Comparison of volatile trapping techniques for the comprehensive analysis of food flavourings by Gas Chromatography-Mass Spectrometry

Application of graphite carbon black assisted-laser desorption ionization-mass spectrometry for soy sauce product discrimination

In a previous study, we developed a novel analytical method to directly and simultaneously detect taste- and odor-active compounds using graphite carbon black (GCB)-assisted laser desorption ionization mass spectrometry (LDI-MS). In this study, we aimed to evaluate food quality using a variety of soy sauces using the method to discriminate each product. Graphite carbon black-laser desorption ionization-mass spectrometry allowed the provision of hundreds of MS peaks derived from soy sauces in both positive and negative modes without any tedious sample pretreatments. Principal component analysis using the obtained MS peaks clearly distinguished three soy sauce products based on the manufacturing countries (Japan, China, and India). Moreover, this method identified distinct MS peaks for discrimination, which significantly correlated with their quantitative amounts in the products. Thus, GCB-LDI-MS analysis was established as a simple and rapid technique for food analysis, illustrating the chemical patterns of food products.

Chemosensory of hemp seed oil extracted with hemp seed(Cannabis sativa L.) roasted under various conditions using electronic sensors and GC-MS/Olfactometry

This study analyzed the flavor of six types of hemp seed oil (HSO) extracted with roasted hemp seed (RHS) under various conditions (Raw, 140 °C_9 min, 140 °C_12 min, 160 °C_12 min, 180 °C_6 min). Electronic tongue (E-tongue), electronic nose (E-nose), GC-MS (gas chromatography-mass spectrometry), and GC-O (gas chromatography-olfactometry) were used for HSO flavor analysis. As a result of the E-tongue analysis, the sweetness tends to increase in most samples as roasting. A total of 89 and 77 volatile compounds were detected through E-nose and GC-MS, and the main volatile compounds were identified as Maillard reaction products. A total of 16 odor active compounds were detected in the GC-O analysis, and in the case of 160 ℃_12 min and 180 ℃_6 min, the scent of Roasted hemp seed oil was more dominant than other aroma profiles. The results of this study are basic data on the flavor characteristics of HSO.

Volatile fingerprints of beef cooking methods using sol-gel-based solid-phase microextraction (SPME) and direct analysis in real-time mass spectrometry (DART-MS)

RATIONALE

The aroma profile of food is a complex mixture of volatile compounds that constitutes a major component of the overall eating experience. The food service industry and chefs therefore constantly seek ways to investigate and thereby enhance the aroma profile. Oven cooking, sous vide and pan fry are three cooking methods of beef commonly practised by chefs. Near real-time analysis of volatile compounds from these three cooking methods will provide insight into respective volatile fingerprints and help improve cooking techniques.

METHODS

Volatile compounds from three beef cooking methods were captured using an in-house sol-gel based solid phase microextraction (SPME) method and analysed using direct analysis in real-time mass spectrometry (DART-MS). A volatile organic compound (VOC) standard was used to demonstrate successful implementation of the sol-gel coating technique. Volatile features discriminating the three cooking methods were shortlisted and statistically assessed by univariate and multivariate analyses.

RESULTS

The VOC standard was successfully adsorbed by the sol-gel method and detected by DART-MS. Hierarchical cluster analysis clearly demarcated three beef cooking methods based on their volatile fingerprints. Out of 65 significant features differentiating the cooking methods, 50 were at highest concentrations from pan-fry cooking only, followed by 14 with highest concentrations from oven cooking followed by pan frying. Sous vide followed by pan frying showed lowest concentrations of almost all volatile features.

CONCLUSIONS

The sol-gel-based solid-phase microextraction technique combined with DART-MS was successful in differentiating beef cooking methods based on their volatile fingerprints. A workflow for rapid assessment of the volatile profile from beef cooking methods was established, providing a baseline to further explore volatile profiles from other key ingredients.

