Project 24336 - Guidance for the Organisation of a Nitrogen Factor Study

Nitrogen factors (NFs) are analytical factors used to measure meat and fish content (i.e. the amount of meat or fish used) in compound products, and added water in raw meat and fish, and their products. They are used by both enforcement labs (public analysts) to check (QUID) labelling claims on meat and fish content, and by industry to check their raw materials and finished products.

When QUID (quantitative ingredient declaration) was also a requirement in the Codex Labelling Standard, the UK proposed to determine fish content by nitrogen analysis an alternative method to the AOAC coating stripping method in the Codex Standard for Coated Fish Sticks (Fish Fingers) - CODEX STAN 166 - 1989. The Fish Stick Standard was amended to include the nitrogen factor approach (Stubbs and More), and an interim table of NFs included. Industry do not use the AOAC gravimetric method for fish content because it is unreliable when used on flash fried or cooked seafood products.

In 2015, after a long discussion in the CCFFP, the NF approach was retained in the standard, but as a secondary method to the AOAC method. The Codex Committee on Fish and Fishery Products has all but adjourned in 2015, and the responsibility for seafood NF has passed to FAO Fisheries, who have requested a NFstudy protocol to be placed on its website.

The application of a reduced cost design will be demonstrated using data from one or more previous studies. This will use data from a study using a full factorial design, from which a subset will be selected based on the cost reduction method. This will illustrate the effect of the reduced cost design on the overall number of samples and on the uncertainties for a mean nitrogen content.

Additional information:

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