Optimization of Headspace Single-Drop Microextraction Coupled with Gas Chromatography–Mass Spectrometry for Determining Volatile Oxidation Compounds in Mayonnaise by Response Surface Methodology

In this assay, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography–mass spectrometry (GC–MS) as a simple, low-cost and rapid method has been developed and validated for determining volatile oxidation compounds including hexanal and heptanal in mayonnaise. The main microextraction variables affecting the HS-SDME procedure such as extraction temperature and time, stirring rate, and amount of NaCl were optimized by response surface methodology employing a central composite design. Obtained results demonstrated that higher yield of extracted analytes could be achieved under the following optimal conditions: extraction temperature of 45 °C, extraction time of 16 min, stirring rate at 700 rpm, and addition of 2 g NaCl. The optimized HS-SDME/GC–MS method was validated for oxidized mayonnaise samples (50 °C/48 h) by calculating analytical parameters (linearity, precision, accuracy, and sensitivity). Good linearity (R ²?>?0.99) was observed by plotting calibration curves of extracted hexanal and heptanal over the concentration range of 0.025–10 μg g^?1, and the repeatability of the method, expressed as relative standard deviation, were found to be 4.04 % for hexanal and 3.68 % for heptanal (n?=?7). After the microextraction process of spiked mayonnaise sample, high levels of relative recovery were obtained for hexanal (107.33 %) and heptanal (91.43 %). The detection limits were 0.008 ng g^?1 and 0.021 ng g^?1 for hexanal and heptanal, respectively, while quantification limits of hexanal and heptanal were calculated to be 0.027 ng g^?1 and 0.071 ng g^?1, respectively. The possibility of the HS-SDME followed GC–MS to determine and quantify volatile oxidation compounds such as hexanal and heptanal was confirmed by analyzing commercial fresh mayonnaise stored at 4 and 25 °C during 3 months.     

STATIC HEADSPACE CAPILLARY GC METHOD FOR DETERMINING CHANGES OF VOLATILES FROM HEATED CHICKEN BREAST MEAT

Volatile compounds generated during heat processing are associated with the flavor quality of cooked muscle foods. A static headspace GC method using a capillary column was developed for the analysis of volatiles from chicken breast meat previously heated to end-point temperatures (EPTs) of 60 to 80C at 5C intervals. A semi-automatic static headspace GC system with a fused silic capillary column (5% bonded methyl phenyl silicone, 50 m × 0.25 mm × 0.25 μm) was incorporated. Up to 23 peaks were detected. Major volatiles including propanal, pentanal, hexanal, heptanal and octanal increased as the EPT increased, especially between 60 and 70C. The effect of cooking EPT on volatile generation was determined more accurately by using the capillary column than by the packed column reported previously. Controlling EPT is important in ensuring the flavor quality and stability of precooked poultry meat products.     

速冻加工过程中慈姑挥发性风味成分分析

为探讨速冻加工对慈姑风味的影响,采用顶空固相微萃取与气相色谱-质谱联用技术,分析烫漂和速冻加工处理过程中慈姑挥发性风味化合物的组分及变化。结果表明：慈姑烫漂和速冻处理后分别检测到33 种和29 种挥发性风味化合物。烫漂慈姑中相对含量较高的为烯类、含硫类、醚类、醛类和醇类等,二甲基硫醚、壬醛、辛醛、己醛、D-柠檬烯、柠檬烯、石竹烯、庚醇、泪柏醚等对烫漂慈姑风味有较大贡献;速冻慈姑中相对含量较高的为烯类、醚类、醛类、醇类和含硫类等,二甲基硫醚、壬醛、辛醛、己醛、庚醛、石竹烯、戊醛、庚醇、苯甲醛、2-戊基呋喃、泪柏醚等对速冻慈姑有较大贡献。慈姑经速冻后降低了对慈姑产生负面影响的风味化合物相对含量,如二甲基硫醚;增加了对风味有较大贡献的化合物种类,有利于风味化合物的保存和改善。     

'Flavor-fade' and Off-Flavors in Ground Roasted Peanuts As Related to Selected Pyrazines and Aldehydes

