Determination of the BactoScan Conversion Factor for the United Kingdom
The microbiological quality of almost all commercially produced raw milk in the United Kingdom of Great Britain and Northern Ireland (UK) is determined by flow cytometry using BactoScan equipment. However, European Commission standards for raw milk are laid down as standard plate counts in Regulation (EC) No 853/2004 Annex III, Section IX, hence there is a need to have a conversion factor between the IBC determined by commercial companies, and the TVC cited in legislation. Using methodology based on BS EN ISO 4833:2003, this study undertook to determine the conversion factor. Three commercial laboratories using BactoScan equipment, and accredited to ISO17025 for their use, undertook duplicate analysis of 1,800 routine samples of raw milk from farms across the UK to determine IBC values. In addition duplicate bacterial enumeration of all samples, using BS EN ISO 4833:2003, was undertaken to determine TVCs. Overall, 1,799 valid results were obtained and regression analysis of the IBC against the TVC results, as log10 values, gave the equation:
Log10 (TVC) = 0.9151x Log10 (IBC) – 0.5696 (r² =0.6694).
Hence this relationship constitutes the UK BactoScan conversion factor which is to be used to convert IBC values for raw milk determined in commercial premises into valid TVC results with reference to European Commission legislation.
Desmasures N, M Gueguen. Monitoring the microbiology of high quality milk by monthly sampling over 2 years. J Dairy Res. 1997; 64:271-280 doi:10.1017/s0022029996002130
European Commission. Commission Regulation (EC) No 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs. Http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2005:338:0001:0026:EN:PDF Accessed April 2017.
Gunasekera TS, PV Attfield, DA Veal. A flow cytometry method for rapid detection and enumeration of total bacteria in milk. App Env Microbiol. 2000; 66:1228-1232 doi:10.1128/aem.66.3.1228-1232.2000
Suhren G, HG Walte. First experiences with automatic flow cytometric determination of total bacterial count in raw milk. Int Dairy Fed Bull 2000; 50:249-275.
European Commission. Commission Regulation (EC) No 853/2004 Annex III, Section IX. Http://eur-lex.europa.eu/legal- content/EN/TXT/?uri=celex%3A32004R0853R(01)#ntr27-L_2004226EN.01004001-E0004. Accessed April 2017.
European Commission. Food and Veterinary office, EU. Final report of an audit carried out in the United Kingdom from 08 to 19 April 2013 in order to evaluate the follow-up action taken by the competent authorities with regard to official controls related to the safety of food of animal origin, in particular milk and dairy products. http://ec.europa.eu/food/fvo/act_getPDF.cfm?PDF_ID=10619 Accessed April 2017.
Food Standards Agency. Response of the Competent Authorities of the United Kingdom to report ref. DG(SANCO)/2013-6872-MR. 2013. http://ec.europa.eu/food/fvo/act_getPDFannx.cfm?ANX_ID=7365 Accessed April 2017.
BSI. Microbiology of food and animal feeding stuffs -- Horizontal method for the enumeration of microorganisms -- Colony-count technique at 30 degrees C. BS EN ISO 4833:2003. British Standards Institute, London. 2003.
BSI. Milk -- Quantitative determination of bacteriological quality -- Guidance for establishing and verifying a conversion relationship between routine method results and anchor method results. BS ISO 21187:2004. British Standards Institute, London. 2004.