Volatile profiling of high quality hazelnuts (Corylus avellana L.): chemical indices of roasting

Consumer acceptance and sensory perception of roasted American-European hybrid hazelnuts

Interspecific American-European hazelnut (Corylus americana × C. avellana) hybrids are being developed for the Upper Midwest region of the United States, which have potential economic and ecological benefits. Currently, researchers are working on pre-commercialization initiatives to create a local hazelnut industry. However, a lack of knowledge on the sensory characteristics and consumer acceptability of the hybrid hazelnuts have been identified as potential limitations to production. This study investigated consumer responses to hybrid hazelnuts, employing hedonic ratings and check-all-that-apply (CATA) questions. Twelve roasted hazelnut hybrids were subjected to consumer evaluation for liking (aroma, color, flavor, texture, and overall) and aroma and flavor descriptors. Consumers also evaluated two European hazelnut varieties for comparative purposes. Liking scores were significantly different (p < 0.05) across different hybrid varieties and when comparing specific hybrids with European varieties. CATA sensory profiles specific to different varieties were also observed and discriminating attributes were identified using multiple-response methodologies. Penalty analysis based on CATA further identified the attributes roasty, hazelnut-like, caramel-like, chocolate-like, sweet, and salty as primary drivers of aroma/flavor liking, while earthy, burnt, and bitter were identified as primary drivers of disliking. Overall, unique flavors that impacted liking were found in hybrid hazelnuts and, when compared with European hazelnuts, provided insights for breeding and post-processing strategies to optimize product quality.

Metabolic Engineering of Escherichia coli for Production of 2,5-Dimethylpyrazine

2,5-Dimethylpyrazine (2,5-DMP) is a high-value-added alkylpyrazine compound with important applications in both the food and pharmaceutical fields. In response to the increasing consumer preference for natural products over chemically synthesized ones, efforts have been made to develop efficient microbial cell factories for the production of 2,5-DMP. However, the previously reported recombinant strains have exhibited low yields and relied on expensive antibiotics and inducers. In this study, we employed metabolic engineering strategies to develop an Escherichia coli strain capable of producing 2,5-DMP at high levels without the need for inducers or antibiotics. Initially, the biosynthesis pathway of 2,5-DMP was constructed that realized 2,5-DMP production from glucose. Subsequently, efforts focused on enhancing 2,5-DMP production by improving the availability of the cofactor NAD+ and precursor l-threonine. Additionally, the supply and conversion of l-threonine were balanced by optimizing the copy number of the key gene tdh on the chromosome and by modifying the l-threonine transport system. The final engineering strain D19 produced 3.1 g/L of 2,5-DMP, which is the highest titer for fermentative production of 2,5-DMP using glucose as the carbon source up to date. The strategies used in this study lay a good foundation for the production of 2,5-DMP on a large scale.

Artificial Intelligence decision-making tools based on comprehensive two-dimensional gas chromatography data: the challenge of quantitative volatilomics in food quality assessment

Effective investigation of food volatilome by comprehensive two-dimensional gas chromatography with parallel detection by mass spectrometry and flame ionization detector (GC×GC-MS/FID) gives access to valuable information related to industrial quality. However, without accurate quantitative data, results transferability over time and across laboratories is prevented. The study applies quantitative volatilomics by multiple headspace solid phase microextraction (MHS-SPME) to a large selection of hazelnut samples (Corylus avellana L. n = 207) representing the top-quality selection of interest for the confectionery industry. By untargeted and targeted fingerprinting, performant classification models validate the role of chemical patterns strongly correlated to quality parameters (i.e., botanical/geographical origin, post-harvest practices, storage time and conditions). By quantification of marker analytes, Artificial Intelligence (AI) tools are derived: the augmented smelling based on sensomics with blueprint related to key-aroma compounds and spoilage odorant; decision-makers for rancidity level and storage quality; origin tracers. By reliable quantification AI can be applied with confidence and could be the driver for industrial strategies.

