The development and evaluation of secondary food reference materials for the determination of cholesterol, fatty acids and selected water-soluble vitamins in foods

The suitability of a number of ‘off-the-shelf’ food items for use as secondary reference materials for incorporation into routine work batches to enhance quality assurance has been evaluated over a 5 month period. The commodities were canned ham (tested for cholesterol and fatty acids), wheat germ (tested for fatty acids, thiamine, riboflavin and niacin), two fish oils (tested for fatty acids) and powdered orange drink vitamin C supplement (tested for ascorbic acid). Foods were purchased locally and analysed using recognized methods. Seven replicate analyses were performed initially on each food to establish homogeneity, with subsequent analyses in triplicate. Overall mean results (±2 s.d.) for the 5 month study were as follows: cholesterol in canned ham, 65 ± 7.2 mg/ 100 g; thiamine in wheatgerm, 1.97 ± 0.26 mg/100 g; riboflavin in wheatgerm, 0.27 ± 0.17 mg/100 g; niacin in wheatgerm, 7.1 ± 0.9 mg/100 g; ascorbic acid in vitamin C supplement, 718 ± 70 mg/100 g; C18:0, C18:1 and C18:2 in wheatgerm, 0.72 ± 0.11, 15.2 ± 0.5 and 57.7 ± 1.4% total fatty acids respectively; C18:0, C18:1 and C18:3 in canned ham, 12.5 ± 0.6, 44.7 ± 1.4 and 0.57 ± 0.12% total fatty acids respectively; C18:0, C20:5 and C22:6 in cod liver oil, 2.4 ± 0.1, 12.6 ± 1.2, and 5.6 ± 0.8% total fatty acids respectively; C18:0, C20:5 and C22:6 in ω3 fish oil, 3.7 ± 0.2, 19.2 ± 0.5, and 12.8 ± 1.4% total fatty acids, respectively. Statistical data were obtained from the multiple analyses, and based on the data generated, the foods tested were shown to have satisfactory homogeneity and stability for use as secondary reference materials over an extended period.