Surveillance Sampling Programme - Method

Sampling 

The informal purchasing of samples was carried out by OL staff who were provided with a shopping list and an area of the country in which to shop.  In general single samples were purchased and this should be taken into consideration in the interpretation of the results. 

All products were purchased at full cost from businesses selling to the general public and the food business operators (FBOs) were not notified that samples were being taken for subsequent testing. The sampling plan focussed on the range of products identified for this project and did not target specific businesses. 

Geographic Distribution

The surveillance sampling was undertaken by OL staff with each OL identifying areas of England and Wales they could purchase samples.  All samples were identified by postcode on a sampling map and areas of the country not covered by OL staff were targeted for on-line purchases where possible.

Retail Types

Representative surveillance was also achieved through sampling across a mix of FBOs. The project aim was to obtain approximately 25% of samples from large FBOs and 75% from smaller FBOs.

Large FBOs included mainstream supermarkets with national coverage or at least across multiple counties, or large food distributors. Smaller retailers included FBOs smaller than this, such as independent retailers, farm stores, stores operating under franchise, and self-service wholesale stores.  

Some samples were purchased via the internet to reflect the consumer migration to on-line shopping and provide national coverage. 

Duplication of Samples

Sampling was coordinated across all five OLs to minimise duplication. OLs were provided with a list of major supermarkets and national FBOs and were only allowed to sample from those specifically allocated to them. 

A similar approach was taken with allocation of main brands for each sample type. 

Sample Integrity 

In order to ensure that surveillance samples were of a suitable standard for testing sampling information was provided for each food commodity/ hazard to ensure that sufficient sample was obtained and that samples were collected, transported and stored under appropriate conditions so as not to adversely impact on the sample integrity or on the quality of the final analytical result. 

Analysis

Each OL holds ISO17025 accreditation and used the most appropriate method for each commodity/hazard analysed using accredited methods if available. All the surveillance samples in this project were analysed using procedures used for official control samples and the integrity of the samples was maintained at all times with comprehensive records to demonstrate chain of custody.

Raw data for all samples including any replicate analysis, positive and negative controls and quality control materials were recorded and all records kept for a period of at least 12 months. The FSA were provided with photographs of packaging for all unsatisfactory samples as well as the final raw data.

In the event that a laboratory identified something that it considered to be non-compliant or a significant hazard to human health then the FSA were informed immediately.