Pyrazines in food samples: Recent update on occurrence, formation, sampling, pretreatment and analysis methods

Pyrazines are a class of active aromatic substances existing in various foods. The accumulation of pyrazines has an impact on flavor and quality of food products. This review encompasses the formation mechanisms and control strategies of pyrazines via Maillard reaction (MR), including the new reactants and emerging techniques. Pyrazines characteristics are better understood through the developed sample pretreatments and detection methods. Herein, an in-depth review of pretreatments and analysis methods since 2010 is presented to explore the simple, fast, green, and effective strategies. Sample preparation methods include liquid phase extraction, solid phase extraction, supercritical fluid extraction, and microextraction methods such as liquid phase microextraction, and solid phase microextraction, etc. Detections are made by chromatographic methods, and sensors, etc. Advantages and limitations are discussed and compared for providing insights to further studies.

Spoilage markers for freshwater fish: A comprehensive workflow for non-targeted analysis of VOCs using DHS-GC-HRMS

Changes of volatile organic compounds (VOCs) patterns during 6 days of storage at +4 °C were investigated in different freshwater fish species, namely carp and trout, using dynamic headspace gas chromatography time-of-flight mass spectrometry (DHS-GC-TOFMS). DHS parameters were systematically optimized to establish optimum extraction and pre-concentration of VOCs. Moreover, different sample preparation methods were tested: mincing with a manual meat grinder, as well as mincing plus homogenization with a handheld homogenizer both without and with water addition. The addition of water during sample preparation led to pronounced changes of the volatile profiles, depending on the molecular structure and lipophilicity of the analytes, resulting in losses of up to 98 % of more lipophilic compounds (logP > 3). The optimized method was applied to trout and carp. Trout samples of different storage days were compared using univariate (Mann-Whitney U test, fold change calculation) and multivariate (OPLS-DA) statistics. 37 potential spoilage markers were selected; for 11 compounds identity could be confirmed via measurement of authentic standards and 10 compounds were identified by library spectrum match. 22 compounds were also found to be statistically significant spoilage markers in carp. Merging results of the different statistical approaches, the list of 37 compounds could be narrowed down to the 14 most suitable for trout spoilage assessment. This study comprises a systematic evaluation of the capabilities of DHS-GC coupled to high-resolution (HR) MS for studying spoilage in different freshwater fish species, including a comprehensive data evaluation workflow.

Extractability, selectivity, and comprehensiveness in supercritical fluid extraction of seaweed using ternary mixtures of carbon dioxide, ethanol, and water

It is well-known that an ideal extraction method enabling quantitative analysis should give complete extraction of the target analytes as well as minimal co-extraction of unwanted matrix substances. If the extraction method is part of a nontarget screening protocol, the desired analytes can differ widely in terms of chemical properties. In chromatography, terminologies such as recovery, selectivity, and comprehensiveness are well-established and can easily be determined. However, in extraction, these concepts are much less developed. Hence, the aim of our research is to develop and scrutinize theory in extraction with respect to numerical descriptors for extractability, selectivity, and comprehensiveness. Our approach is based on experiments determining the extractability of target analytes and selected interferences. As a case study, we use a pooled sample of three species of seaweed (Alaria esculenta, Laminaria digitata and Ascophyllum nodosum). Target analytes are β-carotene, fucoxanthin, δ-tocopherol, and phloroglucinol; and selected interferences are carbohydrates, proteins, ash, arsenic, and chlorophyll a. As a "green and clean" extraction technique, supercritical fluid extraction (SFE) using mixtures of CO2, ethanol and water were explored using a design of experiment. The temperature was varied between 40-80°C, and the pressure was held constant at 300 bar. Obtained results clearly demonstrate that highest relative selectivity was achieved with CO2 containing only 5 vol% of ethanol and no water, which primarily enabled high extractability of β-carotene, and yielding an extract free of carbohydrates, proteins, and toxic metals such as arsenic. Best methods for highest extractability of the other target analytes varied quite widely. Analytes requiring the highest water content (fucoxanthin and phloroglucinol), also resulted in the lowest relative selectivity. Maximum relative comprehensiveness was achieved using CO2/ethanol/water (40/55/5, v/v/v) at 70°C and 300 bar. Our study demonstrates the feasibility of using relative quantitative descriptors for extractability, selectivity, and comprehensiveness, in optimization strategies for analytical extractions.

