Odour intensities of hop oil components

The Effect of Sodium Chloride on the Physicochemical and Textural Properties and Flavor Characteristics of Sous Vide Cooked Duck Meat

This study was conducted to evaluate the effect of salt brining process parameters (salt concentration 0-15%, brining time 4-12 h, brining temperature 4-20 °C) on the quality of sous vide cooked duck meat by a single factor combined with response surface methodology (RSM). The sensory evaluation, physicochemical indexes (color, weight loss, NaCl content, TBARS value, and texture properties), and flavor characteristics were analyzed. The sensory overall mean score was applied as the evaluation index to optimize the brining conditions by RSM, and the optimum results contained a salt concentration of 11.69%, a brining temperature of 7.35 °C, and a brining time of 8.03 h. Under these conditions, the sensory overall mean score of duck meat was 8.59, with a relatively higher a* value and moderate NaCl content. GC-MS and odor activity value (OAV) results indicated that salt brining treatment significantly promoted the formation of the major odorants in duck meat, including pentanal, heptanal, octanal, (E)-2-nonenal, cis-4-decenal, decanal, 2,4-decadienal, (E,E)-2,4-decadienal, 1-heptanol, and 2-methyl-3-octanone, but decreased the content of hexanal, (E)-2-octenal, nonanal, (E,E)-2,4-nonadienal, 1-octen-3-ol, and 1-octen-3-one. 5'-nucleotides in duck meat were significantly increased after brining treatment. Therefore, salt brining treatment could be regarded as an efficient way to improve the sensory, aroma, and taste quality of sous vide cooked meat.

Sensory relevance of seven aroma compounds involved in unintended but potentially fraudulent aromatization of wine due to aroma carryover

Bottling regular wines following aromatized wines on the same filling lines bears the risk of unintentional aroma carryover, which has led to accusations of illegal aromatization. Obeying guidelines of good manufacturing practice, aroma carryover with no sensory relevance shall be considered as a technical unavoidable transfer having no legal consequences. To detect sensory relevance, odor activity values greater than one are proposed. Odor detection thresholds (OTs) were determined in water, model wine, and white wine for three lactones, α-ionone, ethyl 2-methylbutanoate, trans-cinnamaldehyde, and eugenol. Using different matrices OTs varied by factors of 2 for α-ionone and up to 23000 for ethyl 2-methylbutanoate. For α-ionone, being most prone for carryover, the three times higher OT of consumers did not trigger any preference for the aromatized wines, but rejection at 300 µg/L. Assessing α-ionone spiked wines by descriptive analysis, significant changes in sensory attributes only occurred at concentrations 10 times above OT.

Performance of alternative drying techniques on hop (Humulus lupulus L.) aroma quality: An HS-SPME-GC-MS-O and chemometrics combined approach

Economically feasible and effective hop drying strategies are urgently needed to respond to the increasing number of microbrewers in US. In this study, hops were dried by dehydrator-drying (52 °C), oven-drying (52 °C) and freeze-drying (25 °C) until the final moisture content reached 8-10%. Headspace solid-phase microextraction-gas chromatography-mass spectrometry-olfactometry (HS-SPME-GC-MS-O) was employed to analyze the aroma profiles in all dried hops. Methyl octanoate, β-myrcene, trans-α-bergamotene, linalool and geraniol were perceived as high-intensity aromas in all samples. Generally, dehydrator-dried hops contained the highest contents of aroma compounds among all groups, showing an increase of 5-23% and 6-37% when compared to freeze- and oven-dried hops, respectively. Principal component and hierarchical cluster analyses also revealed aroma content differences from three drying methods. Dehydrator drying at 52 °C was therefore considered as an alternative and promising drying approach for smaller-scale hop processing, which can largely benefit regional producers and local craft breweries.

Aroma characterization of regional Cascade and Chinook hops (Humulus lupulus L.)

