melt transformation extrusion of soy protein
TRANSCRIPT
MELT TRANSFORMATION EXTRUSION OF SOY PROTEIN;/'
A Thesis Presented to
/
The Faculty of the College of Engineering and Technology
Ohio University
In Partial Fulfillment
of the Requirement for the Degree
Master of Science
by
Corry S. Hendrowarsito;;:;'
November, 1984
OHIO UNIVERSITYLIBRARY
Acknowledgements
The author wishes to express her appreciation to
Professor John R. Collier, without whose guidance and
counsel this study could have not been possible. Thanks is
al so extended to the facul ty of the Department of Cherni cal
Engineering for their advice and help. Special thanks is
also due to Indro Subowo, whose help and patience were
invaluable.
Finally, thanks is due to my parents and brothers whose
support were unlimited.
i
ABSTRACT
Hendrowarsito, Corry Suzannadevi. M.S. November 1984.Chemical EngineeringDirector of Thesis: Dr. John R. CollierTitle: Melt Transfor.ation Extrusion of Soy Protein (pp.104, 42 figures, 12 tables)
The purpose of thi s research was to apply the ~1el t
Transformation Extrusion Process to the extrusion of soy
protein. As a result, an improved layered fibrous texture
occurs in soy protein extrudates.
Commercially, fibrous soy protein products are used as
meat extenders and substitutes. The premoist soy protein was
extruded in a system consisting of 3/4 1t - d i a me t e r Brabender
single screw extruder, an eighteen inch conditioner zone,
and a uniaxial die having a deformation ratio of 24:1, 1/16 11
x 1/2 11 ribbons were produced. Variables studied included
process temperature profile (160-90 oC), screw speed (40-80
RPt4) and moisture content (30-40%). The effect of these
variables on die pressure, absorption, bulk density, product
temperature, and extruder throughput was investigated using
response surface analysis. Studies using optical and
scanning electron microscopy were conducted to examine the
product structure.
i i
The r~TE process produced higher pressure drops
(300-1500 psi) and longer residence times (5-15 minutes)
compared to the more conventional low pressure extrusion
(less than 500 psi).
Control of both shear rate or stress, and temperature
profile were found to be the most important factors. Product
temperature and operating pressure were significantly
affected by screw speed. Shear rate or stress, and pressure
decreased with increasing moisture.
The best operating conditions for maximum texturization
. 0 0 0 0were a temperature pr o f t l e of 160 -135 -110 -50 C, 80 RPM,
and 40% moisture. Differential scanning calorimetry was
employed to determine the crystallinity of the dough. The
result indicated that DSC was not an appropriate method.
Scanning electron microscopy displayed clearly the
physical changes which occurred due to process conditions.
iii
Table of Contents
Page
List of Figures
List of Tables ..
Chapter
vi
i x
1 . Introduction 1
2. Background of Study ..
2.1 Protein
4
6
2.2
2 • 3
Soy Protein and Its Commercial Use
Mechanism of Fiber Formation.
8
11
3. Theory 16
3.1 Melt Transformation ExtrusionProcess (MTE) ••••••• 16
3.1.1 Shear Stress and Flow InducedCrystallization . . . . . . 17
3.1.2 Pressure Effect on Crystallization 21
3.2 Extrusion Cooking
3.3 Characteristics of Textured ProteinProd uc ts . . . • . . . • . . .
3.4 Response Surface Analysis (RSA)
4. Description of Equipment and Material
24
28
29
31
5 • Experimental Procedure
5.1 Preliminary Experimentation
5.2 Experimentation
5.3 Specimen Testings
i v
40
41
45
47
Chapter
6. Results .......•.
7. Discussion ...
8. Conclusion ....•.•..
9. Recommendation ...
Bi bl t ography •......•.
Appendixes
A. Experimental Data •.••••••
B. Response Surface Analysis Program
C. Response Surface Analysis Results
v
Page
50
74
87
89
91
97
101
102
list of Figures
Figure
1. Mechanism of Protein Denaturation.
Page
12
2 . Structure of Spherulite . 18
3 . Su99ested i~ 0 del for Fib e r For mat ion •
4. Elongational Flow in a Converging Die ..
18
20
5 . Nematic Liquid Crystalline Form. 22
6. Cross Section of a Typical Food Extruder. 25
7 . Sc he (0a tic Di a gram for the Un i a x i a 1- rib bon Die 33
8 .
9 .
10.
Schematic Diagram for the Fiber Die
Photograph of Uniaxial Die Halves.
Photograph of Fiber Die Pieces ..•
34
35
35
11. Schematic Diagram for the Extrusion Processwith a Melt Conditioner Zone . . . 38
12 .
13 .
14.
Front View of the Extrusion Set-up
Simplified Extrusion Flow Sheet
Extrusion Rate versus Screw Speed atdifferent Moisture Contents ...
39
45
52
15. Extrusion Rate versus Screw Speed atdifferent Process Temperature. 53
16. The Effect of Screw Speed and Moisture on theExtrusion Rate at 8 Constant ProcessingTemperature of 150 C (zone II). • . . • 54
17. The Effect of Processing Temperature andMoisture on Extrusion Rate at a ConstantScrew Speed of 70 RPM ••..••.... 55
vi
Figure
18.
19 .
20.
Page
Die Pressure versus Screw Speed at differentProcessing Temperatures · · · . . . . · . . 56
Die Pressure versus Screw Speed at differentNoisture Contents . . . · · · · . . 57
Die Pressure versus Screw Speed for the FiberDie Runs . . . . . . . · · · . . · 59
21. The Effect of Screw Speed and Moisture on theDie Pressure at a COBstant ProcessingTemperature of 152.8 C (zone II). . . . 60
22. The Effect of Temperature and Moisture on theDie Pressure at a Constant Screw Speed of45 RPM • • • • •• •••••• 61
23. The Effect of Temperature and Screw Speed onthe Die Pressure at a Constant MoistureContent of 40 w/o • • • • • • • . • • • 62
24. DSC Endotherm for Indium 63
25. Typical DSC Endotherm of Texturized SoyProtein Product ... ...•.. 64
26. The Effect of Temperature and Moisture on theProduct Absorption at a Constant MoistureContent of 35 wlo . . . . . . 65
27. The Effect of Temperature and Moisture on theProduct Absorption at a Constant ScrewSpeed of 70 RPM ••• •••••• 66
28. The Effect of Screw Speed and Moisture on theProduct Absorptionoat a Constant ProcessingTemperature of 150 C (zone II) .•.• 67
29. The Effect of Temperature and Screw Speed onthe Product Bulk Density at a ConstantMoisture Content of 35 w/o • • • • • • 69
30. The Effect of Temperature and Moisture on theProduct Bulk Density at a Constant ScrewSpeed of 76 RPM •...•..•.•••. 70
v; i
Figure Page
31. The Effect of Temperature and Screw Speed onthe Product Temperature at a ConstantMoisture Content of 27 wlo .. . . . . 71
32. The Effect of Temperature and Moisture on theProduct Temperature at a Constant ScrewSpeed of 135 RPM . .. 72
33. The Effect of Temperature and Moisture on theProduct Temperature at a Constant Process-ing Temperature of 140°C (zone II) .... 73
34. Optical Micrograph of Fiber Die Runs, 12X .. 77
35. Scanning Electron Micrograph of Run F4 showsporous structure, 700X . . . . . . . . .. 77
36. Processing Temperature Profile at differentHeating Zones. . . . . . . . . . . . . .. 81
37. Residence Time versus Screw Speed 83
38. Scanning Electron Micrograph of UntexturizedSoy Protein with Strands of Fibers, lOOOX. 84
39. Optical Microscope of Fibrous Structure ofRun F3, 150X . . . . . . . . . • . . . .. 84
40. Scanning Electron Micrograph of IsolatedFiber of Run F3, 4000x . .. ... 86
41. Scanning Electron Micrograph of Run 13, lOOOX 86
42. SAS Program . • .
vii i
101
Table
list of Tables
Page
1. Extruded versus Spun Texturizing Ingredients 5
3. Amino Acid Composition
2 • Typical Composition of Soy Flours,Concentrates and Isolates 9
9
4. Changes in Characteristics of Soybean Proteinat High Temperature Heating. . . . . . .. 15
5. Experimental Pattern of Processing ConditionCode s . . . . . . . . . . . . . . . . . .. 44
6. Effects of Variables on Extrudate Character-istics . . . . . . . . 75
7. Die Temperatures
8. Flow Rates .....
97
98
9 • Pressure Profiles. 99
10. Extrusion characteristics 100
12. Analysis of Variance
11 . Regression Coefficients. 102
103
13. Levels of Variables Significance on ExtrudateCharacteri sti cs • . . . • . • . . • • • •• 104
ix
Chapter 1
INTRODUCTION
The texturization of vegetable protein products to
simulate meat has been one of the significant developments
in the food engineering industry. Once these products have
been texturized and rehydrated they can be used as meat
extenders or total meat substitutes.
Food manufacturers are interested in these products,
because their use as ingredients imparts favorable changes
in the structure, texture, and composition of the finished
foods, at an attractive price. Those products which have
been texturally and histologically restructured through
processing have fibrous structures and integrity similar to
that of muscle ti ssue. They can be produced by one of the
two basic processes, wet spinning and thermoplastic
extrusion [1]. The topic of this work is the extruded
material.
Theoretically, the temperature of extrusion varies from
80 0 to 17SoC (180 o-350 oF). There is very little degradation
o f the protein, which contains 20 to 40% moisture. The
resulting pressure ranges from 14 to 60 atm (200-900 psi).
Al though the process has rel ied heavily on the theory of
plastic extrusion, food extrusion cooking has some
characteristics of its own. All aspects of production,
2
storage, handling and environment should be considered a
long with economic considerations.
At Ohio University, a melt transformation extrusion
(MTE) process to produce highly oriented semi-crystalline
polymers has been investigated by Collier [3J. In this
process a plasticating extruder supplies molten polymer to
specifically designed dies through a melt conditioner
(medium pressure pipe). The molecules of the molten polymer
are partially oriented by passing the material through this
conditioner zone (2000-8000 psi) immediately before ex
trusion through a converging die. As shown in this research,
MTE was at a lower pressure range (500-2000 psi). This
process was useful in enhancing the fibrous texture of soy
protein.
