Rationalizing the formation of damascenone: synthesis and hydrolysis of damascenone precursors and their analogues, in both aglycone and glycoconjugate forms

Storage of megastigma-4,6,7-trien-3,9-diol (5), and megastigma-3,4-dien-7-yn-9-ol (6) in aqueous ethanol solution at pH 3.0 and 3.2 gave exclusively damascenone (1) and damascenone adducts at room temperature. The diol (5) had half-lives for the conversion of 32 and 48 h at pH 3.0 and pH 3.2, respectively. The acetylenic alcohol (6) had half-lives of 40 and 65 h at the same pH levels. In order to study the reactivity of the C-9 hydroxyl function in 5 and in the previously investigated allenic triol 2, two model compounds, megastigma-4,6,7-trien-9-ol (7) and megastigma-6,7-dien-9-ol (8) were synthesized. No 1,3-transposition of oxygen to form analogues of damascenone was observed when 7 and 8 were subjected to mild acidic conditions. Such transposition takes place only with highly conjugated acetylenic precursors such as 6 or tertiary allenic alcohols such as 2. The placement of glucose at C-3 of 5 and at C-9 of 6 gave the glycosides 9 and 10, respectively. The effect of such glucoconjugation was to increase the observed half-lives by a factor of only 1.6-1.7 for the allenic glucoside 9, and by 2.1-2.2 for the acetylenic glucoside 10. These studies indicate that the effect of glycosylation on damascenone formation is probably not important on the time scale of wine making and maturation.     

Effect of SO2 concentration on polyphenol development during red wine micro-oxygenation

A Merlot wine in 15 L research tanks was subjected to micro-oxygenation at 10 mL O2 per liter of wine per month over a 16 week period with additions of 0, 50, 100, and 200 mg/L SO2. A large decrease in monomeric anthocyanins and flavan-3-ols was seen in wines with a lower concentration of SO2, coupled with an increase in nonbleachable pigments; an increase in tannin, measured using precipitation with methyl cellulose; and a greater size and red coloration of a proanthocyanidin extract obtained using Sephadex LH-20. These changes were largely suppressed in wines initially treated with 200 mg/L SO2 and occurred more slowly in wines stored in bottles in the absence of O2. The concentration of SO2 is shown to regulate the polyphenol chemistry involved in the formation of polymeric pigments and changes in tannin structure affecting wine astringency.     

基于DFI-RSE电子鼻传感器阵列优化的葡萄酒SO2检测

酿造过程中SO2的监控是葡萄酒产业信息化和葡萄酒品质保障的关键。针对传统SO2测定方法操作复杂、耗费时间长等问题,该研究提出基于电子鼻技术建立葡萄酒中SO2检测方法。为提高电子鼻检测性能,提出一种基于动态特征重要度-递归传感器消除（Dynamic Feature Importance-Recursive Sensor Elimination,DFI-RSE）的气体传感器阵列优化算法。将最大信息系数（Maximum Information Coefficient,MIC）作为度量变量间关系的标准,定义DFI选择兼顾高有效性与低冗余性的特征构成特征子集。进一步计算特征子集中的传感器重要度,结合RSE移除重要度较低的传感器,获得最优阵列组合。采用偏最小二乘回归（Partial Least Squares Regression,PLSR）、多层感知器（Multi-Layer Perceptron,MLP）、支持向量回归（Support Vector Regression,SVR）和贝叶斯岭回归（Bayesian Ridge Regression,BRR）对DFI-RSE优化前后阵列的检测能力进行比较。结果表明,针对间隔40 mg/L、0～200 mg/L范围内不同SO2添加量的葡萄酒样品,优化后阵列的传感器数量由原来的16个降低为8个,特征数量减少了59%,4种回归模型的决定系数均高于0.98,其中MLP模型检测效果最佳,均方根误差为7.73 mg/L,优于原始阵列且节省了运行时间。所建立的基于电子鼻的葡萄酒SO2添加量检测和相应的阵列构建与优化方法为葡萄酒酿造过程中SO2的有效监控技术研究提供参考。     

Fate of fumonisin B(1) in corn kernel steeping water containing SO(2)

Six 100 ppm fumonisin B(1) (FB(1)) solutions were prepared by dissolving pure standard in six different solvents containing SO(2). Two of the solvents contained 0.2 or 0.4% SO(2) in distilled water. The other four solvents were obtained by steeping corn kernels at 60 degrees C in a 0.2% SO(2) aqueous solution for 6, 12, 24, or 48 h. After the addition of FB(1), all solutions were maintained at 60 degrees C for 7 days. Fumonisin B(1) content in each solution was determined in triplicate by HPLC. Steeping corn kernels in 0.2% solution at 60 degrees C for 6 h seems to be the most effective treatment to decrease the amount of FB(1).     

