Ultra-high Temperature Treatment Research Articles

The evaluation of microstructure of carbon/carbon composites generated by ultra-high temperature treatment towards excellent electromagnetic interference shielding property

Due to the need of electromagnetic shielding materials for satellites, carbon/carbon (C/C) composites have become a research focus due to their excellent properties. In this study, the ultrahigh treatment temperature was raised from 2500 °C to 2700 °C and 3000 °C, and the influence of micromorphology on the mechanical and electromagnetic shielding properties of materials was explored with an innovative image recognition method. The porosity of the C/C composites increased with increasing heat treatment temperature, from 6.95% to 8.65% after 3000 °C. The density decreased, and the graphitization degree increased gradually, indicating an improvement in the texture order degree. For the compression properties of the material, the Z direction after treatment at 3000 °C maintained a high compressive strength of 171 MPa. The electromagnetic interference (EMI) shielding efficiency (SE) of the C/C composites, which is completely consistent with the trend of electrical conductivity, increased with increasing heat treatment temperature, and the EMI SE of the C/C composites reached ∼80 dB after 3000 °C. It was found that reflection was the dominant EMI shielding mechanism of C/C composite materials. By comparing the comprehensive data indexes of C/C composites with other materials, the composites are expected to be a new generation of satellites with electromagnetic shielding material.

Effect of Heat Treatment on Microstructural Evolution and Microhardness Change of Al-5Zn-0.03In-1Er Alloy

Adding an appropriate amount of Er element to Al-Zn-In alloys can improve the electrochemical performance of Al alloys; it is convenient to study the electrochemical behavior of the alloy in the rest of our work. However, Er segregation in solid solutions which reduced the comprehensive properties of alloys was difficult to reduce and there was no report on the homogenization of Al-Zn-In alloys. We found that the ultra-high temperature treatment (UHTT) can obviously reduce Er segregation. To explore the better homogenization treatment and the microstructure evolution of Al-5Zn-0.03In-1Er alloy after UHTT, we carried out a series of heat treatments on the alloy and characterized the microstructure of the alloy by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and transmission electron microscopy (TEM). The results showed that the main element Er of the Al-Zn-In-Er was largely enriched in grain boundaries after UHTT; the distribution Zn and In was almost unchanged. The as-cast Al-Zn-In-Er alloy consisted mainly of α(Al) solid solution and Al3Er phase. As the temperature of UHTT increased and the treatment time prolonged, the precipitated phase dissolved into the matrix, and there were dispersed Al3Er particles in the crystal. The proper UHTT for reducing the interdendritic segregation of the alloy was 615 °C × 32 h, which was properly consistent with the results of the evolution of the statistical amount of interdendritic phase, the line scanning analysis and the microhardness. Moreover, the microhardness of the alloy after treatment of 615 °C × 32 h was obviously higher than that of the as-cast alloy because of the anchoring effect of Al3Er nanoparticles on the movement of dislocations.

A Review on Consumption of Raw or Heated Cow Milk

- In the framework of the present inclination towards greater organic commodities, there would seem to be an growing desire for bare exploit feasting, since raw milk is linked with many claimed health advantages that are thought to be lost when heated. Many human infections, on the other hand, It's possible to separate it from fresh bovine dairy. Although the prevalence of gastrointestinal microorganisms in uncooked cow dairy varies, their existence has been demonstrated in several investigations, and gastrointestinal infections produced by Gastroenteritis, Salmonella., and highly virulent appropriate anti E. coli have been reported often. In affluent countries, milk-borne and dairy illnesses accounted for 2e6 % of microbial poisoning illnesses. This review's goal is to give methodically volume data on the risks and benefits of consuming raw and warmed cows dairy. Both physiological and microbial and nutritional aspects are taken into account. As a result, raw milk intake is shown to represent a genuine health risk owing to the possibility of contamination with human pathogens. As a result, it is highly advised that milk be heated before drinking. Heating (especially ultra-high temperature and comparable treatments) will not significantly affect the nutritional content of raw milk or other advantages associated with raw milk intake, with the exception of a changed organoleptic character.

