Changes in the sotolon content of dry white wines during barrel and bottle aging

GC-MS in electron ionization mode (EI) was used as a simple, sensitive method for assaying sotolon [4,5-dimethyl-3-hydroxy-2(5) H-furanone] in various dry white wines. The impact of barrel-aging conditions, that is, whether yeast lees were present or not, on the formation of sotolon in dry white wines was then studied. The sotolon content was highest in dry white wines aged in new barrels without lees, often exceeding the perception threshold (8 microg/L). These results demonstrated that yeast lees were capable of minimizing the formation of sotolon in dry white wines during aging. The sotolon and oxygen contents of several bottle of the same white wine were also compared 7 years after bottling. At the range of dissolved oxygen concentrations generally measured, between 5 and 100 microg/L, the sotolon content remained below its perception threshold in wine. The perception threshold was exceeded only in wines with oxygen concentrations above 500 microg/L. The presence of dissolved oxygen in the wine samples analyzed also resulted in a decrease in their free sulfur dioxide content.     

Analysis of benzothiazole in Italian wines using headspace solid-phase microextraction and gas chromatography-mass spectrometry

Benzothiazoles are a part of the molecular structure of a large number of natural products, biocides, drugs, food flavors, and industrial chemicals. They also appear in the environment mainly as a result of their production and use as rubber vulcanization accelerators. A new headspace solid-phase microextraction (HS-SPME) method for analysis of benzothiazole (BTH) in wine is described. This method is fast, inexpensive, and does not require solvents. The detection limit of BTH in wine was 45 ppt with linearity up to 100 ppb. The quantification of BTH is performed by the standard additions method and does not require the use of an internal standard. We have analyzed 12 wines from different grape varieties grown in several regions, using SPME extraction and gas chromatography-mass spectrometry (GC-MS) detection. Under these experimental conditions, benzothiazole was found in all wines analyzed. Concentration levels in samples varied from 0.24 microg/L (Vermentino) to 1.09 microg/L (Franciacorta).     

Survey on the presence of butyltin compounds in chinese alcoholic beverages,determined by using headspace solid-phase microextraction coupled with gas chromatography-flame photometric detection

The use of butyltin compounds in some food packaging leads to the contamination of liquid food and may result in subsequent adverse effects on people's health through the food chain. A survey of butyltin compounds in Chinese alcoholic beverages purchased from retail markets was carried out by using solid-phase microextraction (SPME) followed by gas chromatography coupled with flame photometric detection. Forty-four samples including wine, liquor, and champagne were studied. The levels of monobutyltin and dibutyltin ranged from <0.016 to 5.687 and from <0.0022 to 33.257 microg of Sn/L, respectively. Low levels of tributyltin were detected. The presence of dibutyltin in wine samples was further confirmed by GC-MS. The result indicated that dry wines generally contained more dibutyltin than sweet wines. The concentrations of butyltin compounds in liquor samples were lower than those in wine samples.     

Determination of geosmin, 2-methylisoborneol, and a musty-earthy odor in wheat grain by SPME-GC-MS, profiling volatiles, and sensory analysis

Geosmin and 2-methylisoborneol-compounds responsible for the musty-earthy off-odor of wheat grain, were isolated by SPME and analyzed by GC-MS. Carboxen/PDMS/DVB fiber coating was selected because of its highest extraction efficiency. Concentrations of geosmin and 2-methylisoborneol as low as 0.001 microg/kg were detected in SIM mode using ion trap mass spectrometer. Apart from GC-MS determination of geosmin and 2-methylisoborneol, various methods for evaluating the musty-earthy off-odor caused by these compounds in wheat grain are presented. Sensory profile analysis differentiated wheat grain into sound and off-flavored, but the method was tedious. Similar groupings, however, were obtained using more rapid methods such as comparison of volatile profiles using SPME-fast GC with PCA projection of data and metal oxide (MOS) based electronic nose.     

