Effect of oak extract application to Verdejo grapevines on grape and wine aroma

Volatile compounds from a commercial aqueous oak extract application to white Verdejo grapevines at veraison have been studied. Treated grapes under two types of formulation (25% and 100%) have been analyzed at the optimum maturation time, and winemaking was then subsequently carried out. The volatile compounds were analyzed by stir bar sorptive extraction-gas chromatography-mass spectrometry. The results suggest that after the grapevine treatments, grapes store the volatiles in the form of nonvolatile precursors, and some of the volatiles are released during the winemaking process, especially six months after the alcoholic fermentation. The sensory analysis shows that wines maintain the typical aroma properties of Verdejo wines at the end of fermentation; but after six months, the wine color is greener and more astringent, and, in terms of aroma, it has wooden notes as if the wine has been aged in oak barrels.     

Truffle aroma analysis by headspace solid phase microextraction

An experimental design has been used to optimize the extraction of volatile compounds from summer truffle aroma (Tuber aestivum) by using headspace solid phase microextraction. The extracted compounds have been analyzed by gas chromatography with a flame ionization detector and by gas chromatography-mass spectrometry (GC-MS). In an attempt to develop an objective method to fully characterize truffle aroma, a fiber of medium polarity (for flavors) was used to avoid discrimination toward very nonpolar and polar volatile compounds. To optimize the extraction conditions, a response surface experimental design was applied considering three factors such as extraction temperature, equilibrium time, and extraction time. From the statistical analysis of the experimental design, it was possible to determine that the most important factor influencing the abundance of aroma compounds was the extraction temperature. Optimal extraction temperature was established at approximately 50 degrees C. By using GC-MS, it was possible to identify 37 compounds, most of them previously described as responsible for truffle aroma.     

The elusiveness of coffee aroma: new insights from a non-empirical approach

Aroma is central to a pleasurable eating/drinking experience but is one of the most labile components of food. Coffee is an outstanding example. Attempts to avoid or control aroma degradation are often frustrated by ignorance of the microscopic mechanisms that are responsible for it. One of the processes most frequently invoked is radical formation, yet the identity of the radicals and their involvement in aroma degradation are poorly understood at the molecular level. Here a step forward in the fundamental understanding of this complex problem is taken by identifying the most relevant radicals and their products using first-principles calculations. Over 100 radicals originating from key aroma compounds found in coffee and other foods have been studied and classified according to an unambiguous criterion: their thermodynamic stability relative to common radical sources. This classification scheme predicts that most aroma molecules are resistant to both peroxidation and attack from phenolic antioxidants but are unstable with respect to radicals such as .OH. Dimers--generated from radical reactions--were also considered, and the most volatile species, which may further contribute to coffee aroma degradation, were focused on. Those--which are very few indeed--that have this potential have been identified.     

Impact odorants contributing to the fungus type aroma from grape berries contaminated by powdery mildew (Uncinula necator); incidence of enzymatic activities of the yeast Saccharomyces cerevisiae

Powdery mildew due to the fungus Uncinula necator is an important disease for the vineyard. The development of the fungus at the surface of the berries leads to the occurrence of a very characteristic and sometimes intense mushroom-type odor cited as an important default for grapes quality. Gas chromatography/olfactometry, gas chromatography, and multidimensional gas chromatogaphy/mass spectrometry techniques were used to investigate the most important odorants of grapes diseased by powdery mildew. Among 22 odorants detected, strongly odorant compounds were identified or tentatively identified in purified extracts obtained from grapes diseased by powdery mildew. Aroma extraction dilution analysis (AEDA) analysis revealed that 1-octen-3-one (mushroom odor), (Z)-1,5-octadien-3-one (geranium-leaf odor), and an unidentified odorous zone (fishy-mushroom like odor) were the most potent volatiles of the diseased grapes. In the presence of nonproliferating Saccharomyces cerevisiae yeast cells, and consequently during alcoholic fermentation, the enzymatic reduction of 1-octen-3-one and (Z)-1,5-octadien-3-one to much less odorant compounds, namely 3-octanone and (Z)-5-octen-3-one, was shown. Those results explain to some extent the disappearance of the fungal aroma specific to powdery mildew grapes during alcoholic fermentation.     