Headspace volatiles from ground roasted Florunner medium peanuts, stored at 65°C for 1–68 days, were separated and identifled by GC/MS. Selected pyrazines, resulting from Maillard browning and selected aldehydes from autoxidation were evaluated to determine their mechanistic contributions to peanut ‘flavor-fade.’ The 2,6-dimethylpyrazine, 2-methylpyrazine, 2-ethyl-5-methyl or 6-methylpyrazine, 2,3,5-trimethylpyrazine, and pentanal remained constant during storage (p < 0.05). Flavor scores for ‘roasted peanut’ decreased slightly, then leveled off and hex-anal, heptanal, octanal and nonanal increased during storage (p < 0.05). Oxidative ‘rancid’ flavor scores and thiobarbituric acid values also increased during storage (p < 0.05). Based on results, the ‘flavor-fade’ of stored roasted peanuts is due to masking of pyrazines and other ‘roasted peanut’ flavor compounds by large quantities of low-molecular weight aldehydes from lipid autoxidation, and not due to polymerization and/or degradation of the pyrazines.     

Changes of Headspace Volatiles in Milk with Riboflavin Photosensitization

ABSTRACT:  Effects of fluorescent light, riboflavin, ascorbic acid, sodium azide, and butylated hydroxyanisole (BHA) on the volatiles in milk at 4 °C were determined using a combination of headspace-solid phase microextraction (HS-SPME), gas chromatography (GC), and mass spectrometry (MS). Pentanal, hexanal, heptanal, and dimethyl disulfide were formed only in the milk stored under light and increased significantly as the duration of light exposure increased from 0 to 8 h and the concentration of added riboflavin increased from 5 to 50 ppm ( P  < 0.05). As fat content in milk increased, peak areas of pentanal, hexanal, and heptanal increased significantly ( P  < 0.05) while those of dimethyl disulfide did not change significantly ( P  > 0.05). Sodium azide prevented the formation of dimethyl disulfide in milk, implying that dimethyl disulfide can be formed through singlet oxygen oxidation (type II pathway). Addition of ascorbic acid and BHA reduced the formation of hexanal, heptanal, and dimethyl disulfide significantly ( P  < 0.05). Generation mechanisms of pentanal seem to be different from those of hexanal and heptanal in milk. Both singlet oxygen oxidation (type II pathway) and free radicals (type I pathway) play important roles in the formation of light-induced volatiles in milk.     

Freshness characterisation of whiting (Merlangius merlangus) using an SPME/GC/MS method and a statistical multivariate approach

BACKGROUND: The freshness of whiting was studied at five stages of ice storage by comparing the analysis of volatile compounds obtained through solid phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) with two sensory methods. RESULTS: Of the volatile compounds identified, 38 were analysed using a statistical multivariate approach and classified according to their role in the estimation of freshness during storage as markers of freshness or spoilage. Regarding the evolution of the presence or absence of individual compounds, three categories were defined. For example, the volatile compounds propanal, hexanal, 1‐penten‐3‐ol, pentanal, 2,3‐pentanedione, 1‐penten‐3‐one, heptanal, (E)‐2‐pentenal, 2,3‐octanedione, (Z)‐2‐penten‐1‐ol, 1‐pentanol, butanal, octanal, 3,5,5‐trimethyl‐2‐hexene, 1‐hexanol and 4,4‐dimethyl‐1,3‐dioxane appeared highly relevant, because they are found throughout storage and can be divided into several categories that are directly related to the quality of fish. CONCLUSION: SPME/GC/MS combined with a statistical multivariate approach may be a useful method to identify volatile compounds and characterise fish freshness during storage. Copyright © 2010 Society of Chemical Industry     

Aroma analysis of light-exposed milk stored with and without natural and synthetic antioxidants

