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Process Temperature (process + temperature)
Selected AbstractsComparison of chemical wet scrubbers and biofiltration for control of volatile organic compounds using GC/MS techniques and kinetic analysisJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2005James R Kastner Abstract Increasing public concerns and EPA air regulations in non-attainment zones necessitate the remediation of volatile organic compounds (VOCs) generated in the poultry-rendering industry. Wet scrubbers using chlorine dioxide (ClO2) have low overall removal efficiencies due to lack of reactivity with aldehydes. Contrary to wet scrubbers, a biofilter system successfully treated the aldehyde fraction, based on GC/MS analysis of inlet and outlet streams. Total VOC removal efficiencies ranged from 40 to 100% for the biofilter, kinetic analysis indicated that the overall removal capacity approached 25 g m,3 h,1, and aldehyde removal efficiency was significantly higher compared with chemical wet scrubbers. Process temperatures monitored in critical unit operations upstream from the biofilter varied significantly during operation, rising as much as 30 °C within a few minutes. However, the outlet air temperature of a high intensity scrubber remained relatively constant at 40 °C, although the inlet air temperature fluctuated from 50 to 65 °C during monitoring. These data suggest a hybrid process combining a wet scrubber and biofilter in series could be used to improve overall VOC removal efficiencies and process stability. Copyright © 2005 Society of Chemical Industry [source] Influence of Processing Temperature on Microcellular Injection-Moulded Wood,Polypropylene CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Andrzej K. Bledzki Abstract Summary: Microcellular wood fibre reinforced polymer materials are significant because of their possibility to reduce the density of automotive components through microcellular structure, process and product part advantages, and as a new development with bio-fibre strengthened plastics. Soft wood fibre reinforced PP composites in box part and panel shape were prepared by an injection moulding process. Polymeric microspheres as a chemical foaming agent (endothermic) were used to produce the microcellular composites. The influence of injection moulding processing temperature on the microcellular structure and properties (tensile and flexural properties, notched charpy impact strength) was investigated by varying the temperature over the 150,170,°C, 160,180,°C and 170,190,°C. A comparative study of cell morphology, weight reduction and mechanical properties was conducted between box part and panel. Microcell morphology, cell size, shape and distribution were investigated using scanning electron micrographs. The results indicated that the lower processing temperature should be below the range of 170,190,°C and processing temperature at 160,180,°C, where the composites showed finer cellular structure compared to other processing temperatures. The mechanical properties did not differ with the variation of processing temperature regardless of composite types (box part or panel). Cellular structure changes in the box part were found considering near or far from injecting point. Microcellular injection-moulded box part (geometry: 150,×,100,×,70 mm3 in size) of soft wood fibre,PP composites. [source] The effect of addition of calcium and processing temperature on the quality of guava in syrupINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2006Ana Carla K. Sato Summary The effect of process temperature and calcium concentration in the cooking syrup of guava in syrup were studied. A central composite rotatable design (CCRD) was used to optimize the quality indices of the final product, such as texture and colour. All of the processed guava quality parameters were compared with those of the fresh fruit and of a commercial sample to evaluate the effects of processing on the final product quality. Increase in the process temperature promoted changes in the final product colour, the fruit becoming darker. On the contrary, higher calcium concentrations in the cooking syrup produced lighter samples, with colour parameters closer to those of the fresh fruit. In general, the addition of calcium promoted better texture and minimized the negative effects of temperature on the mechanical properties. Processed guavas had higher rupture stress and strain than fresh fruit, indicating an increase in hardness and elasticity. [source] Rheological behaviour and colour changes of ginger paste during storageINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2004Jasim Ahmed Summary Ginger paste was prepared from fresh ginger by addition of 8% common salt and citric acid. The paste