Aroma Generation Research Articles

Analysis of characteristic aroma of fungal fermented Fuzhuan brick‐tea by gas chromatography/mass spectrophotometry

AbstractFuzhuan brick‐tea is a popular fermented Chinese dark tea because of its typical fungal aroma. Fungal growth during the production process is the key step in achieving the unique colour, aroma and taste of Fuzhuan brick‐tea. To further understand the generation of the characteristic aroma, changes in the main volatile compounds of Fuzhuan brick‐tea during the fungal growth stage were studied by gas chromatography/mass spectrophotometry. The results showed that the content of volatile compounds, especially aldehyde compounds with stale aroma such as (E)‐2‐pentenal, (E)‐2‐hexenal, 1‐penten‐3‐ol, (E, E)‐2,4‐heptadienal and (E, Z)‐2,4‐heptadienal, increased significantly in fermented tea samples. The concentration of terpene alcohols with flower aroma also increased notably during the fermentation process. The compounds with stale and flower aromas in combination with some volatile components of the raw material contributed to the characteristic ‘fungal/flower’ aroma of Fuzhuan brick‐tea. Microbial metabolism during the fermentation process probably played the key role in the generation of characteristic aromatic compounds of Fuzhuan brick‐tea. Copyright © 2007 Society of Chemical Industry

Origin of carbons in sulfur-containing aroma compounds from the Maillard reaction of xylose, cysteine and thiamine

The Maillard reaction of cysteine and thiamine with reducing sugars is known to be important for the aroma generation both in meat and meat-like process flavourings. Headspace SPME analysis in combination with GC-MS was used to analyse the volatiles produced from a solution of [ 13C 5]xylose, cysteine and thiamine, heated at 145 °C during 20 min. Analysis of the mass spectra showed that the resulting 2-furaldehyde and 2-furfurylthiol were 13C 5-labeled and hence stem from xylose, whereas 3-mercapto-2-butanone, 4,5-dihydro-2-methyl-3(2 H)-furanone, 4,5-dihydro-2-methyl-3-furanthiol and 4,5-dihydro-2-methyl-3(2 H)-thiophene were virtually unlabeled suggesting their origin from thiamine. Xylose and thiamine were equally important for the formation of 2-methyl-3-furanthiol and 3-mercapto-2-pentanone, when cysteine was present in the reaction. In the absence of cysteine, however, both sulfur compounds were only formed from thiamine indicating that xylose did no longer play a role therewith emphasizing the role of cysteine as sulfur source.

Addition of amino acids to grape juice of the Merlot variety: Effect on amino acid uptake and aroma generation during alcoholic fermentation

The effects of adding selected amino acids (phenylalanine, alanine, aspartic acid and threonine) to grape juice on the generation of aroma compounds and on amino acid uptake were studied. The fermentation kinetics varied according to the quantities of amino acids added. The fermentations finished more quickly in supplemented juices and their alcoholic content was significantly higher than in the control ( p < 0.05). Amino acids were consumed mainly in the first quarter of fermentation. Higher alcohol formation took place at the same time as ethanol formation: with more amino acids present in the medium, more phenyl ethanol ( p = 0.01) and benzyl alcohol were formed while isoamyl alcohol production decreased. The contents of isoamyl and phenylethyl acetates, ethyl hexanoate and ethyl octanoate, as well as most fatty acids increased during the fermentation, reaching a maximum for 10% of ethanol; with higher alcoholic contents, their concentrations decreased.

The Roles of Free and Bound Amino Acids in Maillard Aroma Generation

The Roles of Free and Bound Amino Acids in Maillard Aroma Generation

Quality characteristics of edible oils.

Edible oils provide a concentrated source of energy and essential fatty acids through daily dietary intake. Lipids also serve as an important constituent of cell walls and carrier of fat-soluble vitamins. In addition, lipids provide flavor, texture and mouthfeel to the food. Edible vegetable oils also serve as a heating medium and are important in the generation of aroma, some of which arise from direct interaction of lipids and/or their degradation products with food constituents.

Changes in green coffee protein profiles during roasting.