Aroma compounds in Cascade and Chinook hops harvested from multiple Virginia locations were identified by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and aroma extract dilution analysis (AEDA). Selected aroma compounds were quantitated by combination of stable isotope dilution analysis (SIDA) and standard addition method (SAM). A total of 33 aroma-active compounds were detected in five samples with β-myrcene, methyl octanoate, geraniol and linalool being the predominant compounds based on their high flavor dilution (FD) factors and odor activity values (OAVs). L-Calamenene and germacrene B was the major characteristic component unique to Cascade and Chinook variety, respectively. Principal component analysis (PCA) showed distinctive aroma profiles for all samples except for Blacksburg and Petersburg Cascade. Hierarchical cluster analysis (HCA) reflected the higher contents of most aroma-active compounds in Meadowview Cascade and Chinook when compared to their counterparts. The significant variations suggested the potential influences of environmental factors and agronomic practices on hop aroma quality.

Characterization of Key Aroma Compounds in Pellets of Different Hop Varieties (Humulus lupulus L.) by Means of the Sensomics Approach

The use of hops in beer brewing is mainly based on its content of bitter acids and aroma compounds. Due to the loss of volatile odorants during wort boiling, the so-called dry hopping is a possibility to intensify the hoppy aroma in the final beer. To clarify the potential of different hop varieties for aroma modulation of beer via dry hopping, key aroma compounds of three different hop varieties were characterized using the sensomics approach. Aroma extract dilution analysis revealed 41 aroma-active compounds, of which 39 were identified via gas chromatography-olfactometry and gas chromatography-mass spectrometry. The highest flavor dilution factor was determined for myrcene with a geranium-like odor. Fourteen substances were quantitated by stable isotope dilution analysis and further two odorants via the internal standard method; all of them revealed odor activity values (OAVs; ratio of concentration to odor threshold) ≥1. Linalool, 3-methylbutanoic acid, myrcene, and dimethyl trisulfide showed the highest OAVs (>1000) in all analyzed hop varieties. For validation of the analytical data, reconstitution models were prepared by adding all quantitated aroma compounds with OAVs ≥ 1 in their naturally occurring concentrations to cellulose as matrix. All three recombinates showed a very high similarity to the aroma profile of the respective hop sample, confirming the correct identification and quantitation of all key aroma compounds.

Characterization of the Key Aroma Compounds in Three Truffle Varieties from China by Flavoromics Approach

The volatile compounds of three different fresh-picked truffle varieties (Tuber sinensis, T1, Tuber sinoalbidum, T2 and Tuber sinoexcavatum, T3) were extracted by headspace solid-phase microextraction (HS-SPME). Separation and identification of volatile components and sulfur compounds were investigated by gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame photometric detection (GC-FPD). The results showed that 44, 43 and 44 volatile compounds were detected in T1, T2 and T3 samples, respectively. In addition, 9, 10 and 9 sulfur compounds were identified in three samples by GC-FPD, respectively. Combining physicochemical and sensory properties, T1 presented fatty, green and rotten cabbage odor; T2 exhibited mushroom, sulfuric and musty odor notes; T3 had nutty, floral and roasted potato odor. Dimethyl sulfide, 3-methylbutanal, dimethyl disulfide, 3-octanone, bis(methylthio) methane, octanal, 1-octen-3-one, 1-octen-3-ol and benzeneacetaldehyde played indispensable roles in the overall aroma of three truffles. Finally, based on quantitative concentration in T1, odorous compounds (OAV) > 1 were mixed to recombine aroma, demonstrating that these key aroma compounds based on OAV can successfully recombine pretty similar aroma of each variety.