Monitoring alkyl pyrazines in roasted hazelnuts by SHS-GC-IMS: IMS response assessment and standardization

Gas chromatography coupled with ion mobility spectrometry (IMS) is an analytical tool which is rapidly becoming widespread in the analysis of food volatiles. Despite this increasing popularity, an assessment of the IMS response for several flavor compound classes is not yet available. This study focuses on alkyl pyrazines and their determination in roasted hazelnut pastes. These Maillard reaction products are crucial to determine the aromatic profile of roasted foods and are suitable markers for industrial roasting monitoring. The instrumental response of 8 alkyl pyrazines was studied using a model matrix and a matrix matching approach. The results showed a relevant effect of the pyrazine ring substitution pattern on the concentration-response curve trends, highlighting that an external standardization of the IMS response is required to make possible relative abundance comparisons between analytes. A response standardization was therefore developed and applied to determine alkyl pyrazines in samples with different roasting intensity and geographical and botanical origin.

MONITORING CHANGES IN THE VOLATILE FRACTION OF ROASTED NUTS AND SEEDS BY USING COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY AND MATRIX TEMPLATES

Static headspace coupled with comprehensive two-dimensional gas chromatography and a flame ionization detector (HS-GC × GC-FID), has been applied to monitor changes in the volatile fraction of commercial edible nuts and seeds (peanuts, almonds, hazelnuts, and sunflower seeds). Effects of the roasting conditions (time, 5-40 min; temperature, 150-170 °C), which were employed under different combinations by using a ventilated oven, on target volatile fraction were examined to identify potential differences in relation to the roasting treatment of raw samples. In addition, reference templates were created, from the HS-GC × GC-FID method, for each of the four food matrices analyzed, and they were applied to characterize the samples according to the presence or absence of volatile compounds. Finally, these templates were successfully employed to make a quick distinction between different roasting conditions.•HS-GC × GC-FID was applied to study the volatile profile of edible nuts and seeds.•Reference templates (GC × GC-FID) were created for each of the four food matrices.•Rapid discrimination between raw and roasted samples was achieved.

Corylus avellana L. Natural Signature: Chiral Recognition of Selected Informative Components in the Volatilome of High-Quality Hazelnuts

The volatile fraction of plant-based foods provides useful functional information concerning sample-related variables such as plant genotype and phenotype expression, pedoclimatic and harvest conditions, transformation/processing technologies, and can be informative about the sensory quality. In this respect, the enantiomeric recognition of the chiral compounds increases the level of information in profiling studies, being the biosynthesis of native compounds often stereo-guided. Chiral native volatiles mostly show an enantiomeric excess that enables origin authentication or support correlation studies between chemical patterns and sensory profiles. This study focuses, for the first time, on the enantiomeric composition of a large set of chiral compounds within the complex volatilome of Corylus avellana L. belonging to different cultivars (Tonda Gentile Romana, Tonda Gentile Trilobata, Anakliuri) and harvested in different geographical areas (Italian and Georgian). Besides native components profiled in raw kernels, volatiles formed after technological treatment (i.e., roasting) are also considered. Headspace solid-phase microextraction combined with enantioselective gas chromatography-mass spectrometry enables the accurate tracking and annotation of about 150 compounds across many samples. The results show that chiral compounds have diagnostic distribution patterns within hazelnut volatilome with cultivar and harvest region playing the major role. Moreover, being some of these chiral molecules also key-aromas, their distribution has a decisive impact on the sensory properties of the product. In particular, the enantiomeric composition of (E)-5-methyl-2-hepten-4-one (filbertone) resulted to be discriminant for origin authentication. The enantiomeric distribution showed, according to literature, an excess of the (S)-enantiomer in both raw and roasted samples volatilome with larger differences in raw samples. The amount of both (R) and (S)-filbertone increases during roasting; the most marked increase for (R)-enantiomer is observed in Italian samples, thus supporting evidence of better hedonic properties and more pleasant odor and aroma.

