Increasing Heating Time Research Articles

Micro-fracture mechanism of microwave induced fracturing of basalt based on a novel Electromagnetic–Thermal–Mechanical coupling model

Microwave-assisted rock fracturing is recognized for its efficiency, energy savings, and environmental benefits. Investigating microscopic mechanisms of microwave-induced rock fracturing is essential for predicting the weakening effect on rock. A coupled Electromagnetic–Thermal–Mechanical model based on FEM–DEM was established to describe the response of rock under microwave irradiation. This model employs interpolation algorithms and mineral lattices randomization algorithms to establish a 2D cross-sectional representation of rock. A discrete element calculation method is proposed to synchronize computational time with the experimental time. The model can simulate the multi-physical field response of different rocks under various conditions, making it an effective tool for studying microwave-induced rock fracturing. The effectiveness of the numerical model was validated through open-end microwave-induced fracturing experiments on basalt. Additionally, the study elucidates the micro-fracture mechanism of basalt under microwave irradiation. The results indicate that the direction of crack propagation is influenced by microwave power and boundary effects. The patterns of fracture development between minerals are summarized as follows: Initial fractures primarily result from the rapid heating of microwave-absorbing minerals like enstatite,creating a significant temperature gradient. With increased heating time, heat transfers to highly expansive minerals such as olivine, causing fractures due to localized thermal expansion.

Formation of advanced glycation end products in glucose-amino acid models of Maillard reaction under dry- and wet-heating conditions.

Advanced glycation end products (AGEs) are compounds formed by non-enzymatic processes in the Maillard reaction and can cause various chronic diseases. This study explores the AGE formation process in a glucose-amino acid system under both wet- and dry-heating conditions, and analyzes the effect of cysteine in AGE formation. Under wet-heating conditions, Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL) concentrations rose for the initial 90 min and subsequently declined after 120 min; after 90 min of heating, the maximum yields in the absence of cysteine were 1151.04 ± 14.01 and 3386.90 ± 26.55 ng mL-1, respectively. The concentration of pyrraline (Pyr) increased after 30 min and then decreased after 60 min with a maximum yield of 777.68 ± 23.36 ng mL-1. However, in dry-heating models, the AGE concentrations consistently increased with increasing heating time; the maximum yields for CML, CEL and Pyr were 468.66 ± 10.96, 1993.57 ± 14.81 and 1085.74 ± 58.06 ng mL-1, respectively. The addition of cysteine showed an inhibitory effect on AGE formation, especially for Pyr in the dry-heating model, with inhibition rates ranging from 17.14% to 95.60%. Although wet-heating models produced more CML and CEL, they produced less Pyr than dry-heating models. The AGE formation in wet-heating models positively correlated with the reaction rate; however, the dry-heating reaction demonstrated a more complex relationship between reaction rate and reaction protocol. Moreover, cysteine exhibited a significant inhibitory effect on AGE production, and the degree of inhibition was proportional to the cysteine concentration. This study provides important insights into the mechanisms for AGE formation under various heating conditions, such as those representing baking (dry-heating) and steaming conditions (wet-heating). © 2024 Society of Chemical Industry.

Effect of microwave heating on rock damage and energy evolution

Rock fragmentation efficiency can be increased by microwave heating. The mechanical properties and energy evolution characteristics of coarse sandstone specimens under different microwave heating conditions are compared in this paper. The effects of microwave heating time and power on coarse sandstone specimens of peak stress, elastic modulus, brittleness index, damage variable, and impact energy index are analyzed. The results indicate that the microwave heating power and microwave heating time are inversely proportional to peak stress and elastic modulus and directly proportional to peak strain. With the increase of microwave heating power and microwave heating time, the brittleness index and damage variable of rock specimens increase, the impact energy index decreases. The microwave heating power and microwave heating time increase the rock brittleness index. The energy absorption rate of rock specimens decreases with the increase of microwave heating time. The impact energy index is inversely proportional to microwave heating power and microwave heating time. High-power and long-time microwave heating can reduce the possibility of rockbursts and the intensity of potential dynamic disasters. The research conclusion can provide the theoretical and technical basis for breaking rock by microwave heating.