A comparative study on flavor trapping techniques from the viewpoint of odorants of hot-pressed rapeseed oil

Rapeseed oil, as one of the three major vegetable oils in the world, its matrix effect makes the decoding flavor a challenge. Solid-phase microextraction (SPME), SPME-Arrow, headspace stir bar sorptive extraction (HSSE), direct thermal desorption (DTD), and solvent-assisted flavor evaporation (SAFE) were compared based on the odorants in hot-pressed rapeseed oil. Besides, methodological validation for 31 aroma standards was conducted to compare reliability and robustness of these approaches. DTD showed the largest proportion of acids, while the other techniques extracted a majority of nitriles. The highest number of odorants was detected by SAFE (31), followed by HSSE (30), SPME-Arrow (30), SPME (24), and DTD (14). SPME-Arrow showed the best performance in linearity, recovery, and reproducibility followed by SPME, HSSE, DTD, and SAFE. Results reveal the advantages and limitations of diverse methodologies and provide valuable insights for the selection of extraction methods in an oil matrix and flavor decoding.

Chemical sensory investigation in green and roasted beans Coffea arabica L. (cv. Yellow Bourbon) by various brewing methods using electronic sensors

This study investigated the effects of four brewing methods (cold and hot brew, espresso, and cezve) on the chemical sensory properties of green and roasted coffee beans (cv. Yellow Bourbon) extract. The caffeine and chlorogenic acid contents of the coffee were analyzed using HPLC. The taste and volatile aromatic compounds of coffee were analyzed using an electronic tongue and nose, respectively, and the results were analyzed using principal component analysis. For the taste components analyzed using the electronic tongue, the degree of separation was relatively large depending on the extraction method, and the degree of separation was larger depending on roasting for the volatile compounds analyzed using the electronic nose. Our findings provide basic data for the coffee industry. PRACTICAL APPLICATION: The use of an electronic sensor will provide flavor characteristics for four different types of coffee extracted from green beans and roasted beans. In this study, it was confirmed that the extraction method had a greater effect on the taste of coffee, and in the case of the volatile aromatic compounds of coffee, there was a large difference depending on the green beans and roasted beans. Therefore, our findings will provide data based on the sensory properties of coffee.

Omics approaches to understand cocoa processing and chocolate flavor development: A review

The global market of chocolate has increased worldwide during the last decade and is expected to reach a value of USD 200 billion by 2028. Chocolate is obtained from different varieties of Theobroma cacao L, a plant domesticated more than 4000 years ago in the Amazon rainforest. However, chocolate production is a complex process requiring extensive post-harvesting, mainly involving cocoa bean fermentation, drying, and roasting. These steps have a critical impact on chocolate quality. Standardizing and better understanding cocoa processing is, therefore, a current challenge to boost the global production of high-quality cocoa worldwide. This knowledge can also help cocoa producers improve cocoa processing management and obtain a better chocolate. Several recent studies have been conducted to dissect cocoa processing via omics analysis. A vast amount of data has been produced regarding omics studies of cocoa processing performed worldwide. This review systematically analyzes the current data on cocoa omics using data mining techniques and discusses opportunities and gaps for cocoa processing standardization from this data. First, we observed a recurrent report in metagenomics studies of species of the fungi genus Candida and Pichia as well as bacteria from the genus Lactobacillus, Acetobacter, and Bacillus. Second, our analyzes of the available metabolomics data showed clear differences in the identified metabolites in cocoa and chocolate from different geographical origin, cocoa type, and processing stage. Finally, our analysis of peptidomics data revealed characteristic patterns in the gathered data including higher diversity and lower size distribution of peptides in fine-flavor cocoa. In addition, we discuss the current challenges in cocoa omics research. More research is still required to fill gaps in central matter in chocolate production as starter cultures for cocoa fermentation, flavor evolution of cocoa, and the role of peptides in the development of specific flavor notes. We also offer the most comprehensive collection of multi-omics data in cocoa processing gathered from different research articles.

Flavor Profiling Using Comprehensive Mass Spectrometry Analysis of Metabolites in Tomato Soups

Trained sensory panels are regularly used to rate food products but do not allow for data-driven approaches to steer food product development. This study evaluated the potential of a molecular-based strategy by analyzing 27 tomato soups that were enhanced with yeast-derived flavor products using a sensory panel as well as LC-MS and GC-MS profiling. These data sets were used to build prediction models for 26 different sensory attributes using partial least squares analysis. We found driving separation factors between the tomato soups and metabolites predicting different flavors. Many metabolites were putatively identified as dipeptides and sulfur-containing modified amino acids, which are scientifically described as related to umami or having "garlic-like" and "onion-like" attributes. Proposed identities of high-impact sensory markers (methionyl-proline and asparagine-leucine) were verified using MS/MS. The overall results highlighted the strength of combining sensory data and metabolomics platforms to find new information related to flavor perception in a complex food matrix.

