Oxidation Of Unsaturated Fatty Acids Research Articles

Volatile Compounds in Pulses: A Review.

The worldwide demand for pulse-based products is increasing in the face of climate change, but their acceptability is limited due to the presence of off-flavours. Off-notes contribute to negative perceptions of pulses (beany notes). Volatile compounds belong to a large variety of chemical classes. They are mainly produced from the oxidation of unsaturated free fatty acids and the degradation of amino acids during seed development, storage, and transformation (dehulling, milling, and starch or protein production). This review aims to provide an overview highlighting the identification of these molecules in different pulses, their potential origins, and their impact on perceptions. However, data on odour-active compounds in pulses are sparse, as they are limited to those of two studies on peas and lupins. A better knowledge of the volatile compounds involved in the off-notes and their origins should allow for drawing efficient strategies to limit their impact on overall perception for more acceptable healthy food design.

Role of lipid deterioration on the quality of aquatic products during low‐temperature storage: a lipidomics‐based study using large yellow croaker (Larimichthys crocea)

AbstractThis work investigated the effects of different storage periods (0 day, 90 days, 120 days) on the quality of large yellow croaker oil. The lipomics of large yellow croaker oil was quantitatively detected by GC‐MS, the content of triglyceride in large yellow croaker oil reached 52.56% at 0 day. With the extension of storage time, the content of large yellow croaker oil components decreased gradually. Differential lipid histogram clearly indicates that the extension of the storage period will affect the change of fish oil, due to the rise in the temperature of large yellow croaker oil; the color of the hot map is bright from the dark. Additionally, the fatty acid composition and volatile components were measured. At 120 days, the decomposition rate of lipid molecular in large yellow croaker oil is increased by oxidation of unsaturated fatty acids, and its oxidised metabolite produced small substance such as aldehydes, ketones, alcohols, and acids. During storage, the waxy, fat, and floral flavour in the oil aroma of large yellow croaker oil decreased gradually, while the yeast flavour and oil flavour increased gradually. These results provide insights for the study of lipid transformation and quality of large yellow croaker oil during different storage.

Development, validation, and application of an HPLC-MS/MS method for quantification of oxidized fatty acids in plants

Oxylipins constitute a huge class of compounds produced by oxidation of long-chain unsaturated fatty acids either chemically (by radicals such as reactive oxygen species, ROS) or enzymatically (by lipoxygenases, LOX; cyclooxygenases, COX; or cytochrome P450 pathways). This process generates fatty acids peroxides, which can then be further modified in a broad range to epoxy, hydroxy, keto, ether fatty acids, and also hydrolyzed to generate small aldehydes and alcohols. In general, oxylipins are present in almost all living organisms and have a wide range of signaling, metabolic, physiological, and ecological roles depending on the particular organism and on their structure. In plants, oxylipins have been extensively studied over the past 35 years. However, these studies have focused mainly on the jasmonates and so-called green leaves volatiles. The function of early LOX products (like keto and hydroxy fatty acids) is yet not well understood in plants, where they are mainly analyzed by indirect methods or by GC–MS what requires a laborious sample preparation. Here, we developed and validated a straightforward, precise, accurate, and sensitive method for quantifying oxylipins in plant tissues using HPLC-MS/MS, with a one-step extraction procedure using low amount of plant tissues. We successfully applied this method to quantify the oxylipins in different plant species and Arabidopsis thaliana plants treated with various biotic and abiotic stress conditions.

Effects of three different gas environments on the storage stability of Lactobacillus plantarum LIP-1 at room temperature

We studied the effects of different gas environments on the storage stability of Lactobacillus plantarum LIP-1 at room temperature, and evaluated the permeability, integrity and fatty acids of cell membrane. The results showed that after 60 days of storage, the survival rate of nitrogen group was the highest, the permeability change of cell membrane was the smallest, and the integrity of cell membrane was the largest. Compared with the air group, the ratio of unsaturated fatty acids to saturated fatty acids in vacuum group and nitrogen group changed little (P < 0.05). The results showed that the survival rate of the strain was closely related to the damage of cell membrane; the oxidation of unsaturated fatty acids was the main reason for the destruction of cell membrane structure; different gas environment affected the oxidation degree of cell membrane fatty acid, which led to different storage stability.

