Changes in volatile compounds upon aging and drying in oolong tea production

BACKGROUND: Long‐term storage (aging) with periodic drying of fresh oolong tea gives rise to so‐called old oolong tea. Alteration of aroma compounds is expected when a fresh oolong tea is converted into an old one, as the two teas smell drastically different. The aim of this study was to compare the volatile compounds in fresh and old oolong teas. RESULTS: Significant differences were observed between the volatile compounds in fresh and old oolong teas. This observation suggested that long straight chains of alcohols and acids were putatively decomposed while shorter‐chain acids, their amide derivatives and many nitrogen‐containing compounds were generated during the tea conversion processes. The overall patterns of volatile compounds observed in five different preparations of old oolong tea were fundamentally identical. This consensus pattern was different from that observed in oolong tea either stored for more than 10 years without drying or prepared at relatively low temperatures and short baking time. CONCLUSION: Characteristic aroma nitrogen‐containing compounds, including N‐ethylsuccinimide, 2‐acetylpyrrole, 2‐formylpyrrole and 3‐pyridinol, were consistently found in the examined old oolong teas. These compounds might be regarded as typical constituents at least for a certain kind of old oolong tea. Copyright © 2010 Society of Chemical Industry     

Spatial and temporal changes in the volatile profile of Alphonso mango upon exogenous ethylene treatment

Alphonso is a highly favoured and exported mango cultivar among the vast mango germplasm of India. Being a climacteric fruit, ethylene plays an important role in ripening of mango. For deeper understanding of effect of pre-climacteric ethylene treatment on volatile profiles of Alphonso mango, 26 volatiles were tracked through six ripening stages of pulp and skin of ethylene-treated and control Alphonso fruits. The study revealed accelerated ripening in terms of early appearance of ripening-specific compounds, lactones and mesifuran, upon ethylene treatment. While the level of lactones remained unaffected, the mesifuran level vastly increased upon ethylene treatment. Skin showed high terpene content while pulp had higher amount of lactones compared to skin. This work points towards involvement of ethylene as a natural hormone in the biosynthesis of lactones and furanones in naturally ripened fruits; whereas, an increase in the terpene level during ripening appears to be independent of ethylene.     

Changes in the volatile profile of skim milk powder prepared under different processing conditions and the effect on the volatile flavor profile of model white chocolate

The objective of this work is to determine the extent to which changes in the skim milk powder (SMP) manufacturing process alter the volatile profile of SMP, and whether these changes are carried through to a final product when the SMP is used as an ingredient and subjected to further processing. The manufacture of SMP is a multistage process involving a preliminary concentration step, heat treatment, and a drying stage. However, the methods and conditions used by the industry are not standardized, and the inherent variability in the production of SMP has consequences for the end-users, such as the confectionery industry, where the SMP is used as an ingredient during the production of milk chocolate, white chocolate, and caramel. This study investigates the effect of each stage of the manufacturing process on the concentration of reducing sugars and available amino groups (as precursors of the Maillard reaction) as well as on the volatile products of the Maillard reaction and lipid degradation. Eight types of SMP were produced using combinations of different processing conditions: concentration (by evaporation or reverse osmosis), heat treatment (low heat or high heat), and drying (spray-drying or freeze-drying). Maillard precursors were quantified after each processing stage and volatile compounds were extracted using solid-phase microextraction, and analyzed by gas chromatography-mass spectrometry. The resulting SMP were incorporated into a model white chocolate system, produced under varying conching conditions. We demonstrate not only that changes in the SMP manufacturing conditions affect the volatile profile of SMP, but also that these differences can be carried through to a final product when the SMP is used to prepare a model white chocolate. Understanding these differences is important to the industry for controlling the flavor of the end product.     