Rheological properties of fermented milk from heated and high pressure-treated camel milk and bovine milk

Gelation of camel milk is a challenge to the industrial utilization. This study investigated the impact of low-temperature long-time (LTLT) and high-temperature short-time (HTST) pasteurization, ultra-high temperature (UHT) treatment, and high-pressure processing (HPP), at 300 and 600 MPa, on the rheological properties of the fermented milk. Both camel and bovine milk were fermented by Lactiplantibacillus plantarum and Ligilactobacillus salivarius. Both milk treated at 300 and 600 MPa showed the highest Lb. plantarum and Lb. salivarius numbers, with ∼9 log.HTST and UHT-treatment increased particle size in bovine milk but decreased it in camel milk. HPP-treatment decreased particle size in both camel and bovine milk. All fermented milk showed shear-thinning behavior, regardless of milk type, processing, culture type and storage time. For both camel and bovine milk, fermented UHT-treated milk had the highest viscosity followed by fermented HPP-treated milk. Lowest viscosities were observed for fermented LTLT-treated and HTST-treated milk. Small deformation rheology showed consistently lower tan δ values for fermented HPP-treated camel milk than for fermented heated camel milk, with the latter only giving tan δ < 1 at elevated frequencies. UHT- and HPP-treatment of milk can enhance the rheological properties of fermented camel milk compared with other heat treatments.

Loss of bioactive microRNAs in cow's milk by ultra-high-temperature treatment but not by pasteurization treatment.

Milk microRNA (miRNA) with bioactivity is beneficial for human health. However, the effect of heat treatment on miRNA in milk is still not clear. In this study, the miRNAs in raw (RM), pasteurized (PM) and ultra-high-temperature (UHT) milk (UM) from the same batch were extracted, sequenced and analyzed. The results showed that there was a significant difference in miRNAs between RM and UM, but not between RM and PM. The total read counts of milk miRNAs were significantly decreased by heat treatment, with the least counts in UM (P < 0.05). The average length and GC percentage of miRNAs were significantly reduced by heat treatment (P < 0.05), while there was no significant difference in these terms between RM and PM. The content of miRNAs was verified by qPCR, finding that miR-17-5p, miR-25, miR-27b and miR-9-5p were significantly reduced in UM (P < 0.05) but not significantly affected in PM (except miR-27b). In addition, the targeting gene ontology enrichment functions of the different presented miRNAs were mostly enriched in biological process, cellular component and molecular function. The top 20 enriched miRNAs with different levels in heat-treated milk were identified by the Kyoto Encyclopedia of Genes and Genomes enrichment analysis. Interestingly, most of the functions of these miRNA targeting genes are involved in cancer or inflammation activity. This study revealed that the bioactive miRNA in RM was lost after UHT treatment but not in pasteurized treatment. © 2021 Society of Chemical Industry.

Bulk-scale synthesis of randomly stacked graphene with high crystallinity

Since the strong interlayer interaction of AB-stacked graphene in bulk form degrades the superior property of single-layer graphene, formation of randomly stacked graphene is required to apply the high performances of graphene to macroscopic devices. However, conventional methods to obtain bulk-scale graphene suffer from a low crystallinity and/or the formation of a thermodynamically stable AB-stacked structure. This study develops a novel approach to produce bulk-scale graphene with a high crystallinity and high fractions of random stacking by utilizing the porous morphology of a graphene oxide sponge and an ultrahigh temperature treatment of 1500–1800 °C with ethanol vapor. Raman spectroscopy indicates that the obtained bulk-scale graphene sponge possesses a high crystallinity and a high fraction of random stacking of 80%. The large difference in the random-stacking ratio between the sponge and the aggregate samples confirms the importance of accessibility of ethanol-derived species into the internal area. By investigating the effect of treatment temperature, a higher random-stacking ratio is obtained at 1500 °C. Moreover, the AB-stacking fraction was reduced to less than 10% by introducing cellulose nanofiber as a spacer to prevent direct stacking of graphene. The proposed method is effective for large-scale production of high-performance bulk-scale graphene.

