ACTIVITY COEFFICIENTS of AROMA COMPOUNDS and WATER ACTIVITY IN MODEL SYSTEMS

One aim of this work was to measure the activity of water and aroma compounds in aqueous solutions simultaneously. The volatilities of aroma substances at infinite dilution in aqueous solutions of polyethylene-glycols (PEG) were studied. the activity coefficients (γi^∞) of volatile compounds were measured by gas stripping (exponential dilution). This dynamic method also allowed the measurement of the water activity of these solutions. the results showed that:

• 1 the influence of polyethylene-glycols on γi^∞ depended most strongly on the PEG mass fraction in the solution. the effect of the PEG molecular weight was not significant.
• 2 γi^∞ increased as molecular weight and length increased for the homologous series of alcohols tested. This can be explained by entropic effects. Probably, the same effect occurs for other homologous series.
• 3 γi^∞ for 2-propanone increased as temperature increased. Based on this relation, molar partial excess enthalpies of mixing were calculated for 2-propanone in an aqueous solution.

     

清香型志都五谷酒关键香气成分分析

通过液液萃取和顶空固相微萃取技术,结合气相色谱-质谱-嗅闻联用仪分析一种清香型志都五谷酒香气活性成分.通过香气提取稀释分析法共得到40种香气物质,且香气稀释(flavor dilution,FD)因子最大的为异丁酸、月桂酸乙酯、愈创木酚和2-苯乙醇(FD＞4 096),通过质谱、保留指数、香气特征和标准品比对共定性出3...     

当归中关键气味活性化合物的鉴定及其在煎煮过程中变化规律研究

通过溶剂辅助风味蒸发制样（SAFE）和动态顶空制样（DHS）与气相色谱-嗅闻仪-质谱联机法（GC-O-MS）结合,对当归药材中的主要气味活性化合物进行分析,最终分别鉴定出43种和47种气味活性化合物。此外,采用香气提取物稀释分析（AEDA）和动态顶空稀释分析（DHDA）共同确定了贡献度较大的6种关键气味活性化合物:6-十一酮（泥土味、中药味）、藁本内酯（药草味）、丁烯基苯酞（药草味）、己醛（青草味）、辛醛（清香）和2-甲氧基-4-乙烯基苯酚（咖喱味）。最后,采用固相微萃取法（SPME）提取当归煎煮液的挥发性成分,并以内标法对关键气味活性化合物进行定量分析。结果表明:上述6种关键气味化合物在煎煮过程中含量发生改变,致使煎煮液清新香韵先增强后减弱,泥土香韵强度减弱,药草和咖喱香韵整体增强。      

红茶特征香气成分的鉴定及感知交互作用

对红茶的特征香气挥发性化合物进行鉴定,之后对红茶的香气轮廓进行深入剖析,继而对重要特征化合物进行香气感知交互作用的探索,在此基础上进行修正矢量模型以及Steven定律在此体系上的应用。以顶空固相微萃取和溶剂辅助蒸发萃取结合气相色谱-嗅闻技术对化合物的香气进行评估,得到了51种较为特征的香气化合物,红茶最主要的香气物质是醇类和醛类,其中香气提取物稀释分析以及香气强度记录结果显示了芳樟醇、苯乙醇、(Z)-3-己烯醇、香叶醇以及水杨酸甲酯等化合物具有较高的香气贡献。通过偏最小二乘法关联化合物与香气特征,基于灰色关联度法将电子鼻传感器与香气轮廓进行匹配,以达到全面剖析红茶香气的目的,继而利用Feller加和模型进行香气感知交互作用的分析,在此基础上探索了修正矢量模型以及Steven定律在此体系上的应用,10组二元化合物中有8组表现了掩盖作用,2组表现为协同作用。通过以上实验可以达到为红茶重要风味物质研究提供参考的目的。     

Characterization of the key aroma compounds in beef extract using aroma extract dilution analysis

Aroma extract dilution analysis (AEDA) of an ether extract prepared from beef extract (BE) and subsequent identification experiments led to the determination of seven aroma-active compounds in the flavor dilution (FD) factor range of 32–128. Omission experiments to select the most aroma-active compounds from the seven aroma compounds suggested that 2,3,5-trimethyl pyrazine, 1-octen-3-ol, 3-methylbutanoic acid, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone were the main active compounds contributing to the aroma of BE. Aroma recombination, addition, and omission experiments of the four aroma compounds in taste-reconstituted BE showed that each compound had an individual aroma profile. A comparison of the overall aroma between this recombination mixture and BE showed a high similarity, suggesting that the key aroma compounds had been identified successfully.     

