GB/T 5009.7-2008 English PDF (GBT5009.7-2008)

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GB/T 5009.7-2008: Determination of reducing sugar in foods
GB/T 5009.7-2008
ICS 67.040
C 53
GB
NATIONAL STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
Replacing GB/T 5009.7-2003
Determination of reducing sugar in foods
ISSUED ON. NOVEMBER 21, 2008
IMPLEMENTED ON. MARCH 1, 2009
Issued by.
General Administration of Quality Supervision, Inspection
and Quarantine of the People’s Republic of China;
Standardization Administration of the People’s Republic of
China
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle... 4
3 Reagents ... 4
4 Instruments ... 6
5 Analytical procedure ... 6
6 Result calculation ... 8
7 Principle... 9
8 Reagents ... 9
9 Instruments ... 10
10 Analytical procedure ... 11
11 Precision ... 23
Foreword
This Standard replaces GB/T 5009.7-2003 of Determination of reducing sugar in foods.
Compared with GB/T 5009.7-2003, main changes of this Standard are as follow.
— The detection limits are included;
— The categories of food samples are redefined;
— The anti-titration formula of the first method "Direct Titration" is included;
— The calculated significant digits are defined.
The Standard was proposed by and shall be administered by Ministry of Health of the
People’s Republic of China.
Drafting organizations of this Standard. National Institute for Nutrition and Food Safety of
Chinese Center for Disease Control and Prevention, and Beijing Center for Diseases
Prevention and Control.
The main drafters of this Standard are. Yang Dajin, Chang Di, Zhao Xin, Wu Guohua, and
Xue Ying.
The previous versions of the standard replaced by this standard are as follows.
— GB/T 5009.7-1985 and GB/T 5009.7-2003.
Determination of reducing sugar in foods
1 Scope
This Standard specifies the determination method of reducing sugar content in food.
This standard applies to the determination of reducing sugar content in food.
When 5.0g of sample is taken, the detection limit of direct titration is 0.25g/100g, and the
detection limit of permanganate titration is 0.5g/100g.
The First method - Direct titration
2 Principle
After the sample’s protein is removed, under the condition of heating, TAKE the
methylene blue as the indicator. TITRATE the marked alkaline copper tartrate solution
(marked by reducing sugar standard solution). Calculate the reducing sugar content
according to the consumed volume of the sample solution.
3 Reagents
Unless otherwise specified, reagents applied in this method are all analytical reagents.
3.1 Hydrochloric acid (HCl).
3.2 Copper sulfate (CuSO 4•5H2O).
3.3 Methylene blue (C16H18C1N3S·3H2O). Indicator.
3.4 Sodium potassium tartrate [C4H4O5KNa·4H2O].
3.5 Sodium hydroxide (NaOH).
3.6 Zinc acetate [Zn(CH3COO)2•2H2O].
3.7 Glacial acetic acid (C2H4O2).
3.8 Potassium ferrocyanide [K4Fe(CN)6•3H2O].
3.9 Dextrose (C6H12O6).
3.10 Fructose (C6H12O6).
water to dissolve it. Put it into a triangular flask with plug. Then add 5mL of hydrochloric
acid (1+1). Heat it for 15min in water at 68°C-70°C. And then place it till the temperature
turning to the indoor temperature. After that, transfer the solution into a 1000mL volumetric
flask and dilute to 1000mL. Per milliliter of this standard solution equal to 1.0mg of
inverted sugar.
4 Instruments
4.1 Acid burette. 25mL;
4.2 Adjustable electric furnace. equipped with asbestos board.
5 Analytical procedure
5.1 Sample processing
5.1.1 General food. Take about 2.5g-5g of smashed solid sample or 5g-25g blended
fluid sample, with the measurement accurate to 0.001g. Put it into a 250mL volumetric
flask, add 50mL of water. Slowly inject 5mL of zinc acetate solution and 5mL of Potassium
ferrocyanide solution. Then raise the solution level with water to the scale. Blend the
solution. Place it for 30min. Filter it with dry filter paper. Dispose the primary filtrate. Take
out the subsequent filtrate for standby.
5.1.2 Stimulant. Take about 100g of blended sample, accurate to 0.01g. Put it into an
evaporating dish. Neutralize it with sodium hydroxide (40g/L) solution to neutral state.
Evaporate it to 1/4 of its initial volume by bathing it in the water. Transfer it to a 250mL
volumetric flask. Manipulate the following procedure according to the regulations of 5.1.1
from "slowly inject 5mL of zinc acetate solution".
5.1.3 Foods containing large quantity of starch. Take about 10g-20g of smashed or
blended sample, with the measurement accurate to 0.001g. Put it into a 250mL volumetric
flask. Add 200mL of water. Heat it for 1h in a 45°C water bath, shaking it frequently. After
cooled, add water to the scale. Blend it. Place it and precipitate it. Absorb 200mL of
supernate and put it into another 250mL volumetric flask. Manipulate the following
too high, it shall dilute appropriately before starting the formal determination. Ensure that
the volume of the consumed sample solution each time is similar to that of the consumed
reducing sugar standard solution used for the determination of the alkaline copper tartrate
solution, which is about 10mL. The result is calculated according to formula (1). When the
concentration is too low, add 10mL of sample solution rather than 10mL of water. Add
reducing sugar standard solution to the end. Record the difference between the
consumed volume AND the volume of the reducing sugar standard solution consumed for
determination, with such difference is equivalent to the reducing sugar content in 10mL
sample solution. Calculate the result according to formula (2).
5.4 Determination of the sample solution
Absorb 5.0mL of alkaline copper tartrate A solution and 5.0mL of alkaline copper tartrate B
solution. Put them into one 150mL conical flask. Add 10mL of water and two glass balls.
Then use burette to drop sample solution which is 1mL less than the forecasted volume to
the conical flask. Ensure it get boiling within 2min. Keep the boiling and drop solution at a
speed of 1 drop/2s to the moment of the disappearance of the blue color. Record the total
consumed volume. Operate 3 such solutions simultaneously and in parallel. Obtain the
average consumed volume.
6 Result calculation
The reducing sugar content in the sample (calculating a certain kind of reducing sugar)
shall be determined according to formula (1).
Where.
X — The reducing sugar content in the sample (calculating a certain kind of reducing
sugar), g/100g;
m1 — The alkaline copper tartrate solution (A solution and B solution each half) which is
equal to the mass of a certain kind of reducing sugar, mg;
8.1 Copper sulfate (CuSO4 • 5H2O).
8.2 Sodium hydroxide (NaOH).
8.3 Sodium potassium tartrate (C4H4O6KNa • 4H2O).
8.4 Ferric sulfate [Fe2(SO4)3].
8.5 Hydrochloric acid (HC1).
8.6 Alkaline copper tartrate A solution. Take 34.639g of copper sulfate (CuSO4·5H2O).
Add some water to dissolve it. Then add 0.5mL of sulfuric acid. Dilute it with water to
500mL. And filtrate it with refined asbestos.
8.7 Alkaline copper tartrate B solution. Take 173g of potassium sodium tartrate, 50g of
sodium hydroxide. Add a moderate amount of water to dissolve it. And dilute it to 500mL.
Filtrate it with refined asbestos. And store the solution in a glass bottle with rubber plug.
8.8 Sodium hydroxide solution (40g/L). Take 4g of sodium hydroxide. Add water to
dissolve and dilute it to 100mL.
8.9 Ferric sulfate solution (50g/L). Take 50g of ferric sulfate. Add 200mL of water to
dissolve it. Slowly add 100mL sulfuric acid into it. And dilute it to 1000mL after co...