Thermal Reaction Models Research Articles

Novel Pink Pigments Produced by Thermal Interaction of Theaflavins, Theanine, and Glucose: Color Formation, Isolation, and Structural Characterization.

A color-deepening effect of theaflavins on the theanine-glucose thermal reaction model was revealed. Generated chromogenic intermediates in the initial stage and an accelerated browning rate through the promoted degradation of theanine-glucose Amadori rearrangement product in the intermediate and final stages are responsible for the color-deepening effect. Four pink-to-red theaflavin-theanine intermediates were verified as theaflavinies referencing the nuclear magnetic resonance and liquid chromatography-mass spectrometry information on theaflavins and l-theanine, including one accurately identified as theaflavinie 4. Theaflavinie 4 showed two maximum absorption peaks at 401 and 506 nm with parallel intensities, which resulted in a significant dichromic color change from pale pink to orange and red. Theaflavinies also could undergo further thermal reactions to yield brown polymers under higher temperatures (130 and 140 °C). This research provided new insight into realizing thermally formed polymers during black tea processing, which may be formed by oxidation products and amino acids or proteins through non-enzymatic thermal reactions.

Numerical Simulation Research on Slow cook-off of Warhead of DNAN-based Melt-cast Explosive

RBOE explosive is a new type of DNAN-based insensitive melt-cast explosive with good thermal safety. In order to study the response characteristics of RBOE explosives under slow cook-off conditions, this study carried out a numerical simulation study of slow cook-off for the ϕ35mm×116mm RBOE cylindrical warhead. According to the thermal decomposition characteristics of each component of the explosive, the thermal reaction model of the RBOE explosive was established. Numerical simulation of RBOE warhead cook-off was carried out at a heating rate of 1K/min; the internal temperature rise curve, phase change cloud diagram and ignition cloud diagram of the warhead were obtained, and the thermal response characteristics of the RBOE explosive were analyzed.

Degradation of 2-Threityl-Thiazolidine-4-Carboxylic Acid and Corresponding Browning Accelerated by Trapping Reaction between Extra-Added Xylose and Released Cysteine during Maillard Reaction.

2-Threityl-thiazolidine-4-carboxylic acid (TTCA), a nonvolatile precursor of flavor and color, is considered to be more stable than its isomeric Amadori compound (ARP). The degradation behavior of TTCA favors higher temperatures and pH. In order to adjust and control the thermal degradation of TTCA to improve its food processing adaptability, a TTCA-Xyl thermal reaction model was constructed to explore the effect of extra-added Xyl on the thermal degradation behavior of TTCA. The results confirmed that the extra-added Xyl was involved in the degradation pathway of TTCA and accelerated its depletion, thus promoting the formation of characteristic downstream products of TTCA including some α-dicarbonyl compounds, and consequently accelerating the browning formation. The isotope-labeling technique was further applied to confirm that the added Xyl could trap the Cys released from the decomposition of ARP and formed additional TTCA, which could promote the movement of chemical equilibrium and gradually accelerate the degradation rate of TTCA as well as melanoidins formation. The higher pH value could even promote this phenomenon.

Effect of conducting filament radius on local temperature and activation power of ON-state ReRAM device

The formation and disruption of conducting filament (CF) are responsible for the SET/RESET switching of resistive random access memory (ReRAM). The ReRAM enters into a low resistive state soon after the complete formation of CF and the process is followed by the radial growth of CF during the ON-state. The present investigation aims to develop a numerical and analytical model to realize the effect of CF radius on local temperature rise and activation power, combining the thermal reaction model (TRM) and power signature model. The numerical investigation is carried out using finite element method to obtain the local temperature rise and temperature distribution across the device. The numerical results show a similar increment pattern of local temperature as of analytical TRM i.e. the local temperature increases linearly with a rapid growth rate of ∼63% in initial CF radii and then gradually attains a steady-state temperature with ∼10% increment in higher CF radii. The relationship between resistance and compliance current is calculated which obeys the same reported trend in other switching oxides like TiO X , CuO, NiO. Additionally, the activation power is determined where the resistance decreases (101.87–0.25 KΩ) due to the CF radial growth, which results in four orders of exponential increment in activation power from ∼0.04 µW to 500 ± 100 µW. The power signature of numerical TRM is validated with that analytical TRM where the device attends a steady-state temperature after a certain CF radius (>25 nm) along with the activation power.

Kinetics of α‑dicarbonyl compounds formation in glucose-glutamic acid model of Maillard reaction.

As a potential health hazard, α‐dicarbonyl compounds have been detected in the thermally processed foods. In order to investigate the formation kinetics of α‐dicarbonyl compounds, liquid chromatography‐electrospray tandem mass spectrometry was employed to determine the content of α‐dicarbonyl compounds in glucose‐only and glucose‐glutamic acid (glucose‐Glu) thermal reaction models. The 3‐deoxyglucosone content was significantly higher than 6 α‐dicarbonyl compounds at 90–110℃, 0–6 hr in the two tested systems. The glutamic acid promoted the content accumulation of 1‐deoxyglucosone, diacetyl, methylglyoxal, and glyoxal, whereas inhibited the content of 3‐deoxyglucosone and 3,4‐dideoxyglucosone. Three‐fifths of the tested compounds content increased linearly with time increasing, but in glucose‐only system, the 1‐deoxyglucosone content increased logarithmically at 95–110℃ over reaction time. The formation of glucose (100–110℃, glucose‐only and glucose‐Glu), 5‐hydroxymethylfurfural (100–110℃, glucose‐only), 1‐deoxyglucose (105–110℃, glucose‐Glu), 3,4‐dideoxyglucosone (110℃, glucose‐Glu), glyoxal (95–110℃, glucose‐Glu) and diacetyl (90–95℃, glucose‐Glu) could be well fitted by exponential equation. Shortening the heating time and reducing heating temperature (except glyoxal in glucose‐only system) were the effective methods to decrease α‐dicarbonyl compounds content in the two tested systems. Additionally, high temperature could also reduce α‐dicarbonyl compounds content, such as 3‐deoxyglucosone (≥110℃, glucose‐only), 1‐deoxyglucosone (≥110℃, glucose‐only), glucosone (≥110℃, glucose‐only; ≥100℃, glucose‐Glu), methyloxyl (≥110℃, glucose‐only; ≥100℃, glucose‐Glu), diacetyl (≥110℃, glucose‐only), and glyoxal (≥100℃, glucose‐Glu).

