Page 40 - Analytical method for food addtives

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2.5 Appendix: method procedure summaries
For the analysis of soft drinks the method is the same as for sunset yellow but
sample preparation and extraction are modified for flour-based products.

Analysis of flour-based products 2

Sample preparation
Accurately weigh 5 g of sample into a 50 mL beaker. De-fat the sample by stirring
and decanting with 3 × 50 mL portions of petroleum spirit 40–60 at a temperature
no greater than 40 ºC. Discard petroleum spirit and air-dry the sample at ambient
temperature under a fume hood with occasional stirring.

Extraction
Transfer the air-dried de-fatted sample to centrifuge tube. Add 10 mL 0.05 mol/L
phosphate buffer pH 7.0. Add 100 mg α-amylase and incubate at 40 ºC for 2 h in
a shaking water bath or by regular manual shaking. Add 5 mL 0.1 mol/L cetylpy-
ridinium chloride in water, mix and add 10 mL of water-saturated n-butanol.
Shake vigorously for 10 min on mechanical shaker. Centrifuge at 1000 g for
10 min. If a gel forms in the upper organic layer, add 2 mL water-saturated
n-butanol and gently stir into the upper layer, with a glass rod, until emulsion
breaks. Transfer upper organic layer to a 25 mL volumetric flask using a Pasteur
pipette. Repeat the extraction procedure with three further 5 mL portions of water-
saturated n-butanol. Make the combined n-butanol extracts up to 25 mL with
water-saturated n-butanol. Accurately dilute an aliquot of the filtrate with an equal
volume of mobile phase (1L + 1L dilution of mobile phase A and solution B). Mix
and filter a portion through a filter.