Analytical and sensorial characterization of the aroma of wines produced with sour rotten grapes using GC-O and GC-MS: identification of key aroma compounds

In the present work, the aroma profiles of wines elaborated from sound and sour rot-infected grapes as raw material have been studied by sensory analysis, gas chromatography-olfactometry (GC-O), and gas chromatography-mass spectrometry (GC-MS), with the aim of determining the odor volatiles most likely associated with this disease. The effect of sour rot was tested in monovarietal wines produced with the Portuguese red grape variety Trincadeira and in blends of Cabernet Sauvignon and sour rotten Trincadeira grapes. Wines produced from damaged berries exhibited clear honey-like notes not evoked by healthy samples. Ethyl phenylacetate (EPhA) and phenylacetic acid (PAA), both exhibiting sweet honey-like aromas, emerged as key aroma compounds of sour rotten wines. Their levels were 1 order of magnitude above those found in controls and reached 304 and 1668 μg L(-1) of EPhA and PAA, respectively, well above the corresponding odor thresholds. Levels of γ-nonalactone also increased by a factor 3 in sour rot samples. Results also suggest that sour rot exerts a great effect on the secondary metabolism of yeast, decreasing the levels of volatiles related to fatty acids and amino acid synthesis. The highest levels of γ-decalactone of up to 405 μg L(-1) were also found in all of the samples, suggesting that this could be a relevant aroma compound in Trincadeira wine aroma.     

Evolution of the aroma profile of sherry wine vinegars during an experimental aging in wood

Changes in the aroma profile of five Sherry wine vinegars submitted to an experimental static aging in wood were followed along 24 months. Eighteen volatile compounds were determined by GC-FID. The results were subjected to multivariate analyses: principal component analysis and linear discriminant analysis. The aroma profile of vinegar can be useful to discriminate vinegars produced from different substrates or with different aging times. During the experimental aging, volatile compounds such as methyl acetate, methanol, diacetyl, and gamma-butyrolactone underwent significant concentration increases. Moreover, the initial ethanol content of vinegars is a factor in the final aromatic richness. The formation of ethyl acetate stood out in samples with an initial ethanol content of approximately 2 alcoholic degrees.     

Effect of storage on some volatile aroma compounds in fresh-cut cantaloupe melon

Changes in volatile aroma constituents of fresh-cut cantaloupe melon with storage were determined by headspace solid-phase microextraction gas chromatography-mass spectrometry. The compounds isolated from the fruit immediately after cutting were predominantly aliphatic and aromatic esters. Storage of fruit at 4 degrees C caused a considerable decrease in concentration of esters and synthesis of the terpenoid compounds beta-ionone and geranylacetone over a period of 24 h. This change in the volatile profile with storage is consistent with that of a stress-induced defense response in the cut fruit as an adaptation process to tissue exposure and cell disruption. The same effect occurred in fruit stored at 22 degrees C and in those treated with sodium azide and ascorbic acid prior to storage. Fruit treated with ascorbic acid and sodium azide had higher concentrations of beta-ionone and geranylacetone and retained these compounds better with storage time. The reduction of esters appears to be an important early reaction step in the loss of freshness during storage of fresh-cut cantaloupe.     

Characterization of aroma compounds in apple cider using solvent-assisted flavor evaporation and headspace solid-phase microextraction

The aroma-active compounds in two apple ciders were identified using gas chromatography-olfactometry (GC-O) and GC-mass spectrometry (MS) techniques. The volatile compounds were extracted using solvent-assisted flavor evaporation (SAFE) and headspace solid-phase microextraction (HS-SPME). On the basis of odor intensity, the most important aroma compounds in the two apple cider samples were 2-phenylethanol, butanoic acid, octanoic acid, 2-methylbutanoic acid, 2-phenylethyl acetate, ethyl 2-methylbutanoate, ethyl butanoate, ethyl hexanoate, 4-ethylguaiacol, eugenol, and 4-vinylphenol. Sulfur-containing compounds, terpene derivatives, and lactones were also detected in ciders. Although most of the aroma compounds were common in both ciders, the aroma intensities were different. Comparison of extraction techniques showed that the SAFE technique had a higher recovery for acids and hydroxy-containing compounds, whereas the HS-SPME technique had a higher recovery for esters and highly volatile compounds.     

