小球藻生长因子关键挥发性风味物质研究

为确定小球藻生长因子的风味特征,比较顶空⁃固相微萃取(headspace⁃solid phase microextraction,HS⁃SPME)和溶剂辅助风味蒸发(solvent⁃assisted flavor evaporation,SAFE)对挥发性风味物质的提取效果,结合气相色谱⁃质谱联用(gas chromatography⁃mass spectrometry,GC⁃MS),对小球藻生长因子液挥发性风味物质进行鉴定;并在此基础上采用气相色谱⁃嗅闻⁃质谱联用(gas chromatography⁃olfactory⁃mass spectrometry,GC⁃O⁃MS),结合相对气味活度值(relative odor activity value,ROAV)对小球藻生长因子中关键挥发性风味物质进行研究。结果表明:与SAFE相比,HS⁃SPME提取的挥发性风味物质种类更多,相对含量更高,鉴定出50种成分,主要为醇类、酮类、杂环类及醛类等;GC⁃O⁃MS结合ROAV筛选出5种关键风味物质,分别为2⁃庚酮、2,4,5⁃三甲基恶唑、噻唑、二甲基二硫醚和2⁃乙基己醇。

Rapid and simultaneous determination of ten off-flavor compounds in water by headspace solid phase microextraction and gas chromatography-mass spectrometry

A simple and sensitive analytical procedure for the determination of multi-component compounds in water samples was developed and optimized using the headspace solid-phase microextraction(HSSPME) coupled with gas chromatography-mass spectrometry(GC-MS). Ten off-flavor compounds, including geosmin(GSM), 2-methylisoborneol(2-MIB), 2-isopropyl-3-methoxypyrazine(IPMP), 2-isobutyl-3-methoxypyrazine(IBMP), β-ionone, trans-2,cis-6-nonadienal(NDE), 2,3,4-trichloroanisole(2,3,4-TCA), 2,3,6-trichroloanisole(2,3,6-TCA), 2,4,6-trichloroanisole(2,4,6-TCA), and 2,4,6-tribromoanisole(2,4,6-TBA) were used as the target analytes. The optimization of extraction parameters including fibers types, extraction time, extraction temperature, stirring rate, sample volume, and ionic strength was carried out through the univariate approach. Ten off-flavor compounds were quantified within 50 min under the optimal conditions. Calibration curves with good linearity(r^2=0.990-0.998) were obtained in the range 1.0/2.0-100 ng/L, while the limits of detection for all compounds were lower than or close to the odor threshold concentration. Furthermore, the proposed method was applied to analyzing and determining the off-flavor compounds in real water samples from water-treatment plants.

Essential Oils Composition of Two Endemic Umbelliferae Herbs Growing Wild in Turkey

The present study was carried out to determine the essential oil composition of aerial parts of two endemic umbelliferae herbs （Malabaila lasiocarpa Boiss. and Stenotaenia macrocarpa Freyn ＆ Sint. ex Freyn） collected from Bingol （Turkey）, using headspace solid-phase microextraction method and gas chromatography （GC） interfaced with mass spectrometer analysis. Forty six and 43 compounds were identified for M. lasiocarpa and S. macrocarpa, respectively, representing 91.40% and 90.86% of their respective essential oils. Germacrene D （20.71%）,β-elemene （12.40%）, spathulenol （11.60%） and β-selinene （9.67%） were identified as the major compound of M. lasiocarpa. β-sesquiphellandrene （19.68%）, hexyl isobutyrate （12.65%） and octanal （9.53%） were found to be the major compounds ofS. macrocarpa. Essential oil composition ofM. lasiocarpa has been determined for the first time and the results have been discussed in view of chemotaxonomy, natural products and potential usefulness of these plants.

Identification of Essential Oil Composition of Four Picea Mill, （Pinaceae） Species from Canada

The aim of this study was to determine the volatile composition of essential oil of four Picea Mill. species （Piceapungens Engelm., Picea mariana （Mill.） Britton, Picea glauca （Moench） Voss., Picea rubens Sarg.） needles. The volatile components extracted from these four species needles were analyzed by using headspace solid phase microextraction （HS-SPME）/gas chromatography-mass spectrum （GC-MS） and 31, 34, 27 and 24 compounds were identified representing 91.77%, 92.70% 92.38% and 94.06% of the total oil, respectively. The major constituents were found to be bornylacetate （29.40%）, camphor （26.43%）, 13-myrcene （7.47%） and camphene （7.01%） in P. pungens; camphene （22.03%）, bornylacetate （21.64%）, α-pinene （16.62%） and borneol （7.79%） in P. mariana; bornylacetate （31.25%）, limonene （17.27%）, α-pinene （15.85%）; camphene （13.65%） in P. glauca and borneol （12.38%）, α-pinene （10.36%）, germacrene D （9.86%） and δ-cadinene （8.25%） in P. rubens. This study sought to detecte new phytochemical data on the Picea genus to help chemotaxonomy and usable of studied species.

