AOAC Methods for Review in Codex STAN 234_11-2018

AOAC Official Methods Listed in CXS 234 for Milk and Milk Products

105

33.2.27

( 3 ) Testing .—Accuracy of each bottle shall be determined before use (usually by manufacturer or certified laboratory). Bottle calibration accuracy is determined by placing bottle upside down on Babcock bottle calibration apparatus (Nafis tester or modified Nafis tester) that is capable of delivering known volumes of Hg into Babcock bottle neck. Bottle calibration apparatus delivery is calibrated and volume of Hg contained between 8 and 4% (0.800 mL), 4 and 0% (0.800 mL), and 8 and 0% (1.600 mL) marks is determined. Accuracy of bottle neck calibration may be determined before or after attachment to bulb. Accuracy should be at least ± 0.04% on scale of 18 g milk-test bottle. [Reference: J. AOAC Int . 78 , 463(1995).] ( b ) Pipet. —Standard milk pipet conforms to following specifications: Total length . . . . . . . . . . . . . . . . . . . . . . . £ 350 mm ODof suction tube . . . . . . . . . . . . . . . . . . . . 6–8mm Length of suction tube. . . . . . . . . . . . . . . . . . . 130mm OD of delivery tube [must fit into bottle, ( a )] . . . . . 4.5–5.0mm Length of delivery tube (slightly longer than bottle neck, must not touch milk test portionwhen delivered) . . . . . . . . . 105–125mm Distance of graduationmark above bulb . . . . . . . . 15–45mm Nozzle parallel with axis of pipet, but slightly constricted so as to discharge in 5–8 s when filled with H 2 O Graduation, marked to contain 17.6 mL H 2 O at 20°C when bottom of meniscus coincides with mark on suction tube Maximumerror in graduation . . . . . . . . . . . . . . £ 0.05mL To test pipet, place tip of pipet against firm rubber surface, clamp pipet in vertical position, and use buret (Class A—graduations £ 0.05 mL) to fill pipet to graduation mark with H 2 O (at 20°C). ( c ) Acid measure. —Device used tomeasure H 2 SO 4 should deliver in range from 10 to 20 mL. Use device that can be set to consistently deliver appropriate amount of acid to obtain desired milk acid reaction temperature in D . ( d ) Centrifuge or “tester.” —Standard centrifuge, however driven, must be constructed throughout and so mounted as to be capable, when filled to capacity, of rotating at necessary speed with minimum vibration and without liability of causing injury or accident. Centrifuge must be heated, electric or otherwise, to 46 ° –51°C during centrifuging. It must be provided with speed indicator, permanently attached, if possible. Proper rate of rotation may be determined by reference to Table 989.04 . Rotation speed Table 989.04. Proper rate of centrifuge rotation for known diameter of wheel to achieve 164 ´ g Diameter of wheel, cm Diameter of wheel, in. rpm 35.6 14 909 40.6 16 848 45.7 18 800 50.8 20 759 55.9 22 724 61.0 24 693

AOAC Official Method 989.04 Fat in Raw Milk Babcock Method Final Action 1920

Revised First Action 1989 Revised First Action 1997 Final Action 2000

(Applicable to raw, whole milk.) Results of the interlaboratory study supporting acceptance of the method (for sections A – D ): s r = 0.037; s R = 0.047; RSD r = 0.901%; RSD R = 1.147%; r = 0.105; R = 0.133 A. Principle Known weight of milk is placed into Babcock bottle and H 2 SO 4 is added. Generated heat releases fat, which is then isolated by centrifuging and addition of H 2 O. Fat is quantitated in graduated portion of Babcock bottle. Result is expressed as % fat by weight. B. Reagents ( a ) Sulfuric acid .—Specific gravity 1.82–1.83 at 20°C. ( b ) Mercury .—Purity ³ 99.99%. Used for testing accuracy of Babcock bottles. C. Apparatus ( a ) Standard Babcock milk-test bottle .—8%, 18 g milk-test bottle, total height 160–170 mm (6.3–6.7 in.). Bottom of bottle is flat, and axis of neck is vertical when bottle stands on level surface. ( 1 ) Bulb. —Capacity of bulb to junction with neck is ³ 45 mL. Bulb may be either cylindrical or conical. If cylindrical, od of base must be 34–36 mm; if conical, od of base must be 31–33 mm, and maximum diameter, 35–37 mm. ( 2 ) Neck. —Cylindrical and of uniform diameter from ³ 5 mm below lowest graduation mark to ³ 5 mm above highest. Top of neck is flared to diameter of ³ 10 mm. Graduated portion of neck is ³ 75 mm long and is graduated in whole %, 0.5%, and 0.1% from 0.0 to 8.0%. Graduations may be etched, with black or dark pigment annealed to graduation, or may be unetched black or dark lines permanently annealed to glass. Graduation line widths £ 0.2 mm. Tenth % graduations are ³ 3 mm long; 0.5% graduations are ³ 4 mm long and project 1 mm to left; and whole % graduations extend at least half way around neck to right and project ³ 2 mm to left of 0.1% graduations. Each whole % is numbered, with numeral placed to left of scale. Vertical line must be etched and annealed with black or dark pigment or must be etched into dark stripe permanently annealed to glass. Etched vertical line is located 1 mm to right of 0.1% graduation marks and extends ³ 1 mm above 8% line and ³ 1 mm below 0% line. If vertical line is etched into dark vertical stripe, then dark vertical stripe must extend ³ 1 mm above the 8% line and ³ 1 mm below 0% line. Dark vertical stripe should be £ 2.0 mm wide and etched line must be £ 0.2 mm wide. Zero line ( £ 0.2 mmwide) must be etched and annealed with black or dark pigment, or not darkened but etched into dark horizontal stripe ( £ 2.0 mm wide) permanently annealed to glass. Zero and vertical etched lines, with or without annealed pigment, should be of sufficient depth to hold point of dividers. Capacity of neck for each whole % on scale is 0.200 mL. Maximum error of total graduation or any part thereof must not exceed 0.008 mL.

ã 2005 AOAC INTERNATIONAL

10/9/2018

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