Reports have dealt with the extrusion texturization of
soy protei n. The product characteri sti cs are thought to be
dependent upon the following independent variables: screw
speed, feed rate, moisture, product temperature, residence
time, and protein content [3-5]. The objective of this
investigation was to apply the MTE process to soy protein
and to observe a definite layered structure of fibers in the
soy protein extrudate under the predetermined conditions.
Texture was used as the basic tool of observation. It
can be viewed as a direct consequence of microstructure,
which originates from chemical composition and physical
forces acting upon it. Scanning electron micrographs of the
3
inner layers will be used to reveal the morphology of the
soy protein extrudate. Advantages of using the scanning
electron micrographs in studying the ultrastructure of
soybean and soy protein have been shown by previous
researchers [6-8]. Optical microscopic observations have
also been used in support of the textural observations.
Chapter 2
BACKGROUND OF STUDY
In recent years texturized vegetable protein process
for the transformation of powdered soy protein into a
meat-l ike texture has received some acceptance and
popularity. The simulation of meat depends on such textural
characteristics as thickness, smoothness, cohesiveness,
shear and friction forces [9]. It has been thought that
this kind of texture develops with the formation of fibers.
Fiber formation can be obtained through several process
which can be either chemical or physical.
Many new processes have been developed to yield
textured protein products. The two most basic industrial
processes for generating texture from proteins are spinning
and extrusion. Spinning of protein fibers involves
modification of the isolated protein through solubilization
in alkali [10]. During the alkali treatment the globular
protein unwinds and deaggregates to form a series of
dispersed flexible chains. When the material is ready for
spinning, it is forced into alignment through a porous
membrane. Protein fibers (about 0.003 in diameter), which
are partially oriented, are coagulated in an acid bath. The
fibers are then stretched to a desirable strength and cut
into a desirable size. The stretching causes further
5
orientation of the protein fibers.
On the other hand,' the thermoplastic extrusion process
is a simpler process. Researchers have detailed variations
of the basic thermoplastic extrusion process [11-14]. The
process involves plasticizing flour and water in an extruder
to high temperatures and pressure. The emerging extrudate
flashes off steam and expands, resulting in a dry and
textured product. This technique has been chosen for this
study because of its advantages over the spinning process
(table 1), and its similarities to the MTE process. Other
processes that are less popular are gelation [15J and direct
steam texturization [16]. Thus, extrusion is not the only
method of texturization [17]. Further details on the
extrusion process and soy protein will follow in chapter 3.
Table 1. Extruded versus Spun Texturizing Ingredients [14J
Thermoplasticextrusion
Fi berspinning
Advantages
*Inexpensive*Simple process*Good protein quality*Can absorb waterand fat
*Thermodynamicallyeffecti ve
*Versatile*Good structuredanalogue texture
Disadvantages
*Limited use*Poor structuredanalogue texture
*Flavor, color
*Expensive*Technically difficult*Low protein quality*Flavor, color
6
2.1 Protein
Native protein molecules are known to be folded with
well-defined, unique three dimensional structures. Princi-
pally the molecules of proteins are made up of carbon, hy-
drogen, oxygen, nitrogen, sulfur and some traces of phospo-
ruse The protein consists of small units, called amino
acids. These amino acids play a very important role in
pol ymer t za t t on to form a long chained molecule. They have
toe following chemical formulas typified by [18]:
leucine
CH 3
>CH~HCOOHCH 3 NH 2
isoleucine
lysine
CH 3
>CHyHCOOH
CH 3 NH 2valine
The amino (-NH 2) and carboxyl (-COOH) groups are
chemically active, basic and acidic, respectively. Thus the
7
amino group of one amino acid readily combines with the
carboxyl group of another and forms a peptide bond at the
center (eq. 1).
o RII I
NH 2-R '-CH2-COOH + NH 2-R-CH 2-COOH -- H2-y-C-j-I-COOH + H20R' H H (1)
dipeptide
The remaining free amino and carboxyl groups at the end can
react with independent amino acids to form polypeptides.
The possibility of variations among proteins is
enormous. This variation depends on a combination of
different amino acids, different sequences of amino acid
wi thi n a cha in and di fferent shapes the cha in assumes. The
chain can be coiled, folded or straight. These differences
are responsible for the differences in texture of the
proteins. This complex configuration of a protein can be
modified to form fibrous texture by subjecting the material
to external forces utilizing protein psychochemical
properties (dough forming, film forming, moisture holding,
emulsifying, thickening, gelling, stabilizing, cohesiveness
and others [19]).
8
2.2 Soy Protein and Its Co.mercial Use
The utilization of soy protein depends on its
functional and physical properties, nutritional and
economical values. The functional value of soy protein,
including its physical and chemical properties, have been
reported [20-22]. Some of these properties, such as
emulsification, viscocity and water holding capacity are
important in meat formulation. These functional properties,
which contribute performance aspects in affecting structure
and texture formation, outweigh their nutritive contribution
[23].
There are three types of commercially available soy
protei n: soy flour (1 ess than 65~ protei n ) , soy protei n
concentrate (65 to 89% protein), and soy protein isolate
(90% and higher protein) [23-24]. All three types of these
products can be used to yield a range of textured vegetable
protein; the cost increases with the protein concentration.
A typical analysis of soy protein concentration is tabulated
in table 2. Soy concentrates (70%) is used as the raw
material in this study.
There are three dietary uses of texturized vegetable
protein (TVP) [26]:
Table 2. Typical Composition of Soy Flours, Concentrates andIsolates [25J
Per cent (moisture-free basis)Soy flours Concentrates Isolates
Protein 56.0 72.0 96.0Fat 1.0 1.0 0.1Fibre 3.5 4.5 0.1Ash 6.0 5.0 3.5Carbohydrates (soluble) 14.0 2.5 0carbohydrates (insoluble) 19.5 15.0 0.3
Table 3. Amino Acid Compo s t t ion'' [26J
9
Amino Acid
ArginineHistidineIsoleucineLeucineLysineMethionineMethionine + cystinePhenylalanineThreonineTryptophanValine
Soy flour
7.02.44.27.76.41.02.24.73.61.74.4
bFAO reference protein
2.02.44.24.84.22.24.22.82.61.44.2
aIn, grams per 16 g N.
bFood and Agticulture Organization
10
(1) Analogues: products which are made to resemble another
product.
(2) Supplements: products which are made to meet a
deficiency. They are not added for textural purposes but
for their functional properties, especially to bind fat
and moisture.
(3) Extenders: to stretch out food which is available. This
is the most common use for extruded textured proteins.
They can be used with meat to reduce prices and, in some
cases, to improve quality.
It can be seen that in nutritional value the TVP is
comparable to meat. Soy protein is known to contain all of
the essential amino acids needed by the human body, except
it has a lower than desirable content of sulfur-containing
methionine (table 3). Hegarty and Ahn [27J proved the
nutritive value in soybeans by comparing soy-based meat
analog with ground beef.
Finally, soybean protein is abundant, commercially
available and inexpensive. It is the largest cash crop in
the United States, exceeding corn, wheat and cotton. It is
used extensively in the food industry. The price of the
texturized materials range from 27-45 cents per pound on a
dry basis, which after hydration translates into a 9-15
cents per pound meat replacement [25].
11
2.3 Mechanis. of Fiber For.ation
The mechanism of protein texturization during extrusion
cooking is not clearly understood. Many researchers have
reported that the extruder environment enhances the trans
formation of amorphous soy protein to fibrous microstruc
tures [14,31,59-63]. A fiber is defined as a body of matter
having a high ratio of length to lateral dimension and which
is principally composed of longitudinally oriented linear
molecules [28]. Fiber can be thought of as a result of
realignment of protein subunits that are disassambled due to
pressure and heat of the extruder environment. This re
alignment is done by the shearing action of the extruder
[29,30]. Smith emphasizes that the cooking extruder has the
ability to work dough to restructure and retexture the
proteins [31].
Thermal denaturation, which is the key parameter of
texturization, involves gelation and restructuring. The
process is irreversible and is described through a sequence
of steps. Figure 1 shows the formation of hydrogen bonds and
amide bonds between aligned molecules in a denatured state.
During heating, the ionic, disulfide, hydrogen bonds and van
der Waals' forces organizing and holding the native
globular proteins are interrupted and the hydrated proteins
begin to unfold. The relatively linear protein chains are
Native state
unfolding
12
AssociatingAmide bond
Figure 1. Mechanism of Protein Denaturation [23J
13
oriented through a shear environment, so that the reactive
sites on adjacent molecules can cross-link the protein to
achieve a fibrous texture [29,30,33].
Previous reports suggest that formation of fibers
involves the formation of certain types of intermolecular
peptide bonds (see section 2.1). The work of Cumming et al.
[34] describes the pressure and temperature influences on
the dissociation of soy protein into subunits which
subsequently become insolubilized and form high molecular
weight aggregate. On studying the formation of spun soy
fibers, Jenkins [35] demonstrated that the fibrous texture
of extruded soy protein can be improved by adding an
elemental sulfur-containing adjunct. It is believed that
molecular changes occur in the elongated curled protein
molecules by lateral reaction of the cystine bonds
{NH2 - CH- C02H)2 formed by amino acid groups between the
peptide chains, which are generally parallel and
overlapping. In 1976, Burgess and Stanley [36] suggested
that lIisopeptide ll crosslinking may playa role. They assumed
that crosslinking of protein chains occur through amide
bonds between free carboxyl and amino acid side groups of
the protein chains.
The energy for the endothermic denaturation process
consisting of breaking and forming of new bonds was
determined using differential scanning calorimetry to be
endothermic (90-100 KJ/KG) [37]. Sensible heat changes
occuring because of temperature rise in the
also be considered [37].
Qualitative changes in soy protein
temperature heating are shown in table 4.
14
product must
during high
Tab
le4.