Corylus avellana L. Aroma Blueprint: Potent Odorants Signatures in the Volatilome of High Quality Hazelnuts

The volatilome of hazelnuts (Corylus avellana L.) encrypts information about phenotype expression as a function of cultivar/origin, post-harvest practices, and their impact on primary metabolome, storage conditions and shelf-life, spoilage, and quality deterioration. Moreover, within the bulk of detectable volatiles, just a few of them play a key role in defining distinctive aroma (i.e., aroma blueprint) and conferring characteristic hedonic profile. In particular, in raw hazelnuts, key-odorants as defined by sensomics are: 2,3-diethyl-5-methylpyrazine (musty and nutty); 2-acetyl-1,4,5,6-tetrahydropyridine (caramel); 2-acetyl-1-pyrroline (popcorn-like); 2-acetyl-3,4,5,6-tetrahydropyridine (roasted, caramel); 3-(methylthio)-propanal (cooked potato); 3-(methylthio)propionaldehyde (musty, earthy); 3,7-dimethylocta-1,6-dien-3-ol/linalool (citrus, floral); 3-methyl-4-heptanone (fruity, nutty); and 5-methyl-(E)-2-hepten-4-one (nutty, fruity). Dry-roasting on hazelnut kernels triggers the formation of additional potent odorants, likely contributing to the pleasant aroma of roasted nuts. Whiting the newly formed aromas, 2,3-pentanedione (buttery); 2-propionyl-1-pyrroline (popcorn-like); 3-methylbutanal; (malty); 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel); dimethyl trisulfide (sulfurous, cabbage) are worthy to be mentioned. The review focuses on high-quality hazelnuts adopted as premium primary material by the confectionery industry. Information on primary and secondary/specialized metabolites distribution introduces more specialized sections focused on volatilome chemical dimensions and their correlation to cultivar/origin, post-harvest practices and storage, and spoilage phenomena. Sensory-driven studies, based on sensomic principles, provide insights on the aroma blueprint of raw and roasted hazelnuts while robust correlations between non-volatile precursors and key-aroma compounds pose solid foundations to the conceptualization of aroma potential.

Roasting intervention for the volatile composition of three varieties of nuts originating from Torreya yunnanensis

For the first time, the volatiles of three varieties of fresh and roasted Torreya yunnanensis nuts were investigated by solid-phase microextraction-gas chromatography-mass spectrometry. The results indicated that roasting had the greatest effect on the volatiles of millet capsules. Fresh nuts had many terpenes, esters, and aldehydes, while roasting led to the formation of pyrazines and furans. In subsequent work, short-term low temperature and small sample area exposed to high temperature had a large effect on the increase in some volatiles and was characterized by a green flavor, such as α-pinene, while ultrahigh-temperature (200 and 230°C) resulted in a decrease in the total volatiles with the generation of unpleasant flavors. Finally, the combination of 170°C for 40 min and slight crushing was found to be the best roasting conditions for samples by means of GC-MS and two-dimensional gas chromatography and time-of-flight mass spectrometry (GC × GC/TOF-MS). PRACTICAL APPLICATIONS: Torreya yunnanensis and its nuts have broad development prospects because of their wide use and rich nutrition. However, inappropriate processing and lack of attention to natural materials such as nuts and wood leads to their poor usage. In addition, volatile compounds make a major contribution to the nut aroma, which is an important indicator of their sensory quality. However, no one has applied roasting technology to Torreya yunnanensis nuts or studied the volatile compounds of the roasted nuts. This study revealed the changes in the composition and content of volatile compounds in Torreya yunnanensis nuts before and after roasting, and the influence of different process points, suggesting that they are key contributors to the development of the related products.

