Volatile Release Research Articles

Volatile Compound Release from Oak Chips in Model Wine Media: Combined Influence of Toasting Degree, Size, Time of Contact, and Ethanol Content.

The effects of size, toasting degree, and time of contact on the release of volatile compounds from Quercus alba (L.) chips during a simulated fermentation and post-fermentative process were studied. The results obtained indicated that the large-size chips favored the release of furfural and furfuryl alcohol, while the small ones increased the concentration of cyclotene and maltol. The interaction between chip size and time of contact showed that the small-size chips are more sensitive to the increase of ethanol concentration for the extraction rate of some compounds (furfural, vanillin, maltol, cyclotene, whiskey lactones, and eugenol) compared to the large-size ones, increasing their concentrations at the end of maceration. The toasting degree of oak chips had a different influence on the volatile compounds studied. Cyclotene and guaiacol concentrations increased with the toasting intensity, whereas the extracted concentration of all compounds increased from light to medium-toasted chips, except for eugenol, and then decreased by further increasing the toasting level for 5-methylfurfural, whiskey lactones, eugenol, and only using high-level toasted chips for furfuryl alcohol, maltol, and vanillin. A possible protection effect of the chip size toward the possible degradation or volatilization losses of furfural for high toasting degrees was observed.

Identification and characterization of TMV-induced volatile signals in Nicotiana benthamiana: evidence for JA/ET defense pathway priming in congeneric neighbors via airborne (E)-2-octenal

Plants release a mixture of volatile compounds when subjects to environmental stress, allowing them to transmit information to neighboring plants. Here, we find that Nicotiana benthamiana plants infected with tobacco mosaic virus (TMV) induces defense responses in neighboring congeners. Analytical screening of volatiles from N. benthamiana at 7 days post inoculation (dpi) using an optimized SPME–GC–MS method showed that TMV triggers the release of several volatiles, such as (E)-2-octenal, 6-methyl-5-hepten-2-one, and geranylacetone. Exposure to (E)-2-octenal enhances the resistance of N. benthamiana plants to TMV and triggers the immune system with upregulation of pathogenesis-related genes, such as NbPR1a, NbPR1b, NbPR2, and NbNPR1, which are related to TMV resistance. Furthermore, (E)-2-octenal upregulates jasmonic acid (JA) that levels up to 400-fold in recipient N. benthamiana plants and significantly affects the expression pattern of key genes in the JA/ET signaling pathway, such as NbMYC2, NbERF1, and NbPDF1.2, while the salicylic acid (SA) level is not significantly affected. Our results show for the first time that the volatile (E)-2-octenal primes the JA/ET pathway and then activates immune responses, ultimately leading to enhanced TMV resistance in adjacent N. benthamiana plants. These findings provide new insights into the role of airborne compounds in virus-induced interplant interactions.

Comparative analysis of sorghum (C4) and rice (C3) plant headspace volatiles induced by artificial herbivory

ABSTRACT Acute stress responses include release of defensive volatiles from herbivore-attacked plants. Here we used two closely related monocot species, rice as a representative C3 plant, and sorghum as a representative C4 plant, and compared their basal and stress-induced headspace volatile organic compounds (VOCs). Although both plants emitted similar types of constitutive and induced VOCs, in agreement with the close phylogenetic relationship of the species, several mono- and sesquiterpenes have been significantly less abundant in headspace of sorghum relative to rice. Furthermore, in spite of generally lower VOC levels, some compounds, such as the green leaf volatile (Z)-3-hexenyl acetate and homoterpene DMNT, remained relatively high in the sorghum headspace, suggesting that a separate mechanism for dispersal of these compounds may have evolved in this plant. Finally, a variable amount of several VOCs among three sorghum cultivars of different geographical origins suggested that release of VOCs could be used as a valuable resource for the increase of sorghum resistance against herbivores.

