Solid-phase microextraction method development for headspace analysis of volatile flavor compounds

Solid-phase microextraction (SPME) fibers were evaluated for their ability to adsorb volatile flavor compounds under various conditions with coffee and aqueous flavored solutions. Experiments comparing different fibers showed that poly(dimethylsiloxane)/divinylbenzene had the highest overall sensitivity. Carboxen/poly(dimethylsiloxane) was the most sensitive to small molecules and acids. As the concentrations of compounds increased, the quantitative linear range was exceeded as shown by competition effects with 2-isobutyl-3-methoxypyrazine at concentrations above 1 ppm. A method based on a short-time sampling of the headspace (1 min) was shown to better represent the equilibrium headspace concentration. Analysis of coffee brew with a 1-min headspace adsorption time was verified to be within the linear range for most compounds and thus appropriate for relative headspace quantification. Absolute quantification of volatiles, using isotope dilution assays (IDA), is not subject to biases caused by excess compound concentrations or complex matrices. The degradation of coffee aroma volatiles during storage was followed by relative headspace measurements and absolute quantifications. Both methods gave similar values for 3-methylbutanal, 4-ethylguaiacol, and 2,3-pentanedione. Acetic acid, however, gave higher values during storage upon relative headspace measurements due to concurrent pH decreases that were not seen with IDA.     

基于判别分析法的金华火腿挥发性风味物质的形成过程分析

为了弄清金华火腿风味物质的形成过程,以60只杂交猪后腿为原料,按照传统工艺加工金华火腿,用气质联用仪(GC-MS)分析了6个工艺点的肌肉中挥发性风味物质的出峰面积,并用判别分析法分别研究了用挥发性风味物质的出峰面积和出峰面积占总出峰面积的百分率建立的判别函数判断金华火腿加工程度的可能性.研究结果表明,用金华火腿挥发性风味化合物的峰面积进行逐步判别分析,有20种挥发性化合物进入判别函数,而用峰面积占总出峰面积的百分率进行逐步判别分析,有17种挥发性化合物进入判别函数,建立的两套判别函数都能准确判别火腿的加工程度.结果提示:金华火腿风味化合物是在加工过程中逐步形成的,在不同加工阶段,火腿特征风味化合物的含量及其比例各具特征,可以用以辨别火腿的加工时间.     

Application of a headspace sorptive extraction method for the analysis of volatile components in South African wines

A headspace sorptive extraction (HSSE) in combination with thermal desorption gas chromatography-mass spectrometry (TD-GC-MS) method for the analysis of volatile components (alcohols, esters, carbonyls, acids, phenols and lactones) in wine samples was developed. Extraction conditions such as salting-out effects, sorption time, stirring speed, phase ratio, extraction temperature, and effect of pH were thoroughly evaluated as part of method validation. The method was very sensitive with LODs and LOQs between 50 pg/L to 299 microg/L and 0.2 ng/L to 0.996 microg/L, respectively. Repeatability for all the compounds was between 3 and 22%. The intermediate repeatability was obtained within the acceptable range. Out of 39 volatile compounds selected, 37 were detected and quantitated. The method was found to be simple, cost-effective, sensitive, and use a small sample volume. The method was successfully applied for the routine analysis of 79 young red and white wine samples from various South African districts.     