Analysis of Volatiles in Food Products

The evaluation of volatiles in food is an important aspect of food production. It gives knowledge about the quality of foods and their relationship to consumers’ choices. Alcohols, aldehydes, acids, esters, terpenes, pyrazines, and furans are the main chemical groups that are involved in aroma formation. They are products of food processing: thermal treatment, fermentation, storage, etc. Food aroma is a mixture of varied molecules. Because of this, the analysis of aroma composition can be challenging. The four main steps can be distinguished in the evaluation of the volatiles in the food matrix as follows: (1) isolation and concentration; (2) separation; (3) identification; and (4) sensory characterization. The most commonly used techniques to separate a fraction of volatiles from non-volatiles are solid-phase micro-(SPME) and stir bar sorptive extractions (SBSE). However, to study the active components of food aroma by gas chromatography with olfactometry detector (GC-O), solvent-assisted flavor evaporation (SAFE) is used. The volatiles are mostly separated on GC systems (GC or comprehensive two-dimensional GCxGC) with the support of mass spectrometry (MS, MS/MS, ToF–MS) for chemical compound identification. Besides omics techniques, the promising part could be a study of aroma using electronic nose. Therefore, the main assumptions of volatolomics are here described.

Volatile Profile of Nuts, Key Odorants and Analytical Methods for Quantification

The presence of nuts in diets has notably increased due to their composition, and the presence of antioxidants and their unsaturated fatty acid profile has led to a considerable increase in their consumption. The volatile profile of nuts is important from different points of view. It affects consumer’s selection, influences raw material selection for the production of composite foods, dictates variety selection in breeding programs, and, from a quality perspective, its changes can indicate food degradation or alteration. A review of the published bibliography concerning the determination of volatiles in nuts has been carried out. The information retrieved has been divided into four main sections. First, a discussion on the main volatiles present in nuts is performed; next, a revision of the methods used to determine the volatiles is presented; and, finally, two sections describing how harvesting conditions, healthy state and the thermal treatment of nuts modifies their volatile profile are added. Analysis of the published bibliography denoted the complexity of volatile determination and the different variables that can modify the compounds present in the volatile fraction of nuts.

Quantitative Analysis of Pyrazines and Their Perceptual Interactions in Soy Sauce Aroma Type Baijiu

Pyrazines are important compounds in soy sauce aroma type Baijiu (SSAB). In this work, a total of 16 pyrazines were analyzed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS) in SSAB. The quantitative results showed that 2,3,5,6-tetramethylpyrazine, 2,6-dimethylpyrazine and 2,3,5-trimethylpyrazine were the three most concentrated pyrazines. The highest odor activity value (OAV) was determined for 2-ethyl-3,5-dimethylpyrazine. Quantitative analysis combined with descriptive sensory analysis revealed that sub-threshold pyrazines (2,3-dimethylpyrazine, 2,3-diethylpyrazine, 2,3-diethyl-5-methylpyrazine and 2-acetyl-3-methylpyrazine) are significantly correlated with the roasted aroma in SSAB. Our study focused on the impact of sub-threshold pyrazines on the perception of roasted aroma in SSAB. The effect of the sub-threshold pyrazines was detected by the addition of various pyrazines in SSAB samples, despite their sub-threshold concentrations. Furthermore, the presence of sub-threshold pyrazines in dilute alcohol solution resulted in a significant reduction in the odor thresholds of supra-threshold pyrazines. Sensory investigation indicated that pyrazines have a synergistic effect on the perception of roasted aroma. The results highlighted the contribution of some pyrazines to the roasted aroma in SSAB despite their sub-threshold concentrations.

Changes in Volatile Compound Profiles in Cold-Pressed Oils Obtained from Various Seeds during Accelerated Storage