Pyrolysis characteristics and kinetic parameters assessment of typical agricultural residues using high heating photothermal TGA

Understanding the complexity of thermal degradation characteristics, kinetic behavior, and thermodynamic parameters is pertinent for the efficient design and process optimization of large-scale conversion systems. Comparative assessment of pyrolysis characteristics and thermodynamic parameters of corn cobs (CC), peanut shells (PS) and sugarcane bagasse (SB) are investigated using high heating rates (100–1000 ℃/min) TGA results. Despite the effect of the heating rate increase on the degradation process of individual samples, increasing heating rates affect pyrolysis characteristics due to compositional differences. With increasing heating rates, the comprehensive pyrolysis index increased sporadically for CC (2.54–44.09 ×104%2/min2 ℃3) and PS (1.36–31.13 ×104%2/min2 ℃3), indicating easier release of volatiles at higher pyrolysis heating rates. The pyrolysis stability index (Rw), which relates to thermal degradation stability, presented an increasing trend (CC>PS>SB) with a heating rate increase (≥106%). Kinetic parameters estimated using model-free methods showed that the activation energies of CC and PS were significantly lower than that of SB. Comparative evaluation of fractional conversions and kinetic parameters using traditional and modified parallel models showed that the double random pore model (DRPM) fitted the best for simulating the experimental results at higher heating rates than other models. The change in Gibbs free energy (ΔG) trend for PS and SB showed a deviation, suggesting reaction difficulties due to higher temperature demands.

Role of Maillard reactions in co-pyrolysis of lignite and spent coffee grounds: Fixation of nitrogen in semicoke and improved adsorption of phenols

Semicoke derived from lignite and biomass has been utilized in soil remediation and activated sludge treatment. Nitrogen-doping treatment has been utilized to improve adsorption capacity of semicoke for phenols (such as humic acids). Known as nitrogen-rich biomass residue, spent coffee grounds (SCG) may serve as nitrogen resources when co-pyrolyzed with lignite. But impacts of SCG on structure and adsorption capacity of semicoke in co-pyrolysis have not been confirmed. In consideration of proteins in SCG, nitrogen fixation and the impacting mechanism have not been sufficiently confirmed. In this work, nitrogen fixation between lignite and SCG during co-pyrolysis were investigated by thermogravimetric analysis (TG) and pyrolysis experiments. Corresponding mechanism were speculated and confirmed by in-situ diffuse reflectance infrared Fourier transformation spectra (DRIFT) and mass spectrum (MS). Impacts of nitrogen fixation on adsorption of phenols on semicoke were investigated by X-ray photoelectron spectroscopy (XPS), adsorption kinetics analysis and density functional theory (DFT) calculations. Compared to theoretical values, higher contents of N have been obtained in co-pyrolyzed semicoke (N: 2.89%; pyridinic N: 44.86%), which implied N fixation and cyclization reactions. Fixation mechanism can be explained by formation of Amadori/Heyns intermediates in Maillard reactions. Release of volatiles and capture of NH3 are crucial in 340–440 °C range, which result in nitrogen fixation. Then formation of pyrrolic and pyridinic N can be explained by cyclization reactions and decomposition of Amadori/Heyns intermediates in 550 °C pyrolysis. Enrichment of pyridinic N, pyrrolic N and CO might enhance adsorption of phenols by offering binding sites for formation of hydrogen bonds. Both C, N fixation and improved adsorption capacity (27.80 mg/g) have been realized for 7:3–550 semicoke. Consequently, doping treatment with typical nitrogen-rich biomass (SCG) may be feasible to enhance adsorption of phenols onto semicoke, based on selection of raw materials and pyrolysis conditions.

