Supporting Information for
Shear degradation of molecular, crystalline and granular
structure of starch during extrusion
Ming Li, Jovin Hasjim, Fengwei Xie, Peter J. Halley and Robert G. Gilbert
Table S1. Die pressure and temperature under different processing conditions.a
No
T
P
SS
.
WMS
(°C) (%) (rpm)
a
NMS
Pressure Temperature
HAMS
Pressure Temperature
Pressure Temperature
(bar)
(°C)
(bar)
(°C)
(bar)
(°C)
1
105
30
70
11.8 ± 3.4
80.1 ± 0.1
19.4 ± 1.7
80.5 ± 0.0
46.9 ± 3.4
80.5 ± 0.8
2
105
30
130
9.6 ± 0.7
82.1 ± 0.4
17.4 ± 3.7
81.1 ± 0.2
29.8 ± 4.9
81.5 ± 0.5
3
105
40
70
3.4 ± 0.3
80.7 ± 0.4
8.5 ± 2.1
80.7 ± 0.1
17.0 ± 3.0
80.2 ± 0.1
4
105
40
130
4.7 ± 0.7
80.0 ± 0.1
7.6 ± 1.7
83.4 ± 0.1
16.8± 0.6
81.0 ± 0.2
5
135
30
70
9.8 ± 2.3
82.3 ± 0.3
14.8 ± 3.1
83.8 ± 0.8
43.3 ± 0.8
83.0 ± 0.1
6
135
30
130
7.5 ± 1.1
82.1 ± 0.2
12.7 ± 1.0
83.5 ± 0.4
33.8 ± 1.6
81.9 ± 0.1
7
135
40
70
3.3 ± 0.3
81.0 ± 0.5
7.4 ± 0.7
83.8 ± 0.2
19.3 ± 1.7
80.3 ± 0.1
8
135
40
130
1.8 ± 0.4
81.0 ± 0.4
5.4 ± 0.4
83.4 ± 0.5
15.0 ± 0.9
82.1 ± 0.3
T = processing temperature (the highest temperature to represent the temperature setting), P =
plasticizer content (based on the total weight of starch mixture), numbers in the table are means ±
standard deviation.
1
Starch gelatinization with limited plasticizer content
Native waxy or high-amylose starch was premixed with 30 or 40% plasticizer (ratio of glycerol to
water is 2:3) and sealed in a plastic bag overnight for equilibrating. A differential scanning calorimeter
(DSC 1, Mettler-Toledo Inc., Columbus, US) was used to analyze starch gelatinization temperature.
Melting point and enthalpy of indium were used for temperature and heat capacity calibration. Starch
mixture (~5 mg) was placed in high pressure pan with gold seal. The slow heating rate of 5 ºC min-1 was
used to minimize any temperature lag due to the large mass of the high pressure pan.
Table S2. Starch gelatinization temperature with limited plasticizer contents.a
Plasticizer
To
Tp
Tc
content
(ºC)
(ºC)
(ºC)
(%)
Waxy maize starch
30
149 ± 8
160 ± 6
172 ± 3
Waxy maize starch
40
114 ± 1
135 ± 2
147 ± 5
High-amylose maize starch
40
190 ± 4
203 ± 3
213 ± 4
a
To, onset temperature; Tp, peak temperature; Tc, endset temperature. Mean ± SD from at least three
measurements.
The highest processing temperature along the barrel was 135°C, which was lower than the starch
gelatinization temperature at the plasticizer contents used in the present study (30-40%). The
gelatinization temperature is higher at lower plasticizer content, which is consistent with those reported
by others [1].
2
The effect of the cleavage of molecular branches during extrusion on the reduction of whole
molecular size
Taking waxy maize starch (~100% amylopectin) as an example, under the assumption that every
successful cleavage of an α-(1⟶4) glycosidic bond, i.e. the cleavage of a linear branch in a molecule,
results in two smaller molecules of equal size, the ratio of the molecular weight of a degraded
amylopectin molecule in extrudate to that of an intact, undegraded amylopectin molecule in native
starch can be used to estimate the number of cleaved glycosidic bonds:
Mextrudate  1  n
Mnative =  2 
(1)
Here n is the number of subsequent cleavages of glycosidic bonds in a molecule of molecular weight M.
Ten subsequent cleavages of α-(1⟶4) glycosidic bonds in an amylopectin molecule in native starch
will result in about a thousandth of its original molecular weight, which is a substantial reduction of the
molecular weight. Hence the number of cleaved amylopectin branches is much smaller than the total
number of branches in an amylopectin molecule (around 104), resulting in no apparent changes in the
SEC weight distribution of debranched starch (Level 1 structure) after extrusion. As there is no unique
relationship between the Vh and the molecular weight of branched molecules, and the molecular weight
of degraded amylopectin is not determined in the present study, the estimation of the number of
subsequent cleavages of glycosidic bonds was not performed.
Reference
[1] Liu, H., Yu, L., Xie, F., Chen, L., Gelatinization of cornstarch with different amylose/amylopectin
content. Carbohydr. Polym. 2006, 65, 357-363.
3