Cha
nges
inC
har
acte
rist
ics
of
Soyb
ean
Pro
tein
at
Hig
hT
empe
ratu
reH
eati
ng[2
9J
Tem
pera
ture
of
hea
tin
g(O
C)
100
105
110
120
130
140
150
160
170
cro
ss-s
trli
ctu
reo
fsu
buni
tsin
tact
1it
tle
degr
aded
..1*
deg
rad
ed
----
solu
bil
ity
rap
idde
cr-e
ase-
s--s
low
incr
ease
..I-ra
pid
incre
ase--
bind
ing
forc
e(d
egre
eo
fag
gre
gat
e)ra
pid
incr
-eas
e-s-
-elo
wd
ecre
ase
.1-ra
pid
decre
ase--
expa
nsio
np
rop
erty
incr
ease
....ra
p;d
decrease--------
tex
ture
hard
frag
ile
..,..so
ftela
stic
•to.
lik
eso
l-------
......
01
Chapter 3
THEORY
When a bulk polymer is crystallized in the absence of
external forces, there is no preferred orientation of
crystallites or molecules. Orientation, which is defined as
the degree of alignment of polymer chains in a particular
direction, is greatly influenced by deformation and
ternperature gradients in the system. As the polymer becomes
oriented, the mechanical and physical properties improve
[28,38].
3.1 Melt Transfor.ation Extrusion Process (MTE)
The MTE is a thermoforming process. The objective is to
deform a polymer melt, and to align the chains in a common
direction or directions. This process has advantages over
other orientation processes, since orientation is induced in
the molten state. In the molten state the deformation can be
quite influential; organization at all dimensional levels
can be affected either directly or indirectly: the basic
molecules, the aggregate-crystallite, the crystalline
amorphous entity, the single crystal lamella, and the larger
1 7
aggregation, called spherulite [39]. The orientation due to
the deformation may be developed in glassy or amorphous
polymers, as well as in crystalline polymers. Since the
amorphous chains have not experienced crystallization, they
do not gain appreciable strength by orientation because they
fail by separation rather than by chain scission. In the
crystalline polymers, the crystallization is enhanced by
chain alignment.
3.1.1 Shear Stress and Flow Induced Crystallization
In the molten unoriented state, the linear molecules
are randomly coiled. Upon supercooling, the polymer tends to
crystallize and form spherulitic structures with no
macroscopic orientation (figure 2). The stacking of parallel
lamellae of the substructures produces a high local order
among the amorphous or disordered regions.
Flow induced crystallization and a shear field can
produce a high deformation. Mechanically, this causes the
forming lamellae to begin to slip from their originally
preferred alignment, such that the polymer axis becomes
a l i qned in the orienting direction. The extension due to
flow of the folded chains forms stacks of parallel lamellae
that can be either along or against the lamellae axis [40].
Figure 3 shows this behavior in a crystalline polymer.
Sphtrut,'icchoins folded atriQht anQ~ tomain alis
18
Defect, infibritt
Single .>crystalnucleus
AmorphousInter - spherulj,icmaterial
Amorphousintff- fibril tormaterial
Spheruli'e
Figure 2.
( a )
( b )
Structure of Spherulite [28J
~~---_.
Figure 3. Suggested Model for Fiber Formation(a) By unfolding of molecules from more
than one lamella,(b) By gradual chain-tilting, slip,
breaking off blocks of folded chains
19
Upon approaching the entrance region of the die, the
velocity distribution of a molten polymeric material changes
to a "wine glass stem shape" (figure 4). The flow
streamlines converge rapidly inducing an elongational effect
of the previously random coiled polymer chain and giving a
higher degree of orientation [41-42]. The rate of uncoiling
of the polymer chains at the converging section depends on
the deformation ratio and the type of polymer processed
[43,44,48].
Previous work using plastics on the MTE process
describes the four important processing conditions which
contribute to the amount of orientation in the extrudate
[43,44,46-52]:
(1) die design and deformation ratio
(2) screw or line speed
(3) operating pressure
(4) temperature profile
The MTE process has been used with dies having reduction
ratios from 2:1 to 16:1, with half angles ranging from 10°
to 26°, and die geometries that deform the melt in either
uniaxial or biaxial directions. Furthermore, fiber, ribbon
and more complex dies have been used along with this process
[44,46-52]. Extrusion rates, controlled partially by screw
speed, govern the level of deformation on the polymer melt,
as well as the orientation.
! , : 1 n (= 0 n f 0 rm d t ion
z
Flow streamlines
Crystal growth tr ontand i sot he rma 1 line
20
Figure 4. Elongational Flow in the "Wine Glass Stem"Region of a Converging Die
21
3.1.2 Pressure Effect on Crystallization
As proposed by Brown [53], the development of the
extended chain crystals may be related to the formation of
the nematic Illiquid crystals." A nematic structure consists
of a parallel stacking of rods with relatively perfect
internal structure, but not necessarily matched from end to
end (figure 5). Collier postulated that a liquid crystalline
form could occur in the materials studied under critical
temperature, pressure, and field conditions [2]. This
behavior of different crystalline structures (polymorphism)
is not limited to the simpler polymers but is also observed
in proteins and synthetic polypeptides [54,55]. In the case
of synthetic polymers, the working pressure for MTE ranges
from 2000 to 8000 psi, which is 1/4-1/5 that of a solid
state extrusion [56].
Thermal properties
Earlier observations of oriented (extended) polymer
have shown a higher melting point than that of a random melt
(quiescent) [43.44,46-52]. In terms of entropy change,
( 2 )
The melting points are,
( 3 )
(
( D
y
)-'2X
22
Figure 5. Nematic Liquid Crystalline Form
23
( 4 )
where subscript f stands for fusion, q for quiescent, and ex
for extended.
As,
( 5 )
then,
Tm / Tm =6.5 / ~Sffex q q ex
from ( 2 ) ,
Tm / Tmq > 1 or T > Tmex mex q
Tm = Tm - Tmex q
( 6 )
( 7 )
( 8 )
Hence, the melting point of polymeric material is directly
related to its degree of orientation.
3.2 Extrusion Cooking
Extrusion, in general, refers to the shaping of the
products to the desired size and consistency by forcing the
material through a die under a high pressure. Extrusion has
long been used in the food industry in the making of special
shapes of food products (e.g. macaroni, bacon bits).
Previous researchers have shown that the extrusion process
ca n produce mea t 1i ke fi ber s [14,31,57-61]. These repor ts
provide the "s t a t e of the a r t " of protein texturization by
using the extruder.
The basic patents of soy protein extrusion are those of
Atkinson [62] and Jenkins [35]. The newer patents, which
were an improvement over the prior patent, did not use a die
on the extruder and therefore had a lower pressure drop
(below 200 - 500 psi); the resultant product's characteris
tics were less spongy, less hydrated, and more fibrous
[57-59].
Food extrusion owes much of its design and theory to
plastic science [37,42]. However, it should be noted that
there are differences between plastics as 'chemical',
artificial polymers and protein as "b t opol yme r s ! , natural
polymers. Zuilichem [63] explained these differences as:
1. Biopolymers shows no spontaneous melting-temperature or
trajectory but simply need a certain amount of shear to
25
plasticize the protein-water mix.
2. The biopolymer is highly sensitive for a long time span
of exposure to heat and pressure.
3. It is important that some water be present during
extrusion to assure a continuous working condition of an
extruder.
The main components of a food extruder are the same as
those of a thermoplastic extruder. They are: feeder,
compression screw, barrel, d t e Ls ) , and heating system. In
this process, moistened products are plasticized in a tube
by a combination of heat, pressure, and mechanical shear.
Figure 8 shows the basic process in the food extruder
barrel, which i s divided into 3 stages: mixing and
compressing, heating and cooking.
DRIVE, GEARRE DUCER aTHRUST BEARING
\
FEEDHOPPER
FEED
SECTION
SCREW WITHINCREASING
ROOT DIAMETER
COOLINGWATERJACKET
THERMOCOUPLES
COMPRESSION METERING
SECTION SECTION
PRESSURETRANSDUCER
/ DIE
DISCHARGETHERMOCOUPLE
BREAKERPLATE
BARREL WITHHARDENED LINER
Figure 6. Cross Section of a typical food extruder [39]
26
(1) Mixing and Co.pressing (feed zone)
The moi stened material enters the extruder through the
feed zone. The relatively free-flowing granular particles of
the meal cause a turbulent like pattern in the intake
section of the extruder. This flow insures intimate contact
of protein with water with very little internal shear of
food. Then the screw further compresses and mixes the
product. No cooking is desired in this zone [64].
(2) Heating (transition zone)
The second zone continues the mixing action, and
concomitantly imparts heat into the mixture due to shearing
action of the screw. This heat is used by the proteinaceous
material to coagulate and polymerize. This transition from
solid to a fluid is associated with a set of chemical
reaction called 'cooking'.
(3) Cooking (.etering section)
The meaning of cooking here is the conversion and/or
reaction of the major food constituents - carbohydrate, fat
protein, and water. Two types of cooking reactions which
occur with food biopolymers are protein denaturation
(section 2.2) and starch gelatinization. In these reactions,
water and food materials themselves interact to create new,
altered forms which have a distinctly different rheological
behavior. This cooking process is time and temperature
the variables of extrusion processing
27
dependent, which probably changes with the concentration and
quantities of the chemical species present and the shear
environment. Food extrusion results in the chemical
alteration of the feed ingredients through the cooking and
texturizing process and in this respect is significantly
different from the melting processes, which occur during the
extrusion of thermoplastic resin. Thus, the application of
the words 'melt' or 'melting' is a misuse [39J.
Most of the cooking is done in this critical zone. The
cooking is mainly done by externally supplied and viscous
shear heat as the material is conveyed through the barrel to
the die. The highly turbulent flow pattern is transformed
into a laminar flow to minimize back flow across the protein
strands. At this stage the materials are simultaneously
oriented and coagulated in the direction of the chamber.
During this whole process, the viscocity and physical
properties of the dough can differ drastically. Information
about this is very limited. According to Briskey [65] and
Hermansson [66], the viscosity of the system changes with
the degree of protein hydration.