Pyrolysis kinetics and thermal degradation characteristics of coffee, date seed, and prickly pear wastes and their blends

This study's objective was to emphasize the renewable lignocellulosic biomasses' energy potential by thermally describing them. The TG/DTG/DTA procedures were used to examine the thermal pyrolysis behavior of coffee wastes (CW), date seeds (DSM), prickly pears (PP), and two blends (50%CW/50%DSM and 33.3%CW/33.3%DSM/33.3%PP by weight), and their physico-chemical compositions were identified and assessed. The activation energy (E) of all tested samples was predicted using iso-conversional models like Friedman (FR), Starink (ST), Kissinger-Akahira-Sunose (KAS), and Ozawa-Flynn-Wall (OFW), and the frequency factor (A) was calculated based on the acquired (E) values utilizing the chemical reaction mechanisms (C1–C8). SEM, EDX, and FTIR techniques were used to examine the microstructure, mineralogy, and functional group present in the studied samples. Every DTG profile displayed a rightward shift when the heating rate (β) rose to higher temperatures. The difference in the average activation energy (Eav) values between the ST, OFW, and KAS models, except for the blend (1), does not surpass 5 kJ/mole. Increases in the (β) value, particularly for blends, were significantly correlated with increases in the maximum pyrolysis rate (−RP), pyrolysis index (CPI), pyrolysis stability index (RW), and volatile release index (Ddev). The ΔGav discrepancies between the results from all kinetic models for all samples varied from 1 to 7 kJ/mole. A little potential energy barrier was noticed when comparing the (Eav) to the average enthalpy (ΔHav).

Fast co-pyrolysis behaviors and synergistic effects of corn stover and polyethylene via rapid infrared heating

Rapid infrared heating with fast heating rates and the capacity to load materials on the gram scale help investigate the co-pyrolysis behaviors, minimizing the gap of materials’ pyrolysis temperature and volatile release during the co-pyrolysis. This work explored the effects of temperature and heating rate on the co-pyrolysis product s behaviors and synergistic interactions of corn stove and polyethylene. Initial increases in oil yield were followed by decreases when the heating rate rose, and when the temperature increased from 500 °C to 600 °C, the oil yield rose from 17.91 wt% to 20.58 wt% before falling to 14.75 wt% at 800 °C. High heating rate promoted the oil generation, and the maximum oil yield was at 25 °C/s with varying heating rates from 15 °C/s to 35 °C/s. The pyrolysis gas produced at 25 °C/s exhibited the highest LHV (Low heating value) and lowest CO2 yield, which were 17.23 MJ/nm3 and 39.29 vol%, respectively. The suitability of heating rate and temperature may improve the interaction between H-radicals of PE and oxygenated groups of CS to generate stable macromolecular compound and enhance oil production. GC–MS studies of the oil products demonstrated that oxygenated compounds such as furans, phenols and acids from lignocellulosic depolymerization had been converted to high molecular weight long chain alcohols (mostly C26, C20 and C14 alcohols) via stronger interactions during fast infrared-heated co-pyrolysis. The alcohols increased from 32.29 % to 65.06 % as temperatures rose from 500 °C to 800 °C. Few furan heterocycles, acids and phenols were detected, suggesting that the oil presented higher quality and stronger synergistic effects. Rapid infrared heating accelerated the synergistic effects between volatile-volatile interactions during co-pyrolysis of corn stover and polyethylene, and the increases in temperature and heating rates further enhanced the release of many volatile substances and the formation of fine pores. Raman results showed char of 600 °C deposited more pure aromatic structures, the influence of temperature on aromatization was stronger than that of heating rate.

Cinnamon essential oil vapor alleviates the reduction of aroma-related volatiles in cold-stored "Feicheng" peach using HS-GC-IMS.

"Feicheng" peach is popular for its unique aroma, but its defect of being highly sensitive to chilling injury (CI) often leads to aroma loss and internal browning. Essential oils (EOs) are often used to enhance the antioxidant capacity of plants and fruits, as well as to trigger their defense against biotic/abiotic stresses. This study aimed to examine the effect of cinnamon essential oil (CEO) vapor treatment on the aroma quality of peach fruit during cold storage using HS-GC-IMS. The results showed that 50 μL/L CEO vapor reduced the severity of internal browning (IB) in peaches at the stage of 7 ~ 21 d during refrigeration (Significantly, the L* value was higher and the IB index was lower than that of control, p < 0.05). Meanwhile, the evident reduction or loss of aroma content caused by CI was restored to a higher level than the control (p < 0.05). Furthermore, CEO treatment promoted the release of aroma-related volatiles as evidenced by more propyl acetate, and the dimer of amyl acetate, isoamyl acetate, butyl acetate detected than that on harvest day and no-treated group after 21 d of cold storage plus 2 d of shelf life. Genes of PpLOX1, PpLOX2, PpHPL1 and PpADH1 associated with aroma-related volatile biosynthesis revealed higher transcript abundance in peach fruits treated with CEO than the control (p < 0.05). Overall, our study demonstrated that CEO in vapor phase may be beneficial to alleviate the quality deterioration in aroma and flesh color of "Feicheng" peaches caused by CI, which lays a theoretical reference for maintaining postharvest quality of peach fruits.

