This standard refers to the use of the international standard ISO 762-1982 "determination of mineral impurities in fruit and vegetable products."
1 Topic content and scope of application
This standard specifies the method for the determination of mineral impurities in quick-frozen fruits and vegetables.
This standard applies to the determination of mineral impurities in frozen fruits and vegetables.
2 Principle
The organic matter was separated by a flotation method and heavy impurities were separated by a deposition method. The deposit was burned in a high-temperature electric resistance furnace at 600° C., and the resulting residue was weighed.
3 Reagents
The reagents were of analytical grade and the water used was distilled water or water of equivalent purity.
3.1 Sodium chloride: 15% (m/m) solution;
3.2 Silver nitrate: 17 g/L solution.
4 Instruments
4.1 Crusher;
4.2 Ashless filter paper;
4.3 å©åŸš;
4.4 high temperature resistance furnace: 600 ± 10 °C;
4.5 Dryer: with effective desiccant;
4.6 analytical balance;
4.7 Beaker: 2000 mL;
4.8 Funnel.
5 Preparation of samples and crucibles
5.1 Preparation of Samples
Pack the sample below 500g and take the entire package. The sample was thawed in a closed vessel and quantitatively transferred to a 2000 mL beaker. Samples can be crushed if necessary. Samples larger than 500g should be taken from representative samples 500g before thawing.
5.2 Preparation of Thorium
The cleaned crucible was moved into a 600±10°C high-temperature resistance furnace and burned for 1 h. After being cooled to below 200° C., it was taken out, moved into a desiccator, cooled to room temperature, and weighed. Repeat burning until the difference between the previous and the second weighing does not exceed 0.0002g as a constant.
6 Determination
6.1 Separation
Transfer the sample to a 2000 mL beaker, add water to the mark, stir it thoroughly with a glass rod, and let it stand for about 10 minutes. Then pour the upper layer of water into a second 2000 mL beaker, add water to the first and second beakers and mix. Stir and let stand for 10 min. Then pour the water from the second beaker into a third 2000 mL beaker. Pour the upper water from the first beaker into the second beaker. Repeat these operations carefully and pour the third beaker supernatant into the drain until all floating fruit and vegetable organics are discarded. Collect all of the sediment in the first beaker.
A solution of warm sodium chloride (2.1 bars) was added to the sediment to allow organic impurities to float, sediments were precipitated, and the sediments were washed thoroughly with warm water to remove sodium chloride, and silver nitrate (2.2 bars) solution was used to test the washing solution without chlorine. The ions were quantitatively transferred to ashless filter paper.
6.2 Ashing
Transfer the filter paper together with the deposits into the crucible (5.2 bars), charcoalize it on the electric furnace until it is smokeless, move it into a 600±10°C high-temperature resistance furnace and burn it for 1 hour, cool it to below 200°C, remove it, and move it into a desiccator to cool it down. Room temperature, weighing. Repeat burning until the difference between the previous and the second weighing does not exceed 0.0002g as a constant.
7 result representation
M2-m1
X =───×10**6
M0
Where: X - mineral impurity content, mg / kg;
M0--quality of sample, g;
M1--quality of gills, g;
M2--mass of yttrium and mineral impurities, g.
Additional information:
This standard was proposed by the Ministry of Commerce of the People's Republic of China.
This standard is drafted by Beijing Food Research Institute.
Drafter of this standard Li Weidong.
This standard is equivalent to the use of the United Nations Commission on Food Regulations issued CAC54-1974 "determination of frozen fruit and vegetable mineral impurities"