GB 5413.31-2013 PDF EnglishUS$70.00 · In stock · Download in 9 seconds
GB 5413.31-2013: National Food Safety Standard Determination of urease in infant foods and dairy products Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB 5413.31: Historical versions
Similar standardsGB 5413.31-2013: National Food Safety Standard Determination of urease in infant foods and dairy products---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB5413.31-2013 GB NATIONAL STANDARD National standard on food safety Infant food and dairy products – Determination of urease Issued on. NOVEMBER 29, 2013 Implemented on. JUNE 01, 2014 Issued by. National Family Planning Commission Table of ContentsForeword... 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... 7ForewordThis 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 urease1 ScopeThis 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 PrinciplesUnder 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 materialsNote. 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 equipment4.1 Electronic balance. sensitivity of 0.01 g. 4.2 Vortex oscillator.5 Analysis stepsTake 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 resultsThe analysis results are to be judged based on Table 1.7 Detection limitThe method is a qualitative method, AND the detection limit is 0.7U. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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