Physicochemical Tests AACC International Method 56-70.
01
Page 1 of 5
Sodium Dodecyl Sulfate Sedimentation Test for Durum Wheat
First approval October 3, 1984; Reapproval November 3, 1999
Objective
This method measures the relative gluten strength in whole durum wheat meal
without a sieving requirement. See Ref. 3. It is useful in screening plant breeder
and commercial durum wheat samples. The method is designed to test batch of
eight samples of durum wheat and is somewhat similar to Method 56-61.02.
Apparatus
1. Grinding mill.
2. Mill feeder (optional). Feed controller for grinding at 2 or 3 g/sec.
3. Mixer (optional). Same as in Method 56-61.02. Rack approximately 23 ×
12 × 2 in. is pivoted at center of each end and oscillates through 60°, 30° each
side of horizontal position, at rate of approximately 40 times per min. Rack is so
designed that eight 100-ml graduated cylinders can be quickly and securely
placed on it. Power is supplied by small electric motor.
4. Automatic pipets, two 50-ml, that empty and fill in less than 15 sec.
5. Stop-watch or interval timer.
6. Glass- or plastic-stoppered, 100-ml graduated cylinders having distance of
180–185 mm between zero mark at bottom and 100-ml mark.
Reagents
1. Sodium dodecyl sulfate (SDS). As standard or for tests, use pure grade of
>99% alkyl sulfate and >98% C12 alkyl sulfate. Lower-cost SDS should be
tested, and those batches that give sedimentation volumes nearly equivalent to
pure grade SDS may also be used.
2. Lactic acid stock solution. Dilute 100 ml 85% lactic acid with 800 ml dis-
tilled water. Reflux diluted acid 6 hr under water condenser to hydrolyze ester
linkages in polylactic acid molecules. After cooling to room temperature, dilute
two 10-ml aliquots to 100 ml with distilled water and then titrate 10-ml aliquots
of diluted acid to phenolphthalein end point, using standardized 0.1N NaOH.
Normality should be 1.2 ± 0.1 for undiluted lactic acid stock solution.
3. SDS-lactic acid reagent. To make 3.0% SDS, dissolve 30 ± 0.2 g SDS in
970 ml distilled water. Avoid inhalation of SDS dust. Add 20 ± 0.1 ml 1.2N
lactic acid to the 3% SDS and mix thoroughly.
Procedure
1. Grind 20 g durum wheat at constant grinding rate of 2 or 3 g/sec, using screen
with 1-mm diameter holes and feed controller or hand feeding. See Note 1.
2. Determine moisture on ground wheat samples by Method 44-15.02. Blend
thoroughly and weigh 6.3 ± 0.02 g (on 14.0% moisture basis) of eight samples
into weighing papers or boats.
3. Add 50 ml distilled water by automatic pipet to eight 100-ml graduated
cylinders. Proceed by mechanical or hand procedures described below.
http://dx.doi.org/10.1094/AACCIntMethod-56-70.01
Physicochemical Tests AACC International Method 56-70.01
Page 2 of 5
Sodium Dodecyl Sulfate Sedimentation Test
for Durum Wheat (continued)
Mechanical procedure
1. Quickly add eight weighed samples to 100-ml graduated cylinders, using
large powder funnel, and stopper each.
2. Hold first two cylinders horizontally (use both hands) and shake vigorously to
break meal cake. Immediately move cylinders horizontally lengthwise, alternately
right and left through space of about 7 in. at a rate of 12 times in each direction in
5 sec. Then place cylinders immediately on mixer rack at 30° from horizontal.
Repeat mixing procedure for remaining six cylinders and place in mixer rack.
3. Turn on mixer and timer simultaneously and mix for 10 sec. Turn off
mixer, stopping in horizontal position. Hold cylinders in rack horizontally
lengthwise by bracing rack with a board. Turn each cylinder 180° to wet
material that has come out of liquid and lodged on walls of cylinder. At 2, 4,
and 6 min, repeat mixing for 15 sec, holding cylinders in horizontal position
between mixings.
4. After mixing at 6 min, remove cylinders from rack, add 50 ml SDS-lactic
acid reagent, using 50-ml automatic pipet, and place cylinders back on rack.
