Thermal Processing Conditions Research Articles

Simultaneously Controllable Doping Sites and the Activity of a W–N Codoped TiO2 Photocatalyst

Tungsten–nitrogen (W–N) codoping has been known to enhance the photocatalytic activity of anatase TiO2 nanoparticles by utilizing visible light. The doping effects are, however, largely dependent on calcination or annealing conditions, and thus, the massive production of quality-controlled photocatalysts still remains a challenge. Using density functional theory (DFT) thermodynamics and time-dependent DFT computations (TDDFT), we investigate the atomic structures of N doping and W–N codoping in anatase TiO2, as well as the effect of the thermal processing conditions. We find that W and N dopants predominantly constitute two complex structures: an N interstitial site near a Ti vacancy in the triple charge state ((VTi-Ni)3–) and the simultaneous substitutions of Ti by W and the nearest O by N ((WTi-NO)+). The latter case induces highly localized shallow in-gap levels near the conduction band minimum (CBM) and the valence band maximum (VBM), whereas the (VTi-Ni)3– defect complex yielded deep levels (1.9 eV a...

Optimization of thermal processing conditions for brown rice noodles

Based on the current thermal processing conditions for rice noodles (80–85 °C for 20–30 min), we used response surface methodology to find brown rice (BR) noodle processing conditions that maximize the noodles antioxidant activity, digestibility, and gelatinization. The experiments were designed according to the central composite design, including two independent variables (temperature and time) and six dependent variables [total phenolic contents (TPC), total flavonoid contents (TFC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activities, digestibility, and gelatinization]. Antioxidant activities decreased but digestibility and gelatinization increased with increasing temperature and time. All dependent variables suggested a quadratic model except TFC, but the probability of TPC was not applicable (0.1505), and DPPH radical scavenging activity showed a relatively low R 2 (0.6750). Therefore, we applied the other three dependent variables (ABTS radical scavenging activity, digestibility, and gelatinization) to the 3D response surface and proposed three optimum conditions: (1) for antioxidant activity (70 °C, 22.95 min), (2) for digestibility and gelatinization (88.18 °C, 34.89 min), and (3) for all three variables (88.5 °C, 40 min). In a validation test, all dependent variables showed values within a 5 % error range except TFC. These results show the optimum processing conditions for BR noodles to maximize antioxidant activity and provide sustainability in BR noodle processing.

Mechanical properties of radiation cross linked polyamide 12 after vacuum thermoforming

Generally semi-crystalline thermoplastics have an inferior thermoformability compared to amorphous thermoplastics. This is because of their sharp drop in stiffness and viscosity with crystalline melting. Radiation cross-linking of semi-crystalline thermoplastics offers a solution for this limitation. The thermoformability is essential for processing, but the parts properties like the mechanical ones are important for the application of thermoformed parts. In this article the effects of mold geometry and temperature, forming temperature and film thickness on the mechanical properties of thermoformed cross-linked polyamide 12 (PA12) are investigated. The results show the improvement of the thermoformability of semi-crystalline thermoplastics by cross-linking. Concerning the mechanical properties of the parts, a significant enhancement in stiffness and tensile strength can be obtained, while the ultimate strain at break decreases compared to the smooth film’s properties. Thermal processing conditions, deformations during forming and the degree of cross-linking of the film material have an influence on these effects.

DTA를 통한 LAS계 투명 결정화 유리의 결정화 조건 최적화

The basic characteristics of glass are highly fragile and brittle consequences the ultimate purpose of glass manufacturing is to make a transparent glass with complex shape. In order to solve this problem, mechanical properties of glass can be increased by crystallization of its amorphous glass. However, glass-ceramics has become opaque through crystallization process due to the distracted interface of glass by precipitated particles. This study has been investigated thermal processing conditions of LAS transparent glass-ceramic by using DTA (differential thermal analysis), in order to control size of precipitated particle and then fabricate transparent glass-ceramic. DTA indicated that crystallization peak area was declined with increased nucleation temperature. Subsequently, we have been established optimum temperature for crystallization depending on the nucleation temperature. The transmission and thermal expansion were measured after crystallization, and the size of precipitated particle was identified in range of 20~100 nm by FE-SEM. In addition, by setting the optimized crystallization condition, with high transmission and low thermal expansion glass was synthesized through this experiment.