The effect of antioxidants, added in a single initial dose or in weekly additions to extended shelf life milk, was evaluated over 6 wk of lighted storage at 4 degrees C. Light-induced oxidation was measured by determining pentanal, hexanal, heptanal, and 1-octen-3-ol contents. Weekly addition of a combination of butylated hydroxyanisole and butylated hydroxytoluene (100 mg/kg of milk fat, each) maintained heptanal content of milk at levels comparable to light-protected milk, whereas an initial single addition of alpha-tocopherol significantly decreased hexanal content over the first 4 wk of storage. Odor-active compounds associated with light-induced oxidation included 2,3-butanedione, pentanal, dimethyl disulfide, hexanal, 1-hexanol, heptanal, 1-heptanol, and nonanal. The addition of butylated hydroxyanisole and butylated hydroxytoluene in a single initial addition resulted in decreases in pentanal and hexanal odor, but not in heptanal and 1-heptanol odor, whereas the addition of alpha-tocopherol and ascorbyl palmitate decreased pentanal and heptanol odor, but not hexanal and heptanal odor.     

基于气相-离子迁移谱技术分析烤羊肉串的挥发性风味成分

为构建市售烤羊肉串特征风味指纹图谱,采用气相-离子迁移谱（gas chromatography-ion mobility spectroscopy,GC-IMS）对5家烧烤店的市售烤羊肉串风味物质进行测定与分析。结果表明:共检测鉴定出82种挥发性风味化合物,包括单体和二聚体,其中烤羊肉串样品共有的物质有:醛（戊醛、壬醛、辛醛、己醛、庚醛、异戊醛、苯甲醛、3-甲硫基丙醛）,酮（2-庚酮、2-丁酮、甲基庚烯酮、3-羟基-2-丁酮、γ-丁内酯）,醇（戊醇）和酯（乙酸乙酯）。通过构建加香辛料烤制和未加香辛料烤制的羊肉串风味指纹图谱,可明显观察不同市售烤羊肉串样品异同,羊肉串在加入香辛料烤制后甲基庚烯酮的含量降低;2-庚酮、丙酮和戊醇的含量升高;己醛、壬醛、庚醛、异戊醛、苯甲醛、3-羟基-2-丁酮的含量几乎不变,可能为羊肉串烤制后本身的特征风味物质。依据指纹图谱信息对烤羊肉串样本进行主成分分析（Principal Component Analysis,PCA）,结果显示,不同市售烤羊肉串样本特征风味具有一定的差异。综上,气相-离子迁移谱可检测烤羊肉串挥发性化合物风味成分和进行多变量分析,为烤羊肉串风味评价提供一定的理论和实际应用价值。     

Precooking Method Affects Warmed-over Flavor of Broiler Breast Patties

Broiler breast patties cooked in a water bath (85°C vs 95°C) or oven (160°C vs 180°C) to an internal temperature of 83°C were stored at 3°C foT 3 days, reheated, and evaluated by headspace GC and thio-barbituric acid (TBA) methods. Cooking temperature within the same cooking medium had no effect on TBA values or headspace GC profiles of cooked, stored samples. During post-cooking storage TBA values and several headspace volatiles increased. The changes were more severe in oven-cooked than water-cooked patties, which could have been partly due to lower moisture content of the oven-cooked patties. Significant correlations were found between TBA values and several major headspace volatiles (pentanal, hexanal, heptanal, and total volatiles).     

Atmospheric chemistry of nonanal

During the Southern Oxidants Study 1999 field campaign at Dickson, TN, we conducted measurements of the n-aldehydes propanal, pentanal, hexanal, heptanal, octanal, and nonanal. Propanal and nonanal tended to have the largest concentrations, with afternoon maxima of approximately 0.3 ppb. These aldehydes typically represented a significant fraction of the VOC reactivity defined as k(OH)[VOC]. However, this information is misleading with regard to the impact of these aldehydes on ozone formation, as their oxidation can represent a significant NOx sink. Motivated by the relatively large nonanal concentrations, we conducted a laboratory study of the products of the nonanal + OH reaction. The OH + nonanal reaction rate constant was determined via the relative rate technique and found to be 3.6 (+/- 0.7) x 10(-11) cm3 molecule(-1) s(-1). Under conditions of high [NO2]/[NO], we determined that 50 +/- 6% of OH-nonanal reaction occurs via abstraction of the aldehydic H-atom through measurement of the peroxynonanyl nitrate yield. We also studied the production of organic nitrates from OH reaction with nonanal in the presence of NO. As expected, a major product (20% at large [NO]/[NO2]) of this reaction was 1-nitrooxy octane. We calculate that the branching ratio for 1-nitrooxy octane formation from peroxyoctyl radicals is 0.40 +/- 0.05. On the basis of these measurements, we find that for more than 50% of the time OH reacts with nonanal (for midday summer conditions) an organic nitrate or PAN compound is formed, making this important atmospheric aldehyde an effective NOx sink.     