Recovery of volatile fruit juice aroma compounds by membrane technology: Sweeping gas versus vacuum membrane distillation

The influence of temperature (10–45 °C), feed flow rate (300–500 L/h) and sweeping gas flow rate (1.2–2 m³/h) on the recovery of berry fruit juice aroma compounds by sweeping gas membrane distillation (SGMD) was examined on an aroma model solution and on black currant juice in a lab scale membrane distillation set up. The data were compared to recovery of the aroma compounds by vacuum membrane distillation (VMD). The flux of SGMD increased with an increase in temperature, feed flow rate or sweeping gas flow rate. Increased temperature and feed flow rate also increased the concentration factors (C_permeate/C_feed) of the aroma compounds. At 45 °C the most volatile and hydrophobic aroma compounds obtained the highest concentration factors: 12.1–9.3 (black currant juice) and 17.2–12.8 (model solution). With black currant juice a volume reduction of 13.7% (vol.%) at 45 °C, 400 L/h, resulted in an aroma recovery of 73–84 vol.% for the most volatile compounds. Compared to VMD, the aroma recovery with SGMD was less influenced by the feed flow rate but more influenced by the temperature. Higher fluxes were achieved during concentration by VMD and this reduced the operation time, which in turn reduced the degradation of anthocyanins and polyphenolic compounds in the juice.

Industrial relevance

High temperature evaporation is the most widely used industrial technique for aroma recovery and concentration of juices, but membrane distillation (MD) may provide for gentler aroma stripping and lower energy consumption. This study gives important clues about the fate of berry juice aroma compounds and polyphenols during concentration by MD, and identifies the main factors influencing the aroma recovery efficiency with MD. Both SGMD and VMD are promising techniques for gentle stripping of berry juice aroma compounds and deserve further consideration as alternative techniques for gentle aroma stripping in industrial fruit juice processing.     

3种不同年份五粮液酒的关键香气成分分析

以1、15 a和30 a 3种不同年份五粮液酒为研究对象,采用顶空固相微萃取、气相色谱-嗅闻-香气稀释分析结合气相色谱-质谱对五粮液的香气成分进行研究。在3种五粮液酒中共鉴定出30种香气物质,包括酯类18种、醇类2种、酸类5种、醛类5种,其中有9种物质在3种五粮液酒中的香气稀释值均不小于256,被认为是关键香气成分。定量结果表明,五粮液酒中的香气物质总含量随着时间的延长而下降。同时,对3种不同年份五粮液酒进行感官分析。方差分析表明,3个酒样的7个感官属性均有显著性差异(P0.05),Duncan’s多重比较表明,陈香、花香、甜香、焦糖香和粮食香区别最明显。     

Key aroma compounds identified in Cheddar cheese with different ripening times by aroma extract dilution analysis,odor activity value,aroma recombination,and omission

To determine the odor-active compounds in Cheddar cheeses with different ripening times (6, 10, and 14 mo), 39 potent odorants of Cheddar cheeses were identified with a flavor dilution factor range between 1 and 512 by aroma extract dilution analysis. To further determine their contribution to the overall aroma profile of Cheddar cheeses, odor activity values of 38 odorants with flavor dilution factors ≥1 were calculated. A Cheddar cheese matrix was developed to determine the concentrations and the odor thresholds of these key aroma compounds. The result of the aroma recombinant experiment prepared by mixing the key aroma compounds in the concentrations in which they occurred in Cheddar cheeses showed that the overall aroma profile of the recombinant sample was very similar to that of Cheddar cheese. The main different compounds in Cheddar cheese with different ripening time were acetic acid, butanoic acid, dimethyl trisulfide, methional, hexanal, (E)-2-nonenal, acetoin, 1-octen-3-one, δ-dodecalactone, furaneol, hexanoic acid, heptanal, and ethyl caproate. This study could provide important information for researching and developing Cheddar cheese–related products.     