Revealing roles of CO2 and N2 in pressurized hydrothermal carbonization process for enhancing energy recovery and carbon sequestration

In this study, CO2– and N2-pressurized hydrothermal carbonization processes were investigated to understand the catalytic effects of CO2 on hydrochar production and its quality (e.g., surface properties, energy recovery, and combustion behaviour). Both CO2– and N2-pressurized HTC processes could enhance the energy recovery (from 61.5% to 63.0–67.8%) in hydrochar by enhancing the dehydration reactions. Nonetheless, the two systems exhibited contrasting trends in volatile release, oxygen removal, and combustion performance as a function of increasing pressure. High N2 pressure enhanced deoxygenation reaction, facilitating the release of volatiles and increasing the hydrochar aromaticity and combustion activation energy (172.7 kJ/mol for HC/5N). Without the contribution of CO2, excessively high pressure may cause an adverse impact on the fuel performance owing to higher oxidation resistance. This study presents an important and feasible strategy to utilise CO2-rich flue gas in the HTC process to produce high-quality hydrochar for renewable energy and carbon recovery.

Combined Analysis of Volatile Compounds and Extraction of Floral Fragrance Genes in Two Dendrobium Species

Many species of the Dendrobium genus are traditional Chinese herbal medicine and ornamental plants. Flower fragrance is one of the most important horticultural ornamental characters and plays a crucial role in the ecology, economy, and aesthetics of plants. However, the volatile constituents and key regulatory genes related to floral biosynthesis are poorly understood. In this experiment, the flowers from two species of Dendrobium with high-scent smells, Dendrobium moniliforme (L.) Sw. (D. moniliforme), and light-scent smells, Dendrobium nobile “H1” (D. “H1”), were selected. The aim of this study was to explore the key gene expression profiles of floral biosynthesis by combining volatile constituent determination and transcriptome analysis in two different Dendrobium species. Physiological determination results showed that 60 volatile compounds were identified in D. moniliforme and 52 volatile compounds were identified in D. ‘H1’ flowers in four flowering stages, and the full bloom stage was the most complicated stage because there were 41 and 33 volatile compounds, respectively. These compounds belong to terpenes, aromatics, fatty acids, nitrogenous compounds, ketones, alcohols, and alkanes, respectively. The components identified in the gynandrium and petals revealed that the petals were probably the most important sites affecting the release of volatiles. The relative content of terpene compounds was the highest, with 77.25% (D. moniliforme) and 50.38% (D. “H1”), respectively. Transcriptome analysis showed that differentially expressed genes (DEGs) were highly enriched in terpenoid backbone biosynthesis and that four linalool synthetase (LIS) genes were up-regulated in high-scent smell species. This study is helpful to explore the key genes of flower fragrance and provides a theoretical basis for further understanding of the regulatory molecular functions of floral synthesis and release, as well as for the cultivation of new aromatic species.

