海产品储藏过程气味特征研究及其与鲜度关系初探

海产品储藏不当,极易腐坏变质,鲜度是评价海产品品质的关键指标.海产品储藏过程中,气味的变化一般都先于性状的变化,气味特征的变化可用于预示海产品鲜度的变化.传统的化学方法采用某些挥发性有机物(VOCs),如三甲胺等来评价海产品鲜度,具有局限性和不准确性~([1,2]).     

吹扫捕集-气相色谱-质谱法快速测定同序列地下水和土壤中的37种挥发性有机物

建立了吹扫捕集-气相色谱-质谱法(GC-MS)测定同序列地下水和土壤样品中37种挥发性有机物(VOCs)含量的方法.分别采集地下水、土壤样品并封装于40 mL棕色吹扫瓶中,采用全自动固液一体吹扫捕集装置,于20℃吹扫11 min,于250℃脱附1.7 min,于280℃烘烤8 min,将分离后的VOCs利用气相色谱-质...     

顶空固相微萃取-气相色谱-质谱法同时测定饮用水源水中24种VOCs

建立了同时测定饮用水源水中24种挥发性有机物(VOCs)的顶空固相微萃取-气相色谱-质谱法.用75 μm CarboxenTM-Polydimethylsiloxane(CAR-PDMS)固相微萃取柱顶空萃取水样中的VOCs,VOCs用气相色谱-质谱联用仪检测,采用内标法定量.对萃取柱涂层、样品盐度、萃取温度和萃取时间等样品前处理条件进行了优化,VOCs的检出限在0.03～0.31 μg/L之间,线性相关系数r＞0.996(二氯甲烷和三氯甲烷除外).对饮用水源水实际水样0.50μg/L和1.00 μg/L两个加标浓度水平的回收率进行了测定,三氯甲烷回收率均值分别为104％和142％,其余VOCs回收率分别为90.0％～120％和88.0％～110％,除二氯甲烷和三氯甲烷外,其余VOCs测定结果的相对标准偏差均小于15.0％(n=6).该方法适用于饮用水源水中挥发性有机物的监测分析.     

浅谈消费产品中挥发性有机物质检测技术

首先介绍了消费品产品检测中几种常见的挥发性有机物质(VOCs)检测技术,其中包括顶空-气相色谱-质谱法、吹扫捕集-气相色谱法、热解析-气相色谱-质谱法、液相色谱-二级管阵列检测法等技术,并介绍了这几种检测技术的原理、适用样品及浓度范围,详述各种检测技术的优缺点。并针对汽车内饰物中,使用热解析-气相色谱-质谱法测定苯系物和液相色谱-二级管阵列检测法测定醛酮类物质进行挥发性有机物质的同时检测,做了初步探讨。     

免疫算法用于复杂样品的GC-MS快速分析

建立了一种基于免疫算法的复杂样品气相色谱-质谱联用(GC-MS)快速分析方法, 该方法采用快速温度程序测定复杂样品的GC-MS信号, 再通过快速解析得到各组分的信息. 计算过程中, 采用各种可能存在于混合物中的组分质谱作为算法的输入, 按照保留时间的顺序逐一对重叠的质谱信号进行解析, 得到各组分的色谱信息. 对于混合物中实际存在的组分可得到该组分的色谱流出曲线, 而对于混合物中不存在的组分所得色谱流出曲线几乎为零. 采用所建立的方法对含有16个组分的有机磷农药混合物进行了分析, 在保留时间10 min内得到了所有组分的色谱信息.     

李子发酵前后挥发性成分及游离氨基酸的变化分析

为探究李子发酵为李子酵素前后挥发性成分及游离氨基酸的变化规律,采用顶空固相微萃取-气相色谱-质谱法(HS-SMPE-GC-MS)和氨基酸分析仪分析了其中的挥发性成分和游离氨基酸.将新鲜的李子样品去核、匀浆、熟化后,加入白砂糖和发酵剂发酵3个月制备李子酵素.发酵前后的样品用顶空固相微萃取仪提取挥发性成分,然后通过H P-...     