GC-Recomposition-Olfactometry (GC-R) and multivariate study of three terpenoid compounds in the aroma profile of Angostura bitters

Foods and beverage aroma results from multicomponent mixtures of volatile compounds present in the food that interact with olfactory receptors and produce a perceptual response in the brain. However, the perceptual interactions that occur when complex odor mixtures are combined are not well understood. Here we used Gas chromatography-Recomposition-Olfactometry (GC-R) to better understand the role that individual compounds have on the perceived sensory aroma of bitters. Bitters are the concentrated alcoholic extract of flavorful plant materials with a wide range of complex sensory and chemical aroma profiles that have not been extensively studied. Previously, we demonstrated that Angostura bitters are characterized by complex aroma attributes described as cola, ginger, orange peel, and black pepper and that the volatile composition of Angostura bitters is predominantly composed of terpenoids. Using GC-R to create in-instrument mixtures of the Angostura headspace extracts, the sensory attributes of Angostura extracts with linalool, α-terpinyl-acetate and caryophyllene omitted were evaluated. The omission experiments demonstrated direct and indirect effects of the individual compounds on the aroma attributes of Angostura bitters, through masking, additive, and synergistic interactions. Caryophyllene in particular, which was present in the headspace extracts at concentration only slightly above sensory threshold levels, had a large and unexpected impact on the sensory properties of the mixtures and may be most responsible for the aromas associated with the whole sample. The GC-R and statistical approaches used here provided valuable tools to reveal relationships among individual compounds and aroma attributes of foods that have not been currently theorized using existing analytical approaches.

Hop Compounds: Extraction Techniques, Chemical Analyses, Antioxidative, Antimicrobial, and Anticarcinogenic Effects

Hop plants comprise a variety of natural compounds greatly differing in their structure and properties. A wide range of methods have been developed for their isolation and chemical analysis, as well as for determining their antioxidative, antimicrobial, and antigenotoxic potentials. This contribution provides an overview of extraction and fractionation techniques of the most important hop compounds known for their health-promoting features. Although hops remain the principal ingredient for providing the taste, stability, and antimicrobial protection of beer, they have found applications in the pharmaceutical and other food industries as well. This review focuses on numerous health-promoting effects of hops raging from antioxidative, sedative, and anti-inflammatory potentials, over anticarcinogenic features to estrogenic activity. Therefore, hops should be exploited for the prevention and even healing of several prevalent diseases like cardiovascular disorders and various cancer types. New ideas for future studies on hops are finally presented: computational investigations of chemical reactivities of hop compounds, nanoencapsulation, and synergistic effects leading to a higher bioavailability of biologically active substances as well as the application of waste hop biomass from breweries for the production of high-added-value products in accordance with the biorefinery concept.

Rapid differentiation of Chinese hop varieties (Humulus lupulus) using volatile fingerprinting by HS-SPME-GC-MS combined with multivariate statistical analysis

BACKGROUND

Hops impart flavor to beer, with the volatile components characterizing the various hop varieties and qualities. Fingerprinting, especially flavor fingerprinting, is often used to identify 'flavor products' because inconsistencies in the description of flavor may lead to an incorrect definition of beer quality. Compared to flavor fingerprinting, volatile fingerprinting is simpler and easier.

RESULTS

We performed volatile fingerprinting using head space-solid phase micro-extraction gas chromatography-mass spectrometry combined with similarity analysis and principal component analysis (PCA) for evaluating and distinguishing between three major Chinese hops. Eighty-four volatiles were identified, which were classified into seven categories. Volatile fingerprinting based on similarity analysis did not yield any obvious result. By contrast, hop varieties and qualities were identified using volatile fingerprinting based on PCA. The potential variables explained the variance in the three hop varieties. In addition, the dendrogram and principal component score plot described the differences and classifications of hops.

CONCLUSION

Volatile fingerprinting plus multivariate statistical analysis can rapidly differentiate between the different varieties and qualities of the three major Chinese hops. Furthermore, this method can be used as a reference in other fields. © 2018 Society of Chemical Industry.

