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D. By Means of U-Tube Oscillation – Digital Density Meter Method
(a)
Direct.
– Specific Gravity of juices.
(b)
Principal
Natural frequency of hollow oscillator varies with density of
material that fills tube. Electronic measurement of a time period is
converted to digital display of density, specific gravity and Brix.
(c)
Apparatus and Reagents
(1)
Digital density meter
: Anton Paar® GmbH, Anton-Paar-
Str.20, A-8054 Graz, Austria – Europe;
(www.anton-paar.com).
DMA 4500M digital analyzer with U-shaped, oscillating sample tube.
(2)
Hypodermic syringe
. As recommended in density meter
instructions.
(d)
Calibration of Density Meter
Calibrate digital density meter at 20.0°±0.1°C with air and H
2
O.
Use hypodermic syringe to inject liquids into analysis tube. Fill tube
completely so no gas or solids are entrapped
(e)
Determination
Inject test sample, if carbonated beverage (ensure
decarbonation), into filling tube. Be sure no gas is entrapped in tube.
Let thermostated analysis tube reach thermal equilibrium. Obtain
specific gravity measurement if desired result are Brix then convert to
Brix using
AOAC942.33
– Degrees Brix, specific gravity, and
degrees Baume of sugar solutions (Plato Table).
References: Anton Paar® GmbH.
J. of AOAC Intl
, Vol XXX, No.
XX (20XX).
J. Am. Soc. Brew. Chem
.
36
, 118 (1978).
Methods of
Analysis
(1992) 8
th
Ed., American Society of Brewing Chemists,
3340 Pilot Knob Rd, St. Paul, MN 55121, USA, Beer 2-B.
AOAC Research Institute
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