GB 5009.2-2024National food safety standard - Determination of relative density of food (English PDF)

Foreword

This standard replaces GB 5009.2-2016 National food safety standard - Determination

of relative density of food.

Compared with GB 5009.2-2016, the main changes in this standard are as follows.

-- A calculation formula is added in Method C;

-- Method D, oscillating U-tube digital densimeter method, is added.

National food safety standard - Determination of relative

density of food

1 Scope

This standard specifies the method for the determination of the relative density of liquid

foods.

This standard is applicable to the determination of the relative density of liquid foods.

Method A - Density bottle method

2 Principle

The masses of water and the sample filled in the same density bottle at 20 °C are

measured, respectively. The volume of the density bottle, which is the sample volume,

can be determined from the mass of the water. The density of the sample can be

calculated based on the mass and volume of the sample. The ratio of sample density to

water density is the relative density of the sample.

3 Instruments and equipment

4 Analysis steps

Take a clean, dry, constant weight, and accurately weighed density bottle. After filling

it with the sample, place it in a water bath and soak it for 0.5 hours until the temperature

of the sample inside reaches (20+/-1) °C;

5 Expression of analysis results

The relative density of the sample is calculated according to formula (1).

6 Precision

The absolute difference between two independent determination results obtained under

repeatability conditions shall not exceed 5% of the arithmetic mean.

7 Principle

At 20°C, the buoyancy of the glass hammer in water and in the sample are measured,

respectively.

8 Instruments and equipment

9 Analysis steps

When measuring, place the stand on a flat table, place the beam on the knife edge, hang

a weight on the hook, adjust the lifting knob to the appropriate height, and rotate the

zero-setting knob to make the two pointers match. Then remove the weight, hang up

the glass hammer, add water to the 4/5 position in the glass cylinder, and put it into a

constant temperature water bath; make the water temperature in the glass cylinder

balance and stabilize at (20+/-1) degrees C, let the glass hammer sink to the glass cylinder, try

placing four kinds of riders until the two pointers on the beam coincide, and the reading

at this time is P1;

10 Expression of analysis results

The relative density of the sample is calculated according to formula (2).

11 Precision

The absolute difference between two independent determination results obtained under

repeatability conditions shall not exceed 5% of the arithmetic mean.

12 Principle

Archimedes' principle is used; the liquid sample to be tested is poured into a higher

container, and then the hydrometer is placed into the liquid sample after the temperature

stabilizes at 20 °C.

13 Instruments and equipment

14 Analysis steps

Wash and dry the hydrometer, and slowly place it into a suitable measuring cylinder

containing an appropriate amount of liquid sample to be tested, and the cylinder has

been at (20+/-1) °C in a constant temperature water bath. Do not let the hydrometer touch

the wall and bottom of the container.

15 Expression of analysis results

The relative density of the sample is calculated according to formula (3).

16 Precision

The absolute difference between two independent measurement results obtained under

repeatability conditions shall not exceed 5% of the arithmetic mean.

17 Principle

Electromagnetic induces the oscillation of the glass U-tube, the magnitude of the

oscillation frequency squared is linearly related to the density of the sample in the

measuring cell, and the density of the sample is thus determined.

18 Instruments and equipment

19 Analysis steps

20 Presentation of analysis results

The result is expressed to the third decimal place.

21 Precision

The absolute difference between two independent measurement results obtained under

repeatability conditions shall not exceed 5% of the arithmetic mean.

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