Lobsters are one of the most sought after of all types of seafood, even considered by some to be a luxurious delicacy. This in turn means that they command a premium price and can be quite lucrative for lobster fishermen. However for lobsters to be so thoroughly enjoyed by the public and profitable to the fishermen, it is crucial that they be kept alive until they are ready to be cooked. This requires proper and meticulous cooling and storage.
Lobsters Must be Kept Alive Prior to Cooking
With most types of meat, particularly non-seafood, there is a much longer window of time possible from the moment when the creature dies until it must be cooked. Often simply cleaning the meat and then freezing or refrigerating it short-term until the consumer is ready to cook and eat it is perfectly safe and doesn’t compromise the taste or quality. However, that is not the case at all with lobster.
As soon as a lobster dies its body begins to undergo a rapid chemical change that will quickly render the meat both unsafe and unappetizing to eat. Thus the lobster must be kept alive after it is caught, while in transit to the market or restaurant where it will be sold, and even while it is waiting for the final consumer to purchase it. Alternatively, the lobster can be cooked and frozen for later consumption, but regardless it must be kept alive until it is ready to be cooked. This will require specially designed tanks with carefully monitored water temperature and composition.
Saltwater Is Essential
Lobsters are marine animals that are caught in salty ocean water. Thus in order for the lobster to remain alive it must be kept in saltwater that closely mimics the conditions and composition of natural seawater. The optimum salinity range for lobsters is about 29-35 parts per thousands of salt. However, there is more to seawater than just salt and while merely replicating the correct salinity may be somewhat effective for keeping lobster alive short-term, it is less effective for long-term storage since actual seawater contains a wide variety of trace minerals. Even minerals that exist in tiny ratios of parts per million can still play an important role in long-term lobster survival. For this reason many fishermen choose to utilize a storage system that pumps actual seawater into the lobster tanks.
Natural seawater has a pH of about 7.5 to 8.4 and thus the lobsters should also be stored in an environment that has a pH of no lower than 5 and no greater than 9. However, the lobster themselves will also have an impact on the pH of the water because lobsters excrete ammonia, which will make the water more acidic as it builds up. Ammonia is also toxic to lobsters and must be removed. Thus in addition to pumping natural seawater into the lobster tanks, many fishermen also utilize an open rather than closed water system so that the ammonia will be naturally removed. If a closed system is used then some type of filter will need to be used. One solution is a biofilter containing bacterial colonies that will convert the ammonia into nitrite. However, simply placing broken mollusc shells in the filter will also help curtail a pH decline.
Lobsters Should be Kept Cool
Lobsters should kept in water that falls between about 40°F and 50°F. There are pros and cons to different temperature levels within that range. At higher temperatures the lobster are more active, which in turn often makes them much more enticing to would-be consumers. However, as temperatures rise so too does the need for very careful and precise control over water salinity levels, pH levels, waste removal, and composition. That is because at lower temperatures the lobsters’ metabolic rate decreases and they thus produce less waste and are less sensitive to fluctuations in water composition.
However, when lobsters are caught in the summer they have already acclimated to warmer temperature levels and should thus be introduced to lower temperature levels more gradually to prevent a shock to their systems. Generally they should be kept within a temperature differential of about 15° F. If water temperatures are warmer or colder than 15° F compared to the temperature they are already acclimated to then there is the potential that the sudden change may kill them.
Storage Tank Considerations
Copper is extremely lethal to lobsters. The typical amount of copper in seawater is about 0.003 ppm; a lethal threshold for lobsters is only about 0.056 ppm. Thus it is crucial that their storage tanks do not contain any copper. Likewise copper coiling is often used in refrigeration systems; however, this too is potentially lethal to lobsters and thus coils should instead be made of black iron, galvanized iron, titanium, stainless steel, or plastic. Each of these different materials will have its own set of pros and cons in terms of expense, maintenance, and heat conductivity.
Lobsters should not be allowed to be in direct contact with cooling surfaces and generally an intermediary surface like a baffle plate should be used. Alternatively the lobsters may be placed in a separate tank from the refrigerant coils to prevent accidental contact. The water should be agitated to ensure good water-to-coil friction, which will increase efficiency compared to allowing the coils to cool the water passively.
It is typically best to consult a refrigeration expert about the storage tank configuration because improper placement of air-cooled condensers and other components could result in heat being released into the system or in other inefficiencies that compromise function.
Semco develops efficient, high quality cooling systems that are ideal for safely storing live lobster. Our systems can be customized to reflect the capacity demands and other priorities of our customers. Our goal is to ensure that your lobsters reach the final consumer while still live and fresh.