(
f
)
Sodium hydroxide solution
.—50%, carbonate-free, density
1.54. NaOH solution is stable indefinitely stored underHe.
(
g
)
Mobile phase A
.—10mM NaOH solution, carbonate-free.
Prepare carbonate-free solution as follows: Degas 2LH
2
O at least
15minwithN
2
orHe inbottleofde-gasmodule.Without shakingor
mixing 50%NaOH solution, (
f
), and while blowing He on liquid
surface, pipet 1.04mL from themiddle of bottle and add gently to
degassedH
2
O. Continue degassing solution 30min before use.
(
h
)
MobilephaseB
.—1MNaOH, carbonate-free.DegasH
2
Oas
in (
g
). Without shaking or mixing 50% NaOH solution, (
f
), and
whileblowingHeon liquidsurface, pipet109.5mLfrom themiddle
of bottle and add gently to degassed H
2
O. Continue degassing
solution 30min before use.
(
i
)
Glucose
.—
D(+)
-Dextrose anhydrous, reagent grade.
(
j
)
Fructose
.—Levulose, reagent grade.
(
k
)
Sucrose
.—Reagent grade.
(
l
)
Glucoheptose
.—
D
-Glucoheptose (Ferro Pfanstiehl
Laboratories, Inc., 1219GlenRockAve,Waukegan, IL60085,USA;
, or equivalent).
(
m
)
Lactose
.—Monohydrate, reagent grade.
(
n
)
Galactose
.—Reagent grade.
(
o
)
Maltitol
.—ca 98%. Store at 4°C when not in use (Sigma
Chemical Co., 3050 Spruce St, St. Louis, MO 63103, USA, or
equivalent).
(
p
)
Sugars standard solution
.—Dry glucose, fructose, sucrose,
glucoheptose, and galactose reference sugar standards in vacuum
oven 48 h at 55
°
±
3°C. (
Note
: Do not dry lactose and maltitol.)
Weigh100mgmaltitol, 100mgdextrose,100mggalactose,100mg
fructose,100mg lactose,and100mgsucroseand transfer intosingle
100mLvolumetric flask.Dissolve sugars completely inH
2
Ousing
magnetic stirrer bar and plate. AddH
2
O toweight of 100 g.
(
q
)
Glucoheptose internal standard solution
.—Weigh 100 mg
glucoheptose(
l
)and transfer into100mLvolumetricflask.Dissolve
sugar completely inH
2
Ousingmagnetic stirrer.AddH
2
O toweight
of 100 g.
(
r
)
Sugarsworking standard solutions
.—(
1
)
S
1
.—50mgof each
sugar/kg (glucoheptose, maltitol, dextrose, galactose, lactose,
fructose, and sucrose). Prepare by diluting 5.0 g glucoheptose
internalstandardsolution, (
q
),and5.0gsugarstandardsolution, (
p
),
to100gwithH
2
O. (
2
)
S
2
.—50mgglucoheptose/kgand25mg/kgof
each sugar: dextrose, maltitol, galactose, lactose, fructose and
sucrose. Prepare by diluting 5.0 g glucoheptose internal standards
solution, (
q
), and 2.5 g sugar standard solution, (
p
), to 100 gwith
H
2
O. (
3
)
S
3
.—50mg glucoheptose/kg and 5mg/kg of each sugar:
dextrose,maltose, galactose, lactose, fructose and sucrose. Prepare
by diluting 5.0 g glucoheptose internal standard solution, (
q
), and
0.5 g sugar standard solution, (
p
), to 100 gwithH
2
O.
D. Preparationof Test Products
Homogenize test samples immediately before analysis as
follows:
Before mixing in blender, freeze sticky or fatty products (e.g.,
chocolate and bars that form a paste-likemass in blender).
Cut gummy, sticky, andpaste-likeproducts that cannot bemixed
in blender into small pieceswith a knife or scissors so that particle
size is
£
5mmdiameter.
Shatter hard products in mortar (e.g., hard candies), so particle
size is
£
5mmdiameter.
E. Extraction
See
Figure
997.08
forflowdiagramofextractionandhydrolysis.
Accuratelyweigh to the nearest 0.1mg test portion (M
1
) from
D
containingca1g fructan (but not exceeding30gand/or5g starch);
place in 100mLbeaker containingmixing rod. [
Note
: For starchy
products (e.g., biscuits, cakes, other bakery products and cereals)
weigh 5 g test portion (M
1
) in 250 mL beaker containing mixing
rod.]
See
Table
997.08D
for guide values.
Add ca 40mLboilingH
2
O (add 100mL to starchy products) and
immediately check pH (Mecotrode, Hamilton P/H 238801/03, or
equivalent)withmild agitation. pH shouldbe between6.5 and8.0. If
necessary, adjust pH immediately with 0.05MKOH or 0.05MHCl.
(
Note
: Continue pHmeasurement and adjustment until test portion is
completelydissolved.)Rinse electrodewithboilingH
2
O.
Transfer solutionquantitatively intoweighed100mLvolumetric
flask(forstarchyproducts transfersolution to250mLflask), rinsing
beaker with boiling H
2
O. Place flask in water bath for 10 min at
85
° ±
2°Cwith continuous stirring.
Let solution cool to room temperature.Dilute to100mL,weigh,
and homogenize. (Weight of solution is M
2
). From this step on,
ensure thatsolutionsaremaintainedatoraboveroom temperature.
Because of possible presence of insoluble matter and/or fat in
some extracts, it may be difficult to homogenize them well. To
ensure proper homogenization, proceed as follows: Shake
volumetric flaskwithextract veryvigorously.Transfer extract into
beaker and continue very vigorousmixing usingmagnetic stirrer.
Whilemixing vigorously, withdraw 2 aliquots usingPasteur pipet:
50 g aliquot (for direct analysis, A
0
), and 15 g aliquot (for
hydrolysis,M
3
).
Dilute aliquots containing fructan to ca 1% fructanwithout any
heating.
F. EnzymaticHydrolysis
Weigh50ghomogenizedmixture from
E
and set aside for direct
analysis (assayA
0
).
(
1
)
First hydrolyzation
.—Transfer ca 15 g (weighed to nearest
10mg)homogenizedmixture(M
3
) into taredglassbottlewithscrew-cap
ã
2013AOAC INTERNATIONAL
Table 997.08B. Eluent grade for determinationof fructans in
foodsby ion exchange chromatography
Time, min
%Mobile phase
A
B
0
100
0
46
100
0
50
0
100
60
0
100
69
100
0
83
100
0
Table 997.08C. Detector timeprogram for determinationof
fructans in foodsby ionexchangechromatography
Time, s
Tension, V
0.00
0.05
0.20
0.05
0.40
0.05
0.41
0.65
0.60
0.65
0.61
–0.10
1.00
–0.10
FOS-01
FORWORKINGGROUP/ERPUSEONLY
DONOTDISTRIBUTE
