Thermal Processing Conditions Research Articles

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.

Beverage emulsions: Comparison among nanoparticle stabilized emulsion with starch and surfactant stabilized emulsions

Emulsions are widely used in beverages to impart desired appearance and flavor to the products. Ring formation in beverages with emulsions during thermal processing and storage is one of the key challenges. This study was aimed at comparing the relative effectiveness of silica nanoparticle based emulsifiers with surfactant and biopolymer based emulsifier (modified starch) in influencing physical stability of emulsions in a model juice. The stability of emulsions was measured by characterizing changes in emulsion droplet size, zeta potential, UV–vis absorbance and visual evaluation of phase separation or ring formation in both primary emulsions and beverage emulsions as a function of storage time. The influence of thermal processing on stability of emulsions both immediately after processing and upon storage was evaluated. The thermal processing conditions simulated both high temperature short time and low temperature long time pasteurization conditions. The results demonstrate that the mean droplet diameter of primary emulsions stabilized by selected emulsifiers was stable during storage for 21days with and without pasteurization. Based on measurements of mean droplet diameter and visible ring formation, polyoxyethylene sorbitan monolaurate (tween-20) stabilized emulsion was not stable in a model juice and the stability of this emulsion was further reduced with thermal processing. In contrast, starch and silica stabilized emulsions in a model juice did not show significant changes in particle diameter or visible ring formation during storage with and without prior thermal processing, although starch stabilized emulsion did show a decrease in absorbance during storage. Zeta potential measurements in a model juice indicate that the surface properties of emulsions were significantly distinct from those of primary emulsion, indicating interaction of juice components with the emulsion interface influencing the surface charge at the interface. These changes in zeta potential of emulsion droplets did not correlate with reduced stability of the emulsions. Overall, the results demonstrate that nanoparticle stabilized emulsions can improve stability of emulsion in beverages as compared to surfactant and biopolymer stabilized emulsions and provides a comprehensive matrix to evaluate stability of emulsions in beverages.

Precursor-mediated reactivity of vibrationally hot molecules: Methane activation on Ir(1 1 1)

Industrial steam reformers use temperatures greater than 1000K to activate methane dissociation. At these temperatures, typical translational energies (Etrans) are much lower than the energy threshold for reaction, but the majority of methane molecules are vibrationally excited. A combination of molecular beam techniques and state-resolved infrared laser excitation allowed us to quantify reaction probability, S0, for vibrationally excited methane in v=1 of the ν3 C–H stretching vibration (Evib=36kJ/mol) at Etrans ranging from 2 to 48kJ/mol. On a 1000K Ir(111) surface, ν3 excitation enhanced S0 at all Etrans studied, and two distinct reaction channels appeared. When Etrans>15kJ/mol, S0 increased with Etrans, as expected for direct dissociative chemisorption. When Etrans<10kJ/mol, S0 decreased as Etrans increased. The low-Etrans results are consistent with a precursor-mediated mechanism in which vibrationally excited molecules first trap on the surface, sample different adsorption geometries and surface sites, and then react prior to vibrational quenching. The direct and precursor-mediated channels have nearly identical vibrational efficacies of 0.43 and 0.42, respectively, for promoting dissociative chemisorption. Our observations point to the potentially important role that vibrationally hot precursor molecules may play under thermal reaction processing conditions.

Effect of Pasteurization and Retort Processing on Spectral Characteristics, Morphological, Thermal, Physico-Mechanical, Barrier and Optical Properties of Nylon-Based Food Packaging Materials

The effect of pasteurization and retort processing on spectral, morphological, thermal, physico-mechanical, barrier and optical properties of three different packaging materials viz., PP/N6/PP, PET/N6/cPP and SiOx-PET/N6/cPP were studied. These packaging materials were packed with distilled water, which acted as a food simulant. Subsequently, these pouches were subjected to different thermal processing conditions such as pasteurization and retort processing. Both the processing techniques found to have retained the mechanical properties of all packaging materials. Water vapour transmission rate (WVTR) and oxygen transmission rate (OTR) of nylon-based combinations were increased after processing. Gloss found to decrease invariably irrespective of the material and increases with the severity of the treatment. XRD diffractogram shows changes in crystal structure as a result of thermal processing, and SEM analysis shows the crystal fragmentation. Absorption of water by the amide group of nylon 6 was observed, which could be a reason for the increase in OTR and WVTR. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of thermal processing conditions on the structure and dielectric properties of PVDF films

