9.4.2
Pre-extraction
As high fat levels can prevent effective
hydrolysis, samples with 10 % fat content should
be pre-extracted with the same type of solvent as
used in the final extraction.
1. Weight in the sample with a precision of
1000
±
2 mg. Load the glass thimble with 1 g
celite and the sample. Do not cover with
cotton.
2. Fit adapters on the thimbles, by introducing
them into the thimbles in such a way that the
circlip is compressed progressively into the
thimble, (i.e. the closed side of the circlip is
pressed in first and then working towards
the open side), and insert them into the
Soxtec HT Extraction Unit.
3. Add solvent and extract for 10 minutes in
"Rinsing" position.
4. After the extraction, dry the extraction cups
in an oven at 100°C for 30 minutes. Let
them cool down and weigh them. Calculate
percentage extracted fat. If the fat content is
high, 20% , it is recommended to use a
second extraction cup for the final
extraction.
5. Remove the thimble holders from the glass
thimbles. Transfer the pre-extracted sample
as quantitatively as possible from the glass
thimble to a sample tube for acid hydrolysis.
Proceed from step 2 of the hydrolysis part.
Note: Use the same glass thimbles for the
filtration after hydrolysis (see 9.4.3 Pos. 4)
9.4.3
Hydrolysis
1. Weigh the samples with a precision of 1000
±
2 mg and transfer them to the sample
tubes.
2. Add 1-2 g of celite and 100-120 ml of the
acid solution to each sample tube. The level
of the acid solution must be over the top of
the cover of the heaters.
3. Insert the tubes into position in the 1047
Hydrolyzing Unit (Fig. 4). Lower the
suction tubes to the fume exhaust position
by pulling the handle upwards (Fig. 5). The
teflonpart should rest on the top of the
sample tubes and the suction tubes should
be about one centimeter down in the sample
tubes.
4. Place the glass thimbles into the thimble
supports (Fig. 6) and insert them into the
Hydrolyzing Unit (Fig. 7).
Note: If pre-extraction according to section
9.4.2 has been carried out, check that the
thimbles are used for the same samples as
in pre-extraction.
5. Start the water aspirator pump for the fume
exhaust system. Open vacuum valves (Fig.
7) under each thimble. Adjust during boiling
for low fume exhaust.
6. Turn on the heater to maximum effect and
place the reflector in front of the sample
tubes. When the solution starts boiling,
adjust to a gently boiling speed with the
heater control
(Fig. 8).
7. At the end of the hydrolysing period, turn
off the heater and remove the reflector.
8. Open the cold water tap for the condensers
(approximately 2 1/m).
9. Pull down the suction tube handle to pos. 1
(Fig. 5). Dilute the acid solution in each
tube with some 100 ml of 20-25°C distilled
water. Close the vacuum valve (Fig. 7)
under each thimble.
10. Lower the suction tubes to pos. 2
(Fig. 5). Open the vacuum valve
(Fig. 7) under one thimble and suck up the
sample solution and as much as possible of
the solid particles in the solution. Close the
valve and repeat in the same way with the
rest of the tubes.
11. Wash each tube by opening the vacuum
valve and spray 5x50 ml of approximately
50°C distilled water, by using the water
sprayer (Fig. 9).
12. Raise the suction tubes and take out one of
the sample tubes. Cover the cleaning rod
with a thin layer of defatted cottonwool and
wet it with acetone. Clean the inside of the
tubes by gently pushing and pulling the
cleaning rod up and down in the tube
(Fig. 10). Take a small piece of the
cottonwool and clean the outside of the
suction tube if necessary. Place each pad of
the cottonwool on the top of the sample
residue in the glass thimble.
Note: Do not have the valves in closed
position when the Hydrolysing Unit is shut
down.
9.4.4
Drying
To make the wet sample residue lyophilic and
achieve effective solvent extraction, the residue
and thimble must be dried.
Alt. 1: Dry overnight at 60-80°C in a oven.
Alt. 2: Dry in a microwave oven with turntable
at medium power for 30-60 minutes.
Most samples can be dried in a microwave oven,
except meat and fish products.
1
Warning
Do not use a microwave oven if residues
of organic solvents are present.
9.4.5
Solvent extraction
1. Fit the adapters, as written in 9.4.2:2, to
each thimble and insert them into the Soxtec
HT Extraction Unit.
2. Extract and analyse the samples according
to the Soxtec HT Extraction Unit
instructions, see Soxtec HT manual.
9.4.6
Calculation
Calculate the fat content according to the
formula below.
W3 = The extraction cup weight after fat
extraction and cooling in desiccator.
W2 = Clean and predried extraction cup.
W1 = Sample weight.
% Fat =
W3-W2
x 100
W1
If a pre-extraction was required, using two
extraction cups, add the two results that have
been calculated, and the sum is the total fat in
the sample.
F1 =
Fat content after pre-extraction.
F2 =
Fat content in final extraction.
% Fat/Oil = F1 + F2
9.5
MAINTENANCE
9.5.1
Change of vacuum valve
1. Loosen all neoprene tubings carefully that
are connected to the suction tubes, by
removing the plastic straps.
2. Lower the suction tubes down the horizontal
plate, so the suction tubes rest against the
bottom of the oven.
1047 Instruction Manual, Rev. 2.2 10/00, 1000 3315
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