AOAC Official Method 941.06 Casein in Malted Milk and Chocolate Malted Milk

First Action 1941
Final Action
Place 10 g test portion in 250 mL (or larger) centrifuge bottle and extract with two 100 mL portions petroleum ether by shaking until uniform, centrifuging, and decanting. To dry residue add exactly 200mL3%Na2C2O4 solution (w/v). Shake occasionally over 4 h period. Centrifuge 15 min at high speed (1800 rpm if Size 1 type SB centrifuge is used). Pipet 50 mL supernate (100 mL for chocolate malted milk product) into 250 mL beaker. Add 50 mL paper pulp suspension (1 filter paper) and 2 mL CH3COOH dropwise with constant stirring. Set beaker in 45–50°CH2O15 min. Cool to room temperature and filter with moderate suction through 7 cm Büchner, previously fitted with S&S 589 white ribbon paper, or equivalent, and overlaid with layer of paper pulp. Wash precipitate 2 or 3 times with coldH2O. (Filtrate should be clear, or nearly so. If first portions of filtrate are not clear, repeat filtration and finish washing precipitate.) DetermineNin washed precipitate and filter paper as in 991.20 (see 33.2.11), and multiply by 6.38 to obtain equivalent casein. Correct result for blank on reagents and paper pulp.

Reference: JAOAC 24, 546(1941).
CAS-9000-71-9 (casein)