Determination of double bond positions in unsaturated fatty acids by pre-column derivatization with dimethyl and dipyridyl disulfide followed by LC-SWATH-MS analysis.

Comprehensive in-depth structural characterization of free mono-unsaturated and polyunsaturated fatty acids often requires the determination of carbon-carbon double bond positions due to their impact on physiological properties and relevance in biological samples or during impurity profiling of pharmaceuticals. In this research, we report on the evaluation of disulfides as suitable derivatization reagents for the determination of carbon-carbon double bond positions of unsaturated free fatty acids by UHPLC-ESI-QTOF-MS/MS analysis and SWATH (sequential windowed acquisition of all theoretical mass spectra) acquisition. Iodine-catalyzed derivatization of C = C double bonds with dimethyl disulfide (DMDS) enabled detection of characteristic carboxy-terminal MS2 fragments for various fatty acids in ESI negative mode. The determination of double bond positions of fatty acids with up to three double bonds, the transfer of the method to plasma samples, and its limitations have been shown. To achieve charge-switching for positive ion mode MS-detection, derivatization with 2,2'-dipyridyldisulfide (DPDS) was investigated. It enabled detection of both corresponding characteristic omega-end- and carboxy-end-fragments for fatty acids with up to two double bonds in positive ion mode. It provides a straightforward strategy for designing MRM transitions for targeted LC-MS/MS assays. Both derivatization techniques represent a simple and inexpensive way for the determination of double bond positions in fatty acids with low number of double bonds. No adaptation of MS hardware is required and the specific isotopic pattern of resulting sulfur-containing products provides additional structural confirmation. This reaction scheme opens up the avenue of structural tuning of disulfide reagents beyond DMDS and DPDS using reagents like cystine and analogs to achieve enhanced performance and sensitivity.

Characterization of cooked off-flavor volatile sulfur-containing compounds in green tea and their thermal inhibition via (-)-epigallocatechin gallate.

Cooked note is an undesired flavor in green tea, while the key odorants and inhibition mechanisms were unknown. Here, volatiles of four green tea samples and two thermal reaction models of methionine-glucose and methional were assessed using gas chromatography­sulfur chemiluminescence detector and two dimensional gas chromatography-time-of-flight mass spectrometry. Nonvolatiles of reaction models were determined using ultra performance liquid chromatography-Q-Exactive orbitrap mass spectrometry. Four cooked smelling sulfur-containing odorants including dimethyl trisulfide, dimethyl sulfide, diethyl disulfide, and methanethiol having odor activity values > 1 were characterized in tea samples. Aroma addition tests confirmed dimethyl trisulfide (> 0.4 µg/L) as a reliable predictor of the cooked note. Seven sulfur-containing odorants were detected in reaction models. The addition of (-)-epigallocatechin gallate depleted glucose and interrupted the reaction, thus reduced sulfur-containing odorants' amounts. The study provides a novel insight on targeted strategic guidance for mitigating cooked off-flavor during the thermal processing of green tea production.

Co-regulating the pore structure and surface chemistry of sludge-based biochar for high-performance deodorization of gaseous dimethyl disulfide.

A straightforward and eco-friendly preparation method for porous sludge biochar (SBA-3) was developed to deodorize gaseous dimethyl disulfide (DMDS) using ion exchange to adjust micropore structures coupled with carboxyl functionalization. Compared with the unmodified sludge biochar SBA-1 and SBA-2 treated with ion exchange, the pore size of SBA-3 decreased accompanied with increasing specific surface area and micropore volume. The Brunauer-Emmett-Teller (BET) specific surface area and micropore volume were 176.35 m2 g-1 and 0.0314 cm³ g-1, which were 2.02 and 1.71-fold larger than those of SBA-2, as well as 20.60 and 78.5-fold larger than those of SBA-1, respectively. Meanwhile, the amount of -COOH on the surface of SBA-3 increased from 0.425 to 1.123 mmol g-1, which was 2.64-fold larger than that of SBA-1. The adsorption behavior between DMDS and SBA-3 could be well described by the quasi-second-order kinetic model and Langmuir isotherm model. The maximum monolayer adsorption capacity was 35.12 mg g-1 at 303 K. Thermodynamic and DFT calculations indicated that the adsorption of DMDS on SBA-3 was exothermic with the deodorization mechanisms involving pore filling and chemisorption.

