Butter can be illegally adulterated with less expensive vegetable fats or beef tallow and lard. Various EEC collaborative trials of the Group of Experts on Dairy Products (DG VI) have shown that the determination of the triglyceride composition along with the use of triglyceride formulae can be regarded as a very efficient means for the detection of adulteration, and a routine method was made available and adopted as official EEC method. Referring to this EEC-method since the 1st of March 1995 from each manufacturer offering butter for intervention two samples per year have to be analysed for non-milk fats. Taking intra-Community trade, export and import into account, it is of great importance that different laboratories obtain comparable results when a butter (i.e. butter fat) sample is analysed. Satisfactory results can, however, only be obtained, if a certified butter fat reference material for triglyceride analyses is available.
The overall objective of the project was to prepare a butter fat reference material (RM) with a medium composition and sufficient stability. Thus, a cream resulting from feeding conditions between barn feeding and pasture feeding had to be used. Since application of the triglyceride formulae used in the official EEC-foreign fat detection method affords the evaluation of triglycerides with the acyl-C-numbers 24 - 54 and cholesterol, the RM should be certified for these parameters. The certified reference butter fat is intended to support official methods and directives.
After preparation of 1900 ampoules with anhydrous butter fat, all homogeneity and stability studies of the RM were completed with satisfactory results. Even after 2 years neither changes in triglyceride composition or refractive index occured, nor were the predetermined limits for the peroxide value and the content of free fatty acids exceeded at any storage temperature.The evaluation of the following certification excercise with 13 participating EU laboratories resulted in the certification of the mass fractions of 16 triglycerides (separated by acyl-C-number) and free cholesterol (including all minor sterols).
During the project 10 l of anhydrous butter fat were prepared and filled into ampoules (5 ml) under conditions which ensure maximum homogeneity and stability of the material. After a homogeneity study of the ampouled material by analysing the triglyceride composition of every 50th ampoule, stability studies were carried out for 24 months. With given time intervals samples stored at -18°C, 4°C, 20°C and 37°C (only in the first month) were analysed for triglyceride composition, content of free fatty acids, refractive index and peroxide value. After conclusion of homogeneity and stability tests, an international certification exercise with laboratories from the different EU Member States was carried out.