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AOAC Official Method 997.09 Nitrogen in Beer, Wort, and Brewing Grains Protein (Total) by Calculation Combustion Method First Action 1997.rar,brewing,breweries

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27.1.25A AOAC Official Method 997.09 Nitrogen in Beer, Wort, and Brewing Grains Protein (Total) by Calculation Combustion Method First Action 1997 ASBCAOAC Method (Applicable to beer and wort containing 0.010.15% N and solid brewing grains containing 0.19% N.) See Table 997.09 for the results of the interlaboratory study sup- porting the acceptance of the method. A. Principle Nitrogen is freed by combustion of test portion in pure O. Nitro- gen gas is measured using thermal conductivity detector. Total N is calculated based on response from known N standard. Nitrogen is converted to protein by multiplying by 6.25. B. Apparatus (a) Nitrogen combustion analyzer.With thermal conductivity detector,capableofreducingNOxcompoundstoN.Anyinstrument that offers range of 0.02100 mg N, precision of 0.002 or 0.75% RSD(whicheverisgreater),andreadabilityof0.001%(orbetter)for N determination is suitable. (b) Laboratory mill.With 0.5 mm or smaller screen. (c) Analytical balance.Weighing to nearest 0.1 mg. C. Reagents (a)Nitrogenstandardsolutionforliquid.Lysinehydrochloride reagent (15.33% N). Weigh ca 1 g lysine hydrochloride to nearest 0.1 mg and dissolve in 100 mL weighed amount of H2O. Percent N (by weight) = weight of nitrogen standard (g) 15.33/weight of nitrogen standard (g) + weight of H2O (g) = ca 0.152. (b) Nitrogen standard for solid.Ethylenediamine tetraacetic acid (EDTA) 9.59% N. (c)Checkstandardforsolid.Nicotinicacidp-toluenesulfonate (HachCompany,POBox389,Loveland,CO 80539,USA,Catalog # 22781-24), 4.743% N. (d) Compressed oxygen gas.99.99%. (e) Compressed helium gas.Nitrogen-free, 99.99%. D. Determination of Nitrogen Mill grain before analysis. No preparation is needed for liquids unlesstheyexceedcalibrationrangeandrequiredilution.UseN-free H2O for dilutions. Include dilution factor in calculation. When operating instrument, follow instrument manufacturers recommendations for size and introduction of test portion, furnace temperatures,burntimes,flowrates,andotheroperationalsettings. Establishinstrumentsbaselinebyrunningatleast3reagent(car- rier gas) blanks. Calibrate instrument for liquids by analyzing at least3replicatesofNstandardsolution,C(a).Calibrateforgrainsby analyzingatleast3replicatesofNEDTAstandard,C(b),andcheck midrangeresponseusingNTS,C(c).Calculatetheaverageresponse factor. E. Calculations Calculate response factor (RF) as follows: RF W PP = %Nstd std stdb where%Nstd=%Ninstandard,C(a)orC(b);Wstd=weightofstan- dard,g;Pstd=areacountofstandard;andPb=areacountofblank. Calculation of % N of test material is usually performed by inte- grator of instrument as follows: % N,by weight = () testb test PPRF W wherePtest=areacountoftestportion;Pb=areacountofblank;RF= appropriate response factor; and Wtest= test portion weight, g. Report results for beer and wort to nearest 0.001% N and grain to nearest 0.01% N. Calculate % protein in test portion as follows: Protein, % by weight = % N, (by weight) 6.25 where 6.25 = nitrogen-to-protein conversion factor. Report results to nearest 0.01% protein. References: ASBC: Beer 11B, Barley 7C. J. AOAC Int. (future issue). 2000 AOAC INTERNATIONAL Table 997.09Interlaboratory study results for determination of nitrogen in beer, wort, and brewing grains by combustion method SampleNo. of labsMean N, %srsRRSDr, %RSDR, %raRb Spent grain124.0190.2190.2705.56.70.6140.756 Barley122.1600.0360.0911.74.20.1020.193 Malt121.5260.0330.0692.24.50.0930.193 Rice101.0720.0150.0241.42.20.0410.066 Lab extract 1100.07690.00180.00252.33.30.00500.0070 Lab extract 2100.11790.00330.00532.84.50.00930.0148 Production wort 1100.13450.00220.00581.