INVESTIGATION OF THE INFLUENCE OF ASCORBIC ACID ON THE TITER OF LACTIC ACID BACTERIA AND TEST FERMENTATION

The use of modern biotechnological approaches in the field of baking allows to improve the quality of finished products, reduce the duration of the technological cycle and increase the functional properties of bread. The aim of the study was to study the effect of ascorbic acid on the intensity of fermentation processes during dough maturation. The task of the work is to establish the optimal amount of improver — ascorbic acid, taking into account organoleptic, microbiological and structural-mechanical quality indicators. The intensity of microbiological and biochemical processes during dough maturation (fermentation) directly depends on the concentration of hydrogen ions compared to the total content of acid-reactive products, as well as redox potential, titrated acidity and titer of fermentation microflora.The introduction of ascorbic acid in the amount of 0.1—0.12 g/kg of flour, the fermentation time of the dough was reduced from 270 to 225 minutes, the speed and completeness of redox reactions (redox potential -50 mV) were increased. redox potential reactions catalyzed by the enzymes peroxidases and catalases are associated with the oxidation of unsaturated fatty acids, which promote the action of lipoxygenase by disrupting its inhibitor - hydrogen peroxide. Experiments have confirmed the activation of the fermenting microflora of the dough and the increase of its titer. Indicators of active (pH 4.66—4.51) and titrated acidity (6.0—6.5 degrees Turner) are within the limits that fully meet the optimal conditions for the cultivation of lactic acid bacteria, which indicates the correct selection of the amount of ascorbic acid and the composition of the nutritious flour mixture.

The use of lemon juice and its role on polyunsaturated fatty acids and cholesterol oxides formation in thermally prepared sardines

Lemon juice is used to enhance the flavor of dishes prepared with fish, which is more prone to oxidation than other flesh food. This study evaluated the impact of treating sardine fillets (Sardina pilchardus) with Tahiti lemon juice and submit them to different domestic cooking methods (air fryer, grill, and deep-fat fryer), regarding the oxidation of unsaturated fatty acids and cholesterol. The juice extract was characterized by its antioxidant capacity and bioactive constituents by UHPLC-MS. Cooking caused the degradation of polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic (EPA, C20:5) and docosahexaenoic acids (DHA, C22:6), and increased the cholesterol oxides level. However, for most treatments, degradation of PUFAs and formation of cholesterol oxides were more pronounced in samples treated with juice. Lemon juice induced cholesterol oxidation, mainly in air-fried sardines where the total content of cholesterol oxides increased from 700 ± 4 (control) to 1333 ± 5 μg/g (10 % lemon juice, in dry basis). Thus, the overall data suggest that potential antioxidant compounds may have degraded during heating and the acid environment may have induced oxidative reactions.

Disaccahrides-Based Cryo-Formulant Effect on Modulating Phospho/Mitochondrial Lipids and Biological Profiles of Human Leukaemia Cells.