Characterization of volatiles evolved during vacuum sintering of lunar regolith simulants

This work describes an experimental vacuum setup, designed for sintering of lunar regolith simulant materials, and its application to real-time characterization and identification of volatile species, resulting from in vacuo decomposition of the non-lunar components in the materials. We carried out a thorough experimental system characterization, highlighted critical aspects (temperature, pressure) with respect to regolith sintering, identified the volatile release / sample environment correlations, and postulated the need for high-vacuum capabilities in light of the high gas loads, generated by the simulants. We detailed the identification process of specific released gas species (H2O, NO, H2S, CO2, SO2, SO3, HCl, HF, etc.) using mass spectrometry, and advanced the use of them as markers for thermally activated processes, such as dehydration of hydrates, decomposition of major non-lunar phases (carbonates and sulfates) and lesser-represented components (nitrates, fluorides, chlorites, etc.). Quantification of individual decomposing phases is feasible within reason despite the inherent limitations of mass spectrometry. The methods, detailed in this paper, are intended for use in developing a better understanding of lunar regolith simulants with respect to sintering applications.

Effect of air staging and porous inert material on the emission of volatile organic compounds in solid biomass combustion

The present paper delves into experimental data to assess the effects of the inclusion of a zirconium porous medium in the emissions of a laboratory-scale biomass combustor, with a focus on particulate matter and volatile organic compounds. While other studies have focused on the effects of the material on solid particulate matter or gaseous emissions, this research is focused on volatiles, their capture and storage. A novel sampling train for the capture of volatiles has been designed based on active carbon adsorption on a refrigerated environment, and its performance was evaluated through thermogravimetric analysis, showing the affinity of this porous medium towards lighter organic compounds. The retention time of the sample was also studied, and the data revealed that after three to six hours the sample had degraded significantly when stored in airtight plastic bags inside a glass desiccator at 22 °C. An analysis of the particulate matter emitted was also carried out. Volatile organic compounds were also found to follow the behavior of particulate matter, with the scenarios where low solid particles were emitted being also those in which volatiles release was minimized.

Controlled volatile release from β-sitosterol-based oleogels based on different self-assembly mechanisms

This study examined how the self-assembly mechanisms of β-sitosterol-based oleogels influenced the release of volatile compounds. Microscopy, X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements showed that the three β-sitosterol-based oleogels (β-sitosterol + γ-oryzanol oleogels (SO), β-sitosterol + lecithin oleogels (SL) and β-sitosterol + monostearate oleogels (SM)) had significant differences in their microstructures, which were formed via different self-assembly mechanisms. SO exhibited the highest oil binding capacity (OBC), complex modulus (G*) and apparent viscosity. Dynamic and static headspace analyses suggested that network structure of β-sitosterol-based oleogels affected the release of volatile components. SO showed the strongest retention effect, followed by SL and SM. The release of volatile compounds mainly related to structural strength and compositions of oleogels. These results indicated that β-sitosterol-based oleogels formed with different self-assembly mechanisms have the potential to serve as effective delivery systems for controlling the release of volatile compounds.

Effect of red mud additive on the combustion performance of lignite and sulfur fixation behaviors

ABSTRACT To reveal the role of red mud (RM) as the catalyst during the combustion behavior of lignite, two kinds of RM from Bayer red mud (SR) and sintering red mud (GR) were chosen to investigate the catalytic combustion behaviors of lignite under different oxygen contents, the action mechanism and the sulfur fixation performance by the thermogravimetric analysis (TGA) and fixed-bed reactor. Flynn–Wall–Ozawa (FWO) method was used to study the combustion kinetics. The results showed that RM can promote the release of pyrolysis volatiles and significantly improve the ignition performance of coal. Moreover, the improvement effect of RM becomes more noticeable with the increase of O2 content. RM decreased the ignition and burnout temperatures of the char combustion. The types of RM exert different catalytic properties owing to different compositions. Under oxygen-rich conditions, the apparent activation energy in the early stage of coal combustion can be significantly reduced by RM. In addition, RM enhances the peak temperature during constant combustion of coal, improves combustion rate, shortens the burnout time, and remarkably reduces SO2 emission in exhausted gas. About 83.7% SO2 in combustion gas produced at 700°C was reduced at the SR addition of 25 wt%, indicating RM is a potential and cheap catalyst for high-effective coal combustion.

