Preventing the breakdown of tyrosine by the enzyme tyrosinase is vital to the seafood industry due in large part to unfavorable consumer response to melanotic shrimp. The use of sulfiting agents such as sodium bisulfite and sodium metabisulfite or formulations with sulfiting agents has been the traditional treatment method for retarding this breakdown in fresh, frozen, or thawed crustaceans since the early 1950’s.[4] E. A. Fieger’s 1951 article provides historical reasoning, “In the past decade shrimp production has increased considerably through the use of larger boats which were able to extend the off-shore fishing areas. This fact has resulted in longer storage on the trawlers and a longer period of time between catching the shrimp and their ultimate consumption.” Thus, sulfiting agents, particularly sodium bisulfite, were introduced in an effort to yield a more valuable harvest. This practice continues today, and companies such as WorldwideJanitor.com have made sodium bisulfite widely available to shrimpers.
However, nonsulfite solutions containing 4-hexylresorcinol have gained recent popularity. The quest for nonsulfite solutions began in response to potential food safety hazards such as allergic reactions amongst hyper-sensitive asthmatics. It is also an attempt to eliminate the tendency of shrimpers to over-dilute sulfite mixtures (more than the USFDA recommended 1.25%), thus creating unsafe working and storage conditions. This quest has produced favorable alternatives such as the commercial product, EverFresh, which contains 4-hexylresorcinol. Nevertheless, studies have shown varying levels of effectiveness depending upon species of shrimp, and 4-hexylresorcinol solutions have proven to be quite ineffective as a treatment for deepwater pink shrimp (Parapenaeus longirostirs).[5]
In an April 1986 study, Dr. W. Steven Otwell and Dr. Marty Marshall concluded that a 1.25% sodium bisulfite dip (1 minute) was superior in preventing melanosis. Their research records varying treatments using single compounds or mixtures including: Calcium Chloride, Ascorbic Acid, Citric Acid, Phosphoric Acid, Sodium Hexametaphosphate, and Hydrogen Peroxide.[6] The study further supports diverse levels of melanin in crustaceans, observing inconsistent levels of melanosis in untreated white shrimp (Panaeus setiferus) that made it too unpredictable to include as a sample. This calls into question any study that does not show results in deepwater pink shrimp as it is difficult to determine whether cause of results was due to species or treatment. Otwell and Marshall, therefore, focused their research on the more consistent pink shrimp (Panaeus duorarum) species, and found no treatment to be as effective as sodium bisulfite.