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GB/T 5009.124-2003 English PDF (GBT5009.124-2003)

GB/T 5009.124-2003 English PDF (GBT5009.124-2003)

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GB/T 5009.124-2003: Determination of amino acids in foods

This Standard specifies the method of using the automatic amino acid analyzer to determine the amino acids in foods. This Standard is applicable to the determination of 16 kinds of amino acids in foods, such as aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, arginine, and etc. The minimum detection limit is 10 pmol.
GB/T 5009.124-2003
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 67.040
C 53
Replacing GB/T 14965-1994
Determination of Amino Acids in Foods
ISSUED ON. AUGUST 11, 2003
IMPLEMENTED ON. JANUARY 1, 2004
Issued by. Ministry of Health of the PRC;
Standardization Administration of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Reagents ... 4
4 Apparatus ... 5
5 Specimen Treatment ... 6
6 Analytical Procedures ... 6
7 Determination ... 6
8 Result Calculation ... 7
9 Precision ... 7
10 Standard Map ... 8
Foreword
This Standard replaces GB/T 14965-1994 Method for Determination of Amino Acids in Foods.
Compared with GB/T 14965-1994, this Standard mainly has the following changes. --- Modify the Chinese name of the standard, which was changed into Determination of Amino Acids in Foods.
--- Modify the structure of the original standard as per GB/T 20001.4-2001 Rules for Drafting Standards - Part 4. Methods of Chemical Analysis.
This Standard was proposed by and shall be under the jurisdiction of the Ministry of Health of the PRC.
Drafting organizations of this Standard. Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine.
Chief drafting staffs of this Standard. Jia Jianbin, and Zhao Xihe.
The original standard was initially published in 1994; and this is the first-time amendment.
Determination of Amino Acids in Foods
1 Scope
This Standard specifies the method of using the automatic amino acid analyzer to determine the amino acids in foods.
This Standard is applicable to the determination of 16 kinds of amino acids in foods, such as aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, arginine, and etc.. The minimum detection limit is 10 pmol.
This Standard is not applicable to the determination of amino acids in low-protein- content fruits, vegetables, beverages, and starchy foods.
2 Principle
Protein in food is decomposed by hydrochloric acid water into the free amino acids; after being separated by ion exchange column of amino acid analyzer, it occurs color reaction with ninhydrin solution; then the amino acid content is determined by spectrophotometer colorimetric method.
3 Reagents
3.1 Concentrated hydrochloric acid. guaranteed reagent.
3.2 6 mol/L hydrochloric acid. concentrated hydrochloric acid is mixed with water by 1+1.
3.3 Phenol. requires re-distillation.
3.4 (0.0025 mol/L) mixed amino acid standard solution (sold by apparatus manufacturer).
3.5 Buffer solution
3.5.1 Sodium citrate buffer solution with pH2.2. weigh 19.6g of sodium citrate (Na3C6H5O7?€?2H2O) and 16.5 mL of concentrated hydrochloric acid; add water and dilute to 1000 mL; adjust the pH to be 2.2 by concentrated hydrochloric acid or 500 g/L 5 Specimen Treatment
After the specimen collection, use the homogenizer to make it homogenate (or try to crush the specimen); freeze and preserve in the low-temperature refrigerator; thaw the specimen before analyzing.
6 Analytical Procedures
6.1 Weighing specimen
Accurately weigh certain amount of specimen with good uniformity, for instance milk powder, and etc.; accurate to 0.0001g, (specimen protein content shall be within the range of 10mg~20mg); for the specimen with poor uniformity, for instance the fresh meat, and etc.; in order to reduce the error, the specimen weighing amount can be increased, dilute the specimen before measurement. Place the weighed specimen into the hydrolysis tube.
6.2 Hydrolysis
Add 10 mL ~ 15 mL of 6 mol/L hydrolysis acid (the amount depends on the protein content of the specimen) into the hydrolysis tube; the specimen with high water content (for instance, milk) can be added with equivalent volume of concentrated hydrochloric acid; add 3~4 drops of freshly distilled phenol; place the hydrolysis tube into the refrigerant to freeze for 3 min ~5 min; then connect to the suction pipe of the vacuum pump, pump vacuum (close to 0 Pa); inject the high-purity nitrogen, then pump vacuum again and inject nitrogen; after repeating for three times, seal the hydrolysis tube under the nitrogen injecting state, or tighten the screw cap, and place the sealed hydrolysis tube within the 110??C??1??C constant temperature drying oven, hydrolyze for 22h, take out for cooling.
Open the hydrolysis tube, after filtering the hydrolysate, rinse the hydrolysis tube with deionized water for several times; transfer all hydrolysate into 50 mL volumetric flask, and use deionized water to make volume. Take 1 mL of filtrate into 5 mL volumetric flask; use vacuum dryer to dry at 40??C~50??C; the residue is dissolved by 1 mL ~ 2 mL of water, then dry again; repeat for twice; finally evaporate to dryness; dissolve by 1 mL of buffer solution with pH2.2; then prepare for the apparatus determination. 7 Determination
Accurately take 0.200 mL of mixed amino acid standard solution; dilute it to 5 mL by buffer solution with pH2.2; the concentration of such standard diluent is 5.00 nmol/50 ??L; which is used for amino acid standard of on-machine determination; use the standard method beyond the automatic amino acid analyzer to determine the content

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