A powerful methodological approach combining headspace solid phase microextraction, mass spectrometry and multivariate analysis for profiling the volatile metabolomic pattern of beer starting raw materials

Comprehensive Two-Dimensional Gas Chromatography-Mass Spectrometry as a Tool for the Untargeted Study of Hop and Their Metabolites

Since hop secondary metabolites have a direct correlation with the quality of beer and other hop-based beverages, and the volatile fraction of hop has a complex composition, requiring effective separation, here we explore the application of headspace solid-phase microextraction as a sample preparation method, coupled with comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) analysis. The methodology involved the use of a DVB/PDMS fibre with 500 mg of hop cone powder, extracted for 40 min at 50 °C, for both GC-MS and GC×GC-MS. The varieties Azacca, Cascade, Enigma, Loral, and Zappa were studied comprehensively. The results demonstrate that GC×GC-MS increases the number of peaks by over 300% compared to classical GC-MS. Overall, 137 compounds were identified or tentatively identified and categorised into 10 classes, representing between 87.6% and 96.9% of the total peak area. The composition revealed the highest concentration of sesquiterpene hydrocarbons for Enigma, whilst Zappa showed a relatively significant concentration of monoterpene hydrocarbons. Principal component analysis for all compounds and classes, along with hierarchical cluster analysis, indicated similarities between Zappa and Cascade, and Azacca and Loral. In conclusion, this method presents an optimistic advancement in hop metabolite studies with a simple and established sample preparation procedure in combination with an effective separation technique.

Nutritional and chemical composition of Alpinia zerumbet leaves, a traditional functional food

Alpinia zerumbet, a species of the Zingiberaceae family, is a common plant in tropical and subtropical areas used in traditional medicine to treat various diseases and also included as food in the traditional Okinawan diet (Japan). The leaves and rhizomes of this plant are used as spice and flavoring in foods such as rice, meats, and pasta. Studies of the chemical and nutritional characteristics of fresh leaves and of leaves submitted to thermal treatments such as boiling and steaming are lacking. In the current study, the leaves of A. zerumbet were subjected to boiling or steaming for 10, 20, and 30 min as part of the thermal treatments. The study also provides noteworthy results regarding the proximate composition, physical-chemical data, minerals, phenolic compounds, antioxidant activity, volatile compounds, and LC-MS chromatographic profiles of the extracts produced with fresh leaves and with thermal treatments. The carbohydrate content of A. zerumbet leaves improved during the thermal treatments, showing an increase after steaming (18.86 to 19.79%) and boiling for 30 min (25.85%). After boiling treatment for 20 min, a significant amount of protein was found (6.79%) and all heat treatments resulted in low content of lipid (<1.0%). The boiling treatment for 10 min (BT10) resulted in the highest concentrations of total phenolic components (TPC), 339.5 mg/g, and flavonoids (TF), 54.6 mg/g, among the three thermal treatments (BT10, BT20 and BT30). The results of the steaming treatments (ST 10, 20, and 30 min) differed, with ST20 leading to higher TPC (150.4 mg/g) and TF (65.0 mg/g). The quantity of total phenolics and flavonoids, as well as the antioxidant activity, were significantly affected by the cooking method and the length of time of sample exposure to heat. The samples boiled for 30 and 10 min had higher concentrations of antioxidant activity as measured by the phosphomolybdenum and DPPH methods (151.5 mg/g of extract and 101.5 μg/mL, respectively). Thirty-eight volatile organic compounds (VOCs) were identified by chromatographic analysis of fresh and thermally treated leaves of A. zerumbet. Terpenoids were the predominant class of volatile compounds in the fresh leaves and in all thermal treatments. p-Cymene, 1,8-cineole, 4-terpineol, linalool, α-copaene and β-bisabolene have the greatest impact on overall aroma perception, with odor activity values (OAV) greater than five. Among the phenolic compounds identified by LC-HRMS in the extracts of fresh and thermally treated leaves were proanthocyanidins, (+) catechin, (-) epicatechin, quercetin-3-O-glucoronide, isorhamnetin-3-O-glucoronide, kaempferol-3-O-rutinoside, pinocembrin, alpinetin, pinostrobin, and other compounds. The present results support the traditional use of this plant as a potential food with properties that certainly contribute to health improvement.

