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

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2.2 SOY PROTEIN EXTRUSION The current production of soy protein films are made via one of two techniques, wet or dry. The wet technique is done by solution casting as previously mentioned. To elaborate, the protein is typically solubilized using large amounts of aqueous solvent and dehydrated on a flat surface. The solubility of the protein is enhanced by applying heat around 80 o C under alkaline conditions. With elevated pH, SPI is known to form β-sheet structures through intermolecular hydrogen bonds during drying (Subirade et al. 1998). Alkaline casting also yields mechanically stronger performing films due to higher protein solubility. Casting around neutral pH yields heterogeneous films with insolubilized protein particles causing uneven film matrices leading to weak mechanical properties (Cho et al. 2007; Gennadios et al. 1993). By contrast, dry techniques occur in the presence of a minimal amount of water and involve the use of thermal and mechanical energies to form films. Some of these thermo mechanical methods include compression molding or extrusion (Cuq et al. 1997; Liu and Kerry 2006; Pommet et al. 2005). Prior to 1998, studies have only focused on solution casting and compression molding due to the ease of production (Ralston 2008). However, these methods are time consuming batch processes that yield low throughput thereby eliminating opportunities for industrial scale-up. By using extrusion, processing of SPI would not only be more efficient but can easily integrate with existing manufacturing infrastructures for both food and packaging industries. Extrusion is a continuous process whereby raw materials, plasticized and conveyed by a screw, is pushed through a film-forming slit die. The process can involve feeding, heating, cooling, shearing, compressing, reacting, mixing, melting, homogenizing, and amorphousizing (converting crystalline polymer to amorphous configurations) (Hernandez-Izquierdo and Krochta 2008). The extrusion of SPI into film can be similarly described by the extrusion cooking process whereby the extruder is divided into three main zones; feeding, kneading, and heating. These 6
zones are synonymous to feeding, transition, and metering for single screw polymer extrusion. Feeding is where raw materials are introduced into the barrel and slightly compressed with the expelling of air. As the materials are conveyed to the kneading zone, screw flights are filled leading to higher compression that increases pressure, temperature, and material density. The heating zone is the final section before the melt exits the extruder. The highest temperatures, shear rates, and pressures are achieved in this zone yielding the final product characteristics (Hauck and Huber 1989). Process variables include screw speed, screw configuration, barrel temperatures, and die configuration. Response variables include product temperature, residence time, torque, specific mechanical energy input, and pressure at the die. The typical target variables for film are mechanical, barrier, and color properties (Hernandez-Izquierdo and Krochta 2008). Since proteins are inherently hydrophilic, moisture content of film, which is dependent on relative humidity, is also an important variable. To allow for the extrusion of proteins, their viscoelastic behavior needs to be modified and controlled to facilitate material flow. Within the extruder, this is dictated by thermal and mechanical denaturation whereby a balance between aggregation and de-aggregation needs to be controlled (Pommet et al. 2005; Redl et al. 2003; Redl et al. 1999b). Insufficient heating would not unfold soy protein into melt deterring flow and chain alignment during extrusion. Excessive heating will cause premature aggregation from chemical cross-links, increasing melt viscosity and disrupting extrudate structure (Verbeek and van den Berg 2010). Increased network formations from heating are thought to be caused by an increase of polymer chain associations from hydrophobic interactions and the formation of disulfide bonds (Prudencio- Ferreira and Areas 1993; Redl et al. 1999b; Rouilly et al. 2006; Toufeili et al. 2002). As such, temperatures must be controlled above glass transition (Tg) but below degradation temperature to allow unfolding and ease processing. Morales and Kokini (1997) studied the glass transition of soy protein as a function of moisture content. They found the Tg of the 7S fraction ranged 7
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 and 14: einforcement material. Research int
Page 15: via centrifugation into four fracti
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
Page 65 and 66: 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
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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
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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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