Sulfur volatiles in guava (Psidium guajava L.) leaves: possible defense mechanism

Volatiles from crushed and intact guava leaves (Psidium guajava L.) were collected using static headspace SPME and determined using GC-PFPD, pulsed flame photometric detection, and GC-MS. Leaf volatiles from four common citrus culitvars were examined similarly to determine the potential component(s) responsible for guava's protective effect against the Asian citrus psyllid (Diaphorina citri Kuwayama), which is the insect vector of Huanglongbing (HLB) or citrus greening disease. Seven sulfur volatiles were detected: hydrogen sulfide, sulfur dioxide, methanethiol, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), methional, and dimethyl trisulfide (DMTS). Identifications were based on matching linear retention index values on ZB-5, DB-Wax, and PLOT columns and MS spectra in the case of DMDS and DMS. DMDS is an insect toxic, defensive volatile produced only by wounded guava but not citrus leaves and, thus, may be the component responsible for the protective effect of guava against the HLB vector. DMDS is formed immediately after crushing, becoming the major headspace volatile within 10 min. Forty-seven additional leaf volatiles were identified from LRI and MS data in the crushed guava leaf headspace.     

Headspace solid-phase microextraction use for the characterization of volatile compounds in vegetable oils of different sensory quality

Headspace solid-phase microextraction (HS-SPME) was used to isolate the volatile compounds, which are formed during peroxidation of fatty acids in vegetable oils. Isolated compounds were characterized by GC-MS and quantified using GC with FID detection. Four fibers for HS-SPME method development were tested, and the divinylbenzene/carboxene/PDMS fiber was selected as providing the best detection of analyzed compounds. Extraction curves, limits of detection, repeatability, and linearity were investigated for 14 aldehydes, ketones, hydrocarbons, and alcohols being products of fatty acids autoxidation. Limits of detection for 11 of these were below 1 microg/L. For quantitative purposes, to minimize the influence of temperature on hydroperoxide formation and the changes in the volatiles profile of the extracts, sampling was performed at 20 degrees C. For compound characterization by GC-MS, sampling temperature of 50 degrees C was applied. The developed method was applied to the analysis of refined and cold-pressed rapeseed oil stored at 60 degrees C for 10 days, and for 10 different vegetable oils of various degree of peroxidation. All samples were subjected to sensory analysis. The results of PCA sensory analysis were related to the amount of volatile compounds isolated by SPME method. In cases where the amount of compounds was highest, the samples were perceived as the worst, whereas those with low levels of volatile compounds were the most desired ones according to sensory evaluation. The relation was observed for both total volatiles, quantified C5-C9 aldehydes, and 14 compounds selected in method development. SPME revealed to be a rapid and sensitive method for the extraction and quantitation of trace volatile compounds from plant oils even at ambient temperature.     

Volatile sulfur compounds in irradiated precooked turkey breast analyzed with pulsed flame photometric detection

Ionizing radiation is an effective processing technology for pathogen inactivation on various foods. However, the generation of off-odor is a concern for some irradiated meats. This study was conducted to investigate volatile sulfur compounds of precooked ready-to-eat turkey breast as functions of radiation dose and subsequent storage. Precooked turkey breast was exposed to 0, 1, 2, 3, 4, and 5 kGy of gamma radiation and stored for 14 days at 5 degrees C. Volatile sulfur compounds were extracted using solid phase microextraction (SPME), followed by gas chromatographic separation and pulsed flame photometric detection. Irradiation dramatically increased concentrations of hydrogen sulfide, sulfur dioxide, methanethiol, and dimethyl disulfide. The rate of increase was higher at low doses (0-2 kGy) than at higher doses of 3-5 kGy. Carbon disulfide was the only volatile sulfur compound that was reduced by irradiation. Concentrations of all volatile sulfur compounds decreased in both irradiated and nonirradiated samples stored at 5 degrees C.     

Determination of free (pH 2.2) sulfite in wines by flow injection analysis: collaborative study

A method for the determination of free sulfite in wine by flow injection analysis (FIA) is described. The method involves liberation of sulfur dioxide from the wine at pH 2.2, with detection by decolorization of a malachite green solution. The method was collaboratively studied, and the results indicated an average reproducibility of 12% for white wine samples (average level 12.1 ppm SO2) and 26% for red wine samples (average level 3.1 ppm). When the FIA method was compared to an aeration/oxidation method, the results indicated a high degree of correlation between the 2 methods. The FIA method has been adopted by AOAC official first action.     