固相微萃取- 气质联用检测鸭汤中挥发性风味成分

采用固相微萃取-气质联用的方法,对麻鸭、北京鸭、水鸭、洋鸭4种鸭汤中的挥发性风味成分进行分离鉴定。共鉴定出159种挥发性风味化合物,包括醛类31种、酮类13种、醇类24种、酸类3种、酯类14种、烃类44种、胺类4种、醚类3种、呋喃类3种、含N化合物2种、含S化合物10种、含S、N化合物5种、其他化合物3种。4种鸭汤中共有的风味化合物有12种,分别为戊醛、己醛、庚醛、(Z)-2-庚烯醛、辛醛、(E)-2-辛烯-1-醛、(E)-2-壬烯醛、癸醛、(E)-2-癸烯醛、(E,E)-2,4-癸二烯醛、3-乙基-2-甲基-1,3-己二烯、2-戊基-呋喃。     

米饭中关键风味化合物的分析

采用固相微萃取与同时蒸馏提取两种方法,应用香气提取物分析结合气味活性值对米饭中的风味物质进行气相色谱-质谱分析,从而确定米饭风味中的关键风味化合物。结果表明,米饭中共鉴定出40 种风味化合物,包括醛类13 种、醇类7 种、酮类3 种、酯类4 种、酚类4 种,及吡啶、噻唑、吲哚、呋喃类等;醛类物质在米饭风味物质中的含量最大;2-乙酰基-1-吡咯啉是米饭中最主要的风味活性化合物。综合两种处理方式发现,2-乙酰基-1-吡咯啉、香草醛、1-辛烯-3-醇、壬醛、4-乙烯基苯酚、4-乙烯基创木酚、己醛、辛醛、庚醛、戊醛等物质对米饭整体风味轮廓起到关键作用。     

Migration of volatile degradation products into ozonated water from plastic packaging materials

Migration of volatile degradation products from poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE) bottles, polypropylene (PP) caps and ethyl vinyl acetate (EVA) liners into ozonated water was measured. Polymer strips were immersed in deionized and distilled water with ozone concentrations of 0.5, 2.5 and/or 5 mg kg^-1 inside 35-ml vials, which were clamp-sealed and stored at 40°C for 10 days. A purge-and-trap unit was developed to extract volatile products from the ozonated water in vials. The extractables were trapped in an adsorbent tube and analysed using a GC-MS coupled with an automated thermal desorber (ATD). Mass spectra were interpreted by comparison with a NIST mass spectral library, and an internal standard method was used to quantify the extractables of interest. Several volatile compounds found in ozonated water that had been in contact with PP, EVA and HDPE polymers included butanal, pentanal, hexanal, heptanal, octanal, nonanal, 2,2-dimethyl propanal, 3-hexanone, 2-hexanone and heptanone. These compounds could cause off-taste and off-odour with a low organoleptic threshold. In general, the concentrations of these volatile compounds increased with an increased exposure to ozone. The highest concentration found was 14.1 ± 0.6 μg kg^-1 for hexanal with a 5 mg kg^-1 ozone treatment of PP caps. Even at a treatment level of 5 mg kg^-1 ozone, which is greater than 10 times the current regulatory limits for bottled water, the extractables migrating from those polymers were within the levels permitted by the FDA. For the PET sample, no significant peaks were observed before or after ozonation. These results imply that PP caps containing EVA liners may be major sources of off-odour and taste in ozonated bottled water.     