Chemical and nutritional characterization of Ambelania duckei (Apocynaceae) an unexplored fruit from the Amazon region

Ambelania duckei Markgr is a species of the Apocynaceae family, native to the Amazon region that is unexplored from a nutritional point of view and studied in relation to its chemical constituents. This work presents an unprecedented study of the proximate composition, lipid profile, a chromatographic analysis, and the antioxidant activity of extracts obtained from the pulp, peel and seeds of the fruit. The results showed that potassium, calcium, and magnesium stood out as the most abundant key minerals in the fruit peel and pulp, with an emphasis on the potassium present in the fruit pulp at 1750.0 mg/100 g. The peel had the highest content of total phenolics (374.86 mg/g), flavonoids (15.54 mg/g), tannins (27.45 mg/g) and O-diphenols (379.36 mg/g; 645.71 mg/g). The antioxidant activity (AA) was highest in the peel compared to the pulp in the DPPH, ABTS, and ORAC tests showing: IC₅₀ of 29.82; 43.67; and 407.13 µg/mL, respectively but a lower activity for the Fe²⁺ chelator. The analysis of the lipid fractions from the peel, pulp, and seeds of the A. duckei fruit resulted in 14 types of fatty acids. The major fatty acids found in the three parts of the fruit were oleic acid (peel, 22.52 %), palmitic acid (pulp, 17.34 %), and linoleic acid (seeds, 47.99 %). The lipid profile and nutritional aspects had a PUFA/SFA ratio (0.4-1.8) in the different parts of the A. duckei fruit; the atherogenic and thrombogenic indexes were higher in the peel (1.23) and pulp (0.62), respectively. The ratio between the hypocholesterolemic and hypercholesterolemic fatty acids (0.5 - 3.8) calculated for the fruit are within the desirable range for a nutritious food. The chromatographic analysis of the volatile organic compounds (VOCs) from the peel and pulp of the fruit, identified 74 VOCs, of which 60.9 % are related to terpenes, and emit notes such as cucumber, green, fatty, floral, and mint, due to the presence of substances with OAVs > 10, especially α-ionone, 1,8-cineole, 2,4-decadienal, and dodecanal. The analysis of the MS and MS/MS spectra of the chromatograms obtained by LC- QTOF-HRMS led to the identification of 26 compounds in the peel, seeds and pulp of A. duckei, such as fatty acids, phenolic acid, flavonoids, proanthocyanidins, alkaloids, and terpenoids. The results show that the pulp of A. duckei has potential as nourishing food and the nutritional and chemical aspects of the peel can be applied to commercial applications.

An Overview of the Application of Multivariate Analysis to the Evaluation of Beer Sensory Quality and Shelf-Life Stability

Achieving beer quality and stability remains the main challenge for the brewing industry. Despite all the technologies available, to obtain a high-quality product, it is important to know and control every step of the beer production process. Since the process has an impact on the quality and stability of the final product, it is important to create mechanisms that help manage and monitor the beer production and aging processes. Multivariate statistical techniques (chemometrics) can be a very useful tool for this purpose, as they facilitate the extraction and interpretation of information from brewing datasets by managing the connections between different types of data with multiple variables. In addition, chemometrics could help to better understand the process and the quality of the product during its shelf life. This review discusses the basis of beer quality and stability and focuses on how chemometrics can be used to monitor and manage the beer quality parameters during the beer production and aging processes.

Carotenoid stability and aroma retention during the post-harvest storage of biofortified maize

BACKGROUND

Maize varieties that are rich in carotenoids have been developed to combat vitamin A deficiency in Sub-Saharan Africa. Unfortunately, after harvest, carotenoids degrade and off-flavor volatiles develop, which affect nutrient intake and consumer acceptance. This study evaluated carotenoid retention and aroma compound stability in provitamin A biofortified maize, variety Pool 8A, as influenced by dry milling and storage in different packaging and temperature conditions.

