GB 5413.18-2010 English PDF (GB5413.18-2010)

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GB 5413.18-2010: National food safety standard -- Determination of vitamin C in foods for infants and young children, milk and milk products
GB 5413.18-2010
GB
NATIONAL STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
National food safety standard
Determination of vitamin C in foods for infants and
young children, milk and milk products
ISSUED ON. MARCH 26, 2010
IMPLEMENTED ON. JUNE 1, 2010
Issued by. Ministry of Health of PRC
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Principle... 4 
4 Reagents and materials ... 4 
5 Apparatus ... 5 
6 Analysis procedures ... 6 
7 Result representation ... 7 
8 Precision... 8 
9 Other ... 8 
Foreword
This Standard replaces GB/T 5413.18-1997 "Milk powder and formula foods for
infants and young children - Determination of vitamin C content".
Compared with GB/T 5413.18-1997, the main changes of this Standard are as
follows.
- defined the activity unit of enzyme;
- changed the concentration of o-phenylenediamine solution;
- changed the treatment of specimens containing starch;
- added -- the reaction time after adding boric acid-sodium acetate solution;
- added -- the reaction time after adding o-phenylenediamine solution;
This Standard replaces the following previous standards.
- GB 5413-1985, GB/T 5413.18-1997.
National food safety standard
Determination of vitamin C in foods for infants and
young children, milk and milk products
1 Scope
This Standard specifies the determination method of vitamin C in foods for
infants and young children, milk and milk products.
This standard is applicable to the determination of vitamin C in foods for infants
and young children, milk and milk products. The determination result of this
Standard indicates the total content of reduction-type vitamin C and oxidation-
type vitamin C.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
3 Principle
Vitamin C (ascorbic acid) is oxidized to be dehydroascorbic acid in the presence
of activated carbon. The dehydroascorbic acid reacts with o-phenylenediamine
to generate fluorescent substances. Use fluorescent spectrophotometer to
determine its fluorescence intensity. Its fluorescence intensity is proportional to
the concentration of ascorbic acid. Use the external standard method to quantify.
4 Reagents and materials
Unless otherwise specified, the reagents used in the method are analytically
pure; the water used is Grade 3 water regulated in GB/T 6682.
4.1 Amylase. enzyme activity is 1.5U/mg; adjust the dosage in accordance
with the activity unit size.
4.2 Metaphosphoric acid-acetic acid solution A. weigh 15 g of metaphosphoric
6 Analysis procedures
6.1 Specimen Treatment
6.1.1 Starch-containing specimen. WEIGH about 5 g (accurate to 0.0001 g)
of well mixed or about 20 g (accurate to 0.0001 g) of liquid specimen
(containing about 2 mg of Vitamin C) in a 150 mL erlenmeyer flask. ADD 0.1 g
of amylase (4.1). ADD 50 mL of 45°C ~ 50°C distilled water into solid specimen.
ADD 30 mL of 45°C ~ 50°C distilled water into liquid specimen. After well mixing,
USE nitrogen to discharge the air in the flask. COVER it with cork. PLACE it in
the 45°C±1°C incubator (5.4) for 30 min. TAKE it OUT to cool to room
temperature. USE metaphosphoric acid-acetic acid solution B (4.3) to the 100
mL flask for constant volume.
6.1.2 Starch-free specimen. WEIGH about 5 g of well mixed solid specimen
(accurate to 0.0001 g). USE metaphosphoric acid-acetic acid A (4.2) to dissolve.
MAKE constant volume to 100 mL. OR WEIGH about 50 g of well mixed liquid
specimen (accurate to 0.0001 g). USE metaphosphoric acid-acetic acid B (4.3)
to dissolve. MAKE constant volume to 100 mL.
6.2 Preparation of solution for test
6.2.1 TRANSFER the aforementioned specimens (6.1.1, 6.1.2) and Vitamin
C standard solution (4.8) to a 250 mL erlenmeyer flask having about 2 g of
acidic activated carbon (4.4). Severely VIBRATE it. FILTER it (discard about 5
mL of initial filtration) and it shall be the filtration of specimen and standard
solution. Accurately PIPETTE 5.0 mL of the filtration of specimen and standard
solution. Respectively PLACE in the 25 mL and 50 mL flasks having 5.0 mL of
boric acid-sodium acetate solution (4.6). Place for 30 min. USE distilled water
for constant volume. Use it as the blank solution of specimen and standard
solution.
6.2.2 Within this 30 min, accurately PIPETTE 5.0 mL of the filtration of
specimen and standard solution into another 25 mL and 50 mL flasks having
5.0 mL sodium acetate solution (4.5) and about 15 mL of water. USE water to
dilute it to scale. Use it as specimen solution and standard solution.
6.2.3 Specimen for test. Respectively and accurately PIPETTE 2.0 mL of
specimen solution (6.2.2) and specimen’s blank solution (6.2.1) into 10.00 mL
test tubes. Accurately ADD 5.0 mL of o-phenylenediamine solution (4.7) into
each test tube. Well MIX. PLACE for 60 min under dark conditions for test.
6.2.4 Standard series of test solution. Respectively PIPETTE 0.5 mL, 1.0 mL,
1.5 mL and 2.0 mL of the aforementioned solution (6.2.2). Respectively PLACE
them into 10 mL test tubes. ADD water to 2.0 mL. At the same time, accurately
PIPETTE 2.0 mL of blank solution of standard solution (6.2.1) into a 10 mL test