To reveal its flavor, coffee has to be roasted. In fact, the green coffee bean contains all ingredients necessary for the later development of coffee flavor. It is now widely accepted that free amino acids and peptides are required for the generation of coffee aroma. However, the mechanisms leading to defined mixtures of free amino acids and peptides remain unknown. Information pertaining to the identification of precursor proteins is also lacking. To answer some of these questions, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) was used to follow the fate of green coffee proteins. Two conditions were considered: roasting and incubation of green coffee suspensions at 37 degrees C. Coffee beans were observed to acquire the potential to spontaneously release H(2)O(2) upon polymerization of their proteins during roasting. Fragmentation of proteins was also observed. Conversely, H(2)O(2) was found to control polymerization and fragmentation of green coffee proteins in solution at 37 degrees C. Polymerization and fragmentation patterns under the two conditions were comparable. These observations suggest that the two conditions under study triggered, at least to some extent, similar biochemical mechanisms involving autoxidation. Throughout this study, a unique fragmentation cascade involving the 11S coffee storage protein was identified. Generated fragments shared an atypical staining behavior linked to their sensitivity to redox conditions.

Studies on aroma generation in lulo (Solanum quitoense): enzymatic hydrolysis of glycosides from leaves

Five C13-norisoprenoid glycosides, isolated from lulo (Solanum quitoense) leaves, were subjected to enzymatic hydrolysis with a commercial glucosidase (emulsin) and also with an enzymatic preparation having glycosidase activity, isolated from lulo fruit pulp. The volatile compounds generated after reaction were characterized by capillary GC and capillary GC–MS. Lulo fruit glycosidases were extracted by ammonium sulfate precipitation at pH 6.5 and subjected to fractionation by hydrophobic interaction chromatography (HIC) on phenyl Sepharose® gel, and some of their properties were determined. As the result of enzymatic hydrolysis with exogenous enzymes (emulsin), glycosides isolated from lulo leaves produced only the aglycone (glycosidically bound volatile); in contrast, enzymatic hydrolysis of glycosides, using endogenous enzymes (lulo fruit glycosidases), generated additional volatile compounds, some recognisable as components of fruit flavour. The role of lulo leaf glycosides as flavour precursors was confirmed.

Recent Advances in the Chemistry of Strecker Degradation and Amadori Rearrangement: Implications to Aroma and Color Formation

The importance of Strecker degradation lies in its ability to produce Strecker aldehydes and 2-aminocarbonyl compounds, both are critical intermediates in the generation of aromas during Maillard reaction, however, they can also be formed independently of the pathways established for Strecker degradation. Strecker aldehyde can be formed directly either from free amino acids or from Amadori products. Several pathways have been proposed in the literature for the mechanism of this transformation. On the other hand, Amadori or Heyns rearrangements of ammonia with reducing sugars can also generate 2-aminocarbonyl compounds without the formation of Strecker aldehyde. In addition, isomerization of the imine bond of the Schiff base formed between a reducing sugar and an amino acid, can initiate a transamination reaction and convert the amino acid into the corresponding α-keto acid and the sugar into its α-amino alcohol derivative. The reverse of this reaction, has been documented to produce Amadori products. The α-keto acids can either decarboxylate to produce Strecker aldehydes or undergo Strecker degradation (as a α-dicarbonyl compound) with amino acids to also produce Strecker aldehydes. This review will examine the role of Strecker degradation and Amadori rearrangement, under the light of recent findings, in controlling the balance among four critically important key intermediates: α-dicarbonyl, α-hydroxycarbonyl, 2-amino carbonyls and 2-(amino acid)-carbonyl compounds, during the Maillard reaction and hence control relative importance of aromagenic versus chromogenic pathways.

