This standard supersedes "Determination of Relative Density of Foods" (GB/T 5009.2-2003), "National Food Safety Standard - Determination of Specific Gravity in Raw Milk" (GB 5413.33-2010) and "Determination of Fruit Juice - Determination of Relative Density" (NY 82.5-1988).
Compared with GB/T 5009.2-2003 and GB 5413.33-2010, the main changes in this standard are as follows:
- The standard name is changed to "National Food Safety Standard - Determination of Relative Density of Foods";
- The examination methods for relative density of foods, raw milk and fruit juice are integrated in a uniform standard, in which, 3 methods are included and the methods in NY 82.5-1988 are integrated.
National Food Safety Standard
Determination of Relative Density of Foods
食品安全國(guó)家標(biāo)準(zhǔn)
食品相對(duì)密度的測(cè)定
1 Scope
This standard specifies the determination method of relative density of liquid specimen.
This standard is applicable to the determination of relative density of liquid specimen.
Method I: Density Bottle Method
2 Principle
At 20℃, respectively determine the mass of water and specimen filling up the same density bottle; the volume of density bottle (i.e. the volume of specimen) may be determined according to the mass of water, and then the density of specimen may be calculated according to its mass and volume; the ratio of specimen density to water density is the relative density of specimen.
3 Instruments and Apparatus
3.1 Density bottle: precise density bottle, as shown in Figure 1.
Notes:
1 - density bottle;
2 - mark line on branch tube;
3 - small cap on branch tube;
4 - bottle cap of attached thermometer.
Figure 1 Density Bottle
3.2 Thermostat water bath.
3.3 Analytical balance.
4 Analysis Steps
Take a clean, dry, constant-weight and accurately weighed density bottle, fill it up with specimen, and then soak it in 20℃ water bath for 0.5h to make its content reach 20℃; cover the bottle cap, absorb the specimen above the branch tube mark line with fine filter paper strip, and then take it out after covering the small cap; wipe up the outer surface of density bottle with filter paper, put this bottle in the balance room for 0.5h, and then weigh it. Pour out the specimen, wash the density bottle and fill it with water, and then repeat the steps "soak it in 20℃ water bath for 0.5h to make its content reach 20℃; cover the bottle cap, absorb the specimen above the branch tube mark line with fine filter paper strip, and then take it out after covering the small cap; wipe up the outer surface of density bottle with filter paper, put this bottle in the balance room for 0.5h, and then weigh it" as mentioned above. The density bottle shall be free from bubbles, and the temperature in balance room shall be constantly maintained at 20℃; otherwise, this method shall not be used.
5 Expression of Analysis Result
The relative density of specimen at 20℃ is calculated according to Formula (1):
(1)
Where,
d - the relative density of specimen at 20℃;
m0 - the mass of density bottle, g;
m1 - the mass of density bottle and water, g;
m2 - the mass of density bottle and liquid specimen, g.
The calculation result is expressed to the significant digits (accurate to 0.001) of the weighing balance precision.
6 Precision
The absolute difference of the results from two independent determinations under repeatability condition shall not exceed 5% of their arithmetic average.
Foreword I
1 Scope
2 Principle
3 Instruments and Apparatus
4 Analysis Steps
5 Expression of Analysis Result
6 Precision
7 Principle
8 Instruments and Apparatus
9 Analysis Steps
10 Expression of Analysis Result
11 Precision
12 Principle
13 Instruments and Apparatus
14 Analysis Steps
15 Precision