RESULTS

The lowest amount of total carotenoids was found in flour stored in laminated paper bags at 37 °C (only 16% retention after 180 days), attributable to the high storage temperature and oxygen permeability of the packaging material. No significant effect on carotenoid degradation was found for dry milling, either by rotor mill or freezer mill, but the formation of volatile compounds was significantly (P < 0.05) affected. Volatile compounds such as hexanal, 2-pentylfuran, 1-propanol, 2-heptanone, butyrolactone, limonene, and hexanoic acid were found in different proportions after milling. The highest concentration of hexanal was in flour milled by rotor mill or freezer mill, and stored in laminated paper bags at 37 °C after 180 days, and the lowest concentrations were for flour in aluminium bags and double-layered polyethylene bags stored at 4 °C.

CONCLUSION

Maize flour stored in double-layered polyethylene bags had the highest carotenoid retention and aroma stability. Importantly, the use of these bags is economically feasible in low-income countries. Overall, our results show that effective control of storage conditions is crucial to prevent carotenoid loss and decrease off-odor formation. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Identification of the volatile profiles of 22 traditional and newly bred maize varieties and their porridges by PTR-QiTOF-MS and HS-SPME GC-MS

BACKGROUND

Low adoption of maize varieties bred to address the nutritional needs of the growing African population limits their impact. Aroma is essential in consumer preference, but has hitherto hardly been studied. We analysed the volatile organic compounds of flours and porridges of 22 maize varieties belonging to four nutritionally distinct groups, namely provitamin A maize, quality protein maize, yellow and white maize.

RESULTS

Proton-transfer-reaction quadrupole ion time-of-flight mass spectrometry (PTR-QiTOF-MS) analysis generated 524 mass peaks ranging from 16.007 to 448.089 m/z. Principal component analysis separated the varieties belonging to the four groups. With headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME GC-MS), 48 volatile compounds were identified in maize flour and 21 in maize porridge, including hexane, nonane, pentanoic acid, 1-octen-3-ol, 1-hexanol, hexanal, nonanal, 2-pentylfuran and 2-heptanone. Volatile compounds such as 1,2,4-trimethyl benzene, associated with thermal degradation of carotenoids, increased in the porridge of yellow and provitamin A maize.

CONCLUSION

The results indicate that PTR-QiTOF-MS and HS-SPME GC-MS combined with multivariate analysis are instrumental to study the volatile aroma compounds of different maize varieties.

Contribution of autochthonous microbiota succession to flavor formation during Chinese fermented mandarin fish (Siniperca chuatsi)

Complex microbial metabolism is key to the unique flavor formation of Chinese fermented mandarin fish (Siniperca chuatsi). However, the association between microorganisms and production of specific flavor components during fermentation is unclear. In this study, headspace-solid-phase microextraction-gas chromatography -mass spectrometry was performed to identify flavor components in fermented samples of S. chuatsi, and high-throughput sequencing of 16S rRNA was conducted to identify the diversity and succession of microbial communities. A correlation network model was adopted to predict the relationship between key microorganisms and flavor formation. The results revealed alcohols, nitrogen compounds, aldehydes, and esters as the main flavor components, and three microbial genera (Psychrilyobacter, Fusobacterium, and Acidaminococcus) were closely associated with the production of these components. These microorganisms contributed to formation of characteristic flavor substances such as linalool, trimethylamine, indole, and Geranyl acetate. This study improves the understanding of different roles of microorganisms in flavor formation during mandarin fish fermentation.

