BS ISO 6732:2010 pdf download – Milk and milk products — Determination of iron content — Spectrometric method (Reference method) 5.1 Analytical balance. 5.2 Centrifuge, capable of producing a radial acceleration of 2 500g, with tubes of capacity at least 150 ml. 5.3 Grinding device, appropriate to the nature of the sample. 5.4 Sieve, nominal size of openings 500 µm, ISO 565 [1] , made of iron-free material. 5.5 Water baths. 5.6 Micro-burners or electric heaters, which do not emit iron-containing particles. 5.7 Digestion flasks (Kjeldahl), capacity approximately 70 ml, with ground-glass stoppers, calibrated on the lower part of the neck at 50 ml. 5.8 Glass beads, preferably made of quartz, which do not release iron during the digestion procedure (see 8.2.1). 5.9 Measuring cylinders, capacities 5 ml, 10 ml and 25 ml, ISO 4788 [6] . 5.10 Graduated pipettes, capacities 1 ml, 2 ml and 5 ml, graduated in divisions of 0,1 ml, ISO 835 [4] . 5.11 One-mark pipettes, capacities 1 ml, 2 ml, 3 ml, 4 ml, 5 ml, 10 ml and 25 ml, ISO 648 [2] class A. 5.12 Spectrometer, suitable for measuring absorbance at 533 nm, equipped with cells of optical pathlength 10 mm. 6 Sampling IMPORTANT — Avoid contamination by iron. Store glass sampling jars in 10 % mass fraction nitric acid solution. Rinse them thoroughly and dry before use. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707|IDF 50 [3] . It is important that the laboratory receive a truly representative sample which has not been damaged or changed during transport or storage 7 Preparation of test sample IMPORTANT — Avoid contamination by iron. 7.1 Milk,skimmed milk and whey Bring the sample to (20±2)°C and mix carefully. lf, in the case of milk, the fat is not evenly dispersed, heatthe sample slowly to 40 °℃, mix gently by inversion only, and cool quickly to (20 ±2)°℃. 7.2Buttermilk lf necessary, remove butter granules. Bring the sample to (20±2)C and mix carefuy, immediately beforeweighing (see 8.1.1). 7.3 Plain yogurt and skimmed yogurt Bring the sample to (20±2) ℃ and mix carefully. lf serum separates, stir vigorously,immediately beforeweighing (see 8.1.1). 7.4Cream Bring the sample to (20±2) °℃.Mix or stir thoroughly, but not so vigorously as to cause frothing or churning.lf the cream is very thick, or if the fat is not evenly dispersed, warm...

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