4.6.01AOAC Of fi cial Method 962.09

Fi ber (Crude) in An i mal Feed and Pet Food

Ce ramic Fi ber Fil ter MethodFirst Ac tion 1962

Fi nal Ac tion 1971

Re vised First Ac tion 1982

AOCS–AOAC Method

A. Prin ci ple

Crude fi ber is loss on ig ni tion of dried res i due re main ing af terdi ges tion of sam ple with 1.25% (w/v) H2SO4 and 1.25% (w/v)NaOH so lu tions un der spe cific con di tions. Method is ap pli ca ble toma te ri als from which the fat can be and is ex tracted to ob tain awork able res i due, in clud ing grains, meals, flours, feeds, fibrousma te rials, and pet foods.

B. Re agents

(a) Sul fu ric acid so lu tion .—0.128 ± 0.003M. 1.25 gH2SO4/100 mL. Con cen tra tion must be checked by ti tra tion.

(b) So dium hy drox ide so lu tion.—1.25 g NaOH/100 mL, 0.313 ±0.005M, free, or nearly so, from Na2CO3. Con cen tra tion must bechecked by ti tra tion.

(c) Pre pared ce ramic fi ber.—Place 60 g ce ramic fi ber(Refractory Ceramic Fiber by Kaowool, Distribution International,Port Allen, LA, USA; Part No. BTCS128323K; CAS-142844-00-6)in blender, add 800 mL H2O, and blend 1 min at low speed.

De ter mine blank by treat ing ca 2 g (dry weight) of pre paredce ramic fi ber with acid and al kali as in de ter mi na tion. Cor rect crudefi ber re sults for any blank, which should be neg li gi ble (ca 2 mg).

(d) Al co hol.—95% or re agent al co hol, meth a nol, or isopropanol.

(e) Antifoam.—Dow Corning Corp. Antifoam A com pounddi luted 1 + 4 with min eral spir its or pe tro leum ether, or H2O-dilutedAntifoam B Emul sion (1 + 4). Do not use Antifoam Spray.

(f) Bumping chips or gran ules.—Bro ken Alundum cru ci bles orequiv a lent gran ules (RR Alundum 90 mesh, Norton Co., 1 NewBond St, Worces ter, MA 01606, USA; Tel: +1-508-795-5000) aresat is fac tory.

(g) Petroleum ether.—Ini tial boil ing tem per a ture, 35°–38°C;

dry-flask end point, 52°–60°C; ³95% dis till ing <54°C, and £60%

dis till ing <40°C; spe cific grav ity at 60°F, 0.630–0.660; evap o ra tion

res i due £0.002% by weight.

C. Ap pa ra tus

(a) Di ges tion ap pa ra tus.—With con denser to fit 600 mL beaker,and hot plate ad just able to tem per a ture that will bring 200 mL H2O at

25°C to roll ing boil in 15 ± 2 min. (Avail able from Labconco Corp.,8811 Pros pec t Ave , Kan sas C i ty, MO 64132 , USA;www.labconco.com).

(b) Ashing dishes.—Sil ica, Vitreosil 70 16 mm; or por ce lain,Coors Ce ramics Co. (600 9th St, Golden, CO 80401, USA,No. 60230), or equiv a lent.

(c) Des ic ca tor.—With ef fi cient desiccant such as 4–8 meshDrierite (CaCl2 is not sat is fac tory).

(d) Fil tering de vice.—With No. 200 Type 304 or 316 stain lesssteel screen (W.S. Ty ler, Inc., 8570 Ty ler Blvd, Men tor, OH 44060,USA; www.wstyler.com), eas ily washed free of di gested res i due.Ei ther Oklahoma State fil ter screen (see Fig ure 962.09A; avail ablefrom Labconco Corp.) or mod i fied Cal i for nia plas tic Büchner (seeFig ure 962.09B; con sists of 2 piece poly propy lene plas tic fun nel

man u fac tured by Nalge Co., 75 Panorama Creek Dr, PO Box 20365,Roch es ter, NY 14602, USA, Cat. No. 4280-0700, 70 mm [with outNo. 200 screen], or equiv a lent [also avail able from Labconco Corp.].Seal screen to fil ter ing sur face of fun nel, us ing small-tip sol der ingiron).

