Following the recent news in the USA of a product recall of jumbo shrimp from a supermarket because of the presence of sulfites that were undeclared by the supplier, the manufacturer of a new and more effective treatment for prawns is urging American seafood processors and shrimp farmers to consider switching to such safer alternatives.
Shellfish processors, farmers and fishermen have long used sodium metabisulfite as a treatment to prevent ‘blackspot’ in a variety of species of warm and coldwater prawns and shrimps, which is a natural process that discolors the shell after harvesting. Although blackspot is harmless, it does affect the appearance of the prawns, which in turn can make selling the prawns difficult and increases the reject rate.
After harvesting, prawns are still commonly dipped in a sodium metabisulfite solution, masking the development of blackspot. However, sodium metabisulfite is corrosive and can cause serious and expensive damage to equipment in processing factories. But even more serious than that is the well-documented evidence that sulfite based treatments are hazardous to the health of processing workers because the sulphur dioxide fumes released during treatment can harm operator’s airways and lungs. Metabisulfite may also cause asthma attacks and trigger allergic reactions in people who are sensitive to sulfites.
However, there are alternative and more effective treatments that are gaining popularity. One of these is Prawnfresh, which is manufactured by Xyrex, and processors who are already using this liquid solution treatment have found immediate and tangible benefits. The active ingredient in Prawnfresh is safe to use and leaves no chemical residues or taints. It works by inhibiting the enzyme present in the prawn that causes melanotic blackening.
For several years Prawnfresh, which is now available in the US market, has been used with great success by prawn processors and fishermen in Europe and other parts of the world.
Donald Kristensen, managing director of Danish seafood processor Royal Fish Denmark A/S, says he has noticed a big improvement in the welfare of his processing employees after switching from sodium metabisulfite to Prawnfresh.
“All our employees used to have general breathing problems including irritated eyes and nose. This is no longer an issue after changing to Prawnfresh.”
The quality improvements are important too. He says: “Tests have shown that prawns treated with Prawnfresh stay nicer in colour, texture and odour, longer than raw material treated with sodium metabisulfite. We also feel it is a healthier additive for the consumer.”
This is a view supported by Graeme Sutherland, director of Scottish company Whitelink Seafoods, who states: “We switched to Prawnfresh so as to ensure that our valued employees are able to work in a comfortable and safe environment, without encountering any breathing difficulties. We have also found that this alternative treatment gives a better result to the end product in terms of appearance and quality compared with sodium metabisulfite.”
Independent testing by the UK Sea Fish Industry Authority supports these findings. Trials by Seafish in 2005 found that prawns treated with 5% metabisulfite lose some visual qualities through bleaching and attain high sulphite residues, often above the permitted 150ppm. Furthermore, prawns treated with high concentration sodium metabisulfite were found to have poor flavour. Of the various alternative treatments tested, Prawnfresh was found to deliver the best results
John Davis, the managing director Xyrex, the manufacturer of Prawnfresh, says there are compelling reasons for US shellfish processors and wholesalers still using sodium metabisulfite, or importing shellfish that have been treated with the compound, to make the switch to safer and more effective alternative treatments.
“It is better for the consumer and results in an improved product, which in turn makes economic and marketing sense. But most importantly of all, it is particularly heartening to see that more and more shellfish processors and farmers are now using such alternatives because of their concern over exposing their operatives to the potential health risks of sodium metabisulfite.”