热反应猪肉香精的制备及其气味活性化合物的鉴定

以猪肉蛋白酶解液为基础,与氨基酸、还原糖等物质进行Maillard反应制备猪肉香精,同时通过正交试验和专业评香员的评比,得猪肉香精的最佳配方及条件为：木瓜蛋白酶:肽酶R(Peptidase R)=5:1、加酶量0.3%、底物浓度100%、酶解温度55℃、酶解时间6h、酶解液添加量100.0g、酵母提取物20g、葡萄糖10g、VB1 2g、甘氨酸7g、丙氨酸5g、精氨酸2g、脯氨酸5g、天门冬氨酸5g、半胱氨酸(盐酸盐)9g、呈味核甘酸二钠(IMP 50%+GMP 50%)1.5g、味精4g、木糖1.5g、食盐1.5g、水25g、氧化油脂5g,反应温度125℃,反应时间60min。然后利用两种前处理技术即同时蒸馏提取(simultaneous steam distillation/extraction,SDE)和动态顶空制样(dynamic headspace sampling,DHS)提取猪肉香精的香味成分,采用国内先进的香味分析技术气相色谱-吸闻(gas chromatography-olfactometry,GC-O)技术和质谱(mass spectrometry,MS)技术进行检测分析。同时,采用稀释技术香味提取物稀释分析(aroma extract dilution analysis,AEDA)、动态顶空稀释分析(dynamic headspace dilution analysiis,DHDA)筛选其关键芳香化合物。结果,用同时蒸馏提取物-吸闻-质谱(SDE-GC-O-MS)的方法共检测到30种香味活性化合物,用 动态顶空制样-吸闻-质谱(DHS-GC-O-MS)的方法共检测到40种香味活性化合物,其中两种方法中都被检测到的香味活性化合物有24种。2-戊基呋喃、己醛、1-辛烯-3-醇具有最高的FD因子,这3种化合物在相关猪肉香气的文献报道中也被鉴定出来,是该猪肉香精中对整体香味作出重要贡献的关键芳香活性化合物。     

传统小麦酱挥发性香气成分的GC-MS与GC-O分析

采用同时蒸馏萃取法提取传统小麦酱中的挥发性成分,以气-质联用结合气相色谱-嗅闻技术,对传统小麦酱中的活性香气成分进行分离鉴定。结果共鉴定出42种挥发性化合物,占色谱流出组分总量的72.835%,在传统小麦酱中的含量为102.845μg/g,包括醛类6种、酯类10种、酸类6种、烃类8种、醇类1种、杂环类化合物7种、酮类1种,其他化合物3种。用气相色谱-嗅闻技术分离出25种活性香气成分,其中芳香萃取物稀释分析稀释因子较高的有乙酸、异戊醛、糠醛、3-甲硫基丙醛、二甲基三硫醚、1-辛烯-3-醇和四甲基吡嗪等。     

Identification of Predominant Aroma Compounds in Muscadine Grape Juice

The aroma components of muscadine (Vitis rotundifolia Michx) grape juice were analyzed by gas chromatography (GC)/mass spectrometry and GC/olfactometry (aroma extract dilution analysis). 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (furaneol), with a burnt sugar-like aroma, was the most intense aroma in the juice. Other predominant compounds included 2,3-butanedione, ethyl butanoate, ethyl 2-methylbutanoate, 2-phenylethanol, and o-aminoacetophenone. These compounds were described as buttery/cream cheese, bubble gum/fruity, green apple/fruity, rosy, and foxy, respectively. Furaneol and o-aminoacetophenone were thought to be responsible for characteristic candy and foxy-like aroma notes of muscadine grape juice. Flavor dilution chromatograms were similar for juices prepared from grapes harvested on different dates and from different locations.     

Static Headspace and Aroma Extract Dilution Analysis of Parmigiano Reggiano Cheese

ABSTRACT The aroma compounds in Parmigiano Reggiano cheese were studied with Aroma Extract Dilution Analysis (AEDA). Both static headspace and solvent extraction, high-vacuum distillation techniques were used to isolate aroma compounds. Thirty-six odor-active compounds had high flavor dilution values. Static headspace gas chromatography/olfactometry (GC/O) analysis found that acetaldehyde, 2-methylpropanal, 2-methylbutanal, 3-methylbutanal, ethyl butanoaic, and ethyl hexanoate had low detection volumes, while high-vacuum distillation revealed that acetic, butanoic, hexanoic, octanoic, and decanoic acids, and ethyl butanoate, ethyl hexanoate, dimethyl trisulfide, methional, and phenylacetaldehyde had high flavor dilution values. In addition, some pyrazines appear to be important to the aroma of this cheese.     