莪术药材的闪蒸气相色谱测定及其模式识别分析研究

建立了莪术药材的闪蒸-气相色谱法(FE-GC),采用FE-GC测定了3个产地的9个莪术样品.0.4mg的粉末样品, 在200℃下闪蒸,经色谱分离,基于闪蒸色谱图上分离鉴定到的35个共有峰的相对强度,结合化学模式识别即主成分分析和系统聚类分析法对莪术样品进行了鉴别分析.3个产地的莪术样品可以很好地得到区别.本法快速、简便、准确, 不失为药材质量控制的良好方法.     

全二维气相色谱－飞行时间质谱测定PBAT生物降解膜中挥发性有机物

采用顶空固相微萃取（HS－SPME）结合全二维气相色谱－飞行时间质谱技术（GC × GC－TOF MS）对聚己二酸对苯二甲酸丁二酯（PBAT）生物降解膜中主要挥发性有机物（VOCs）进行分析测定,并考察了萃取纤维头类型、平衡温度、平衡时间、萃取时间对HS－SPME在生物降解膜中VOCs测定的影响。结果显示：以聚二甲基硅氧烷－二乙烯基苯－碳分子筛羧乙基（PDMS－DVB－CAR）为萃取头、80 ℃下分别平衡与萃取目标物10 min与40 min,在进样口260 ℃条件下解析3 min后进GC × GC－TOF MS分析,采用基质谱数据库与结构谱图等定性,内标法定量,生物降解膜中共检出55种VOCs,按结构可分为苯系物、萘、醛酮、醇、酯、茚、胺、酚、其它类共9类。相比常规一维气相色谱,全二维气相色谱可有效分离生物降解膜中的同系物、异构体及干扰物质,获得准确的定性结果。方法的日内和日间相对标准偏差（RSD）均不高于19%,表现出较好的稳定性和可重复性。对不同厂家（A、B、C、D） PBAT生物降解膜中的55种VOCs进行检测并多元统计分析,主成分分析结果显示,PBAT A与PBAT B样品重叠,VOCs差异较小,PBAT A+B、PBAT C与PBAT D有明显差异,VOCs差异较大,表明同类型不同来源的生物降解膜中具有不同的物质组成。热图分析显示,PBAT D中的苯系物与PBAT A+B中的萘、胺类、酚类化合物含量较高,而PBAT C中的VOCs普遍偏低。由此表明建立的HS－SPME结合GC × GC－TOF MS检测方法具有准确可靠、简单、快速等优点,对PBAT生物降解膜的安全评价及使用具有一定的参考价值。     

顶空固相微萃取-气质联用分析小麦储藏过程中挥发性成分变化

采用顶空固相微萃取(HS-SPME)和气相色谱-质谱联用(GC-MS)对不同储藏时间弱(强)筋小麦中的挥发性物质进行提取、鉴定与分析.选用复合萃取纤维二乙烯基苯-炭烯-聚二甲硅氧烷共聚物(DVB/CAR/PDMS)50 μm涂层,对萃取温度、时间、样品用量和解析时间进行优化.结果表明: HS-SPME测定挥发性物质的最佳前处理条件样品量20 g, 萃取温度75 ℃, 萃取时间60 min, 260 ℃条件下解析5 min;经鉴定分析小麦挥发性成分主要有烃类、醛类,其次为醇类、酮类;挥发性成分总含量在储藏6个月内均呈现先降后增的趋势.弱筋小麦的烃类挥发物相对量随储藏时间延长而快速增加,醛类相对含量先降后升,而酮类和醇类相对含量则逐渐下降;强筋小麦中除烃类相对含量呈先下降而后快速增加外,其余各类挥发物含量均与弱筋小麦呈现相同的规律.储藏6个月后,变化较明显的挥发性物质有己醇、己醛、2,6,10-三甲基-十二烷、十五烷和二十烷.     