Kinetics of 5-hydroxymethylfurfural formation in the sugar-amino acid model of Maillard reaction.

As a potential health hazard, 5-hydroxymethylfurfural (HMF) has been detected in thermally processed foods high in sugar and amino acids. In order to analyze HMF quantitatively and investigate the kinetics of its formation, high-performance liquid chromatography was employed to determine the content of HMF in six sugar-amino acid thermal reaction models. In thermal reaction models, formation of HMF was significantly affected by sugar and amino acid composition, pH value and heating conditions. HMF formation increased with increasing sugar and amino acid (cysteine excepted) content, temperature and reaction time. A maximum amount of HMF of 1.50 g kg-1 was detected in the sucrose-glutamic acid model at 110 °C and 6 h. Low pH value and added acidic amino acids promoted the formation of HMF, especially in the sucrose-containing system. HMF formation followed first-order kinetics in four models, including the model of glucose-cysteine, glucose-glutamic acid, glucose-leucine and sucrose-leucine. In contrast, HMF formation followed zero-order kinetics in the model of sucrose-glutamic acid. The quantity of HMF increased as the quantity of sugar and amino acid increased (cysteine excepted) in six tested models. © 2018 Society of Chemical Industry.

Development of Ag/ZnO/FTO thin film memristor using aqueous chemical route

The present paper report the development of the Ag/ZnO/FTO memristor device using a simple aqueous chemical route. The structural, electrical, morphological and optical properties of Ag/ZnO/FTO memristor device are characterized using X-Ray diffraction (XRD), semiconductor characterization unit, field emission scanning electron microscopy (FESEM), and UV-Vis-NIR spectrophotometer respectively. The fabricated memristor device shows bipolar resistive switching behavior within low operating voltage (±0.88V). The hysteresis loop in the I–V plane is the fingerprint characteristics of memristor and same has been seen in developed device. Furthermore, the effect of temperature on ZnO based memristor device is investigated using the thermal reaction model. The results suggested that, temperature of conductive filaments increases rapidly and affected the memory window of memristor.

Aroma extract dilution analysis of a beef flavouring prepared from flavour precursors and enzymatically hydrolysed beef

AbstractVolatile components of a beef flavouring prepared from a thermal reaction model system of enzymatically hydrolysed beef/amino acids/sugars were extracted by simultaneous distillation/extraction (SDE) and dynamic headspace sampling (DHS) methods, then subjected to aroma extract dilution analysis (AEDA) and dynamic headspace dilution analysis (DHDA) methods; 32 and 48 odour‐active peaks were revealed from the SDE and DHS isolates, respectively. With the highest flavour dilution (FD) factors, 2‐methyl‐3‐furanthiol, 3‐methylthiopropanal and 2‐furanmethanethiol were identified as the key aroma compounds of the beef flavouring by both sample preparative methods, SDE and DHS. Moreover, methyl propyl disulphide, ethyl‐2‐methylbutyrate, allyl methyl disulphide, thiazole, 1‐butanol, 1‐nonen‐3‐one, 2‐ethenyl‐3,5‐dimethylpyrazine, (E, E)‐2,4‐heptadienal and 2‐undecenal were also identified as important aroma components of the beef flavouring. Copyright © 2008 John Wiley & Sons, Ltd.

Consideration of switching mechanism of binary metal oxide resistive junctions using a thermal reaction model

The authors investigated the resistive switching of transition metal oxide (TMO) junctions by applying a short voltage pulse and found that the response time of the “reset” process was dependent on the resistance in the low resistive state. By using a thermal conductive equation to calculate the temperature of the filamentary conductive path in the TMO film, the temperature in the reset process was estimated to reach the same temperature grade in each reset. On this basis, the previous experimental relation is well explained by assuming a general thermal chemical reaction model for the reset process.

A numerical study of coal devolatilization in an entrained-flow reactor

This paper reports a numerical study of the steady, turbulent reacting two-phase flow in an experimental axisymmetric bench-scale entrained-flow reactor using a readily available computer code. Emphasis is focused on the temperature history and heating rates of individual coal particles. This information, which is difficult to obtain experimentally, plays an important role in assessing coal devolatilization experiments. Numerical simulations are presented and analyzed for reactor temperatures in the range 1000–1650 K (1500–2500°F). The coal considered is of subbituminous type with a particle size range of 20–100 microns. The results illustrate the details of the coal devolatilization process as predicted by a two-competing thermal reaction model. In particular, the mechanism by which the particle temperature history affects this process is elucidated. It is shown that the measured trends of volatile yields with reactor temperature can be predicted with this simple model provided that the temperature history is known. The predicted gas component yields agree fairly well with measurements in the higher-temperature range ( > 1300 K). In the lower-temperature range, the equilibrium chemistry assumption seems not to be appropriate.