Enhanced dielectric and piezoelectric properties of 0–3 PZT/PVDF composites

Flexible piezoelectric composite films of ([PZT/]x/[PVDF]1-x (x = 0, 0.1, 0.2, 0.3) with 0–3 connectivity were synthesized from 0.2 wt% Li2CO3 added PZT ceramic powders in the morphotropic phase boundary (MPB) and PVDF polymer by solution cast technique under optimized thermal processing conditions. It is seen that crystallinity and β phase are enhanced with the addition of Li in the composite films and as well as with the volume content of PZT ceramics in PVDF matrix, thereby resulting in superior dielectric and piezoelectric properties. It is also seen that reasonably high dielectric and piezoelectric properties are obtained for 30 % of the volume content of PZT ceramics as compared to 50 % of the volume content of ceramic in the polymer matrix as reported in literature and hence, the flexibility is better in these films.

Formation of tree-like and vortex magnetic domains of nanocrystalline α-(Fe,Si) in La–Fe–Si ribbons during rapid solidification and subsequent annealing

The characteristic magnetic domains at the surfaces of melt-spun La–Fe–Si ribbons under different thermal processing conditions are explored using room-temperature Lorentz force microscopy and electron holography. In as-quenched ribbons, the magnetic domain structure is found to change from a tree-like morphology on the surface far from the copper wheel during quenching to a vortex-type domain structure on the surface in contact with the wheel. In the initial stages of annealing, domains on both surfaces developed a vortex behavior. Detailed microstructural observations demonstrated nanocrystalline α-(Fe,Si) regions embedded in the majority La(Fe,Si)13 phase due to a partially completed peritectoid reaction between α-(Fe,Si) and LaFeSi. The room temperature magnetic domains disappeared along with the residual α-(Fe,Si) upon extended heat treatment, yielding a homogeneous La(Fe,Si)13 material. Magnetometry measurements and analysis reveal the absence of strong coupling between the α-(Fe,Si) and La(Fe,Si)13 phases, so that the presence of α-(Fe,Si) nanocrystallites with a vortex-type structure does not favor an enhanced magnetocaloric response in the ribbons.

Water activity change at elevated temperatures and thermal resistance of Salmonella in all purpose wheat flour and peanut butter

Water activity (aw) is a major factor affecting pathogen heat resistance in low-moisture foods. However, there is a lack of data for aw at elevated temperatures that occur during actual thermal processing conditions, and its influence on thermal tolerance of pathogens. The objective of this study was to gain an in-depth understanding of the relationship between temperature-induced changes in aw and thermal resistance of Salmonella in all purpose flour and peanut butter at elevated temperatures (80 oC). Equilibrium water sorption isotherms (water content vs. water activity) for all purpose wheat flour and peanut butter over the range of 20 to 80°C were generated using a vapor sorption analyzer and a newly developed thermal cell. The thermal resistance (D80-values) of Salmonella in all purpose wheat flour and peanut butter with initial aw of 0.45 (measured at room temperature, ~20°C) was determined via isothermal treatment of small (<1g) samples. When increasing sample temperature from 20 to 80°C in sealed cells, the aw of all purpose flour increased from 0.45 to 0.80, but the aw of peanut butter decreased from 0.45 to 0.04. The corresponding estimated D80-values of Salmonella in all purpose flour and peanut butter with 20 oC aw of 0.45 were 6.9±0.7min and 17.0±0.9min, respectively. The significantly (P<0.05) higher D80-value of Salmonella in peanut butter than in all purpose flour may be partially attributed to the reduced aw in peanut butter in comparison to the increased aw in all purpose flour at 80°C. The improved understanding of temperature-induced changes in aw of low-moisture products of different composition provides a new insight into seemly unpredictable results, when using heat treatments to control Salmonella in such food systems.