The effect of annealing and quenching tempera- tures on the crystallinity, β phase fraction and dielectric be- havior of poly (vinylidene fluoride) (PVDF) have been stud- ied. The crystallinity and β phase fraction of these films were evaluated using X-ray diffraction and FTIR techniques for different annealing and quenching temperatures. It is seen that the thermal processing conditions play a crucial role in deter- mining the dominant phase in PVDF. The β phase PVDF is the most desired phase for device applications such as sensors and actuators. Hence, the thermal processing conditions are optimized for obtaining β rich PVDF films. The β rich phase ofPVDFisobtainedfor filmswhichareannealedat80°Cand quenchedat 20 °C. The as-synthesized films for the optimized processing conditions was studied for their dielectric behavior and was found to exhibit dielectric constant as high as ~60.

Effect of rapid thermal processing conditions on the properties of Cu2ZnSnS4 thin films and solar cell performance

In the present work, we have studied the effect of several sulphurization conditions on the properties of Cu2ZnSnS4 thin films obtained through rapid thermal processing (RTP) of multi-period precursors with 8 periods of Zn/SnS2/CuS. In this study we varied the heating rate, the maximum sulphurization temperature, the time at maximum temperature and the amount of evaporated sulphur. The samples were characterized through scanning electron microscopy, energy dispersive spectroscopy, Raman scattering spectroscopy, X-ray diffraction, photoluminescence and I–V measurements. We have observed that at heating rates above 0.5°C/s the samples delaminated severely. As a result further tests were carried out at 0.2°C/s heating rate. The morphological studies revealed that the samples sulphurized at higher temperatures, shorter times and higher amount of evaporated sulphur exhibited larger grain sizes. The structural analysis based on Raman scattering and XRD did not lead to a clear distinction between the samples. Photoluminescence spectroscopy studies showed an asymmetric broad band characteristic of CZTS, which occurs in the range of 1.0–1.4eV and a second band, on the high energy side of the previous one, peaking at around 1.41eV. The intensity of this latter band varies from sample to sample revealing substantial differences in their optical properties. This band appears to originate either from the surface of the absorber or from the CdS layer and has a clear correlation with cell efficiency. The higher the intensity of this band the lower the cell efficiency, presumably due to the increase in recombination resulting from CZTS surface decomposition and eventually from the CdS with modified optoelectronic properties. The cell results hint toward a detrimental effect of long sulphurization times and a positive effect of higher sulphur vapour pressure and higher sulphurization temperature. Solar cell efficiencies improved with increased grain size in the absorber layer. The highest cell efficiency obtained in this study was 3.1%.

Thermal stability and oxidation of layer-structured rhombohedral In3Se4 nanostructures

The thermal stability and oxidation of layer-structured rhombohedral In3Se4 nanostructures have been investigated. In-situ synchrotron X-ray diffraction in a sealed system reveals that In3Se4 has good thermal stability up to 900 °C. In contrast, In3Se4 has lower thermal stability up to 550 or 200 °C when heated in an atmosphere flushed with Ar or in air, respectively. The degradation mechanism was determined to be the oxidation of In3Se4 by O2 in the heating environment. This research demonstrates how thermal processing conditions can influence the thermal stability of In3Se4, suggesting that appropriate heating environment for preserving its structural integrity is required.

Polyacetylene levels in carrot juice, effect of pH and thermal processing

This research focuses on the study of polyacetylenes in carrot juice and their response to pH, storage and thermal processing conditions. Falcarindiol-3-acetate (FaDOAc) and falcarinol (FaOH) were in fresh carrot juice at concentrations of 73 and 233μg/L, respectively. Reducing the pH of the raw carrot juice from its natural pH 6.13 to pH 3.5 resulted in 2 and 5 fold better extraction of FaDOAc and FaOH respectively in comparison to a control sample (pH 6.13). Polyacetylenes were retained better in acidified juices and cold storage temperatures (4°C) for first week of storage with respect to untreated juices. An increase in FaDOAc and FaOH of 10- and 16-fold, respectively, as compared to raw unprocessed samples was observed when processing samples at 90°C for 1min. This was assumed to be due to cell wall polysaccharides dissolution. However, negative correlation between total polyacetylenes and hexoses was confirmed by 1H NMR spectroscopy, indicating some biological links between polyacetylenes and soluble sugars.