was thermally processed and packed in glass, polyethyleneterephthalate or high-density-polyethylene containers and stored at 5 ± 1 and 25 ± 1 °C for 120 days. The rheological characteristics of the paste were studied by using a computer controlled rotational viscometer over the temperature range of 20,80 °C. Samples were subjected to a programmed shear rate, increasing linearly from 0 to 200 s,1 in 3 min, followed by a steady shear at 200 s,1 for 3 min and finally decreasing linearly from 200 to 0 s,1 in 3 min. Ginger paste exhibited pseudoplasticity with yield stress and flow adequately described by the Herschel,Bulkley model. The yield stress decreased exponentially with process temperature and ranged between 3.86 and 27.82 Pa. The flow behaviour index (n) varied between 0.66 and 0.82 over the temperature range. Both consistency index and apparent viscosity decreased with increase in temperature and the process activation energies were found to be in the range of 16.7 to 21.9 kJ mol,1. The effect of temperature was significant (P < 0.05) on the Hunter colour combination value of the paste during storage; however it was not affected by type of packaging material (P > 0.05). It is recommended that ginger paste is stored at 5 ± 1 °C in polyethyleneterephthalate or glass containers. [source] INACTIVATION OF STAPHYLOCOCCUS AUREUS EXPOSED TO DENSE-PHASE CARBON DIOXIDE IN A BATCH SYSTEMJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2009HUACHUN HUANG ABSTRACT The inactivation of Staphylococcus aureus exposed to dense-phase carbon dioxide (DPCD) was investigated, and the kinetics of come-up time (CUT) in pressurization was monitored with come-down time (CDT) and temperature fluctuation in depressurization. CUT was about 2.5, 3.5, 4.0 and 4.0 min; CDT was 3.4, 3.7, 4.5 and 4.5 min; lowest temperature of samples in depressurization was 4, ,1, ,15 and ,22C, corresponding to 10, 20, 30 and 40 MPa at 37C. The inactivation behavior of S. aureus was closely related to the variables of process pressure, holding-pressure time (HPT), process temperature and process cycling. The log reduction of S. aureus at 40 MPa for 30-min HPT was significantly greater (P < 0.05), but the inactivation effect at 10, 20 and 30 MPa was similar. The log reduction of S. aureus at 30 and 40 MPa for 60-min HPT was similar and significantly greater (P < 0.05), while the inactivation effect at 10 and 20 MPa was similar. The inactivation of S. aureus against HPT conformed to a fast,slow biphase kinetics; the two stages were well fitted to a first-order model with higher regression coefficients R2 = 1.000 and 0.9238; their respective D values (decimal reduction time) were 16.52 and 70.42 min. As the process temperature increased, the log reduction of S. aureus increased significantly (P < 0.05); the inactivation kinetics of S. aureus versus process temperature was characterized with a fast inactivation rate from 32 to 45C and a slow inactivation rate from 45 to 55C. As compared to one-process cycling for a total of 60-min HPT, four-process cycling resulted in a significant reduction of S. aureus, and its maximal reduction was near to 5 log cycles, indicating that more process cycling caused more inactivation of S. aureus under identical pressure and temperature with equal HPT. However, the maximal reduction was 0.09 and 0.12 log cycles for two- and four-process cyclings with 0-min HPT, indicating that pressurization and depressurization had a lesser effect on the inactivation of S. aureus, while HPT was significant in DPCD to inactivate S. aureus. PRACTICAL APPLICATIONS Dense-phase carbon dioxide (DPCD) is a novel technology to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. This study showed that DPCD effectively inactivated Staphylococcus aureus inoculated in 7.5% sodium chloride broth, and the inactivation behavior of S. aureus was closely related to the pressure, holding-pressure time, temperature and process cycling. Based on this observation, the technology of DPCD can be applied in the pasteurization of foods such as milk and various fruit juices, especially thermal-sensitive materials. [source] Effect of Equivalent Thermal Treatments on the Color and the Antioxidant Activity of Tomato PureeJOURNAL OF FOOD SCIENCE, Issue 9 2002M. Anese ABSTRACT: The influence of different heat treatments on color and antioxidant properties of tomato purees was investigated. The treatments were designed to produce the same total thermal effect against spoilage microorganisms. Although the development of nonenzymatic browning reactions occurred by increasing process temperature, no changes in redness were observed in the heated samples, due to the "masking" effect of lycopene. Also, the heat treatments had equivalent effect on the chain-breaking activity