The use of novel cryo-additive agents to increase cell viability post-cryopreservation is paramount to improve future cell based-therapy treatments. We aimed to establish the Human Leukemia (HL-60) cells lipidomic and biological patterns when cryo-preserved in DMSO alone and with 300 µM Nigerose (Nig), 200 µM Salidroside (Sal) or a combination of Nig (150 µM) and Sal (100 µM). HL-60 cells were pre-incubated with Nig/Sal prior, during and post cryopreservation, and subjected to global lipidomic analysis. Malondialdeyhde (MDA), released lactate dehydrogenase (LDH) and reactive oxygen scavenger (ROS) measurements were also carried out to evaluate levels of lipid peroxidation and cytotoxicity. Cryopreserving HL-60 cells in DMSO with Nig and Sal provided optimal protection against unsaturated fatty acid oxidation. Post-thaw, cellular phospholipids and mitochondrial cardiolipins were increased by Nig/Sal as the ratio of unsaturated to saturated fatty acids 2.08 +/- 0.03 and 0.95 +/- 0.09 folds respectively in comparison to cells cryopreserved in DMSO alone (0.49 +/- 0.05 and 0.86 +/- 0.10 folds). HL-60 lipid peroxidation levels in the presence of DMSO + Nig and Sal combined were significantly reduced relative to pre-cryopreservation levels (10.91 +/- 2.13 nmole) compared to DMSO (17.1 +/- 3.96 nmole). DMSO + Nig/Sal combined also significantly reduced cell cytotoxicity post-thaw (0.0128 +/- 0.00182 mU/mL) in comparison to DMSO (0.0164 +/- 0.00126 mU/mL). The combination of Nig/Sal also reduced significantly ROS levels to the levels of prior cryopreservation of HL-60. Overall, the establishment of the cryopreserved HL-60 cells lipidomic and the corresponding biological profiles showed an improved cryo-formulation in the presence of DMSO with the Nig/Sal combination by protecting the, mitochondrial inner membrane, unsaturated fatty acid components (i. e. Cardiolipins) and total phospholipids.

Secondary organic aerosol markers and related polar organic compounds in summer aerosols from a sub-urban site in Athens: Size distributions, diurnal trends and source apportionment

Size-segregated aerosols (six stages with a diameter from <0.49 to >7.2 μm) were collected during daytime and nighttime in the summer of 2020 and were analyzed for dicarboxylic acids, isoprene, α/β-pinene and β-caryophyllene secondary organic aerosol (SOA) tracers, aromatic acids, hydroxy-polyacids, monocarboxylic acids and levoglucosan. The vast majority of the detected compounds presented significantly higher (p < 0.05) concentrations in fine than in coarse modes, excluding benzoic and oleic acids for which the higher fine mode than coarse mode concentrations were not significant and pinonic acid which was found at higher coarse mode concentrations. The dominant compound in the fine mode was 2-methylerythritol (mean of 213 ± 79.4 ng m−3), whereas in coarse particles palmitic acid was the most abundant (mean of 22.8 ± 9.7 ng m−3). All of the detected compounds, except for terephthalic acid, presented higher daytime concentrations, a difference that in the cases of glutaric, suberic, azelaic and pinic acids was significant (p < 0.05). The six-stage size distribution showed various patterns, with most species peaking at particles with a diameter of <1.1 μm suggesting photoxidation sources, while significant peaks at the size of 3–7.2 μm have been observed for suberic, azelaic, pinonic, benzoic, trimellitic and monocarboxylic acids. The hydroscopic growth of particles during nighttime may explain the observed decrease of the fine to coarse concentration ratio. From the employed source apportionment tools four factors where derived explaining 83.0% of total the variance including oxidation of anthropogenic volatile organic compounds (35.6%), oxidation of monoterpenes and sesquiterpenes (21.5%), isoprene's oxidation (14.1%) and photoxidation of unsaturated fatty acids (11.8%).

Effects of biodiesel on changes in IC engine performances: A long-term experiment with farm tractors

This study aimed to determine the effects of continued use of petroleum diesel and biodiesel fuel blend on the changes in engine performances and exhaust gas emissions of the IC engine. The experiments were conducted on a tractor engine using a blend of biodiesel and petroleum diesel in the ratio of 40:60% (v.v−1) (BD40). The tractor performed standard farming operations using BD40 fuel for 1000 h. The engine performances and exhaust gas emissions were evaluated at the beginning of the experiment and after 100, 250, 500, and 1000 h.Maximum engine power dropped by 6.16% after 1000 h with BD40 fuel, and specific fuel consumption and CO emission increased by 7.35 and 12.5% respectively. The CO2 emission was reduced by 6.26%. Worsened engine performance was probably a consequence of the deposit on the tip of injectors which was formed due to thermal oxidation of unsaturated fatty acids that amounted to over 90% in the used raw material for biodiesel production. Statistical analysis of the obtained data indicated statistically significant changes.

Antioxidative Properties and Chemical Changes of Quercetin in Fish Oil: Quercetin Reacts with Free Fatty Acids to Form Its Ester Derivatives.