Unraveling redox pathways of the disulfide bond in dimethyl disulfide: Ab initio modeling.

CONTEXT: In cellular environments, the reduction of disulfide bonds is pivotal for protein folding and synthesis. However, the intricate enzymatic mechanisms governing this process remain poorly understood. This study addresses this gap by investigating a disulfide bridge reduction reaction, serving as a model for comprehending electron and proton transfer in biological systems. Six potential mechanisms for reducing the dimethyl disulfide (DMDS) bridge through electron and proton capture were explored. Thermodynamic and kinetic analyses elucidated the sequence of proton and electron addition. MD-PMM, a method that combines molecular dynamics simulations and quantum-chemical calculations, was employed to compute the redox potential of the mechanism. This research provides valuable insights into the mechanisms and redox potentials involved in disulfide bridge reduction within proteins, offering an understanding of phenomena that are challenging to explore experimentally. METHODS: All calculations used the Gaussian 09 software package at the MP2/6-311 + g(d,p) theory level. Visualization of the molecular orbitals and electron densities was conducted using Gaussview6. Molecular dynamics simulations were performed using GROMACS with the CHARMM36 force field. The PyMM program (Python Program for QM/MM Simulations Based on the Perturbed Matrix Method) is used to apply the Perturbed Matrix Method to MD simulations.

Floral scent of eastern skunk cabbage (Symplocarpus foetidus: Araceae).

Symplocarpus foetidus (L.) Salisb. (eastern skunk cabbage) occurs across a broad geographic range of northeastern North America, blooming in winter between December and March. The inflorescences are well-known for their thermogenic and thermoregulatory metabolic capabilities. The perceptual qualities of their fetid floral aroma have been described widely in the literature, but to date the floral volatile composition remained largely unknown. Here we present a detailed study of the floral scent produced by S. foetidus collected from intact female- and male-stage inflorescences and from dissected floral parts. Our results show a large range of biosynthetically diverse volatiles including nitrogen- and sulfur-containing compounds, monoterpenes, benzenoids, and aliphatic esters and alcohols. We document high inter-individual variation with some organ-specific volatile trends but no clear strong variation based on sexual stage. Multivariate data analysis revealed two distinct chemotypes from our study populations that are not defined by sexual stage or population origin. The chemotype differences may explain the bimodal perceptual descriptions in earlier work which vary between highly unpleasant/fetid and pleasant/apple-like. We discuss the results in ecological contexts including potential for floral mimicry, taking into account existing pollination studies for the species. We also discuss the results in evolutionary contexts, comparing our scent data to published scent data from the close sister species Symplocarpus renifolius. Future work should more closely examine the chemotype occurrence and frequency within these and other populations, and the impact these chemotypes may have on pollinator attraction and reproductive success.

Delafossite CuGaO2-Based Chemiresistive Sensor for Sensitive and Selective Detection of Dimethyl Disulfide.

Dimethyl disulfide (DMDS) is a common odor pollutant with an extremely low olfactory threshold. Highly sensitive and selective detection of DMDS in ambient humid air background, by metal oxide semiconductor (MOS) sensors, is highly desirable to address the increased public concern for health risk. However, it has still been a critical challenge up to now. Herein, p-type delafossite CuGaO2 has been proposed as a promising DMDS sensing material owing to its striking hydrophobicity (revealed by water contact angle measurement) and excellent partial catalytic oxidation properties (indicated by mass spectroscopy). The present CuGaO2 sensor shows a selective DMDS response, with satisfied humidity resistance performance and long-term stability at a relatively low operation temperature of 140 °C. An ultrahigh response of 100 to 10 ppm DMDS and a low limit of detection of 3.3 ppb could be achieved via a pulsed temperature modulation strategy. A smart sensing system based on a CuGaO2 sensor has been developed, which could precisely monitor DMDS vapor in ambient humid air, even with the presence of multiple interfering gases, demonstrating the practical application capability of MOS sensors for environmental odor monitoring.