戴尔有孢圆酵母调控晚采小芒森葡萄酒乙酸和香气

为降低甜型葡萄酒中的挥发酸,进一步增加其香气复杂度,该研究利用本土戴尔有孢圆酵母R12与酿酒酵母NX11424同时接种和顺序接种发酵,研究其对贺兰山东麓产区晚采小芒森葡萄酒乙酸及香气成分的调控。与酿酒酵母单菌发酵相比,本土戴尔有孢圆酵母与酿酒酵母按照5:1、20:1、50:1的不同菌体数量比例同时接种和间隔5d顺序接种发酵,均可以显著降低晚采小芒森葡萄酒的乙酸含量,其乙酸产率分别降低19.1%、21.2%、38.2%和48.9%。此外,按20:1比例同时接种发酵,可显著提高晚采小芒森葡萄酒中萜烯类和降异戊二烯类等品种香气物质含量,和乙酸异戊酯、丁酸乙酯及苯乙醇等发酵香气物质的含量。该研究表明合理的酿酒酵母接种发酵能有效降低高糖原料酿造葡萄酒挥发酸含量,为贺兰山东麓产区葡萄酒新产品的开发提供了的技术参考。     

Competitive binding of aroma compounds by beta-cyclodextrin.

Retention of six aroma compounds has been studied after dehydration of ternary mixtures of aroma water and beta-cyclodextrin. A maximal retention of a mole of aroma per mole of beta-cyclodextrin has been observed for five of the aroma compounds, whereas retention of benzyl alcohol can be twice as high. Retention of a mixture of aroma compounds has also been studied. It has been noted that when volatile compounds compete for the same binding sites on beta-cyclodextrin, ethyl hexanoate, 2-methylbutyric acid, and benzyl alcohol are, respectively, better retained than ethyl propionate, hexanoic acid, and hexanol. Preferential retention observed with esters can be simply explained by their difference of physicochemical properties, but for the acids and alcohols a study at the molecular scale has been necessary. The better retention of 2-methylbutyric acid can be explained by differences in the nature of interaction between the acids and their carrier. At least selectivity of retention noted for the alcohol could be due to a difference in the location of the guest and also a difference in the number of aroma molecules that can be bound per polysaccharide molecule.     

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.     

Influence of eggs on the aroma composition of a sponge cake and on the aroma release in model studies on flavored sponge cakes

The use of solvent-assisted flavor evaporation extraction (SAFE) and purge and trap in Tenax allowed the identification of more than 100 volatile compounds in a sponge cake (SC-e). Gas chromatography-olfactometry (GC-O) of the SAFE extracts of crumb and crust were achieved in order to determine the most potent odorants of SC-e. The change in the traditional dough formulation of SC-e in which eggs were substituted by baking powder (SC-b) as the leavening agent produced important changes in some key aroma compounds. The release curves of some aroma compounds-some of them generated during baking and others added in the dough-were followed by cumulative headspace analysis. In the flavored SC-b, the aroma release curves showed a plateau after 15 min of purge, while the release increased proportionally with the purge time in the flavored SC-e. In general, except for some of the aroma compounds with the highest log P values, the rate of release of most of the added and generated aroma compounds was significantly influenced by the changes in the cake formulation. The higher rates of release found for the aroma compounds in SC-b could contribute to explain its rapid exhaustion of aroma compounds in the purge and trap experiments and might lead to poorer sensorial characteristics of this cake during storage.     

Processing and storage effects on orange juice aroma: a review

Freshly squeezed orange juice aroma is due to a complex mixture of volatile compounds as it lacks a specific character impact compound. Fresh hand-extracted juice is unstable, and thermal processing is required to reduce enzyme and microbial activity. Heating protocols range from the lightly heated not from concentrate, NFC, to the twice heated, reconstituted from concentrate, RFC, juices. Thermal processing profoundly effects aroma composition. Aroma volatiles are further altered by subsequent time-temperature storage conditions. Heating reduces levels of reactive aroma impact compounds such as neral and geranial, and creates off-flavors or their precursors from Maillard, Strecker, and acid catalyzed hydration reactions. Off-flavors such as 4-vinylguaiacol, p-cymene, and carvone are the products of chemical reactions. Other off-flavors such as butane-2,3-dione, guaiacol, and 2,6-dichlorophenol are indicators of microbial contaminations. Since most orange juice consumed worldwide is processed, the goal of this review is to summarize the widely scattered reports on orange juice aroma differences in the three major juice products and subsequent aroma changes due to packaging, storage, and microbial contamination with special emphasis on results from GC-O studies.     