Changes in the profile of volatile compounds in wines stored under oxygen and their relationship with the browning process

 Eight young white wines produced in Aragon from Macabeo and Chardonnay grapes were stored under an oxygen atmosphere in the dark at room temperature. Changes in the colour and volatile compound composition were recorded over a period of 13 weeks. Significant changes in the volatile compound composition were detected through analysis of variance (ANOVA) of repeated measures, considering both grape variety and browning tendency as discriminant categories. The amounts of fatty acids and fermentation esters in the wine were significantly changed by the oxidative storage. Some of these changes can be attributed to acid-ester hydrolysis equilibria, but not others, such as the decrease in concentrations of octanoic and decanoic acids. The oxidative storage also affected most of the unsaturated fatty-acid-derived compounds: trans-2-octenal, trans-2-nonenal, trans-2-decenal and 1-octen-3-ol were all found to increase in the first stages of storage, while hexanol decreased slightly. Volatile phenols behaved very differently: while phenol and 4-ethylphenol initially increased and later decreased, eugenol increased through the process and 4-vinyl-guaiacol disappeared. Benzaldehyde and furfural increased while methionol and terpenols disappeared. Only furfural was found to be linked with the tendency of the wine to brown, while only linalool and benzaldehyde were found to be linked whith the grape variety. The levels of some odorants previously isolated by sniffing detection were temptatively monitored, and significant changes in their concentrations were found to occur during the process. Received: 16 December 1996 / Revised version: 27 March 1997     

Changes in the profile of volatile compounds in wines stored under oxygen and their relationship with the browning process

 Eight young white wines produced in Aragon from Macabeo and Chardonnay grapes were stored under an oxygen atmosphere in the dark at room temperature. Changes in the colour and volatile compound composition were recorded over a period of 13 weeks. Significant changes in the volatile compound composition were detected through analysis of variance (ANOVA) of repeated measures, considering both grape variety and browning tendency as discriminant categories. The amounts of fatty acids and fermentation esters in the wine were significantly changed by the oxidative storage. Some of these changes can be attributed to acid-ester hydrolysis equilibria, but not others, such as the decrease in concentrations of octanoic and decanoic acids. The oxidative storage also affected most of the unsaturated fatty-acid-derived compounds: trans-2-octenal, trans-2-nonenal, trans-2-decenal and 1-octen-3-ol were all found to increase in the first stages of storage, while hexanol decreased slightly. Volatile phenols behaved very differently: while phenol and 4-ethylphenol initially increased and later decreased, eugenol increased through the process and 4-vinyl-guaiacol disappeared. Benzaldehyde and furfural increased while methionol and terpenols disappeared. Only furfural was found to be linked with the tendency of the wine to brown, while only linalool and benzaldehyde were found to be linked whith the grape variety. The levels of some odorants previously isolated by sniffing detection were temptatively monitored, and significant changes in their concentrations were found to occur during the process. Received: 16 December 1996 / Revised version: 27 March 1997     

Changes in the profile of volatile compounds and amino acids during cider fermentation using dessert variety of apples

In China, the production of apples is very large even surplus. Developing cider is becoming an important and promising segment of the fruit industry. Fuji apples, a most popular dessert variety in China, were employed to produce cider. Timely monitoring during the fermentation process was conducted by recording the changes in yeast biomass, total sugar content, reducing sugar content, total acidity, yeast assimilable nitrogen, total phenols content, amino acids and volatile compounds. The sugar and nitrogen compounds were consumed smoothly during fermentation. A variety of volatile compounds were detected in the fermentation liquor, mainly including eight higher alcohols, fourteen esters, six fatty acids, three aldehydes, one ketone, one volatile phenol and three terpenes. Their content was changing dynamically throughout the fermentation process. The sensory evaluation revealed a good acceptance of the cider. The results showed that Fuji apples are good raw material for cider and have the potential to be widely used in the China cider industry.     

即墨黄酒煮糜工艺对挥发性物质的影响

采用溶剂辅助风味蒸发(solvent assisted flavor evaporation,SAFE)和顶空固相微萃取法(headspace solid-phase microextraction arrow,HS-SPME-ARROW)结合全二维气相色谱-飞行时间质谱技术(comprehensive two di-...     

Changes in volatile compounds and related biochemical profile during controlled fermentation of cv. Conservolea green olives

The effect of controlled fermentation processes on the profile of volatile and other biochemical compounds of cv. Conservolea green olives processed by the Spanish method was studied. The different treatments included: (a) inoculation with a commercial starter culture of Lactobacillus pentosus, (b) inoculation with a wild strain of Lactobacillus plantarum isolated from a previous fermentation, (c) uninoculated spontaneous process (control). Microbial growth, pH, titratable acidity, reducing sugars, organic acids and volatile compounds were monitored. Starter cultures were effective in establishing an accelerated fermentation process. Both were able to reduce the survival period of Enterobacteria by 7 days, minimizing thus the likelihood of spoilage. Higher acidification of the brines and faster pH drop was observed in inoculated processes, with L. pentosus presenting better performance than the wild strain of L. plantarum. Lactic and acetic were the major organic acids detected by HPLC, the concentration of which increased in the course of fermentation. Citric and malic acids were also present in the brines but they were degraded completely within the first 2 weeks of fermentation. Ethanol, methanol, acetaldehyde, ethyl acetate, isobutyric acid were the major volatile compounds identified by GC. Their concentration varied greatly among the fermentation processes, reflecting varying degrees of microbial activity in the brines.     

