High Shear Extrusion Research Articles

Twin-Screw Extrusion Mechanical Pretreatment for Enhancing Biomethane Production from Agro-Industrial, Agricultural and Catch Crop Biomasses

This study aimed to evaluate the effects of mechanical treatment through twin-screw extrusion for the enhancement of biomethane production. Four lignocellulosic biomasses (i.e., sweetcorn by-products, whole triticale, corn stover and wheat straw) were evaluated, and two different shear stress screw profiles were tested. Chemical composition, particle size reduction, tapped density and cellulose crystallinity were assessed to show the effect of extrusion pretreatment on substrate physico-chemical properties and their biochemical methane production (BMP) capacities. Both mechanical pretreatments allowed an increase in the proportion of particles with a diameter size less than 1 mm (from 3.7% to 72.7%). The most restrictive profile also allowed a significant solubilization of water soluble coumpounds, from 5.5% to 13%. This high-shear extrusion also revealed a reduction in cellulose crystallinity for corn stover (i.e., 8.6% reduction). Sweetcorn by-products revealed the highest BMP values (338–345 NmL/gVS), followed by corn stover (264–286 NmL/gVS), wheat straw (247–270 NmL/gVS) and whole triticale (233–247 NmL/gVS). However, no statistical improvement in maximal BMP production was provided by twin-screw extrusion. Nevertheless, BMP kinetic analysis proved that both extrusion pretreatments were able to increase the specific rate constant (from 13% to 56% for soft extrusion and from 66% to 107% for the high-shear one).

Optimization of process parameters for the development of gluten free extruded breakfast cereal based on Quinoa, finger millet and red rice using RSM.

Current research aims to evaluate the effect of high shear extrusion on quinoa, finger millet, and red rice composite flour-based breakfast cereal using response surface methodology with extruder barrel temperature (120-130°C), screw speed (320-350rpm) and feed moisture content (10-20g/100g) as independent variables. Product responses were fitted on to mathematical model using second-order polynomial equations. Multiple regression analysis of data revealed the high statistical significance of respective mathematical models. Numeric optimization based on acceptable product characteristics revealed optimized processing conditions (barrel temperature 130°C, screw speed 350 RPM, and feed moisture content 20g/100g) with a desirability of 0.9373. Extrudates developed using selected processing conditions along with optimized ones and control were characterized for their nutrient profile and crystallinity. Breakfast cereal developed using optimized processing conditions showed a better nutritional profile and reduction in crystallinity of product after high shear extrusion processing represented starch gelatinization.

Highly dispersed graphene nanoplatelets in polypropylene composites by employing high-shear stress for enhanced dielectric properties and frequency-selective electromagnetic interference shielding capability

Although graphene nanoplatelets (GNPs) are currently receiving significant interest as a filler for polymer composites, the issue of agglomeration is yet to be overcome for their wide applications. Herein, the high-shear extrusion technique was thoroughly investigated to effectively disperse GNPs in a polypropylene (PP) matrix with a content of 3 wt%. The screw rotation speed was controlled in the range of 1000–3000 rpm, which is extremely high corresponding to the shear rate of 733–2199 s−1 that should be compared with 200 rpm and 99 s−1 of a conventional extruder, respectively. As the shear rate increased, the size of GNP agglomerates decreased from several microns to ca. 250 nm. This size reduction resulted in the significant enhancement of dielectric loss, owing to the strong interfacial polarization at the interfaces between the GNPs and PP matrix. Furthermore, frequency-selective characteristics in electromagnetic interference shielding could be controlled in the wide frequency spectrum covering the X- and Ka-bands by adjusting the shear rates providing different aperture sizes specified by the interstitial distances of GNPs. Altogether, the developed GNP/PP nanocomposites and their methodology have remarkable potential as promising solutions for graphene-based polymer composites.

Changes to fine structure, size and mechanical modulus of phytoglycogen nanoparticles subjected to high-shear extrusion

This study aims to enhance the understanding of the structure of maize phytoglycogen nanoparticles, and the effect of shear scission on their architecture, radius, stiffness, and deformability. Compared to amylopectin, phytoglycogen had a lower A:B chain ratio, a lower number of chains per B chain, and a much higher number of Afingerprint chains. Phytoglycogen (Mw = 28.0 × 106 g/mol) was subjected to high-shear extrusion with varying Specific Mechanical Energies (SMEs) using different screw speeds, showing a maximum stable molecular weight Mw of ∼9.31 × 106 g/mol and a particle radius R reduction of 36 %, with a corresponding 20 % increase in the average mass density. Atomic force microscopy force spectroscopy revealed that nanoparticles extruded at the lowest SME (122 Wh/kg) exhibited a 20 % increase in Young's modulus. Higher SME values (up to 488 Wh/kg) resulted in an overall decrease in stiffness without further significant reductions in radius.