Optimization of cold-induced aerated gels formed by Maillard-driven conjugates of SPI-gellan gum as an oil substitute in mayonnaise sauce

This research aimed at chracaterization of composite cold-set aerated gels composed of SPI-gellan gum Maillard conjugates. The optimized gel was eventually incorporated in mayonnaise sauce as an oil substitute. The optimum conditions were statistically determined as 1.5% SPI, 300 mM CaCl2, and 90 min heating time. All of which resulted 35% glycation degree and high molecular weight conjugates on top of SDS-PAGE injection wells. Increasing CaCl2 concentration enhanced the adsorption of conjugates at air-water interface, decreasing the density but increasing the WHC and hardness. Increasing heating time facilitated gelation which improved gel hardness. The optimized gel was microstructurally homogeneous with increased overrun (20.8%) and H-bonds. The rheological measurements showed viscoelastic gel network which was thermally stable up to 90°C, besides increasing G’, G” and η* at 85°C. Substitution of optimized gel in mayonnaise sauce improved the nutritional value and thermal stability (77.13%), but declined calorie. The substituted mayonnaise sauce was greatly accepted by panelists. Thus, the aerated gel formed at optimum conditions had great structural and mechanical characteristics and its usage as an oil analogue induced a low-calorie mayonnaise sauce with acceptable sensory properties.

Investigating the impact of manufacturing conditions on crack growth rate in nitrile butadiene rubber for enhanced service life – Part 02: Crosslink density via multi-stage swelling analysis

The importance of the state of cure of elastomer components with regard to fatigue behavior and thus also durability was already discussed in more detail in Part 01 of the paper. It was shown that crosslinking time and temperature have an enormous influence on the crack growth behavior in nitrile butadiene rubber (NBR). In the course of this, a fourfold deceleration in crack growth was observed with a 20 K increase in manufacturing temperature. To confirm this trend, test specimens were produced at 180 °C. Crack growth was found to be 40 times slower, especially in high tearing energy ranges, compared to 150 °C. To analyze the observed behavior in more detail, cylindrical samples were taken from the plain strain test specimens (used for the crack growth measurements), and multi-stage swelling was performed with them. This allowed a detailed analysis of the degree of cure and the sulfur chain composition. It was found that the crosslink density decreases with increasing manufacturing temperature due to decomposition and the proportion of polysulfidic crosslinks decreases with increasing heating time due to desulfurization. Furthermore, a correlation between the results found by means of the rubber process analyzer (RPA) and the swelling results could be established looking at the maximum transmitted torque during the isothermal crosslinking phase.

MICROWAVE HEATING EFFECT ON THE OXIDATION AND QUALITY OF COLD-PRESSED SUNFLOWER OIL

Sunflower oil is widely used in the human diet, primarily due to its constituent components and its applications in producing functional products. The use of microwave ovens in food preparation has become widespread in recent years due to certain advantages that include saving time, energy and convenience. As a result of heat treatment of oils, various chemical reactions can occur, leading to the formation of products that may indicate deterioration or a reduction in quality. For this purpose, untreated oil (not subjected to heating) and oil heated in a microwave oven for varying durations (ranging from 4 to 20 minutes) were analyzed in this study. The quality assessment of cold-pressed sunflower oil was conducted using standard official methods to measure peroxide, acid, and iodine values. The progression of oil oxidation was tracked by analyzing conjugated dienes and conjugated trienes through UV-spectroscopy (method AOCS Ch 5-91). Additionally, considering the theoretical link between microwave heating and changes in fatty acid composition, the fatty acid profile of the oil was determined according to MKC EN ISO 12966-4:2015. The results indicate a notable shift in the peroxide value (PV). Specifically, after heating the oil for 4 minutes, the PV exceeds the permitted limits. Furthermore, a decrease in the iodine value is observed with increasing heating time, while no significant changes are noted in the acid value. Additionally, changes in the content of fatty acids are observed in cold-pressed sunflower oil. At specific wavelengths (232 and 268 nm), conjugated dienes and trienes were detected as oxidation products, i.e. the extinction coefficients (K232) and (K268) fell within the ranges of 3,72-4,16 and 1,25-2,56, respectively. These findings lead to the conclusion that microwave heating induces changes in the quality of cold-pressed sunflower oil. To maintain its quality, an appropriate choice of heat treatment is required.