Comparison of two sample preparation techniques for sniffing experiments with broccoli (Brassica oleracea var. italica Plenck)

The suitability of the headspace solid phase microextraction (HS-SPME) for gas chromatography-olfactometry (GC-O) with aroma extract dilution analysis in comparison to the dynamic head space sampling on a Tenax trap was tested exemplarily by the aroma volatiles of fresh broccoli. A high number of odour sensations in qualitative olfactometry was registered with both sample preparation techniques. The key aroma compounds of the fresh broccoli material are represented by high flavour dilution factors with dynamic head space sampling and headspace SPME. The SPME method has found to be a convenient and fast technique suitable especially for qualitative GC-O. The adsorption selectivity of the fiber and the substance discrimination have to be taken into account for quantitative use like aroma extract dilution analysis     

现代工艺和传统工艺酿造小曲清香型白酒感官表征及风味成分分析

运用感官分析、气相色谱-嗅闻-质谱技术、顶空固相微萃取-气相色谱-质谱联用技术,研究现代工艺和传统工艺酿造而成的小曲清香型白酒的主要香气轮廓及风味成分。采用保留指数结合标准品比对法分别从现代工艺和传统工艺小曲清香型白酒中鉴定出116 种和121 种挥发性成分;并进一步通过芳香萃取物稀释分析法从现代工艺和传统工艺小曲清香型白酒中筛选出49 种挥发物（稀释因子≥2）。通过计算香气活度值,在现代工艺小曲清香型白酒中鉴定出33 种风味活性物质,在传统工艺小曲清香型白酒中鉴定出34 种风味活性物质。分别依据两种工艺小曲清香型白酒的定量结果进行香气重组实验,得到的模拟液与两种工艺小曲清香型白酒香气较为接近,并通过化合物遗漏实验,表明现代工艺小曲清香型白酒重要的风味物质包括辛酸乙酯、乙醛、乙酸异戊酯、1,1-二乙氧基乙烷、己酸乙酯、戊酸、1-辛烯-3-醇、乙酸乙酯、异丁醇、异戊酸乙酯等物质;传统工艺小曲清香型白酒重要的风味物质包括辛酸乙酯、己酸乙酯、戊酸乙酯、丁酸乙酯、乙醛、乙酸异戊酯、戊酸、1,1-二乙氧基乙烷、异丁醇、乙酸乙酯、正丙醇、1-辛烯-3-醇等物质。两种工艺酿造的小曲清香型白酒在主要风味物质种类上差异较小,但是呈香强度和香气活度值存在较大的区别,导致两种工艺小曲清香型白酒在感官评价和风味特征上存在显著差异。     

Determination of the key aroma compounds in Sachima and using solid phase micro extraction (SPME) and solvent-assisted flavour evaporation (SAFE)-gas chromatography-olfactometry-mass spectrometry (GC-O-MS)

The aroma-active compounds present in Sachima samples purchased at retail from the same batch code and stored for different durations of the shelf life were analysed by two methods: solid phase micro extraction (SPME) and solvent-assisted flavour evaporation (SAFE)-gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 41 volatile key compounds were identified. Among them, the predominant compounds in Sachima were tentatively identified by dilution analysis as being 3-(methylthio)propionaldehyde, 2-pentylfuran, 2-methyl-3-(methylthio)pyrazine, dimethyl disulfide, and dipropyl trisulfide. These compounds produced the highest due to their highest calculated flavour dilution (FD) factors. Sensory evaluations of the extracted compounds by a panel of trained individuals revealed that the ‘egg’ aroma was the main characteristic aroma due to its high sensory assessment score. With increasing length of storage of the product from 0 to 10 months, the overall acceptability of the Sachima aroma declined gradually. The observed changes in concentration of the different volatile compounds during storage indicated that the Maillard reaction and lipid oxidation continued during storage, so that aroma compounds and off-flavour compounds were being generated simultaneously. In addition, the undesirable smell of Sachima that increased during storage was not just generated from one volatile compound with a distinct off-flavour, but rather it was the result of an increase in both pleasant and unpleasant aromas. Furthermore, the pleasant aroma components appeared to still play a dominant role in the overall aroma profile of Sachima even after 10 Months of storage, which is within the stated shelf life on the product label.     