Evaluating the effects of temperature and time on heterocyclic aromatic amine profiles in roasted pork using combined UHPLC-MS/MS and multivariate analysis

In this study, ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) combined with principal component analysis (PCA) were used to investigate the effects of process conditions on the profiles of carcinogenic and mutagenic heterocyclic aromatic amine (HAA) in the pork roasted at 175 °C, 200 °C, 225 °C and 250 °C for 10, 15, 20, 25, 30, 35 and 40 min. Twelve HAAs from four categories, including carboline (Norharman, Harman, and Phe-p-1), imidazopyridine (PhIP, 4'-OH-PhIP, DMIP, and 1,5,6-TMIP), imidazoquinoline (IQ, IQ [4,5-b], and MeIQ), and imidazoquinoxaline (MeIQx and 4,8-DiMeIQx), were detected, quantified and used to compose the HAA profiles in roasted pork. After being Analyzed by PCA, the distributions of HAA profiles from different temperature on the PCA score plot demonstrated that there are significant differences among the HAA profiles from different temperatures. The loading plot also showed that PhIP, 4'-OH-PhIP, IQ[4,5-b], and MeIQ were mainly responsible for the difference. The profiles from higher temperature distribute more scattered than the lower ones, illustrating that the time effects on the HAA profiles from higher temperature are stronger than the lower ones. Comparing the score and loading plots of different heating times, the diversities of the HAA profiles at different temperatures increased under prolonged heating because of the changingpyridines levels. The results of PCA that comparing the HAA from different categories displayed that the formation features of four categories HAAs were significantly differed because of their formation discrepancy under low temperatures and short-term roasting. Using HAA profiles as an entirety, these findings obtained in this study are more close to the real process of HAA formation in roasted pork, and make the complex effects of temperature and time on multiple HAA formations more simply to be concluded.

Enlarging Knowledge on Lager Beer Volatile Metabolites Using Multidimensional Gas Chromatography

Foodomics, emergent field of metabolomics, has been applied to study food system processes, and it may be useful to understand sensorial food properties, among others, through foods metabolites profiling. Thus, as beer volatile components represent the major contributors for beer overall and peculiar aroma properties, this work intends to perform an in-depth profiling of lager beer volatile metabolites and to generate new data that may contribute for molecules’ identification, by using multidimensional gas chromatography. A set of lager beers were used as case-study, and 329 volatile metabolites were determined, distributed over 8 chemical families: acids, alcohols, esters, monoterpenic compounds, norisoprenoids, sesquiterpenic compounds, sulfur compounds, and volatile phenols. From these, 96 compounds are reported for the first time in the lager beer volatile composition. Around half of them were common to all beers under study. Clustering analysis allowed a beer typing according to production system: macro- and microbrewer beers. Monoterpenic and sesquiterpenic compounds were the chemical families that showed wide range of chemical structures, which may contribute for the samples’ peculiar aroma characteristics. In summary, as far as we know, this study presents the most in-depth lager beer volatile composition, which may be further used in several approaches, namely, in beer quality control, monitoring brewing steps, raw materials composition, among others.

Decomposing the molecular complexity of brewing

The compositional space of a set of 120 diverse beer samples was profiled by rapid flow-injection analysis (FIA) Fourier transform ion cyclotron mass spectrometry (FTICR-MS). By the unrivaled mass resolution, it was possible to uncover and assign compositional information to thousands of yet unknown metabolites in the beer matrix. The application of several statistical models enabled the assignment of different molecular pattern to certain beer attributes such as the beer type, the way of adding hops and the grain used. The dedicated van Krevelen diagrams and mass difference networks displayed the structural connectivity of the annotated sum formulae. Thereby it was possible to provide a base of knowledge of the beer metabolome far above database-dependent annotations. Typical metabolic signatures for beer types, which reflect differences in ingredients and ways of brewing, could be extracted. Besides, the complexity of isomeric compounds, initially profiled as single mass values in fast FIA-FTICR-MS, was resolved by selective UHPLC-ToF-MS² analysis. Thereby structural hypotheses based on FTICR’s sum formulae could be confirmed. Benzoxazinoid hexosides deriving from the wheat’s secondary metabolism were uncovered as suitable marker substances for the use of whole wheat grains, in contrast to merely wheat starch or barley. Furthermore, it was possible to describe Hydroxymethoxybenzoxazinone(HMBOA)-hexosesulfate as a hitherto unknown phytoanticipin derivative in wheat containing beers. These findings raise the potential of ultrahigh resolution mass spectrometry for rapid quality control and inspection purposes as well as deep metabolic profiling, profound search for distinct hidden metabolites and classification of archeological beer samples.