Influence of two yeast strains in free, bioimmobilized or immobilized with alginate forms on the aromatic profile of long aged sparkling wines

Production of sparkling wines involve a second alcoholic fermentation and contact with yeast less over an extended period of time, which influences the aroma composition and sensory quality of the resulting wines. Sparkling wines obtained with two yeast strains inoculated as free cells, immobilized in alginate bed and bioimmobilized as biocapsules, were aged during 32 months. Among the volatile compounds, high Odor Activity Values were obtained with isoamyl acetate, ethyl propanoate, ethyl butanoate, ethyl 3-methylbutanoate, ethyl hexanoate, ethyl octanoate, hexanol, 2-methoxy-4-vinylphenol, decanal, octanoic acid, decanoic acid and TDN. Taken together these contribute more than 70% of the overall aromatic series value. Although some results rely more on the yeast strain than the inoculation format, specific aroma compounds were associated with the immobilization format, allowing the classification of sparkling wines by PCA. As a result the aroma quality of sparkling wines could be improved using immobilized yeasts.

Characterization of the Key Aroma Volatile Compounds in Cranberry (Vaccinium macrocarpon Ait.) Using Gas Chromatography-Olfactometry (GC-O) and Odor Activity Value (OAV)

The volatile compounds of cranberries obtained from four cultivars (Early Black, Y1; Howes, Y2; Searles, Y3; and McFarlin, Y4) were analyzed by gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), and GC-flame photometric detection (FPD). The result presented that a total of thirty-three, thirty-four, thirty-four, and thirty-six odor-active compounds were identified by GC-O in the Y1, Y2, Y3, and Y4, respectively. In addition, twenty-two, twenty-two, thirty, and twenty-seven quantified compounds were demonstrated as important odorants according to odor activity values (OAVs > 1). Among these compounds, hexanal (OAV: 27-60), pentanal (OAV: 31-51), (E)-2-heptenal (OAV: 17-66), (E)-2-hexenal (OAV: 18-63), (E)-2-octenal (OAV: 10-28), (E)-2-nonenal (OAV: 8-77), ethyl 2-methylbutyrate (OAV: 10-33), β-ionone (OAV: 8-73), 2-methylbutyric acid (OAV: 18-37), and octanal (OAV: 4-24) contributed greatly to the aroma of cranberry. Partial least-squares regression (PLSR) was used to process the mean data accumulated from sensory evaluation by the panelists, odor-active aroma compounds (OAVs > 1), and samples. Sample Y3 was highly correlated with the sensory descriptors "floral" and "fruity". Sample Y4 was greatly related to the sensory descriptors "mellow" and "green and grass". Finally, an aroma reconstitution (Model A) was prepared by mixing the odor-active aroma compounds (OAVs > 1) based on their measured concentrations in the Y1 sample, indicating that the aroma profile of the reconstitution was pretty similar to that of the original sample.

Identification of character-impact odorants in a cola-flavored carbonated beverage by quantitative analysis and omission studies of aroma reconstitution models

Thirty aroma-active components of a cola-flavored carbonated beverage were quantitated by stable isotope dilution assays, and their odor activity values (OAVs) were calculated. The OAV results revealed that 1,8-cineole, (R)-(-)-linalool, and octanal made the greatest contribution to the overall aroma of the cola. A cola aroma reconstitution model was constructed by adding 20 high-purity standards to an aqueous sucrose-phosphoric acid solution. The results of headspace solid-phase microextraction and sensory analyses were used to adjust the model to better match authentic cola. The rebalanced model was used as a complete model for the omission study. Sensory results indicated that omission of a group consisting of methyleugenol, (E)-cinnamaldehyde, eugenol, and (Z)- and (E)-isoeugenols differed from the complete model, while omission of the individual components of this group did not differ from the complete model. These results indicate that a balance of numerous odorants is responsible for the characteristic aroma of cola-flavored carbonated beverages.