热脱附-吹扫捕集-气相色谱质谱联用在大气挥发性有机物分析中的应用探索

采用热脱附结合吹扫捕集(P&T)技术对大气中挥发性有机物(VOCs)进行富集,并用气相色谱质谱(GC/MS)进行分析检测,建立了一种大气中多组分VOCs分析方法。将热脱附-吹扫捕集-气相色谱质谱联用技术应用于大气挥发性有机物分析中,使样品经过吸附管及捕集阱双重富集后再进入GC/MS检测,VOCs分析结果部分目标物检出限可达到0.1 ng/L,实际平行样品检测结果相对偏差小于30%,且可同时对54种VOCs进行定性定量分析。     

A preliminary study of plant aroma profile characteristics by a combination sampling method coupled with GC-MS

Plant aroma profile characteristic is an important bio-information. In this study, a sampling method in combination with headspace solid phase microextraction (HSSPME), simultaneous distillation extraction (SDE) and steam distillation (SD), followed by gas chromatography-mass spectrometry (GC-MS) detection, was used to study the aroma profile characteristics of the fresh and stale samples of common tomato, cherry tomato, durian and longan, and of the different samples of Chinese mango and Allium varieties. The typical aroma volatiles of these samples were isolated and identified according to the different degrees of certainty. The different samples showed different aroma profile characteristics when principal component analysis (PCA) was conducted to analyze the data of the aroma profile chromatograms. Then the crucial aroma volatiles contributing greatly to the clustering differences of the aroma profile characteristics of the fresh and stale common tomato, cherry tomato, durian and longan were identified by common model strategy. These compounds are potential bio-markers of plant metabolism, but further study is needed. Continuous investigations for the aroma profile characteristics of common tomato during storage and chive during growth were conducted to distill the potential bio-information from the plant metabolism processes. The saturated hexanal of common tomato increased during storage, whereas the unsaturated hexenal reduced. The accumulating trends of volatile sulfides were observed during chive growth. The preliminary results related with the corresponding bio-information could provide helpful clues to the study of plant's secondary metabolism process and benefit quality control.     

A review of advances and new developments in the analysis of biological volatile organic compounds

Biological volatile organic compounds (VOCs) are interlinked to biological metabolism and bacterial populations localized on the surfaces of biological samples. The characteristics of biological VOCs at different physiological status or metabolism phases are various, which contain crucial bio-information. In this review, the significance of the study of biological VOCs was introduced, and crucial techniques greatly influencing the investigation were summarized and reviewed including efficient sampling, suitable analytical and bio-information distillation techniques. From the preliminary identification of biological VOC components to the interpretation of biological VOC characteristics is a great improvement in this field, which would provide more abundant bio-information during biological metabolism. Owing to complicated biological VOC compositions, any single sampling or bio-information distillation method could not obtain complete biological VOCs and interpret the biological VOC characteristics, and would result in the loss of effective bio-information. The combination of some suitable sampling and bio-information distillation techniques for the study of biological VOCs and the related bio-information will be a novel trend in the future.     

Rapid prediction of moisture content of dehydrated prawns using online hyperspectral imaging system

Because the shape of prawn is not round, spectroscopy instruments cannot measure the spectra of the whole prawn without containing background information. In this study, an online hyperspectral imaging system in the spectral region of 380–1100 nm was developed to determine the moisture content of prawns at different dehydrated levels. Hyperspectral images of prawns were acquired at different dehydration periods. The spectra of prawns then were extracted from hyperspectral images based on ‘Manual Prawn Mask’ and ‘Automatic Prawn Mask’, respectively. Spectral data were analyzed using partial least squares regression (PLSR) and least-squares support vector machines (LS-SVM) to establish the calibration models, respectively. Successive projections algorithm (SPA) was first applied for the optimal wavelength selection in the hyperspectral image analysis. Out of 482 wavelengths, only twelve wavelengths (428, 445, 544, 569, 629, 672, 697, 760, 827, 917, 958, and 999 nm) were selected by SPA as the optimum wavelengths for moisture prediction. Based on these optimum wavelengths, a multiple linear regression (MLR) calibration model was established and used to obtain the moisture distribution of each prawn. The overall results of this study revealed the potentiality of hyperspectral imaging as an objective and non-destructive method to obtain the content and distribution of moisture of prawns whose shapes are not round.     

