Ultra-high Temperature Heating Research Articles

Ultra-High Temperature Treatment and Storage of Infant Formula Induces Dietary Protein Modifications, Gut Dysfunction, and Inflammation in Preterm Pigs.

Ready-to-feed liquid infant formula is increasingly used for preterm infants when human milk is unavailable. These formulas are sterilized by ultra-high temperature treatment, but heating and storage may reduce bioactivity and increase formation of Maillard reaction products with potential negative consequences for immature newborns. Using preterm pigs as a model for sensitive newborn infants, the study tests the intestinal responses of feeding experimental liquid formula within 5 days. A pasteurized formula (PAST) with the same nutrient composition but less protein modifications serves as control to ultra-high temperature-treated formula without (UHT) and with prolonged storage (SUHT). Relative to PAST, UHT contains lower levels of lactoferrin and IgG. Additional storage (40°C, 60 days, SUHT) reduces antimicrobial capacity and increases non-reducible protein aggregates and Maillard reaction products (up to 13-fold). Pigs fed SUHT have more diarrhea and show signs of intestinal inflammation (necrotizing enterocolitis) compared with pigs fed PAST and UHT. These clinical effects are accompanied by accumulation of Maillard reaction products, protein cross-links, and inflammatory responses in the gut. The results demonstrate that feeding UHT infant formulas, particularly after prolonged storage, adversely affects gut maturation and function in preterm pigs used as a model of preterm infants.

Impacts of guar and xanthan gums on pasting and gel properties of high-amylose corn starches

The effects of adding guar and xanthan gums on the pasting and gel properties of high-amylose corn starches, Hylon V (~50% amylose content) and NF-CG170 (~71% amylose content), were studied with waxy corn starch as a control, using an ultra-high temperature heating process (up to 130 °C) to gelatinize starches. Interaction between dispersed amylose and hydrocolloids contributed to the earlier onset of viscosity increase during pasting process (lower pasting temperatures) and strong synergistic effects in the peak, setback, and final viscosities with high-amylose starches, phenomena that were more pronounced when amylose content was higher. Conversely, addition of guar and xanthan gums to waxy corn starch resulted in higher pasting temperatures. After held at 5 °C for 2 h, the gelatinized high-amylose starch/hydrocolloid formed stronger and more elastic gels (higher G′ and tanδ) with denser microstructure and thicker gel skeleton, compared to starch alone. Compared to xanthan gum, guar gum displayed a much stronger synergistic effect with Hylon V in gel strength, while their difference in synergistic effect was less pronounced with NF-CG170, indicating that amylose dominated gel properties when at a high content (i.e., ~ 71% in starch).

Key issues of MoSi2-UHTC ceramics for ultra high temperature heating element applications: Mechanical, electrical, oxidation and thermal shock behaviors

MoSi2 based ceramics have great potential for high temperature heating element applications. In this paper, MoSi2-UHTC ceramics were produced by pressureless sintering by introducing ZrB2-20 vol% SiC ultra high temperature ceramic as additives. The key issues of the MoSi2-UHTC ceramics for ultra high temperature heating element applications, including mechanical, electrical, oxidation and thermal shock behaviors, were investigated. The aim of the study was to evaluate the possibility and ability of MoSi2-UHTC ceramics for high temperature heating element applications.

Mechanical and electrical properties of MoSi2-based ceramics with various ZrB2-20 vol% SiC as additives for ultra high temperature heating element

MoSi2-(ZrB2-20vol% SiC) ceramics were produced by pressureless sintering at 1700–1900°C for 1h. The amounts of ZrB2-20vol% SiC were in the range of 0–80vol%. Synergetic effects of ZrB2 and SiC additives on flexure strength of MoSi2 based ceramics were investigated in detail. A maximum strength of 279 ± 20MPa was examined for the ceramic with 20vol% (ZrB2-20vol% SiC). The electrical resistivity of the ceramics decreased with the volume fraction of (ZrB2-20vol% SiC) increasing. Microstructure analysis and topological transformation calculations were carried out, which further proved the flexure strength and electrical resistivity measurement results.