Influence of Annealing Conditions on the Luminescence and Photoelectric Properties of Pure and Mn2+-Activated ZnGa2O4 Thin Films

The cathodoluminescence and photoelectric properties of thin films of ZnGa2O4 and ZnGa2O4:Mn produced by rf magnetron sputtering are studied as a function of thermal processing conditions and atmosphere. It is found that, after annealing in a hydrogen reducing atmosphere at temperatures up to 750°C, the luminescence intensity and electrical conductivity of the films increase. After annealing in a reducing atmosphere, a photoconductivity effect appears in ZnGa2O4:Mn thin films with a maximum near 400 nm that is related to electronic transitions from deep Mn2+ levels into the conduction band. The increased conductivity of ZnGa2O4:Mn thin films after annealing in a reducing atmosphere arises from a high concentration of donor centers in the form of oxygen vacancies and interstitial cation defects, which leads to the development of n-type conductivity.

The effect of thermal processing condition on the physicochemical and sensory characteristics of fermented sausages dried by Quick-Dry-Slice process®

The effect of different thermal processing conditions just after fermentation on physicochemical parameters and sensory attributes of salami and chorizo slices dried by Quick-Dry-Slice process®, was evaluated. Meat and common additives were mixed, stuffed and fermented. Previous to drying the sausages were subjected to thermal treatment at 53°C at different exposure times (0, 50, 65, 80, 95 and 110min). Finally, the sausages were sliced and dried using QDS process®. Color, instrumental texture and sensory analysis were performed. Lightness (L*) after fermentation increased with thermal processing in both products while redness (a*) and yellowness (b*) decreased only in salami. Thermal treatment after fermentation increased the initial force (F0). Cooked appearance, cooked fat odor, cooked flavor and stringiness increased when the thermal processing time was increased. Thermal processing of salami and chorizo at 53°C for 50min and drying up to 30% of weight loss resulted in a similar product to that obtained without thermal processing.

Canine-Specific PCR Assay Targeting Cytochrome b Gene for the Detection of Dog Meat Adulteration in Commercial Frankfurters

This report described a cytochrome b (cytb)-based polymerase chain reaction (PCR) assay for the detection of canine tissues in commercial frankfurters. Discriminating detection of canine derivatives in processed food products has important application in halal authentication as well as in health, religions, and fare trades. The assay based on a pair of canine-specific primers that targeted a 100 bp region of canine mithochondrial-cytb gene which is present in multiple copies and highly conserved within the same species. The specificity of the assay was tested against dog and eight most common animal meat species as well as five plant species commonly found in frankfurter formulation. The stability and specificity of the assay were verified under different thermal processing conditions under pure and complex matrices. Three commercial brands of chicken and beef frankfurters were tested in triplicate, and specific PCR products were obtained only from deliberately contaminated formulations. The detection limit of the assay was 0.1 % (0.02 ng DNA) of canine meat spiked with other meats in a typical frankfurter formulation. Shorter amplicon length, superior stability, and higher sensitivity of the assay suggested its potential application in the screening of canine-origin biomaterials in processed food products.

Thermal stability and phase transformations of martensitic Ti–Nb alloys

Aiming at understanding the governing microstructural phenomena during heat treatments of Ni-free Ti-based shape memory materials for biomedical applications, a series of Ti–Nb alloys with Nb concentrations up to 29 wt% was produced by cold-crucible casting, followed by homogenization treatment and water quenching. Despite the large amount of literature available concerning the thermal stability and ageing behavior of Ti–Nb alloys, only few studies were performed dealing with the isochronal transformation behavior of initially martensitic Ti–Nb alloys. In this work, the formation of martensites (α′ and α″) and their stability under different thermal processing conditions were investigated by a combination of x-ray diffraction, differential scanning calorimetry, dilatometry and electron microscopy. The effect of Nb additions on the structural competition in correlation with stable and metastable phase diagrams was also studied. Alloys with 24 wt% Nb or less undergo a transformation sequence on heating from room temperature to 1155 K. In alloys containing >24 wt% Nb α″ martensitically reverts back to β0, which is highly unstable against chemical demixing by formation of isothermal ωiso. During slow cooling from the single phase β domain α precipitates and only very limited amounts of α″ martensite form.

