GB 5009.239-2016 PDF in English
GB 5009.239-2016 (GB5009.239-2016) PDF English
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National Food Safety Standard -- Determination of Acidity in Food
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Standards related to (historical): GB 5009.239-2016
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GB 5009.239-2016: PDF in English GB 5009.239-2016
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).
3.1.3 Phenolphthalein.
3.1.4 95% ethanol.
3.1.5 Diethyl ether.
3.1.6 Nitrogen. purity 98%.
4.6 Ground conical flask with a stopper. 250 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.
4.10 Pipette. 10 mL, 20 mL.
4.11 Measuring cylinder. 50 mL, 250 mL.
4.12 Glass funnel and funnel support.
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.
Add 2.0 mL of reference solution to a conical flask containing 96 mL of water of about
20°C (3.2.5); 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.
Add 2.0 mL of phenolphthalein indicator to another conical flask containing specimen
solution; rotate it gently to mix up. Use 25 mL basic burette to add sodium hydroxide
solution to the conical flask; rotate the flask while adding dropwise until the colour is
similar to that of reference solution and does not fade away within 5 s. The whole
titration process shall be finished within 45 s. During the titration process, blow nitrogen
to the conical flask to prevent solution absorbing carbon dioxide from the air. Record
the millimetres of sodium hydroxide solution used (V1), accurate to 0.05 mL, and
substitute into Formula (1) for calculation.
5.1.3 Blank titration
millimetres of sodium hydroxide standard titration solution used (V2), and substitute
into Formula (2) for calculation.
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. Absorb 50 mL of
filtrate to place into conical flask; 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. The whole titration process shall be finished within 45 s. During the titration
process, blow nitrogen to conical flask to prevent solution absorbing carbon dioxide
from the air. Record the millimetres of sodium hydroxide standard titration solution
used (V3), and substitute into Formula (3) for calculation.
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).
The volume of sodium hydroxide consumed by blank shall not be less than 0, or else,
distilled water or neutral ethanol-diethyl ether mixture as required shall be prepared
and used once again.
5.3 Starch and derived products
5.3.1 Specimen pretreatment
Specimen shall be mixed up.
5.3.2 Specimen weighing
Weigh 10 g (accurate to 0.1 g) of specimen to transfer to 250 mL conical flask; add
100 mL of water; vibrate for mixing up.
5.3.3 Titration
Add 2.0 mL of reference solution to a conical flask containing 100 mL of water of about
20°C; 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.
Add 2 ~ 3 drops of phenolphthalein indicator to another conical flask containing
specimen solution; use sodium hydroxide standard solution for titration after mixing up;
m3 – mass of specimen, expressed in g;
0.1 – molar concentration of sodium hydroxide for the theoretical definition of acidity,
expressed in mol/L.
The result is expressed by the arithmetic mean value of the results obtained from two
independent determinations under repeatable conditions, which is rounded off to the
third decimal place.
The acidity of the specimen of starch and derived products is expressed in °T and
calculated in accordance with Formula (4).
where,
X4 – acidity of specimen, expressed in °T [calcula...
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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