Fate of quinoxyfen residues in grapes, wine, and their processing products

Quinoxyfen is a new fungicide that belongs to the family of the quinolines, recently introduced to control powdery mildew (Uncinula necator). In this paper the fate of quinoxyfen residues from vine to wine and in their processing products was studied. After the last of four applications at the recommended rate, 0.38 mg/kg of residue was found on the grapes, which is under the legal limit fixed in Italy (0.5 mg/kg). The degradation rate was according to a pseudo-first-order kinetics (r = 0.964) and the half-life was 7.24 days. Vinification was carried out with and without maceration. During the vinifications without maceration <50% of the residues passed from the grapes to the musts. Separation of the lees (8%) from the must by centrifugation caused no detectable residues in centrifuged must. At the end of fermentation with and without maceration no quinoxyfen residues were determinable in the wine. No effect on the alcoholic or malolactic fermentation was observed even in the presence of higher quinoxyfen concentrations than those found in the grapes at harvest time. During fermentation, the yeasts partially degraded the pesticides and completly adsorbed them. Bacteria, on the other hand, do not have any degradative effect on the pesticides. The raisins obtained by sun-drying did not contain any residues, whereas those obtained by oven-drying show the same amount of residues as in the fresh grapes. During the sun-drying process the fruit weight decreased by a factor of 4; the decrease in the oven-drying was equivalent. Samples of dregs and liquid lees, fortified with high levels of quinoxyfen. were double-distilled. The first dregs distillate, with an alcohol content of 32.1%, did not show any residues, whereas the first lees distillate, with an alcohol content of 34.5%, showed 7% of the initial residues. After the second lees distillation, the obtained product showed an alcoholic content of 81.2% and no residues of quinoxyfen (<0.01 mg/kg).     

Precursors to damascenone: synthesis and hydrolysis of isomeric 3,9-dihydroxymegastigma-4,6,7-trienes

A series of four isomeric 3,9-dihydroxymegastigma-4,6,7-trienes, 8, has been prepared. The (3S,6R,9S) isomer of 8 proved to be identical to an isomer of this compound tentatively identified as an intermediate in the formation of damascenone from an allene triol. Each of the four isomers, when hydrolyzed independently of each other at pH 3.0 and 25 degrees C, produced product mixtures in which the major product was damascenone (1). Contrary to expectation, 3-hydroxydamascone (5) was not observed in any of the hydrolyses. Consequently, the mechanism of formation of damascenone proposed earlier requires modification. In each hydrolysis, the product mixtures showed the presence of a second isomer of 8, produced by epimerization during hydrolysis. Chiral analysis on a Cyclosil B column revealed that this epimerization was occurring at C(3) in each of the hydrolyses.     

Fate of iprovalicarb, indoxacarb, and boscalid residues in grapes and wine by GC-ITMS analysis

The behavior in field and the transfer from grapes to wine during winemaking of iprovalicarb, indoxacarb, and boscalid was studied. The residue levels found in grapes were far below the MRLs set for grapes in EU, accounting at harvest time 0.81, 0.43, and 4.23 mg/kg for iprovalicarb, indoxacarb, and boscalid, respectively. The residue levels in the samples treated with boscalid may have residual problems (due to an accumulation effect) if repeated field treatments will be performed. Winemaking experiments showed a complete transfer of all pesticide from grapes to the must, while in wine the residues were low or negligible due to the adsorbing effect of lees and pomace. The clarification experiments showed a good removal of pesticide residues from the wine media, for all pesticides. The GC-ITMS method showed good performance with adequate recoveries ranging from 75 to 115%, and good method limits of quantitation (LOQs) and of determination (LODs) far below MRLs.     

An assessment of the role played by some oxidation-related aldehydes in wine aroma

The levels of important oxidation-related aldehydes, such as methional, phenylacetaldehyde, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, methylpropanal, 2-methylbutanal, and 3-methylbutanal, were determined in 41 different wines belonging to different types (young whites and reds, natural sparkling wines, oxidized young whites and reds, Sherry, aged red wines, Port wines). Except (E)-2-hexenal and (E)-2-heptenal, all of them could be found at levels above threshold. Different compositional patterns were identified: Sherry wines have large amounts of branched aldehydes but not of (E)-2-alkenals, wines exposed to oxygen can have large amounts of (E)-2-alkenals but not of branched aldehydes, while aged wine and Port have relatively large amounts of both classes of compounds. Different sensory tests confirmed the active sensory role of these compounds and revealed the existence of interactions (additive or synergic) between them and with other wine volatiles. (E)-2-Alkenals are related to flavor deterioration, while branched aldehydes enhance dried fruit notes and mask the negative role of (E)-2-alkenals.     