Aroma profiles of vegetable oils varying in fatty acid composition vs. concentrations of primary and secondary lipid oxidation products

The aroma compositions of oxidised sunflower oil, linseed oil and a blend thereof (85/15) were compared with frequently used indicators for primary and secondary lipid oxidation. Primary lipid oxidation was followed by the formation of conjugated dienes, secondary lipid oxidation by proponal and hexanal formation. Highest concentrations of conjugated dienes and propanal were measured in the linseed oil, followed by the blend and sunflower oil, respectively. Highest concentrations of hexanal were determined in the blend. At similar primary oxidation levels, volatile compounds of the oils were isolated in a model mouth system and subsequently analysed by gas chromatography/sniffing port analysis. Propanal, pentanal, 1-penten-3-one, hexanal, 1-pentanol, octanal, 1-octen-3-one, 1-octen-3-ol and (E,Z)-2,4-heptadienal possessed detectable odours. Comparing the three oils, most aroma compounds and greatest intensities were determined in the blend. Conjugated diene concentrations did not predict the formation of aroma compounds adequately. Although propanal and hexanal concentrations were reasonable indicators for aroma development in linseed and sunflower oil, respectively, neither of the indicators predicted aroma development in all three oils sufficiently.     

Volatiles Production and Lipid Oxidation in Irradiated Cooked Sausage as Related to Packaging and Storage

Irradiation dose affected production of volatiles in vacuum-and aerobic-packaged cooked pork sausage, but its effect on TBARS was minor. Storage increased production of volatiles and changed their composition only in aerobic-packaged sausage. Among volatile components, 1-heptene and 1-nonene were influenced most by irradiation dose, and aldehydes by packaging type. TBARS and volatiles of vacuum-packaged irradiated cooked sausage did not correlate well. However, TBARS had very high correlation with amount of aldehydes, total volatiles, ketones and alcohols with long retention times in aerobic-packaged pork sausage. Heptene and 1-nonene could be indicators for irradiation; and propanal, pentanal, and hexanal for oxygen-dependent changes of cooked meat.     

Reduction of Warmed-Over Flavor Volatiles from Freeze-Dried Lean by Supercritical CO2 Extraction

Supercritical carbon dioxide (SC-CO₂) was used to extract warmed-over flavor (WOF) volatiles from cooked, freeze-dried beef at 40°C and pressures of 10.3 MPa or 30 MPa after 2 days storage. WOF markers, hexanal, heptanal, octanal, nonanal, and 2,3-octanedione, were identified in the volatiles profile of precooked beef by dynamic headspace extraction and gas chromatography-mass spectrometry before and after CO₂ extraction. TBARS and levels of WOF markers increased over 2 days storage. There was a reduction in WOF markers at both extraction pressures. The higher pressure led to greater reduction of WOF markers (e.g., hexanal: 73.5%) than the lower pressure (e.g., hexanal: 60.3%), notably for heptanal and nonanal. SC-CO₂ may be applicable for reducing WOF volatiles from precooked meats.     

Antioxidant activities of defatted sesame meal extracts in cooked turkey breast and thigh meats

The antioxidant properties of methanolic extract of raw and roasted (at 200 °C for 60 min) defatted sesame‐meal in turkey breast and thigh meat systems were determined. The TBARS values of turkey breast and thigh meat added with 0.1% of roasted defatted sesame‐meal extract were 18.8% and 24.7%, respectively, lower than those of untreated controls after 5 days of storage. The turkey meats added with roasted defatted sesame‐meal extract had higher a* and b* values than those of controls due to the browning effects occurred in sesame seeds during roasting. The amounts of volatile hydrocarbons (pentane, hexane, heptane, and octane) and carbonyls (propanal, butanal, pentanal, hexanal and heptanal) significantly decreased by the addition of roasted defatted sesame‐meal extract. In particular, the amount of hexanal, the most predominant volatile compound in the cooked turkey meat, decreased by 74% and 83% in turkey breast and thigh meat, respectively. However, raw defatted sesame‐meal extract did not show significant antioxidant activity in turkey meats. These results indicated that heat treatment of sesame‐meal increased the antioxidant activities of methanolic extract of defatted sesame meal. Copyright © 2007 Society of Chemical Industry     