Trypsin inhibitor activity, phenolic content and antioxidant capacity of soymilk as affected by grinding temperatures, heating methods and soybean varieties

Two soybean varieties (yellow and black) were ground under three temperature regimes (cold, ambient and hot) and then the raw soymilk underwent three thermal treatments (traditional stove cooking, one-phase ultra-high temperature (UHT) processing, and two-phase UHT processing). Trypsin inhibitor activity (TIA), chymotrypsin inhibitor activity (CIA), total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC), DPPH free radical scavenging activity, and oxygen radical absorbing capacity (ORAC) were significantly affected by the above factors and their interactions. For raw yellow soymilk, hot grinding generated 64 and 69% lower TIA than cold and ambient grinding, respectively. For raw black soymilk, hot grinding generated 40 and 43% lower TIA than cold and ambient grinding, respectively. After heating process, the advantage of hot grinding was reduced. By suppression of the development of lipoxygenase-induced hydroperoxides, hot grinding preserved the most sulfhydryl and disulfide groups. Stove cooking following ambient grinding resulted in the lowest CIA. Except TFC, hot grinding recovered the highest phenolic content and antioxidant capacity. CTC from hot grinding was about twice that from ambient grinding. Black soymilk contained significantly higher antioxidant capacity than yellow soymilk and UHT treatments showed advantage over traditional stove cooking in the preservation of phenolics.

Sn-V centers in diamond activated by ultra high pressure and high temperature treatment

We investigate the activation of Sn-V centers in diamond through ions implantation and the subsequent high pressure and high temperature (HPHT) treatment at 15 GPa and 2300 °C. Sn ions is implanted at fluences greater than 2 × 1014 cm−2 by varying the acceleration voltage up to 180 kV, which results in a Sn distribution with a uniform concentration of 1 × 1020 cm−3 down to a depth of 50 nm from the surface. The subsequent HPHT treatment recovers the transparent appearance and preserves the introduced Sn ions. The sample shows emission peaks composed of four levels that originate from the Sn-V centers. The two distinct emission peaks from the lower excited states to the split ground states are stable up to 77 K. At 10 K, these peaks are clearly observable at excitation powers spanning two orders of magnitude, which suggests the preferential carrier capture at these centers.

Different processed milk with residual xanthine oxidase activity and risk of increasing serum uric acid level

Xanthine oxidase (XO), the main enzyme responsible for the formation of uric acid, is abundant on milk fat globule membrane (MFGM), which might be associated with the increasing risk of hyperuricemia from high-fat compared to the low-fat dairy product. In our study, we hypothesized that XO activity could be maintained after hydrolysis under conditions simulating digestion and produce uric acid either in blood or intestine. First, protein levels of XO in different types of processed milk (ultra-high temperature treatment (UHT), pasteurization and skim) were examined by Western Blot, and XO activity was measured by the level of uric acid production. In conclusion, residual XO activity in pasteurized whole milk could be retained after in vitro hydrolysis, and increased uric acid levels in vitro and in vivo. Although whole milk is highly nutritious, XO in milk can be a risk factor for acute increase of uric acid. This study elaborated the different digestive characteristics of milk after different processes, and provides a theoretical basis of milk selection in controlling gout.