Biodegradable blends of thermoplastic waxy starch and poly(ε-caprolactone) obtained by high shear extrusion: Rheological, mechanical, morphological and thermal properties

The aim of this work was to develop polymer blends of plasticized thermoplastic waxy starch (TPS) and poly(ɛ-caprolactone) (PCL) using the largest amount of TPS possible to obtain a biodegradable material motivated by sustainability issues and to replace petrochemical-based polymers with alternatives based on biopolymers. Addition of TPS to other polymers has been used to obtain cheaper and increasingly biodegradable final products. However, TPS presents limited mechanical properties, and mixing with other polymers such as PCL is necessary to overcome these limitations and improve its processability. TPS was processed by extrusion and thermo-compression using 30 wt% glycerol. The blends were suitably processed by extrusion and further injected. The TPS/PCL blends were studied by varying the amount of PCL in a range of 10 wt% in increasing order of addition. Thermal analysis showed that introducing PCL in TPS increased Tonset because of the higher thermal stability of the former, and that the obtained blends presented a behavior intermediate to that of neat polymers.Graphical Abstract

High shear cooking extrusion to create fibrous mozzarella cheese from renneted and cultured curd

To understand shearing on cheese curds during high shear extrusion, the controlable parameters of a twin-screw extruder were related with measured and calculated parameters that characterise the extrusion process effects on product properties. Curd properties were correlated with specific mechanical energy SME (23–390 kJ·kg−1), Texit (22–54 °C) and residence time RT (36–507 s); the wide experimental range studied provided new insights regarding extrusion of cheese curds. Longer and finer fibers were produced at low SME (23–27 kJ·kg−1), high Texit (50–54 °C) and short RT (55–60 s). Whereas extruded curds produced at high SME (166–390 kJ·kg−1), low Texit (22–23 °C) and long RT (371–396 s) tend to form a compact structure with less fiber formation. Temperature in the heating section, Th, and temperature of the cooling die, Tc, were found to determine critical curd phase transitions during extrusion, from viscoelastic solid to viscoelastic liquid and vice versa, that are important for the creation of fibrous cheese curd structures. Tc was the most important factor influencing SME, indicating the considerable contribution of the cooling process in increasing the shear forces. Curd composition and textural properties were significantly influenced by Th and Tc, showing that a higher Th enhances curd elasticity and reduces melt strength while a higher Tc induces lower water content and increases melt strength. We concluded that a variety of structured mozzarella products with customized properties can be produced by controlling the extrusion parameters.

Dietary resistant starch preserved through mild extrusion of grain alters fecal microbiome metabolism of dietary macronutrients while increasing immunoglobulin A in the cat.

Dietary digestion-resistant starch (RS) provides health benefits to the host via gut microbiome-mediated metabolism. The degree to which cats manifest beneficial changes in response to RS intake was examined. Healthy cats (N = 36) were fed identically formulated foods processed under high (n = 17) or low (n = 19) shear extrusion conditions (low and high RS levels [LRS and HRS], respectively). Fecal samples collected after 3 and 6 weeks' feeding were assayed for stool firmness score, short-chain fatty acids, ammonia, and changes to the global metabolome and microbiome; fecal immunoglobulin A (IgA) was analyzed at week 6. Few differences were seen in proximate analyses of the foods; stool firmness scores did not differ. In cats consuming HRS food, concentrations of fecal butyrate and the straight chain:branched chain fatty acid ratio were significantly greater in feces at both weeks 3 and 6, while fecal ammonia was reduced at week 6 relative to feces from LRS-fed cats. Fecal IgA concentrations were significantly higher at week 6 with HRS food. RS consumption altered 47% of the fecal metabolome; RS-derived sugars and metabolites associated with greater gut health, including indoles and polyamines, increased in the cats consuming HRS food relative to those fed the LS food, while endocannabinoid N-acylethanolamines decreased. Consumption of HRS food increased concentrations of the ketone body 3-hydroxybutyrate in feces and elevated concentrations of reduced members of NADH-coupled redox congeners and NADH precursors. At the microbiome genus-level, 21% of operational taxonomic units were significantly different between food types; many involved taxa with known saccharolytic or proteolytic proclivities. Microbiome taxa richness and Shannon and Simpson alpha diversity were significantly higher in the HRS group at both weeks. These data show that feline consumption of grain-derived RS produces potentially beneficial shifts in microbiota-mediated metabolism and increases IgA production.