5. Simultaneously start mixer and timer and mix for 15 sec, followed by hold-
ing cylinders in horizontal position. Then mix for 6 sec at 2 and at 4 min,
holding cylinders in horizontal position between mixings.
6. Immediately after last mixing, quickly remove the eight cylinders from
mixer and place in upright position.
7. Place cylinders in upright position.
8. After 20 min, read sedimentation volumes to nearest 0.5 ml.
9. Record temperature of sedimentation liquid and adjust sedimentation vol-
umes to 25° by Table I. See Note 2.
Hand procedure
1. Add the eight weighed samples quickly through large powder funnel to
cylinders containing 50 ml distilled water, and stopper cylinders.
2. According to hydration schedule below, simultaneously start timer and,
holding first two cylinders horizontally, break meal cake by initially vigorously
shaking cylinders, using both hands. Immediately move cylinders horizontally
lengthwise, alternately right and left through space of about 7 in. at rate of 12
times in each direction in 5 sec. 3.
3. Lay the two cylinders almost horizontally on bench with top of cylinder
elevated about 3 3/4 in. (in notched edge of 2 × 4 in. board). Agitate remaining
six samples according to first mixing in hydration schedule below and lay on
bench almost horizontally.
Time on Timer
Cylinder Numbers 1st Mixing 2nd Mixing 3rd Mixing 4th Mixing
1 and 2 0:00 2:00 4:00 6:00
3 and 4 0:30 2:30 4:30 6:30
5 and 6 1:00 3:00 5:00 7:00
7 and 8 1:30 3:30 5:30 7:30
Physicochemical Tests AACC International Method 56-70.01
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Sodium Dodecyl Sulfate Sedimentation Test
for Durum Wheat (continued)
4. At 2nd, 3rd, and 4th mixings, completely invert cylinders, then turn upright,
10 times in period of 15 sec, according to hydration schedule. Lay cylinders
almost horizontally between mixings.
5. After 4th mixing, place cylinders upright and remove stoppers on all eight
cylinders.
6. Add 50 ml SDS-lactic acid reagent to each cylinder, using 50-ml automatic
pipet.
7. Start timer and immediately mix contents of first two cylinders by inverting
and then turning upright 10 times in 15 sec. Lay the two cylinders almost hori-
TABLE I
Corrections to 25° C Volumea
Temp.
(°C) Sedimentation Volume (ml) Observed After 20 Min
20.0 22.7 26.0 29.3 32.6 34.8 37.0 39.2 41.4 43.6 45.8 48.0 50.2 51.3
20.5 22.7 25.9 29.2 32.5 34.6 36.8 39.0 41.2 43.4 45.5 47.7 49.9 51.0
21.0 22.6 25.8 29.1 32.3 34.5 36.6 38.8 40.9 43.1 45.3 47.4 49.6 50.7
21.5 22.5 25.7 28.9 32.1 34.3 36.4 38.6 40.7 42.8 45.0 47.1 49.3 50.3
22.0 22.4 25.6 28.8 32.0 34.1 36.2 38.3 40.5 42.6 44.7 46.8 49.0 50.0
22.5 22.4 25.5 28.7 31.8 33.9 36.0 38.1 40.2 42.3 44.4 46.5 48.6 49.7
23.0 22.3 25.4 28.5 31.7 33.7 35.8 37.9 40.0 42.1 44.1 46.2 48.3 49.3
23.5 22.2 25.3 28.4 31.5 33.5 35.6 37.7 39.7 41.8 43.8 45.9 48.0 49.0
