GB 5009.239-2016 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB 5009.239-2016 | English | 85 |
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National food safety standard - Determination of Acidity in Food
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GB 5009.239-2016: National food safety standard - Determination of Acidity in Food---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB5009.239-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard –
Determination of Acidity in Food
Issued on. AUGUST 31, 2016
Implemented on. MARCH 1, 2017
Issued by. National Health and Family Planning Commission of the
People’s Republic of China
Table of Contents
Foreword... 3
1 Application Scope... 4
Method I Phenolphthalein Indicator Method... 4
2 Principle... 4
3 Reagents and Materials... 4
4 Apparatus... 5
5 Analytical Procedure... 6
6 Expression of Analytical Results... 10
7 Accuracy... 13
Method II pH Method... 13
8 Principle... 13
9 Reagents and Materials... 13
10 Apparatus... 14
11 Analytical Procedure... 14
12 Expression of Analytical Results... 15
13 Accuracy... 16
Method III Potentiometric Titrator Method... 16
14 Principle... 16
15 Reagents and Materials... 16
16 Apparatus... 16
17 Analytical Procedure... 16
18 Expression of Analytical Results... 18
19 Accuracy... 19
Foreword
This Standard replaces GB 5413.34-2010, National Food Safety Standard –
Determination of Acidity in Milk and Milk Products, GB/T 22427.9-2008, Starch and
Derived Products – Determination of Acidity and GB/T 5517-2010, Inspection of Grain
and Oils – Determination of Acidity in Grain and Produce.
Compared with GB 5413.34-2010, GB/T 22427.9-2008 and GB/T 5517-2010, the
major changes of this Standard are as follows.
-- it changes the standard name into “National Food Safety Standard –
Determination of Acidity in Food”;
-- it integrates the methods for the determination of acidity in food specified in GB
5413.34-2010, GB/T 22427.9-2008 and GB/T 5517-2010.
National Food Safety Standard –
Determination of Acidity in Food
1 Application Scope
This Standard specifies the methods for the determination of acidity in milk and milk
products, starch and derived products, grain and grain products.
The first method of this Standard applies to the determination of acidity in milk and milk
products, starch and derived products, grain and grain products; the second method
applies to the determination of acidity in milk powder; the third method applies to the
determination of acidity in milk and milk products.
Method I Phenolphthalein Indicator Method
2 Principle
Use phenolphthalein as the indicator after the treatment of specimen; use 0.100 0
mol/L sodium hydroxide standard solution to titrate to neutral; use the volume of
sodium hydroxide consumed to determine the acidity of specimen by calculation.
3 Reagents and Materials
Unless specified otherwise, all reagents used for this method are analytically pure and
the water is of grade 3 as specified in GB/T 6682.
3.1 Reagents
3.1.1 Sodium hydroxide solution (NaOH).
3.1.2 Cobalt sulfate heptahydrate (CoSO4·7H2O).
3.1.7 Trichloromethane (CHCl3).
3.2 Preparation of reagents
3.2.1 Sodium hydroxide solution standard solution (0.100 0 mol/L)
Weigh 0.75 g of working chemical potassium acid phthalate which has been dried to
constant weight in an electric drying oven at 105°C ~ 110°C; add 50 mL of water free
of carbon dioxide to dissolve; add 2 drops of phenolphthalein indicator (10 g/L); use
prepared sodium hydroxide solution to titrate until the solution appears pink; maintain
it for 30 s. Meanwhile, carry out blank test.
3.2.2 Reference solution
Dissolve 3 g of cobalt sulfate heptahydrate in water; add dropwise to 100 mL.
3.2.5 Distilled water free of carbon dioxide
Boil water for 15 min to expel carbon dioxide; cool and confine the water.
4 Apparatus
4.1 Analytical balance. sensitivity 0.001 g.
4.2 Basic burette. capacity 10 mL; minimum scale 0.05 mL.
4.7 Pulverizer. it is capable of pulverizing specimen so that more than 95% of
specimen passes sieve CQ16 [equivalent to pore diameter 0.425 mm (mesh number
40)]; it will not generate heat in the grinding chamber when pulverizing specimen.
4.8 Oscillator. reciprocating type; oscillation frequency 100 /min.
4.9 Intermediate speed qualitative filter paper.
5 Analytical Procedure
5.1 Mild powder
5.1.1 Specimen preparation
Transfer all specimen to a clean, dry container (with a seal lid) which is about 2 times
of the volume of specimen; immediately put on the lid; rotate and oscillate repeatedly
to mix up specimen. During the operation, efforts shall be taken to avoid specimen
from exposure to the air.