番茄秸秆堆肥提高番茄果实风味的适宜添加比例研究

【目的】我国蔬菜生产面积大,食用部分收获后的蔬菜废弃物剩余量大,需要妥善处理。本文以番茄秸秆废弃物为原料进行堆肥,研究了其与菜园土混合作为基质用于番茄生产后,对番茄果实挥发性物质含量的影响,为番茄秸秆堆肥的科学应用提供依据。【方法】选用陕西地区的主栽番茄品种‘金棚1号’为试验材料,以常规基质 (氮磷钾总养分含量 ≥ 2%,有机质 ≥ 30%) 栽培为对照 (CK) 进行了盆栽试验,设置6个番茄秸秆堆肥与菜园土混配质量占比为0% (T1)、5% (T2)、7.5% (T3)、10% (T4)、12.5% (T5)、15% (T6)。在果实成熟期取样,利用顶空固相微萃取?气相色谱?质谱联用技术 (SPME-GC-MS) 测定番茄果实挥发性物质成分和含量。【结果】7个试验处理的番茄果实共检测出73种挥发性物质,包括9种酮类、25种醛类、19种醇类、5种酯类和4种烃类与11种其他未分类成分,施用堆肥的各处理挥发性物质种类与常规栽培相比差异较大,主要体现在醛类与醇类物质种类上;不同应用配比的堆肥产物对番茄果实挥发性物质含量影响不同,其总含量由高到低依次为T6 > T5 > CK > T4 > T2 > T3 > T1,整体随堆肥产物施用量的增高而增高,其中T5与T6处理的挥发性物质总含量分别较常规栽培番茄提高了81.0%与137%。被检测出的挥发性物质中包含11种番茄特征效应化合物,影响青香、果香与花香这3种类型的香气成分的总含量与挥发性物质总含量高低顺序一致,且T5与T6处理的番茄特征效应化合物总含量分别较常规栽培番茄提高了24.8%与72.2%;T5处理的番茄产量高于T6处理,且与对照无显著性差异。【结论】番茄秸秆经过堆腐处理后作为有机肥料用于番茄生产,不仅可实现番茄秸秆废弃物资源再利用,还可以有效改善番茄的风味品质,使果实香气丰富,果味浓郁。在本试验条件下,将12.5%的番茄秸秆堆肥产物与园土混配 (质量比) 时,番茄果实挥发性物质成分含量显著高于栽培基质对照,且产量与对照无显著差异,是较适宜的掺混比例。     

Infusion of volatile flavor compounds into low-density polyethylene

Supercritical fluids can extract components from some matrixes (e.g., fat and flavors from food) as well as infusing additives into synthetic polymer matrixes. To study the feasibility of infusing flavors into matrixes as a potential flavoring mechanism, a wide range of volatile flavor compounds was infused into a well-defined synthetic polymer (low-density polyethylene) using supercritical carbon dioxide. The polymer was then extracted, and the amount of infused compound was determined. The effects of time, temperature, pressure, rate of depressurization, volatile concentration, and volatile properties on the degree of infusion were studied. Infusion with supercritical carbon dioxide achieved much higher loadings of the polymer (0.01 to 6.87 mg/g LDPE, depending on the volatile molecule being infused) compared to those achieved by static diffusion. Forty-five volatiles were infused, from which a model was developed to predict infusion as a function of certain physicochemical properties.     

Rapid extraction and analysis of volatile fatty acids in soil

Abstract

The concentrations of volatile fatty acids (VFA) in soils are important in studies involving phytotoxicity and fermentation processes. Concentrations of acetic, propionic, and butyric acids as low as 0.21, 0.14, and 0.10 mmol kg^‐1soil in water extracts were accurately determined. The extracts were filtered through 45 μm millipore disc filters and injected directly into a gas chromatograph following addition of purified formic acid. The formic acid eliminated ghosting of peaks. The gas chromatograph was equipped with a flame ionization detector and a 60/80 Carbopack C/0.3% Carbowax 20M/0.1% H₃PO₄packed precolumn (0.15 m) and column (1.83 m). The precolumn was changed after 150 to 200 sample injections when contaminated beyond acceptable limits. There was good separation of VFA with no interfering organic volatiles in extracts of soil containing glucose, cellulose or straw incubated anaerobically for as long as 4 weeks. The advantages of the procedure are relative rapidity and simplicity as well as improved sensitivity in measuring small quantities of volatile fatty acids in soil     

Mixture approach for optimizing lycopene extraction from tomato and tomato products

A simple mixture process design based on the comparison of both quadratic and special cubic models and involving three mixture components (hexane/acetone/ethanol) as a solution for extracting lycopene from raw tomato, tomato sauce, and tomato paste was used to confirm the hypothesis that lycopene extraction rates are a function of the solvent used during the extraction process. Conventional criteria (p 相似文献   

Some unusual minor volatile components of tomato

The identities and possible origins of three minor unusual volatile components of tomato are discussed. These are pentyl nitrate, the first identification of a volatile alkyl nitrate in a fresh vegetable or fruit; 5-ethyl-2(5H)-furanone, which, besides its presence in tomato, was found to be a major autoxidation product of pure (Z)-3-hexenal; and 5-ethylcyclopentene-1-carbaldehyde, a likely unusual linolenic acid oxidation product.     

