THESIS - ROC CH ... - FINAL - resubmission.pdf - University of Guelph

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2.0 LITERATURE REVIEW 2.1 SOY PROTEIN Soybeans have been widely popularized since the 1930’s as an agricultural cash crop due to their high oil and protein contents. With around 30 to 40% of the natural soybean composed of protein, much attention has been focused on expanding potential uses for this natural biopolymer. The protein fraction of the soybean can be extracted in two forms known as a concentrate (70 - 80%) or an isolate (> 90%). Due to the protein fraction being the main potential for bioplastic production, much research has been focused on the isolate form (Hernandez-Izquierdo and Krochta 2008; Song et al. 2011; Zhang and Mittal 2010). Using protein as a natural polymer to replace petroleum plastics requires the reconfiguration of the natural protein structures. There are mainly four levels of structure that make up the protein macromolecules. The primary structure is the linear chain of sequenced amino acids. The secondary structure is the first level of folding with amino acid chains bound by strong hydrogen bonds. This folding creates patterned structures with the two most common forms known as α-helix and β-sheet (Fennema 1996). The tertiary structure involves linkages of the secondary structures by bonds between the side groups of the amino acids. Tertiary linkages involve hydrophobic interaction, disulfide bonds and hydrogen bonds (Fennema 1996). The folding of the tertiary structure typically favours hydrophobic regions to the interior while exposing hydrophilic regions to the surface (Fennema 1996). These larger folded molecules are then arranged to form the quaternary structure connected primarily by hydrogen bonds and hydrophobic interactions (Fennema 1996). In soy protein, the quaternary level is made of globulin subunits of differing molecular weights ranging from 200 to 600 kDa (Cho and Rhee 2004). These subunits can be fractionated 4
via centrifugation into four fractions known as 2S, 7S, 11S, and 15S. The 7S and 11S fractions make up 37% and 31% respectively of the total extractable protein with molecular weights ranging from 180 to 360 kDa (Wolf and Cowan 1975). These molecular weights are a good indicator of the polymer length with higher chain lengths typically translating to better mechanical properties. Some synthetic plastics such as high density polyethylene (HDPE) have molecular weights ranging from 200 to 500 kDa, which are comparable to SPI, revealing the good potential of soy protein as a replacement of synthetic polymers in certain applications (Ralston 2008). To form SPI films, the protein structures of the native state would need to be denatured to reform new configurations via new linkages within the protein molecule. Denaturation of the protein can be induced by changes in pH, electrical force, mechanical force, or heat (Fennema 1996). Changing pH conditions away from the isoelectric point (4.2 - 4.6 for SPI) can cause the protein to unfold and increase solubility. Casting leverages this phenomenon by evaporating solubilized SPI solution on a flat surface forming film. Mechanical forces like pressure and shear are known to break bonds and induce flow in an extruder which is important for increasing intermolecular entanglement (Verbeek and van den Berg 2010). Heat denaturation of protein typically occurs above a certain threshold temperature. For SPI, this is generally between 65 to 70 o C (Morgan 1989). As the proteins unfold, sulfhydryl and hydrophobic groups are exposed and disulfide bonds are reformed, thereby forming new structural arrangements. With the use of heat, pressure, and shear, extrusion can greatly benefit the goal of denaturing SPI to reform into continuous films. 5
Page 1 and 2: A Study on the Extrusion of Soy Pro
Page 3 and 4: ACKNOWLEDGEMENTS My research would
Page 5 and 6: 4.3.9 Statistical Analysis.........
Page 7 and 8: LIST OF TABLES Table 2.1: Compariso
Page 9 and 10: Figure 5.2: Light optical microscop
Page 11 and 12: 1.0 INTRODUCTION The production of
Page 13: einforcement material. Research int
Page 17 and 18: zones are synonymous to feeding, tr
Page 19 and 20: Ralston (2008) investigated the ext
Page 21 and 22: onding between hydroxyl groups and
Page 23 and 24: Table 2.2: Summary of cellulose par
Page 25 and 26: through the use of enzymes have pro
Page 27 and 28: matrix such as soy protein (Wang et
Page 29 and 30: 4) Explore the extraction process f
Page 31 and 32: 4.3 METHODS 4.3.1 SAMPLE PREPARATIO
Page 33 and 34: a Figure 4.2: a) Schematic of extru
Page 35 and 36: length at break by the initial grip
Page 37 and 38: 4.4 RESULTS AND DISCUSSION 4.4.1 SP
Page 39 and 40: Further experiments were carried ou
Page 41 and 42: Figure 4.5: Film with rough texture
Page 43 and 44: extrusion screw to continuously bre
Page 45 and 46: stopped which fixes the spherical s
Page 47 and 48: 4.4.3 MECHANICAL PROPERTIES Mechani
Page 49 and 50: Elongation at break (%) Figure 4.10
Page 51 and 52: Table 4.5: Water vapor permeability
Page 53 and 54: 4.4.5 FTIR ANALYSIS The main absorb
Page 55 and 56: 4.4.6 CONCLUSION The extrusion of S
Page 57 and 58: 5.3 METHODS 5.3.1 CELLULOSE EXTRACT
Page 59 and 60: For mechanical treatments, the obta
Page 61 and 62: initial soy biomass; SNF and SMF. T
Page 63 and 64: compiled by Moon et al. (2011), thi
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RSH: 5min HPH: 20 passes, 4000 - 60
Page 67 and 68:
SMF micrographs, the presence of fi
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process as described. However, it m
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a peak at 22.6° is representative
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chemical and mechanical treatment h
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6.3 METHODS 6.3.1 SAMPLE PREPARATIO
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6.3.3 FILM CONDITIONING Similar to
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increased in size. At fiber concent
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6.4.2 MORPHOLOGY AND STRUCTURE Due
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SEM images of the cryo-fractured su
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Table 6.1: Mechanical properties of
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cellulose and SPI. This high interf
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concentrations at isolated sites. A
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Similar to Section 4.4.5, dominatin
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Further analysis of the Amide II ba
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specimens that have been cryo-crush
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crushing. Conversely, this could al
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7.0 EXPLORATORY WORK WITH TIO 2 NAN
Page 101 and 102:
7.3.2 COMPOUNDING AND EXTRUSION Com
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smaller size of P90, the ability to
Page 105 and 106:
Table 7.1: Mechanical Strength of T
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Modulus of Elasticity (MPa) 120 110
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(21 nm) particle was seen to have a
Page 111 and 112:
7.4.3 MECHANICAL PROPERTIES OF TIO2
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Tensile Strenght (MPa) 12 11 10 9 8
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Modulus of Elasticity (MPa) 200 180
Page 117 and 118:
8.0 CONCLUSIONS AND RECOMMENDATIONS
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The viability of introducing a comp
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acting as a coupling agent for furt
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Cherian BM, Leao AL, Souza SFD, Tho
Page 125 and 126:
Kacurakova M, Capek P, Sasinkova V,
Page 127 and 128:
Pääkkö M, Ankerfors M, Kosonen H
Page 129:
Wang N, Ding E, Cheng R (2008) Prep
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THESIS - ROC CH ... - FINAL - resubmission.pdf - University of Guelph

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