(e) Suc tion fil ter.—To ac com mo date fil ter ing de vices. At tachsuc tion flask to trap in line with as pi ra tor or other source of vac uumwith valve to break vac uum.

(f) Liq uid preheater.—For pre heat ing H2O, 1.25% H2SO4, B(a),and 1.25% NaOH, B(b), solutions to bp of H2O. Con ve nientsys tem, shown in Fig ure 962.09C, con sists of sheet Cu tank with3 coils of 3

8 in. (10 mm) od Cu tub ing, 12.5 ft (3.8 m) long. Sol derin lets and out lets where tub ing passes through tank walls. Con nectto re flux con denser and fill with H2O. Keep H2O boil ing with two750 watt ther mo stat i cally con trolled hot plates. Use Tygon for in letleads to res er voirs of H2O, acid, and al kali; use gum rub ber tub ingfor out lets. Ca pac ity of preheater is ad e quate for 60 anal y ses in 8 h.

D. Prep a ra tion of Test Sample

Re duce laboratory sam ple (rif fle is suit able) to 100 g. Place testsample in sealed con tainer for H2O de ter mi na tion and immediatelyde ter mine H2O. Grind re main der to uni form fine ness. (Weber millwith screen 0.033–0.040 in. [No. 18 or 20], Mi cro mill [HosokawaMi cron Pow der Sys tems, Inc., 10 Chat ham Rd, Sum mit, NJ 07901, USA] with screen 1

25– 116 in. [No. 18–No. 12], or Wiley mill with

1 mm [No. 18] screen give com pa ra ble fine ness.) Since mostma te ri als lose mois ture during grind ing, de ter mine H2O on groundtest sam ple at same time portion is taken for crude fi berde ter mi na tion.

E. De ter mi na tion

Ex tract 2 g ground test por tion (W1) with ether or pe tro leum ether. Iffat is <1%, ex trac tion may be omit ted. Pretreat ma te ri als that con tain

>1% car bon ate with 100 mL cold (<15°C) HCl to pre vent par tialneu tral iza tion of acid dur ing sul fu ric acid ex trac tion. Af ter 5 min fil ter

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Figure 962.09A. Oklahoma State fil ter screen.

and wash res i dues with cold wa ter to re move HCl. Trans fer to 600 mL

beaker, avoid ing fi ber con tam i na tion from pa per or brush. Add ca

1.5–2.0 g dry weight of pre pared ce ramic fi ber, 200 mL boil ing 1.25%

H2SO4, B(a), and one drop di luted antifoam. (Ex cess antifoam may

give high re sults; use only if nec es sary to con trol foam ing.) Bumping

chips or gran ules may also be added. De ter mine blank by treat ing ca 2 g

(dry weight) of pre pared ce ramic fi ber with acid and al kali as in

de ter mi na tion. If ex tremely fine ma te ri als are be ing an a lyzed and fil ters

are to be precoated with a fil ter mat, pre pare 2 beak ers of ce ramic fi ber

mix ture for each test as fol lows: Add 1.5 g dry weight of pre pared

ce ramic fi ber to each 100 mL beaker, then add 60–75 mL 1.25% (w/v)

sul fu ric acid, B(a), to each beaker and al low to soak un til precoat step.

Place beaker on di ges tion ap pa ra tus with pre ad justed hot plate and boil

ex actly 30 min, ro tat ing beaker pe ri od i cally to keep sol ids from

ad her ing to sides. Re move beaker, and fil ter as in (a) or (b).

(a) Using Oklahoma fil ter screen.—(1) Ex tremely fine ma te ri als

only. Skip to step (2) if no fil ter precoating is nec es sary. Precoat the

fil ter screen as fol lows: At tach Oklahoma fil ter screen to vac uum

flask. Turn on suc tion. Mix well the 60–75 mL 1.25% sul fu ric acid,

B(a), and 1.5 g ce ramic fi ber mix ture pre vi ously pre pared. In sert the

screen into beaker keep ing face of screen just un der the sur face of

liq uid un til all liq uid is re moved. With out break ing suc tion, pro ceed

to step (2).