of the aqueous and lycopene tomato fractions. However the redox potential values increased as the heating temperature increased. All data together showed that the thermal resistance constant z values for color and chain-breaking activity were close to 10°C, but lower than 10°C for reducing properties. [source] Reinforcement of Biodegradable Poly(DL -lactic acid) Material by Equal-Channel Angular ExtrusionMACROMOLECULAR SYMPOSIA, Issue 1 2006Hongxiang Cui Abstract The purpose of this study was to reinforce biodegradable poly(DL -lactic acid) (PDLLA) material using a new method, equal-channel angular extrusion (ECAE). Different processing parameters, including the number of extrusion passes and the process temperature, were investigated to analyze their effect on the PDLLA properties. Experimental results indicate that the mechanical strength of PDLLA increased with the number of extrusion passes. The extrusion temperature also affected the mechanical strength of the PDLLA. After two ECAE passes, the bending strength of PDLLA increased from 83.3 to 178.7 MPa. The bending fracture mode for PDLLA changed from brittle failure for initial specimens to ductile fracture after ECAE processing. SEM micrographs showed that the longitudinal split surfaces of PDLLA are of a fibrillar structure. Taken together, the results suggest that ECAE might represent a useful approach for the preparation of reinforced PDLLA. [source] Passivation study of the amorphous,crystalline silicon interface formed using DC saddle-field glow dischargePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010Barzin Bahardoust Abstract The DC saddle-field (DCSF) glow discharge method was used to deposit intrinsic a-Si:H onto c-Si to passivate the c-Si surface. The effective minority carrier lifetime in the heterostructures as a function of the excess minority carrier density in the c-Si wafers was measured. The results were then analyzed in the context of recombination associated with interface defect states using three known recombination models. The defect density and the charge density at the interface are inferred. In addition subsequent annealing of the samples was studied. It is shown that for our intrinsic a-Si:H samples improvements in surface passivation are directly correlated with the reduction of interface defects and not the reduction of minority carrier concentration at the interface due to electric field. We have achieved excellent surface passivation with effective carrier lifetime >4,ms for an intrinsic a-Si:H sample deposited at a process temperature of 200,°C and thickness of about 30,nm. It is also demonstrated that subsequent annealing, at 240,°C, of the samples which were prepared at process temperatures <240,°C greatly increases the effective lifetime. [source] Effect of Illite Clay and Divalent Cations on Bitumen RecoveryTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2006Xinlin Ding Abstract The adverse effect of illite clay on bitumen recovery was found to be related to its acidity. The addition of calcium or magnesium ions to the flotation deionized water had a marginal effect on bitumen recovery when measured using a Denver flotation cell. However, the co-addition of illite clay and divalent cations caused a significant reduction in bitumen recovery. The effect was found to be compounded at a lower process temperature and low pH values. Zeta potential distributions of illite suspensions and bitumen emulsions were measured individually and as a mixture to investigate the effect of divalent cations on the interaction between bitumen and illite clay. The presence of 1 mM calcium or magnesium ions in deionized water had a significant effect on the interactions between bitumen and illite clay. Slime coating of illite onto bitumen was not observed in zeta potential distribution measurements performed in alkaline tailings water. On a trouvé que l'effet adverse de l'argile d'illite sur la récupération de bitume était relié à son acidité. L'ajout d'ions de calcium ou de magnésium à l'eau déionisée de flottation a un effet marginal sur la récupération de bitume lorsqu'on la mesure avec une cellule de flottation de Denver. Toutefois, l'ajout combiné d'argile d'illite et de cations divalents entraîne une réduction significative de la récupération de bitume. On a trouvé que les effets étaient combinés à une faible température de procédé et de faibles valeurs de pH. Les distributions de potentiel zéta des suspensions d'illite et des émulsions de bitume ont été mesurées individuellement et dans le mélange afin d'étudier les effets des cations divalents sur l'interaction entre le bitume et l'argile d'illite. La présence de 1 mM d'ions de calcium ou de magnésium dans l'eau déionisée a un effet significatif sur les interactions entre le