In-situ catalytic pyrolysis of biomass with nickel salts: Effect of nickel salt type

Aiming to investigate the role of anions in the process of biomass pyrolysis catalyzed by nickel salts, four types of nickel salts (Ni(NO3)2, NiSO4, (CH3COO)2Ni, NiCl2) were impregnated on reed to investigate their effects on biomass pyrolysis. The results showed that nickel salts inhibited the release of volatiles from biomass and increased the yield of bio-char, with NiCl2 being the most effective. NiSO4 dramatically increased the specific surface area and graphitization of bio-char, and improved the selectivity of phenolic compounds in bio-oil (62.27 area%) as well as the concentration of CO in pyrolysis gas (37.78 vol%). The addition of NiCl2 enhanced the selectivity of ketone-rich oil (26.95 area%) and hydrogen-rich gas (56.39 vol%). Ni(NO3)2 is weaker than other nickel salts in catalyzing the cleavage of macromolecular compounds. This research offers a prospective approach to control the distribution and quality of pyrolysis products by using suitable catalyst precursors.

Effects of moisture on soot generation and ignition of coal particle: Investigation and evaluation with OH-planar laser induced fluorescence

Coal with a high moisture content is increasingly being utilized in power generation. However, the influence of moisture on coal ignition and soot generation characteristics remains unclear. Understanding the effect of moisture on coal ignition and soot generation characteristics is important for improving energy efficiency in coal utilization. The characteristics of soot generation and ignition of lignite coal including different contents of moisture (0%, 5%, 10%, 15%) were studied with Planar Laser Induced Fluorescence of OH radicals (OH-PLIF) on a novel concentrating photothermal platform. The results showed that the ignition delay time (tign) of coal and observed soot generation during volatile combustion by the observation of flame luminosity both increased as the moisture content of the coal particles increased from 0% to 15%. The observed increase in tign corresponded to the decreased OH intensity during the ignition. Similarly, the increased generation of soot during volatile combustion corresponded to the increased OH intensity resulting from increased moisture content in the coal. Before ignition, the steam surrounding the coal particle inhibits the release of volatiles. Thus, the formation of fuel molecules (RH) is reduced. Simultaneously, the inhibitory effect of moisture on RH leads to a decrease in H atoms, which further results in a decline in OH radical concentration resulting from the reaction H + O2→OH + O. The combined effect of reduced RH and OH concentrations inhibits ignition for coals containing moisture. During volatile combustion, although OH is commonly acknowledged as the primary oxidant for soot, the increase in OH facilitates gasification reactions, thereby promoting the massive release of volatiles. These volatiles, through processes such as nucleation reactions, contribute to the formation of an increased amount of soot, consequently resulting in an elevated formation of soot in coal with higher moisture content.

Variation and Natural Heritability of Blueberry Floral Volatiles.

Vaccinium corymbosum (highbush blueberry) in British Columbia relies on honeybee pollination for a reliable fruit set. As floral volatiles may help explain pollinator preference for blueberry, we surveyed components of variation for volatiles using gas chromatography-mass spectrometry (GC/MS). Principal component analysis of GC chromatogram peaks revealed a grouping of cultivars by a biosynthetic pathway that also corresponds with their known pedigree. To identify genetic variance, we identified 34 chemicals with adequate sample sizes. We estimated "natural heritability" (using uncontrolled crosses in natural environments) in two ways: (1) as "clonal repeatability," which is equivalent to broad-sense heritability and is an upper bound for narrow-sense heritability, and (2) "marker-based heritability," which serves as a lower bound for narrow-sense heritability. Both methods indicate that heritability is relatively low, ca. 15%, and variable among traits. This is expected as the floral volatile release is changeable and dependent on environmental conditions. It might be possible to use highly heritable volatiles for breeding.

