Juice of fruits and vegetables-Determination of free amino acid

This standard specifies the extraction, purification and determination methods of free amino acids in fruit and vegetable juices. GB/T 12292-1990 Determination of free amino acids in fruit and vegetable juices GB/T12292-1990 Standard download decompression password: www.bzxz.net
This standard specifies the extraction, purification and determination methods of free amino acids in fruit and vegetable juices.

National Standard of the People's Republic of China
Determination of free amino acid in fruit and vegetable juicesJuice of fruits and vegetablesDetermination of free amino acidSubject content and scope of applicationbZxz.net
This standard specifies the extraction, purification and determination methods of free amino acids in fruit and vegetable juices. 2
Determination principle
GB/T12292-90
Fruit and vegetable juices are passed through cation exchange resins to fix and purify amino acids. After eluting the amino acids with 2mol/L ammonium hydroxide, deaminate and concentrate. The content is determined using an amino acid analyzer. 3 Instruments and equipment
3.1 Amino acid analyzer or high pressure liquid chromatograph: 3.2 Glass column, 20cm high, 2cm inner diameter;
3.3 Masher;
3.4 ​​Centrifuge;
3.5 Balance;
3.6 Rotary evaporator.
3.7 Vacuum dryer.
4 Reagents
All reagents are analytically pure, and deionized water is used for the preparation of reagents. 4.1 Cation exchange resin, Dowex 50W×4 type, 100-200 mesh or other suitable resins. 4.2 Hydrochloric acid solution 6mol/L.0.1mol/L. 4.3 Ammonium hydroxide solution 2mol/L.
4.4 Sodium hydroxide solution 3.5mol/L.
4.5 Each amino acid standard solution 0.0025M. 4.6 Various buffers for instrumental analysis.
4.7 Triketone reagent for instrumental analysis.
5 Sample selection and preparation
5.1 Liquid products must be fully mixed.
5.2 Solid products Select representative fruits and vegetables, wash, dry, peel or cut the peel, and use the quartering method to sample about 150g.
5.3 Weighing Weigh 100-150g of sample accurately to 0.01g, place it in the glass jar of the masher, and add an equal amount of water. 5.4 Sample pounding Place the glass jar containing the sample on the masher, pound it at the first gear speed for 1min, take it out and pour it into a beaker. 5.5 Filtration and centrifugation Filter the pounded sample liquid, draw 10mL of filtrate into a centrifuge tube, and centrifuge it at a speed of 4000r/min for 15min.
5.6 Pectin removal The sample liquid rich in pectin needs to be treated with ethanol. Accurately draw 5mL of sample liquid, add 34mL of 96% ethanol to filter, rinse the filter paper with 15mL of 80% ethanol three times, and distill the filtrate under reduced pressure at 35℃. 6 Analysis steps
6.1 Fixing column device Put Dowex 50W×4 resin into a glass cylinder, leaving about 10cm from the top, activate the resin with 250mL of 6mol/L hydrochloric acid and then wash with water until there is no chloride ion (check with silver nitrate, no white precipitate is produced). Adjust the piston so that the solution flow rate is 1mL/min. 6.2 Fixation and elution Take 5mL of sample solution or liquid product, except for the sample solution of pectin, take all of it, put it into a glass cylinder and add 5mL of water. After the liquid passes through the resin, add 50mL of 2mol/L ammonium hydroxide, which can be added in 3 to 4 times, wash with 50mL of water,
Collect the solution flowing out of 2mol/L ammonium hydroxide in a round-bottom flask, evaporate to dryness under reduced pressure and heating (40 to 45℃c), and dissolve with 5mL of 0.1mol/L hydrochloric acid. 6.3 Deamination Take 1mL of the test solution, add 2~3 drops of 3.5mol/L sodium hydroxide solution, adjust to pH10~11, and place in a vacuum dryer to evaporate under reduced pressure. Wash with 1mL of water, and then evaporate to dryness under vacuum. Repeat this twice, add 0.5mL of pH2.2 buffer and 0.5mL of 0.1mol/L hydrochloric acid to make the pH reach 2.2, and then dilute 5~10 times before determination. 6.4 Determination Use an amino acid analyzer to determine the amino acid content. Before determination, make 2~3 amino acid standards, and then test the sample after the instrument is stable.
7 Calculation of results
7.1 The results are expressed in mg/kg or mg/L.
7.2 Calculation formula
Content of a certain amino acid (mg/kg) =
Content of a certain amino acid (mg/L) =
X10**(-3)Xd
-X10**(-3)Xd
Where: NG is the mass of a certain amino acid measured by the instrument, Ng:m is the weight of the fresh sample, g;
mL is the original sampling volume, mL;
d is the dilution factor.
7.3 Allowable difference
The relative difference between the results of parallel determination of free amino acids in fruit and vegetable juices shall not exceed 5%. Additional remarks:
This standard was proposed by the Ministry of Agriculture of the People's Republic of China. This standard was drafted by the Analysis and Testing Center of the Chinese Academy of Agricultural Sciences. This standard was drafted by the Analysis Center of the Shanghai Academy of Agricultural Sciences. The main drafters of this standard are Ji Weige, Gu Jinyan and Chen Bifang. This standard adopts NFV76--1151983 "Determination of free amino acids in fruit and vegetable juices". Approved by the State Bureau of Technical Supervision on March 29, 1990 and implemented on December 1, 1990
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