Analysis of acrylamide in a complex matrix of polyacrylamide solutions treated by heat and ultraviolet light

A recently developed headspace/solid-phase microextraction/gas chromatograph (GC) equipped with a nitrogen-phosphorus detector (NPD) (HS/SPME/GC/NPD) method was used to analyze acrylamide formed in an aqueous polyacrylamide solution (25%) treated by heat or photo-irradiation. Original polyacrylamide contained 0.43 +/- 0.11 microg/mL of acrylamide. When polyacrylamide solution was heated at 70 degrees C for 16 h with 0.5% potassium persulfate, the amount of acrylamide increased to 1.02 +/- 0.11 microg/mL. When polyacrylamide solution was irradiated by UV (lambda = 300 nm) for 16 h with 0.05% 2-anthraquinone sulfate sodium salt, the amount of acrylamide increased to 1.14 +/- 0.54 microg/mL. Polyacrylamide has been used in cosmetic formulations. The present study, therefore, suggests that there is another route of acrylamide exposure to humans in addition to foods and beverages.     

Analysis of phenolic and other aromatic compounds in honeys by solid-phase microextraction followed by gas chromatography-mass spectrometry

The solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was used for the analysis of phenolic and other aromatic compounds in honey samples from different floral origin. Different parameters affecting the efficiency of the extraction, such as the type of the stationary phase of the fiber, NaCl and acetic acid addition, and extraction time, were optimized for the detection of the maximum number of compounds in the shortest analysis time. A total of 31 compounds were detected, with most of them identified and quantified by GC-MS. The principal component analysis (PCA) was applied to the data matrix; the results allowed for the differentiation between honeydew and nectar honeys on the basis of the salicylic acid concentration. It was found that this acid has a high contribution in the honeydew group (71.2-705.9 microg/100 g of honey) compared to the nectar honey group (0-47.6 microg/100 g of honey). The comparison of data in each honey group enabled us to characterize the floral source of some honeys using some aromatic compounds as markers.     

基于氨基酸组成的黄酒酒龄电子舌鉴别

该研究采用电子舌结合化学计量学方法用于黄酒酒龄的快速鉴别。为确证黄酒样品酒龄,采用氨基酸分析仪分析了1年陈、3年陈和5年陈黄酒中20种氨基酸,并利用主成分分析（principal component analysis,PCA）对氨基酸数据进行了分析。采用电位型电子舌采集了不同酒龄黄酒样品的味觉指纹信息,并采用判别分析（discriminant analysis,DA）方法结合味觉指纹信息建立黄酒酒龄快速鉴别模型。采用偏最小二乘法（partial least squares regression,PLSR）建立电子舌响应信号与氨基酸含量之间的相关关系。氨基酸数据结合PCA分析表明所有样品均标注正确;电子舌结合DA所建黄酒酒龄鉴别模型可将3个年份预测集样品正确区分;异亮氨酸（Ile）、天门冬氨酸（Asp）、酪氨酸（Tyr）和缬氨酸（Val）与电子舌相关性高,模型的相对分析误差（Residual predictive deviation, RPD）高于2。研究表明电位型电子舌结合判别分析是黄酒龄鉴别的稳健方法。     

Comparison of static headspace, headspace solid phase microextraction, headspace sorptive extraction, and direct thermal desorption techniques on chemical composition of French olive oils

Static headspace (SHS), headspace solid phase microextraction (HS-SPME), headspace sorptive extraction (HSSE), and direct thermal desorption (DTD) were applied to the analysis of four French virgin olive oils from Corsica. More than 60 compounds were isolated and characterized by GC-RI and GC-MS. SHS was not suited to the characterization of olive oil volatile compounds because of low sensitivity. The SPME and HSSE techniques were successfully applied to olive oil headspace analysis. Both methods allow the characterization of volatile compounds (mainly C(6) aldehydes and alcohols), which contribute significantly to the "green" flavor note of virgin olive oils. The PDMS stir bar showed a higher concentration capacity than a DVB/CAR/PDMS SPME fiber due to the higher volume of polymeric coating. DTD was a very good tool for extracting volatile and especially semivolatile compounds, such as sesquiterpenes, but requires a significant investment like that for HSSE. Finally, SPME may be a more appropriate technique for routine quality control due to its operational simplicity, repeatability, and low cost.     