Beer volatile fingerprinting at different brewing steps

Volatile fingerprints of a lager beer were carried out throughout five brewing steps to characterize the changes encompassing this process. Overall, 60 volatile organic metabolites (VOMs) were identified by headspace solid-phase microextraction followed by gas chromatography mass spectrometry (HS-SPME/GC-MS). Specific profiles were observed at different brewing steps - aldehydes and furans dominate in wort, whereas the aliphatic esters and alcohols predominate in the following steps. Such variations can be assigned to specific VOMs, as 3-methylbutanal (wort), ethyl alcohol and ethyl octanoate (fermentation, maturation and filtration), or ethyl alcohol and isoamyl acetate (final product). These VOMs can influence the beer final flavour. Ethyl alcohol contributes to its strong and pungent smell and taste, while isoamyl acetate adds intense 'fruity' and 'banana' odours. These beer volatile fingerprints constitute a valuable tool to obtain insights on the impact of each brewing step on the final product, being also very useful for certification purposes.

A review on furan: Formation, analysis, occurrence, carcinogenicity, genotoxicity and reduction methods

Furan (C₄H₄O) is a volatile, heterocyclic and carcinogenic heterocyclic chemical compound occurring in a wide range of thermally processed foods. Several studies have been conducted to analyze the formation conditions, triggering furan formation via model systems. Furan can be encountered via various pathways including thermal degradation, oxidation of polyunsaturated fatty acids, thermal rearrangement of carbohydrates in the presence of amino acids, thermal degradation of certain amino acids. Furan has been proven to cause cancer in experimental animal models and classified as a possible human carcinogen by International agency for research on cancer based on sufficient evidences. Thus, different strategies should be developed to reduce furan contents in commercially available food stuffs while food processing. This review summarizes some current evidences of furan formation from different precursors, analytical methods for its detection, and its toxicity that might lead to carcinogenicity and genotoxicity with human risk assessment. In addition, furan occurrence in different thermally processed foods entailed by several recent studies as well as furan mitigation strategies during food processing have also been illustrated in this review.

Floral volatiles identification and molecular differentiation of Osmanthus fragrans by neutral desorption extractive atmospheric pressure chemical ionization mass spectrometry

RATIONALE

Floral volatiles are commonly present only at trace amounts and can be degraded or lost during vapor collection, which is often challenging from the analytical standpoint. Osmanthus fragrans Lour. is a widely cultivated plant known for the highly distinct fragrance of its flowers. The identification of specific volatile organic compounds (VOCs) and molecular differentiation of O. fragrans without any chemical pretreatment and VOC collection are important.

METHODS

Twenty-eight VOCs released by the flowers from ten different cultivars of O. fragrans were identified using neutral desorption extractive atmospheric pressure chemical ionization mass spectrometry (ND-EAPCI-MS) without any chemical pretreatment or VOC collection. Chemical identification was performed by high-resolution MSⁿ analysis and whenever possible was confirmed by the analysis of standards.

RESULTS

According to our literature search, nine of the identified VOCs, 3-buten-2-one, cyclohexadiene, 2-methylfuran, 3-allylcyclohexene, cuminyl alcohol, hotrienol oxide, epoxy-linalool oxide, N-(2-hydroxyethyl) octanamide, and 3-hydroxy-dihydro-β-ionone, have not been reported in O. fragrans in earlier studies. Confident differentiation between ten different cultivars of O. fragrans was achieved by the principal component analysis of the mass spectrometric results.

CONCLUSIONS

The results of our ND-EAPCI-MS analysis substantially increase our knowledge about the chemistry of the O. fragrans floral fragrance and demonstrate the power of this technique for direct molecular profiling for plant recognition or in biotechnological applications.