不同熬煮工艺对牛杂汤挥发性风味物质的影响

采用顶空固相微萃取-气质联用技术(HS-SPME-GC/MS)和感官评定方法鉴定了商业牛杂汤的主要风味化合物,在此基础上优化了自制牛杂汤配方,并研究了不同熬煮时间和熬煮方式对牛杂汤风味物质的影响。结果表明:商业牛杂汤最主要的挥发性风味化合物有26种,包括醛类、萜烯类、醇类、酮类及其他化合物等种类。熬煮时间对牛杂汤风味有较大影响,1~3 h内延长熬煮时间会促进牛杂汤中挥发性成分的充分释放,但超过3 h汤中风味物质含量显著减少,牛杂汤的最适合熬煮时间为3 h;常规熬煮、开盖熬煮和高压熬煮的牛杂汤中分别检测出28、32、37种风味化合物,但高压熬煮汤的香味显著弱于常规和开盖熬煮,这可能是由于高压熬煮中脂肪氧化所产生的己醛、辛醛含量较低所致。     

一种萃取酒醅中低沸点挥发性成分的方法

分别采用水蒸汽蒸馏（SD）法、超声辅助溶剂萃取（UASE）法和蒸馏-微溶剂萃取（SD-MSE）法从浓香型白酒酒醅中提取挥发性成分,利用峰面积归一化法测定各成分的相对含量,通过对挥发性成分的气相色谱-质谱连用/自动化退卷积系统（GC-MS/AMDIS）对比分析。结果表明,SD、UASE及SD-MSE法分别鉴定出42种、71种、60种挥发性成分。SD、UASE及SD-MSE法分别测得的醇、酸、酯的相对含量分别为1.34%、6.61%、21.67%;1.03%、39.28%、37.42%;3.96%、9.97%、64.97%。由此可知,SD法对酸、酯的提取效果劣于另两种方法,UASE法对酸类物质萃取效果更佳,SD-MSE法对酯类物质的萃取效果更佳。和UASE法相比,SD-MSE法节约了大量溶剂,减少了样品转移次数,且待测液澄清透明,是一种适宜萃取糟醅中低沸点成分的方法。     

Contribution of enterococci to the volatile profile of slightly-fermented sausages

The volatile profiles of slightly-fermented sausages inoculated with eight different enterococci strains were determined and compared with a fermented sausage manufactured without any inoculation. The volatile profile was determined by solid-phase microextraction (SPME) and gas chromatography coupled to mass spectrometry (GC/MS). A total of 121 volatile and semi-volatile compounds were identified in the samples of the final products (day 21). Terpenes from spices added during manufacture of dry-fermented sausages were the main group of compounds in the volatile profile. Other groups included alcohols (18% of total volatile compounds), aldehydes (16%), alkanes and alkenes (12%), and ketones (10%). These are derived from lipids, proteins or carbohydrates and formed during fermentation and ripening. In terms of global volatile composition, the batches inoculated with enterococci strains were similar to those obtained for non-inoculated batch. However, some quantitative differences in the volatile profiles of different batches were found, mainly in the compounds formed from amino acid catabolism (i.e.: propanol, isoamyl), from free fatty acid oxidation (i.e.: hexanal, hexanol), or from carbohydrate fermentation (i.e.: 2-butanone, acetoin). In comparison with non-inoculated sausages, some batches were more resistant to oxidation; they contained fewer volatile compounds arising from lipid oxidation. The use of different selected enterococci strains did not alter the volatile profile of slightly-fermented sausages. The enterococci strains provide similar volatile compounds to those usually reported in the literature.     

解百纳葡萄洒在橡木桶贮存中的挥发酸

挥发酸主要由两部分组成:一部分是由酒精发酵而生成的(正常);另一部分是由细菌寄生产生的(异常),其合值一般应在0.4～0.6g/L之间.     