Therefore,
conditions are,
1. temperature profile
2. screw speed/line speed
3. design of die(s)
28
4. moisture
5. pressure profile, and
6. residence time
3.3 Characteristics of textured protein products
A variety of tests have been used to characterize the
texture and other properties of textured protein products.
These tests are used to determine the effects of varying
extrusion conditions on product characteristics, and to
maintain quality standards for production runs. Comparison
of results from different investigations is difficult,
because no standard set of tests is used [37J.
Only two types of tests were possible in our
laboratory: bulk density and water absorption (hydration
value). Bulk density gives the degree of expansion of the
extruded dried products, while water absorption gives the
degree of po r o s i ty of the products' textures. Water
absorption is an important functional property of textured
protein products as the products are used after rehydration.
This value gives an indication of the extrudate maximum
absorption and retention capabilities. Hydration conditions
vary in different laboratories.
29
3.4 Response Surface Analysis (RSA)
It is convenient to visualize geometrically the
relation between response and the various factor levels. RSA
method represents the response by assuming that when k
factors ( or independent variables, exist in an
experiment, the response (or dependent variables) will be a
function of the levels at which these factors are combined
[61].
( 10 )
The function ~ is called the response function.
The response surface is represented by a polynomial.
For the case of three variables, a quadratic polynomial was
proven adequate to fit the data [3-5]. The model is,
( 11 )
The above equation takes into account variations due to
first and second degree as
i nt e'r act ion s •
well as those due to
Response of the independent variables in a certain
region is represented by contours. These surface contours
are obtained by making one variable equal to a constant
30
value and then solving the fitted equation as a quadratic
equation in the other two.
The application of this method in food industry is
quite popular [3,45,68].
Chapter 4
DESCRIPTION OF EQUIPMENT AND MATERIAL
A. Extruder
A laboratory single-screw extruder, C.W.
Brabender, Model 200, had the following
specifications: barrel diameter - 0.75 11; LID 20:1;
feed hopper gravity feed; heating 2 zone
electric heaters, independently controlled by 800
watt heaters monitored by two West Model JPC
on-off proportional controllers; drive unit
variable speed motor assembly, equipped with a
tachometer, and capable of controlling screw speed
from 0-200 RPM. The discharge pressure was
indicated on a West Model 1586 pressure indicator
with a range of a to 10,000 psi. The motor speed
was controlled by a Fincor 2400 MKII DC Motor
Controller, manufactured by INCOM, International
Inc.
B. Extruder Screw
The screw used was made of 4140 chrome alloy with
a standard compression ratio of 2:1. It had 20
flights with increasing screw root diameter from
0.475" to 0.605 11 with a 0.608" axial channel width
32
and a 0.007 11 flight clearance. Angle of the
helical screw was 25°.
c. A Melt Conditioning Pipe
as a connection between the
(medium pressure-lO,OOO psi)
insidediameter and 0.687"
A 15 11 length pipe
barrel and the die •
with 111 outside
diameter was used
..;
D. Extruder Dies
The dies were made of 304 stainless steel:
(a) A split die with a uniaxial deformation ratio
of 6:1 was used. The die opening consisted of
a slit 1/16 11 thick and 1/2 11 wide which
produced a tape or ribbon like extrudate.
(b) A fiber die with a circular opening of 0.020"
diameter and 111 length was also used. This die
was fitted to a holder and produced a
string-like extrudate.
Each of the above dies produced a vertical,
downward extrusion and were heated with fitted 600
watt heaters controlled automatically from the
control board. Figures 7 - 10 show the designs,
dimensions, and views of the dies.
o•
-1/16" 1/2"J
L--- -2 1/4"-----3/16"
---------3 1/2 ..-------......
33
Figure 7 . Schematic Diagram for(A) Side view, and (B)
the Uniaxial-ribbonTop view
Die
34
-CD~,
\9I
•"10J QJ
..c:-4->
S-o4-
Ertj
S-O)
rtj
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E S-QJ Q)
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co
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lJ......
4.
..........t:-:-:-:·:-:-:-:·............................t::::::::::::::::~:.
4 8 /~ 1--.II
~
f ",...
='""-....
::::::::::::::::~
-+-- 9 /1.--+It
r ~
r~:::::::::::::::
f- ~::::::::::::~
=- =N .. •"' " ",... ....
PI)
r- ~:::::::::::::::i ,.... IL
r'i"••••••, ••••••••
1:::::::::::::::::Il
.~
--It)
Figure 9. Photograph of Uniaxial Die Halves
Figure 10. Photograph of Fiber Die Pieces
35
36
E. Controllers
Two of the three Gardsman temperature control
units manufactured by West Instrument Corporation
were used to control temperatures in the barrel.
They had a range of Q-800oF (425°C). The tem
peratures in the piping and the dies were
controlled with two Love Model 52 controllers
mounted on the control board. They had a range up
to 400 oC. Temperatures and pressures in the barrel
and the die were sensed by Dynisco strain gauges,
r~1 0 del TPT43 2A-I QM- 6 / 18 , and measur e d byaWest
Model 15-86 and a Dynisco Model ER 478Al pressure
gauges.
F. Optical Microscope
A Wild M5A Stereomicroscope was used for
texture observations i n the 1abora tory. The
overall magnification range was 1.4X to 20QX,
depending on the optical combination.
Photomicrographs of the structure were taken by
MPS15/11 Semiphotomat (632.8 mm) assembled on the
M5A Stereomicroscope using a 35 mm film (ASA
400/DIN 27).
G. Scanning Electron Microscope (SEM)
A Hitachi Model HHS-2R Scanning Electron
37
Microscope was used to photograph the sample on
positive/negative black and white Polaroid film,
type 665 (ASA 75/DIN 20). The SEM is capable of
viewing three-dimensional structures over a range
of 20-280,000 magnification.
H. Sputter Coater
Prior to SEM examination, the samples were
coated with gold or gold/palladium deposition in a
Hummer V sputter coater, manufactured by Technics.
I. Differential Scanning Calorimeter
A Perkin-Elmer, Model DSC-1B differential
scanning calorimeter was used to detect the
melting point of soy protein. This equipment was
connected to a Perkin-Elmer, Model 56 chart
recorder to plot the rate of heat input versus
temperature.
J. Soybean
Defatted Soybean protein concentrate, PROCON
2000, was obtained from A.E. Staley, Mfg. Co.,
Decatur, 11. It contained 70% protein on a dry
solid basis and 5-7% moisture.
Tacla
•••t
.r
Zon
l4
Zo
ne
3
r--------
Pr•
••ur
.-T.
.p
.rat
urt
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auae
~
Zon
e2
Zon
f1
o
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ar
r•
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on
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.r
Z0
ne
1-D
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Fig
ure
11
.S
chem
atic
Dia
gram
for
the
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tru
sio
nP
roce
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ith
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erZ
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39
Chapter 5
EXPERIMENTAL PROCEDURE
All the samples tested in this investigation were
prepared by extruding premoist soybean flour in a C.W.
Brabender laboratory extruder, Model 200. To complete the
screw assembly, a conditioner zone (18" spacer) was placed
between the die plate and the barrel, which provided
additional volume after extruder screw discharge. Previous
workers proved that the conditioning zone improved pressure
uniformity behind the die plate, increased the residence
time of the material in the extruder, and improved
crystallization [51,52].
All compression fittings in the assembly line were
torqued to 75 ft-lb (figures 11 and 12). Prior to setting
up, the die channels were cleaned from old polymer by
sanding with 600 grit sandpaper. The ribbon die halves were
assembled with six 0.25" X 2.5 11 grade eight socket head cap
screws, which then were torqued to 90 ft-lb. All
t he r mo coupl e s , transducers were tightened to prevent any
leaking during operation.
Independent variables selected for the process were
temperature, feed moisture and screw speed. The selection of
these critical variables were based on findings reported by
previous researchers and through preliminary experimentation
41
[14,31,59-63]. The dependent variables are pressure profile
and line speed.
6.1 Preliminary experi.entation
The first objective was to find the best temperature
profile and processing conditions. The extrusion assembly
was divided into 5 temperature zones: I and II - the barrel,
III and IV - the conditioner zone, and V - the die (figure
11). Through preliminary experimentation, it was necessary
to force feed the material through the hopper. The premoist
soybean was ground by the screw and pushed back into the
feed hopper. Because of the considerable amount of steam
generated, the soybean developed a tacky consistency and
clogged the feed inlet. This effect was reduced by not
heating the section nearest to the hopper. If this section
were heated, the steam would be absorbed by the incoming soy
material. The steam caused caking and made smooth operation
impossible.
The temperature settings for the assembly were
determined by careful observation of extrudate quality. A
decreasing temperature distribution toward the die was a
better choice than that of an increasing temperature
distribution. The former case had two advantages:
42
(a) Most of the cooking was done in the barrel zone. A
decreasing temperature distribution prevented de
gradation of the material.
(b) The material did not extrude at too high a
temperature in the die. Excessive expansion caused
by flashing steam could destroy or seriously limit
the formation of the fibrous structure, however, a
certain amount of expansion of the product was also
important in order to obtain a fibrous structure.
In the past, a steep temperature gradi ent was appl ied
to enhance and freeze the highly oriented extrudate
[48,51,52]. This was usually done by immersing the tip of
the die in a water bath as a cooling medium, which also
caused the pressure to build up. In this study, the effects
of the die land temperature gradient were not observed to
occur.
The die temperature was heated to SOOC, since a lower
temperature caused the material to stop flowing out of the
die passage. Too high a temperature (100°C) at the die made
the product emit separated bursts of burnt individual
pieces. It appeared that some pieces would stick in the die
nozzle until the pressure built up sufficiently to dislodge
them. The material near the end of the die expanded rapidly,
producing a rapid outflowing of material which fragmented
into individual pieces. This product was unassayable.
43
Once particular processing temperatures were set, a
series of experiments with the same temperature setting were
conducted. This reduced excessive use of raw material during
the transition periods to a new temperature settings.
Since the extruder was not self emptying, too little
moisture, too high a temperature, and too high a compression
ratio were all avoided because any of these would cause the
materials remaining in the barrel to harden and lock the
screw [69]. A blocked extruder, due to overheating or high
frictional drag of the product, costs a considerable amount
of maintenance time for dismantling, cleaning and repair.
