Seafood is one of the most highly perishable of all food types and will begin to spoil as soon as the fish dies. Lowering the meat’s temperature to the temperature of freezing, 32°F, will help prevent the growth of spoilage and pathogenic micro-organisms, thereby crucially extending the seafood’s viable shelf life to the point that it can be transported and sold. However, for this process to be effective it is important to understand the rate of cooling and the factors that may affect it. Failure to do so could result in inadequate cooling and dangerous, spoiled seafood. What follows is a discussion of several of the main factors that affect seafood cooling rate.
The Size of the Fish
The size of the fish is one of the most important factors that affect cooling rates since as a general rule the larger the fish the more ice will be needed to cool it and the longer it will take to completely cool. It is also important to realize that even if the outer surface of the fish reaches freezing, the inner layers of meat may still be retaining heat. Thus, larger fish will of course call for more ice and more aggressive cooling methods.
The Starting Temperature of the Fish
Another very important factor is the temperature of the fish. Most fish are cold-blooded, meaning that their body temperatures are closely in line with ambient temperatures. This is in contrast to warm-blooded organisms who regulate their body temperatures and keep it fairly consistent regardless of ambient temperatures. Thus a fish that is caught in a polar or temperate region with a cold or cool climate will have a body temperature that is much lower than that of a fish caught in a warm or hot tropical or subtropical climate.
The higher the fish’s starting temperature the longer it will take to fully cool to a safe storage temperature near freezing. Likewise, in order for the fish to reach this safe temperature it will require much more ice than a fish that is caught in already-cold waters. Thus fishing vessels operating in warmer temperatures need to start out with more ice than cold-water vessels and plan accordingly.
The Type of Ice Being Used
Some people inexperienced in the fishing or cooling industries may not realize that when it comes to cooling fish not all ice is created equally. That is because in order for the ice to be maximally effective it needs to fully suffuse and saturate the fish, so that as much of the fish as possible is in contact with the ice. Thus a fish placed against of block of ice will not be as quickly and evenly cooled as a fish that is surrounded by flake ice. Fish placed in a slush ice bath is even more efficiently cooled since the cooling agent may then enter crevices and cavities inaccessible by larger chunks of ice.
Thus an informed selection of white ice type will be used on a fishing trip will carefully consider the cooling efficiency of each type of ice and weigh that against other factors. For example despite the fact that block ice is relatively inefficient for cooling fish in block form, some fisherman decide to bring it anyway due to the convenience of storing and transporting it and an ease of acquiring it. Once out to sea the block ice may then be crushed to allow for better fish cooling.
The Amount of Ice Present
A fourth factor that affects the rate of seafood cooling is the amount of ice that is present. Not all of the cooling potential of ice is able to be transferred directly to the fish. Instead some ice is sacrificed in the process of thermal loss. Thus a successful fishing expedition needs to correctly account not just for the weight of ice that will be needed to properly chill the fish, but also for the ice that will be needed to replace melting ice due to thermal loss. If there is not enough ice present then the fish may not achieve full cooling or may begin to re-warm once ice loss passes the critical point of no longer being able to compensate for thermal loss.
The Ambient Temperature in the Hold
Just as the starting temperature of the fish plays a large role in the cooling rate so too does the local ambient temperature in the hold. As we discussed above not all of the cooling potential in ice can be directly applied to the fish since some will be sacrificed to thermal loss. Naturally this effect will be much higher in a warmer local environment than a cooler one. That is why having a well-insulated storage hold can make such a significant difference in cooling rate and efficiency. A well-insulated container will allow less heat in, thereby reducing thermal loss and allowing for greater ice efficiency.
SEMCO/SEMCOLD LLC is an industry leader in manufacturing and supplying industrial cooling equipment. Our fishing clients can count on us for equipment that gets the job done thoroughly and efficiently while taking their particular space and capacity needs into consideration. Please contact us so that we can design a fully customized system for your fishing needs.