Alleviation of banded leaf and sheath blight disease incidence in maize by bacterial volatile organic compounds and molecular docking of targeted inhibitors in Rhizoctonia solani.

Rhizoctonia solani (RS) is a pathogenic fungus that affects maize (Zea mays L.) plants and causes banded leaf and sheath blight (BLSB) with severe consequences leading to significant economic losses. Contrarily, rhizobacteria produce numerous volatile organic compounds (VOCs) that help in devising the environment-friendly mechanism for promoting plant growth and stress alleviation without having physical contact with plants. In the present study, 15 rhizobacterial strains were tested for their antagonism against RS. The antagonistic potential of VOCs of the tested plant growth-promoting rhizobacteria (PGPR) strains ranged from 50% to 80% as compared to the control (without PGPR). Among these 15 strains, the maximum (80%) antagonistic activity was exhibited by Pseudomonas pseudoalcaligenes SRM-16. Thus, the potential of VOCs produced by P. pseudoalcaligenes SRM-16 to alleviate the BLSB disease in maize was evaluated. A pot experiment was conducted under greenhouse conditions to observe the effect of VOCs on disease resistance of BLSB-infected seedlings. Overall, maize seedlings exposed to VOCs showed a significant increase in disease resistance as indicated by a reduced disease score than that of unexposed infected plants. The VOCs-exposed maize exhibited lower (11.6%) disease incidence compared to the non-inoculated maize (14.1%). Moreover, plants exposed to VOCs displayed visible improvements in biomass, photosynthetic pigments, osmoregulation, and plant antioxidant and defense enzyme activities compared to the healthy but unexposed seedlings. Simultaneous application of RS and VOCs enhanced superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), phenylalanine ammonia lyase (PAL), ascorbate peroxidase (APX), and polyphenol oxidase (PPO) activities by 96.7%, 266.6%, 313.7%, 246.6%, 307%, and 149.7%, respectively, in the roots and by 81.6%, 246.4%, 269.5%, 269.6%, 329%, and 137.6%, respectively, in the shoots, relative to those of the control plants. The binding affinity of the VOCs (2-pentylfuran, 2,3-butanediol, and dimethyl disulfide) with CRZ1 and S9 protein receptors of RS was assessed by deploying in silico methods. Overall, 2-pentylfuran exhibited a binding affinity with both the selected receptors of RS, while 2,3-butanediol and dimethyl disulfide were able to bind S9 protein only. Hence, it can be deduced that S9 protein receptors are more likely the target RS receptors of bacterial VOCs to inhibit the proliferation of RS.

Effects of soil factors on dimethyl disulfide desorption and the risk of phytotoxicity to newly-planted seedlings.

Dimethyl disulfide (DMDS) is a relatively new soil fumigant used in agro-industrial crop production to control soil-borne pests that damage crops and reduce yield. The emissions of DMDS after fumigation reduce soil concentrations thus reducing the risk of phytotoxicity to newly planted crops. However, the factors affecting the desorption of DMDS from soil are unclear. In our study, the desorption characteristics of DMDS from soil were measured in response to continuous ventilation. The degradation of DMDS in soil was examined by thermal incubation. The phytotoxic response of newly-planted cucumber (Cucumis sativus) seedlings to DMDS residues was measured by a sand culture experiment. The results showed DMDS desorption and degradation rates fit a first-order model; that 92% of the DMDS desorption occurred in the first hour after fumigant application; and that residue concentrations in the soil at the end of the ventilation period were unlikely to be phytotoxic to newly-planted cucumber seedlings. By the third day of ventilation, the average desorption rate (ADR) of DMDS in Wenshan soil was 4.0 and 3.6 times, respectively, faster than that in Shunyi and Suihua soils and the ADR of DMDS in soil decreased by 40.0% when the soil moisture content increased from 3% to 12% (wt/wt). Moreover, within one hour of ventilation, the ADR of DMDS in soil decreased by 20.1% when the soil bulk density increased from 1.1 to 1.3 g cm-3. The degradation of DMDS in soil, however, was mostly influenced by soil type and moisture content. A slow degradation rate resulted in a high initial desorption concentration of DMDS in soil. Our results indicated that DMDS desorption from soil in response to continuous ventilation was affected by the soil type, moisture content and bulk density. Rapid degradation of DMDS in soil will lower the risk of phytotoxic residues remaining in the soil and reduce emissions during the waiting period. Acceleration of emissions early in the waiting period by managing soil moisture content or increasing soil porosity may shorten the duration of emissions. Alternatively, soil extraction technology could be developed to recover and reduce fumigant emissions.