Usefulness of ytterbium(III) as analytical reagent for total sulfite determination in white wine samples

Ytterbium(III) is used as reagent for the determination of sulfite by measuring the formation of the Yb(III)-sulfite complex through the variation of the light scattering intensity with time. The low solubility of this complex causes an efficient dispersion of the radiation at 490 nm, which is measured at 980 nm. Each kinetic datum is automatically obtained in only 0.5 s by stopped-flow mixing technique. The application of the initial rate method using a long emission wavelength minimizes the potential interference of fluorescent background signals from the sample matrix. The dynamic range of the calibration graph is 1-250 microg/mL, and the calculated detection limit is 0.35 microg/mL. The precision, expressed as relative standard deviation, is <6%. The method has been applied to the determination of total sulfites in white wine samples, which requires only the sample dilution and the use of two aliquots to improve selectivity. However, the matrix effect found for red wines precludes the application of the method to the direct analysis of these samples. Analytical recoveries ranged from 96.0 to 106.7%. The results obtained with the proposed method agreed with those provided by the p-rosaniline method. Unlike this method, in which toxic reagents are required, the use of ytterbium(III) as analytical reagent shows the advantage of its low acute toxic rating.     

Focused microwave assistance for extracting some pesticide residues from strawberries into water before their determination by SPME/HPLC/DAD.

A novel and simple method for the determination of some pesticide residues in strawberries using both focused microwave-assisted extraction (FMAE) and solid-phase micro extraction (SPME), coupled with high-performance liquid chromatography (HPLC), has been developed. The pesticides were first extracted from strawberries with water and the assistance of focused microwaves at 30 W for 7 min. Then, an aliquot of the resulting aqueous extract was subjected to SPME with a 60-microm thick poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber for 45 min at room temperature, with the solution being stirred at 1000 rpm. The extracted pesticides on the SPME fiber were desorbed into the SPME/HPLC interface for quantitative analysis with a diode array detector (DAD). The whole sample pretreatment procedure before chromatographic analysis did not use any organic solvents or involve any blending or centrifugation steps. The five compounds (carbendazim, diethofencarb, azoxystrobine, napropamide, and bupirimate) were chosen because they cannot be analyzed easily by GC. The efficiency of this relatively fast procedure was comparable to that of previously reported methods, with detection limits at low microg/kg levels and linear responses in the range from 0.05 to 1 mg/kg of pesticide in strawberries, with RSDs between 3 and 7.3%, depending on the analyte. In all but one case results obtained by this method for field-incurred samples were comparable to those obtained with traditional methods.     

Model aging and oxidation effects on varietal, fermentative, and sulfur compounds in a dry botrytized red wine

From harvest until wine arrives to the consumer, oxygen plays a crucial role in the definition of the final aroma. In the present research, the effect of the model oxidative aging on a dry red Botrytis wine, such as Italian Amarone, was considered. Amarone wine was submitted to model oxidative aging and then analyzed with two different approaches (SPE-GC-MS and HS-SPME/GC-MS). The same sampling plan was adopted to study the model aging of the same Amarone wine in anaerobic conditions. The HS-SPME/GC-MS method was applied to investigate for the first time the effect of the oxidative aging on a vast number of fermentative sulfur compounds. This research highlighted peculiar evolutions for several volatile compounds. In particular, benzaldehyde showed a sensitive increment during the oxidative aging, with a rate much higher than that reported for non-Botrytis red wines. On the other hand, several sulfides (dimethyl sulfide, 3-(methylthio)-1-propanol, etc.) disappeared after just 15 days of oxidative aging. A wine oxidation marker such as 3-(methylthio)-propanal was not found in any of the oxidized wines; conversely methionol-S-oxide was tentatively identified. This evidence has not been mentioned in the literature. A possible involvement of grape withering process and Botrytis in these mechanisms was supposed: a dry red wine, produced from the same but without any grape withering process and Botrytis infection (e.g., Bardolino wine), was submitted to oxidative aging and analysis. This red wine showed an evolution similar to those reported in the literature for dry red wines but significantly different from the Amarone wine.     