Standardization of thermal processing of cuttlefish nidamental gland

Cuttlefish nidamental gland was blanched in boiling 5 per cent brine for 2, 5, 10 and 15 minutes to standardise the blanching condition. The sample blanched for 5 minutes was found to have the best sensory qualities. Sub-sequently, glands blanched under these standardised conditions were packed in cans in brine and were subjected to thermal processing in a retort. Thermal processing conditions were standardised by processing the cans under different retorting conditions. Out of these, the retorting temperature and the process time of 121.1°C and 25 minutes, respectively was found to be the best with respect to sensory qualities and could produce a commercially sterile product. The F o value attained by the process was 11.25 minutes with a total process time of 30.54 minutes. The storage study of the product over a period of three months showed that it has good stability at ambient condition and has a shelf-life of more than three months. The present investigation delineates that cuttlefish nidamental gland can be used for the production of ready-to-eat thermally processed product, which can be stored at room temperature for long periods.

Insoluble and soluble roasted walnut proteins retain antibody reactivity

Thermal processing techniques commonly used during food production have the potential to impact food allergens by inducing physical and/or chemical changes to the proteins. English walnuts (Juglans regia) are among the most commonly allergenic tree nuts, but little information is available regarding how walnut allergens respond to thermal processing. This study evaluated the effects of dry roasting (132 or 180°C for 5, 10, or 20min) on the solubility and immunoreactivity of walnut proteins. A dramatic decrease in walnut protein solubility was observed following dry roasting at 180°C for 20min. However, both the soluble and insoluble protein fractions from roasted walnuts maintained substantial amounts of IgG immunoreactivity (using anti-raw and anti-roasted walnut antisera), with similar patterns of reactivity observed for human IgE from walnut-allergic individuals. Thus, walnut proteins are relatively stable under certain thermal processing conditions, and IgE reactivity remains present even when insoluble aggregates are formed.

Effect of pulsed electric field and pasteurisation treatments on the rheological properties of mango nectar (Mangifera indica)

processing. The rheological parameter shear stress was measured up to the shear rate of 750 s -1 using co-axial cylinder attachment at wide range of temperatures from 10 to 70 °C. The investigation showed that pulsed electric field (PEF) processed and thermally pasteurised mango nectar behaved like a pseudo plastic (shear thinning) fluid and obeyed Herschel-Bulkley model (0.9780 0.893, p < 0.05) and flow activation energy (Ea) was significantly (p < 0.05) affected by processing conditions. The results indicated that the pulsed electric field (PEF) and thermal processing condition has affected the rheological properties of mango nectar. The combined equation relating to shear stress (τ) with temperature and shear rate of mango nectar was established.

Austenite–ferrite transformation in enhanced niobium, low carbon steel

The austenite to ferrite transformation characteristics of a commercial high strength line pipe steel containing 0·05 wt-% carbon and 0·095 wt-% niobium have been rigorously studied by continuous cooling experiments in the range between 960 and 1260°C. A significant delay in the austenite to allotriomorphic ferrite transformation has been demonstrated to occur under practically relevant thermal processing conditions. The effects of prior austenite grain size and soluble niobium have been carefully evaluated and isolated and it has been concluded that the amount of niobium in solution in the austenite is primarily responsible for the retardation. Alternative hypotheses to explain the mechanism whereby niobium exerts this effect on the hardenability of steel are discussed in detail. Soluble niobium reducing the austenite grain boundary energy is argued to be the most convincing explanation of the phenomenon and a reduction of grain boundary energy of 0·286 J m−2 per wt-% of soluble niobium content has been proposed.

Evaluation of the viscosity profile obtained for dispersions containing different proportions of milk protein concentrate / whey protein concentrate during simulated conditions of thermal processing

Denaturation and interaction of different proteins occur in different forms and intensity when the pH value varies in accordance with the medium in which they are located. This study aimed to verify the influence of whey protein/casein interaction in the evolution of viscosity at different pH values, using the Rapid Viscosity Analyzer (RVA) as the thermal processing simulator. Samples of commercial whey protein concentrate (WPC) and milk protein concentrate (MPC) have been analyzed. The results of this study can be applied in the development of products obtained from dairy powders such as processed cheeses and yoghurt.