Shear-induced enhancement of technofunctional properties of whole grain flours through extrusion

Thermo extrusion is a practical and achievable approach to produce flours with improved techno-functional properties. The aim of this study was to compare the potential of different whole cereals, pseudocereals and legumes to produce techno-functional flours by means of high-shear extrusion. Whole flours from oat, sorghum, amaranth, quinoa, chickpea, lentil, black bean and pinto bean were extruded under selected specific mechanical energy (SME) to achieve functional modifications. Refined rice flour was used for comparison purposes. Extruded flours presented a diversity of functional properties depending on the raw material. In general, hot peak viscosity was lost and final viscosity was significantly reduced due to the extrusion conditions. Extruded flours presented higher apparent viscosities under cold conditions compared to raw flours. The hydration properties and water solubility index were improved after extrusion. The oil binding capacity, protein solubility and foaming properties were affected depending on the extruded material. Extruded flours produced with cereals and legumes presented cold-gelling capacity. The texture of gels differed depending on the raw material and resting temperature and time. Extruded whole grain flours presented comparable or even better techno-functional properties compared to the extruded refined rice flour. Results obtained herein are promising and may be used to tailor made new techno-functional ingredients that can be used for formulation of new food products.

Consumption of identically formulated foods extruded under low and high shear force reveals that microbiome redox ratios accompany canine immunoglobulin A production.

Digestion‐resistant starch (RS) can provide health benefits to the host via gut microbiome‐mediated metabolism. This study tested the physiological effects on healthy dogs of identically formulated foods processed under high (n = 16) or low (n = 16) shear extrusion conditions resulting in respective lower and higher levels of RS. Faecal samples collected at weeks 3 and 6 were assayed for stool score, proximate analysis, short‐chain fatty acids (SCFA), immunoglobulin A (IgA) and microbiome; faecal metabolome was characterized at week 6. Proximate and digestibility analyses of the foods and stool scores and stool proximate analysis showed few differences between the two shear methods except for increased apparent fibre digestibility in the low shear food. In contrast, levels of butyrate (p = .030) and total SCFA (p = .043) were significantly greater in faeces at week 6 from dogs who consumed the low versus high shear food. Faecal IgA levels were significantly higher at week 3 (p = .001) but not week 6 (p = .110) in the low shear food. Significant differences in 166 metabolites between consumption of the two foods were identified via faecal metabolomic analysis, with changes in sugars, bile acids, advanced glycation end products and few amino acids. Strikingly, consumption of the low shear food resulted in elevated levels of the reduced members of redox couples derived from metabolized sugars and branched‐chain and phenyl amino acids. Alpha diversity of the microbiome showed significantly higher species richness in faeces from the low shear group at week 6, though other measures of diversity were similar for both foods. Twelve genus‐level operational taxonomic units (OTU; half Firmicutes) significantly differed between the food types. Six OTU significantly correlated with RS‐derived sugars and ratios of the redox couples. Taken together, these data show that RS impacts microbiome‐mediated metabolism in the gut, resulting in changes in the reducing state.

Low‐Shear Extrusion of Grains Retains Resistant Starch to Increase Microbiome Saccharolysis and Fecal Hydroxy/Keto Redox Ratios of the Feline Gut