Exploration of the prediction and generation patterns of heterocyclic aromatic amines in roast beef based on Genetic Algorithm combined with Support Vector Regression

Heterocyclic aromatic amines (HAAs) are harmful byproducts in food heating. Therefore, exploring the prediction and generation patterns of HAAs is of great significance. In this study, genetic algorithm (GA) and support vector regression (SVR) are used to establish a prediction model of HAAs based on heating conditions, reveal the influence of heating temperature and time on the precursor and formation of HAAs in roast beef, and study the formation rules of HAAs under different processing conditions. Principal component analysis (PCA) showed that the effect on HAAs generation increases with the increase of heating temperature and time. The GA-SVR model exhibited near-zero absolute errors and regression correlation coefficients (R) close to 1 when predicting HAAs contents. The GA-SVR model can be applied for real-time monitoring of HAAs in grilled beef, providing technical support for controlling hazardous substances and intelligent processing of heat-processed meat products.

Effect of Aggregated Lysozyme on Fluorescence Properties of Rose Bengal.

Protein aggregates cause abnormal states and trigger various diseases, including neurodegenerative disorders. This study examined whether the xanthene dye derivative Rose Bengal could track a series of conformational changes in protein aggregates. Using lysozyme as a model protein, aggregated proteins were prepared by heating under acidic conditions. The absorption spectra, steady-state fluorescence spectra, fluorescence quantum yield, fluorescence lifetime, and phosphorescence lifetime of a solution containing Rose Bengal in the presence of aggregated lysozyme were measured to identify their spectroscopic characteristics. The absorption spectrum of Rose Bengal changed significantly during the formation of agglomerates in heated lysozyme. Additionally, the fluorescence intensity decreased during the initial stages of the aggregation process with an increase in heating time, followed by an increase in intensity along with a red-shift of the peak wavelength. The decrease in quantum yield with a fixed fluorescence lifetime supported the formation of a nonfluorescent ground-state complex between Rose Bengal and the aggregated lysozyme. Based on the characteristic changes in absorption and fluorescence properties observed during the aggregation process, Rose Bengal is considered an excellent indicator for the sensitive discernment of aggregated proteins.

Use of optical absorption and scattering properties to monitor the change of chemical characteristics, particle structure and viscoelasticity during apple puree processing

This work explored the optical absorption (μa) and reduced scattering (μs') properties at 400–1050 nm (Vis-NIR) and 900–1650 nm (SWIR) of apple puree at different heating times to evaluate their changes in composition and structure. The optical absorption and scattering coefficients of μa and μs' decreased with increasing heating time. The specific μs' coefficients at 432 nm, 455 nm, 1183 nm and 1304 nm were related to particle structural changes. The partial least squares regression (PLSR) models based on μs' coefficients in the combined Vis-NIR and SWIR regions provided satisfactory estimations of puree particle area (Rp2 = 0.90) and particle perimeter (Rp2 = 0.85), whereas the μs' coefficients in the Vis-NIR region predicted puree viscosity (Rp2 = 0.83), elasticity modulus (Rp2 = 0.81) and viscous modulus (Rp2 = 0.78). Consequently, optical properties can be a potential tool to determine structural and rheological changes of apple puree.

Elastomeric Fire and Heat-Protective Materials Containing Functionally Active Microheterogeneous Systems.

This research aims to explore how functionally active structures affect the physical, mechanical, thermal, and fire-resistant properties of elastomeric compositions using ethylene-propylene-diene rubber as a base. The inclusion of aluminosilicate microspheres, microfibers, and a phosphorus-boron-nitrogen-organic modifier in these structures creates a synergistic effect, enhancing the material's heat-insulating properties by strengthening coke and carbonization processes. This results in a 12-19% increase in heating time for unheated sample surfaces and a 6-17% increase in residual coke compared to existing analogs. Microspheres help counteract the negative impact of microfibers on composition density and thermal conductivity, while the phosphorus-boron-containing modifier allows for controlling the formation of the coke layer.