Preliminary study on application of mid infrared spectroscopy for the evaluation of the virgin olive oil "freshness"

The freshness of virgin olive oils (VOO) from typical cultivars of Garda regions was evaluated by attenuated total reflectance (ATR) and Fourier transform infrared (FTIR) spectroscopy, in combination with multivariate analysis. The olive oil freshness decreased during storage mainly because of oxidation processes. In this research, 91 virgin olive oils were packaged in glass bottles and stored either in the light or in the dark at room temperature for different periods. The oils were analysed, before and after storage, using both chemical methods and spectroscopic technique.Classification strategies investigated were partial least square discriminant analysis (PLS-DA), linear discriminant analysis (LDA), and soft independent modelling of class analogy (SIMCA).The results show that ATR-MIR spectroscopy is an interesting technique compared with traditional chemical index in classifying olive oil samples stored in different conditions. In fact, the FTIR PCA results allowed a better discrimination among fresh and oxidized oils, than samples separation obtained by PCA applied to chemical data. Moreover, the results obtained by the different classification techniques (PLS-DA, LDA, SIMCA) evidenced the ability of FTIR spectra to evaluate the olive oil freshness. FTIR spectroscopy results are in agreement with classical methods. The spectroscopic technique could be applied for the prediction of VOOs freshness giving information related to chemical modifications. The great advantages of this technique, compared to chemical analysis, are related to rapidity, non-destructive characteristics and low cost per sample. In conclusion, ATR-MIR represents a reliable, cheap and fast classification tool able to assess the freshness of virgin olive oils.     

Characterization of sorption mechanisms of solid-phase microextraction with volatile organic compounds in air samples using a linear solvation energy relationship approach

The linear solvation energy relationship (LSER) model was used to characterize interactions responsible for sorption of volatile organic compounds (VOCs) in air samples on six different solid-phase microextraction (SPME) fibers at 296K and zero relative humidity. The polydimethylsiloxane and polyacrylate fibers sorption data were also modeled at different relative humidities in the range of 10-90% and influence of water vapors on the extraction process is discussed. The LSER equations were obtained by a multiple regression of the distribution coefficients of 14 probe solutes on an appropriate SPME fiber against the solvation parameters of the solutes. The derived LSER equations successfully predicted the VOC distribution coefficients and the selectivity of individual SPME fibers for the various volatile solutes. The LSER approach coupled with SPME is a relatively simple and reliable tool to rapidly characterize the sorption mechanism of VOCs with various stationary phases and may potentially be applied to design and test new chromatographic materials for sampling or separation of VOCs.     

Determination of antioxidant properties of 26 Chilean honeys and a mathematical association study with their volatile profile

Radical scavenging activity (RSA), antioxidant content (TEAC), total phenolic compounds content (TPCC) and volatile profile (VOCs) were measured in 26 honeys obtained from the Valparaiso Region (Chile). Persea americana honey was the most interesting sample according to these evaluated parameters. A Projection to Latent Structures (PLS) based algorithm was used to model the possible relationship between antioxidant activity, total phenolic compounds content and volatile profile. Concerning the volatile profile, only nine volatile compounds, of a total of fifty, showed dependence on antioxidant activity and total phenolic compounds content.     

High impact of vehicle and solvent emission on the ambient volatile organic compounds in a major city of northwest China

Monitoring of ambient volatile organic compounds（VOCs） was conducted within typical residentialcommercial area in the city of Xi’an in northwest China during typical ozone（O₃） episodes, to investigate the major contributors to the characteristic of ambient VOCs and their impact on O₃ production. In the residential-commercial area, diurnal variation of VOCs was highly impacted by vehicle exhaust, fuel evaporation, and local solvent use. Relative higher contributions（up to 60...     

