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GB/T 5009.124-2003 (GB/T5009.124-2003)

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GB/T 5009.124-2003: PDF in English (GBT 5009.124-2003)
GB/T 5009.124-2003
ICS 67.040
C 53
Replacing GB/T 14965-1994
Determination of Amino Acids in Foods
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
This Standard replaces GB/T 14965-1994 Method for Determination of Amino Acids in
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
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
3.3 Phenol. requires re-distillation.
3.4 (0.0025 mol/L) mixed amino acid standard solution (sold by apparatus
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
µL; 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
(Above excerpt was released on 2016-11-13, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT5009.124-2003