Perceptual characterization and analysis of aroma mixtures using gas chromatography recomposition-olfactometry

This paper describes the design of a new instrumental technique, Gas Chromatography Recomposition-Olfactometry (GC-R), that adapts the reconstitution technique used in flavor chemistry studies by extracting volatiles from a sample by headspace solid-phase microextraction (SPME), separating the extract on a capillary GC column, and recombining individual compounds selectively as they elute off of the column into a mixture for sensory analysis (Figure 1). Using the chromatogram of a mixture as a map, the GC-R instrument allows the operator to “cut apart" and recombine the components of the mixture at will, selecting compounds, peaks, or sections based on retention time to include or exclude in a reconstitution for sensory analysis. Selective recombination is accomplished with the installation of a Deans Switch directly in-line with the column, which directs compounds either to waste or to a cryotrap at the operator's discretion. This enables the creation of, for example, aroma reconstitutions incorporating all of the volatiles in a sample, including instrumentally undetectable compounds as well those present at concentrations below sensory thresholds, thus correcting for the “reconstitution discrepancy" sometimes noted in flavor chemistry studies. Using only flowering lavender (Lavandula angustifola ‘Hidcote Blue’) as a source for volatiles, we used the instrument to build mixtures of subsets of lavender volatiles in-instrument and characterized their aroma qualities with a sensory panel. We showed evidence of additive, masking, and synergistic effects in these mixtures and of “lavender' aroma character as an emergent property of specific mixtures. This was accomplished without the need for chemical standards, reductive aroma models, or calculation of Odor Activity Values, and is broadly applicable to any aroma or flavor.

Some insights into analytical bias involved in the application of grab sampling for volatile organic compounds: a case study against used Tedlar bags

In this study, we have examined the patterns of VOCs released from used Tedlar bags that were once used for the collection under strong source activities. In this way, we attempted to account for the possible bias associated with the repetitive use of Tedlar bags. To this end, we selected the bags that were never heated. All of these target bags were used in ambient temperature (typically at or below 30°C). These bags were also dealt carefully to avoid any mechanical abrasion. This study will provide the essential information regarding the interaction between VOCs and Tedlar bag materials as a potential source of bias in bag sampling approaches.

Quantification and odor contribution of 2-furanmethanethiol in different types of fermented soybean paste miso

2-Furanmethanethiol, a compound contained in many kinds of food, was identified for the first time in five types of miso fermented soybean paste (red salty rice miso, thin-colored salty rice miso, weak salty rice miso, barley miso, and soy miso) by specific extraction of volatile thiols using p-hydroxymercuribenzoate. In the triangle test with red salty rice miso, which included a higher concentration of 2-furanmethanethiol, and thin-colored salty rice miso, which included a lower concentration of 2-furanmethanethiol, it was shown that the aroma of thin-colored salty rice miso was similar to that of red salty rice miso by adding 2-furanmethanethiol into thin-colored salty rice miso. In addition, a quantitative descriptive analysis (QDA) clearly shows that 2-furanmethanethiol contributed to the intensity of three odor qualities "thick, complex", "sweet", and "pleasant aroma like coffee beans" in six odor qualities and was a very important component of miso aroma.

Long-term storage of Pink Lady apples modifies volatile-involved enzyme activities: consequences on production of volatile esters

Pink Lady apples were harvested at commercial maturity and stored at 1 degrees C and 92% relative humidity under either air or controlled atmosphere conditions (2 kPa O 2:2 kPa CO 2 and 1 kPa O 2:1 kPa CO 2) for 27 weeks. Data on the emission of volatile compounds and on the activity of some related enzymes in both skin and flesh tissues were obtained during subsequent shelf life at 20 degrees C. Major effects of storage atmosphere and poststorage period were observed on the emission of volatile esters and their precursors. Changes in the production of volatile esters were partly due to alterations in the activity of alcohol o-acyltransferase, but the specific esters emitted by fruit after storage also resulted largely from modifications in the supply of the corresponding substrates. Samples stored under air were characterized by higher availability of acetaldehyde, whereas those stored under CA showed enhanced emission of the alcohol precursors ethanol and 1-hexanol (2 kPa O 2) and 1-butanol (1 kPa O 2), with accordingly higher production of ethyl, hexyl, and butyl esters. Multivariate analysis revealed that a large part of the observed differences in precursor availability arose from modifications in the activity of the enzymes considered. Higher pyruvate decarboxylase activity in air-stored fruit possibly accounted for higher acetaldehyde levels in these samples, while storage under 1 kPa O 2 led to significantly decreased lipoxygenase activity and thus to lessened production of 1-hexanol and hexyl esters. Low acetaldehyde availability together with enhanced hydroperoxide lyase and alcohol dehydrogenase levels in these fruits are suggested to have led to higher emission of 1-butanol and butyl esters.