Free, glycosidically bound, and phosphate bound flavor constituents of badea (Passiflora quadrangularis) fruit pulp

Free volatiles, glycosidically bound, and phosphate bound volatile compounds from badea fruit pulp were identified by capillary GC and capillary GC-MS analyses. Free volatile extract was characterized as a mixture of 57 components with (5E)-2,6-dimethyl-5,7-octadiene-2,3-diol, (2E)-2,6-dimethyl-2,5-heptadienoic acid, benzoic acid, furaneol, benzyl alcohol, 2,6-dimethyl-5-hepten-1-ol, dimethylheptadienoic acid, and 2,6-dimethylheptenol, as major components. Three of those: (E)-2-pentenol, 2,6-dimethyl-5-hepten-1-ol, and (2E)-2,6-dimethyl-2,5-heptadienoic acid, displayed a strong resemblance to the aroma of the fresh fruit. Volatile compounds released by enzymatic hydrolysis of glycosidic and phosphate extracts were all present in the aroma of the fruit pulp. This fact strongly suggests an active role of glycosides and phosphates in the generation of fruit aroma. Furthermore, the new monoterpenoids trans-4-hydroxylinalool 3,6-oxide and cis-4-hydroxylinalool 3,6-oxide were characterized as major transformation products of (5E)-2,6-dimethyl-5,7-octadiene-2,3-diol under acidic conditions.

Wagyu Beef Aroma in Wagyu (Japanese Black Cattle) Beef Preferred by the Japanese over Imported Beef

Preference of taste or both aroma and taste between Wagyu (Japanese Black Cattle) beef and imported beef on market was compared to reveal reasons why Wagyu beef is considered to be more palatable than imported beef in Japan. Panelists ate heated beef samples and assessed preference on taste by pinching their noses and both aroma and taste by not pinching their noses. As a result there was no difference in preference on taste between both samples, but in the case of both aroma and taste Wagyu beef was significantly preferred to imported beef. Wagyu beef presented a preferable, sweet and fatty aroma, which was different from the conditioned raw beef aroma, while imported beef did not present such an aroma. Therefore, the existence of such an aroma was presumed to be one of the reasons why Japanese people preferred Wagyu beef to imported beef. We proposed to name this aroma Wagyu beef aroma. The optimum cooking temperature to generate Wagyu beef aroma was found to be 80°C. This aroma was almost absent in Wagyu beef immediately after slaughter. The experiment on additional storage of Wagyu beef slices suggested that a considerable high level of fat-marbling and contact with oxygen were necessary to generate Wagyu beef aroma. On the other hand, an antibacterial agent, chloramphenicol, did not inhibit the generation of Wagyu beef aroma in highly marbled beef stored under air, indicating that a group of bacteria including Brochothrix thermosphacta which is essential for the generation of the conditioned raw beef aroma were not responsible for the generation of Wagyu beef aroma.

Aroma Generation by Horticultural Products: What Can We Control? Introduction to the Workshop

Received for publication 7 Sept. 1999. Accepted for publication 6 Jan. 2000. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. E-mail address: beaudry@pilot.msu.edu Aroma Generation by Horticultural Products: What Can We Control? Introduction to the Workshop

Effect of urea on volatile generation from Maillard reaction of cysteine and ribose.

Urea occurs naturally in many food products, and its presence affects food quality. However, little is known about its impact on flavor generation in food production. In this study, the urea contents in beef, pork, and chicken were determined. The effects of urea and pH on thermal flavor generation were investigated using the model system of cysteine with ribose, which was heated to the roasting temperature of 180 degrees C for 2 h at pH 5 and pH 8.5. The results revealed relatively large amounts of urea in these meats and demonstrated that pH affects aroma generation. Volatiles identified from the reaction system of ribose and cysteine showed that sulfur-containing compounds such as thiophenes, thiazoles, and thiophenethiols were the most abundant compounds. The addition of urea into the reaction mixture caused the disappearance or reduction in content of some sulfur-containing compounds but resulted in the generation of several important nitrogen-containing volatiles, like pyrazine, methylpyrazine, 2,5- (and 2,6-)dimethylpyrazine and other alkylpyrazines, which are known to elicit roasty, nutty flavor notes. A plausible explanation for this phenomenon is that ammonia can be released from urea upon heating and the formed ammonia competes with hydrogen sulfide to react with Maillard reaction precursors to produce nitrogen-containing compounds such as alkylpyrazines.

Resveratrol is a potent inhibitor of the dioxygenase activity of lipoxygenase.