Sorption of volatile flavor compounds by microcellular cereal starch

Wheat starch based microcellular foam (MCF) forms of (dry) starch possess a significant percentage of micropores in the range of 5-14 A. The present study confirmed earlier preliminary studies that MCF starch (in a 0.25-1.0 mm diameter bead form) is effective in sorbing and lowering the headspace partial pressure of many volatile compounds in a manner similar (although less efficient) to that exhibited by other microcavity sorbants such as charcoal. It was found that the proportion of polar compounds sorbed was much greater than the proportion of nonpolar compounds. A major portion of the sorbed volatile compound was readily displaced from the MCF microcellular starch by the addition of water. These properties make this form of edible starch a potential useful carrier of flavor compounds for dried foods.     

Optimization of the analysis of flavor volatile compounds by liquid-liquid microextraction (LLME). Application to the aroma analysis of melons, peaches, grapes, strawberries, and tomatoes

A fast method based on liquid-liquid microextraction (LLME) has been developed for the analysis of volatile compounds in fruit and vegetable juices. The method was tested in an aqueous solution containing 49 common flavor compounds typically found in fruit aroma. Influence on extraction yield of the salts used, their levels, and the time of extraction was investigated. The efficiency of n-propyl gallate to inhibit the formation of secondary compounds from lipids during the crushing of fruit tissues was also tested. The proposed method was then applied to several authentic samples such as melons, peaches, grapes, strawberries, and tomatoes. The advantages and limitations of LLME are discussed.     

Effects of nitrogen application on flavor compounds of cherry tomato fruits

A pot experiment was conducted to determine the effects of N application on volatile compounds, taste compounds, and firmness of fresh tomato fruits. Each pot was filled with 8 kg of clean sand. The experiment consisted of six nitrogen (N)‐application rates with 0, 2.25, 4.50, 9.00, 18.00, and 36.00 mmol N L^–1 in the nutrient solution. Volatile compounds, soluble sugars, soluble solids, titratable acidity, and firmness of fresh tomato fruits were measured. The results show that increasing N application increased the concentrations of 1‐penten‐3‐one, hexanal, cis‐3‐hexenal, 2‐methyl‐4‐pentenal, trans‐2‐hexenal, 6‐methyl‐5‐hepten‐2‐one, titratable acidity, soluble sugars, and soluble solids. By contrast, increasing N supply decreased the concentration of phenylacetaldehyde and first increased and then decreased the concentrations of 2E–4E‐hexadienal and the firmness of fresh tomato fruits. Close relationships between the concentration of various volatile compounds, titratable acidity, soluble sugars, and soluble solids were found. However, concentrations of these flavor compounds were very poorly correlated with fruit firmness. Based on contributions of these compounds to tomato flavor, we assume that moderate high N supply improves tomato flavor, whereas excessive N supply can deteriorate it.     

鸡油组织中的磷脂对鸡油挥发性风味化合物形成的影响

磷脂是肉类特征性风味的重要前体物质。鸡油具有浓郁的脂香和鸡汤香气,磷脂可能对其风味有重要作用。该研究采用去除鸡油组织中的磷脂,以及在鸡油中添加磷脂等处理方法,结合顶空固相微萃取-气相色谱-质谱联用技术和感官评价方法研究经不同处理鸡油中的挥发性风味物质相对含量和风味的变化。结果表明添加了磷脂的鸡油,其特征性风味成分显著增加,特别是（E,E）-2,4-癸二烯醛和1-辛烯-3-酮分别增加了4.5倍和10.4倍;而去除磷脂鸡油的挥发性风味物质种类和丰度显著减少;感官评价结果也表明添加磷脂鸡油的风味最浓郁,而去除磷脂鸡油的风味最弱。因此,该研究证明鸡油组织中的磷脂对鸡油的风味具有重要的贡献作用,添加磷脂可显著增加鸡油的香气。该研究结果为浓香鸡油的开发提供理论依据和参考工艺。     