Does SO2 fumigation change the chemical defense of woody plants: The effect of short-term SO2 fumigation on the metabolism of deciduous Salix myrsinifolia plants

The effect of a moderate increase in atmospheric sulphur dioxide on the production of phenolic secondary chemicals, soluble sugars and phytomass distribution within plants was investigated in six willow (Salix myrsinifolia Salisb.) clones. The plants were cultivated for 3 weeks under 0.11 ppm of SO₂ (300 μg m^?3). The production of salicin and chlorogenic acid was significantly reduced under increased SO₂. However, salicortin, 2′-O-acetylsalicortin, (+)-catechin and two unknown phenolics did not show any clear trend. The increase in SO₂ did not affect the glucose, fructose and sucrose contents. The final weight of the SO₂-treatment plants was significantly greater than that of the control plants: the leaf, stem and root phytomass was from 14 to 48% greater under increased SO₂. All the clones showed the same trend, although there was a significant variation in phytomass production. Our results indicate, although not consistently that even a short-term exposure of enhanced atmospheric SO₂ may change moderately the accumulation pattern of willow phenolics.     

Concentrations and depositions of SO2, SO4 2− etc. in a Chongqing suburban forested area

During the period from 25 May 1991 to 30 May 1992 the atmospheric concentrations and depositions of oxides of sulfur were continuously measured in a suburban masson pine forest which is currently experiencing severe dieback, in Chongqing, China. The annual mean concentrations of SO₂ and particulate SO₄ ^2? were 220 μ g/m³ (77 ppbv) and 32 μ g/m³ respectively. The atmospheric concentrations of these sulfur compounds were high in late autumn and winter. The annual wet and dry depositions of sulfur to the forest as measured by throughfall and stemflow were 93.1 and 46.6 kgSha^?1a^?1 respectively. These depositions are among the highest level ever reported in the world. Althogh the cause of the dieback of the masson pine trees has not been unequivocally determined, it is probable that the direct impact of SO₂ is more likely the cause than acid deposition.     

SO2 emission scenarios of Eastern China

Under the National Key Project in Eighth Five-year Plan, a study was carried out on forecasting SO2 emission from coal combustion in China, with a special emphasis on eastern area. 3 scenarios, i.e. “Optimistic”, “Pessimistic” and “Business as Usual” scenario were developed trying to cover changing scale of coal consumption and SO2 emission from 1990 to 2020. “Top-down” approach was employed, and coal consumption elasticity was defined to project future economic growth and coal consumption. SO2 emission scenarios were outlined, based on coal consumption, estimated sulfur content level and prospective SO2 control situation. Emission level for each 1° longitude × 1° latitude grid cell within eastern China was also estimated to show geographical distribution of SO2 sources. The results show that SO2 emission of China will increase rapidly, if current situation for energy saving and SO2 control is maintained without improvement; measures enhanced reasonably with economic growth could stop further increase of emission by 2010; realization of more encouraging objective to keep emission at even below 1990 level needs, however, more stringent options. Share of eastern China in country's total emission would increase until 2000, while general changing tendency would principally follow the scenarios of whole country.     

Fate of lignins in soils: A review

Lignins are amongst the most studied macromolecules in natural environments. During the last decades, lignins were considered as important components for the carbon cycle in soils, and particularly for the carbon storage. Thus, they are an important variable in many soil-plant models such as CENTURY and RothC, and appeared determinant for the estimation of the soil organic matter (SOM) pool-size and its stabilization. Recent studies challenged this point of view. The aim of this paper was to synthesise the current knowledge and recent progress about quantity, composition and turnover of lignins in soils and to identify variables determining lignin residence time. In soils, lignins evolve under the influence of various variables and processes such as their degradation or mineralization, as well as their incorporation into SOM. Lignin-derived products obtained after CuO oxidation can be used as environmental biomarkers, and also vary with the degree of degradation of the molecule. The lignin degradation is related to the nature of vegetation and land-use, but also to the climate and soil characteristics. Lignin content of SOM decreases with decreasing size of the granulometric fractions, whereas its level of degradation increases concomitantly. Many studies and our results suggest the accumulation and potential stabilization of a part of lignins in soils, by interaction with the clay minerals, although the mechanisms remain unclear. Lignin turnover in soils could be faster than that of the total SOM. Different kinetic pools of lignins were suggested, which sizes seem to be variable for different soil types. The mechanisms behind different degradation kinetics as well as their potential stabilization behaviour still need to be elucidated.     

