Poultry marketing controls – Inter-laboratory validation of a method to detect previously frozen chicken breasts by determination of HADH activity

• The paper details an improved analytical method for detection of previously frozen chicken breast meat.
• The method is necessary for the official control of poultry under marketing regulations.
• The paper gives results of a collaborative study conducted by LGC involving 24 EU official control laboratories.
• A revised cut-off limit has been validated which enables improved detection of previously chicken breasts.
• This paper will be of interest to the food and analytical communities and will help to protect consumers from food fraud.

EU poultry marketing legislation requires that poultry be marketed either as fresh (chilled) poultry or as frozen (or quick-frozen) poultry. It is not permitted to market poultry which has been previously frozen as if it were fresh. A robust analytical method that is capable of distinguishing between fresh and previously frozen poultry is therefore required for the enforcement of the legislation. A method to detect whether poultry and other meats have been previously frozen was developed and validated by an earlier collaborative study in 1997. The method is based on measuring the HADH activity of intracellular juice pressed from the test samples. The ratio of the HADH activity of sub-samples tested before and after laboratory freezing is compared to a reference cut-off limit, to determine whether the sample has previously been frozen. In a subsequent study in 2010, improvements were made to the analytical procedure and a revised cut-off limit for chicken of 0.5 was determined. The aim of the current study was to validate the improved analytical procedure and the revised cut-off value for chicken via a collaborative trial with 12 European NRLs and 12 UK OCLs. Each laboratory was asked to analyse 24 chicken breast samples and to use the results to determine their thermal history (chilled or previously frozen) according to the SOP provided. All samples were supplied as chilled blind samples. The results of the study showed inter-laboratory variation between the results obtained for chilled and for previously frozen chicken breasts, however despite this, almost all of the samples were correctly identified and reported in terms of their thermal history. Although some reduction in the analytical variability of the method would be beneficial, the results confirmed the suitability of the method and the revised cut-off limit of 0.5 for the official control of marketing of chicken breasts within the EU.