Experimental study on the effect of temperature and oxygen on pyrolysis-gasification decoupling characteristics of Yili coal

Pyrolysis, as the initial process of coal clean utilization, is essential to ensure the operation of pyrolysis-gasification decoupling technology. This paper aims to investigate the effects of temperature and oxygen content on coal pyrolysis product distribution and the char structure and reactive properties. Results demonstrate that in the range of 800–1100 °C, the increase in temperature is conducive to the release of volatiles and tar cracking, to enhance the gas phase yield and syngas concentration. However, as Raman spectroscopy analysis shows, higher temperature (>900 ℃) will intensify the graphitization of char, which is not conducive to the next gasification step. In addition, oxygen introduction at 900 ℃ can accelerate the release of volatiles and intensify the occurrence of depolymerization reaction, which increased the gas yields of CO and CO2 in the gaseous product. Besides, the presence of trace oxygen in the pyrolysis process reduces the degree of coal char graphitization and improves the gasification reactivity. However, at high oxygen content (8 %) conditions, combustion occurs on the surface of the char as SEM results show, which destroys the structure and reduces the gasification activity of the char. Hence, the pyrolysis product distribution and post-pyrolysis char gasification activity can be adjusted by introducing trace oxygen in pyrolysis-gasification decoupling technology.

Effect of Fat to Lean Meat Ratios on the Formation of Volatile Compounds in Mutton Shashliks.

This study aimed to investigate the release of volatile compounds in mutton shashliks (named as FxLy, x-fat cubes: 0-4; y-lean cubes: 4-0) with different fat-lean ratios before and during consumption, respectively. In total, 67 volatile compounds were identified in shashliks using gas chromatography/mass spectrometry. Aldehyde, alcohol, and ketone were the major volatile substances, accounting for more than 75% of the total volatile compounds. There were significant differences in the volatile compounds of mutton shashliks with different fat-lean ratios. With the increase of the fat content, the types and content of volatile substances released also increase. However, when the percentage of fat exceeded 50%, the number of furans and pyrazine, which were characteristic of the volatile compounds of roasted meat, was decreased. The release of volatiles during the consumption of mutton shashliks was measured using the exhaled breath test and the results showed that adding an appropriate amount of fat (<50%) helps to enrich the volatile compound components in the mouth. However, shashliks with higher fat-lean ratios (>2:2) shorten the mastication duration and weaken the breakdown of bolus particles in the consumption process, which is not conducive to the release potential of volatile substances. Therefore, setting the fat to lean ratio to 2:2 is the best choice for making mutton shashliks, as it (F2L2) can provide rich flavor substances for mutton shashliks before and during consumption.

Comparison of the effects of antimony trioxide and zinc, calcium and copper stannates on the thermal degradation of polyamide-6,6

Thermal and thermo-oxidative decompositions of polyamide 6.6 (PA66) in the presence and absence of zinc (ZnSt), calcium (CaSt) and copper stannates (CuSt), and in the presence of antimony trioxide (ATO), have been studied by TGA-FTIR and pyrolysis GC/MS. It is shown that whilst ATO has a negligible effect on the rate of decomposition and products of pyrolysis under both slow heating on a TGA and rapid heating on a pyrolysis/GC/MS apparatus, the stannates have a catalytic effect in the order ZnSt ≈ CaSt > CuSt, evident through release of volatiles at a lower temperature and in a different product distribution following rapid high temperature pyrolysis. In particular, rapid pyrolysis at high temperature in the presence of the stannates promotes formation amongst the pyrolysis products of, for example, 6-aminohexanenitrile. 1,6-hexanediamine, 1-methyl-3-formylindole and 1,2,3,7-tetramethylindole, whilst yields of others are reduced, e.g., hexanedinitrile, caprolactam, diaminomethylidene(2-hydroxypropyl)azanium, prop‑2-enenitrile (acrylonitrile) and azacyclodecan-5-ol. We suggest that these effects arise from complexation of the electropositive metal in the stannate (Zn, Ca or Cu) with the C=O groups of PA66, thus weakening the C(O)-C and C-N bonds adjacent to the C=O groups. The fact that ZnSt has the most pronounced effect on the pyrolysis product distribution and CuSt the least, we explain in terms of the order of electropositivity of the metal (Zn>Ca>Cu).