A new formulation of screwworm fly attractant with reduced hazardous chemicals and transport restrictions.

New World screwworm flies, Cochliomyia hominivorax (Coquerel), are obligate parasites of warm-blooded animals. They were eradicated from North and Central America during the mid-20th to early-21st centuries using the sterile insect technique (SIT), a method presently employed to maintain a permanent barrier between Central and South America. Lures are an important component of the screwworm eradication program, where they are used for surveillance, sample collection, and strain evaluation in the field. The first chemical lure, later named swormlure, was developed based on the attractiveness of C. hominivorax to volatile organic compounds (VOCs) produced from decomposing animal tissues. The formulation has changed little over the years and presently contains 10 chemicals, one of which is dimethyl disulfide (DMDS). Restrictions on the transport of DMDS have recently impeded its use in swormlure-4 (SL-4). However, dimethyl trisulfide (DMTS) is not as highly restricted and can be shipped via air transportation. Both chemicals are produced by microbial decomposition of animal tissues. Here, we conducted field trials using three releases of sterile C. hominivorax, each comprising approximately 93,000 flies, to test the efficacy of SL-4, containing DMDS, to swormlure-5 (SL-5) containing DMTS. Traps baited with SL-4 and SL-5 captured 575 (mean = 191.7, SD 17.9) and 665 (mean = 221.7, SD 33.2) C. hominivorax, respectively (df = 19, F = 1.294, P = 0.269). However, traps baited with SL-5 captured considerably more Cochliomyia macellaria (Fabricius), a closely related but nontarget fly.

Response Surface Methodology Approach to Evaluate the Effect of Transition Metals and Oxygen on Photo-Degradation of Methionine in a Model Wine System Containing Riboflavin.

A Box-Behnken experimental design was implemented in model wine (MW) to clarify the impact of copper, iron, and oxygen in the photo-degradation of riboflavin (RF) and methionine (Met) by means of response surface methodology (RSM). Analogous experiments were undertaken in MW containing caffeic acid or catechin. The results evidenced the impact of copper, iron, and oxygen in the photo-induced reaction between RF and Met. In particular, considering a number of volatile sulfur compounds (VSCs) that act as markers of light-struck taste (LST), both transition metals can favor VSC formation, which was shown for the first time for iron. Oxygen in combination can also affect the concentration of VSCs, and a lower content of VSCs was revealed in the presence of phenols, especially caffeic acid. The perception of "cabbage" sensory character indicative of LST can be related to the transition metals as well as to the different phenols, with potentially strong prevention by phenolic acids.

Superior dimethyl disulfide degradation in a microbial fuel cell: Extracellular electron transfer and hybrid metabolism pathways.

To enhance the biological degradation of volatile organic sulfur compounds, a microbial fuel cell (MFC) system with superior activity is developed for dimethyl disulfide (DMDS) degradation. The MFC achieves a removal efficiency near 100% within 6 h (initial concentration: 90 mg L-1) and a maximum biodegradation rate constant of 0.743 mM h-1. The DMDS removal load attains 2.684 mmol h-1 L-1, which is 6.18-2440 times the loads of conventional biodegradation processes reported. Meanwhile, the maximum power density output and corresponding current density output are 5.40 W m-3 and 40.6 A m-3, respectively. The main mechanism of extracellular electron transfer is classified as mediated electron transfer, supplemented by direct transfer. Furthermore, the mass balance analysis indicates that methanethiol, S0, S2-, SO42-, HCHO, and CO2 are the main intermediate and end products involved in the hybrid metabolism pathway of DMDS. Overall, these findings may offer basic information for bioelectrochemical degradation of DMDS and facilitate the application of MFC in waste gas treatment. ENVIRONMENTAL IMPLICATION: Dimethyl disulfide (DMDS), which features poor solubility, odorous smell, and refractory property, is a typical pollutant emitted from the petrochemical industry. For the first time, we develop an MFC system for DMDS degradation. The superior DMDS removal load per unit reactor volume is 6.18-2440 times those of conventional biodegradation processes in literature. Both the electron transfer route and the hybrid metabolism pathway of DMDS are cleared in this work. Overall, these findings give an in-depth understanding of the bioelectrochemical DMDS degradation mechanism and provide an efficient alternative for DMDS removal.

