Carbonate in fish and seafood
How to analytically detect water-binding additives in unprocessed fish and seafood products
Apr. 2021. In order to compensate for water losses and increase the net weight, fresh fish and fish products are sometimes treated with water-binding additives. However, the additive carbonate is not permitted in untreated fish and fish products. Eurofins can determine the content of carbonate by headspace GC-MS via the CO2 released during the analysis and report it, calculated as sodium carbonate.
Use of carbonate in fish and fish products
Depending on the fish species, the natural water content in fillets ranges from 55% to 82%. To compensate for the natural loss of tissue water, especially in frozen fish products, water-binding additives are often added. In addition to some permitted additives such as phosphates or citrates, the use of carbonates is only permitted in processed fish products. However, the product does not always have a label identifying the additives used. In addition, the use in unprocessed fish and unprocessed crustaceans and molluscs is not permitted under Annex II, Part E of Regulation (EC) No. 1333/2008.
An indication of carbonate addition in unprocessed products is given, for example, in routine water content determination, if the amount of water added is higher than the amount of water expected to be lost through the loss of tissue water. The increased water retention increases the total weight of the product. Analysis for carbonate can provide deeper insight here.
How carbonate levels in fish and seafood should be assessed
The more carbonate is detected in fish products or seafood, the more likely this is an indication that these products have been treated with additives such as sodium carbonate. To date, however, there is no clear limit at which level an additive is present since carbonate also occurs naturally in smaller amounts. Therefore, a case-by-case consideration is required in each case, taking into account other analytical parameters such as the pH value and the water/protein ratio. Following the ALTS1 guidance "Water additives in unprocessed fishery products" (6/2017, page 12ff, in German), according to which contents of <100 to >500 mg/100 g have been detected in conspicuous samples, Eurofins follows the common practice of the German authorities and uses – depending on the fish species – a content of carbonates, calculated as sodium carbonate, of about 1000 mg/kg as an indicator value.
The limit of determination of the method used by Eurofins is 150 mg/kg, calculated as sodium carbonate. From a toxicological point of view, carbonate is harmless. Since only the water content in the product and thus the weight increases, no negative health effects are to be expected from the addition.
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1 ALTS: Federal German working group of experts in the field of food hygiene and food of animal origin