施用有机肥对番茄品质风味的影响

番茄的品质和风味是决定番茄口感的重要因素。以不施肥作为对照,在等氮投入条件下,分别以普通有机肥、沼渣及精制有机肥(中量)作为供试肥料,研究了有机肥对番茄品质和风味的影响,其中精制有机肥共设置了3个施肥水平(分别为19、38和57 t/hm~2的低、中和高量)。结果表明:施用有机肥后番茄产量增加了4.8%~14.4%,其中中量精制有机肥增产效果最好。施用有机肥尤其是中量精制有机肥可以显著增加番茄可溶性固形物、还原型维生素C、可溶性总糖等含量。番茄风味化合物主要以醛酮类、醇类及烷类为主。施用有机肥可以显著增加风味化合物的种类和数量,尤其是中量精制有机肥的施用,显著增加了番茄中醛酮类、酯类、酰肼、羟胺、有机酸等化合物。就番茄产量和品质而言,施用中量(38 t/hm~2)精制有机肥是最佳施肥方案。     

基于Niblack自适应修正系数的温室成熟番茄目标提取方法

番茄目标的准确提取是番茄采摘的基础,目前番茄目标提取方法都有一定的局限性,难以满足采摘需求。该研究在传统Niblack算法的基础上,结合图像全局灰度变化的估计信息与局部区域信息之间的关联性,提出了一种基于Niblack自适应修正系数的温室成熟番茄目标提取新方法。首先对R-G番茄灰度图像,采用基于自适应修正系数选取的Niblack算法进行阈值分割,从理论意义上确定修正系数的选取原则,归一化局部标准差,实现修正值的计算及二值化过程,然后对分割后的图像去噪,最后采用最小临界矩形法提取成熟番茄果实。试验结果表明,该方法对温室成熟番茄图像有较好的提取效果,识别正确率达到98.3%,与基于归一化红绿色差灰度化的Otsu算法和传统的Niblack算法相比有更高的识别率和更快的处理速度,噪声率也明显减少,能够满足后续成熟番茄定位的需要,有效地解决传统方法适应性低,易产生伪噪声块等问题。     

Effect of cultivar and storage time on the volatile flavor components of baked potato

Tubers of five cultivars of potato were stored at 4 degrees C for 2, 3, and 8 months and baked in a conventional oven. The flavor compounds from the baked potato flesh were isolated by headspace adsorption onto Tenax and analyzed by gas chromatography-mass spectrometry. On a quantitative basis, compounds derived from lipid and Maillard reaction/sugar degradation dominated the flavor isolates, with sulfur compounds, methoxypyrazines, and terpenes making smaller contributions. Levels of 37 of the >150 detected compounds were monitored in each cultivar with time of storage. Many significant differences were found in levels of individual compounds, compound classes, and total monitored compounds for the individual effects of cultivar and storage time and for their two-way interaction. Differences may be explained by variations in levels of flavor precursors and activities of enzymes mediating flavor compound formation among cultivars and storage times. In addition, differences in agronomic conditions may partly account for variations among cultivars. Overall, of the compounds monitored, those most likely having the greatest flavor impact were 2-isopropyl-3-methyoxypyrazine, 2-isobutyl-3-methoxypyrazine, dimethyl trisulfide, decanal, and 3-methylbutanal, with methylpropanal, 2-methylbutanal, methional, and nonanal also being probable important contributors to flavor.     

Supercritical fluid extraction of all-trans-lycopene from tomato

A procedure is proposed for the supercritical fluid extraction of all-trans-lycopene from tomato using carbon dioxide at 40 degrees C without modifier. The present method minimizes the risk of degradation via isomerization and oxidation of health-promoting ingredients, such as lycopene. The effect of different experimental variables on the solvating power of the supercritical fluid was evaluated in terms of both the selectivity achievable in the process and the yield of the extraction of all-trans-lycopene. Satisfactory separations of the all-trans-lycopene isomers from the cis counterparts were achieved using a C(30) column. The obtained extract contained 88% all-trans-lycopene and 12% cis-lycopene.     