The Evaluation of Microstructure of Carbon/Carbon Composites Generated by Ultra-High Temperature Treatment Towards Excellent Electromagnetic Interference Shielding Property

The Evaluation of Microstructure of Carbon/Carbon Composites Generated by Ultra-High Temperature Treatment Towards Excellent Electromagnetic Interference Shielding Property

High-temperature binding parameters and molecular dynamics of 4-hydroxybenzoic acid and β-casein complexes, determined via the method of continuous variation and fluorescence spectroscopy

Interactions between β-casein and 4-hydroxybenzoic acid (4HBA) were investigated following ultra-high temperature (UHT) treatment at 140 °C for 10 s. The aim of the work was to identify the binding strength, binding stoichiometry and type of molecular interactions between protein and bioactive compound. Molecular dynamics (MD) analysis shows that binding is stabilised by a wider variety of residues than is often indicated in simpler docking studies. Construction of Job plots via fluorescence quenching argues that β-casein can accommodate two 4HBA molecules. This is in agreement with MD analysis, which demonstrates the stability of ligand in two different binding sites of the receptor. FTIR results indicate a binding interaction between the two components and UV–vis measurements record an increase in the absorption of 4HBA following UHT treatment in the presence of β-casein. The latter observation argues that 4HBA may be bound covalently following heat treatment. This is further supported by MD simulations and quantum mechanics calculations that indicate one site has the potential for binding covalently to 4HBA via the lysine32 residue of the β-casein molecule. This work addresses often overlooked issues in the determination of binding parameters, through the use of the method of continuous variation for the accurate determination of binding stoichiometry, as well as making use of a nonlinear fluorescence binding equation to account for the residual fluorescence of formed complexes. The findings give a broader understanding of the fate of bioactive ingredients in UHT treated beverage systems, allowing industry to make informed decisions on the inclusion of insoluble fibres and the impact of heat treatment on their products.

Ultra-high Temperature (UHT) Processing: Technological Significance and Updates

Background: Background: Milk forms an integral part of the human diet from the nutritional point of view. Besides nutrition, it has also unique functional properties which are harnessed by the industry for numerous uses. Being highly perishable specific techniques are required to minimize the losses during processing and adequate preservation of this precious commodity. In the U.S. and many other parts of the world, the traditional pasteurization of milk requires a minimum heat treatment of 72ºC for 15 seconds with subsequent refrigeration. However, the advent of Ultra High Temperature (UHT) treatment of milk has added a new dimension to the marketing of liquid milk in urban as well as remote areas without the requirement of cold chain management. The distinctive feature of UHT processed milk is that it is commercially-sterile-not pasteurized and so has long shelf life at room temperature. UHT milk, also known as long-life milk, is emerging as an attractive commercial alternative offering a hygienic product of unmatched quality, which can be bought anywhere, at any time and in any quantity. The present review will discuss numerous aspects of UHT processing of milk with reference to historical significance, fundamental principle, various systems used and prerequisites, type of exchangers used, fouling and other defects in system, chemical and microbiological effect of the treatment, its effect on nutritional components, organoleptic quality of milk and the advantage and involved challenges of the process. Conclusion: Raw milk is easily contaminated with pathogens and microbes and hence its consumption of raw milk is associated with certain ill health effects. Therefore, heating milk before consumption is strongly suggested. Thus, UHT treatment of milk is done to ensure microbial safety and also to extend the shelf life of this highly perishable commodity. Heating milk at such a high temperature is often associated with the change of organoleptic properties like change in flavor or cooked flavor, rancidity due to microbes or acid flavor, etc. But UHT treatment does not substantially decrease the nutritional value or any other benefits of milk.

Comparative study on the microstructure and functional properties of casein in goat milk processed by different methods

SummaryThis work compared the thermal stability, microstructure and functional properties of casein (CN) in goat milk processed by different methods, including homogenisation, low‐temperature long‐time (LTLT), high‐temperature short‐time (HTST), ultrapasteurisation (UP) and ultrahigh temperature (UHT) treatment. The greatest development of CN‐whey protein complexes was observed in LTLT goat milk and the least in HTST goat milk. The CN micelles in LTLT, UP and UHT milk were more obviously changed than the CN micelles in HTST milk, and the random coil content increased significantly after the homogenisation, UP and UHT treatments. The homogenisation had a significant effect on the functional properties of CN. In addition, the most obvious changes in the properties of CN were observed in LTLT and UHT goat milk. The results suggested that homogenisation, pasteurisation and UHT can cause effective changes in the functional properties of CN in goat milk that facilitate its application in the milk industry.