Analysis of bacterial and fungal communities in fermented fish (pla-ra) from Northeast Thailand

Our aim was to explore the microbial community composition (bacteria and fungi) of fermented fish (pla-ra) from Northeast Thailand. We also made functional predictions concerning these microbial communities. The association between the microbiota and odor intensity was also analyzed. Fourteen samples of 1-year fermented fish samples derived from seven local markets in Khon Kaen, Northeast Thailand were used. The microbial community composition of each was investigated by sequencing the V1-V9 regions of the 16S rRNA gene (bacteria) and the ITS gene (fungi) using an Illumina MiSeq platform. Functional prediction analysis was conducted through Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) based on the use of the bacterial 16S rRNA gene sequences. The bacterial communities were rich, comprising 402 genera from 28 phyla, including such genera as Tetragenococcus, Staphylococcus, Virgibacillus, Lactobacillus and Lentibacillus. The fungal communities comprised 7 phyla and 60 genera, such as Heterobasidion, Densospora, Exophiala and Monascus. The bacterial community functional analysis revealed an association with six biological metabolic pathway categories (e.g., metabolism, genetic information processing, environmental information processing, cellular processes, organismal systems and human diseases) with 17 subfunctions, showing the richness of bacterial community functions. Odor-association analysis revealed that Brevibacterium, Brachybacterium and Chromohalobacter were more abundant in the weak-odor group, while Noviherbaspirillum was more abundant in the strong-odor group. This study provides a preliminary analysis of pla-ra microbial community structure and function in popular traditional Thai foods. Functional prediction analysis might be helpful to improve our knowledge of the microbiota in fermented fish.

Exploring the Volatiles Released from Roots of Wild and Domesticated Tomato Plants under Insect Attack

Plants produce volatile organic compounds that are important in communication and defense. While studies have largely focused on volatiles emitted from aboveground plant parts upon exposure to biotic or abiotic stresses, volatile emissions from roots upon aboveground stress are less studied. Here, we investigated if tomato plants under insect herbivore attack exhibited a different root volatilome than non-stressed plants, and whether this was influenced by the plant's genetic background. To this end, we analyzed one domesticated and one wild tomato species, i.e., Solanum lycopersicum cv Moneymaker and Solanum pimpinellifolium, respectively, exposed to leaf herbivory by the insect Spodoptera exigua. Root volatiles were trapped with two sorbent materials, HiSorb and PDMS, at 24 h after exposure to insect stress. Our results revealed that differences in root volatilome were species-, stress-, and material-dependent. Upon leaf herbivory, the domesticated and wild tomato species showed different root volatile profiles. The wild species presented the largest change in root volatile compounds with an overall reduction in monoterpene emission under stress. Similarly, the domesticated species presented a slight reduction in monoterpene emission and an increased production of fatty-acid-derived volatiles under stress. Volatile profiles differed between the two sorbent materials, and both were required to obtain a more comprehensive characterization of the root volatilome. Collectively, these results provide a strong basis to further unravel the impact of herbivory stress on systemic volatile emissions.

Experimental rice seed aging under elevated oxygen pressure: Methodology and mechanism