Volatile Dimethyl Disulfide from Guava Plants Regulate Developmental Performance of Asian Citrus Psyllid through Activation of Defense Responses in Neighboring Orange Plants.

Intercropping with guava (Psidium guajava L.) can assist with the management of Asian citrus psyllid (ACP, Diaphorina citri Kuwayama), the insect vector of the huanglongbing pathogen, in citrus orchards. Sulfur volatiles have a repellent activity and physiological effects, as well as being important components of guava volatiles. In this study, we tested whether the sulfur volatiles emitted by guava plants play a role in plant-plant communications and trigger anti-herbivore activities against ACP in sweet orange plants (Citrus sinensis L. Osbeck). Real-time determination using a proton-transfer-reaction mass spectrometer (PTR-MS) showed that guava plants continuously release methanethiol, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), and the contents increased rapidly after mechanical damage. The exposure of orange plants to DMDS resulted in the suppression of the developmental performance of ACP. The differential elevation of salicylic acid (SA) levels; the expression of phenylalanine ammonia lyase (PAL), salicylate-O-methyl transferase (SMT), and pathogenesis-related (PR1) genes; the activities of defense-related enzymes PAL, polyphenol oxidase (PPO), and peroxidase (POD); and the total polyphenol content were observed in DMDS-exposed orange plants. The emission of volatiles including myrcene, nonanal, decanal, and methyl salicylate (MeSA) was increased. In addition, phenylpropanoid and flavonoid biosynthesis, and aromatic amino acid (such as phenylalanine, tyrosine, and tryptophan) metabolic pathways were induced. Altogether, our results indicated that DMDS from guava plants can activate defense responses in eavesdropping orange plants and boost their herbivore resistance to ACP, which suggests the possibility of using DMDS as a novel approach for the management of ACP in citrus orchards.

Bacterial Volatiles Known to Inhibit Phytophthora infestans Are Emitted on Potato Leaves by Pseudomonas Strains.

Bacterial volatiles play important roles in mediating beneficial interactions between plants and their associated microbiota. Despite their relevance, bacterial volatiles are mostly studied under laboratory conditions, although these strongly differ from the natural environment bacteria encounter when colonizing plant roots or shoots. In this work, we ask the question whether plant-associated bacteria also emit bioactive volatiles when growing on plant leaves rather than on artificial media. Using four potato-associated Pseudomonas, we demonstrate that potato leaves offer sufficient nutrients for the four strains to grow and emit volatiles, among which 1-undecene and Sulfur compounds have previously demonstrated the ability to inhibit the development of the oomycete Phytophthora infestans, the causative agent of potato late blight. Our results bring the proof of concept that bacterial volatiles with known plant health-promoting properties can be emitted on the surface of leaves and warrant further studies to test the bacterial emission of bioactive volatiles in greenhouse and field-grown plants.

Determining the double-bond positions of monounsaturated compounds in the alcohol fraction in seep carbonate.