Analysis of the volatile profile and identification of odour-active compounds in Bayonne ham

The aim of this work was to reliably identify odour-active compounds in dry-cured ham using powerful analysis methods for the volatile fraction. For this purpose, dynamic headspace gas chromatography combined with eight-way olfactometry using a panel of eight sniffers was used. One- and two-dimensional gas chromatography coupled with mass spectrometry and (or) olfactometry were also used. More than 600 compounds from the volatile fraction of dry-cured ham were identified and their biochemical origins are discussed. They covered a wide diversity of structures and chemical functions. Only 29 of them proved odour-active. Comparison of the results of GC–O analysis with those obtained by orthonasal sniffing of the dry-cured ham helped to gain a better understanding of how these substances contributed to the overall aroma of the product. Thus, “Fruity–Floral”, “Green–Vegetable” or “Plastic–Chemical” odours intensively perceived by GC–O have been poorly perceived by orthonasal sniffing. By contrast, “Animal–Meat products” or “Butter–Lactic–Cheesy” odours have been much better perceived by orthonasal sniffing. These results indicate that to understand the interactions between odour-active compounds, experimental doping with carefully selected odour-active compounds will be necessary.     

Changes in volatile flavour components of soybeans during roasting

Volatile concentrates were prepared from whole soybeans, roasted at 200°C for 10, 20 and 30 min, by steam distillation under reduced pressure followed by ether extraction, and analysed by gas chromatography and gas chromatography-mass spectrometry, in comparison with the volatile concentrate from raw soybean flour.Major flavour components of raw soybean, such as n-hexanol, 1-octen-3-ol and n-hexanal, decreased during the course of roasting, but the rate of this decrease was not rapid, especially between 10 and 20 minutes' roasting. During the roasting period, alkylated pyrazines, oxygenated furans, oxygenated pyrroles and phenols were formed or increased markedly. On the other hand, sensory evaluation showed that a flavour change to ‘desirable’ from ‘beany’ or ‘objectionable’ occurred between 10 and 20 minutes' roasting. These results suggest that roast flavour masks the ‘beany’ flavour in soybean.     

Changes in volatile compounds of Parma ham during maturation

Changes in the aromatic profile of Parma ham caused by the normal course of aging up to 12 months were examined in order to identify distinctive signals for different maturing periods (6, 9, 12 months).

The 28 samples analysed, divided among the three periods mentioned above, provided an aromatic profile in which methyl esters were the most relevant signals, followed by carbonyl compounds and alcohols.

The greatest discriminating power is to be ascribed to components such as 3-methylbutanal and ethyl esters, and alcohols like 1-propanol, 1-butoxy-2-propanol and 2-butanol.

These compounds were present in higher percentages at 12 months of aging.     

甬优15在储藏期间挥发性成分的变化

通过HS-SPME/GC-MS技术,对不同含水量以及储藏时间的甬优15优质稻的挥发性成分进行分析,结果表明:随着储藏时间的延长,烯烃类、醇类、醛类物质的含量呈上升趋势,酮类和酯类变化不明显,烷烃类和酸类呈下降趋势。含水量14.5%的甬优15的清香物质含量高于13.1%和13.8%含水量的甬优15;当储藏180 d时,很多清香物质的含量达到峰值,继续储藏清香物质含量降低,储藏效果变差。1-壬醇随着储藏时间延长呈上升趋势,可作为甬优15储藏时间延长的醇类标志物;邻苯二甲酸二异丁酯的含量随着储藏时间的延长先下降后上升再下降,可作为甬优15的酯类标志物;反式-2-壬烯醛的含量随着储藏时间先上升后降低,且含水量越高,其含量越高,可作为甬优15的醛类标志物。关键字     

泡菜发酵过程挥发性风味成分的变化

采用SPME–GC–MS对泡菜在发酵过程中不同时期的挥发性风味进行分析。结果表明:泡菜的最佳食用期为48 h,不同时期的泡菜的挥发性成分差异明显;共鉴定出化合物111种,包括醇类、烃类、含硫化合物、酯类、醛类、酮类、酸类等。泡菜在发酵期间,酸类、醇类、含硫化合物的含量不断增长;在发酵后期,烃类、醛类、酮类化合物的含量不断下降。含硫化合物和醇类对泡萝卜的风味形成有较大贡献。