Storage stability and age gelation of reconstituted ultra-high temperature skim milk

Reconstituted skim milk (12–15% total solids) was processed under different preheat and direct ultra-high temperature (UHT) heating conditions. Samples heated at 75 °C/3 s + 143 °C/3 s showed proteolysis from plasmin and gelled rapidly on storage. Increased preheating (90 °C for 60 or 120 s), UHT holding (143 °C for 15 or 30 s), or combinations of these prevented proteolysis and slowed gelation; however some samples still gelled on storage. None of the properties followed (size, zeta potential, pH, serum mineral levels, colour or serum protein levels) gave any indication whether a sample would gel or not. High levels of κ-casein dissociated from the casein micelles on UHT processing and this did not change further on storage. The gelled material was composed of κ-casein-depleted casein micelles, which is not consistent with the current hypothesis for age gelation. A modified hypothesis for non-enzymatic age gelation is proposed where κ-casein-depleted casein micelles, formed during UHT treatment, slowly sediment due to gravity and cross-link to form a gel once a critical concentration is attained.

Effects of strength-weakening oriented heat treatment on structural steel and its application on steel plate shear walls

Low-yield point steels began to be widely used for energy dissipation in seismic design. Traditional aseismic designs often utilize section-cutting measurements to induce plasticity to be happened at designed location. But this paper investigated local steel strength-reduction measurement through controlled heat treatment that features high temperature heating and slow cooling process. A series of parametric heat treating process were applied and corresponding material tests were performed on Q235B carbon steel, low-alloy Q345B and Q390B steel, and Q235-grade angle steel. Results showed that the ultra-high peak temperature heating method (above 800°C) and slow cooling treatment method can effectively reduce the yield and ultimate strength of all those tested steel types. No obvious reductions were presented on the elastic modulus, and the steel ductility even presented slight increase after heat treatment. The peak temperature served as the primary influencing factor; meanwhile, the cooling rate and holding time also influenced the strength reduction, which influencing extents were related to the steel type. The locally strength-weakening concept and heat treatment were then applied on the steel plate shear wall. Results showed that an appropriate local strength-weakening design can produce better lateral strength and ductility than traditional designs and all section low-yield point steel plate designs.

Thermal treatment of lupin-based milk alternatives – Impact on lupin proteins and the network of respective lupin-based yogurt alternatives

In this study lupin-based milk alternative (LBMA), obtained from protein isolate of Lupinus angustifolius cv. Boregine, was homogenized and was subjected to different heat treatments (unheated; pasteurized: 80°C, 60s; ultra-high temperature heating (UHT): 140°C, 10s). Upon thermal treatment, lupin proteins, namely β-conglutin and α-conglutin, were stepwise denatured, which was accompanied by the exposure of masked sulfhydryl groups, the decrease of free sulfhydryl groups and reoxidation to disulfide bridges. Moreover, quaternary structure of lupin proteins was influenced upon heat treatment displayed with molecular weight distribution (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Further, particle size distribution showed that heat treatment promoted the formation of smaller particles. Differently heated LBMA were additionally fermented to lupin-based yogurt alternatives (LBYA) with different lactic acid bacteria (Lactobacillus plantarum TMW 1.460 and 1.1468, Pediococcus pentosaceus BGT B34 and Lactobacillus brevis BGT L150) and microstructural observations (Confocal Laser Scanning Microscopy, cryo-Scanning Electron Microscopy) were performed. Micrographs showed that harsher thermal treatments of LBMA (UHT heating) led to more close-meshed microstructures of respective LBYA. Further, the choice of microorganisms seemed to play a decisive role in microstructural appearance of respective LBYA as the composition of the networks were fundamental different.

Investigation and evaluation of a novel technique on CFRT column connection

This study investigated the effect of an innovative technique, heat treatment, on Q345B steel, which is generally used in China, and the application potential of this technique for H-beam moment connections to concrete filled rectangular steel tube (CFRT) column. A heat-treating process with ultra-high temperature heating and subsequent controlled slow cooling could have a weakening effect on steel strength. The effect of this heat-treating process on steel was investigated through a series of material tests on Q345B steel (Chinese standard). The Chaboche hysteresis material model was selected and calibrated to better describe the strength behavior under cyclic loading, and was then used for subsequent seismic simulations. This technique can be utilized to improve the seismic performance of connections by locally heat-treating the beam section (HBS), and then inducing the plastic hinge away from the critical region. The effect of HBS was investigated on two common CFRT column connections in China, namely, through-diaphragm and internal-diaphragm CFRT column connections. Results showed that the novel heat-treating process also had a significant weakening effect on Chinese Q345B steel. The hysteresis behavior of steel was different from the monotonic performance. The Chaboche model can effectively describe the hysteresis properties. The application of HBS succeeded in inducing plastic strain developed in the heat-treated region, and can reduce strain concentrations without significant connection moment strength loss.