Microwave and mechanical properties of quartz/graphene-based polymer nanocomposites

We report microwave spectroscopy studies of graphene-based polymer-matrix composite materials subject to uniaxial elongation. The samples were prepared via shear mixing under the same thermal processing conditions of amorphous styrene butadiene rubber (SBR) with quartz grains on the order of micrometers in size and/or graphene sheets with thickness 10–20 nm and average lateral size 200 μm. An important result is the observation of a significant increase (up to 25%) in the effective microwave permittivity of hybridized nanocomposites comprising both quartz and graphene compared to the nanocomposites with quartz only. We suggest that the coating of quartz grains by graphene sheets is the most likely origin of this synergetic effect. In all cases, we also observe that the permittivity spectrum is unaffected by strain up to 8%. By examining the mechanical response, it is shown that the elasticity network of SBR polymer chains is significantly affected in the rubbery state by filling SBR with graphene and quartz particles.

Feasibility of Fish and Shellfish Curries Stored in Indigenous Polymer Coated Tin Free Steel Cans

The study indicated that the suitability of indigenous polymer coated TFS cans for processing at high temperature and pressure. The cook value was found to exhibit an inverse relationship with processing temperature (p<0.05) and was maximum at 115°C and minimum at 130°C. The fish products were acceptable even after 24 months of storage at ambient temperature. The initial overall acceptability score of about 8.75 and it was gradually reduced to around 6.78. It can be seen that the initial pH of fish, shrimp, crab and mussel curries are 5.9, 5.7, 5.6 and 6.0 respectively indicating that it is towards the acidic side. The acidic nature of the product can be attributed to the acidity contributed by the curry ingredients like tomato. During storage, the pH of the products was found to exhibit a decreasing trend. On the 6th, month of storage, the pH of fish, shrimp, crab and mussel curries are 5.7,5.6, 5.6 and 5.8 respectively which are significantly lower as compared to initial values. On the 12th month of storage, the pH of fish, shrimp, crab and mussel curries are 5.6, 5.6, 5.5 and 5.7 respectively. The results of the present experiments showed that the polymer coated TFS cans are suitable for processing fish products. Polymer coated TFS cans was found to withstand all the conditions of thermal processing. The TFS cans which are now available in India can be used for thermal processing of various fish products as a substitute to other packs.

Effect of particle size and heat treatment of soybean meal on standardized ileal digestibility of amino acids in growing pigs1

A study with growing barrows was conducted to evaluate of variations in particle size and degree of heat treatment during processing on standardized ileal digestibility (SID) of AA in soybean (Glycine max) meal (SBM). A commercial SBM batch was visually identified as being overtoasted due to its brownish color and was separated into small and large particles using a 1-mm sieve. In addition, 3 SBM were produced from 1 batch of soybean and exposed to different processing conditions (temperature and direct steam contact) referred to as mild (105°C; 34 min), medium (115°C; 45 min), and strong (139°C; 7 min). In total, 5 SBM-corn (Zea mays) starch-based diets were formulated to contain SBM as the sole protein source. This experiment was conducted according to a 6 × 6 Latin square design using 6 barrows (23 kg initial BW) fitted with a T-cannula at the distal ileum. With increasing particle size, SID of His and some dispensable AA increased (P < 0.05). Lower SID values in small compared to large SBM particles indicate more pronounced heat damage possibly due to increased surface area. The SID of CP and AA was lowest in the mild, intermediate in the strong, and highest in the medium toasted SBM (P < 0.001). These differences in SID are reflected in varying contents of trypsin inhibitors, Lys, reactive Lys, and NDF. In conclusion, both differences in particles size and variations in thermal processing conditions of SBM may affect SID of CP and AA.

Structure and Immuno-Stimulating Activities of a New Heteropolysaccharide from Lentinula edodes

In this study, a new heteropolysaccharide, here called L2, was separated from the fruit body of Lentinula edodes. Chemical and physical analyses indicated that L2 has a molecular weight of 26 KDa and consists of glucose (87.5%), galactose (9.6%), and arabinose (2.8%), but it does not possess a triple-helical conformation. Stimulation of the production of nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) in RAW 264.7 cells showed that L2 has significant immune activities involving toll-like receptor 2 (TLR2). Further studies demonstrated that the activities of L2 exhibited high stability in wide range of pH from 4.0 to 10.0, when the thermal processing temperature was below 121 °C. Our findings revealed that a new heteropolysaccharide without triple-helical conformation from Lentinula edodes shows immuno-stimulating activities involving TLR2 at modest pH and thermal processing conditions, which enable it to act as an active component in foods.

