AOAC Official Method 2000
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19CB7CC4BF9A464D8C40AD12D222AE70 |
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0.1 |
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2 |
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日期： |
2016-2-28 |
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文本摘录（文本识别可能有误，但文件阅览显示及打印正常，pdf文件可进行文字搜索定位）：
33.2.27A,AOAC Of fi cial Method 2000.18,Fat Con tent,of Raw and Pas teur ized Whole Milk,Gerber Method by Weight,First Ac tion 2000,Final Action 2004,(Ap pli ca ble to whole milk that is raw, batch pas teur ized or high,tem per a ture short time [HTST] pas teur ized, and/or ho mog e nized.),Cau tion: See Appendix B, safety notes on cen tri fuges, sul fu ric,acid, mer cury, and or ganic sol vents. Dis pose of waste,sol vents ac cord ing to ap pli ca ble en vi ron men tal rules,and reg u la tions.,See Ta ble 2000.18A for the re sults of the interlaboratory study,sup port ing ac cep tance of the method.,A. Prin ci ple,Milk is weighed into Gerber butyrometer con tain ing H2SO4.,Isoamyl al co hol is added and butyrometer con tents are vig or ously,mixed to dis solve curd and re lease fat. Fat is iso lated by,centrifugation and quan ti fied in the grad u ated por tion of the Gerber,butyrometer.,B. Re agents,(a) Sul fu ric acid.—Spe cific grav ity 1.820–1.825 at 15.5°C.,Tech ni cal grade.,(b) Isoamyl al co hol.—Spe cific grav ity 0.814–0.816 at 15.5°C,bp 128° to 133°C, free of wa ter, acid, fat, and furfural. (Cau tion:,Va pors are poi son ous.),C. Apparatus,(a) Stan dard Gerber milk-test butyrometer (grad u ated 0–8%),with lock stop per and key.—(See Fig ure 2000.18.) Clear,trans par ent, col or less, re sis tant boro sili cate glass, an nealed and free,from de fects; neck, large bulb, flat tube, and small bulb on a straight,me dian axis, joined smoothly to per mit free flow of liq uid; wall,thick ness ad e quate to pro vide suf fi cient strength but not less than,0.9 mm at any point. To tal length 190 ± 2.5 mm.,(1) Small bulb.—Tapered, with matte sur face on side above,grad u a tions for sam ple iden ti fi ca tion; #15.0 mm od; ca pac ity,mea sured be tween top grad u a tion line and in ter nal end of bulb,$1.5 mL.,(2) Large bulb.—#25.0 mm od; ca pac ity, 21.5 ± 0.4 mL.,(3) Neck.—Cy lin dri cal and plain; length, 15 ± 1.0 mm; 11.5 ±,0.5 mm id; rim, op tion ally re in forced; to tal thick ness of ex ter nal,rim, #2.5 mm di am e ter.,(4) Flat tube.—Uni form in cross-sec tion grad u ated length,$70 mm; uni form cross-sec tion be yond each ter mi nal grad u a tion,$3.0 mm; ex ter nal width, $10.0 mm. Grad u ated with per ma nent,clean lines of 0.10–0.20 mm width and per ma nently fused color,con trast ing sharply with color of milk fat, per pen dic u lar to flat tube,axis. Grad u ated vol ume in flat tube at 20°C is 1.000 mL (13.546 g,Hg), di vided into 80 equal parts, each equiv a lent in vol ume to,0.0125 mL. Er ror of to tal cal i brated length is not to ex ceed ±?of,small est grad u a tion. Grad u a tion lines are uni formly cen tered on flat,tube face, with 0.1% lines not less than 3 mm long, the 0.5% lines,ex tend ing 1 mm on each side be yond the 0.1% lines, and the 1.0%,lines ex tend ing not less than 1 mm on each side be yond the 0.5%,lines or ex tend ing across the en tire flat face. Each whole per cent,grad u a tion is iden ti fied by pig mented num bers run ning se ri ally,from 0 to 8, at the right and just above the whole-per cent lines, with,the zero mea sure ment near est the large bulb. Bot tles are iden ti fied,“Milk,” with the name or sym bol of the man u fac turer or dis trib u tor,per ma nently in scribed on the body and a sym bol ap plied af ter,recalibration where re quired to at test con for mance with reg u la tory,spec i fi ca tions.,(5) Testing.—Ac cu racy of each bot tle should be de ter mined,be fore use (usu ally by man u fac turer or cal i bra tion lab o ra tory).,Mer cury is added to the butyrometer by means of a spe cial,vol u met ric ap pa ra tus. Testing is con ducted at am bi ent tem per a ture,at 20° ± 2°C. The small bulb is opened to pre vent trapped air,bub bles. The ap pa ra tus has 2 vol u met ric set tings. The first set ting,de liv ers a vari able vol ume that per mits fill ing mer cury into the,butyrometer un til the me nis cus reaches the 0 grad u a tion line. The,sec ond set ting dis penses 1.000 mL mer cury, cor re spond ing to 8% on,the grad u ated scale. The dif fer ence be tween the ex pected and,ob served scale read ings must not ex ceed ±?di vi sion of a grad u a tion,line (±0.05% fat). The ac cu racy of the test ing ap pa ra tus is reg u larly,ver i fied with of fi cially cal i brated glass ware.,(6) Lock stop per and key.—Lock stop per is of re agent-re sist ing,rub ber, of stan dard ized di men sions to fit in neck of butyrometer,molded to pro vide a seat for the ball or plug, and with a chan nel for,the key. Rim and chan nel are re in forced by metal, plas tic, or other,firm bind ing in sert. Key is of noncorrodible ma te rial s……
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