A review of the analytical methods used for beer ingredient and finished product analysis and quality control

Beer is an incredibly complex beverage containing more than 3000 different compounds, including carbohydrates, proteins, ions, microbes, organic acids, and polyphenols, among others. Beer becomes even more complex during storage, for over time it may undergo chemical changes that negatively affect the flavor, aroma, and appearance. Thus, it can be expected that maintaining the quality of beer throughout its lifetime is a difficult task. Since it is such a popular drink throughout the world, being familiar with proper analytical techniques for beer evaluation is useful for researchers and brewers. These techniques include, but are not limited to, gas chromatography, liquid chromatography, matrix assisted laser desorption/ionization, capillary electrophoresis, mass spectrometry, ultraviolet-visible spectroscopy, and flame ionization detection. This review aims to summarize the various ingredients and components of beer, discuss how they affect the finished product, and present some of the analytical methods used for quality control and understanding the formation of chemicals in beer during the brewing process.

Profiling of volatile flavor compounds in nkui (a Cameroonian food) by solid phase extraction and 2D gas chromatography time of flight mass spectrometry (SPME-GC×GC-TOF-MS)

The objective of this study was to investigate the volatile flavor compounds of nkui, a Cameroonian food, using solid phase microextraction (SPME) and a two-dimensional gas chromatography time of flight mass spectrometry GC×GC-TOF-MS system. Using SPME, volatile compounds were extracted from nkui and analyzed by GC×GC-TOF-MS. The data retrieved revealed the presence of flavor volatiles including acids (20%), alcohols (4%), aldehydes (10%), aromatic compounds (4%), esters (7%), furans (4%), ketones (11%), terpenes and terpernoids (27%). Although the terpene compounds were the most predominant, an ester (linalyl acetate) had the highest percentage of 19%, conferring a sweet, green and citrus flavor. Results obtained from this study suggest that the characteristic flavor of nkui was due to the combination of different volatile flavor compounds, which contributed to its aroma. Considering the medicinal importance of these compounds, their presence positions nkui as a vital food source with health benefits and medicinal properties.

Assessment of the phytochemical profiles of novel hop (Humulus lupulus L.) cultivars: A potential route to beer crafting

This study investigated the volatile phytochemical diversity of 30 samples obtained from experimental hybrid and commercial H. lupulus L. plants. Essential oils distilled from these samples were analysed by high resolution gas chromatography coupled with accurate mass time-of-flight mass spectrometry (GC-accTOFMS). A total of 58 secondary metabolites, mainly comprising 18 esters, 6 monoterpene hydrocarbons, 2 oxygenated monoterpenes, 20 sesquiterpene hydrocarbons, 7 oxygenated sesquiterpenes, and 4 ketones, were positively or tentatively identified. A total of 24 metabolites were detected in all samples, but commercial cultivars (selected for brewing performance) had fewer compounds identified compared to experimental genotypes. Chemometrics analyses enabled distinct differentiation of experimental hybrids from commercial cultivars, discussed in terms of the different classes of compounds present in different genotypes. Differences among the mono- and sesquiterpenoids, appear to be related to either: i) the genetic origin of the plants; or ii) the processes of bioaccumulation of the identified secondary metabolites.

Evaluation of Amazon fruits: chemical and nutritional studies on Borojoa sorbilis

BACKGROUND

Borojoa sorbilis (Ducke) is an Amazonian species with edible fruits that are widely consumed by the local population, but little studied and not yet economically explored. Thus the aim of this study was to describe the chemical composition, volatile compounds, nutritional aspects and antioxidant activity of the fruit pulp and peel of B. sorbilis.

RESULTS

Headspace solid-phase microextraction, using polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber, resulted in the identification of 59 substances in the pulp and peel of B. sorbilis fruits after analysis of the chromatograms obtained by gas chromatography-mass spectrometry using polar and nonpolar columns. Esters were the most abundant. Moisture, lipids, protein, dietary fiber, ash, carbohydrate, total energy value, titratable acid, soluble solids and pH were measured. Protein amount, fat content and antioxidant activity were low in both pulp and peel. Carbohydrate content was 179.2 and 134.9 g kg^-1 in pulp and peel, respectively.