Fish freshness detection by a computer screen photoassisted based gas sensor array

In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be “portable” and “simple”. In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8 h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30 min.The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities.     

δD and δ13C analyses of atmospheric volatile organic compounds by thermal desorption gas chromatography isotope ratio mass spectrometry

This paper describes the establishment of a robust method to determine compound specific δD and δ(13)C values of volatile organic compounds (VOCs) in a standard mixture ranging between C(6) and C(10) and was applied to various complex emission samples, e.g. from biomass combustion and car exhaust. A thermal desorption (TD) unit was linked to a gas chromatography isotope ratio mass spectrometer (GC-irMS) to enable compound specific isotope analysis (CSIA) of gaseous samples. TenaxTA was used as an adsorbent material in stainless steel TD tubes. We determined instrument settings to achieve a minimal water background level for reliable δD analysis and investigated the impact of storage time on δD and δ(13)C values of collected VOCs (176 days and 40 days of storage, respectively). Most of the standard compounds investigated showed standard deviations (SD)<6‰ (δD) when stored for 148 days at 4 °C. However, benzene revealed occasionally D depleted values (21‰ SD) for unknown reasons. δ(13)C analysis demonstrated that storage of 40 days had no effect on VOCs investigated. We also showed that breakthrough (benzene and toluene, 37% and 7%, respectively) had only a negligible effect (0.7‰ and 0.4‰, respectively) on δ(13)C values of VOCs on the sample tube. We established that the sample portion collected at the split flow effluent of the TD unit can be used as a replicate sample for isotope analysis saving valuable sampling time and resources. We also applied TD-GC-irMS to different emission samples (biomass combustion, petrol and diesel car engines exhaust) and for the first time δD values of atmospheric VOCs in the above range are reported. Significant differences in δD of up to 130‰ were observed between VOCs in emissions from petrol car engine exhaust and biomass combustion (Karri tree). However, diesel car emissions showed a high content of highly complex unresolved mixtures thus a baseline separation of VOCs was not achieved for stable hydrogen isotope analysis. The ability to analyse δD by TD-GC-irMS complements the characterisation of atmospheric VOCs and is maybe used for establishing further source(s).     

Changes in Volatile Compounds in Short-Term High CO2-Treated ‘Seolhyang’ Strawberry (Fragaria × ananassa) Fruit during Cold Storage

‘Seolhyang’ strawberry is harvested before it is fully ripened and treated with CO₂ to extend the shelf-life. However, the volatile changes in the ‘Seolhyang’ strawberry after short-term CO₂ treatment have not been investigated, although the volatile profile is an important quality attribute. Herein, we investigated the effect of short-term high CO₂ treatment on the changes in the composition of volatile compounds in ‘Seolhyang’ strawberries at two ripening stages (i.e., half-red and bright-red) during cold storage using headspace solid-phase microextraction and gas chromatography-mass spectrometry. Furthermore, the effect of CO₂ treatment on fruit quality with respect to the aroma was investigated. A total of 30 volatile compounds were identified. Storage increased the volatile compound concentrations, and the total concentration of volatiles in the CO₂-treated strawberries was lower than that of the untreated strawberries during storage. The production of some characteristic strawberry volatiles (e.g., 4-methoxy-2,5-dimethyl-3(2H)-furanone) was inhibited in CO₂-treated strawberries. However, CO₂ treatment helped maintain the concentrations of hexanal and 2-hexenal, which are responsible for the fresh odor in strawberries. Interestingly, CO₂ treatment suppressed the production of off-odor volatiles, acetaldehyde, and hexanoic acid during strawberry storage. Thus, short-term CO₂ treatment may help maintain the fresh aroma of strawberries during cold storage.