Evaluation of the qualitative properties of the oil extracted from the mixture of Helianthus annuus and Nigella sativa seeds during heating

The oil obtained from black cumin (Nigella sativa) seeds has many health-effective properties, which is used in food applications and in traditional medicine. One practical method to extract its oil is mixing with other seeds such as sunflower (Helianthus anuus) seeds before oil extraction by press. The effectiveness of the cold-press oil obtained from the mixture of black cumin seeds (BS) and sunflower seeds (SF) in different proportions 100:0, 95:5, 90:10, 85:15 and 0:100 (w/w) was studied to evaluate their qualitative properties including peroxide value (PV), acid value, p-anisidine value (AnV), pigments (carotenoid and chlorophyll) content, polyphenols, and profile of fatty acids during heating process (30–150 min at 180 °C). The results revealed that the acid and p-anisidine value of the all samples enhanced with the extension of the heating time, and the peroxide value increased at the beginning of the heating and then decreased with the prolongation of the heating time (p < .05). With the increase of temperature and heating time, the peroxide of sunflower oil increased with a higher slope and speed than that of black seed and blends oil. Changes in the PV and AnV were the fastest in sunflower oil. Blending and heating caused considerable changes in the fatty acid composition of oils, especially myristic, palmitic, and stearic acids. Moreover, the levels of certain unsaturated fatty acids, namely linoleic, oleic, and linolenic acids declined after heating. The carotenoids, chlorophyll and total phenol content decreased gradually during heating treatments. Among extracted oils, SF:BS (15%) had the good potential for stability, with total phenol content of 95.92 (Caffeic acid equivalents/100 g), PV of 2.16 (meq O2/kg), AV of 2.59 (mg KOH/g oil), and AnV of 8.08 after the heating. In conclusion, oil extracted from the mixture of SF and BS can be used as salad and cooking oils with a high content of bioactive components and positive nutritional properties.

Effects of hydrothermal–microwave treatment on bending properties of teak in plantation

In order to study the bending properties of tropical tree species rich in organic extracts, the effects of temperature and time on the bending performance of hydrothermal treatment were investigated. The effects of power and time on bending performance under microwave heating conditions were investigated. It is found that the chemical composition does not undergo obvious degradation at 80°C–100°C, and the bending performance gradually becomes better with the increase in heating time; when the hydrothermal time exceeds 4 h, the bending performance varies with heating time. The growth is better than the difference, reaching the maximum at 4 h. When the water temperature is 140°C, the bending performance is negatively correlated with the heating time. When the hydrothermal treatment time is the same, the bending property becomes better as the temperature increases. The most reasonable process for microwave softening heating is with a power of 480 W and a heating time of 4 min. A softening treatment method combining water heat and microwave can achieve a better softening effect. When the final moisture content is controlled to 8%, the bending setting effect is the best. The optimum drying time is 6 h, and the optimum drying temperature is 50°C.

Study on migration behavior and mechanism of strong carcinogenic PAHs in oil to fume during frying using stable isotope method

The migration and distribution of four strong carcinogenic polycyclic aromatic hydrocarbons (PAH4) in oil to fume during frying were characterized by the stable isotope-labeled PAH4-d12. The results indicated that PAH4-d12 mainly migrated to heterogeneous oil fume, and their mobilities increased significantly with the increase in heating time and frying temperature, which were 0.48−1.08%, 0.96−1.21%, and 2.98−3.60% at 160, 180, and 200 °C, respectively. The established linear models proved that PAH4-d12 migrated through the carrying of heterogeneous fume, and the carrying ability of fume produced at 200 °C was significantly stronger than at 160 and 180 °C. For morphology, ultrafine fume (<1 μm) at 200 °C had the most emission and the strongest carrying ability for PAH4-d12. For components, the heterogeneous fume produced at 200 °C contained more unsaturated fatty acids and conjugated heterocyclic compounds, which could bind with PAH4-d12 in electrostatic force and π-π conjugate force for migration. This study explained the potential mechanism of oil fume components binding to PAH4 from molecular interaction.

Encapsulation of roast beef flavor by soy protein isolate/chitosan complex Pickering emulsions to improve its releasing properties during the processing of plant-based meat analogues

During the production of plant-based meat analogues (PBMA), a significant loss of flavor characteristic compounds in meat-flavor essences could be observed. Pickering emulsion-based encapsulation is an effective method to improve their stability. Therefore, a soy protein isolate (SPI)/chitosan (CS) complex Pickering emulsion was fabricated to encapsulate roast beef flavor (RBF) and further applied in the processing of PBMA. Our results indicated that the network structure of emulsions was dominated by elasticity, while hydrogen and covalent bonding interactions played important roles in the encapsulation process. The release rate of flavor compounds gradually increased with the increase of pH value, glutamine transaminase, NaCl content, heating temperature or heating time, while encapsulation significantly reduced the loss of characteristic aroma compounds. In addition, the releasing characteristics of aroma compounds and textural properties of PBMA were greatly improved by treating with RBF-loaded emulsions. Consequently, the emulsions were promising to improve the flavor quality of PBMA.