ObjectivesFood extrusion processes mixed ingredients to cook food through application of mechanical shear force and heat. This degrades higher‐order starch structure to improve carbohydrate digestibility in the upper gastrointestinal tract. However, evidence indicates the role that digestion resistant starch (RS) plays in promoting health through activity of the gut microbiome. We examined the impact of reducing temperature and shear force in extrusion‐based processing of feline foods to impact gut microbiome metabolites (postbiotics) related to cat gastrointestinal health.MethodsCats were housed in environments promoting social interaction, had access to natural light that varied with season, daily opportunity to exercise and interact with Caretakers and were fed to maintain healthy body weight. Health was confirmed through clinical indices. Collections were under IACUC approved protocols. Identically formulated diets (poultry meal, rice, corn gluten, corn, cellulose and micronutrients) were produced with either HIGH or LOW shear force. Specific Mechanical Energy (SME) for the HIGH shear was 52 W.h/kg, and the Specific Thermal Energy (STE) was 41 W.h/kg, for a Total Energy (TE) of 94 W.h/kg. The SME for the LOW shear parameters was 22 W.h/kg, and the STE was calculated to be 38 W.h/kg, for a TE of 61 W.h/kg. Dietary intakes of RS were 0.3 g/(kg BW^0.75) and 5.1 g/(kg BW^0.75) for the HIGH shear and LOW shear groups, respectively. Randomized design, 2 groups; High Shear extrusion (HIGH, n = 18) and Low Shear (LOW, n = 19). Cats fed for 8 weeks; fecal collections in week 4 and 8. Fecal analyses: metabolomics by multiplatform LC‐MS, short chain fatty acids (SCFA) by GC‐FID and ammonia by indophenol colorimetry. Data were analyzed by independent t‐test for group‐wise differences at the 4 and 8 week timepoints.ResultsThe primary finding was of heightened gut microbiome saccharolysis and fermentation in the cats fed the LOW shear food, indicated by increased RS‐derived fecal saccharides maltotriose, maltose and glucose as well as increased fecal butyrate and lactate. By 8 week there was also a reduction in gut microbial putrefaction as indicated by decreased fecal ammonia and branched SCFA derived from valine, leucine and isoleucine. Also notable was the global shift in NADH/NAD+ redox couples (hydroxy/oxo couples) toward a more reduced state, such that 5 observed couples all had ratios significantly favoring the hydroxy form over the oxo form in the LOW‐ vs HIGH‐shear foods.ConclusionsOptimizing food extrusion for cats can enable more robust saccharolysis and resultant fermentation by the gut microbiome to promote production of postbiotics known to provide health benefits. Additionally, processing of the food resulted in decreased putrefaction by the feline gut microbiome. Finally, we document evidence that providing RS to a gut microbiome shifts the microbiome NADH/NAD+ redox milieu to favor the hydroxy (vs oxo) form of common two‐electron couples. This work is expected to increase the awareness of the benefits that resistant starch can have for an animal typically considered an obligate carnivore.Support or Funding InformationHill's Pet Nutrition, Inc. Topeka, Kansas, USAThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The combined effect of reactive and high-shear extrusion on the phase morphologies and properties of PLA/OBC/EGMA ternary blends

Reactive extrusion and high-shear extrusion are both effective methods to regulate the size of dispersed phase and improve the properties for polymer blends, which have been investigated widely but separately. In this work, the combined effect of reactive and high-shear extrusion has been carried out in polylactide (PLA)/olefin block copolymer (OBC)/ethylenemethyl acrylate-glycidyl methacrylate terpolymer (EGMA) blends to better control the phase morphologies and improve the properties. It was found that, for PLA/OBC binary blends (80/20), the size of OBC dispersed phase decreased from 1.95 to 1.09 μm with increasing the rotation speed from 100 to 900 rpm, but the obtained phase morphologies couldn't be maintained after annealing treatment. In contrast, for PLA/EGMA binary blends (80/20), the effect of shear force on the dispersed phase size was negligible, due to the efficient reaction even under relative low shear force, and the morphologies of the annealed specimens is stable. For PLA/OBC/EGMA ternary blends, the suitable dispersed phase size and appropriate interfacial adhesion regulated by variations of composition and shear force lead to a significant increase of impact toughness. Super toughened PLA/OBC/EGMA blend (80/10/10–900) after annealing treatment shows impact strength of 49.61 kJ/m2, 21 times as comparing to that of the pure PLA. Our work demonstrates the importance of a suitable dispersed phase size and appropriate interfacial adhesion for the improvement of impact strength of PLA/OBC/EGMA blends achieved via a combined effect of reactive and high-shear extrusion.

Largely enhanced energy density of polypropylene based nanocomposites via synergistic hybrid fillers and high shear extrusion assisted dispersion

The energy density of a film capacitor is proportional to the square of the breakdown strength (BDS) of the material. However, polymer composites’ BDS is usually compromised by the filler’s agglomeration, thus resulting in very limited increase in the energy density. In this work, we adopted a high-shear extrusion technique to improve filler’s dispersion. A synergistic effect between montmorillonite (oMMT) and boron nitride (BN) on BDS of polypropylene was observed, particularly for samples prepared by high shear extrusion. As a result, the energy density of PP can be improved from 2.98 J/cm3 to as high as 5.14 J/cm3 while energy discharged efficiency barely changed. In addition, we have also demonstrated that PP/oMMT/BN ternary composites prepared by high shear extrusion show much improved mechanical properties. This work offers a scalable fabrication of PP based nanocomposites with superior energy density that could be easily achieved by using hybrid fillers and high shear extrusion.