bitume et l'argile d'illite. On n'a pas observé de couche de boues d'illite sur le bitume dans les mesures de distributions de potentiel zéta obtenues dans de l'eau de rejets alcaline. [source] Ethanol production from paper sludge by simultaneous saccharification and co-fermentation using recombinant xylose-fermenting microorganismsBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010Jiayi Zhang Abstract Simultaneous saccharification and co-fermentation (SSCF) of waste paper sludge to ethanol was investigated using two recombinant xylose-fermenting microbes: Zymomonas mobilis 8b and Saccharomyces cerevisiae RWB222. S. cerevisiae RWB222 produced over 40,g/L ethanol with a yield of 0.39,g ethanol/g carbohydrate on paper sludge at 37°C, while similar titers and yields were achieved by Z. mobilis 8b at 30°C. Both S. cerevisiae RWB222 and Z. mobilis 8b exhibited decreasing cell viability at 37°C when producing over 40,g/L ethanol. A high ethanol concentration can account for S. cerevisiae RWB222 viability loss, but ethanol concentration was not the only factor influencing Z. mobilis 8b viability loss at 37°C. Over 3,g/L residual glucose was observed at the end of paper sludge SSCF by Z. mobilis 8b, and a statistical analysis revealed that a high calcium concentration originating from paper sludge, a high ethanol concentration, and a high temperature were the key interactive factors resulting in glucose accumulation. The highest ethanol yields were achieved by SSCF of paper sludge with S. cerevisiae RWB222 at 37°C and Z. mobilis 8b at 30°C. With good sugar consumption at 37°C, S. cerevisiae RWB222 was able to gain an improvement in the polysaccharide to sugar yield compared to that at 30°C, whereas Z. mobilis 8b at 30°C had a lower polysaccharide to sugar yield, but a higher sugar to ethanol yield than S. cerevisiae. Both organisms under optimal conditions achieved a 19% higher overall conversion of paper sludge to ethanol than the non-xylose utilizing S. cerevisiae D5A at its optimal process temperature of 37°C. Biotechnol. Bioeng. 2010;107: 235,244. © 2010 Wiley Periodicals, Inc. [source] "Enzyme Test Bench," a high-throughput enzyme characterization technique including the long-term stabilityBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Kirill Rachinskiy Abstract A new high throughput technique for enzyme characterization with specific attention to the long term stability, called "Enzyme Test Bench," is presented. The concept of the Enzyme Test Bench consists of short term enzyme tests in 96-well microtiter plates under partly extreme conditions to predict the enzyme long term stability under moderate conditions. The technique is based on the mathematical modeling of temperature dependent enzyme activation and deactivation. Adapting the temperature profiles in sequential experiments by optimal non-linear experimental design, the long term deactivation effects can be purposefully accelerated and detected within hours. During the experiment the enzyme activity is measured online to estimate the model parameters from the obtained data. Thus, the enzyme activity and long term stability can be calculated as a function of temperature. The engineered instrumentation provides for simultaneous automated assaying by fluorescent measurements, mixing and homogenous temperature control in the range of 10,85,±,0.5°C. A universal fluorescent assay for online acquisition of ester hydrolysis reactions by pH-shift is developed and established. The developed instrumentation and assay are applied to characterize two esterases. The results of the characterization, carried out in microtiter plates applying short term experiments of hours, are in good agreement with the results of long term experiments at different temperatures in 1 L stirred tank reactors of a week. Thus, the new technique allows for both: the enzyme screening with regard to the long term stability and the choice of the optimal process temperature regarding such process parameters as turn over number, space time yield or optimal process duration. The comparison of the temperature dependent behavior of both characterized enzymes clearly demonstrates that the frequently applied estimation of long term stability at moderate temperatures by simple activity measurements after exposing the enzymes to elevated temperatures may lead to suboptimal enzyme selection. Thus, temperature dependent enzyme characterization is essential in primary screening to predict its long term behavior. Biotechnol. Bioeng. 