CONCLUSION

This is the first report on the chemical characteristics, flavor and nutritional aspects of B. sorbilis fruit, which is essential to its economic exploitation. The high energy value associated with the carbohydrate content, plus the low fat content, contribute to a possible use of B. sorbilis fruits as a food supplement. © 2018 Society of Chemical Industry.

Forced into aging: Analytical prediction of the flavor-stability of lager beer. A review

Despite years of research, sensory deterioration during beer aging remains a challenge to brewing chemists. Therefore, sensorial and analytical tools to investigate aging flavors are required. This review aims to summarize the available analytical methods and to highlight the problems associated with addressing the flavor-stability of beer. Carbonyls are the major contributors to the aroma of aged pale lager beer, which is especially susceptible to deterioration. They are formed via known pathways during storage, but, as recent research indicates, are mainly released from the bound-state during aging. However, most published studies are based on model systems, and thus the formation and breakdown parameters of these adducts are poorly understood. This concept has not been previously considered in previous forced-aging analysis. Only weak parallels can be drawn between forced and natural aging. This is likely due to the different activation energies of the chemical processes responsible for aging, but may also be due to heat-promoted release of bound aldehydes. Thus, precursors and their binding parameters must be investigated to make appropriate technological adjustments to forced-aging experiments. In combination with sophisticated data analysis, the investigation of volatile indicators and non-volatile precursors can lead to more reliable predictions of flavor stability.

Chemotyping of new hop (Humulus lupulus L.) genotypes using comprehensive two-dimensional gas chromatography with quadrupole accurate mass time-of-flight mass spectrometry

Comprehensive two-dimensional gas chromatography with quadrupole accurate mass time-of-flight mass spectrometry (GC×GC-Q-TOFMS) is employed to profile Humulus lupulus L. (hop) essential oils. Comparison of characterised essential oils allows discrimination among chemotypes. Experimental and commercial hop genotypes displayed distinguishable chemotypic patterns among the volatile secondary metabolites making up their essential oils. In total, 210-306 unique compounds were detected (depending on specific genotype), with 99 of these compounds either positively or tentatively identified. Identified volatile secondary metabolites were grouped into esters, monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes and ketones. Terpenoids were the dominant chemical families across all hop genotypes analysed, representing between 67% and 90% of the total ion count. The multidimensional chromatographic profiles of hop essential oils are extremely information-rich, making GC×GC-Q-TOFMS useful for fast screening of new hybrid hop genotypes, and therefore informing breeding strategies to derive new commercial hop cultivars for the development of distinctive and desirable beers.

Towards a Universal Approach Based on Omics Technologies for the Quality Control of Food

In the last decades, food science has greatly developed, turning from the consideration of food as mere source of energy to a growing awareness on its importance for health and particularly in reducing the risk of diseases. Such vision led to an increasing attention towards the origin and quality of raw materials as well as their derived food products. The continuous advance in molecular biology allowed setting up efficient and universal omics tools to unequivocally identify the origin of food items and their traceability. In this review, we considered the application of a genomics approach known as DNA barcoding in characterizing the composition of foodstuffs and its traceability along the food supply chain. Moreover, metabolomics analytical strategies based on Nuclear Magnetic Resonance (NMR) and Mass Spectroscopy (MS) were discussed as they also work well in evaluating food quality. The combination of both approaches allows us to define a sort of molecular labelling of food that is easily understandable by the operators involved in the food sector: producers, distributors, and consumers. Current technologies based on digital information systems such as web platforms and smartphone apps can facilitate the adoption of such molecular labelling.

New trends in beer flavour compound analysis

As the beer market is steadily expanding, it is important for the brewing industry to offer consumers a product with the best organoleptic characteristics, flavour being one of the key characteristics of beer. New trends in instrumental methods of beer flavour analysis are described. In addition to successfully applied methods in beer analysis such as chromatography, spectroscopy, nuclear magnetic resonance, mass spectrometry or electronic nose and tongue techniques, among others, sample extraction and preparation such as derivatization or microextraction methods are also reviewed.