杀菌方式对即食胡萝卜片挥发性风味物质的影响

为研究不同杀菌方式对即食胡萝卜片挥发性风味物质的影响,运用固相微萃取和气相色谱-质谱联用技术,分别对新鲜胡萝卜片和经巴氏杀菌、超高压杀菌、热辅助超高压杀菌处理的即食胡萝卜片及其贮藏期间(4℃,60 d)的挥发性组分进行对比分析。试验结果表明:新鲜胡萝卜片的主要芳香成分为萜烯类物质。与未杀菌组相比,经不同杀菌处理后,即食胡萝卜片的萜烯类物质含量均有所降低,其中巴氏杀菌组降低的最多。在贮藏前期(20~30 d),超高压处理即食胡萝卜片的萜烯类物质的含量最高,超高压杀菌在短期内较好地保持了胡萝卜特有的香气,即食胡萝卜片品质较好;其次是热辅助压力杀菌组,热辅助压力杀菌组即食胡萝卜片的β-蒎烯、β-石竹烯的含量较其他处理组较高,较好地保持了胡萝卜的松树树脂香气以及辛香气味;而巴氏杀菌组即食胡萝卜片的萜烯类物质含量最低,即食胡萝卜片的品质相对较差。研究结果可为新型杀菌技术在即食产品领域的应用提供参考。     

Effect of flavor compound chemical structure and environmental relative humidity on the binding of volatile flavor compounds to dehydrated soy protein isolates

Influence of flavor compound chemical structure, including functional group and stereochemistry, and environmental relative humidity (RH) on the binding of volatile flavor compounds to dehydrated soy protein isolates (SPIs) was evaluated by inverse gas chromatography. Binding of selected volatile flavor compounds differed slightly between SPIs of different origins. Results showed that the flavor compound chemical structure greatly determined its binding potential to SPIs. Binding of nonpolar flavor compounds (hydrocarbon) to soy proteins was attributed mainly to nonspecific van der Waals dispersion forces and was not affected by adsorbed water. The more polar flavor compounds (ester, ketone, aldehyde, and alcohol) exhibited both specific (hydrogen bonding, dipole forces) and nonspecific interactions, and their binding with soy proteins was greatly impaired by adsorbed water in the extremely low humidity region (approaching 0% RH). Further water uptake in the 30 to 50% RH region did not significantly affect the binding of polar compounds, although sorption of alcohol compounds (when present at high levels) further increased.     

超声辅助提取冻干番茄粉番茄红素的工艺优化

为了提高番茄原料中番茄红素的提取率,增加番茄深加工的利用价值,该文研究了冻干番茄粉粒度范围、液料比、超声温度、超声比功率和超声处理时间5个因素对番茄红素提取率的影响,通过响应面分析优化出超声辅助提取(ultrasound assisted extraction, UAE)冻干番茄粉(<74 μm)中番茄红素的最佳工艺,并与常规溶剂提取(conventional solvent extraction, CSE)进行了比较。确定的最优工艺条件为：液料比41:1 mL/g、超声温度55℃、超声比功率18 W/g,超声处理时间15 min。响应面验证试验番茄红素提取率为1.82±0.05 mg/g（超声时间10 min）,与优化模型预测值1.83 mg/g基本一致,验证了模型的可靠性。UAE的番茄红素提取率较CSE增加了6.04%,提取时间节省了92.47%。该文为番茄红素的高效提取及番茄的综合利用提供了参考。     

Analysis of volatile compounds and their contribution to flavor in cereals.

Recent developments in methods for isolation and measurement of volatiles from cereals are reviewed. The main types of isolation methods, namely, direct extraction, distillation, and headspace, have recently been complemented by solid phase microextraction. Direct solvent extraction provides efficient recovery of compounds with a broad range of polarities and volatilities, whereas headspace techniques provide relatively clean extracts. Supercritical fluid and solid phase microextractions have not yet been fully evaluated for cereals. GC and GC/MS remain the dominant techniques for measurement of the extracted compounds, although new electronic noses show promise. Relating these results to human perception requires careful control to ensure valid comparisons and, in this respect, aroma extract dilution analysis is a useful procedure.