This standard applies to the determination of lipase activity in commercial grains. GB/T 5523-1985 Grain and oilseed inspection - Determination of lipase activity GB/T5523-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Inspection of grain and oilseedsMethods for determination of lipaseactivityThis standard applies to the determination of lipase activity in commercial grains. Apparatus and equipment
1.1 Flask: 100ml,
1.2 Pipette: 5ml,
1.3 Separating funnel: 500ml,
1.4 Low temperature oven,
1.5 Mortar, fine-mouthed bottle, etc.
2 Reagents
2.11% thymephthalein ethanol solution,
2.20.2N sodium hydroxide ethanol solution.
2.3 Ethanol and ether (4:1) mixture. UDC (633.1+633.85)
.001.4
GB5523—85
2.4 Toluene.
2.5 pH 4.7 buffer solution: Measure 250 ml of 1N acetic acid solution and 25 ml of 1N ammonium acetate solution, mix them, and add water to 1000 ml. 2.6 Pure oil: Measure about 250 g of sunflower oil (or replace it with pure peanut oil) and inject it into a separatory funnel. Add 100-150 ml of 2% alkali solution, shake it, let it stand and separate the layers, and discard the alkali solution. Wash the oil with water until it is neutral. After standing, pass the oil through a calcium chloride column and dry it for later use. 3
Operation method
Weigh 2g of the sample (shelled oilseeds are called kernels) and pour it into a mortar, add 1ml of pure oil, mix, add 5ml of buffer, grind into a thin paste, transfer to a conical flask, and wash the mortar with 5ml of water. Add 3 drops of toluene to the conical flask, cover the bottle mouth with weighing blood, and place it in a 30℃ oven for 24h. Take it out, add 50ml of ethanol and ether mixture, let it stand for 5min, add 0.5ml of thymephthalein indicator, and drip 0.2N alkali ethanol solution to the end point (light blue), and record the milliliters of alkali solution used (V). Weigh another 2g of sample for a control test. Except for not keeping warm at 30℃, the rest of the operation is the same as above, and record the milliliters of alkali solution used (V.). 4 Calculation of results
The activity of lipase is calculated by the following formula: Lipase activity (ml alkali solution/1g sample) Formula: V, —-volume of alkali-free solution for sample titration, ml, V2
-volume of macro alkali solution for control test, ml, N——-actual alkali solution concentration, N,
W——-weight of sample, g, bZxz.net
Published by National Bureau of Standards on November 2, 1985
(Vr-V)N×1000
W(100-M)
Implemented on July 1, 1986
M~-water content of sample, %.
GB5523—85
The allowable difference between two test results shall not exceed 10% of the average value, and the average value shall be taken as the test result. The test result shall be rounded to the first decimal place. Additional remarks:
This standard is 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 Mu Guifen.
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