An experimental design was chosen with three levels of
temperature, three levels of moisture and four levels of
screw speed to allow estimation of second order effects in
the empirical statistical model for three independent
variables (table 5).
Tab
le5.
Exp
erim
enta
lP
atte
rno
fP
roce
ssin
gC
ondi
tion
Cod
es
Pro
cess
ing
tem
pera
ture
pro
file
,Zo
nes
II-
III
-IV
(OC)
M0
istu
re
wlo 30 35 40
140
-11
590
RP
M
4060
8010
0
Al
A2A3
A4
B182
8384
C1C2
C3C4
150
-12
5-
100
RP
~1
4060
8010
0
0102
0304
E1E2
E3E4
F1F2
F3F4
160
-13
5-
110
RP
M
4060
8010
0
G1G2
G3G4
HIH2
H3H4
II12
1314
Not
e:Th
ete
mpe
ratu
reat
zone
sI
and
Vw
ere
unhe
ated
and
50°C
,re
spec
tiv
ely
~ +::at
45
6.2 Experi.entation
DRY a WET SOLID - LIQUID........
INGREDIENTS BLENDER
AFTERDRYER .... EXTRUDER. .-.... ,
Figure 13. Simplified extrusion flow sheet
Figure 13 shows a simplified flowsheet. Moisture was
added to the soybean meal prior to extrusion because the
residual moisture content of the meal after oil extraction
is normally very low (5-7 weight percent or w/o) [69]. As
the present design did not allow direct water addition in
the extruder, a food processor was used for moistening the
powder. In order to have a uniform product, a food processor
was used to mix the dry flour with water. Distilled water
was added slowly along with the continuous mixing and
breaking action of the steel blade, so that it maintained a
free fl owi ng movement of powder to prevent the development
of large aggregates. Water addition was accomplished in 3-5
46
minutes and mixing ceased after an additional 3 minutes.
Batch sizes were normally about 300 grams of dry blend.
Once the temperature settings on the extrusion system
were reached, the motor was turned on and the screw speed
was adjusted to achieve the desired tachometer setting. Then
the hopper was fed with premo;stened soybean meal. In order
to achieve a continuous feeding, the mix was hand-fed to the
extruder hopper. An excessive amount of mix in the hopper
prevented free flow of the material into the extruder
because of caking or bridging of ingredients in the feed
hopper.
Sufficient time (20-30 minutes) was allowed in order to
have a steady state system. Estimation of the steady state
was based on the temperature and pressure readings. After
enough material at each shear rate had been produced (.!.15
feet), the screw speed was changed to another desired shear
rate. Elapsed time was allowed for the transition period (20
minutes).
Data collected consisted of the steady state values of
temperatures in all zones in degree Celsius, pressure at the
exit of the barrel, pressure at the die in psi, and
extrusion rate in in/min. Table 5 shows the variations of
variables selected.
Extruded samples were collected, placed in sealed
plastic bags, labeled with the extruder run codes and
refrigerated.
47
The second objective was to analyze the effect of using
higher pressure conditioning. Higher pressure drop at the
die was attempted. This was done by replacing the ribbon die
with a fiber die. Temperature profile chosen was unheated
160-135-10Q-50oC and screw speed of 40, 60, 80 and 100 rpm.
c. Speci.en Testings
All the samples were photographed and tested for
moisture absorption capacity, bulk density and thickness. It
was necessary to examine the specimens as soon as possible
because the extrudates will not remain fresh due to
microbial and enzyme action. Under refrigerated conditions
the material lasted only for 2-3 weeks.
Water absorption capacity was evaluated by soaking 50
grams of extrudate segments in a beaker filled with 200 ml
water. After 15 minutes of rehydration, the excess water was
removed by draining with a tea strainer for 15 seconds.
Afterwards, the sample was reweighed. The percent water
absorption was calculated as the percentage weight increased
based on the dry weight.
Bulk density was determined by weighing 12-in long
extrudate. The volume was obtained by multiplying the length
by average width and thickness. Average degree of puffing
was 40.8S; puffing is defined as the degree of extrudate's
into two
Electron
studies
because
divided
Scanning
microscopic
extruded,
48
volume expansion due to pressure drop and flashing of the
water vapor. The product density was obtained by dividing
the weight by the calculated volume.
Microscopic Examinations were
stages, optical microscopic and
f4 i c r 0 9 rap h s (S EM). Sam p1e s for 0 ptic a 1
were taken immediately after they were
they were still moist and easy to layer.
Preparing samples for SEM was more complicated than for
the optical microscope. However, only a small area of the
sample can be viewed at one time. The samples obtained
during the extrusion were frozen in liquid nitrogen. Samples
for SEM were placed onto a specimen stub covered with
double-coated cellulose adhesive tape. The area around the
specimen was coated with a small streak of silver conductive
paint in order to minimize charge build-up from the primary
electron beam. Afterwards, the specimens were coated with
gold-palladium (60:40) in a sputter coater. The coated
specimens were examined in a Hitachi scanning electron
microscope, Model HHS-2R. The photographs were taken on
positive/negative black and white Polaroid film (ASA 75/DIN
20) •
Differential Scanning Calorimeter (OSe). Samples
were cut into thin pieces and weighed to the nearest tenth
of a milligram. They weighed approximately 5-15 milligrams.
Then they were sealed into specially designed aluminum pans
49
supplied by Perkin-Elmer and placed on the Perkin-Elmer DSC
unit. The instrument was calibrated with a standard heavy
Indium sample (163.S oC melting point) at 20°C/min and a full
scale deflection of eight millicalories. The recorder was
set at a full scale range of five millivolts and the chart
speed was set at 40 rom/min.
Statistical Design. The data were analyzed by means
of a stepwise multiple regression. The analyses were
performed using the extrudate characteristics as dependent
variable versus the processing temperature, screw speed, and
moisture. All possible subsets of the regression were
performed using the SAS package [70]. Then, response surface
plots were made from the derived regression equations.
Chapter 6
RESULTS
A series of experiments was conducted according to the
above design. The intent was to investigate the effect of
independent process variables upon dependent variables. The
protein concentrates used on all runs were assumed to
contain 5% moisture prior to any water addition.
The results of response surface analysis are tabulated
in tables 11 and 12 in Appendix C. The response surface
plots include all the experimental design data and the
predicted data. These plots illustrate the contour of the
dependent variable against two of the independent variables,
while setting one of the variables constant. Response
analysis usually predicts the area with optimum response,
e.g. highest output, highest absorption rates, etc. The
shape of the optimum, the "center of the sy s t e ra'", can be a
maximum, minimum, or a mix of the two, a "saddle point". The
results of the dependent variables of this study show a
"saddle po i nt " which implies the existence of two distinct
regions of maximum yield a two peak system (figures 23, 29,
and 32). The area of the two peak system means that there
are two maximum peaks in the system. Sometimes the center of
this area is found outside the experimental design. The
surface in this region of the experiments represents either
51
an inclined ridge or an inclined trough.
The effects of screw speed on extrusion rate or
volumetric flow rate was primarily a function of screw
speed. Figures 14 and 15 show the trends at different
moisture contents and process t emp e r a t ur e s , respectively.
Moisture content effects were more significant than that of
processing temperature. Higher moisture content produced
caking of the material t reducing output rate. Process
temperature effects were more dramatic at lower screw speed
and leveled off at higher screw speed. Effects of all the
three processing variables are represented by the response
surface plots in figures 16 and 17. For e xamp l e , in figure
16, the effect of screw speed and moisture on the extrusion
rate at a constant temperature is represented by five
symbols. The darkest symbols, at the upper left of the
figure with a value of 62.18 to 69.53 inches per mi nut e ,
represents the highest value range of extrusion rate shown
in this figure. The value occured at a screw speed of 90 to
100 RPM at a moisture content of 20 to 22.5 weight percent.
Decreasing extrusion rates are represented by the other
symbols along contour lines, at roughly 15 inches per minute
interval.
Figures 18 and 19 depict the pressure profile at the
die versus screw speeds. This pressure was an indication of
how much energy was required to force the material out of
the die orifice. To overcome high frictional forces in the
52
20 40 80 80SCREW SPEED (Rpm)
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·1 X ++++.++++++++++ •••••••••••••••••••••••+ +++++++++++++++ ••••••••••••• ~ ••••••••••-----+------+------+------+------+------.----------
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Figure 16. The Effect of Screw Speed and Moisture on theExtrusion Rate at a Constant Processing Temperatureof 150-125-100-50°C.
55
CONl"OUR PLOT OF TEMPERATURE (e) AND MOISTtfAE. CONTeNT (W/O)CONTOURS ARe E>eTRlIsrON RATES (IN/MIN)
CONTOUR PLOT a~ Xl*~3
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Figure 17. The Effect of Processing Temperature and Moistureon Extrusion Rate at a Constant Screw Speed of70 RPM.
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58
die land of the fiber die, pressure was increased to one and
a half times that of the ribbon die (figure 20). Pressure
variance was graphically represented with a 90% confidence
limit. Response surface plots for the die pressure are on
figure 21-23.
A differential scanning calorimeter was used to detect
the melting point and heat of fusion. The DSC was
standardized using an Indium sample. The peak melting point
occured at 430 oK, which depressed the actual melting point
(163.S oC) by 4% (figure 24).
Figure 25 shows the typical DSC scanning for the
extruded protein product. Mel ting point did not occur and
the decreasing curve indicated that the tested material
experienced an endothermic reaction. This behavior will be
further discussed in the next chapter.
Figures 26-28 represent the correlations of extrusion
parameters with product absorptions, or water retention
value. The increase in water uptake implies that more water
penetrated the structure. This is an important value because
commercial texturized vegetable protein products are
rehydrated prior to use, and rehydration characteristics of
the cooked food is also important for digestion.
Furthermore, the extrusion processing conditions influenced
the protein to restructure and reduce its solubility.