2009;103: 305,322. © 2008 Wiley Periodicals, Inc. [source] Enzymatic production of ,- D -glucose-1-phosphate from trehaloseBIOTECHNOLOGY JOURNAL, Issue 9 2010Jef Van der Borght Abstract ,- D -Glucose-1-phosphate (,Glc1P) is an efficient glucosyl donor for both enzymatic and chemical glycosylation reactions but is currently very costly and not available in large amounts. This article provides an efficient production method of ,Glc1P from trehalose and phosphate using the thermostable trehalose phosphorylase from Thermoanaerobacter brockii. At the process temperature of 60°C, Escherichia coli expression host cells are lysed and cell treatment prior to the reaction is, therefore, not required. In this way, the theoretical maximum yield of 26% could be easily achieved. Two different purification strategies have been compared, anion exchange chromatography or carbohydrate removal by treatment with trehalase and yeast, followed by chemical phosphate precipitation. In a next step, ,Glc1P was precipitated with ethanol but this did not induce crystallization, in contrast to what is observed with other glycosylphosphates. After conversion of the product to its cyclohexylammonium salt, however, crystals could be readily obtained. Although both purification methods were quantitative (>99% recovery), a large amount of product (50%) was lost during crystallization. Nevertheless, a production process for crystalline ,Glc1P is now available from the cheap substrates trehalose and inorganic phosphate. [source] Barium Sulfate Crystallization Kinetics in the Used Quenching Salts Treatment ProcessCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2004A. Matynia Abstract The research results and kinetic studies on the barium ions precipitation process by means of crystalline ammonium sulfate addition are presented. The influence of: barium, sodium, potassium and calcium chlorides concentration in the feeding solution and also the process temperature on barium sulfate mass crystallization kinetics are investigated. Experiments were carried out in the MSMPR crystallizer with internal circulation of suspension. The barium sulfate nucleation and crystal growth rates were estimated from crystal size distribution taking into account a size dependent growth (SDG). Research results may be utilized in the used quenching salts processing technology. [source] Atomic Layer Deposition of BaTiO3 Thin Films,Effect of Barium Hydroxide FormationCHEMICAL VAPOR DEPOSITION, Issue 5 2007M. Vehkamäki Abstract Barium titanate thin films are grown by atomic layer deposition (ALD) at 340,°C from barium cyclopentienyl and titanium methoxide precursors. H2O is used as the oxygen source. Binary reactions of Ba(tBu3C5H2)2 and H2O are first studied separately in BaO deposition and are found to result in a hydration/dehydration cycle, which is strongly influenced by the process temperature. Self-limiting growth of amorphous barium titanate films becomes possible when Ti(OMe)4 , H2O growth cycles are mixed as well as possible with Ba(tBu3C5H2)2 , H2O cycles. The as-deposited amorphous films are crystallized by post-deposition annealing at 600,°C. Permittivities of 15 and 70 are measured for as-deposited and post-deposition annealed films, respectively. A charge density of 1.9 ,C cm,2 (equivalent oxide thickness of 1.8,nm) and leakage current density ,,1,×,10,7,A,cm,2 were achieved at 1,V bias with a 32,nm thick Ba,Ti,O film in a Pt electrode stack annealed at 600,°C. [source] Characterization of Aroma-Active Compounds in Microwave Blanched PeanutsJOURNAL OF FOOD SCIENCE, Issue 9 2006A.V. Schirack ABSTRACT:, Microwave blanching of peanuts has been explored as an alternative to conventional oven methods based on its speed of operation, energy savings, and efficiency of process control. Although processing times can be greatly reduced, the occurrence of stale/floral and ashy off-flavors has been reported at high process temperatures. This study examined the chemical compounds responsible for this off-flavor using solvent extraction/solvent assisted flavor evaporation (SAFE), gas chromatography-olfactometry (GC/O), gas chromatography-mass spectrometry (GC/MS), and aroma extract dilution analysis (AEDA). Select compounds were quantified based on AEDA results using SAFE and GC/MS. Quantification, threshold testing, and analysis of model systems revealed increased formation of guaiacol and phenylacetaldehyde in the off-flavored peanuts, which resulted in the burnt and stale/floral flavors noted by a trained panel. [source] Stabilization of vinyl chloride/vinylidene chloride copolymers using N-substituted maleimides,JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2006Bob A. Howell As a consequence of their excellent barrier properties, vinyl chloride/vinylidene chloride copolymers have long been prominent in the flexible packaging market. While these polymers possess a number of superior characteristics, they tend to undergo thermally induced degradative dehydrochlorination at process temperatures. This degradation must be controlled to permit processing of the polymers. Three series of N-substituted maleimides (N -alkyl-, N -aralkyl-, and N -aryl-) have been synthesized, characterized spectroscopically, and evaluated as potential stabilizers for a standard vinyl chloride/vinylidene chloride (85 wt%) copolymer. As surface blends with the polymer, these compounds are ineffective as stabilizers. However, significant stabilization may be achieved by pretreatment of the polymer with N-substituted maleimides. The most effective stabilization of the polymer is afforded by N -aralkyl- or N -arylmaleimides, most notably, N -benzylmaleimide and N -(p -methoxyphenyl)maleimide. J. VINYL. ADDIT. TECHNOL. 