Seed aging during storage results in loss of vigor and germination ability due to the accumulation of damage by oxidation reactions. Experimental aging tests, for instance to study genetic variation, aim to mimic natural aging in a shorter timeframe. As the oxidation rate is increased by elevating the temperature, moisture, and oxygen levels, this study aimed to (1) investigate the effect of experimental rice seed aging by an elevated partial pressure of oxygen (EPPO), (2) elucidate the mechanism of dry-EPPO aging and (3) compare aging under dry-EPPO conditions to aging under traditional moist-controlled deterioration (CD) conditions and to long-term ambient storage. Dry seeds from 20 diverse rice accessions were experimentally aged under EPPO (200 times higher oxygen levels), at 50% relative humidity (RH), along with storage under high-pressure nitrogen gas and ambient conditions as controls. While no decline in germination was observed with ambient storage, there was significant aging of the rice seeds under EPPO storage, with considerable variation in the aging rate among the accessions, with an average decline toward 50% survival obtained after around 21 days in EPPO storage and total loss of germination after 56 days. Storage under high-pressure nitrogen gas resulted in a small but significant decline, by an average of 5% germination after 56 days. In a second experiment, seven rice seed lots were stored under EPPO as compared to a moist-CD test and two different long-term ambient storage conditions, i.e., conditioned warehouse seed storage (CWSS) and traditional rice seed storage (TRSS). Untargeted metabolomics (with identification of lipid and volatile compounds profiles) showed a relatively high increase in levels of oxidized lipids and related volatiles under all four storage conditions. These compounds had a high negative correlation with seed viability, indicating oxidation as a main deteriorating process during seed aging. Correlation analysis indicated that EPPO storage at 50% RH is more related to aging under TRSS at 60% and CD-aging at 75% ERH rather than CWSS at 40% ERH. In conclusion, aging rice seeds under EPPO conditions is a suitable experimental aging method for analyzing variation among seed lots or genotypes for longevity under storage.

Characterization of the Aroma-Active Compounds in Banana (Musa AAA Red green) and Their Contributions to the Enhancement of Sweetness Perception

"Hongmeiren" bananas are popular because of their red peel. Two extraction methods solvent-assisted flavor evaporation and headspace solid-phase microextraction, combined with gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS), were used to analyze the volatile components of "Hongmeiren" bananas. A total of 86 aroma compounds were identified by GC-MS, 62 of which were identified as the major aroma-active compounds with an odor activity value ≥ 1 or modified frequency ≥ 30%. Ethyl (E)-2-butenoate, 4-undecanone, and α-phellandrene were found in bananas for the first time. Sensory experiments showed that eight sweet-associated odorants could significantly achieve the sweetness enhancement effect at 30 g/L sucrose solution by odor-induced changes in taste perception. These experiments suggest that selected odorants can achieve sugar reduction, but with consideration of the sugar concentration. The study of the sweetness enhancement effect of individual compounds provides a more direct theoretical support for sugar reduction in the food industry.

Combination of solid phase microextraction and low energy electron ionisation gas chromatography-quadrupole time-of-flight mass spectrometry to meet the challenges of flavour analysis

The flavour analysis of volatile compounds remains challenging not only because of their diversity in properties and dynamic range, but also due to the high background noise from food matrix constituents. To improve sensitivity and specificity for a multiclass range of compounds, a combination of solid phase micro-extraction (SPME) devices and low energy electron ionisation (LE-EI) was proposed for the analysis of 36 volatile compounds, using coffee as a model matrix. From a pre-evaluation of devices and extraction modes, the combined use of direct immersion-stir bar sorptive extraction and headspace-thin-film SPME (SBSE-TFSPME) was selected to increase compound recovery, and further optimised for extraction temperature (88 °C) and time (110 min). Furthermore, to complement sample preparation by improving method specificity, a LE-EI technique was developed by evaluating the effect of ionisation energy, source temperature, and emission current on the formation of the diagnostic molecular ions and their preservation. This LE-EI method (15 eV, 150 °C, 0.3 μA) was validated with SBSE-TFSPME as a complete workflow in coffee matrices, and was found to possess good repeatability (intra-day RSD: 1.6-7.3 %), intermediate precision (inter-day RSD: 4.1-12.2 %), and linearity (R² > 0.98). Even for complex coffee samples, the method detection limit reached the pg/mL range (e.g. 2,4,5-trimethylthiazole was detected at 15 pg/mL). In conclusion, this study provided insights on the potential of SPME and LE-EI to improve the sensitivity and specificity of analysis for a range of volatile compounds from food and other complex matrices.

From Sampling to Analysis: How to Achieve the Best Sample Throughput via Sampling Optimization and Relevant Compound Analysis Using Sum of Ranking Differences Method?