Chemical composition and antifungal activity of essential oils from different tissues of Japanese Cedar (Cryptomeria japonica)

In this study antifungal activities of essential oils from different tissues of Japanese cedar (Cryptomeria japonica D. Don) against four wood decay fungi and six tree pathogenic fungi were investigated. In addition, the yields of essential oils obtained by water distillation were compared and their constituents determined by GC-MS analyses. The yield of essential oils from four tissues of Japanese cedar is in the decreasing order of leaf (27.38 mL/kg) > bark (6.31 mL/kg) > heartwood (3.80 mL/kg) > sapwood (1.27 mL/kg). Results obtained from the antifungal tests demonstrate that the essential oil of Japanese cedar heartwood used against Laetiporus sulphureus and Trametes versicolor and sapwood essential oil used against L. sulphureus had strong antifungal activities at 500 mug/mL, with IC(50) values of 39, 91, and 94 microg/mL, respectively. Besides, the essential oils of Japanese cedar heartwood used against Rhizoctonia solani, Collectotrichum gloeosporioides, Fusarium solani, and Ganoderma australe had strong antifungal activities at 500 microg/mL, with IC(50) values of 65, 80, 80, and 110 microg/mL, respectively. GC-MS analyses showed that the sesquiterpene hydrocarbon compounds dominate in the essential oil from Japanese cedar heartwood, amounting to a total percentage of 82.56%, with the major compounds of delta-cadinene (18.60%), isoledene (12.41%), and gamma-muurolene (11.82%). It is proposed that the excellent antifungal activities of Japanese cedar heartwood essential oils might correlate with the presence of these compounds.     

Effect of wine inhibitors on free pineapple stem bromelain activity in a model wine system

The influence of potential inhibitors, naturally present in wine, on the activity of stem bromelain was investigated in order to evaluate the applicability of this enzyme for protein stabilization in white wine. Bromelain proteolytic activity was tested against a synthetic substrate (Bz-Phe-Val-Arg-pNA) in a model wine system after adding ethanol, sulfur dioxide (SO(2)), skin, seed, and gallic and ellagic tannins at the average range of their concentration in wine. All the inhibitors of stem bromelain activity tested turned out to be reversible. Ethanol was a competitive inhibitor with a rather limited effect. Gallic and ellagic tannins have no inhibitory effect on stem bromelain activity, while both seed and skin tannins were uncompetitive inhibitors. The strongest inhibition effect was revealed for sulfur dioxide, which was a mixed-type inhibitor for the enzyme activity. This study provides useful information relative to a future biotechnological application of stem bromelain in winemaking.     

Evolution and occurrence of 1,8-cineole (eucalyptol) in Australian wine

A new method has been developed for the quantitation of 1,8-cineole in red and white wines using headspace solid-phase microextraction (SPME) combined with stable isotope dilution analysis (SIDA) and gas chromatography-mass spectrometry (GC-MS). An extensive survey of Australian wines (44 white and 146 red) highlighted that only red wines contained significant amounts of 1,8-cineole (up to 20 μg/L). Hydrolytic studies with limonene and α-terpineol, putative precursors to 1,8-cineole, showed a very low conversion into 1,8-cineole (< 0.6%) over a 2 year period, which does not account for the difference between white and red wines. 1,8-Cineole was chemically stable in model wine solution over 2 years, and absorption from a Shiraz wine by bottle closures was most evident for a synthetic closure only (14% absorption after 1 year). Two commercial ferments at two different locations were monitored daily to investigate the evolution of 1,8-cineole throughout fermentation. Both ferments showed daily increases in 1,8-cineole concentration while in contact with grape solids, but this accumulation ceased immediately after pressing. This observation is consistent with the extraction of 1,8-cineole into the ferment from the solid portions of the grape berries.