GB 5413.31-2013National Food Safety Standard Determination of urease in infant foods and dairy products (English PDF)
婴幼儿食品和乳品中脲酶的测定
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Issued by
National Family Planning Commission
Level / Type
National · Mandatory
Issue date
November 29, 2013
Implementation date
June 1, 2014
Scope
GB 5413.31-2013 is the English-translated version of 婴幼儿食品和乳品中脲酶的测定.
GB 5413.31-2013 — This standard specifies the determination methods for urease in infant foods and dairy products. This standard applies to qualitative detection of urease in infant food and dairy urease.
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Document preview — GB 5413.31-2013
National Standard of the People's Republic of China
Issued by: National Family Planning Commission
Contents
- Foreword...3
- 1 Scope...4
- 2 Principles...4
- 3 Reagents and materials...4
- 4 Instruments and equipment...6
- 5 Analysis steps...6
- 6 Presentation of analysis results...6
- 7 Detection limit...7
Foreword
This standard replaces GB/T 5413.31-1997 Milk powder and formula foods for
infant and young children - Qualitative detection of urease.
As compared with GB/T 5413.31-1997, the main changes of this standard are
as follows.
- MODIFY the standard name;
- ADD the storage conditions for urea solution;
- ADD the storage conditions for Nessler's reagent;
- ADD the time limit for determination results.
National standard on food safety
Food and dairy products for infant and young children
- Determination of urease
1 Scope
This standard specifies the determination methods for urease in infant foods
and dairy products.
This standard applies to qualitative detection of urease in infant food and dairy
urease.
2 Principles
Under the appropriate pH and temperature conditions, urease will catalyze the
urea to convert into ammonium carbonate. Ammonium carbonate will, under
the alkaline conditions, generate ammonium hydroxide, which will react with the
potassium iodide double salt in the Nessler's reagent to produce brown double-
mercury ammonium iodide.
3 Reagents and materials
Note. Unless otherwise stated, the reagents used in this standard are of
analytical pure AND the water is grade III water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Urea (H2NCONH2).
3.1.6 Potassium dihydrogen phosphate (KH2PO4).
3.1.7 Mercury Iodide (HgI2).
3.1.8 Potassium Iodide (KI).
3.1.9 Sodium hydroxide (NaOH).
3.2 Reagent preparation
3.2.1 Urea solution (10 g/L). WEIGH 5 g of urea and DISSOLVE it in 500 mL
water. STORE it in a brown reagent bottle; PRESERVE it in the refrigerator,
AND the valid period is 1 month.
3.2.2 Sodium tungstate solution (100 g/L). WEIGH 50 g of sodium tungstate
and DISSOLVE it in 500 mL water.
3.2.5 Disodium hydrogen phosphate solution. WEIGH 9.47 g of anhydrous
sodium hydrogen phosphate and DISSOLVE it in 1000 mL water.
3.2.6 Potassium dihydrogen phosphate solution. WEIGH 9.07 g of potassium
dihydrogen phosphate and DISSOLVE it in 1000 mL water.
3.2.9 Nessler's reagent. WEIGH 144 g of sodium hydroxide and DISSOLVE it
in 500 mL water; MAKE it fully dissolved and cooled;
4 Instruments and equipment
4.1 Electronic balance. sensitivity of 0.01 g.
4.2 Vortex oscillator.
5 Analysis steps
Take two test tubes A and two test tubes B; WEIGH 0.10 g of sample
respectively and PLACE into the two tubes; ADD 1 mL of water; SHAKE for 0.5
min (about 100 times). Respectively ADD 1 mL of neutral buffer solution. ADD
1 mL of urea solution into the test tube A (sample tube) AND 1 mL of water into
the test tube B (blank control tube). After shaking uniformly, PLACE them in
40 °C ± 1 °C water bath for 20 min. TAKE the two tubes form the water bath;
6 Presentation of analysis results
The analysis results are to be judged based on Table 1.
7 Detection limit
The method is a qualitative method, AND the detection limit is 0.7U.
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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 7 pages — is available in the English PDF.
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