AOAC Methods for Review in Codex STAN 234_11-2018

AOAC Official Methods Listed in CXS 234 for Milk and Milk Products

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D. Determination Pipet 1mLclear filtrate into test tube. Add 1.3mLpyridine, mix, and immediately add 5.7 mL Ac 2 O. Stopper tube, mix thoroughly, and place in 32°C water bath. After 30 min, remove tube from water bath, let cool to room temperature, dry, and measure A against blank at 428 nm. Convert reading to µ g anhydrous citric acid by reference to standard curve.

33.7.22

AOAC Official Method 976.15 Citric Acid in Cheese Colorimetric Method

First Action 1976 Final Action 1977 IDF–ISO–AOAC Method

A. Principle Cheese is dispersed in H 2

′ W W 100 ×

O and protein is precipitated by

Anhydrous citric acid, % =

CCl 3 COOH. Filtrate is treated with pyridine and acetic anhydride and A of yellow color of citric acid complex is measured at 428 nm. B. Apparatus and Reagents ( a ) Test tubes .—16 or 18 × 150mm, with glass or plastic stoppers. ( b ) Trichloroacetic acid solution .—1.836M. Dissolve 300 g CCl 3 COOH in H 2 O and dilute to 1 L. ( c ) Citrate standard solution .—0.003252M. Dissolve 0.9565 g trisodium citrate (C 6 H 5 O 7 Na 3 ⋅ 2H 2 O) in H 2 O and dilute to 1 L. C. Preparation of Test Solution Accurately weigh ca 0.5 g prepared test portion, 970.30 ( see 33.1.06), 920.122 ( see 33.7.01), and 955.30 ( see 33.7.02), and place in porcelain mortar. Disperse by crushing with pestle, adding small portions warm water (60 ° –70°C). Transfer quantitatively to 100 mL volumetric flask with ≤ 50 mL H 2 O. Let cool to room temperature and add 40mLCCl 3 COOH solution, mix by swirling, dilute to volumewith H 2 O, and remix again. Let stand 30 min at room temperature and filter through dry, hard paper. Discard filtrate ( ≥ 10mL) until filtrate is clear.

where W ′ = µ g anhydrous citric acid fromstandard curve and W = g test portion. E. Preparation of Standard Curve Transfer 0, 4, 8, 12, 16, and 20 mL citrate standard solution, B ( c ), to separate 50 mL volumetric flasks and add H 2 O to total volume of ca 25 mL in each. Add 20 mL CCl 3 COOH solution to each, mix by swirling, dilute to volume with H 2 O, and remix. Pipet 1 mL from each flask into separate test tubes to prepare standards containing 0, 50, 100, 150, 200, and 250 µ g anhydrous citric acid, and proceed as in D . Prepare standard curve by plotting A against µ g citric acid. Reference: JAOAC 59, 1142(1976).

CAS-77-92-9 (citric acid)

 2005 AOAC INTERNATIONAL

10/9/2018