Challenges Experienced in Scaling-Up the CSIR-Ti Process

The CSIR-Ti process produces titanium metal powder through continuous stepwise metallothermic reduction of titanium tetrachloride (TiCl4) in molten salt medium, and represents a cost-effective alternative to the standard Kroll process to produce titanium metal. Subsequent to proving the CSIR-Ti process at bench scale producing batches of ±2 kg titanium powder, the design, build and test of a continuous 2 kg/h Ti pilot plant was authorised. The scale-up process highlighted limited expertise in South Africa with regards to handling molten salt and molten reducing metals. Such gaps in knowledge are addressed in this study, which discusses a number of the engineering challenges faced and solutions developed around agitation of molten salt reactors, process pipe heating and insulation, molten salt flow measurement and also feeding of a highly reactive molten reducing metal. Scaling up the CSIR-Ti process, with requirements of continuous operation, compact size, effective agitation, pumping and maintaining salt in the molten state brought an unusual set of challenges requiring development of unique and prototype equipment. Further challenges were encountered in the handling and continuous feeding of molten reducing metal at the relatively small scale of the pilot plant. Solutions developed and discussed in this study include custom-modified agitators, custom-developed flow meters for measuring molten salt and molten metal flows, and a custom-designed molten metal feed system. Specialised materials such as, ultra-high temperature heating tape and ultra-low thermal conductivity insulation had to be imported as well as a special high-temperature pump that can pump a slurry consisting of molten salt containing a high weight percentage of suspended metal powder. The experience illustrates the technological difficulty of bridging the chasm between science and technology in that many unforeseen problems are encountered when developing and scaling up a new technology.

Elimination of Trypsin Inhibitor Activity and Beany Flavor in Soy Milk by Consecutive Blanching and Ultrahigh-Temperature (UHT) Processing

Soy foods contain significant health-promoting components but also may contain beany flavor and trypsin inhibitor activity (TIA), which can cause pancreatic disease if present at a high level. Thermal processing can inactivate TIA and lipoxygenase. Ultrahigh-temperature (UHT) processing is relatively new for manufacturing soy milk. Simultaneous elimination of TIA and soy odor by UHT processing for enhancing soy milk quality has not been reported. The objective was to determine TIA in soy milk processed by traditional, steam injection, blanching, and UHT methods and to compare the products with commercial soy milk products. Soybean was soaked and blanched at 70-85 degrees C for 30 s-7.5 min. The blanched beans were made into base soy milk. The hexanal content of the base soy milk was determined by gas chromatography to determine the best conditions for further thermal processing by indirect and direct UHT methods at 135-150 degrees C for 10-50 s using the Microthermics processor. Soy milk was also made from soaked soybeans by traditional batch cooking and steaming methods. Eighteen commercial products were selected from the supermarket. Residual TIA in soy milk processed by the traditional and steam injection to 100 degrees C for 20 min was approximately 13%. Blanching could inactivate 25-50% of TIAs of the raw soy milk. The blanch conditions of 80 degrees C and 2 min were selected for UHT processing because these conditions produced blanched soy milk without hexanal, indicating a complete heat inactivation of lipoxygenases. The TIA decreased with increased temperature and time of UHT heating. The maximal trypsin inhibitor inactivation was achieved by UHT direct and indirect methods with residual activities of approximately 10%. Some commercial soy milk products contained high TIAs. The results are important to the food industry and consumers. Kinetic analysis showed that heat inactivation (denaturation) of TIA, under the continuous processing conditions of the Microthermics processor, followed first-order reaction kinetics, and the activation energy of the inactivation was 34 kJ/mol.