Resveratrol is a naturally occurring phytoalexin, present in grapes and other food products, with important antioxidant properties. Although still under debate, it is generally assumed that resveratrol has protective effects against heart diseases and probably tumor development. Lipoxygenase is a dioxygenase with peroxidase activity involved in the synthesis of mediators in inflammatory, atherosclerotic, and carcinogenic processes. Lipoxygenase activity is also involved in the generation of flavors and aromas in foods from animal or vegetal sources. The results presented here show that resveratrol was a potent inhibitor of the dioxygenase activity of lipoxygenase, with an IC(50) = 13 microM. Simultaneously, resveratrol was oxidized by the peroxidase activity of lipoxygenase with a V(max) = 0.28 microM min(-1) and a k(M) = 16.6 microM. Furthermore, oxidized resveratrol was as efficient a lipoxygenase inhibitor as in its reduced form. From the data obtained it can be concluded that both resveratrol and its oxidized form can act as inhibitors of the dioxygenase activity of lipoxygenase. In contrast, the hydroperoxidase activity of lipoxygenase was not inhibited by resveratrol. These results suggest that resveratrol may be used as an antioxidant food additive and as a pharmacological agent to prevent the generation of eicosanoids involved in pathological processes.

Seasonal Change of Volatile Compounds of Citrus sudachi during Maturation.

Seasonal change of volatile components in Citrus sudachi was monitored by headspace gas-chromatographic analyses. The limonene content increased sharply from 50.87% (unripe sudachi) to 87.23% (over-ripe sudachi) in accordance with maturation of the fruit, while α-thujene, sabinene, α-phellandrene, β-ocimene and γ-terpinene decreased. Linalool decreased particularly sharply during maturation from 5.20% to 0.55%. Other oxygenated compounds such as cis- and trans-limonen-1,2-oxide, citronellal, decanal, terpinen-4-ol and carvone were not detected in unripe sudachi but appeared in the volatiles during the ripening progress. These oxygenated terpenes had larger log Uo values (>1). Furthermore, as limonene, α-pinene, decanal, citronellal, linalool are the characteristic odor chemicals in sudachi, these increase and decrease of odor active terpenes during maturation are determined to contribute to the change of the characteristic aroma and the generation of sudachi-like aroma.

Fusel oil as precursor for aroma generation by biotransformation using lipase: scientific note.

The feasibility of using mixtures of C4 and C5 chain-length aliphatic alcohols from fusel oil as the bulk organic media for lipase-mediated synthesis of laurate esters was assessed. Reaction mixtures consisted of lauric acid, lipase, solvent (if added), and appropriate amount of fusel oil (previously dehydrated with inorganic salts and molecular sieves). The influence of the reaction conditions such as substrate concentrations and temperature were investigated. Increased molar ratio of acyl donor to acyl acceptor allowed the esterification to proceed with no need for solvent addition.

Sensory Characterisation of the Aromas Generated in Extruded Maize and Wheat Flour

The effects of extrusion temperature, moisture and residence time (RT) on flavour generation in maize and wheat flours processed by direct extrusion cooking have been investigated using quantitative descriptive aroma profiling. Temperature and moisture level were important variables influencing the aroma generation in extrusion of both maize and wheat flour. Changing RT from 35 to 60 s had a relatively small effect on the aroma of extruded maize. A greater effect of RT on aroma generation was noted for extruded wheat flour. The maize and wheat extrudates were described by similar aroma vocabularies, although low-intensity sulphury and musty notes were observed in the extruded wheat. The extrudates from the lowest extrusion temperature (120 °C) and higher moisture levels (18 and 22%) were mainly characterised by porridge-like, cooked milk, cooked vegetable terms. At the intermediate conditions (150 °C and 18% moisture), popcorn, toasted and puffed wheat notes dominated the extrudates from both cereals, with the popcorn note more characteristic for the extruded maize samples. The popcorn aroma was lower in the extrudates prepared under the most severe conditions (180 °C and 14% moisture), where puffed wheat, burnt and toasted aromas were scored at relative high intensity.