Which impact for beta-damascenone on red wines aroma?

beta-Damascenone, a C-13 norisoprenoid compound, is usually presented as an impact odorant in red wines. Its direct contribution to their aroma was investigated. Both free beta-damascenone and beta-damascenone precursors were isolated from various French red wines and then analyzed by gas chromatography-mass spectrometry, revealing concentrations in the vicinity of 1 and 2 microg/L for free compounds and both forms, respectively. Gas chromatography-olfactometry analyses were also performed on dilutions of both red wine extracts and pure beta-damascenone. The very low detection threshold in olfactometry for this compound explains why it is found at the highest dilution factor in aroma extract dilution analysis methods. Moreover, determination of beta-damascenone's odor thresholds confirmed the huge importance of the matrix: beta-Damascenone is characterized by a very low perception threshold in hydroalcoholic solution as compared to red wine, where it is over 1000-fold higher. In hydroalcoholic solution, beta-damascenone enhanced fruity notes of ethyl cinnamate and caproate and masked the herbaceous aroma of IBMP. Globally, these results suggested that beta-damascenone has more an indirect than a direct impact on red wine aroma.

Bias of Tedlar bags in the measurement of agricultural odorants

Odor regulations typically specify the use of dynamic dilution olfactometery (DDO) as a method to quantify odor emissions, and Tedlar bags are the preferred holding container for grab samples. This study was conducted to determine if Tedlar bags affect the integrity of sampled air from animal operations. Air samples were collected simultaneously in both Tedlar bags and Tenax thermal desorption tubes. Sample sources originated from either a hydrocarbon-free air tank, dynamic headspace chamber (DHC), or swine-production facility, and were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Several background contaminants were identified from Tedlar bags, which included the odorous compounds N,N-dimethyl acetamide (DMAC), acetic acid, and phenol. Samples from the DHC demonstrated that recovery of malodor compounds was dependent on residence time in the Tedlar bag with longer residence time leading to lower recovery. After 24 h of storage, recovery of C3-C6 volatile fatty acids (VFA) averaged 64%, 4-methylphenol and 4-ethylphenol averaged 10%, and indole and 3-methylindole were below the detection limits of GC-MS-O. The odor activity value (OAV) of grab samples collected in Tedlar bags were 33 to 65% lower following 24 h of storage. These results indicate that significant odorant bias occurs when using Tedlar bags for the sampling of odors from animal production facilities.

Gas chromatography-olfactometry

GC-olfactometry (GC-O) refers to the use of human assessors as a sensitive and selective detector for odour-active compounds. The aim of this technique is to determine the odour activity of volatile compounds in a sample extract, and assign a relative importance to each compound. Methods can be classified into three types: detection frequency, dilution to threshold and direct intensity. Dilution to threshold methods measure the potency of odour-active compounds by using a series of extract dilutions, whereas detection frequency and direct-intensity methods measure odour-active compound intensity, or relative importance, in a single concentrated extract. Factors that should be considered to improve the value of GC-O analysis are the extraction method, GC instrument conditions, including the design and operation of the odour port, methods of recording GC-O data and controlling the potential for human assessor bias using experimental design and a trained panel. Considerable emphasis is placed on the requirement for multidimensional GC analysis, and on best practice when using human assessors.