24.0 22.2 25.2 28.3 31.3 33.4 35.4 37.5 39.5 41.5 43.6 45.6 47.7 48.7
24.5 22.1 25.1 28.1 31.2 33.2 35.2 37.2 39.2 41.3 43.3 45.3 47.3 48.3
25.0 22.0 25.0 28.0 31.0 33.0 35.0 37.0 39.0 41.0 43.0 45.0 47.0 48.0
25.5 21.9 24.9 27.9 30.8 32.8 34.8 36.8 38.7 40.7 42.7 44.7 46.7 47.7
26.0 21.9 24.8 27.7 30.7 32.6 34.6 36.6 38.5 40.5 42.4 44.4 46.4 47.3
26.5 21.8 24.7 27.6 30.5 32.4 34.4 36.3 38.3 40.2 42.1 44.1 46.0 47.0
27.0 21.7 24.6 27.5 30.3 32.3 34.2 36.1 38.0 39.9 41.8 43.8 45.7 46.6
27.5 21.6 24.5 27.4 30.2 32.1 34.0 35.9 37.8 39.7 41.6 43.5 45.4 46.3
28.0 21.6 24.4 27.2 30.0 31.9 33.8 35.7 37.5 39.4 41.3 43.2 45.1 46.0
28.5 21.5 24.3 27.1 29.9 31.7 33.6 35.4 37.3 39.2 41.0 42.9 44.7 45.6
29.0 21.4 24.2 27.0 29.7 31.5 33.4 35.2 37.0 38.9 40.7 42.6 44.4 45.3
29.5 21.4 24.1 26.8 29.5 31.3 33.2 35.0 36.8 38.6 40.4 42.3 44.1 45.0
30.0 21.3 24.0 26.7 29.4 31.1 33.0 34.8 36.5 38.4 40.1 41.9 43.8 44.6
30.5 21.2 23.9 26.6 29.2 31.0 32.8 34.5 36.3 38.1 39.9 41.6 43.4 44.3
31.0 21.1 23.8 26.4 29.0 30.8 32.6 34.3 36.1 37.8 39.6 41.3 43.1 44.0
31.5 21.1 23.7 26.3 28.9 30.6 32.3 34.1 35.8 37.6 39.3 41.0 42.8 43.6
32.0 21.0 23.6 26.2 28.7 30.4 32.1 33.9 35.6 37.3 39.0 40.7 42.5 43.3
32.5 20.9 23.5 26.0 28.6 30.2 31.9 33.7 35.3 37.0 38.7 40.4 42.1 43.0
(continued on next page)
Physicochemical Tests AACC International Method 56-70.01
Page 4 of 5
Sodium Dodecyl Sulfate Sedimentation Test
for Durum Wheat (continued)
TABLE I (continued)
Temp.
(°C) Sedimentation Volume (ml) Observed After 20 Min
20.0 52.4 53.5 54.6 55.8 56.8 57.9 59.1 60.2 61.3 62.4 63.5 64.6
20.5 52.1 53.2 54.3 55.4 56.5 57.6 58.6 59.7 60.8 61.9 63.0 64.1
21.0 51.7 52.8 53.9 55.0 56.1 57.2 58.2 59.3 60.4 61.5 62.6 63.6
21.5 51.4 52.5 53.6 54.6 55.7 56.8 57.8 58.9 60.0 61.0 62.1 63.2
22.0 51.1 52.1 53.2 54.3 55.3 56.4 57.4 58.5 59.6 60.6 61.7 62.7
22.5 50.7 51.8 52.8 53.9 54.9 56.0 57.0 58.1 59.1 60.2 61.2 62.3
23.0 50.4 51.4 52.5 53.5 54.5 55.6 56.6 57.7 58.7 59.7 60..8 61.8
23.5 50.0 51.1 52.1 53.1 54.1 55.2 56.2 57.3 58.3 59.3 60.3 61.4
24.0 49.7 50.7 51.7 52.8 53.8 54.8 55.8 56.8 57.9 58.9 59.9 60.9
24.5 49.3 50.4 51.4 52.4 53.4 54.4 55.4 56.4 57.4 58.4 59.4 60.5
25.0 49.0 50.0 51.0 52.0 53.0 54.0 55.0 56.0 57.0 58.0 59.0 60.0
25.5 48.6 49.6 50.6 51.6 52.6 53.6 54.6 55.6 56.6 57.6 58.5 59.5
26.0 48.3 49.3 50.3 51.3 52.2 53.2 54.2 55.2 56.2 57.1 58.1 59.1
26.5 48.0 48.9 49.9 50.9 51.8 52.8 53.8 54.8 55.7 56.7 57.7 58.6
27.0 47.6 48.6 49.5 50.5 51.4 52.4 53.4 54.3 55.3 56.2 57.2 58.2
27.5 47.3 48.2 49.2 50.1 51.1 52.0 53.0 53.9 54.9 55.8 56.8 57.7
28.0 46.9 47.9 48.8 49.8 50.7 51.6 52.6 53.5 54.5 55.4 56.3 57.3
28.5 46.6 47.5 48.4 49.4 50.3 51.2 52.2 53.1 54.0 54.9 55.9 56.8
29.0 46.2 47.2 48.1 49.0 49.9 50.8 51.8 52.7 53.6 54.5 55.4 56.4
29.5 45.9 46.8 47.7 48.6 49.5 50.4 51.3 52.3 53.2 54.1 55.0 55.9
30.0 45.5 46.5 47.4 48.3 49.1 50.0 50.9 51.9 52.8 53.6 54.5 55.4
