Page 349 - Analytical method for food addtives

236 Analytical methods for food additives

Procedure
Preparation of the sample test solution
Clear liquid products (e.g. lemonades, cola, beverages)
Dilute 20 mL of the sample in a 100 mL volumetric flask with water. Filter the
solution through a membrane filter of pore size 0.45 µm before injection.

Cloudy liquid products (e.g. juices, flavoured milk drinks)
Dilute 20 mL of the homogenised sample in a 100 mL volumetric flask with 50 mL
water, add 2 mL of Carrez solution No. 1, mix and add 2 mL of Carrez solution No.
2. Shake vigorously and allow the solution to stand at room temperature for
10 min. Dilute to the mark with water. Filter through a fluted filter paper,
discarding the first 10 mL of the filtrate. Pass the filtrate through a membrane filter
of pore size 0.45 µm before injection.
To make allowance for the volume of any precipitate, if the fat-free insoluble
matter in the sample volume (here 20 mL) exceeds approximately 3 g, it is
advisable to centrifuge the clarified sample mixture for 10 min at least 1400 g
before filtering it quantitatively into the 100 mL volumetric flask. Wash the settled
matter twice with water and centrifuge again, collect each of the supernatants in the
100 mL volumetric flask and then dilute the solution to the mark with water. This
procedure may also be followed when the amount of insoluble matter is less than
3g.

Jams, preserves, marmalades and related products (except fruit curds)
Weigh, to the nearest 1 mg, about 20 g of homogenised sample into a 100 mL
volumetric flask. Add about 60 mL of water and place the flask in an ultrasonic
bath at 40 °C for 20 min. The temperature should not exceed 40 °C since aspartame
can be degraded.
Cool the solution to room temperature. Add 2 mL of Carrez solution No. 1, mix
and then add 2 mL of Carrez solution No. 2. Shake vigorously and allow the
solution to stand at room temperature for 10 min. Dilute to the mark with water.
Filter the solution through a fluted filter paper, discarding the first 10 mL of the
filtrate. Pass the filtrate through a membrane filter of pore size 0.45 µm before
injection.
To make allowances for the volume of any precipitate, if the fat-free insoluble
matter in the initial sample mass exceeds approximately 3 g, it is advisable to
centrifuge the clarified sample mixture for 10 min at least 1400 g before filtering
it quantitatively into the 100 mL volumetric flask. Wash the settled matter twice
with water and centrifuge again, collect each of the supernatants in the 100 mL
volumetric flask and then dilute the solution to the mark with water. This procedure
may also be followed when the amount of insoluble matter is less than 3 g.

Semi-solid and solid products (e.g. curd cheese desserts, yogurt products,
delicatessen salads, except custard powder)
Weigh, to the nearest 1 mg, about 10 g to 20 g of the thoroughly homogenised
sample into a 100 mL volumetric flask. Add about 50 mL of water and place the