基于电子鼻、HS-GC-IMS和HS-SPME-GC-MS分析五种水产原料的风味特征

采用电子鼻（Electronic Nose）、顶空-气相色谱-离子迁移谱（Headspace Gas Chromatography Ion Mobility Spectrometry, HS-GC-IMS）和顶空-固相微萃取-气相色谱-质谱（Headspace Solid Phase Micro-extraction Gas Chromatography-mass Spectrometry, HS-SPME-GC-MS）技术与感官评价相结合,对广西南美白对虾、禾花鱼、罗非鱼、金丝鱼及马氏珍珠贝五种优势水产原料中挥发性成分进行分析。结果表明:感官评价显示五种水产原料腥味较突出;电子鼻分析显示五种水产原料的整体气味主要是无机硫化物、芳香成分（有机硫化物）及甲基类;GC-IMS共检出75种化合物（定性37种）,共有的化合物为:正辛醛、苯甲醛（单体）、戊醛（单体）、2-戊酮（单体）、2-蒎烯、2-丁酮（单体）、丁醛（二聚体）、丙酸乙酯、正己醛（单体）、苯甲醛（二聚体）、庚醛（单体）;GC-MS共鉴定出57种挥发性化合物,其中醇类、醛类及芳香族类化合物为这五种水产原料主要的挥发性化合物;1-辛烯-3-醇和壬醛为五种水产原料共有的关键性风味物质。     

基于电子鼻与SPME-GC-MS法分析咸鲅鱼加工过程挥发性风味成分变化

本文研究咸鲅鱼加工过程中挥发性风味成分的变化情况。采用电子鼻与固相微萃取-气质联用法(SPME-GC-MS)分别检测鲜鱼、腌制、干制4、10、24、36、48 h 7个不同阶段的风味成分变化。结果表明,腌制和干燥阶段风味变化明显。7个阶段挥发性风味成分种类数分别为27、37、53、42、47、45种以及51种。其中,成品咸鱼中三甲胺、乙二醇单丁醚、己醛、1-戊烯-3-醇、壬醛、正辛醛、庚醛、异戊醛含量较高,相对含量分别为11.05%、7.21%、6.65%、6.35%、5.69%、4.56%、3.52%和3.37%。腌制和干燥是风味产生的主要加工阶段。醛类、醇类、酮类和烃类是主要的挥发性物质的种类,其中己醛、壬醛、正辛醛、庚醛、(Z)-4-庚烯醛、苯甲醛、1-戊烯-3-醇、1-辛烯-3-醇是咸鲅鱼风味的主要成分。因此可通过控制腌制和干燥条件改善咸鲅鱼风味。     

基于GC-IMS技术分析炖煮过程中大鲵头汤挥发性风味物质

为探明大鲵头汤挥发性风味物质种类,采用气相-离子迁移谱联用技术（GC-IMS）考察了不同炖煮时间（30、60、90、120和150 min）鲵头汤挥发性风味物质的变化。结果表明,GC-IMS 技术对不同炖熬时间鲵头汤样品中45个信号峰中,鉴定出35种挥发性风味物质,包括醛类17种、酯类8种、酮类4种、醇类4种、酸类1种和吡嗪类1种;随着炖熬时间的延长（30~150 min）,鲵头汤中丙醛、戊醇、乙醇、庚醛、2-庚酮、乙酸乙酯、壬醛和正辛醛浓度明显降低,而正己醇、丁醛、2-甲基丁酸乙酯、丙酸己酯、2-丁酮、戊醛、异戊醛、苯甲醛、丙酸乙酯和丁酸乙酯浓度逐渐上升。该文构建了炖熬过程中鲵头汤挥发性风味指纹,对不同炖熬时间鲵头汤挥发性风味轮廓实现了可视化表征,为今后鲵头汤品质控制以及质量标准制定提供了参考。