Generation of Proline-Specific Maillard Compounds by the Reaction of 2-Deoxyglucose with Proline

The proline-specific Maillard products including 2,3-dihydro-1H-pyrrolizines, hexahydro-7H-cyclopenta[b]pyridin-7-ones, and cyclopent[b]azepin-8(1H)-ones were generated by both 2-deoxyglucose/proline and glucose/proline model reactions at 180 °C for 2 h. The amounts of these products generated in 2-deoxyglucose/proline reaction were far less than (<12%) those generated in the glucose/proline model reaction at both pH 9.0 and 4.0. The pH effect on the formation of these products in the 2-deoxyglucose/proline model was not significant, while a lower pH favored the generation of these products in the glucose/proline reaction. The generation of the active precursors of these proline-specific Maillard products from 2-deoxyglucose is proposed. Keywords: Maillard reaction; proline, aroma generation; 2-deoxyglucose; pH effect

Modifying Flavor and Aroma from Cut Onions and Other Alliums

World-wide, onions are the most important member of the vegetable Alliums. Members of this group are primarily consumed because of their unique flavors and aromas. Allium aroma is dominated by organosulfur compounds arising from the enzymatic decomposition of S-alk(en)yl-L-cysteine S oxide (ACSO) flavor precursors following tissue disruption. Primary products from the decomposition of the four ACSOs are sulfenic acids, including the lachrymator, pyruvate, and ammonia. The sulfenic acids, however, are short-lived and disassociate rapidly into thiosulfinates, which, in turn, are unstable and randomly rearrange or dissociate over time. The thiosulfinates each have unique sensory qualities and are responsible for the flavor notes of fresh cut Alliums, while of the degradation compounds can contribute to off-fl avors and bitterness. ACSO concentration affects ultimate flavor and aroma intensity, while ACSO composition determines among species flavor differences. Controlling sulfur uptake and sulfur metabolism that terminates in ACSO synthesis is one method of controlling ultimate flavor and aroma intensity. Cultivar difference in the ability to absorb and metabolize sulfur have been identified. Sulfur availability, plant growing temperatures, and irrigation intensity also influence sulfur absorption and metabolism, and can be manipulated. Differences in alliinase concentration and the efficiency at which alliinase decompose the ACSO substrates also affect aroma generation. Difficulties, however, exist in controlling alliinase activity. Alliinase has been cloned and anti-sense constructs have been made, but an efficient vectoring system has yet to be developed for the Alliums.

The Biochemistry and Control of Cell Disruption-dependent Aroma Generation by Tomatoes

More than 400 volatile components have been identified in tomato fruit, of which only 10–16 are likely to be important contributors to tomato flavor/aroma based on odor threshold data. Tomato volatiles are grouped as lipid-derived, carotenoid-related, amino acid-related, lignin-related, or of uncertain origin. These flavor components are either present in intact fruit or formed after blending due to mixing of previously compartmentalized enzymes and substrates. Lipid-derived volatiles are the biggest group containing cis-3-hexenal and hexanal, which are quantitatively the major volatile compounds in tomato fruit. cis-3-Hexenal and -ionone have the highest odor thresholds among tomato volatile compounds so far identified. Most of these compounds increase during ripening (or the enzymes, substrates and conditions develop that result in increased levels after blending) and appear to be related to ethylene production. Biosynthetic pathways have been established or suggested for most of the important flavor components, of which lipid degradation is the best-understood. Linoleic and linolenic acids are oxidized to hydroperoxides by lipoxygenase, which are then cleaved to volatile C6 aldehydes (hexanal and cis-3-hexenal, respectively). There are two membrane-associated lipoxygenases (tomloxA and B), of which tomloxB appears to be fruit-specific and increases during ripening. Alcohol dehydrogenase (ADH) has been demonstrated to catalyze the interconversion of trans-hexene-2-al and -2-ol and of trans-hexene-2-al, hexanal and hexanol. The enzyme product of the Adh2 gene is induced by 3% O2, and is developmentally expressed in fruit aside from anoxic induction. Naturally occurring mutants and genetically engineered tomatoes with reduced ethylene production, color and/or retarded ripening patterns show changes in volatile concentrations.

花はなぜ香るのか？ 香気生成のメカニズムを探る

花はなぜ香るのか？ 香気生成のメカニズムを探る