Bulk density of the dried extruded soy protein product
indicated the degree of product expansion. This exothermic
1600
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XXXXXX 1424.2624 ~lS0.6:~Jqg~ee~q 21~J.620Q 287f1.9794
~~JlC4"~ 2a7~.97q4 3240.t58';
Figure 2 1. The Effect of Screw Speed and Moisture on theDie Pressure at a.Constant Processing Temperatureof 152.8°C (Zone II ~
61
CONTOUP PLOT CF Tp:,JPf':"pATUnE r r j VS. r··OT~TlJPr CCNTE~~T ('1J/O)cnNTPUn~ ARF OYE PRESSUR~S (PSI~)
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Figure 22. The Effect of Temperature and Moisture on theDie Pressure at a Constant Screw Speed of 45 RPM
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Figure 23. The Effect of Temperature and Screw Speed onthe Die Pressure at a Constant Moisture Contentof 40 w/o.
dqdt
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Figure 24. DSC Endotherm for Indium
63
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67
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Figu re 2'8. The Effect of Screw Speed and Moisture on the ProductAbso~ption at a Constant Processing Temperature of150°C (zone II)
68
expansion was caused by the sudden release from elevated
pressure at the die to atmospheric pressure and the flashing
of the water vapor. Figure 29 shows the effect of
temperature and the screw speed at a constant) initial
moisture content of 30 w/o. The result indicated an area
near a minimum; an increase in screw speed at low
temperature produced a high and low bulk density.
The relation of temperature and moisture on the bulk
density is illustrated in figure 30. Increased temperature
and moisture content increased the bulk density, because
high temperature produced the flashing of water vapor, which
increased the expansion.
As previously mentioned, it was desirable to maintain a
low enough temperature at the die to prevent the product
from overheating, yet high enough to enable sufficient heat
to be added to cause proper fiber formation. The die
temperature was set at SOoC. The actual temperature was
greater; the dies used were not equipped with a cooling
system allowing an increase in temperature due to mechanical
friction and chemical reaction. The actual temperature of
the die was taken as a dependent variable of the product
temperature. Response surface analysis plots are shown in
figures 31-33.
69
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20.J 2~.5 2 7 . 0 3J.5 34.0 3 7 . 5
MOISTU~E
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g-Ase€e ~S.J~652 - 1 0 .) • 40"" 1 q
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Figure 32. The Effect of Temperature and Moisture on theProduct Temperature at a Constant Screw Speed of135 RPM
73
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20.0 23.5 27.) 30.5 34.0 37.5
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Figure 33. The Effect of Screw Speed and Moisture on the ProductTemperature at a Constant Processing Temperature of1400 C (Zone I I )
Chapter 7
DISCUSSION
The results of SEM and the analysis of variance prove
that it was possible to produce different product
characteristics. Texture, which is a product of va r t ab l e s '
interaction, can be manipulated by controlling the process
variables.
As expected, extrusion rate was primarily a function of
screw speed. Increased screw speed increased the quantity of
material passing through the die. Analysis of variance shows
that moisture and temperature also had a very significant
effect (P~O.Ol-table 6). This trend was probably related to
flow characteristics of the feed material. Increased dough
moisture resulted in lower bulk density and greater
percentage water absorption. Increased moisture content
produced a certain degree of swelling (caking) of protein
molecules, which caused the decrease in flow rate. An
increased temperature enhanced the swelling effect. It was
not known to what extent water absorption could be taken as
a measure of the degree of swelling of protein molecules
[65,66J.
Extrusion -rate at high screw speed was also a result of
pressure gradient. The pressure profile indicated the
location of maximum pressure, which was greatly dependent on
Tab
le6
Eff
ects
of
Var
iab
les
onE
xtr
ud
ate
Ch
ara
cte
rist
ics
LEV
ELS
OFSI
GN
IFIC
AN
CE
VA
RIA
BLE
SE
xtr
usi
on
Die
Bul
kA
bso
rp-
Pro
du
ctRa
teP
ress
ure
Den
sity
tio
nT
emp
erat
ure
Tem
per
atu
re~
0.0
1~
0.0
1NS
NS~
0.0
5
Scr
ewsp
eed
~0
.01
~0
.05
NS~
0.0
1~
0.0
1
Mo
istu
re~
0.0
1~
0.0
1NS
~0
.05
NS
Reg
ress
ion
88
.3%
89
.8%
14
.0%
53
.89
%74
.26%
(P~O.Ol)
(P~O.Ol)
(NS
)(P
-,O
.Ol)
(P~O.Ol)
.........
(Jl
76
operating conditions, such as barrel temperature. flow rate,
frequency of screw rotation, screw geometry, and moisture
level [71J. In general, minimum pressure drop across the
ribbon die orifice ranged from 300 to 500 psi, which was
almost twice as much as the conventional method. The
pressure trend was difficult to establish. Increased screw
speed did not always increase pressure. This variable was
related to the viscocity of the molten material in the die
zone. As temperature and moisture increased, the viscocity
decreased. and the less viscous material flowed out faster,
so that pressure decreased.
The fiber die runs had a small die orifice (0.020 11) and
generated a higher pressure range (1000-1600 psi). This
indicated a higher friction in the land of the die. Too high
a die pressure was very significant for fiber formation. An
optical micrograph of the extrudate at too high a pressure
showed no fiber formation; the product was tightly
compacted, very dense and had very little rehydration value
(figure 34). After the die was disassembled, fibrous
structures were found in the reservoir section. It was
apparent that the high pressure, which produced high shear
strain and back flow, disrupted the fibers.
Fiber formation began in the screw channel. The shear
strain in the screw provided a good environment to align the
protein molecules during their flow. Therefore, increased
shear rate increased the possibility for chemical reaction
Figure 34. Optical Micrograph of Fiber Die Runs, 12X
77
Figure 35. Scanning Electron Micrograph of Run.F4 shows
Porous Structure, 700X
78
and produced texturization. Fibers were further formed and
aligned in each consecutive heating section. The final
texture of the extrudate was a result of all these
reactions. The final extrudate seemed to remember the
formation in the screw section by showing interlaced fibers.
Analysis of variance gave an indication that all
process variables, temperature, screw speed and moisture had
a very significant effect on the die pressure (table 6).
The result of Differential Scanning Calorimetry showed
an e ndo t her a i c curve without a peak. This was expected
because soy protein undergoes an irreversible reaction and
behaved more like a dough. DSC analysis might not be an
appropriate method for characterizing soy protein
texturization. Furthermore, layers of the fibers were easily
separated along the direction of orientation. High
temperature produced a lateral fissuring to such an extent
tha t they had a weak 1i nk , Probabl s , the soy protei n wa s
only a semicrystalline or amorphous polymer.
Product absorption showed a decrease with higher feed
moisture, and an increase with higher process temperature
(figure 27). At lower temperature the product was uncooked,
tightly compacted, and very dense. There was very little
penetration of water during rehydration. As the product
temperature increased, the product was more structured
(fibrous), cooked and spongy, because upon exiting from the
die, the product expanded, becoming more porous and less
79
dense. Figure 35 reflects the microstructure which shows
larger cavities and smaller filaments. The microstructure
illustrates that some of the tight fibrillar arrangement
observed at the die were lost due to sudden expansion. The
more spongelike the structure the more water will be imbibed
in the product.
~igh screw speed not only reduced the heat exposure the
protein received but also produced interlaced fibers. This
structure tended to trap the expanding steam within the
product when it left the die. This also elevated the
v;scocity of the dough, and reduced product expansion as it
left the extruder. Thus, it was less porous.
Table 6 shows that the absorption value was mostly
governed by screw speed and moisture content.
During the rehydration period, the protein did not
disintegrate or lose its structure and shape. This proved
that the protein denatured or changed its physical-chemical
and functional properties due to heat processing. The
extrusion process caused most of the water soluble soybean
protein to break into subunits and/or become insoluble.
Thus, heat and moisture caused progressive insolubility of
the protein in soybean meal [34,72]. A high pressure gave
higher extrusion rates and, in effect, increased the rate of
shear, which resulted in better cohesion and better
retention of structure on rehydration. Work done by Taranto
et ale showed that fibers formed at higher screw speed
80
extrusion are stronger [5].
Theoretically, the passage from die to atmospheric
pressure is characterized by "puffing", which controls the
product bulk density. This is mainly due to flashing-off
superheated vapor and to the release of normal stresses. As
the material cools, it sets into a definite porous structure
with a slight size reduction.
There is no significant correlation between the
variables on the bulk density. Perhaps, it is related more
to the die temperature. Even though density changed quite
markedly over the range of temperature, width and thickness
remained constant (average degree of puffing was 40%). This
suggests that all physical changes occured prior to final
extrusion.
Temperature increases were not only found in die
temperature but also in the heating zones (figure 36). It
appeared that there were substantial heat sources other than
the heating element. The increased temperature came from the
mechanical work and frictional heat in the screw section and
in the die section, where the shearing action existed; the
dough temperature might be even higher than the desired
temperature.
Exceeding a floor temperature was necessary to provide
sufficient energy for denaturation. The thermal denaturation
of aligned protein molecules to form cross-link layers is an
irreversible endothermic chemical reaction in the extruder
81
>!J L&.I
/1 z0
: I N
: /I
I >II
LIJ
Iz0
Vl
:QJ
/ N c:0
/N. rn
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: I+Jct1:', QJ- :r:-
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LIJ S-
Z QJ
...: /4-
0 C+-
N .r-
/ -0
:
/.....,
.. ~
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/'r-
e: 4-0
"- 0-.- I S-...- , 0-
"C " &1.1 QJ
0 S-
U • Z :::3
0 0+oJ., . ct1
65.
N S-
CI c: '\"OJ
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;: .a ... E
• y-. Q).. ~ ..D ~.,ii Ii:en C'l
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IVlVl
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82
behaving as a reactor. Figure 37 shows the dependency of
residence time versus screw speed. Increasing residence time
would provide an environment giving a greater degree of
thermal denaturation. Zuilichem noted that residence time
distribution controlled the degree of mixing and the degree
of uniformity of the strain exerted on the dough [63]. In
the MTE system, residence time was increased by the addition
of the conditioner zone, this was about 5-10 minutes longer
than the conventional extrusion.