The unsaturation patterns of molecular fossils are critical in distinguishing their biological precursors and diagenetic processes. However, questions regarding the determination of double-bond positions of unsaturated dialkyl glycerol ethers (DAGEs) in submarine hydrocarbon seep ecosystems remain unsolved. To address this problem, a protocol for dimethyl disulfide (DMDS) derivative analysis using gas chromatography (GC)-mass spectrometry was optimised. Herein, the double-bond positions of monounsaturated short-chain alcohols, monoalkyl glycerol ethers (MAGEs), and DAGEs in seep carbonates were analysed. Among these compounds, the double-bond positions of trimethylsilyl (TMS) derivatives of the monounsaturated DAGE-DMDS adducts were determined for the first time, with mass spectra characterized by molecular ions (M+·) and two major diagnostic ions (ω+ and Δ+) cleaved at the double bonds. For both the MAGEs and DAGEs, the double-bond positions of the monounsaturated n-C16:1-alkyl moieties were identified at ω5 and ω7. Compared to monounsaturated short-chain alcohols and MAGEs, both ionization efficiency and relative sensitivity for the TMS derivatives of DAGE-DMDS adducts were low as indicated by the high limit of detection at a signal-to-noise ratio of 3. In addition, the appropriate injection parameters and oven temperature program during GC analyses may be crucial in determining the double-bond positions within monounsaturated DAGEs.

A dimethyl disulfide gas sensor based on nanosized Pt-loaded tetrakaidecahedralα-Fe2O3nanocrystals.

Surface modification by employing precious metals is one of the most effective ways to improve the gas-sensing performance of metal oxide semiconductors. Pureα-Fe2O3nanoparticles and Pt-modifiedα-Fe2O3nanoparticles were prepared sequentially using a rather simple hydrothermal synthesis and impregnation method. Compared with the originalα-Fe2O3nanomaterials, the Pt-α-Fe2O3nanocomposite sensor shows a higher response value (Ra/Rg = 58.6) and a shorter response/recovery time (1 s/168 s) to 100 ppm dimethyl disulfide (DMDS) gas at 375 °C. In addition, it has better selectivity to DMDS gas with the value of more than 9 times higher than the other target gases at 375 °C. This study indicates that the Pt-α-Fe2O3nanoparticle sensor has good prospects and can be used as a low-cost and effective DMDS gas sensor.

Soil properties affect vapor-phase adsorption to regulate dimethyl disulfide diffusion in soil.

Dimethyl disulfide (DMDS) is efficacious against nematodes and other soil-borne pathogens known to reduce crop quality and yield. Previous studies reported inconsistent efficacy and suggested that the diffusion of DMDS varied with different soil types. The effect of soil adsorption on gaseous DMDS diffusion through different soil types is poorly understood. To clarify the role and mechanism of soil adsorption in the diffusion of gaseous DMDS in soil, we have studied the diffusion rate constant (Rt) of gaseous DMDS in soils using a soil column experiment. The adsorption of DMDS at each gas-soil, soil-water and gas-water partition was measured by a batch-equilibrium headspace method. The results showed the DMDS adsorption equilibrium was well-described by the nonlinear Freundlich isotherm and the linear Henry isotherm. Rt values were strongly negatively correlated with the Henry coefficient (Kd) values. The Kd values of dry soil were several orders of magnitude higher than those observed in moist soil within each moisture content range. The Kd values in dry soil were strongly positively correlated with soil pore size (<2 nm). However, when the soil moisture content ranged from 3 to 12% (w/w), the Kd values were strongly correlated with specific surface area (SSA). Elevated temperatures promoted the gaseous phase of DMDS (consistent with Henry's Law) and its diffusion through soil. The soil-water partition coefficient (K'f) ranged from 1.83 to 2.20 µg11/n mL1/n g-1 in tested soils. Our results suggest that the DMDS vapor-phase diffusion in soil was significantly affected by soil adsorption, which in turn depended on the soil's properties especially the SSA and soil moisture content. These findings suggest applicators can reduce the risk of unsatisfactory and inconsistent efficacy results against soil-borne pests by adjusting the DMDS dose and fumigation period according to soil type, moisture conditions, and other environmental factors.

Dual activity of Serratia marcescens Pt-3 in phosphate-solubilizing and production of antifungal volatiles.