Analysis and characterization of aroma‐active compounds of Schizandra chinensis (omija) leaves

Volatile components from leaves of Schizandra chinensis (omija), a native plant of Korea, were extracted by simultaneous distillation–extraction (SDE) and analyzed by gas chromatography–mass spectrometry (GC‐MS) using two types of capillary column with different polarities (DB‐5MS and DB‐Wax). The GC‐MS analysis of volatile compounds obtained by SDE revealed that germacrene D is the most abundant compound (22.6%) in omija leaves, followed by β‐elemene (17.4%), (E)‐2‐hexenal (8.7%), and (E)‐β‐ocimene (7.2%). Aroma‐active compounds were determined by gas chromatography–olfactometry (GC‐O) using the aroma‐extract‐dilution analysis method. (E,Z)‐2,6‐Nonadienal (cucumber) was the most intense aroma‐active compound due to its higher flavor‐dilution factor (243–729) than any other compound. (Z)‐3‐Hexenal (green/apple), (E)‐2‐hexenal (green/fruity), and (E)‐β‐ocimene (wither green/grass) were also identified as important aroma‐active compounds by GC‐O. In addition, the volatile compounds were extracted by solid‐phase microextraction (SPME), and the quantitative analysis of the SPME samples gave slightly different results, depending on the type of SPME fiber, compared with those from SDE, However, the aroma‐active compounds identified in SPME were similar to those in SDE. Copyright © 2004 Society of Chemical Industry     

GC-O-MS法鉴定黑巧克力中关键香气物质

采用同时蒸馏萃取法(SDE)和吹扫捕集法(P&T)对醇浓黑巧克力中挥发性物质进行提取。利用气相色谱-嗅闻-质谱联用的方法对其中的挥发性性物质定性分析,共鉴定出52种物质,包括醛类、烯醛类、吡嗪类、醇类、酯类、酮类、呋喃类、酸类等物质,其中吡嗪类物质的种类最多,其次为醛类物质。通过香气提取物稀释分析(AEDA)和动态顶空稀释分析(DHDA),确定关键的香气物质(log3FD≥4/FD值≥125)共有10种,分别为醛4种(2-甲基丙醛、3-甲基丁醛、2-甲基丁醛、苯乙醛),吡嗪4种(乙基吡嗪、2,3-二甲基吡嗪、三甲基吡嗪、四甲基吡嗪),酯1种(苯甲酸异戊酯),吡咯1种(2-乙酰基-1-吡咯啉)。其中巧克力香气特征主要表现为黑巧克力香、爆米花味、烤香、水果香、咖啡香、坚果香等。     

2种芝麻香型白酒中香气活性成分分析

应用液液萃取法结合气相色谱-质谱-嗅闻联用仪分析2 种芝麻香型白酒（BTQ、YH）中香气活性成分。经保留指数、香气特征并结合标准品比对,BTQ和YH分别定性出挥发性化合物75 种和68 种;结合气相色谱-质谱-嗅闻联用通过芳香萃取物稀释分析分别嗅闻出香气活性化合物48 种和46 种,BTQ中香气稀释（flavor dilution,FD）因子值最大的是3-甲硫基丙醛（FD=6 561）;YH中FD最大的是苯乙醇、3-甲基-1-丁醇、丁酸乙酯、戊酸乙酯（FD=2 187）。通过多种方法联用,对嗅闻到的51 种香气活性成分和28 种非嗅闻活性成分进行定量分析,并结合相关阈值进行香气活性值（odor activity value,OAV）分析,比较它们对整体香气的贡献程度,发现BTQ中有40 种化合物OAV不小于1,YH中有36 种化合物OAV不小于1,2 种酒中香气贡献度最高的是己酸乙酯、3-甲基丁醛、丁酸乙酯、3-甲基丁酸乙酯。结合FD因子及OAV,对这2 种芝麻香型白酒香气有重要贡献的化合物有己酸乙酯、丁酸乙酯和3-甲基丁醛。     

EFFECT OF COOKING METHOD ON THE AROMA CONSTITUENTS OF SWEET POTATOES [IPOMOEA BATATAS (L.) LAM.]

To better understand the factors controlling the flavor of horticultural products, the effect of method of cooking on the volatile flavor of sweet potatoes was assessed. Volatile extracts from sweet potatoes cooked by baking, boiling, and microwaving were studied by GC, GC‐MS and GC olfactory assessment. GC‐olfactory analysis identified 37 compounds that were odor‐active, 36 of which were identified. Compared with conventional baking, boiling and microwaving yielded only 54.26% and 6.43% of the relative total yield of aroma‐active compounds, respectively. From aroma extract dilution analysis, four compounds contributed to the aroma from each cooking method. In addition, cooking method specific aroma contributing compounds accounted for the unique aroma of each of the cooked products. Thus the flavor of cooked sweet potatoes is dependent upon the method of cooking both on a sensory and chemical level.