Instrumental and Sensory Characterization of Heat-Induced Odorants in Aseptically Packaged Soy Milk

Predominant heat-induced odorants generated in soy milk by ultrahigh-temperature (UHT) processing were evaluated by sensory and instrumental techniques. Soy milks processed by UHT (143 degrees C/14 s, 143 degrees C/59 s, 154 degrees C/29 s) were compared to a control soy milk (90 degrees C/10 min) after 0, 1, and 7 days of storage (4.4 +/- 1 degrees C). Dynamic headspace dilution analysis (DHDA) and solvent-assisted flavor evaporation (SAFE) in conjunction with GC-olfactometry (GCO)/aroma extract dilution techniques and GC-MS were used to identify and quantify major aroma-active compounds. Sensory results revealed that intensities of overall aroma and sulfur and sweet aromatic flavors were affected by the processing conditions. Odorants mainly responsible for the changes in sulfur perception were methional, methanethiol, and dimethyl sulfide. Increases in 2-acetyl-1-pyrroline, 2-acetyl-thiazole, and 2-acetyl-2-thiazoline intensities were associated with roasted aromas. A marginal increase in intensity of sweet aromatic flavor could be explained by increases in 2,3-butanedione, 3-hydroxy-2-butanone, beta-damascenone, and 2- and 3-methylbutanal. Predominant lipid-derived odorants, including (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, (E,Z)-2,4-decadienal, (E)-2-nonenal, (E)-2-octenal, 1-octen-3-one, 1-octen-3-ol, and (E,Z)-2,6-nonadienal, were affected by processing conditions. Intensities of overall aroma and sulfur notes in soy milk decreased during storage, whereas other sensory attributes did not change. Color changes, evaluated by using a Chroma-meter, indicated all UHT heating conditions used in this study generated a more yellow and saturated color in soy milk in comparison to the control soy milk.

Process Design for Improved Fouling Behaviour in Dairy Heat Exchangers Using a Hybrid Modelling Approach

The main purpose of this study is the optimization of the heat exchange process in the dairy industry. A tool for simulating heat exchanger performance was fed with technical data of various heat exchanger confi gurations and process variables. Individual plant sections, like the preheater or ultra-high-temperature (UHT) heater, were simulated with modified variables, e.g. water temperatures or heat transfer areas. One modification, developed by simulation, was successfully implemented in a dairy plant. This proved the potential of the simulation software as a tool for design of new plants or the modification of existing plants. Performance rating was done by comparing pressure differences and overall heat transfer coefficients of the original setup and the modification. Improvements of simulated model running times for individual sections of up to 50% were achieved. Advantageous modifications were embedded in a simulation of the complete plant, additionally testing its effects upon milk quality. The main parameters for evaluation of plant performance were the pressure loss over the complete plant as well as the inlet temperature of the UHT heating water while milk quality primarily was rated by inactivation of thermophilic spores and loss of thiamine.

Plasma spray fabrication of near-net-shape ceramic objects

Among near net shape approaches, plasma spray deposition has its own advantages. It can perform ultrahigh temperature heating, produce components with layered compositions and structures, and fabricate thin-wall and large diameter objects. In this paper, the microstructural characteristics and their influential factors were reviewed in the light of the plasma spray forming process.

UHT processed milk concentrates

Ultrafiltration and reverse osmosis concentrates made from milk with differing fat and protein contents were sheared in defined flow conditions to establish the critical concentration of the constituents beyond which flow properties and heat stability change. The viscosity of the concentrates at 20 °C was calculated for volume concentrations below 0.5. Non-Newtonian flow occurred above this concentration, and heat coagulation tests at 140 °C revealed a dramatic drop in heat stability. The dense packing of the constituents above a volume concentration of 0.5 led to altered flow properties and decreased heat stability. The heat stability at 140 °C and storage stability correlated with the ash content and these increase as the ash contents decrease. Milk may be treated by applying ultra- filtration and nanofiltration to reduce ash content and enable high quality milk concentrates with a long- life stability to be produced by means of ultra-high temperature heating. milk / ultrafiltration / nanofiltration / rheology / ultra-high temperature

Effect of whey protein denaturation on structure of casein micelles and their rennetability after ultra-high temperature processing of milk with or without ultrafiltration