Extrudates obtained at lower than 40 RPM and higher
than 100 RPM demonstrated the erratic behavior of the
extruder. This study indicated that shear values decreased
as the initial moisture content increased, but above 40%
there was virtually no influence of moisture on texture.
Also, at lower moisture content (less than 20%), no
interaction was observed between shear value and process
temperature.
Observation of the physical appearance of the products
indicated that as temperature increased, orientation and
fiberization increased. The scanning electron micrographs
revealed alterations in physical structure during
processing. Figure 38 shows the appearance of fibers among
unstructured globular protein of run Gl (zone II-160°C, 30%
moisture, 40 RPM) at lOOOx magnification. Figure 39 shows
the exellent fibrous structure of run F3 (zone II-150°, 40%
moisture, 80 RPM) at 150x magnification. An isolated fiber
16 83
8
..l.
99...
•.•...•.....•.•.,
•••••~.•.o .•..•.- •-.••
~t
-·-...0~......
••• •.... .....~ .
\
o•,,.,,.,,•,•...
40
6
RUN$ ZONEII
EJ C 140·C
14 & F I~OoC----0 160·C._....-..
12
LtJ2-I-
10
I.IJ(.)
ZlIJQ-enLtJ~
8
,..c-:2
SCREW SPEED (Rpm)Fi gure 37. Res i dence Time versus Screw Speed
Figure 38 Scanning Electron Micrograph of UntexturizedSoy Protein with Strands of Fibers, lOOOX
Figure 39. Optical Microscope of Fibrous Structure of Run F3,150X
84
from figure 39 was
figure 41 shows the
moisture, 80 RPM).
85
shown in figure 40 (4000x). Finally,
fibers of run 13 {zone II-160°C, 35%
The limitation of this observation was the
unavailability of mechanical apparatus to measure the
quality of fibers on breaking strength, shear» or "c he w",
Also, the results were equipment specific. Larger scale
experiments should have an increase effect of temperature
and more complex non-Newtonian flow behavior [73].
Figure 40. Scanning Electron Micrograph of an Isolated Fiberof Run F3, 4000X
Figure 41. Scanning Electron Micrograph of Run 13, 1000X
86
Chapter 8
CONCLUSIONS
This study described the importance of controlling the
shear environment in the screw and die, the dough
temperature, and the residence time to produce varying
texturized extruded products of soy protein. The results
indicate the formation of fibrous layers. A summary of the
study follows:
1. Soy protein was continuously extruded by the MTE
process.
2. Controlling the shear rate and the flow rate through
the screw and the die was important in cantrall ing
fiber formation. Too high a shear rate at the die wall
disrupted the fibers.
3. Increasing the shear rate and the residence time (5-10
minutes) tended to enhance cross-linking between
protein.
4. The extrudate characteristics were highly dependent on
screw speed and temperature.
5. The operating pressure and extrusion rate were
dependent on the temperature, moisture, and screw
speed.
6. Process conditions were altered as a result of a longer
assembly line than in normal extrusion; pressure drop
88
was increased from 300 to 1500 psi and residence time
from 5 to 15 minutes.
7. The product absorption was dependent on screw speed and
initial moisture content.
8. Product temperature was found to be a function of the
zone set temperatures and screw speed.
9. Dough temperature. was higher than the process
temperature due to the lack of a cooling system and
heat generation.
10. Plugging of the die to increase pressure was not
feasible, since the resultant prolonged cooking time
would cause degradation.
11. Optimum operating conditions to a produce fibrous
texture were found to be a temperature profile of
160-135-110 0C, 80 RPM, and 40% moisture for the
equipment used in this study.
89
Chapter 9
RECOMMENDATIONS
1. The use of a cooling system would provide better
control of the dough temperature, resulting in better
control of bulk density. Frictional heat due to
mechanical work usually builds up at the screw section
and the die land.
2. The use of mechanical tests to evaluate the f i ber s '
quality, such as:
shear force - Warner-Bratzler shear,
shear force and work - Kramer Shear Press,(firmness and crispness)
texture measurement - General Food Texturometer,
and breaking strength - Instron, Model TM.
would yield better evaluation.
3. Extrusion should be attempted at lower temperature
gradients.
4. The feed system should be modi fied for better control
of feed ra te.
5. Horizontal extrusion causing a higher deformation would
produce better fibers.
6. Extrusion with the Leistritz twin screw extruder should
be attempted. Good shearing, flow control, and
controllable feed rate in the twin screw extruder will
provide a better control of the final texture of the
90
soy protein product.
7. Higher die temperatures should be attempted.
8. Further study is needed to determine if soy protein
crystallization is affected by the independent
variables.
9. Computer simulation should facilitate better control of
the pressure, temperature, and screw speed.
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42. W.O. Statton, J. of Polym. Sci.: Part f., No. 20, pp.117-144 (1967):- -
43. J.R. Collier, T.Y.T. Tam, J. Newcome, and N. Dinos,Polym. ~. Sci., Vol • .!i, No.3, p • 204 (March 1976).
44. B.P. Pandya, M.S. Thesis, Chemical Engineering, OhioUniversity, 1981.
45. L. Holiday and I.M. Ward in Structure and Pro~ties ofOriented Polymers, edited by I.M. Ward:-ApprTed-SCTencePublishers, London, 1975, p. 18.
46. J.R. Collier, S.L. Chang, S.K. Upadhyayula, IIFlowInduced Crystallization," Monog,raph, No.6. (1979).
47. T.Y.T. Tam, Ph.D. Thesis, Chemical Engineering, OhioUniversity, 1975.
48. J. Newcome, Ph.D. Thesis, Chemical Engineering, OhioUniversity, 1976.
94
49. S.K. Upadhyayula, M.S. Thesis, Chemical Engineering,Ohio University, 1978.
50. C.B. Rao, M.S. Thesis, Chemical Engineering, OhioUniversity, 1980.
51. K. Lakshmanan, M.S. Thesis, Chemical Engineering, OhioUniversity, 1980.
52. M. Barger, M.S. Thesis, Chemical Engineering, OhioUniversity, 1982.
53. G.H. Brown, Amer. ~i., Vol. 60, No.1, p , 64 (1972).
5 4 • Leo Man del k ern , Cry s tal 1 i z a t ion 0 f Pol ym~!~ , Mc Graw Hill, New York, 1964.
55. P.H. Geil, The Morphology of Crystallization Polymers,APreli min aryE ~1 MSEe d ucat ion mod u1e pre par ed for theASEE Meeting, Urbana, 11., June 1980.
56. O.M. Bigg et al., Polym. Enir. Sc i . , Vol. ~~, No.1,pp. 27-33 (Jan. 19821. -- - -
57. John T. Hayes et al., U.S. Patent No. 3,886,298,1975.
58. G. Puski and A.H. Konwinski, U.S. Patent No. 3,950,564,1976.
59. A. Felbrugge et al., U.S. Patent No. 3,886,299,1975.
60. Oak B. Smith, Inst. of Food Sci. and Technol., Vol. g,No.1, pp. 15-~March-yg19r:-
61. M.F. Campbell, JAO~, Vol. 58, pp. 336-338 (March1981).
62. Atkinson, U.S. Patent No. 3,488,770, 1970.
63. D. van Zuilichem, Inst. of Food Sci. ~~ Te£hnol., Vol.~, No.1, pp. 5-1~arCh 1929)-.-
64. J.M. Faubion, R.C. Hoseney and P.A. Seib, Cereal FoodsW0 r 1d , Vo 1. ~, No.5, Pp , 212 - 216 ( May 1982). ---
65. E.J. Briskey in Evaluation of Novel Protein Products,edited by A.E. Bender et al ~ Pergamon Press,---=tOronto,1970.
66. A.M. Hermansson, Lebensm. Wis. U. Technol., Vol. ~, No.1, pp. 24-29 (1972).
67.
68.
95
Owen L. Davies, ed., The Desi~ and Analysis ofI nd us t ria 1 ExEe rim e n t s J lla1 nerlfUDl i s1iTn 9 ,---Y:V:-;-l 9bf ,p p , 495-578.
E.G.Henika, Cereal Sc!. radar, ~£l. !i, p. 309 (1972).
69. Daniel K. Tang, Senior Development Engineer, A.E.Staley, Mfg. Co., Personal Communication, 1983.
70. SAS Institute Inc., SAS Circle, P.O. Box 8000,Cary,N.C. 27511-8000.
71. Zehe v Ta?m0 r. and I mric h K1e in, En9 i nee r i n.[ Pr i .!!£!.e.1e sof Plastlcatlng Extrusion, Van Nostrand, Reinhold Co.,New York, 1970, p • 384
72. Y. Victor Wu and George E. Inglett, J. of Food Sc t • ,Vol. ~, pp. 218-225 (1974). - ----
73. T.F. Tsao, J.M. Harper and K.M. Repholz,Pharmaceutical and Bioe~~erin,[ 1967/ll,George T. Tsao, Vol. 74, No. 172, AIChE,142-147.
in Fooded i te<rby1978, pp ,
APPENDICES
96
APPENOIX ATable 7
Die Temperatures
97
===============================================================CONDITION TEMPERATURE (C)* SPEEO*
CODE ZONE II ZONE III ZONE IV (RPM)MOISTURE Die
(w/o)* Temp C===============================================================
AlA2A3A4
81628384
ClC2C3C4
DlD20304
E1E2E3E4
F1F2F3F4
G1G2G3G4
HIH2H3H4
I 1121314
140140140140
140140140140
140140140140
150150150150
150150150150
150150150150
160160160160
160160160160
160160160160
115115115115
115115115115
115115115115
125125125125
125125125125
125125125125
135135135135
135135135135
135135135135
90909090
90909090
90909090
100100100100
100100100100
100100100100
110110110110
110110110110
110110110110
406080
100
406080
100
406080
100
406080
100
406080
100
406080
100
406080
100
406080
100
406080
100
30303030
35353535
40404040
30303030
35353535
40404040
30303030
35353535
40404040
67.578.388.390.0
75.080.085.090.0
65.075.075.079.0
78.679.086.795.0
50.075.0
100.0100.0
75.075.080.090.0
80.688.694.3
100.0
80.091 . 795.092.1
75.082.590.090.0
Note: *Zone I was unheated, and Zone V washeated to 50 degrees Celsius.