BACKGROUND: Soil fertility decline and pathogen infection are severe issues for crop production all over the world. Microbes as inherent factors in soil were effective in alleviating fertility decrease, promoting plant growth and controlling plant pathogens et al. Thus, screening microbes with fertility improving and pathogen controlling properties is of great importance to humans. RESULTS: Bacteria Pt-3 isolated from tea rhizosphere showed multiple functions in solubilizing insoluble phosphate, promoting plant growth, producing abundant volatile organic compounds (VOCs) and inhibiting the growth of important fungal pathogens in vitro. According to the 16S rRNA phylogenetic and biochemical analysis, Pt-3 was identified to be Serratia marcescens. The solubilizing zone of Pt-3 in the medium of lecithin and Ca3(PO4)2 was 2.1 cm and 1.8 cm respectively. In liquid medium and soil, the concentration of soluble phosphorus reached 343.9 mg.L- 1, and 3.98 mg.kg- 1, and significantly promoted the growth of maize seedling, respectively. Moreover, Pt-3 produced abundant volatiles and greatly inhibited the growth of seven important phytopathogens. The inhibition rate ranged from 75.51 to 100% respectively. Solid phase micro-extraction coupled with gas chromatography tandem mass spectrometry proved that the antifungal volatile was dimethyl disulfide. Dimethyl disulfide can inhibit the germination of Aspergillus flavus, and severely destroy the cell structures under scanning electron microscopy. CONCLUSIONS: S. marcescens Pt-3 with multiple functions will provide novel agent for the production of bioactive fertilizer with P-solubilizing and fungal pathogens control activity.

Non-volatile and volatile metabolic profiling of tomato juice processed by high-hydrostatic-pressure and high-temperature short-time.

High hydrostatic pressure (HHP) processing has become a commercial success in fruit and vegetable processing. Herein, the effects of HHP and high-temperature short-time (HTST) processing on metabolic profiling in tomato juice was evaluated by UPLC-MS/MS, HPLC, and GC-MS; a total of 425 metabolites, 14 carotenoids, and 56 volatile compounds were identified in tomato juice. HHP processing affects the composition of the juice less than HTST processing, considering 4 and 33 differential metabolites discriminated after HHP and HTST processing, respectively. The total lycopene and carotenoid contents in tomato juice increased after HHP processing, while the ß-carotene and lycopene contents decreased after HTST processing. Further, more volatile compounds and higher contents of aldehydes that contribute to green aroma and lower contents of alcohols were observed after HHP and HTST processing, respectively. These findings provide a comprehensive understanding of the advantages of HHP processing on metabolite profiles in tomato juice.

Effect of glucose oxidase treatment on the aroma qualities and release of cooked off-odor components from heat-treated Hami melon juice.

Melon juice produces strong cooked off-odors during heat processing, leading to serious deterioration of aroma quality. In this work, the aroma quality of melon juice, the changes in GOD reaction products, and the interactions of reaction products and cooked off-odor components were analyzed by sensory evaluation, gas chromatography-mass spectrometry/olfactory, ultraperformance liquid chromatography-triple quadrupole mass spectrometry, and isothermal titration calorimetry to study the effect mechanism of glucose oxidase (GOD) on the release of cooked off-odor components from heat-treated melon juice. The results showed that GOD treatment improved the aroma quality mainly by controlling off-odor attributes and maintaining characteristic odor attributes. This was because the reaction products (hydrogen peroxide and gluconic acid) of GOD treatment inhibited the release of cooked off-odor components from heat-treated melon juice through oxidation and hydrophobic effects. Furthermore, these products reduced the loss of characteristic odor compounds by restraining Maillard, degradation, and oxidation reactions during heat processing.

Adsorption of dimethyl disulfide onto activated carbon cloth.

Dimethyl disulfide (DMDS) has a specific unpleasant odour and is profoundly toxic with an odour threshold of around 7-12 ppb. In this study, the removal of DMDS was investigated by adsorption on activated carbon cloth (ACC) in the gas phase. Kinetics and isotherm studies were performed. Adsorption kinetics followed by GC-MS and the data were processed using different models. When correlation coefficients (R2) of linear regression analysis are analyzed, it is seen that the concordance of experimental data to the pseudo-second-order equation is quite good. Isotherm data have been examined using Freundlich, Temkin and Langmuir models. The regression coefficient (R2) of data to fit the Langmuir model is 0.9993, which means that the fit is very good. The monolayer adsorption capacity (qm) of DMDS has been calculated as 118 mL.g-1 according to the Langmuir model.