GB/T 5510-1985 Grain and oilseed inspection - Determination of fatty acid value

This standard is applicable to the determination of fatty acid content in commercial grains. GB/T 5510-1985 Grain and oilseed inspection method for determination of fatty acid content GB/T5510-1985 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Inspection of grain and oilseedsMethods for determination of fatty acid value of floursThis standard applies to the determination of fatty acid value in commercial grains. 1bzxZ.net
Instruments and appliances
1.1 Conical flask with stopper: 150ml;
1.2 Measuring cylinder;
1.3 Pipette:
1.4 Microburette;
1.5 Surface blood;
1.6 Balance: sensitivity 0.01g;
1.7 Electric oscillator;
1.8 Funnel, etc.
2 Reagents
GB/T5510-85
2.1 0.01N potassium hydroxide (or sodium hydroxide) ethanol (95%) solution: first prepare about 0.5N potassium hydroxide aqueous solution, then take 20ml and dilute to 500ml with 95% ethanol;
2.2 Benzene, 95% ethanol;
2.3 0.04% phenol anhydride ethanol solution (0.2g phenolic acid dissolved in 500ml 95% ethanol solution). 3 Operation method
3.1 Sample preparation: Take about 80g of sample from the average sample and crush it so that more than 90% of the sample passes through a 40-mesh sieve. If the crushed sample is placed at room temperature above 20℃, the fatty acid value will increase rapidly, so it must be measured in time. 3.2 Leaching: Weigh 20±0.01g of the sample (10g of the sample when the fatty acid value is higher than 60mgK0H/100g) into a 200ml or 250ml conical flask, add 50ml of benzene, add a stopper and shake for a few seconds, then open the stopper to release the gas, cover the stopper and place it on an oscillator for 30min (or shake it by hand for 45min), take it out, tilt the bottle and let it stand for a few minutes to make the filtrate clear. 3.3 Filtration: Filter with fast filter paper, discard the first few drops of filtrate, collect 25ml of filtrate with a 25ml colorimetric tube or measuring cylinder, and immediately adjust it to the scale accurately.
3.4 ​​Titration: Transfer 25ml of filtrate into a conical flask, then use the original colorimetric tube or measuring cylinder to take 25ml of phenolic ethanol solution and add it to the conical flask, and immediately titrate with potassium hydroxide ethanol solution until it shows a slightly reddish color that does not disappear within half a minute. Record the number of milliliters of potassium hydroxide ethanol solution consumed (V1).
3.5 Blank test: Take 25 ml of phenol ethanol solution and titrate with potassium hydroxide ethanol solution as in 3.4, and record the milliliters of potassium hydroxide ethanol solution consumed (VO).
4 Result calculation
The fatty acid value is expressed as the milligrams of potassium hydroxide required to neutralize the free fatty acids in 100 g of grain sample. The fatty acid value is calculated according to the following formula:
Fatty acid value (mgKOH/100g) = (V1-V0)N×56.1×-25
WIn the formula: V1 is the volume of potassium hydroxide ethanol solution used to titrate the sample, ml; X
W(100-M)
V0 is the volume of potassium hydroxide ethanol solution used to titrate 25ml of phenol ethanol solution, ml; 50 is the volume of benzene used to soak the sample, ml;
25 is the volume of filtrate used for titration, ml; N is the equivalent concentration of potassium hydroxide (or sodium hydroxide) ethanol solution: 56.1——milligram equivalent of potassium hydroxide;
W is the weight of the sample, g;
M is the moisture percentage of the sample, % (when determining the fatty acid value of flour, it is calculated on a wet basis, and it is not necessary to subtract moisture): 100 is converted to 100g sample weight.
The allowable difference between the two test results is no more than 5mgK0H/100g for fatty acid values ​​above 51; no more than 3mgKO0H/100g for fatty acid values ​​below 50. The average is the test result, and the test result is rounded to the first decimal place. Note: When the color of the leaching solution is too dark and the titration end point is difficult to observe, use a four-fold filter paper instead, put about 0.5g of powdered activated carbon in the cone of the filter paper, and slowly inject the leaching solution while filtering while decolorizing. Or use a 0.1% thymol acid ethanol solution indicator, and the titration end point is green or blue-green. Additional notes:
This standard was proposed by the Ministry of Commerce of the People's Republic of China. This standard was drafted by the Grain Storage and Transportation Bureau of the Ministry of Commerce. The main drafters of this standard are Gao Xiuwu, Yang Haoran, Wu Yanxia, ​​and Lv Guifen. Issued by the National Bureau of Standards on November 2, 1985
Implementation on July 1, 1986
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