In this research, we studied the antioxidative properties and chemical changes of quercetin in fish oil during accelerated storage at 60 °C for 5 days. Gas chromatography (GC) analysis showed that quercetin inhibited aldehyde formation and unsaturated fatty acid oxidation in fish oil significantly; however, the inhibitory effects decreased gradually with prolonged heating time. Moreover, quercetin was consumed with increasing heating time. Some new phenolic derivatives were discovered in the fish oil with quercetin, with their structures fully elucidated by LC-MS/MS and comparison with newly synthesized ones (characterized by MS and NMR spectroscopy). Based on their chemical structures, we proposed that quercetin reacted with EPA and DHA to form the corresponding quercetin fatty acid esters in fish oil. In addition, the newly formed quercetin-3-O-eicosapentaenoate and quercetin-3-O-docosahexaenoate showed weaker DPPH and ABTS radical cation scavenging activity but much improved lipophilicity, higher cell membrane affinity, and hence enhanced cellular antioxidant activity compared with the parent quercetin. Overall, quercetin could be used as a safe dietary polyphenol to inhibit lipid oxidation. The newly formed quercetin-polyunsaturated fatty acid esters may render improved bioactivity to humans, which needs further investigation.

Interaction of Agaric Acid with the Adenine Nucleotide Translocase Induces Mitochondrial Oxidative Stress.

Mitochondrial permeability transition is characterized by the opening of a transmembranal pore that switches membrane permeability from specific to nonspecific. This structure allows the free traffic of ions, metabolites, and water across the mitochondrial inner membrane. The opening of the permeability transition pore is triggered by oxidative stress along with calcium overload. In this work, we explored if oxidative stress is a consequence, rather than an effector of the pore opening, by evaluating the interaction of agaric acid with the adenine nucleotide translocase, a structural component of the permeability transition pore. We found that agaric acid induces transition pore opening, increases the generation of oxygen-derived reactive species, augments the oxidation of unsaturated fatty acids in the membrane, and promotes the detachment of cytochrome c from the inner membrane. The effect of agaric acid was inhibited by the antioxidant tamoxifen in association with decreased binding of the thiol reagent eosin-3 maleimide to the adenine nucleotide translocase. We conclude that agaric acid promotes the opening of the pore, increasing ROS production that exerts oxidative modification of critical thiols in the adenine nucleotide translocase.

Quality of Virgin Coconut Oil with Addition of Peppermint Oil

Virgin coconut oil (VCO) is a pure coconut oil made from mature and fresh coconut meat. VCO is consumed for health-related reasons, but the unsaturated fatty acids of VCO are prone to oxidation. Mixing VCO with peppermint oil, which contains antioxidants, inhibits the oxidation of unsaturated fatty acids and thus prevents the rancidity of VCO. This research used the antioxidants from peppermint oil to improve VCO quality. VCO contains antioxidants, such as α-pinene, menthol, 1,8-cineol, camphor, flavonoid, borneol, tocopherol, and carotene. The treatments consisted of three peppermint oil concentrations (2.5%, 5%, and 7.5%) in VCO. Results showed that the additionof peppermint oil significantly improved VCO quality. The optimal concentration of peppermint oil in VCO was 7.5% with a water content of 0.05%, a free fatty acid value of 0.13%, a peroxide value of 0.53 mg eq/kg, an iodine value of 4.42 g I2/100 g, a total plate count of 0 cfu/mL, and antioxidant activity of 90.28%.

Coconut oil as a calibration matrix for headspace gas chromatographic determination of hexanal in edible oils

Oxidation of unsaturated fatty acids of edible oils results in off-flavours, in a decrease in the nutritional properties and in the formation of toxic compounds. Hexanal is a suitable marker of the oxidation process. A new solvent, coconut oil, was suggested for hexanal quantification by static headspace extraction-gas chromatography. Sample equilibration temperature, time, weight and injection time were determined to provide the highest extraction to the headspace efficiency. At the optimized extraction conditions, the hexanal detection limit was 30 µg kg–1, linearity was 0.9977 for a concentration range of 50 µg kg–1 – 2 g kg–1 and repeatability of the results was 1.1%. The effect of heating on hexanal formation in four edible oils (olive oil, sunflower oil, rapeseed oil and linseed oil) was investigated. The biggest quantity of hexanal was observed in sunflower oil and it significantly increased after heating. Rapeseed oil was the most resistant to the oxidation at elevated temperatures. For linseed oil hexanal is not the most relevant oxidation marker as hexanal is not the main volatile oxidation product.

