In the last article, I emphasized accurate processing in order to achieve higher recoveries and yields. I will continue to mention this, because with the price of tuna continuing to stay at the high end, processors must obtain and utilize the maximum amount possible in order to be profitable.

The fish have reached the target backbone temperature for cooking and are now ready for cooling. It is important to note that even though the steam has been turned off and the   racks have been taken out of the cooker, the fish will continue to cook due to the heat that is retained within the body. This can result in higher backbone temperatures and over cooking. Therefore, it is important firstly, to remove the fish racks as quickly as possible once the cooker doors are opened, and secondly, to stop the cooking as quickly as possible. The most commonly used medium for cooling fish and stopping the cooking is water. The quicker you can get your racks to the cooling area, the less overcooking you will experience.

There are several methods for cooling fish but the most common is the water spray, which can be sprayed either from overhead, or from the sides, and even with the combination of both. Usually stainless steel or brass nozzles are used, and depending on the type of water spray, volume of water, and pressure, it will determine how quickly the fish will cool. It is important that the water spray coverage area is adequate to cover all the fish completely. Some cookers are also designed to have water sprays within them so that the cooking is stopped very quickly even before the fish racks are taken out. Another type of cooker will apply water to the walls of the cooker so that the heat is diminished right away, and the cooking will slow down and stop. Other processors will even allow for the cooking after the  fish racks are removed and will have this allowance incorporated in the cooking procedure which means undercooking the fish and then letting them set so that when it does cool down, it would result in fish that are fully cooked. The larger the fish, the longer it will take to cool to a workable temperature suitable for the next stage which is fish cleaning. Although some processors will air cool, by just letting the fish set out over night, it is not recommended as the fish will dry out and lose a lot of moisture which is important for recovery. It will also start to decompose be exposed to bacterial/microbial environment. It is recommended not to use air fans as the same as above will occur.

It is very important that the spray cooling is accurately controlled so that the fish are  quickly cooled and there is no excess water that would allow for the fish to get soggy and soft, resulting in lower fish recovery, lower cleaning efficiency, and excess flake. Normally the spray cooling is controlled manually or by PLC. The PLC is much better because it is fully automatic and you can have the sprays go on and off so that the heat can be released during the off cycle and the fish cooled during the on cycle. The time on and time off is very important to cooling off your fish quickly and to prevent over spraying. On/off spray cycles  should be established for each fish size and specie. The times can then be programmed into the PLC and you will be able to achieve accurate cooling for maximum recovery and cleaning efficiency. Please remember that the water that you use for the spray cooling is potable. For maintenance reasons, it is good to have a micron filter for your spray cooling system to prevent the spray nozzles from clogging and getting plugged. Without the filter you will experience nozzles that are partially spraying and some that are completely stopped.

Please mail your questions to: askdon@atuna.com

Read other Ask Don ! articles