Determination of Trihalomethanes in Water Samples Using Headspace Solid-Phase Microextraction Gas Chromatography

The chlorination process is one of the water treatment method used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, dichloromethane, dibromochloromethane and bromoform. A headspace solid-phase microextraction method has been developed for determination oftrihalomethanes in water samples. The experimental parameters such as the stirring rate, extraction time, extraction temperature and desorption time were investigated. The linearity, detection limits and percentage recovery were evaluated. The optimum conditions were stirring rate 800 rpm/min, extraction time 6 min, extraction temperature 20 ~C, desorption time 2.5 min and desorption temperature 220 ~C. The detection limits were 0.01 ~g/L and the recoveries were in the range of 86-110 %, The proposed method was successfully applied to determination of THM4 in tap water samples. The THM4 contents were varied depending on the sample sites and the season. The total THM4 contents in cool, summer and rainy season were in the range of 27.58-41.89, 32.06-60.73 and 46.26-69.87 p.g/L, respectively. Confirmation of the detected compounds in water samples were performed by gas chromatograph-mass spectrometer. The mass spectra of the target compounds in water samples is in good agreement with trihalomethanes standard spectra.

Essential Oil Composition of Endemic Pimpinella tunceliana YiId. from Turkey for the First Time

The objective of this study was to examine the essential oil ofPimpinella tunceliana Yild. growing wild in the Eastern part of Turkey for the first time. Obtained results were discussed with the genus patterns and natural products. The essential oil of P. tunceliana was analyzed by head space-solid phase microextraction （HS-SPME）/gas chromatography-mass spectrometry （GC-MS） technique, and 50 compounds were identified, representing 96.3% of the oil. The main constituents of P. tunceliana were β-caryophyllene （13.9%）, β-bisabolene （10.4%）, anethole （9.3%）, sabinene （7.5%）, limonene （6.9%） and germacrene D （6.8%）. In this study, essential oil contents of P. tunceliana that is a new and endemic species was studied for the first time, and important results were presented in respect to the composition of the oil of this new species of Pimpinella.

Analysis of Aroma Volatile Profile of Philippine Durian Pulp （Durio zibethinus Rumph, ex Murray） Using HS-SPME Coupled with GC-MS

Durian （Durio zibethinus Rumph. ex Murray） is an exotic tropical fruit known for its excellent flavor and strong distinctive aroma. Volatiles of durian pulp from different cultivars in Thailand, Malaysia and Indonesia were already reported. However, no study of volatiles from Philippine ＂Puyat＂ durian is available. ＂Puyat＂ is the most preferred by consumers in the Philippines due to its firm flesh with sweet and buttery taste. Aroma volatile compounds were analyzed by headspace solid phase microextraction （HS-SPME） method and gas chromatography-mass spectrometry （GC-MS）. Volatiles were extracted for 1 h using 65 μm PDM/DVB SPME fiber and separated by DB-WAX capillary column （30 m × 0.25 mm id × 0.25 μm film thickness）. Durian pulp produced 22 volatiles composed of 15 esters, six sulfurs and one thioacetal. Ethyl propanoate, ethyl octanoate, propyl propanoate, ethyl 2-methyl butanoate and diethyl disulfide were the major compounds identified. These compounds were also reported to be the most abundant in durian cultivars of other countries. Results of this study can then be used for future development of postharvest technologies to control the production of volatiles from Philippine durian pulp.

Aroma changes of black tea prepared from methyl jasmonate treated tea plants

Methyl jasmonate（MeJA） was widely applied in promoting food quality.Aroma is one of the key indicators in judging the quality of tea.This study examined the effect of exogenous MeJA treatment on tea aroma.The aroma components in black tea prepared from MeJA-treated fresh tea leaves were extracted using headspace solid-phase microextraction（HS-SPME） and were analyzed using gas chromatography-mass spectrometry（GC-MS） and GC-olfactometry（GC-O）.Forty-five volatile compounds were identified.The results revealed that the MeJA-treated black tea had higher levels of terpene alcohols and hexenyl esters than the untreated tea.Moreover,several newly components,including copaene,cubenol,and indole,were induced by the MeJA treatment.The activities of polyphenol oxidase and β-glucosidase in fresh tea leaves changed after the MeJA treatment.Quantitative real-time polymerase chain reaction（qRT-PCR） analysis indicated that the gene expression levels of polyphenol oxidase and β-primeverosidase were upregulated by two and three folds,respectively,by the MeJA treatment（P0.01）; however,the gene expression of β-glucosidase was downregulated to a half level.In general,the aroma quality of the MeJAtreated black tea was clearly improved.

Butyltin compounds in vinegar collected in Beijing:Species distribution and source investigation

Forty-eight vinegar samples including white vinegar, rice vinegar and mature vinegar were collected from several markets in Beijing. Butyltin compounds were determined by headspace solid-phase microextraction coupled with gas chromatography and flame photometric detector after in situ ethylation with sodium tetraethylborate. Butyltin species were detected in sixteen vinegar samples and ranged from 0.012 to 14.10 lag Sn L 1. The detection rate of white vinegar is higher than that of rice vinegar and mature vinegar. Vinegar samples with relatively high butyltin concentration (〉1.5 μg Sn L-1) were those stored in plastic bags, indicating that the plastic bag was one of the possible sources of butyltin contamination. This was further confirmed by the leaching experiments of three selected plastic bags, and monobutyltin was detected in the leaching solvents. According to the estimation, the average daily intake of total butyltin compounds through vinegar consumption is about 0.04 ng Sn/kg b.w., much lower than the Tolerable Daily Intake (TDI) of 100 ng Sn/kg b.w. set by the European Food Safety Authority (EFSA).