Effects of Cooking Methods on Caffeoylquinic Acids and Radical Scavenging Activity of Sweet Potato.

The effects of cooking methods, including steaming, deep-frying, and baking, on the phenolic content, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and isomerization of caffeoylquinic acids in sweet potato were investigated. A high correlation was observed between antioxidant capacity and total phenolic content. Deep-frying treatment resulted in higher antioxidant capacity with increasing heating time. The major phenolic components of raw sweet potat were 5-caffeoylquinic acid (CQA) and 3,5-dicaffeoylquinic acid (diCQA), which were reduced by heat treatment due to the isomerization of 5-CAQ to 3- and 4-CQA, and 3,5-diCQA to 3,4- and 4,5-diCQA. Moreover, 5-CQA was more stable than 3,5-diCQA even at 100 °C. Our results demonstrated that by controlling the cooking temperature and time, new bioactive compounds such as mono- and diCQA derivatives can be produced from sweet potato. These data indicate a potential approach for the development of new functional foods from sweet potato by controlling cooking temperature and time.

Roles of soybean β-conglycinin subunit fractions in fibril formation and the effects of glycinin on them

This research is aimed at exploring the fibrillation of soybean β-conglycinin (7S) subunits (αα′ and β) at 90 °C and pH 2.0, as well as the effects of glycinin (11S) on them. Fibril formation kinetics was monitored by measuring changes in thioflavin T (Th T) fluorescence intensity of the proteins. This analysis showed that αα′ subunits had a higher fibrillation capacity but slower fibril formation rate than the β subunit. Glycinin accelerated the rate of fibrillation of the αα′ and β subunits but weakened the fibril structure. The size of the fibrils first decreased and then increased with increasing heating time. Circular dichroism and intrinsic fluorescence spectroscopy analysis indicated that the β-sheet structure and hydrophobic interactions were important for the generation of ordered fibrils. Shear viscosity and transmission electron microscopy analysis suggested that the αα′ subunits formed relatively rigid fibrils that led to a high solution viscosity. In contrast, β subunit fibrils became unstable after prolonged heating, forming shorter fibrils (fragments) that tended to aggregate, which led to a lower solution viscosity. This research also suggested that the extension region of αα′ subunits played an important role in fibrillation, and the presence of the highly hydrophobic basic polypeptides of glycinin might be the main reason for the inhibition of soy protein fibrillation. Our analysis of soy protein fibrillization at the subunit level provides insights that might enhance the future application of soy protein fibrils as functional ingredients in foods.

Study on the formation mechanism of pea protein nanofibrils and the changes of structural properties of fibril under different pH and temperature

The functional performance of plant proteins can be enhanced by converting them into nanofibrils using controlled acid-heat treatments. Initially, the impact of heating time on the morphology and properties of nanofibrils prepared from pea proteins was assessed. The pea protein nanofibrils (PPF) were formed by heating at 85 °C and pH 2.0 for different times (0–24 h). Multiple analytical methods were then used to characterize the properties of the nanofibrils, including transmission electron microscopy (TEM), gel electrophoresis (SDS-PAGE), thioflavin T (ThT) fluorescence spectroscopy, molecular flexibility, and surface hydrophobicity. With increasing heating time, the protein molecules were gradually decomposed into small molecular weight peptides, which then assembled into nanofibrils. Initially, the length of the PPFs increased with heating time, but then it decreased, which was attributed to fibril fragmentation. In the food processing industry, pH and temperature are important factors affecting food preparation. For this reason, the effects of pH (2–9) and temperature (55, 85, 100 °C) on the properties of the nanofibrils were explored. These environmental conditions had a strong influence on the morphology and properties of PPFs. For instance, their flexibility increased with increasing pH, whereas their surface hydrophobicity decreased with increasing pH and temperature. Moreover, their charge went from positive to negative as the pH was ascended from below to above their isoelectric point. The findings of the structural properties of protein nanofibrils could provide some new insights into the wider application of nanofibrils in the food industry.