The determination of an optimal volatile sampling procedure is always a key question in analytical chemistry. In this paper, we introduce the application of a novel non-parametric statistical method, the sum of ranking differences (SRD), for the quick and efficient determination of optimal sampling procedures. Different types of adsorbents (Porapak Q, HayeSep Q, and Carbotrap) and sampling times (1, 2, 4, and 6 h) were used for volatile collections of lettuce (Lactuca sativa) samples. SRD identified 6 h samplings as the optimal procedure. However, 1 or 4 h sampling with HayeSep Q and 2 h sampling with Carbotrap are still efficient enough if the aim is to reduce sampling time. Based on our results, SRD provides a novel way to not only highlight an optimal sampling procedure but also decrease evaluation time.

Metabolomics Reveals Heterogeneity in the Chemical Composition of Green and White Spears of Asparagus (A. officinalis)

Green and white asparagus are quite different crops but can be harvested from the same plant. They have distinct morphological differences due to their mode of cultivation and they are characterised by having contrasting appearance and flavour. Significant chemical differences are therefore expected. Spears from three varieties of both green and white forms, harvested in two consecutive seasons were analysed using headspace GC-MS and LC-MS with an untargeted metabolomic workflow. Mainly C5 and C8 alcohols and aldehydes, and phenolic compounds were more abundant in green spears, whereas benzenoids, monoterpenes, unsaturated aldehydes and steroidal saponins were more abundant in white ones. Previously reported key asparagus volatiles and non-volatiles were detected at similar or not significantly different levels in the two asparagus types. Spatial metabolomics revealed also that many volatiles with known positive aroma attributes were significantly more abundant in the upper parts of the spears and showed a decreasing trend towards the base. These findings provide valuable insights into the metabolome of raw asparagus, the contrasts between green and white spears as well as the different chemical distributions along the stem.

Systematic selection of competing metabolomics methods in a metabolite-sensory relationship study

INTRODUCTION

The relationship between the chemical composition of food products and their sensory profile is a complex association confronting many challenges. However, new untargeted methodologies are helping correlate metabolites with sensory characteristics in a simpler manner. Nevertheless, in the pilot phase of a project, where only a small set of products are used to explore the relationships, choices have to be made about the most appropriate untargeted metabolomics methodology.

OBJECTIVE

To provide a framework for selecting a metabolite-sensory methodology based on: the quality of measurements, the relevance of the detected metabolites in terms of distinguishing between products or in terms of whether they can be related to the sensory attributes of the products.

METHODS

In this paper we introduce a systematic approach to explore all these different aspects driving the choice for the most appropriate metabolomics method.

RESULTS

As an example we have used a tomato soup project where the choice between two sampling methods (SPME and SBSE) had to be made. The results are not always consistently pointing to the same method as being the best. SPME was able to detect metabolites with a better precision, SBSE seemed to be able to provide a better distinction between the soups.

CONCLUSION

The three levels of comparison provide information on how the methods could perform in a follow up study and will help the researcher to make a final selection for the most appropriate method based on their strengths and weaknesses.

Assessment of the contribution of chiral odorants to aroma property of baked green teas using an efficient sequential stir bar sorptive extraction approach

Chiral volatile compounds are known to be distributed in teas at various enantiomeric ratios. However, the performance of each enantiomer, including aroma characteristics, aroma intensities, and contribution to the overall flavor of tea, is still unclear. In this study, aroma characteristics and intensities of 38 volatile enantiomers in standards and baked green teas with chestnut-like aroma and clean aroma were evaluated by an efficient sequential headspace-stir bar sorptive extraction (seq-HS-SBSE) approach combined with the enantioselective gas chromatography-olfactometry/mass spectrometry (Es-GC-O/MS) technique. Moreover, aroma recombination results for the two types of baked green teas using 14 chiral odorants and four achiral odorants indicated that the combinations of the detected odorants mainly contributed to the "floral", "sweet", and "chestnut-like" aromas. R-Linalool simultaneously enhanced the "floral", "sweet", and "chestnut-like" aromas; R-limonene mainly contributed to the "sweet" and "clean" aromas; and S-α-terpineol promoted the "sweet" and "floral" aromas of baked green tea.