English

The retention of nutrient components of fruit juices during processing is an important criterion to produce better quality fruit products. Stability of nutrient components during processing vary from product to product and processing methods. Information about kinetic study of particular nutrient component under different processing conditions would enable to optimize processing parameters for better quality retention. Therefore the objective of this research was to evaluate the effect of thermal and high pressure food processing methods on stability of vitamin C and lycopene of watermelon juice. Watermelon juice was subjected to different thermal (70 to 90&deg;C) and high pressure (400 to 600 MPa) treatments for different interval of times and the residual vitamin C and lycopene concentrations were measured. The destruction of nutrients in both thermal and high pressure processing conditions obey first order reaction rate kinetic model. In both processing conditions lycopene remains more stable as compared to vitamin C. The degradation rates of both components were faster in thermal treatment as compared to high pressure. The D value of vitamin C ranged from 40 to 176 min (z = 30.8&deg;C) and 4 to 24 h (zp = 257 MPa) in thermal and high pressure treatments respectively whereas the D value of lycopene ranged from 15 to 83 h (z= 24.5oC) and 61 to 258 h (zP= 318 MPa) for thermal and high pressure treatments respectively. Therefore high pressure ensures better retention of the nutrients as compared to thermal treatment&nbsp;and hence can be used to pasteurize better quality watermelon juice. Key words: Vitamin C, lycopene, thermal, high pressure, destruction kinetics, watermelon.&nbsp; &nbsp

Structural, dielectric and piezoelectric properties of 0–3 PZT/PVDF composites

Piezoelectric composite films of ([PZT]x/[PVDF]1−x) with 0–3 connectivity were prepared using a solution cast technique. The films with different volume fractions of PZT ceramics in the morphotropic phase boundary were prepared in the form of thin films for the optimized thermal processing conditions. It is seen that the increase in the content of PZT ceramic in the PVDF matrix not only increases the dielectric constant of the composites but also enhances the β phase in the PVDF polymer, thereby resulting in the overall improved dielectric and piezoelectric behavior of the system. The as-synthesized films exhibited superior dielectric and piezoelectric properties than reported in the literature.

Recombinant kiwi pectin methylesterase inhibitor: Purification and characterization of the interaction with plant pectin methylesterase during thermal and high-pressure processing

Abstract Recombinant kiwi pectin methylesterase inhibitor (rPMEI) with a six-histidine tag at the C-terminus was successfully expressed in Pichia pastoris GS115 strains. rPMEI was purified using pectin methylesterase (PME)-CNBr-affinity chromatography or nickel affinity chromatography. The purified rPMEI had a slightly higher molecular weight than the kiwi PMEI probably due to the presence of added six histidines and some glycosylation. The expression in P. pastoris did not result in changes in the inhibitory activity of rPMEI, nor did it significantly change the complexation with PME under thermal and high pressure processing conditions compared to kiwi PMEI. While thermal treatment of an equimolar PME–rPMEI complex resulted in the aggregation of PME and rPMEI as an entity, high-pressure processing led to the dissociation of PME–rPMEI complex resulting in the presence of free rPMEI after processing. The obtained results presented a viable option for utilization of recombinant PMEI for control of PME activity. Industrial relevance The discovery of a pectin methylesterase inhibitor (PMEI) in kiwi fruit opened an additional way to control PME activity, although the industrial application is inhibited by the low yield obtainable from kiwi. For a possible utilization of PMEI in large scale production, recombinant PMEI (rPMEI) was modified with an additional six-histidine tag, expressed and studied. Our results showed that the expression of rPMEI with the additional six-histidine tag allows a feasible large scale purification of the inhibitor using nickel affinity chromatography without negatively affecting the inhibitory activity nor significantly changing the complexation with PME compared to kiwi PMEI. Thus the combination of rPMEI with high-pressure treatment can be exploited to process food systems where cloud stability is of importance but the high pressure itself is insufficient to completely inhibit the PME.

Application of content optimized ZnS-ZnO-CuS-CdS heterostructured photocatalyst for solar water splitting and organic dye decomposition

Heterostructured ZnS-ZnO-CuS-CdS photocatalyst was synthesized via a sequential fabrication approach (ZnS→thermal treatment (ZnS-ZnO)→CuS formation (ZnS-ZnO-CuS)→CdS addition (ZnS-ZnO-CuS-CdS)). Each component in this heterostructure has its own role for photocatalytic reaction. The oxide content controlled by thermal processing condition is a crucial factor for improving photocatalytic activity, and the CuS and CdS contents are controlled by their feedstocks. The effects of heterostructure composition on the solar water splitting and organic dye decomposition were investigated under 1 sun irradiation (100 mW/cm2, AM 1.5G filter). The content optimized ZnS-ZnO-CuS-CdS photocatalyst produces 2452.7 μmol g−1 h−1 hydrogen, and it decomposes methyl blue much faster than the other cases. Thus, heterostructured photocatalysts can benefit the use of electrons and holes for improved photocatalytic activity.