Characterization of volatile aroma compounds in cooked black rice

Black rice ( Oryza sativa L.), an aromatic specialty rice popular in Asia, has a unique flavor, the volatile chemistry of which has not been reported. The objectives of this research were to study volatile profiles of cooked black rice and to characterize the odor-active compounds. Thirty-five volatile compounds were identified by gas chromatography-mass spectrometry using a dynamic headspace system with Tenax trapping. Aldehydes and aromatics were quantitatively in the greatest abundance, accounting for 80.1% of total relative concentration of volatiles. The concentration of 2-acetyl-1-pyrroline (2-AP) was high, exceeded only by hexanal, nonanal, and 2-pentylfuran. A total of 25 odor-active compounds, determined by gas chromatography-olfactometry, were applied to principal component analysis, demonstrating significant differences between a black and a traditional white rice cultivar in terms of aroma and explaining 93.0% of the total variation. 2-AP, guaiacol, indole, and p-xylene largely influenced the difference between the aroma in cooked black and white rice. 2-AP and guaiacol were major contributors to the unique character of black rice based on odor thresholds, relative concentrations, and olfactometry.     

优选非酿酒酵母胞外酶增香酿造干白葡萄酒效果

为了研究非酿酒酵母胞外酶促进葡萄酒发酵产香的效果,该文在爱格丽葡萄汁酒精发酵12 h后,分别添加优选胶红酵母(Rhodotorula mucilaginosa,RM)胞外酶液,优选发酵毕赤酵母(Pichia fermentans,PF)胞外酶液和商业糖苷酶制剂(almondβ-glucosidase,AG)(10 mU/mL),以不添加酶制剂的酿酒酵母纯发酵为对照,发酵过程中每24 h取样,采用HS-SPME-GC/MS(headspace solid-phase microextraction-gas chromatography/mass spectrometry)监测挥发性成分的生成变化。葡萄酒含糖量低于2 g/L时终止发酵,低温满罐密封储存,次年4月,进行葡萄酒香气仪器和感官量化分析。胞外酶液共测得6种风味酶活性,其中RM酶液中的β-D-葡萄糖苷酶、α-L-鼠李糖苷酶、β-D-木糖苷酶活性均显著(P<0.05)高于PF中的,而α-L-阿拉伯糖苷酶和酯酶在PF酶液中活性更高(P<0.05)。发酵过程中,胞外酶处理显著促进了(P<0.05)品种香气和发酵香气物质的生成,其中RM酶液显著提高了萜烯类物质和苯乙基类化合物含量,其作用效果分别比商业酶处理高41.7%和31.8%,PF酶液显著促进了发酵香气化合物的生成,尤其是脂肪酸乙酯含量约为对照的2倍。酒样感官分析结果显示,两株酵母的胞外酶处理表现出各自增香酿造的优势,其中RM酶液促进温带酸果类香气的效果突出,PF酶液显著提升了柑橘类香气。研究结果为酵母风味酶应用于葡萄酒的增香酿造提供了理论和实践指导。     

Determination of rotundone, the pepper aroma impact compound, in grapes and wine

Shiraz, also known as Syrah or Hermitage, is one of Australia's most popular red wine varieties both domestically and internationally. Black pepper aroma and flavor are important to some Australian Shiraz red wine styles. Recently, rotundone (a bicyclic sesquiterpene) was identified as the potent aroma compound responsible for pepper aromas in grapes, wine, herbs, and spices, including peppercorns. Here the development, optimization, and validation of the analytical method for the quantitative determination of rotundone in grapes and wine are described and discussed. The method is precise, accurate, robust, and sensitive with a subpart per trillion limit of quantitation. The method uses stable isotope dilution analysis with d(5)-rotundone as internal standard, solid-phase extraction and microextraction, and gas chromatography-mass spectrometry.