Influence of Heat Penetration on the Quality of Canned Ribbon Fish (Trichiurus lepturus )

Influence of heat penetration on the quality changes of ribbon fish canned in different media, oil and curry using tin-free steel cans, was assessed. The total process time for ribbon fish in oil pack was 47 min, and curry pack was 68 min, with a lethality value of 12.84 and 10.8 min for oil and curry pack, respectively. The biochemical and sensory analysis of the products was done during a storage period of 5 months. Total volatile base nitrogen and tri-methylamine nitrogen contents were found to be slightly higher but within the acceptable limit at the end of 5-month storage, while thiobarbituric acid and free fatty acid content increased slightly in curry and oil pack at the end of the storage period. The sensory quality of the processed products was rated as good by the taste panel, and the products were in acceptable condition even after storage of 5 months at room temperature (28 ± 2C). Practical Applications The present work on the development of ready-to-serve ribbon fish canned products will help in meeting the present demand in the market; if commercialized, it may be a better method of utilization of this presently underutilized fish to fetch higher value to both fishermen and processor besides providing a new and low cost raw material base to canning industry as well as it forms a means of diversification. It was found that tin-free steel cans are suitable for processing fish products, so they can be used as an alternative to tin and aluminum cans because of their capacity to withstand all the conditions of thermal processing.

Application of regularized Alternating Least Squares to an astrophysical problem

Determination of the compounds that are present in molecular clouds is carried out from the study of the infrared spectrum of astrophysical ices. This analysis plays a fundamental role in the prediction of the future evolution of the cloud under study. The process is simulated in the laboratory under similar conditions of thermal and energetic processing, recording the infrared absorption spectrum of the resultant ice. The spectrum of each ice can be modeled as the linear instantaneous superposition of the spectrum of the different compounds, so a Source Separation approach is appropriate. We propose the use of Alternating Least Squares and a Regularized version to identify the molecules that are present in the ice mixtures. Since the spectra and abundances are non-negative, a non-negativity constraint can be applied to obtain solutions with physical meaning. We perform several simulations of synthetic and real mixtures of ices in order to compare both solutions and to show how the proposed approach provides an efficient way to recover underlying spectral patterns that are physically meaningful.

Effects of rapid thermal process on the junction properties of aluminum rear emitter solar cells

N-type silicon with aluminum emitters for rear junctions was studied; aluminum back surface fields were replaced with n-type silicon wafers. Aluminum rear emitters for n-type silicon solar cells were studied with various rapid thermal processing conditions. With fast ramping-up and fast cooling, an aluminum rear junction was formed uniformly with low emitter recombination current. The effects of junction quality on solar cell efficiency were investigated.

Behavior of dairy protein in different simulated thermal processing conditions

Milk protein products (MPP) are routinely used by the industry, with the aim to provide improved texture, yield and palatability for processed food products. Understanding the behavior of the thermal protein denaturation for ingredients in the food matrix and its fundamental importance to the industry, this property may influence the attributes of the processed products. The objective of this study was evaluate the kinetics of the viscosity´s development from the rehydrated MPP in different concentrations, when used in different conditions of thermal processing using the Rapid Visco Analyzer (RVA) as a process simulator. Commercial samples of skimmed milk powder (SMP), whey protein concentrate (WPC), milk protein concentrate (MPC), whey powder (WP) and demineralized whey powder (DWP) were analyzed. The solid-liquid ratio evaluated were 0.1 g.g-1 a 0.4 g.g-1 for the WPC/MPC and 0.4 g.g-1 a 0.8 g.g-1 of dry solids per 1 g of water for SMP, WP and DWP because of the sensibility of the system to the concentration of solids. The Brazilian setup of industrial heat treatment used were 65oC/30min, 85o/15min and 95oC/5 min. Thus, the results could be interpreted as a function of the thickening rate during the heating and cooling. It was possible to optimize the different conditions of parameters of the MPP with the interpretations of the viscographic profiles obtained, with reference to the thermal behavior of proteins, especially for the WPC and MPC. Indeed, the RVA can be considered an emerging analytical tool for the study and knowledge of PDI, aiding to optimize the choice for the technological application in the food industry, through ongoing analysis of viscosity to estimate the rate of the protein denaturation.