Effect of extrusion temperature and screw speed on properties of oat and rice flour extrudates.

Whole oat and rice flours were mixed to develop instant flours by a high pressure and low mechanical shear extrusion process. The screw profile was designed aiming to obtain an infant food with gelatinized starch and high hydration ability. Response surface methodology was selected to study the impact of operating parameters such as temperature and screw speed (73-186 °C; 109-391 rpm) on physicochemical and pasting properties of the final extruded product. The main challenge of this study was to process high oats content, since they are characterized by high lipid and fiber content, which impact on material processing. The optimal response was achieved at 170 °C and 350 rpm. The optimal expansion ratio, bulk density, water absorption index, and water solubility index were 2.24, 289.65 kg m-3 , 6.42 g g-1 , and 4.75 g g-1 respectively. Overall, both temperature and screw speed affected the responses studied, except for water absorption index (only screw speed affected this response). Although lipids from oats reduce the expansion ratio of extrudates compared with samples containing higher starch proportions, their lipids protect the starch granules from mechanical degradation when higher screw speed values are used. As a result, both ungelatinized and gelatinized starches may be found in extrudates, which was confirmed by pasting property analyses. High oat content may be efficiently processed by optimizing the extruder conditions (temperature, screw speed, and profile), improving the nutritional properties of the final product. © 2017 Society of Chemical Industry.

Reinforcement of polyolefins-based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (IPP) and ethylene propylene copolymer (IEPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated-Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO2 systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high-shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization-process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties.

Performance and long term degradation of 7 W micro-tubular solid oxide fuel cells for portable applications

Micro-tubular SOFCs have shown an astonishing thermal shock resistance, many orders of magnitude larger than planar SOFCs, opening the possibility of being used in portable applications. However, only few studies have been devoted to study the degradation of large-area micro-tubular SOFCs. This work presents microstructural, electrochemical and long term degradation studies of single micro-tubular cells fabricated by high shear extrusion, operating in the intermediate range of temperatures (T∼700 °C). A maximum power of 7 W per cell has been measured in a wide range of fuel utilizations between 10% and 60% at 700 °C. A degradation rate of 360 mW/1000 h (8%) has been observed for cells operated over more than 1500 h under fuel utilizations of 40%. Higher fuel utilizations lead to strong degradations associated to nickel oxidation/reduction processes. Quick thermal cycling with heating ramp rates of 30 °C /min yielded degradation rates of 440 mW/100 cycles (9%). These reasonable values of degradation under continuous and thermal cycling operation approach the requirements for many portable applications including auxiliary power units or consumer electronics opening this typically forbidden market to the SOFC technology.

Impact of High-Shear Extrusion Combined With Enzymatic Hydrolysis on Rice Properties and Chinese Rice Wine Fermentation

To better understand how high-shear extrusion combined with enzymatic hydrolysis affects the rice properties and subsequent fermentation, a twin screw extruder incorporated with rice treatment with thermostable α-amylase was used for simultaneous saccharification and fermentation (SSF) of Chinese rice wine. Seven pretreatment methods for rice were compared, and their impacts on rice properties and quality indices of final wine were studied. Enzymatic extruded rice had higher water solubility index (WSI), extent of gelatinization (GE), but lower water absorption index (WAI) and viscosity than those of other treated rice due to a strong synergy of shear action and enzymatic hydrolysis on the degradation and gelatinization of starch. The modification of enzymatic autoclaved rice was smaller than that of enzymatic extruded rice mainly for the lack of mechanical shearing force. Although extrusion with smaller particle size tended to have higher susceptibility to enzyme, the effect was not dramatic. This implied that manipulating particle size had limited effect on the modification of rice properties. Correlation analysis showed that the ethanol yield (EY), fermentation efficiency (FE), amino acid (AA), and soluble solid content (SSC) of finished rice wine increased as rice properties improved by enzymatic extrusion. Overall, simultaneous high-shear extrusion and enzymatic hydrolysis can be an attractive alternative to obtain modified rice with desirable properties for manufacturing Chinese rice wine or other fermentation products.

