BS EN 14569:2004 – This is an uncontrolled copy. Ensure use of the most current version of this document by searching British Standards Online at bsonline.techindex.co.uk

Samples that are identified as having high endotoxin levels but low levels or no detectable GNB show an unusual microbiological profile. Thus, when log 1 0 EU/g – log 1 0 cfu GNB/g is greater than 0 the sample is suspected of having been irradiated and should be subjected to further radiation specific tests. Samples that are identified as having high endotoxin levels and similarly high Gram negative bacteria counts show a normal microbiological profile.
, when log 1 0 EU/g – log 1 0 cfu GNB/g is lower or equal 0, the sample is not suspected of having been irradiated. Samples that are identified as having endotoxin titres log 1 0 EU/g of lower than 2,0 and low levels of GNB, i.e. log 1 0 cfu GNB/g of lower than 2,0 should be considered inconclusive and should be subjected to further radiation specific tests. 6 Limitations This method can give only an indication of a possible treatment by ionising radiation.
A high amount of dead microorganisms in comparison to the viable fraction can be due to several other reasons. It is therefore necessary to confirm a possible treatment by ionising radiation by a standardized reference method for the detection of irradiated foods. The method is of particular use to routine microbiological laboratories, which may be involved in the examination of foods. It should be noted that freezing after irradiation can influence the ratio of GNB to EU due to the loss of viability of microorganisms. Conversely, re-growth of bacterial flora can occur in irradiated samples which are stored unfrozen.
7 Validation The method was developed by the UK Ministry of Agriculture, Fisheries and Food, Food Science Laboratory, Norwich (FSL) and validated by collaborative trial [4], [5], [6]. Twenty UK laboratories participated in the trial (1 6 Public Analyst Laboratories, 3 Public Health Laboratories and FSL). A commercial poultry processor supplied a single batch of boneless chicken breasts with skin and a single batch of boneless chicken breast fillets. Within 24 h of slaughter, both batches of chicken were transported from the processing plant, under refrigeration conditions (<5 °C), to a commercial irradiation facility. The batch of chicken breasts were subdivided; one third of the batch were retained as control (unirradiated) samples; one third were irradiated at an overall average dose of 2,5 kGy and the remainder irradiated at 5 kGy. The skinless chicken breast fillets were sub-divided into two. Half were retained as controls and the remaining half were irradiated at 2,5 kGy. Samples were irradiated using a Cobalt 60 source. Amber perspex dosimeters 1 ) were used to estimate the dose received by measuring spectrometrically a change in absorbance at 530 nm. All chicken pieces were randomly coded and packaged in insulated containers under chill conditions. Samples were then delivered by overnight carrier to arrive at participating laboratories the following morning. Participants were instructed to commence the analysis immediately upon arrival of the samples. Each participant received 1 0 samples for analysis comprising control samples of chicken breasts with and without skin; chicken breasts with skin irradiated at 2,5 kGy and 5 kGy and skinless breasts irradiated at 2,5 kGy. All samples were dispatched randomly as blind „pairs‟. Participants were asked to examine each sample only once and report the results obtained from the LAL test and enumeration of GNB. Using the evaluation criteria detailed in Clause 5, 1 00 % of all unirradiated samples, 97 % of chicken with skin irradiated at 2,5 kGy, 82 % of those irradiated at 5 kGy and 88 % of the skinless fillets irradiated at 2,5 kGy were correctly identified. All other samples were reported as „inconclusive‟ due to the very low EU titres obtained. BS EN 14569:2004 – This is an uncontrolled copy. Ensure use of the most current version of this document by searching British Standards Online at bsonline.techindex.co.uk