(2) Turn on suc tion and in sert screen (precoated with ce ramic fi ber if

extremely fine ma te ri als are be ing an a lyzed) into beaker, keep ing face of

screen just un der sur face of liq uid un til all liq uid is re moved. With out

break ing suc tion or rais ing fil ter, add 50–75 mL boil ing water. (Work

rap idly to keep mat from be com ing dry.) Re move fil ter from beaker and

drain all H2O from line by rais ing above trap level. Re turn mat and

res i due to beaker by break ing suc tion and blow ing back. Add 200 mL

boil ing 1.25% NaOH, B(b), and boil ex actly 30 min. Re move beaker.

(3) Ex tremely fine ma te ri als only. Skip to step (4) if no fil terprecoating is nec es sary. Precoat the fil ter screen us ing the sec ondbeaker of ce ramic mix ture as de scribed in E(a)(1).

(4) Fil ter as in E(a)(2). With out break ing suc tion, wash with 25 mLboil ing 1.25% H2SO4, B(a), and three 50 mL por tions boil ing H2O.Drain free of ex cess H2O by rais ing fil ter. Lower fil ter into beaker andwash with 25 mL al co hol. Drain line, break suc tion, and re move mat byblow ing back through fil ter screen into ashing dish. Pro ceed as in E(c).

(b) Using Cal i for nia Büchner.—(1) Ex tremely fine ma te ri alsonly. Skip to step (2) if no fil ter precoating is nec es sary. Precoat thefil ter screen as fol lows: At tach Cal i for nia Büchner to vac uum flask.Fun nel must be level. Do not turn on vac uum. (Note: Cal i for niaBüchner may be held level above vac uum flask if vac uum can not beturned off.) Mix well the 60–75 mL 1.25% sul fu ric acid and 1.5 gce ramic fi ber mix ture pre vi ously pre pared. Pour ce ramic fi ber/acidslurry into Cal i for nia Büchner. Al low to set tle 5–10 s. Turn onmin i mum vac uum, just suf fi cient to form ce ramic fi ber “pad.”

(2) Trans fer con tents of beaker to a level Büchner un der novac uum (precoated with ce ramic fi ber if ex tremely fine ma te ri alsare be ing an a lyzed). Let res i dues and ce ramic fi ber set tle for 5–10 sand then ap ply vac uum. Rinse beaker with 50–75 mL boil ing H2O,and wash through Büchner. Re peat with three 50 mL por tions H2O, andsuck dry. Re move mat and res i due by snap ping bot tom of Büchneragainst white top while cov er ing stem with thumb or fore fin ger andre place in beaker. Add 200 mL boil ing 1.25% NaOH, B(b), and boilex actly 30 min. Re move beaker.

(3) Ex tremely fine ma te ri als only. Skip to step (4) if no fil terprecoating is nec es sary. Precoat the fil ter screen us ing the sec ondbeaker of ce ramic mix ture as de scribed in E(b)(1).

(4) Fil ter as in E(b)(2). Wash with 25 mL boil ing 1.25% H2SO4,B(a), three 50 mL por tions H2O, and 25 mL al co hol. Re move matand res i due; trans fer to ashing dish.

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Fig ure 962.09B. Mod ified Cal i for nia State Büchnerfun nel, 2-piece poly propy lene plas tic, cov ered with200-mesh screen, A, heat-sealed to edge of fil ter ingsur face. Figure 962.09C. Con tin u ous heater for dis tilled wa ter,

1.25% al kali, and 1.25% acid.

(c) Treat ment of res i due.—Dry mat and res i due 2 h at 130° ± 2°C.

Cool in des ic ca tor and weigh (W2). Ig nite 30 min at 600° ± 15°C.Cool in des ic ca tor and reweigh (W3).

Crude fi ber in ground test por tion, % = C= (loss in weight on ig ni tion – loss in weight of ce ramic fi ber blank)

100/weight test por tion

= [(W2 – W3) – (B2 – B3)] ´ 100/W1

where B2 and B3 are av er age weights of all blanks af ter oven dry ingand ashing, re spec tively.

Crude fi ber on de sired mois ture ba sis(or de sired dry mat ter ba sis), % =

C ´-

-

100 percent moisture desired

100 percent moisture in ground test sample

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Re port re sults to 0.1%.

Ref er ences: JAOAC 42, 222(1959); 43, 335(1960);44, 567(1961); 45, 578(1962); 65, 265(1982).

Re vised: February 2010

ã 2010 AOAC IN TER NA TIONAL