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Development and Validation of a Method for the Quantitative Determination of Synthetic Colours in High-Protein Food Matrices


Currently there is no fully quantitative method available to determine red 2G (E128), tartrazine (E102) and sunset yellow (E110) in high protein foods such as fish and meat. This is largely because the colours bind to the protein in the food making them difficult to extract. In order to enforce the maximum levels permitted for these colours, a robust validated method was needed to determine the quantities of these colours in protein rich foods.

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Model sausages, burgers and fish products, dosed with specified colour levels, were made following industry protocols under controlled conditions. They were used to optimise the extraction procedure and to develop the analysis method. Potential methods were evaluated and optimised by comparing the amount of colour recovered. A key step in improving the method was the physical disruption and chemical modification of the protein matrix enabling the food colours to be more easily extracted.

The developed and optimized method for the determination of red 2G in sausages, burgers and tartrazine and sunset yellow FCF in haddock and salmon was validated and can be used to determine whether products contain these colours within the permitted levels.
A simple solvent extraction method with a protein denaturing stage and high pressure liquid chromatography (HPLC) detection was adopted, optimised and validated in house for the extraction and quantification of red 2G in sausages and burgers and tartrazine and sunset yellow in fish products.
The developed method achieved above 70% colour recoveries for non-heat processed samples and is valid for concentrations of red 2G of between 2 to 30 ppm (parts per million) in sausages and burgers; tartrazine of between 2 and 170 ppm in salmon and haddock; and sunset yellow FCF at concentrations of between 40 to170 ppm and 2 to 170 ppm in haddock and salmon respectively.
This method lays down the ground work for the development of a suitable method for the enforcement of legislated limits on the use of specific colours in foods with complex matrices.
Homogeneity work on 20 replicates of six types of sausages showed that the method gave consistent and reliable results.
The validation experiments performed showed that a quantitative method has been developed to determine the level of red 2G in sausages and burgers and also tartrazine and sunset yellow in fish products.
The limits of detection (LOD) of red 2G, sunset yellow FCF and tartrazine on the equipment used were 0.010, 0.010 and 0.048 ppm respectively. The limits of quantification (LOQ) for red 2G, sunset yellow and tartrazine on the equipment used were 0.031, 0.037 and 0.166 ppm respectively.
The method is not valid for the quantitative analysis of heat processed fish.
Find more about this project and other FSA food safety-related projects at the <a href="; target="_blank">Food Standards Agency Research webpage</a>.

Reading Scientific Services, Ltd
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