This standard specifies the principle of the method for determining the fatty acid value of rice and brown rice by extraction with anhydrous ethanol, the instruments, reagents, operating steps and result calculation. This standard is applicable to the determination of fatty acid value in rice and brown rice. GB/T 15684-1995 Method for determination of fatty acid value of cereal products GB/T15684-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Method for determination of fatty acid value of cereal products
Method for determination of fatty acid value of cereal products This standard adopts the international standard ISO7305:1986 "Cereal milling products 1 Subject content and scope of application
GB/T 15684-1995
-Determination of fatty acids".
This standard specifies the method principle, instruments, reagents, operation steps and result calculation for the determination of fatty acid value of rice and brown rice by extraction with anhydrous ethanol.
This standard is applicable to the determination of fatty acid value in rice and brown rice. 2 Reference standards
Method for determination of moisture content in grain and oilseeds
GB5497
3 Principle of the method
Extract fatty acids from cereal products with anhydrous ethanol at room temperature and titrate with standard potassium hydroxide solution. 4 Instruments
4.1 Conical flask with stopper: 150mL, 200mL. 4.2 Pipette: 50mL.
4.3 Colorimetric tube: 25mL.
4.4 Microburette: 5mL, minimum scale is 0.02mL. 4.5 Balance: sensitivity is 0.01g.
4.6 Oscillator.
4.7 Sample crusher.
4.8 Glass short-necked funnel.
4.9 Surface blood.
4.10 Qualitative filter paper: medium speed.
5 Reagents
5.1 Anhydrous ethanol: AR.
5.21% phenol-ethanol solution: 1.0g phenolic acid is dissolved in 100mL 95% (V/V) ethanol. 5.3 0.01 mol/L potassium hydroxide-95% ethanol solution: first prepare about 0.5 mol/L potassium hydroxide aqueous solution, that is, weigh about 28g potassium hydroxide and dissolve it in 100mL water, then take 20mL 0.05 mol/L potassium hydroxide aqueous solution and dilute it to 1000mL with 95% (V/V) ethanol. 5.4 Standardization of 0.01 mol/L potassium hydroxide-ethanol solution: Accurately weigh 0.05 g (accurate to 0.0001 g) of potassium hydrogen phthalate that has been dried at 105℃ for 2 h and cooled into a 150 mL conical flask, add 50 mL of carbon dioxide-free distilled water to dissolve, add 3 to 5 drops of 1% phenolic acid indicator, and titrate with the prepared potassium hydroxide-ethanol solution of unknown concentration until it turns slightly red. The end point is that the color does not fade after 30 seconds. Record the milliliters of potassium hydroxide used (V). At the same time, perform a blank test (without adding potassium hydrogen phthalate, operate the same as above), and record the milliliters of potassium hydroxide used (V). Calculate according to formula (1):
c(KOH) = (vV× 204. 23 × 1 00 Where: c(KOH)--the molar concentration of potassium hydroxide-ethanol solution, mol/L, W--the mass of potassium hydrogen phthalate weighed, g; V,--the volume of potassium hydroxide solution used for titration, mL; V.--the volume of potassium hydroxide solution used for blank test, mL; 204.23---the molar mass of potassium hydrogen phthalate, g/mol; 1000--the conversion factor.
6 Operation steps
· (1)
6.1 Sample preparation: Take a uniformly mixed The sample is about 80g, which is crushed with a grinder. The fineness requirement is 95% passing through a CQ16 sieve. After the ground sample is fully mixed, it is placed in a ground-mouth bottle for later use.
Note: The fatty acid content of the crushed sample will gradually increase at room temperature. Therefore, the sample should be measured as soon as possible after grinding, preferably within 1 day. If it cannot be measured in time, it should be stored in a refrigerator (4℃).
6.2 Extraction: Weigh 10±0.01g of the sample in a 150mL ground-mouth corrugated flask, and add 50.0mL of anhydrous ethanol with a pipette. Place On the oscillator, shake for 10 minutes.
6.3 Filtration: After shaking, let it stand for a few minutes, and filter it in a glass funnel with folded filter paper. Discard the first few drops of filtrate, collect more than 25mL of filtrate in a 25mL colorimetric tube, and immediately adjust it to 25mL accurately. 6.4: Titration: Transfer the 25mL filtrate in the colorimetric tube into a conical flask, and wash the colorimetric tube three times with 50mL of carbon dioxide-free distilled water (add distilled water to make the alcohol-soluble enzyme protein in the extract produce a milky white colloid when it meets water to eliminate the extract. Effect of alcohol-soluble enzyme protein on fatty acid titration), pour the washed solution into a conical flask, add a few drops of phenolic acid indicator and titrate with potassium hydroxide-ethanol solution until it turns slightly red and does not fade for 30 seconds. Record the milliliters of potassium hydroxide-ethanol solution consumed (V). 6.5 Blank test: Take 25mL of anhydrous ethanol and add 50mL of carbon dioxide-free distilled water in a conical flask, add a few drops of 1% phenol indicator, and titrate with potassium hydroxide-ethanol solution until it turns slightly red. Record the milliliters of potassium hydroxide-ethanol solution consumed (V.). 6.6 Number of determinations: The same sample is measured twice. 7 Calculation of results
7.1 The fatty acid value is expressed as the number of milligrams of potassium hydroxide required to neutralize the free fatty acids in 100g of dry matter sample. The fatty acid value is calculated according to formula (2):
Fatty acid value (KOH mg/100 g dry basis) = (V,--V.) × c × 56.1%%x100
Wherein: V,--volume of potassium hydroxide-ethanol solution used for titration of sample, mL; V. ---volume of potassium hydroxide-ethanol solution used for titration of blank, mL; 50--volume of anhydrous ethanol used for extracting sample, mL; 25--volume of filtrate used for titration, mL, (2) bZxz.net
GB/T15684-1995
molar concentration of potassium hydroxide-ethanol solution, mol/L; 56.1--molar mass of potassium hydroxide, g/mol; -mass of sample, g
100--mass of sample converted to 100g, g; W-
moisture percentage of sample, that is, the mass of water per 100g sample, g. The calculation result shall be rounded to one decimal place.
7.2 When the difference between two determination results meets the repeatability requirement, the arithmetic mean shall be the determination result. 7.3 Repeatability
The same analyst shall make two determinations on the same sample simultaneously or successively, and the difference between the results shall not exceed 2mgKOH/100g. Additional remarks:
This standard is proposed by the Science and Technology Department of the Ministry of Domestic Trade of the People's Republic of China. This standard is under the jurisdiction of the State Grain Reserves Administration. This standard was drafted by the Chengdu Grain Storage Science Research Institute of the Ministry of Domestic Trade. The main drafters of this standard are Qi Xianmei, Yang Jianxin and Wang Xingjuan. 482
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