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GB 5009.239-2016 PDF English

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GB 5009.239-2016: 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

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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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