Off-flavor in soy drink: Development, optimization, and validation of an easy and fast method to quantify the key odorants

A detailed molecular flavor profile was necessary to understand the low acceptance of soy drink by Western consumers. Accordingly, key odor-active compounds were detected by means of aroma dilution analyses coupled with gas chromatography-mass spectrometry-olfactometry after application of suitable solvent-free volatile extraction techniques. Four quantification methods (standard addition, external calibration, internal standard, and stable isotope dilution assay) were developed and validated to measure the concentrations after direct immersion-stir bar sorptive extraction. The quantitative methods provided correctness between 97% and 111% and precision ranging from 78% to 99% for the 21 key odorants. Considering the advantages to be efficient, easy to perform and cheap, internal standard method was further applied to four commercially available soy drinks in Germany. Correlated to a sensory acceptance test (n = 52) contents of 1-octen-3-one, (E,E)-2,4-decadienal and 2-methoxy-4-vinylphenol were suggested to be linked to the aversion of Western consumers to soy drink.

Characterization of the Aroma Profile and Main Key Odorants of Espresso Coffee

Espresso coffee (EC) is a common coffee preparation technique that nowadays is broadly widespread all over the globe. Its popularity is in part attributed to the intense aroma and pleasant flavor. Many researchers have studied and reviewed the aroma of the coffee, but there is a lack of specific review focused on EC aroma profile even if it is intensively investigated. Thus, the objective of the current review was to summarize the aroma profile of EC and how different preparation variables can affect EC flavor. Moreover, a collection of diverse analytical procedures for volatile analysis was also reported. The findings of this survey showed that the volatile fraction of EC is extremely complex, but just some compounds are responsible for the characteristic aroma of the coffee, such as some aldehyde, ketones, furanones, furans, sulfur compounds, pyrazines, etc. In addition, during preparation, some variables, e.g., temperature and pressure of water, granulometry of the coffee particle, and brew ratio, can also modify the aroma profile of this beverage, and therefore its quality. A better understanding of the aroma fraction of EC and how the preparation variables should be adjusted according to desired EC would assist coffee workers in obtaining a higher quality product.

Untargeted flavor profiling of lager beers by stir bar sorptive extraction -capillary gas chromatography - time-of-flight mass spectrometry: High analytical performance with a green touch

Beer is one of the most popular beverages in the world and its complex flavor is widely appreciated. Beer flavor profiling is important for brewers to optimize beer production and to guarantee odor quality and taste stability of the final products. This is especially the case for pale lager beers that represent the beer type with the largest worldwide production volume. In this study, the combination of stir bar sorptive extraction (SBSE) with capillary gas chromatography (GC) hyphenated to time-of-flight mass spectrometry (TOFMS) was used to perform a detailed aroma profiling of lager beer samples originating from Belgium, The Netherlands, and France. A generic SBSE method was applied resulting in a very broad extraction coverage of odor solutes, while the extraction process is miniaturized, unattended and solventless, meeting green analytical chemistry requirements. Using GC-TOFMS analysis operated in untargeted mode, MS deconvolution and statistical data analysis, with principal component and hierarchical clustering analysis, it was possible to clearly differentiate brands and origins of the beer samples and to identify marker compounds for flavor profiling of these closely related beer samples. An extended database of beer aroma compounds was created. The developed method can be applied in beer quality optimization and quality control in routine laboratories.

Stir bar sorptive extraction of aroma compounds in soy sauce: Revealing the chemical diversity

Fermented soy sauce is used worldwide to enhance the flavour of many dishes. Many types of soy sauce are on the market, and their differences are mostly related to the country of origin, the production process applied and the ratio of ingredients used. Consequently, several aromas, tastes, colours, and textures are obtained. Nowadays, soy sauce can also be produced without microorganisms making the process shorter and cheaper. However, flavour may be lost. We have carried out a comprehensive metabolomics analysis of volatile compounds using stir bar sorptive extraction (SBSE)-GC-MS to relate differences in volatile content to production history and origin. The results revealed major differences between fermented and non-fermented soy sauces, and a list of volatile compounds is reported as being characteristic of each type. This study was able to relate volatiles to the production process using SBSE-GC-MS and to aroma characteristics using GC-O-MS.

Sample Introduction Method in Gas Chromatography

In this review, we summarize the methods of sample introduction into a gas chromatograph. For volatile organic compounds, headspace measurements and purge-trap methods have been used traditionally. Recently, the trapped headspace method has been used in water quality testing. In addition, various solid-state adsorption methods have been developed, including a method in which the adsorbent is placed inside a needle, while new adsorbents and their applications have also been introduced.