30.5 45.2 46.1 47.0 47.9 48.7 49.6 50.5 51.4 52.3 53.2 54.1 55.0
31.0 44.9 45.7 46.6 47.5 48.4 49.2 50.1 51.0 51.9 52.8 53.6 54.5
31.5 44.5 45.4 46.3 47.1 48.0 48.9 49.7 50.6 51.5 52.3 53.2 54.1
32.0 44.2 45.0 45.9 46.8 47.6 48.5 49.3 50.2 51.0 51.9 52.7 53.6
32.5 43.8 44.7 45.5 46.4 47.2 48.1 48.9 49.8 50.6 51.4 52.3 53.2
a Select nearest temperature and volume observed. Move up or down column to 25°C line and
record difference between 25°C volume and volume nearest observed one. Add or subtract
this difference to or from observed volume. For volume outside table, one can derive
equation:
Sedimentation Volume = (Slope) (°C) + Constant. (1)
Slope for a selected 25° C volume (Volume 25) is calculated from equation:
Slope = (– 0.0202) (Volume 25) + 0.30. (2)
Then:
Constant for equation (1) = Volume 25 – (Slope × 25°C).
Physicochemical Tests AACC International Method 56-70.01
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Sodium Dodecyl Sulfate Sedimentation Test
for Durum Wheat (continued)
zontally. According to SDS-lactic acid schedule below, mix remaining six cylin-
ders and lay them down.
Time on Timer
Cylinder 1st 2nd 3rd Set Read
Numbers Mixing Mixing Mixing Upright Volume
1 and 2 0:00 2:00 4:00 4:15 24:15
3 and 4 0:30 2:30 4:30 4:45 24:45
5 and 6 1:00 3:00 5:00 5:15 25:15
7 and 8 1:30 3:30 5:30 5:45 25:45
8. Agitate cylinders at 2nd and 3rd mixings as described in step 7 and lay
almost horizontally between mixings.
9. After 3rd mixing, set cylinders upright and read sedimentation volumes to
nearest 0.5 ml after 20 min.
10. Record temperature of sedimentation liquid and correct sedimentation
volumes to 25° by Table I. See Note 2.
Notes
1. The same mill with the same sieve size should be used for all samples
because different mills and sieves can cause a large error in sedimentation vol-
umes. Mills giving almost equivalent sedimentation volumes should be selected
before doing intralab tests. Error is also reduced by using a constant grinding
rate. With proper adjustment of the mill gate, wheat can be pushed through the
mill with fingers at a set rate. A 3-g/sec feed rate should be reduced to 2 g/sec if
the mill speed is substantially reduced during grinding.
2. Temperature correction is not necessary in a laboratory where day-to-day
temperature is constant.
References
1. Axford, D. W. E., McDermott, E. E., and Redman, D. G. 1978. Small-scale tests of bread-making
quality. Mill. Feed Fert. 16(5):18.
2. Dexter, J. E., Matsuo, R. R., Kosmolak, F. G., Leisle, P., and Marchelo, B. A. 1980. The suit-
ability of the SDS-sedimentation test for assessing gluten strength in durum wheat. Can. J. Plant
Sci. 60:25.
3. McDonald, C. E. 1985. Sodium dodecyl sulfate sedimentation test for durum wheat. Cereal Foods
World 30:674.
4. Quick, J. S., and Donnelly, B. J. 1980. A rapid test for estimating durum wheat gluten quality.
Crop Sci. 20:816.
