GB 5009.9-2023National food safety standard - Determination of starch in foods (English PDF)

3.1 Reagents

3.1.1 Iodine (I2).

3.1.2 Potassium iodide (KI).

3.1.3 alpha-amylase. EC 3.2.1.1, enzyme activity >= 1.6 U/mg.

3.1.4 Absolute ethanol (C2H5OH) or 95 % ethanol.

3.1.5 Petroleum ether. the boiling range is 60 degrees C ~ 90 degrees C.

3.1.11 Copper sulfate (CuSO4 . 5H2O).

3.1.12 Potassium sodium tartrate (C4H4O6KNa . 4H2O).

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

3.2 Preparation of reagents

3.3 Reference material

D-anhydrous glucose (C6H12O6, CAS number. 50-99-7). purity >= 98 %, or a reference

material certified by the country and awarded a reference material certificate.

3.4 Preparation of standard solution

Glucose standard solution (1.00 mg/mL). Accurately weigh 1 g (accurate to 0.001 g) of

D-anhydrous glucose that has been dried at 98 degrees C ~ 100 degrees C for 2 hours, add water to

dissolve, then add 5 mL of hydrochloric acid, and dilute to 1000 mL with water.

4.4 Reflux device, accompanied with a 250 mL Erlenmeyer flask.

4.5 Tissue masher.

4.6 Electric stove.

4.7 Burette. 25 mL.

5.1 Preparation of samples

Take the edible part of the sample and grind it, pass it through a 40 mesh sieve, and

weigh 2 g ~ 5 g (accurate to 0.001g) of it. If the sample is not easy to grind, add an

appropriate amount of water accurately and record the mass; after homogenization,

weigh a sample equivalent to 2 g ~ 5 g of the original sample.

5.2 Microsugar test method

Take 2 mL of the washing liquid in a small test tube, add 4 drops of alpha-naphthol ethanol

solution (10 g/L), and slowly add 1 mL of concentrated sulfuric acid along the tube wall.

5.3 Determination

5.3.1 Calibration of alkaline copper tartrate solution

Pipette 5.00 mL of alkaline copper tartrate solution A and 5.00 mL of alkaline copper

tartrate solution B, place them in a 150 mL Erlenmeyer flask;

5.3.4 Determination of reagent blank

At the same time, measure 20.00 mL of water and the same amount of amylase solution

as when processing the sample solution, and carry out a reagent blank test according to

the back titration method. That is, use the glucose standard solution to titrate the reagent

blank solution to the end point, and record the mass of glucose contained in 10 mL of

the sample solution, which is equivalent to the difference between the volume

consumed and the volume of the glucose standard solution consumed during calibration.

Calculate the glucose content in the reagent blank according to formula (5) and formula

(6).

6.1 The mass of glucose, which is equivalent to the alkaline copper tartrate solution

used for calibration.

6.3 When the starch concentration in the sample is too low, the glucose content is

calculated according to formula (3) and formula (4).

6.5 The starch content in the sample is calculated according to formula (7).

9.1 Reagents

9.2 Preparation of reagents

9.2.1 Methyl red indicator solution (2 g/L). Weigh 0.20 g of methyl red, dissolve in 95 %

ethanol and dilute to 100 mL.

9.2.2 Sodium hydroxide solution (400 g/L). Weigh 40 g of sodium hydroxide, add water

to dissolve and dilute to 100 mL.

9.2.6 Ethanol solution (85 %, volume fraction). Take 85 ml of absolute ethanol, add

water to dilute to 100 mL and mix well. It can also be prepared with 95 % ethanol.

9.2.7 Ethanol solution (40 %, volume fraction). Take 40 ml of absolute ethanol, add

water to dilute to 100 mL and mix well. It can also be prepared with 95 % ethanol.

9.3 Reference material

Same as 3.3.

9.4 Preparation of standard solution

Same as 3.4.

10.5 Tissue masher.

10.6 Electric stove.

10.7 Burette. 25 mL.

11.1 Preparation of samples

Take the edible part of the sample and grind it, pass it through a 40 mesh sieve, and

weigh 2 g ~ 5 g (accurate to 0.001g) of it. If the sample is not easy to grind, add an

appropriate amount of water accurately and record the mass; after homogenization,

weigh a sample equivalent to 2 g ~ 5 g of the original sample. Place it in a funnel with

folded slow filter paper, first wash it with 50 mL of petroleum ether or diethyl ether in

five times to remove the fat (it can use a glass rod to stir gently to disperse the sample),

and discard the petroleum ether or diethyl ether, then wash it with ethanol solution

(85 %, volume fraction) in several times to remove soluble sugars until the microsugar

test result is negative.

11.2 Microsugar test method

Same as 5.2.

11.3 Determination

Same as 5.3.

15.1 Reagents

15.2 Preparation of reagents

15.2.1 Potassium hydroxide-ethanol solution. Weigh 50 g of potassium hydroxide,

dissolve in 95 % ethanol and dilute to 1000 mL.

15.2.2 Ethanol solution (80 %, volume fraction). Take 80 ml of absolute ethanol, add

water to dilute to 100 mL and mix well. It can also be prepared with 95 % ethanol.

15.2.7 Alkaline copper reagents.

Solution a. Weigh 25 g of copper sulfate, and dissolve in 100 mL of water.

15.2.8 Potassium iodide solution. Weigh 10 g of potassium iodide, dissolve in water

and dilute to 100 mL.

15.2.9 Hydrochloric acid solution (7.5 mol/L). Take 100 ml of hydrochloric acid, and

dilute to 160 mL with water.

15.2.10 Sodium thiosulfate standard solution (0.1 mol/L). Prepare according to GB/T

5009.1.

16.1 Balance. the minimum division is 10 mg.

16.2 Constant temperature water bath. it can be heated to 100 degrees C.

16.5 Electric stove.

16.6 Burette. 25 mL.

17.1 Preparation of samples

Take a representative sample of no less than 200 g, grind it twice with a meat grinder

and mix well.

17.2 Starch separation

Weigh 25 g of the sample (accurate to 0.01g, starch content is about 1 g) in a 500 mL

beaker, add 300 mL of hot potassium hydroxide-ethanol solution, stir evenly with a

glass rod, cover with a watch glass, and heat on a boiling water bath for 1 hour, stirring

occasionally.

17.4 Hydrolysis

Drill holes in the filter paper, use 100 mL of 1.0 mol/L hydrochloric acid solution to

wash the precipitate completely into a 250 mL beaker, cover with a watch glass, and

hydrolyze in a boiling water bath for 2.5 h, stirring occasionally.

17.5 Determination

Accurately take a certain amount of filtrate (V4) and dilute it to a certain volume (V5),

then take 25.00 mL (preferably containing 40 mg ~ 50 mg of glucose) and transfer it

into an iodine volume bottle, add 25.00 mL of alkaline copper reagent, install a

condenser tube, and boil on an electric stove within 2 min.

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