12:88,97, 2006. © 2006 Society of Plastics Engineers. [source] Stress corrosion cracking susceptibility of stainless steels in pulp cooking processes,online capillary electrophoresis, potentiostatic and chromatographic studiesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2008H. Leinonen Abstract An online high temperature capillary electrophoresis instrument (HotUCE), a potentiometer and an ion chromatograph were used in studies on corrosive ions and changes in potential at normal pulping process temperatures in experimental liquors modelling pulp cooking processes at mills. The aim was to evaluate the stress corrosion cracking (SCC) susceptibility of stainless steels. The HotUCE instrument and the potentiometer were online coupled with an autoclave, where welded duplex stainless steel samples were immersed for 500 h in simulated high ionic strength hot black liquor (HBL), hot white liquor (HWL) or green liquor (GL) at 130, 150 or 170,°C, respectively. The results showed that only minor amounts of oxidized sulphur compounds were formed. The concentrations of corrosive sulphur anions were calculated against sulphur standards. Amounts of sulphur species in the liquor correlated with the changes in the potential of the duplex stainless steel specimens during the cooking experiments. The formation of sulphite during cooking was greater in HWL than in HBL. Changes in the potential showed that reduction processes occurred during the SCC tests. The results indicate that the SCC risk is enhanced at higher temperatures, probably, due to the increased formation of thiosulphate. [source] Passivation study of the amorphous,crystalline silicon interface formed using DC saddle-field glow dischargePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010Barzin Bahardoust Abstract The DC saddle-field (DCSF) glow discharge method was used to deposit intrinsic a-Si:H onto c-Si to passivate the c-Si surface. The effective minority carrier lifetime in the heterostructures as a function of the excess minority carrier density in the c-Si wafers was measured. The results were then analyzed in the context of recombination associated with interface defect states using three known recombination models. The defect density and the charge density at the interface are inferred. In addition subsequent annealing of the samples was studied. It is shown that for our intrinsic a-Si:H samples improvements in surface passivation are directly correlated with the reduction of interface defects and not the reduction of minority carrier concentration at the interface due to electric field. We have achieved excellent surface passivation with effective carrier lifetime >4,ms for an intrinsic a-Si:H sample deposited at a process temperature of 200,°C and thickness of about 30,nm. It is also demonstrated that subsequent annealing, at 240,°C, of the samples which were prepared at process temperatures <240,°C greatly increases the effective lifetime. [source] Nucleation and Expansion During Extrusion and Microwave Heating of Cereal FoodsCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 4 2003C.I. Moraru ABSTRACT Expansion of biopolymer matrices is the basis for the production of a wide variety of cereal foods. A limited number of manufacturing processes provide practical solutions for the development of an impressive variety of expanded products, just by changing process variables. It is therefore essential that the mechanisms involved in expansion are well known and controlled. This paper summarizes the knowledge of nucleation and expansion in extruded and microwaved products available to date. The effect of processing conditions and properties of the biopolymeric matrix on nucleation and expansion are discussed. Moisture content enables the glassy polymeric matrix to turn into rubbery state at process temperatures, which allows superheated steam bubbles to form at nuclei and then expand, expansion being governed by the biaxial extensional viscosity of the matrix. Nucleation and expansion theories are presented along with quantitative data that support them. [source] | ||||||||||||||||||||||||||||