Table 8 98Flo:w Rate s
CONDITION VO[.RATEEXT.RATE*CODE (in/min) (in3/hr)
=============================================Al 20.5 + 2. 7 38.4-A2 33.7 + 1 . 5 63.2
37.7-
70 . 7A3 + 3 . 144.0
-1.8 82.5A4 ±
B1 24.0 ± 0.5 45.082 23.7 ± 3 . 1 44.483 33.3 ± 0.9 62.484 44.1 ± 4 . 1 82.7
C1 19.0 + 2.8 35.6C2 29.0 + 2.9 54.4
32.2 - 3.2 60.4C3 +-C4 34.4 ± 3.4 64.5
01 24.0 + 2.5 45.0-02 22.3 ± O. 7 41.803 31.0 ± 3.8 58 . 104 44.3 ± 2.4 83.1
E1 7.5 ± 1 . 2 14. 1E2 16.5 + 2.2 30.9-E3 21.6 + 4.1 40.5E4 33.2 + 3.8 62.2
Fl 12.9 + 2.6 24.223.8
-1.3 44.6F2 +-
45.0F3 24.0 + 1 . 7F4 27.1 + 1 . 7 50.8
Gl 20.6 + 1.8 38.6G2 27.9
-2.5 52.3+
G3 30.8 + 2.2 57.8G4 45.7 -:;: 4.1 85.7-
HI 18.6 + 1 . 5 34.9H2 27.3 + 2.3 51.2-H3 31.7 + 2 . 7 59.4
42.9-
3.2 80.4H4 +-
11 13.2 ± 0.3 24.812 24.8 ± 3. 1 46.513 27.7 ± 1.4 51.914 28.9 ± 4.0 54.2
*90% confidence 1i mi t
Table 999
Pressure Profiles
============================================================CONDITION P R E S S U R E* ( psi )
CODE barrel die drop============================================================
Al 2742 ±124 1442 ± 45 1300 ± 85A2 2608 ± 45 1350 ± 70 1258 ± 58A3 2300 ±183 1150 ± 76 1150 ±.130A4 2075 ±109 1068 ± 75 1007 ± 92
81 864 ± 44 543 ± 42 321 ±. 4382 943 ±177 543 ± 42 400 ±. 8083 978 ± 36 629 ±. 25 350 ± 3184 1043 ± 73 621 ± 52 430 ±. 62
Cl 1207 ±332 664 ±281 528 ±300C2 985 ± 35 543 ± 36 372 ±. 35C3 980 ±116 480 ± 68 420 ±. 48C4 900 ± 50 450 ± 45 460 ± 23
01 1885 ±216 1157 ± 73 729 ±14502 1767 ±146 1150 ± 76 617 ±.lll03 1571 ±103 864 ±153 773 ±12804 1400 ±320 793 ±260 575 ±290
E1 680 ±213 310 ±111 270 .± 16 2E2 857 ±266 546 ±142 341 ±204E3 1000 ±.100 550 ±. 50 470 ± 25E4 1030 ±194 530 ± 75 550 ±135
Fl 540 ± 83 450 ± 87 80 ± 85F2 550 ± 76 441 ± 73 108 ± 74F3 558 ± 73 425 ±. 55 133 ± 64F4 557 ± 86 393 ± 49 170 ± 45
G1 1729 ± 45 950 ± 38 779 ± 41G2 1914 ±164 1012 ± 29 854 ±. 96G3 1800 ±141 900 ±130 900 ±136G4 1714 ±155 785 ± 99 917 ±127
HI 1120 ±117 710 ± 66 410 ±. 92H2 1071 ±.103 614 ± 35 457 ±.. 69H3 1121 ± 99 586 ± 44 535 ± 72H4 1150 ±. 60 560 ± 60 589 ±. 60
I 1 720 ± 24 470 ± 25 250 ± 4012 600 ± 50 363 ± 13 238 ± 1013 529 ± 70 321 ± 59 209 ± 6514 479 ± 36 300 ± 38 179 ± 37
*95S conffdence limit
Table 10Extrusion Characteristics
-~~-~-~---~-~~-----~~--~~~-----~--~~~~-----~~~--~--~-~~~~-~~----~~-~-~~-----~~-------~-~~
100
CONDITIONCODE
ABSORPTION(w/o)
Bulk den.(glee)
=============================================AlA2A3A4
81828384
C1C2C3C4
01020304
E1E2E3E4
FlF2F3F4
G1G2G3G4
HIH2H3H4
I 1121314
63.847.833.833.5
25.925.825.727.5
33.533.930.930.5
45.839.432.526.8
56.347.533.030.0
39.333.530.322.5
39.934.534.530.9
28.027.527.332.4
27.031.035.520.3
1.491.531.581.66
1.541 . 511.461.53
1.781.541.821 • 79
1.561.581.611.66
2.561.701.481.59
1.491.541.541.61
1 . 711.661.601.67
1.641.591.581.57
1.651.621.571.56
Appendix B
101
FILE: c sj- r r S4S A
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THE QE5PCNSE SUPf=ACE AN·,\l.Y51 s -~s nr:pror.-~~D eNSOYBEAN PPOTEIN EXTTPU5TQN IN ~ELT Tn.NSF~RM_TtON
EXTRUSICN PROCESS. T~E 08JECTIV~ WAS TO OIscaVEPWHIC~ FACTOR VALUES (INDF~ENnENT VAPtAAL~~l
OPTIMIZE A RESPONSE. T~F P~P_METERS IN T~F M~OEL
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THE RSPEG PROCEDUPE FI~ i~E PAPA~~~FPS OF ACO,.:JLETE QUADRAT IC RESPONSE ~UPF"_CE 4NO THENDETERMINED cPtTtC~L V~LU~S TC CP~I~T7~ ~H= PESP~N5E
WIT~ RESPECT TO T~E ~ACT~~S T~ ~~E MODEL
.-----------------------------------------------------*•O_TA A;INPUT y X I-X 3 G1a;
LABEL V=EXTPUSICN QATEXt=TEMPER4TUPEX2=SC REW c;PE E ')X.3=MO I STURE;
CARDS;20.5 140 40 30 24.0 140 40 35 19.0 16.0 40 40 ~4.0 150 40 30.33. 7 140 6J 30 23.7 16.e 60 .,c:: 2'1.0 16.V tiC 40 :!2.3 150 60 3037.7 140 AO 30 ~1.3 140 FiO ,! ~?2 1 A·O PO 40 , t , 0 150 80 ::10••• 0 140 100 30 44.1 140 100 35 ""'.4- 140 1 00 40 44."1 ISO 100 307.5 150 40 35 12.Q l~u 4\j 40 20.f» l~O 40 30 18.() IFt~ 40 15
16.5 150 60 35 23.8 150 60 J!: ;'7.1 1"0 1;0 ~c=; ';'7.' 160 60 ~5
21.6 150 eo 35 24..0 ISO 80 3~ '0.8 If,O ~o 35 :JI.7 160 80 ~5
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\1C DEL V= x 1- X ~/ L .\ CK FIT;OAT_ B:
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I~ EOF THEN DC: Y:.; Xl=15~.6~pq;
00 )(2=40 TC 100 HV 1;00 X3= 2u TO 4-U 8V o.~;
OUTPUi: ENO; END; END;PRQC RSPEG DAT~=A OUl=C ppcnIC~ NOPP~NT:
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TITLE CONTOuP PLOT OF 5CPE~ SPFEn (~P'~) ~Nf' ~ISTUPE (W'Cl;TITLE2 CCNTCUR~ APE EXTRUSYCN ~A~~~ (IN/~IN):
/.
APPENDIX C
Table 11Regression Coefficient
102
Coefficients Extrusion Die Absorp- Bulk ProductRa te Pressure tion Density Temperature
~~--~------------~---~~~~---~-~~-~-~--~---------~~~~-~----~---
80 1719. 35479. -390.78 -11.80 258.82
B1 -23.22 -267.63 9.86 0.13 -4.55
82 0.35 -11.47 -2.15 0.00 1.27
83 2.31 -727.89 -11.73 0.21 4.97
B11 0.08 0.77 -0.04 0.00 0.02
822 0.00 -0.02 0.00 0.00 0.00
B33 0.06 7.40 0.07 0.00 -0.08
812 0.00 0.01 0.01 0.00 -0.01
B13 -0.04 0.85 0.03 0.00 0.01
823 0.00 0.31 0.03 0.12 -0.01
df
Tab
le12
An
aly
sis
of
Var
ian
ce
Ex
tru
sio
nD
ieB
ulk
Ab
sorp
-R
ate
Pre
ssu
reD
ensi
tyti
on
Die
Tem
per
atu
re
Lin
ear
Qu
adra
tic
Cro
ssP
rod
uct
Lac
ko
fF
it
Err
or
R
3 3 3
20 6
.00
01
.00
01
.07
45
.25
96
.88
34
.00
01
.00
04
.22
76 1
.89
8
.84
02
.44
63
.88
45
.00
19
.14
01
.00
06
.62
76
.25
35
.21
28
.53
89
.00
01
.41
8
.87
72 1
.74
26
......
o w
VA
RIA
BLES
Tab
le13
Lev
els
of
Vari
ab
les
Sig
nif
ican
ce
onE
xtr
ud
ate
Ch
ara
cte
rist
ics
Ex
tru
sio
nD
ieB
ulk
Ab
sorp
-R
ate
Pre
ssu
reD
ensi
tyti
on
Pro
du
ctT
emp
erat
ure
Tem
per
atu
re.0
00
1.0
06
4.9
07
1.3
90
8.0
21
4
Scr
ewS
pee
d.0
00
1.0
5.5
78
.00
81
.00
01
~10
is
ture
.00
04
.00
01
.93
23
.06
54
.14
4
Reg
ress
ion
88.3
%89
.8%
14.0
%53
.89%
74.2
6%(R
-sq
uar
e)
~ o +::a