Abstract Whole milk and skim milk were ultrafiltered to 3× concentration and heated to 72°C, 89°C, 106°C, 123°C, or 140°C in an ultra-high temperature (UHT) plate heat exchanger. Whey protein denaturation increased with heating temperature and was higher in concentrated milk than in the corresponding unconcentrated milk. There was no difference in the patterns of whey protein denaturation and rennet coagulation times between whole milk and skim milk. Rennet coagulation time increased and gel strength decreased with milk processing temperature. Concentrating milk by ultrafiltration shortened coagulation time and increased gel firmness. UHT processed milk did not coagulate when rennet was added. Its 3× concentrated counterpart did coagulate although only a weak gel was formed. UHT heating caused the casein micelles to increase in size with additional protein material adhering to their surface, especially in the 3× skim milk heated to 140°C. This diffuse layer of material around casein micelles was not observed in 3× whole milk. It is suggested that this denatured protein is adsorbed onto the fat-water interfaces during homogenization.

Physical Properties of Yogurt: A Comparison of Vat Versus Continuous Heating Systems of Milk

Milk was processed by vat (85°C for 10 to 40min), high temperature, short time (98°C for .5 to 1.87min), and ultra-high temperature (140°C for 2 to 8s) heating systems and made into yogurt. Yogurt firmness ranged from 90 to 104g force for vat treatments, 74 to 96g for high temperature, short time treatments, and 47 to 65g for ultra-high temperature treatments. Planned contrasts between heating systems indicated significantly higher yogurt firmness and viscosity for vat versus high temperature, short time and ultra-high temperature systems. Yogurt from high temperature, short time milk showed the highest water-holding capacity, followed by ultra-high temperature and vat treatments. Correlation coefficient between yogurt firmness and whey protein denaturation was .83 and between apparent viscosity and whey protein denaturation was .89. Sensory evaluation indicated an overall preference for yogurt made from high temperature, short time (1.87min) milk.

Thermal Stability of Enterotoxins in Food

Biological and serological properties of staphylococcal enterotoxins exhibit remarkable thermal stability. The slope of the thermal destruction curve (z value) for enterotoxin A or D is 27–28 C and it is 32 C for enterotoxin B regardless of the initial concentration of enterotoxin, the heating medium, or the assay system used to detect the enterotoxin. Thermal stability of enterotoxins is influenced by the nature of the food, pH, presence of NaCl, etc., and the type of enterotoxin; enterotoxin A is relatively more stable to heat at pH 6.0 (or higher) than at pH 4.5–5.5. Enterotoxin D is relatively more stable at pH 4.5–5.5 than at pH 6.0 or greater. Heat treatments commonly used in food processing, that is pasteurization (72 C for 15 sec) or ultrahigh temperature heating (290 F for 9 sec) in a “Spiratherm” Unit of Fluid whole milk, or smoking and heating of cured sausage to 70–100 C, or heating of Cheddar cheese to 70–90 C, are not effective for complete destruction (to levels below detection by the microslide serological assay) of enterotoxin A or D when present initially at levels normally expected to be found in foods (0.5–1.0 μg per 100 ml or g). Enterotoxin A or B (30 μg/ml) heated at 100 C for 25 min in saline, containing 2% gelatin and 0.3% proteose peptone and at pH 7.0, retained biological activity toward humans with a suggestion of increased biological activity after heat treatment, especially with enterotoxin A. The length of time required at a given temperature for complete destruction of enterotoxin in a given food system depends upon the sensitivity of the detection system used and the amount of food sample used for recovery of the enterotoxin. Treatment of heated enterotoxin A or D with urea and its removal by dialysis before serological assay, increased the recovery of enterotoxin by almost 4-fold as compared to controls which were simply heated and were not treated with urea. Enterotoxin A or D present initially at 1 μg/ml in whole milk (using 2 ml for recovery of enterotoxin with urea treatment following heating and assay by the micro slide method of Casman and Bennett) was found to withstand heating of milk at 121.1 C for 15 min. In the absence of urea treatment of heated toxins in milk, both toxins were found to be inactivated (to less than 0.02 μg/ml (within 15 min at 121.1 C; between 13.8–14.8 min for toxin A and 12.8–13.8 min for toxin D.