Influence of seasonal variation and processing on protein glycation and oxidation in regular and hay milk

Climate and feeding influence the composition of bovine milk, which is further affected by thermal treatment inducing oxidation and Maillard reactions. This study aimed to evaluate season- and processing-related changes in the modified proteome of milk from two different feeding systems. Therefore, tryptic digests of regular and hay milk were analyzed by targeting 26 non-enzymatic modifications using LC-MS. Forty-five glycated, 48 advanced glycation endproduct (AGE-) modified, and 20 oxidized/carbonylated peptides representing 44 proteins were identified with lactosylation, formyllysine, and carboxymethyllysine being most common. The numbers and quantities of glycation- and oxidation-related modifications were similar between regular and hay milk and among seasons. The effects of pasteurization and ultra-high temperature (UHT) treatment were comparable for both milk types. In particular UHT treatment increased the numbers of identified modifications and the relative quantities of lactosylated peptides. The number of identified AGE-modified and oxidized residues increased slightly after UHT-treatment, but the contents were stable.

Effect of Ultra-high temperature processing on the physicochemical properties and antibacterial activity of d-limonene emulsions stabilized by β-lactoglobulin/Gum arabic bilayer membranes.

The objectives of the present work were to investigate the influence of Gum Arabic (GA) on the physicochemical properties and ultra-high temperature (UHT) processability of β-lactoglobulin(β-lg)-stabilized d-limonene emulsions. Moreover, we also wanted to evaluate the antimicrobial efficiency and mechanism of β-lg-GA bilayer d-limonene emulsions. Physicochemically stable bilayer emulsions could be formed with an optimal concentration of GA (1.00wt%), which showed a higher tolerance to both flocculation and coalescence, as well as better protective effects on d-limonene against UHT-treatment that up to 94.32% of d-limonene was retained in emulsions. Likewise, it is also noteworthy that no obvious difference in the minimal inhibitory concentration could be found between bilayer emulsions with or without UHT processing. Moreover, the antimicrobial effects of the bilayer emulsions with UHT treatment were shown to be dose-dependent, which was evidenced from the results of scanning electron microscopy and the determination of released cell constituents. Keywords: β-lactoglobulin; gum arabic; d-limonene emulsion; physicochemical stability; UHT processability, antimicrobial efficiency.

The role of key process steps on microstructural organisation of fat globules and lipid profiles in UHT milk processed in a pilot plant unit

Microscopy was applied to explore changes in fat globules and gas chromatography was used to determine the fatty acid distribution in different lipid classes in ultra-high temperature (UHT) milk processed in a pilot plant. Four milk samples were collected at key steps during UHT-milk production. Second-stage homogenisation significantly decreased fat globule size and disrupted the original milk fat globule membrane (MFGM) organisation. Pasteurisation applied before homogenisation increased the adsorption of casein micelles to the newly formed MFGM. The final UHT treatment for 4 s at 137 °C exacerbated the damage to MFGM causing disruption of fat globules. Damaged fat globules in UHT milk were more prone to aggregation and entrapment in the protein network compared with fat globules in commercial UHT milk. The significant modifications of milk microstructure and lipid composition suggested processes applied in commercial dairy plants might contribute to destabilisation of UHT milk during shelf life.

Identification of aroma compounds in pea protein UHT beverages

The objective of the study was to characterize changes in the aroma profile of pea protein beverage during Ultra High Temperature (UHT) processing and subsequent refrigerated storage. The aroma profiles were characterized using Gas Chromatography/Mass Spectrometry/Olfactometry (GC/MS/O); twenty-one aroma compounds were identified and further quantified using dynamic headspace-GC/MS/MS analysis. Descriptive analysis indicated the UHT processing treatment significantly changed the sensory aroma profile of the pea protein beverage; however, no further changes were reported as a result of storage. Aroma recombination experiments in pea protein samples confirmed the sensory relevance of the identified compounds and indicated lipid oxidation and the Maillard were the reaction pathways responsible for the observed aroma changes during the UHT treatment.

