially well to hydro-cooling. Produce items that have a large volume in relationship to their surface area and non-porous surfaces such as sweet corn, apples, musk melon (cantaloupe), and peaches are suitable for hydro-cooling, benefiting from its excellence in preventing moisture loss during cooling. A product with the size and density of musk melon may require over an hour to cool, depending on the container it is in. Smaller items such as cherries are also well-suited to hydro-cooling, although care must be taken to prevent damage from the force of the falling water. Large quantities of cherries can be cooled in minutes.

Containers and Stacking Considerations for Hydro-cooling

An important factor in operating efficiency is container design and the stacking pattern. These elements greatly affect the heat transfer process in hydro-cooling.

A variety of produce packages have been successfully used in hydro-cooling. Plastic totes and bulk bins are popular in pre-packaging use. For products packaged and palletized before cooling wire-bound wooden crates, waxed fibreboard cartons, and mesh poly bags are alternatives.

Palletized packages must be carefully stacked to allow water to enter the packages. If the water flows around and not through the packages, little cooling will occur, or much too slowly. Produce in waxed fibreboard cartons with solid tops are particularly difficult to cool unless the tops and bottoms are designed to allow easy access and egress of the falling water.

In any selection, allowance for some open space between bulk or packaged product must be made so that the water can touch all pieces of the crop.

When clear water is available, shower type hydro-coolers can be a very economical cooling method for a broad line of products. They are commonly used for corn, celery, avocados, melons, and many products with relatively smooth surfaces. Units can be configured to match harvest needs. They are effective with asparagus, stone fruit and cherries in either boxes or bins. Water cleanup in remote areas can be handled by integrating filtering and sanitation units, with stainless steel on all water contact surfaces adding an additional layer of safety and shelf-life extension. These systems are very useful in line with processing operations. While they are usually integrated with refrigeration components, block ice can also be used to chill the water.

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