Effects of superheated steam processing on common buckwheat grains: Lipase inactivation and its association with lipidomics profile during storage

Superheated steam (SS) at 170 °C for 5 min was used to inactivate lipase of common buckwheat grains in this study, which effectively retarded lipid hydrolytic rancidity and maintained lipid nutrition of common buckwheat. Higher stabilities based on lower free fatty acid accumulation and lipase activity were observed in SS-treated buckwheat samples during storage. Meanwhile, SS could suppress oxidation of unsaturated fatty acids (UFA) in buckwheat, significantly retard the increase of saturated fatty acids and the decrease of polyunsaturated fatty acids during storage. Moreover, the lipidomics profile results indicated that SS processing could retard the increased hydrolysis and oxidation of sulfoquinovosyl diacylglycerol, phosphatidylethanolamine, phosphatidylserine and lysophosphatidic acid during storage, while regulate the content of galactolipids. Thus, SS processing could effectively inactivate lipase, suppress UFA oxidation, change glycerolipids and glycerophospholipids subclass metabolism, and consequently retard hydrolytic rancidity and the loss of lipid nutrition in buckwheat during storage. SS processing was proved to effectively protect the quality of buckwheat during storage for the first time.

Short communication: Effect of purple corn pigment on change of anthocyanin composition and unsaturated fatty acids during milk storage

Unsaturated fatty acids (UFA) in milk give rise to radicals and lead to lipid oxidation during storage, reducing the commercial value of milk. The objective of this study was to observe the effect of anthocyanins from purple corn pigment on the oxidation of UFA in milk. Milk samples were randomly divided into 2 groups: (1) the control (without purple corn pigment) and (2) treatment (0.3% purple corn pigment), using a completely randomized design. The milk samples were placed into plastic tubes and stored at 4°C for a period of 0, 1, 3, and 7 d. Individual anthocyanin composition and UFA were detected by HPLC-mass spectrometry and gas chromatography-mass spectrometry, respectively. The results indicated that pelargonidin (0.258 vs. 0.054 µg/mL), cyanidin (5.550 vs. 1.808 µg/mL), petunidin (0.464 vs. 0.107 µg/mL), delphinidin (2.061 vs. 0.123 µg/mL), and total anthocyanin (8.332 vs. 2.091 µg/mL) significantly decreased in response to increasing storage day. Of interest, purple corn pigment had a significant effect on most of the UFA (C14:1n-5, C16:1n-7, C18:1n-9, C18:2n-6, C18:3n-3, C18:3n-6, C20:2n-6, C20:3n-3, and C20:4n-6), except for C17:1n-7 and C20:3n-6. Specifically, various stronger positive correlations were noted for anthocyanin composition and UFA (pelargonidin and petunidin with C14:1n-5, C17:1n-7, C18:2n-6, C20:2n-6, C20:3n-3, and C20:4n-6; and cyanidin and total anthocyanins with C14:1n-5, C16:1n-7, C17:1n-7). Collectively, the current study suggested that the addition of anthocyanins from purple corn pigment had the potential to maintain UFA concentrations in milk during the storage period.