Study of Thermal Behaviour of Milk Protein Products Using a Chemometric Approach

This study deals with the evaluation of the behavior of viscosity evolution of the Milk Protein Products (MPPs) solutions in different concentrations used in different conditions of thermal processing by means of Rapid Visco Analyzer (RVA). Skimmed milk powder (SMP), whey protein Original Research Article Stephani et al.; BJAST, 7(1): 62-83, 2015; Article no.BJAST.2015.126 63 concentrate (WPC), milk protein concentrate (MPC), whey powder (WP) and demineralized whey powder (DWP) were analyzed; the evaluated solid-liquid ratio solutions were 0.1 g∙g -1 to 0.45 g∙g -1 of dry solids in water (DSW) for the MPC, 0.1 g∙g -1 to 0.4 g∙g -1 of DSW for the WPC and 0.5 g∙g -1 to 0.8 g∙g -1 of DSW for SMP, WP and DWP. Brazilian industrial heat treatment set ups were used, with temperatures ranging from 65°C to 95°C and retention time from 5 to 30 minutes. The results were interpreted according to the viscosities during heating and cooling, being possible to optimize the MPPs different parameters conditions with the interpretations of the viscographic profiles based on the thermal behavior of proteins, especially for the SMP, MPC and WPC. The data showed similarity in viscographic characteristics of the solutions when evaluated at 65°C for 30 minutes, at 85°C for 15 minutes and 95°C for 5 minutes, for the MPC and WPC at 95°C for 5 minutes, all of them for different concentrations of proteins in water.

Structure, phases and tribological behaviour of Fe-based self-fluxing alloy coatings formed by plasma spraying and follow-up flame and laser remelting

This paper analyses the influence of the type of thermal spraying and processing conditions on the structure, phases and tribological behaviour of Fe-based self-fluxing alloy coatings. Two processes are studied: plasma spraying combined with flame remelting and plasma spraying combined with laser remelting. The type of remelting affects the structure and phases composition of Fe-based coating significantly. The laser beam velocity influences the alloy structure changes considerably. These changes affect the microhardness of the coating. The types of remelting influences the average and momentary friction coefficients as well as relative wear rates of the coating.

Impact of Pulse Thermal Processing on the Properties of Inkjet Printed Metal and Flexible Sensors

We report on the low temperature processing of environmental sensors employing pulse thermal processing (PTP) technique to define a path toward flexible sensor technology on plastic, paper, and fabric substrates. Inkjet printing and pulse thermal processing technique were used to realize mask-less, additive integration of low-cost sensors on polymeric substrates with specific focus on temperature, humidity, and strain sensors. The printed metal line performance was evaluated in terms of the electrical conductivity characteristics as a function of post-deposition thermal processing conditions. The PTP processed Ag metal lines exhibited high conductivity with metal sheet resistance values below 100 mΩ/□ using a pulse width as short as 250 μs. The flexible temperature and relative humidity sensors were defined on flexible polyimide substrates by direct printing of Ag metal structures. The printed resistive temperature sensor and capacitive humidity sensor were characterized for their sensitivity with focus on future smart-building applications. Strain gauges were printed on polyimide substrate to determine the mechanical properties of the silver nanoparticle films. The observed electrical properties of the printed metal lines and the sensitivity of the flexible sensors show promise for the realization of a high performance print-on-demand technology exploiting low thermal-budget PTP technique.

Mechanical Characterization of a Steel AISI 43100 Submitted to Different Routes of Heat Treatments

The present study aimed to explore possible thermal processing conditions of a steel AISI 43100, seeking the best combination of properties, especially strength and ductility. Different routes of heat treatments for continuous cooling were applied to the material, and the mechanical properties were evaluated by tensile and hardness tests. The microstructure and fracture micromechanisms were characterized by scanning electron microscopy (SEM). It was observed a strong influence of cooling rate on the formation of microstructure, reflecting directly in mechanical properties.