SO2诱导拟南芥气孔保卫细胞致死效应研究

以拟南芥叶片下表皮为材料,研究了SO2体内衍生物——亚硫酸钠和亚硫酸氢钠混合液（3：1,mmol·L^-1／mmol·L^-1）对气孔保卫细胞的致死作用。结果表明,浓度0．5～4．5mmol·L^-1的SO2衍生物处理表皮3h可引起保卫细胞死亡,细胞死亡率呈浓度依赖性增高。抗坏血酸（AsA）或过氧化氢酶（CAT）与SO2衍生物共同作用时,保卫细胞死亡率显著降低。Ca^2＋合剂乙二醇双四乙酸（EGTA）或Ca^2＋通道抑制剂LaCl3与SO2衍生物共同作用时,保卫细胞死亡率亦显著降低。研究发现,一定浓度的SO2可诱导拟南芥保卫细胞死亡,胁迫可能通过诱导活性氧、激活质膜钙通道,造成胞外Ca^2＋内流,引发细胞死亡。     

SO2 Transformation in controlled atmosphere leading to the production of aerosol particles

The photochemical transformation of SO₂ and the generation of aerosol particles are investigated in a variety of atmospheres, with and without initial aerosols, in clean and polluted air, and with various pollutants. The pollutants in addition to the SO₂ include O₃, NO, NO₂ and water vapor in a variety of combinations. The most striking finding is, that only with the combination of SO₂, NO₂, and H₂O is the aerosol particle production large.     

Dependence of SO2 integrated exposure rates on SO2 concentration,wind velocity,temperature, and relative humidity

Integrated exposure rates for SO₂ of a standardized physico-chemical receptor and corresponding SO₂ concentrations and meteorological variables have been measured at various sites in the state of Northrhine Westphalia, Germany from 1982 to 1986. The dependence of exposure rates and deposition velocities of the receptor on SO₂ concentration and meteorological variables has been investigated within the framework of various regression models. A contribution of prime importance to exposure rates of the product of SO₂ concentrations and the square root of wind velocities averaged over exposure time has been established. The model explains 87% of variation. Deposition velocities for this receptor turn out to be of the order of 1 cm s ^?1. A corresponding regression model between deposition velocities and the square root of wind velocities unexpectedly explains only a minor amount of variation of this quantity.     

Smoke-derived taint in wine: effect of postharvest smoke exposure of grapes on the chemical composition and sensory characteristics of wine

Although smoke exposure has been associated with the development of smoke taint in grapes and subsequently in wine, to date there have been no studies that have demonstrated a direct link. In this study, postharvest smoke exposure of grapes was utilized to demonstrate that smoke significantly influences the chemical composition and sensory characteristics of wine and causes an apparent 'smoke taint'. Verdelho grapes were exposed to straw-derived smoke for 1 h and then fermented according to two different winemaking treatments. Control wines were made by fermenting unsmoked grapes. Sensory studies established a perceivable difference between smoked and unsmoked wines; smoked wines were described as exhibiting 'smoky', 'dirty', 'earthy', 'burnt' and 'smoked meat' characteristics. Quantitative analysis, by means of gas chromatography-mass spectrometry, identified guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol, and furfural in each of the wines made from smoked grapes. However, these compounds were not detected in the unsmoked wines, and their origin is therefore attributed to the application of smoke. Increased ethanol concentrations and browning were also observed in wines made from grapes exposed to smoke.     

Inhibitory effects of SO2 on biofiltration of aldehydes

Biofiltration is a suitable method for eliminating volatile biodegradable organic chemical from waste gases. However, if substances inhibiting microbiological activity are present in the waste gas, biofiltration efficiencies will be poor. Results are presented on inhibition of biofiltration by SO₂. Inhibition was observed first in a pilot scale experiment on odor abatement in a food processing factory. Then it was shown in laboratory scale experiments that SO₂. concentrations less than 10 ppm have no measurable effect. A concentration of 40 ppm results in 60% inhibition but original efficiency can be restored when the SO₂ supply is shut off. A concentration of 100 PPM of SO₂ results in complete and permanent inhibition.     

Atmospheric SO2 Pollution and Acidity of Rain in Changchun China

It is mainly SO₂ that bring about acid rain in China. Changchun City, which is located in Northeast China, is a typical city that is polluted by SO₂ from coal combustion in winter. In winter, the daily mean concentration of atmospheric SO₂ is about 0.10mg/m³ and about 5 times as high as in summer, and the daily highest concentration usually appears in daybreak and nightfall. The monitored lowest pH value of rainwater was 4.8 in spring and the range of pH value of rain/snow was 5.2–6.0 in winter, 4.8–5.8 in spring, 5.4–6.4 in summer, 5.6–6.4 in autumn, and the annual mean pH value of rainfalls was 5.8 (1999–2000). Because the alkaline aerosol from soil, meteorological conditions etc., is unfavorable to acid rain formation, even though high SO₂ emission intensity existed in winter, the acid rain did not appear obviously. The aerosol character, climate conditions in Northeast China are important factors for the acid rain formation, although SO₂ emission is the original cause.