Primary and secondary organic aerosol in an urban/industrial site: Sources, health implications and the role of plastic enriched waste burning

PM10 samples were collected from an urban/industrial site nearby Athens, where uncontrolled burning activities occur. PAHs, monocarboxylic, dicarboxylic, hydroxycarboxylic and aromatic acids, tracers from BVOC oxidation, biomass burning tracers and bisphenol A were determined. PAH, monocarboxylic acids, biomass burning tracers and bisphenol A were increased during autumn/winter, while BSOA tracers, dicarboxylic- and hydroxycarboxylic acids during summer. Regarding aromatic acids, different sources and formation mechanisms were indicated as benzoic, phthalic and trimellitic acids were peaked during summer whereas p-toluic, isophthalic and terephthalic were more abundant during autumn/winter. The Benzo[a]pyrene-equivalent carcinogenic power, carcinogenic and mutagenic activities were calculated showing significant (p < 0.05) increases during the colder months. Palmitic, succinic and malic acids were the most abundant monocarboxylic, dicarboxylic and hydrocarboxylic acids during the entire sampling period. Isoprene oxidation was the most significant contributor to BSOA as the isoprene-SOA compounds were two times more abundant than the pinene-SOA (13.4 ± 12.3 and 6.1 ± 2.9 ng/m3, respectively). Ozone has significant impact on the formation of many studied compounds showing significant correlations with: isoprene-SOA (r = 0.77), hydrocarboxylic acids (r = 0.69), pinene-SOA (r = 0.63),dicarboxylic acids (r = 0.58), and the sum of phthalic, benzoic and trimellitic acids (r = 0.44). PCA demonstrated five factors that could explain sources including plastic enriched waste burning (30.8%), oxidation of unsaturated fatty acids (23.0%), vehicle missions and cooking (9.2%), biomass burning (7.7%) and oxidation of VOCs (5.8%). The results highlight the significant contribution of plastic waste uncontrolled burning to the overall air quality degradation.

STUDY OF THE OXIDATIVE STABILITY OF SEVERAL TYPES OF VEGETABLE OILS WITH DIFFERENT TECHNOLOGICAL PARAMETERS

Vegetable oils are currently not only one of the most popular foods in the world, having a reputation for being healthy, but also the main source of unsaturated fatty acids, which prevent numerous cardiovascular and other diseases. In order to study the depth of oxidative changes in the chemical composition of the fatty acid phase in real technological processing processes and the preparation of culinary dishes using vegetable oils, the peroxide, acid, anisidine, Totox, thiobarbituric numbers for vegetable oil were studied under various conditions of model conditions: cooking (temperature 95-100 °C, processing time 30 min), frying (temperature 195-200 °C, processing time 15 min), short-term heating (microwave heating power 90 W, processing time 2 min), breaking the condition ovy storage (temperature 35-40 °C, and treatment time 3 to 7 days). With a comparative description of oxidative processes in coconut, palm, and sunflower oil, it was established that sunflower oil is prone to deep oxidative damage processes. A high propensity to increase the studied parameters was found for all treatment options, which indicates a deep occurrence of oxidative processes in vegetable oils. A particularly large effect, accelerating the oxidation of unsaturated fatty acids of sunflower oil, is observed in the case of storage at elevated temperatures and microwave heating. Based on these data, recommendations are made on the need to use natural antioxidants in the processing of vegetable oils, food production using vegetable oils, cooking culinary dishes, in the formulation of which vegetable oils are present.

Polar organic compounds in PM10 and PM2.5 atmospheric aerosols from a background Eastern Mediterranean site during the winter period: Secondary formation, distribution and source apportionment