Analysis of thermal characteristics of building envelope structure for night storage heating

In order to understand the thermal characteristics analysis of nighttime thermal storage heating, the author proposes a study on the thermal characteristics analysis of nighttime thermal storage heating of building envelope structures. In some places, the writer will use an office room as a research object. The main purpose of the experiment is to measure, compare and analyze the surface temperature and heat flow rate of the room sample volume under two conditions: constant power 24 hour heating and night constant thermal power (12 hours) heating. In order to verify the accuracy of the dynamic thermal process of the heating room, the indoor air time variation will be performed along with the simulation results. Thermal performance parameters and characteristics of building thermal envelope heating effect of storage room were studied. The mathematical model of the thermal dynamic process of the heating room was established using the heat balance method and verified by experiments. According to the experiment, when the heating time increases from 5-12 hours, the additional heating consumption of the building heating system decreases by 500 Wh, and the additional heating consumption decreases to 19.4. In addition, it is important to change the heating time of the night-time packing model and the total heat accumulation. In addition, external wall insulation is useful in reducing additional heating consumption and building heating costs, but all heat transfer between model blocks is low. As the weather changes and the heat transfer coefficient of the external window increases, the additional amount of heat consumption and the additional value of heat consumption for heat storage of the building will increase. In the process of continuous heating operation, the additional heat consumption of the building heating system, the additional heat consumption gradually decreases, the heating equipment changes per hour, and the total heat accumulation of the night packing structure is important.

Behaviour of T-shaped stiffened concrete-filled steel tubular stub columns after uniform and non-uniform fire exposure

The post-fire behaviour of T-shaped stiffened concrete-filled steel tubular stub columns was investigated by the heating and residual mechanical performance tests. Key parameters, such as heating duration, number of surfaces exposed to fire and the influence of the stiffening steel bars, were studied. Temperature distribution, failure modes, mid-height strain curves, and load-displacement curves were obtained and discussed. The study reveals that the number of fire-exposure surfaces significantly affects the temperature distribution of the specimen section. Both the bearing capacity and compressive stiffness decrease with the increase of fire exposure surfaces and heating time, whereas the ductility follows an inverse pattern. The transverse stiffeners can enhance the mechanical performance of these stub columns, especially for ductility.

Design and experimentation of soil organic matter content detection system based on high-temperature excitation principle

With the continuous development of precision agriculture, the integration of sensor technology, control technology, and agricultural production activities has become increasingly tight. Soil organic matter (SOM) content is an important parameter in precision agriculture, closely related to the growth status of crops. Therefore, in-situ detection of SOM is an important part of variable seeding. Currently, most researchers use spectroscopy to detect SOM. However, the accuracy of spectroscopy is affected by factors such as soil texture, soil moisture content, soil iron oxide content, and soil particle size. Additionally, spectroscopic instruments are expensive and complex. To address these issues, this study designed and developed a real-time detection system for soil organic matter content based on the high-temperature excitation principle. The SOM detection system includes the selection and application of carbon dioxide sensor, the design of detection devices, the design of control systems, and the design of human–machine interface. Benchtop tests showed that the system's response time standard deviation was 0.252 s, indicating good stability. The filtering and cooling effects of the system met the requirements of the detection system. Five different natural soils were collected, and two of them, along with organic soil, were used to create artificially graded soil samples. Multiple linear regression was used for modeling, selecting six models with an R2 greater than 0.8 for accurate prediction of the remaining three different soil textures. The modeling results showed that a heating depth of 10 mm was susceptible to external interference, and the accuracy of the model with a heating depth of 15 mm was similar to that of the model with a heating depth of 20 mm. When the heating time exceeded 10 s, both models with different heating depths had an R2 greater than 0.8. The accuracy of the models increased with increasing heating time. Among them, the 15 mm-20 s model had the highest accuracy, with an average prediction accuracy of 91.4 %, a maximum accuracy of 94.1 %, and a minimum accuracy of 86.7 %. The experimental results showed that the SOM detection system designed in this study had good predictive capabilities for SOM in different soil textures and could achieve in-situ detection of SOM.