GB 5009.7-2016National food safety standard - Determination of reducing sugar in foods (English PDF)

3.1 Reagents

3.1.1 Hydrochloric acid (HCl).

3.1.2 Copper sulfate (CuSO4 · 5H2O).

3.1.8 Potassium ferrocyanide [K4Fe(CN)6 · 3H2O].

3.2 Preparation of reagents

3.2.1 Hydrochloric acid solution (1 + 1, volume ratio). WEIGH 50 mL of hydrochloric

acid; ADD 50 mL of water; MIX well.

3.2.2 Alkaline copper tartrate solution A. WEIGH 15 g of copper sulfate and 0.05 g of

methylene blue; DISSOLVE in water; DILUTE to 1000 mL.

3.2.3 Alkaline copper tartrate solution B. WEIGH 50 g of potassium tartrate and 75 g

of sodium hydroxide; DISSOLVE in water; ADD 4 g of potassium ferrocyanide; after

completely dissolved, DILUTE with water to 1000 mL; STORE in a glass bottle with

rubber stopper.

3.3 Standards

3.3.1 Glucose (C6H12O6)

CAS. 50-99-7, purity >= 99 %.

3.3.2 Fructose (C6H12O6)

CAS. 57-48-7, purity >= 99 %.

3.3.3 Lactose (containing water) (C6H12O6 · H2O)

CAS. 5989-81-1, purity >= 99 %.

3.3.4 Sucrose (C12H22O11)

CAS. 57-50-1, purity >= 99 %.

3.4 Preparation of standard solutions

3.4.1 Glucose standard solution (1.0 mg/mL). accurately WEIGH 1 g of glucose that

has been dried in the oven at 98 °C ~ 100 °C for 2 h; ADD water to dissolve; ADD 5

mL of hydrochloric acid solution; DILUTE with water to 1000 mL. This solution is

equivalent to 1.0 mg of glucose per milliliter.

4.1 Balance. with division of 0.1 mg.

4.2 Water bath pot.

4.3 Temperature-adjustable electric furnace.

5.1 Preparation of samples

5.1.1 Starch-containing foods. WEIGH 10 g ~ 20 g (accurate to 0.001 g) of crushed or

mixed sample; PLACE in a 250-mL volumetric flask; ADD 200 mL of water; HEAT in

5.1.2 Alcoholic beverages. WEIGH 100 g (accurate to 0.01 g) of mixed sample; PLACE

in an evaporative dish; NEUTRALIZE with sodium hydroxide solution to neutral;

EVAPORATE in the water bath to 1/4 of the original volume; TRANSFER to a 250-mL

volumetric flask; slowly ADD 5 mL of zinc acetate solution and 5 mL of potassium

ferrocyanide solution; ADD water to the scale;

5.2 Calibration of alkaline copper tartrate solution

PIPETTE 5.0 mL of alkaline copper tartrate solution A and 5.0 mL of alkaline copper

tartrate solution B; PLACE in a 150-mL Erlenmeyer flask; ADD 10 mL of water; ADD 2

~ 4 glass beads. ADD dropwise about 9 mL of glucose (3.4.1) [or other reducing sugar

standard solution (3.4.2, or 3.4.3, or 3.4.4)] from the burette;

5.3 Prediction of sample solution

PIPETTE 5.0 mL of alkaline copper tartrate solution A and 5.0 mL of alkaline copper

tartrate solution B; PLACE in a 150-mL Erlenmeyer flask; ADD 10 mL of water; ADD 2

~ 4 glass beads. HEAT to boil in 2 min; KEEP boiling and ADD dropwise the sample

solution from the burette at a speed of from fast to slow, and keep boiling state, until

the solution color becomes lighter. TITRATE at a rate of 1 drop/2 s until the blue of the

solution fades, that is the end point. RECORD the volume of the sample solution

consumed.

5.4 Determination of sample solution

PIPETTE 5 mL of alkaline copper tartrate solution A and 5.0 mL of alkaline copper

tartrate solution B; PLACE in a 150-mL Erlenmeyer flask; ADD 10 mL of water; ADD 2

~ 4 glass beads; ADD dropwise the sample solution 1 mL less than the predict volume

from the burette to the Erlenmeyer flask. HEAT to boil in 2 min;

10.1 Reagents

10.1.1 Hydrochloric acid (HCl).

10.1.2 Sodium hydroxide (NaOH).

10.1.3 Copper sulfate (CuSO4 · 5H2O).

10.2 Preparation of reagents

10.2.1 Hydrochloric acid solution (3 mol/L). MEASURE 30 mL of hydrochloric acid;

DILUTE with water to 120 mL.

10.2.2 Alkaline copper tartrate solution A. WEIGH 34.639 g of copper sulfate; ADD

appropriate amount of water to dissolve; ADD 0.5 mL of sulfuric acid; ADD water to

dilute to 500 mL; FILTER with refined asbestos.

10.2.6 Refined asbestos. SOAK asbestos in hydrochloric acid solution for 2 d ~ 3 d,

WASH with water. SOAK in sodium hydroxide solution for 2 d ~ 3 d, DISCARD the

solution. SOAK in hot alkaline copper tartrate solution B for several hours, WASH with

water. SOAK in hydrochloric acid solution for several hours, WASH until it is not acid.

ADD water and SHAKE, so that it becomes fine slurry of soft fibers. SOAK in water

and STORE in glass bottle, which can be used for paving the Gooch crucible.

10.3 Standards

Potassium permanganate (KMnO4), CAS. 7722-64-7, excellent regent or higher.

11.1 Balance. with division of 0.1 mg.

11.5 25 mL Gooch crucible or G4 vertical crucible.

11.6 Vacuum pump.

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