Atmospheric particle samples with aerodynamic diameter <10 μm (PM₁₀) and <2.5 μm (PM₂.₅) were analyzed for elemental (EC), organic (OC) carbon and polar organic compounds. Samples were collected, on a daily basis, over 44 days during the winter period in Agia Maria Xyliatou, a background location of Cyprus. Polar organic compounds were determined using a 3-step derivatization method prior to analysis with GC/MS. Gas phase compounds and meteorological data were also measured. Secondary OC was estimated and found to be significantly higher in PM₂.₅ than PM₁₀ fraction (mean of 0.81 ± 0.58 over 0.51 ± 0.66 μg m⁻³). Concentrations of biogenic secondary formation tracers, monocarboxylic acids, dicarboxylic acids and aromatic acids ranged from 7.3 to 29.0, 2.9–162, 7.6–82.0 and 1.9–19.6 ng m⁻³ respectively, in all aerosol samples, accumulated mostly on PM₂.₅ fraction. Molecular diagnostic ratios of selected carboxylic acids indicated influence of biogenic sources and aged aerosols. Source apportionment tools employed, including principal component analysis, demonstrated anthropogenic activity, biomass burning, biogenic volatile organic compounds oxidation and oxidation of unsaturated fatty acids as the basic sources of the studied analytes. Estimation of OC contribution from different sources was performed using tracer-based methods, such as “SOA tracer method” presenting biomass burning as a significant contributor (12.8 ± 14.8% in PM₂.₅ and 5.8 ± 4.8% in PM₁₀). Oxidation of biogenic volatile organic compounds accounted for 13.0 ± 8.9% and 5.6 ± 3.5% of OC in PM₂.₅ and PM₁₀ samples respectively. Dust episodes that occurred during the sampling period, appear to enhance secondary formation mostly on PM₁₀ particles.

Fingerprinting of volatile organic compounds for quick assessment of vigour status of seeds

AbstractSeed is a fertilized mature ovule, which possesses an embryonic plant. When the dry, mature seeds are subjected to imbibition, they release a wide range of organic substances, which include low molecular weight carbonyl compounds (gases and volatiles) and water-soluble organic substances (enzymes and polysaccharides). The volatile organic compounds (VOCs) are molecules of low molecular weight (300 g mol−1) and high vapour pressure (0.01 kPa at 20°C) and include diverse chemical compounds. The nature and emission kinetics of volatiles produced from seeds vary, depending on the moisture content of the seeds. Orthodox seeds stored at ‘low seed moisture content’ undergo seed deterioration, predominantly due to lipid peroxidation, initiated by autoxidation or enzymatic oxidation of unsaturated or polyunsaturated fatty acids. This peroxidation leads to emission of volatile compounds. The quantity of VOCs emitted is positively correlated with the advancement of seed deterioration. With respect to the seed germination process, exposure of seeds to ‘high moisture conditions’ leads to increased respiration, triggers glycolysis and mobilization of storage reserves, resulting in the emission of volatile metabolic products. The quantity of VOCs emitted on commencement of metabolic activity in germinating seeds depends on (1) vigour status and (2) amount of storage reserves. Since it has been established that there is a significant difference between high and low vigour seeds with respect to quantity and profile of VOCs emitted, there is great potential for utilizing the VOC profile to obtain a quick and reproducible test of vigour status of crop seeds. In order to harness the VOC profile for quick assessment of vigour status of seeds, research has to be taken up to develop standard protocols for fingerprinting of VOCs for the purpose of seed vigour assessment and to fix the standard volatile biomarker(s) specific to crop and vigour status of seeds.

The influence of SO2 as the Criegee intermediate scavenger on the heterogeneous oxidation of oleic acid

Abstract As a well-known Criegee intermediate (CI) scavenger, SO2 can react with CIs in the gas phase to form sulphuric acid, which can be further converted to sulfate aerosols, which make an important contribution to haze formation. Despite the potential importance, the interaction of SO2 with the CIs produced by heterogeneous oxidation of unsaturated fatty acids remains largely unclear. In this work, the heterogeneous reactions of oleic acid (OA) thin films with O3 and O3/SO2 mixture gases are studied under four different relative humidities (RHs): 5%, 30%, 60% and 80%, using microscopic Fourier transform infrared (micro-FTIR) spectrometer combined with a gas-flow system. A detailed comparison on formation rates of ester and intensity ratios of 1742 cm−1 band (envelope C O of ester) to 1712 cm−1 band (feature C O of carboxyl) between the two reaction systems shows that the addition of SO2 inhibits the conversion of carboxyl to ester at any RH. As the SO2 concentration increases, the formation rates and final relative amount of ester decrease. Based on these data, it can be concluded that SO2 consumes part condensed-phase CIs produced by ozonolysis of OA, resulting in a significant inhibition in ester formation. The present results provide an important atmospheric implication on the reaction between SO2 and condensed-phase CIs, which may be a missing sulfate production pathway in the atmosphere.