The effect of heat treatment on the microstructure and functional properties of whey protein from goat milk

This work investigated the effects of thermal processing methods commonly used in the dairy industry and prolonged treatment at different temperatures on the denaturation, microstructure, and functional properties of whey proteins (WP) from goat milk. The complete denaturation of WP was observed in goat milk treated at 85°C for 30 min, and at a higher temperature (>85°C), a considerable amount of WP was easily denatured. The low temperature, long time treatment had the least effect on the secondary structure, whereas ultra-high temperature treatment had the greatest effect, and the amount of regular structures decreased gradually with prolonged time. The most serious morphological damage occurred after treatment at 85°C for 30 min, which was consistent with the denaturation results. This result indicated that the denaturation degree, particle size, surface hydrophobicity, and microstructure had a strong influence on the functional properties of WP from goat milk after heat treatment. The heat treatment of goat milk at 65°C for 30 min and 85°C for 15 s increased the particle size, turbidity, zeta potential, and surface hydrophobicity of WP, and these increases ensured that the WP had a good emulsifying activity index, water-holding capacity, oil-holding capacity, foaming capacity, and foam stability. This study simulated the heat treatment conditions used in actual production, aiming to provide a theoretical basis for industry.

Structural and compositional changes during UHT fouling removal—Possible mechanisms of the cleaning process

Ultra-high temperature (UHT) treatment of milk forms a deposit or fouling in the processing equipment that is mineral-based with an enclosed protein network. This study addresses the fundamental mechanisms that control the removal of this deposit. For this purpose, the structural and compositional changes during the cleaning process have been studied. The structure analysis was performed with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) on samples that were quenched at different stages of the cleaning process. It was found for acid cleaning that the mineral content is rapidly decreasing in the fouling layer as the cleaning continues, but there is still an intact protein structure with the similar thickness as the original fouling. For alkali cleaning, part of the protein structure was subsequently removed from the outside towards the stain-less steel as a function of time, while the mineral structure was mostly remaining. The break-up of the organic network structure, which likely involves depolymerization of protein aggregates, were found to control the cleaning efficiency. The weakening of the protein network facilitates the removal of the UHT fouling layer during the acid cleaning step and allow for an efficient cleaning cycle. The chemical reactions that occur within the fouling layer between the hydroxyl ions and the protein network was modeled according to a depolymerization reaction and a mechanistic model of the cleaning process is presented.

Change in interfacial properties of milk fat globules by homogenization and thermal processing plays a key role in their in vitro gastrointestinal digestion

The effects of homogenization, homogenization plus thermal processing including high temperature short time (HHTST) or ultra-high temperature (HUHT) treatment on digestion and interfacial properties of milk fat globules during simulated gastrointestinal digestion were investigated. Compared to raw milk fat globules, homogenization and thermal processing increased the initial digestion rate of milk fat globules. Homogenization increased the release of middle- and long-chain fatty acids, HHTST increased the release of unsaturated fatty acids, and HUHT increased the release of all types of fatty acids under gastrointestinal digestion. After homogenization, milk proteins (caseins and whey proteins) increased but glycosylated molecules decreased, both of which were at the surface of milk fat globules. The amount of glycosylated molecules at the surface of HHTST milk fat globules and the amount of denatured milk proteins at the surface of HUHT milk fat globules were higher than those of homogenized milk fat globules. During gastrointestinal digestion, fat globules in HHTST milk possessed higher amount of glycosylated molecules and more integrated phospholipid layers, and HUHT milk fat globules had more filamentous phospholipid layers, and less integrated phospholipid layers and glycosylated molecules than those of homogenized milk fat globules. Therefore, the changes in composition and microstructure of glycosylated molecules and phospholipid layers at the surface of milk fat globules induced by homogenization and thermal processing might contribute to the digestion difference of milk fat globules.