Nitrogen Factors for Cod Ingredient in Fish Products

Analytical Methods Committee, Royal Society of Chemistry, Burlington House, Piccadilly, London W1J 0BA

Summary

A Code of Practice on the declaration and the labelling of fish content in fish products was drawn up by participants from Industry and Enforcement Agencies. The Code currently contains interim nitrogen factors to calculate the amount of fish ingredient which have been obtained by considering the available data on nitrogen content of fish straight from the sea and the effects of good manufacturing practice (GMP). There was a need to carry out experimental trials to determine the actual nitrogen content of GMP products to verify or replace these interim values.

This paper reports the trials carried out between December 2001 and September 2003 to determine the nitrogen factor of fish ingredient, in double frozen fillet and mince blocks produced under GMP in the UK. Sampling took into account both seasonality and raw-material catch area. In addition, samples were taken at key stages of fish block manufacture to determine the effect of processing. Trials were also carried out to determine the nitrogen factors of the equivalent single and double frozen blocks imported into the UK from five different countries.

Processing had a significant effect on nitrogen contents which followed a consistent pattern within a given sample type. In fillet block production, the conversion from a raw material control fillet to a commercial fillet ingredient resulted in no change or an increase in nitrogen content, whilst the conversion of commercial fillet ingredient to final block resulted in a decrease in nitrogen content. Mince block production showed a different pattern. The conversion from raw material control to mince ingredient resulted in a decrease in nitrogen content, whilst the conversion of mince ingredient to the final block resulted in an increase in nitrogen content.

For UK manufactured blocks the nitrogen content of fillet and mince ingredient was found to be 2.88% and 2.74% respectively.

For imported blocks the overall nitrogen content for those made from fillet or mince was found to be 2.74% and 2.67%. There was no statistically significant difference between single or double frozen blocks. Although the values for imported blocks were lower than those produced in UK, these differences were not significantly different.

Based on these findings, recommended values for the nitrogen factor for cod ingredient in cod products have been agreed by the Nitrogen Factors Sub-Committee.

The Analytical Methods Committee has received, and approved for publication, the following report from its Nitrogen Factors Sub-Committee.

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