GB/T 8857-1988 Determination of total ash and alkalinity of total ash and water-soluble ash of fruit and vegetable products

This standard is applicable to the determination of total ash and alkalinity of total ash and water-soluble ash of various types of fruit and vegetable products. GB/T 8857-1988 Determination of total ash and alkalinity of total ash and water-soluble ash of fruit and vegetable products GB/T8857-1988 Standard download decompression password: www.bzxz.net

8857-88
National Standard of the People's Republic of China
Method for determination of total ash and of alkalinity of total ash and water-soluble ash in fruit and vegetable productsGB/T
This standard adopts the international standard ISO5520-1981 "Fruits, vegetables and their products-Determination of alkalinity of total ash and water-soluble ash".
1 Scope of application
This standard is applicable to the determination of total ash and alkalinity of total ash and water-soluble ash in various types of fruit and vegetable products. 2 Reference standards
GB5009.4-85 Determination of ash in food 3 Definition
3.1 Total ash: The number of grams of residual ash obtained by burning 100g of sample under the conditions specified in this standard. 3.2 Alkalinity of total ash: The acid required to neutralize 100 g of ash obtained from the sample under the conditions specified in this standard, measured in milligram equivalents.
3.3 Alkalinity of water-soluble ash: The acid required to neutralize the water extract of 100 g of ash obtained from the sample under the conditions specified in this standard, measured in milligram equivalents.
The alkalinity of total ash and water-soluble ash can also be expressed as an alkalinity index. 3.4 Alkalinity index: The number of mL of 1N acid solution required to neutralize 1 g of ash obtained from the sample under the conditions specified in this standard.
4 Principle
4.1 Total ash: Determined by ignition gravimetric method at 525 ± 25°C. 4.2 Alkalinity of total ash: Ash the product at 525 ± 25°C, add excess sulfuric acid standard solution, and then back-titrate with sodium hydroxide standard solution in the presence of an indicator. 4.3 Alkalinity of water-soluble ash: Use hot water to extract ash from the ash-treated product at 525 ± 25°C. Then neutralize the water extract with a standard sulfuric acid solution in the presence of an indicator. 5 Reagents
All reagents are analytical grade and are prepared with distilled water that does not contain carbon dioxide. 5.1 0.1N sulfuric acid standard solution.
5.2 0.1N sodium hydroxide standard solution.
5.3 Indicator
Add 4 ml of 10 g/L methyl blue solution to 100 ml of 1 g/L methyl orange solution. 6 Apparatus
6.1: 30-50 mL quartz crucible or porcelain crucible (disposable). 6.2 Muffle furnace.
7 Operational procedures
7.1 Determination of total ash
7.1.1 Constant weight
Boil the sample in dilute hydrochloric acid (1+4) for 1~2h, wash and place in a muffle furnace at 525±25℃ for 30min. When the furnace temperature drops below 200℃, move the crucible into a desiccator, cool to room temperature and weigh to the nearest 0.0001g, and repeat the burning to constant weight.
7.1.2 Preparation of test sample
Mix the laboratory sample evenly. If the sample is stored in a sealed frozen state, it must be thawed and sampled evenly after the temperature returns to room temperature.
7.1.3 Test part
Weigh 5~10g of fresh sample and 0.5~2g of dry sample, weigh to the nearest 0.001g, or accurately pipette 5~10mL of liquid into a pre-weighed crucible.
7.1.4 Carbonization
Liquid samples must be evaporated to dryness in a boiling water bath. Solid or evaporated samples should be heated with a low fire to fully carbonize the samples until there is no smoke.
7.1.5 Ashing
Put the completely carbonized sample in a muffle furnace and ash it at 525±25℃ until no carbonized material remains. When the furnace temperature drops below 200℃, move the crucible into a desiccator, cool it to room temperature and weigh it, accurate to 0.0001g, and repeat the burning until constant weight.
7.2 Determination of ash alkalinity
7.2.1 Determination of total ash alkalinity
Accurately pipette about 10-15 mL of sulfuric acid standard solution to treat the ash obtained in 7.1.5, quantitatively transfer it into a 200 mL conical flask, rinse with a small amount of hot water, boil the liquid on a hot plate until transparent, then cool to room temperature, add 2 drops of mixed indicator, and titrate with sodium hydroxide standard solution until the solution changes from light purple to orange-yellow. 7.2.2 Alkalinity of water-soluble ash
Add about 20 mL of hot water to the ash obtained in 7.1.5, transfer all of it into a filter paper in a funnel, then wash the residue on the filter paper with a small amount of hot water, merge the washing liquid into the filtrate, and add 2 or 3 drops of mixed indicator after the filtrate cools, and titrate with sulfuric acid standard solution until the solution changes from orange-yellow to light purple. 8 Result Expression
8.1 Calculation Method and Formula
8.1.1 Total ash: expressed as the mass of ash obtained by burning 100g sample: ml
X=—X100....
Wherein: X—total ash, %;
m1—mass of ash obtained after the sample is ashed, g; m
mass of the sample, g.
8.1.2 Alkalinity of total ash
Alkalinity of total ash: expressed as the number of milligram equivalents in 100g sample, calculated as follows: 100
A=(N1V1-N2V2)-
Alkalinity index of total ash: expressed as the number of mL of 1N acid solution per 9 ash, calculated as follows: 1
n= (N1V2 - N2V2)X
Wherein: A——alkalinity of total ash, milliequivalent n—alkalinity index of total ash;
N1—equivalent concentration of sulfuric acid standard solution: V1
volume of sulfuric acid standard solution added in 7.2.1, mL; N2-
equivalent concentration of sodium hydroxide standard solution; volume of sodium hydroxide standard solution added in 7.2.1, ml; mass of sample, g:
mass of ash obtained after sample ashing, g; 8.1.3 Alkalinity of water-soluble ash
Alkalinity of water-soluble ash: expressed as milliequivalent number in 100g sample, calculated as follows: 100
AW=NiV'1X-
Alkalinity index of water-soluble ash: expressed as mL of 1N acid solution per 9 ash, calculated as follows: 1
nw=NiV'iX
-alkalinity of water-soluble ash;
Wherein: Aw
-alkalinity index of water-soluble ash;
N1-equivalent concentration of sulfuric acid standard solution: (5)
-volume of sulfuric acid standard solution added in 7.2.2, mL; V'1-
mass of sample, g:
m'1-mass of ash obtained after sample ashing, g. The result of liquid sample is expressed as the content in 100 mL sample. If the repeatability requirement is met, take the arithmetic mean of the two measurements as the result. The result is rounded to the second decimal place.
8.2 Repeatability
The relative error of the results of two simultaneous or consecutive measurements by the same analyst shall not exceed 5%. The constant weight requirements in this standard are that the difference between the two measurements shall not exceed 0.0005g. Additional remarks:bZxz.net
This standard was proposed by the Bureau of Subsidiary Foodstuffs, Ministry of Commerce of the People's Republic of China. This standard was drafted by the Institute of Food Testing and Inspection, Ministry of Commerce. The main drafter of this standard is Fu Li.
Approved by the Ministry of Commerce of the People's Republic of China on February 29, 1988 and implemented on July 1, 1988
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.