Studies on the effect of storage time and plasticizers on the structural variations in thermoplastic starch

Starch was combined with plasticizers such as glycerol, sorbitol, glycerol/sorbitol and urea/ethanolamine blends by means of high shear extrusion process to prepare thermoplastic starch (TPS). Effect of storage time and plasticizers on the structural stability of melt processed TPS was investigated. Morphological observation, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal that melt extrusion process is efficient in transforming granular starch into a plasticized starch for all plasticizer compositions. XRD analysis highlights major changes in the microstructure of plasticized starch, and dependence of crystalline type and degree of crystallinity mainly on the plasticizer composition and storage time. Dynamical mechanical analysis (DMA) yields a decrease of the peak intensity of loss factor with aging time. The effect of ageing on tensile strength also appears to be highly dependent on the plasticizer composition. Thus, through different plasticizer combinations and ageing, starch-based materials with significant differences in tensile properties can be obtained, which may be tuned to meet the requirements of a wide range of applications.

Residence Time Distribution in a High Shear Twin Screw Extruder

Abstract The residence time distributions (RTD) of a high shear twin screw extruder were measured by an on–line UV fluorescence device. First, by increasing throughput (Q) and screw speed (N), a decrease of the complex viscosity of the studied polypropylene (PP) was observed, revealing chain scissions. It was associated to high viscous dissipation taking place during extrusion, and more particularly under high shear conditions. Then the impact of these experimental conditions on the RTD was carried out. As expected, an increase of usual throughputs and screw speeds decrease mostly the RTD characteristic data. In this study industrial rate have been studied: throughput varied from 1.5 up to 22 kg h−1 and screw speed varied from 200 min−1 up to 1 200 min−1. However, by increasing the screw speed over usual values (from 500 up to 1 200 min−1), the variation of some experimental RTD characteristics were unexpected. Indeed, the slope of the shape of the experimental RTD function E(t) changed significantly. This phenomenon will be called lag or delay time. This result was only observed at low throughputs and high screw rotation speeds. To finish, a modeling software of twin screw extrusion process was used to compare experimental and calculated results. For usual processing conditions (up to 700 min−1), the simulation predicts nicely the experimental RTDs. However, at high screw speed (N > 800 min−1) and moderate throughput (Q = 4 kg h−1), the simulation fails to predict the RDT delay time. Hence, some side effects apparently occurred during high shear extrusion at low throughputs.

Characterization of Extruded and Toasted Milk Protein Concentrates

Important functional properties of milk protein concentrate with 80% protein (MPC80), modified with low- and high-shear extrusion, or low-temperature toasting were compared. The effect of high- and low-shear profile screws in a corotating twin-screw extruder, and 4 different ramped temperature profiles with die temperatures of 65, 75, 90, and 120 °C were compared. Extrudates were pelletized, dried, and ground to a fine powder. Toasting was done at 75 and 110 °C for 4 h for milk protein modification. Extruded and toasted MPC80 had reduced protein solubility and surface hydrophobicity. Extrusion decreased water-holding capacity (WHC). Toasted MPC80 had increased WHC when treated at 75 °C, but WHC decreased when heated at 110 °C. The treatments had no strong influence on gel strength. Reduced and nonreduced sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed peptide structural changes that occurred due to processing, especially for whey proteins. Results are discussed in terms of potential for application of extruded or toasted MPC80 in high-protein nutrition bar applications.

Improved ceramics leading to microtubular Solid Oxide Fuel Cells (mSOFCs)

Two methods for improving ceramics in SOFCs are contrasted: first, the strengthening of the cell materials through control of nanoparticle aggregation during ceramic processing; second, the design of tubular cells and stacks with smaller diameters to avoid thermal shock damage.Nanoparticle aggregation is a natural process within a fluid dispersion of the ceramic grains, caused by the attractions of weak van der Waals forces which cause clumping to occur. Large aggregates are shown to act as defects which initiate cracks at low stress. By adding polymer and using high shear extrusion, the strength of zirconia was increased by a factor 4 compared to material prepared by conventional powder pressing methods.A much larger improvement, a factor 1000, was demonstrated by reducing the tube diameter from 25 mm to 6 mm then to 2 mm. The start-up time was thereby improved from 10 h to 22 min to less than 1 min, demonstrating that the thermal shock resistance of mSOFCs could be controlled more satisfactorily through cell design than from ceramic processing.Tests on a 250 We mSOFC system have shown that the start-up is now more limited by the balance of plant issues, such as thermal inertia, preheating fuel processing catalyst and heat exchanger, rather than the ceramic thermal shock resistance properties. The advances needed to obtain 1 min start-up of an mSOFC system are discussed.