5.1.2 Determination
Weigh 4 g of specimen (accurate to 0.01 g) to place into 250 mL conical flask. Use
measuring cylinder to take 96 mL of water of about 20°C (3.2.5) to dissolve specimen
once again; stir before allowing to stand for 20 min.
5.1.3 Blank titration
Use 96 mL of water (3.2.5) to conduct blank test; read the millimetres of sodium
hydroxide standard solution consumed (V0). The volume of sodium hydroxide
consumed by blank shall not be less than 0, or else, distilled water as required shall
be prepared and used once again.
5.2 Milk and milk products
5.2.1 Preparation of reference solution
Add 2.0 mL of reference solution to conical flask containing an equivalent volume of
corresponding solution; rotate it gently to mix up; then obtain standard reference colour.
If several similar products are to be determined, the reference solution can be used for
the whole determination process, but the time shall not be more than 2 h.
5.2.4 Condensed milk
Weigh 10 g (accurate to 0.001 g) of specimen mixed up to place in 250 mL conical
flask; add 60 mL of water newly boiled and cooled to room temperature; mix up; add
2.0 mL of phenolphthalein indicator; use sodium hydroxide standard solution for
titration after mixing up; rotate the flask while adding dropwise until the colour is similar
to that of reference solution and does not fade away within 5 s.
5.2.5 Casein
Weigh 5 g (accurate to 0.001 g) of specimen ground and mixed up to place into conical
flask; add 50 mL of water (3.2.5); store for 4 h ~ 5 h at room temperature (18°C ~ 20°C)
or heat to 45°C in water bath and maintain it at the temperature for 30 min; add another
50 mL of water (3.2.5); filter through dry filter paper after mixing up.
5.2.6 Blank titration
Use an equivalent volume of water (3.2.5) to conduct blank test; read the millimetres
of sodium hydroxide standard solution consumed (V0) (applicable to 5.2.2, 5.2.4 and
5.2.5). Use 30 mL of neutral ethanol-diethyl ether mixture to carry out blank test; read
the millimetres of sodium hydroxide standard solution consumed (V0) (applicable to
5.2.3).
5.3 Starch and derived products
5.3.1 Specimen pretreatment
Specimen shall be mixed up.
5.4 Grain and grain products
5.4.1 Specimen preparation
Take 80 g ~ 100 g of specimen mixed up; use pulverizer to pulverize specimen so that
more than 95% of specimen passes sieve CQ16 [pore diameter 0.425 mm (mesh
number 40)]; mix up all specimen sieved after pulverization; place in ground flask; and
immediately determine specimen prepared.
5.4.3 Blank titration
Use 30 mL of water (3.2.5) to carry out blank test and record the millimetres of sodium
hydroxide standard solution used (V0).
6 Expression of Analytical Results
The acidity of milk powder specimen is expressed in °T and calculated in accordance
with Formula (1).
7 Accuracy
The absolute difference between the results obtained from two independent
determination results under repeatable conditions shall not exceed 10% of the
arithmetic mean value.
8 Principle
The acidity is determined through calculation based on the volume of 0.100 0 mol/L
sodium hydroxide for the neutralization of specimen solution to 8.30.
9 Reagents and Materials
Unless specified otherwise, all reagents used for this method are analytically pure and
the water is of grade 3 as specified in GB/T 6682.
9.1 Sodium hydroxide standard solution. as in 3.2.1.
10 Apparatus
10.1 Analytical balance. sensitivity 0.001 g.
10.2 Basic burette. scale division 0.1 mL, accurate to 0.05 mL; or automatic burette
which can meet the same requirements for use.
10.3 pH meter. equipped with glass electrodes and appropriate reference electrodes.
10.6 Thermostat water bath.
11 Analytical Procedure
11.1 Specimen preparation
Transfer all specimen to a clean, dry container (with a seal lid) which is about 2 times
of the volume of specimen; immediately put on the lid; rotate and oscillate repeatedly
to mix up specimen. During the operation, efforts shall be taken to avoid specimen
from exposure to the air.
11.3 Blank titration
Use 100 mL of water (9.3) to carry out blank test and record the millimetres of sodium
hydroxide standard solution used (V0).
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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