Cold-pressed oils are highly valuable sources of unsaturated fatty acids which are prone to oxidation processes, resulting in the formation of lipid oxidation products, which may deteriorate the sensory quality of the produced oil. The aim of the study was to determine the main volatile compounds which differentiate examined oils and could be used as the markers of lipid oxidation in various oils. In the experiment, cold-pressed oils-brown flaxseed, golden flaxseed, hempseed, milk thistle, black cumin, pumpkin, white poppy seed, blue poppy seed, white sesame, black sesame and argan oils from raw and roasted kernels-were analyzed. To induce oxidative changes, an accelerate storage test was performed, and oils were kept at 60 °C for 0, 2, 4, 7 and 10 days. Volatile compound profiling was performed using SPME-GC-HRToFMS. Additionally, basic measurements such as fatty acid composition, peroxide value, scavenging activity and phenolic compound contents were carried out. Multivariate statistical analyses with volatile compound profiling allow us to differentiate oils in terms of plant variety, oxidation level and seed treatment before pressing. Comparing black cumin cold-pressed oil with other oils, significant differences in volatile compound profiles and scavenging activity were observed. Compounds that may serve as indicators of undergoing oxidation processes in flaxseed, poppy seed, milk thistle and hemp oils were determined.

Comparative analysis of volatile profiles in two grafted pine nuts by headspace-SPME/GC-MS and electronic nose as responses to different roasting conditions

As an attempt to fulfill the massive demand for pine nuts, two grafted trees were cultivated: grafted Pinus koraiensis on the same scions (PK) and grafted Pinus koraiensis on Pinus sylvestris rootstocks (PKS) trees. Both PK and PKS are acknowledged as important economic trees in the northeastern area of China. This study aimed to compare the volatile compounds and aroma profiles in PK and PKS by Headspace Solid Phase Microextraction (HS-SPME) coupled with Gas Chromatography-Mass Spectrometry (GC-MS) and Electronic nose (E-nose) as responses to different roasting conditions. The results showed that a total of 286 volatile compounds were identified in the PK and PKS samples, which some of them were considered to contribute to the desirable aroma of samples. Abundance of terpenes and aromatic hydrocarbons, such as D-limonene and toluene, were respectively present in both raw PK and PKS. The increasing temperature and duration of roasting significantly decreased terpenes and aromatic hydrocarbons content, while more alkanes/alkenes, acids, and ketones were generated in the medium temperature condition. The late phase of roasting was dominated by aldehydes, furans, furfurals, pyrazines, and pyrroles, for which PKS showed a higher content than PK. The aroma profiles detected by E-nose showed that the influence of roasting time was less at high temperatures than those at low and medium temperatures. This study also highlighted the feasibility of principal component analysis (PCA) combined with HS-SPME/GC-MS and E-nose to discriminate the samples.

Adding extra-dimensions to hazelnuts primary metabolome fingerprinting by comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry featuring tandem ionization: Insights on the aroma potential

The information potential of comprehensive two-dimensional gas chromatography combined with time of flight mass spectrometry (GC × GC-TOFMS) featuring tandem hard (70 eV) and soft (12 eV) electron ionization is here applied to accurately delineate high-quality hazelnuts (Corylus avellana L.) primary metabolome fingerprints. The information provided by tandem signals for untargeted and targeted 2D-peaks is examined and exploited with pattern recognition based on template matching algorithms. EI-MS fragmentation pattern similarity, base-peak m/z values at the two examined energies (i.e., 12 and 70 eV) and response relative sensitivity are adopted to evaluate the complementary nature of signals. As challenging bench test, the hazelnut primary metabolome has a large chemical dimensionality that includes various chemical classes such as mono- and disaccharides, amino acids, low-molecular weight acids, and amines, further complicated by oximation/silylation to obtain volatile derivatives. Tandem ionization provides notable benefits including larger relative ratio of structural informing ions due to limited fragmentation at low energies (12 eV), meaningful spectral dissimilarity between 12 and 70 eV (direct match factor values range 222-783) and, for several analytes, enhanced relative sensitivity at lower energies. The complementary information provided by tandem ionization is exploited by untargeted/targeted (UT) fingerprinting on samples from different cultivars and geographical origins. The responses of 138 UT-peak-regions are explored to delineate informative patterns by univariate and multivariate statistics, providing insights on correlations between known precursors and (key)-aroma compounds and potent odorants. Strong positive correlations between non-volatile precursors and odorants are highlighted with some interesting linear trends for: 3-methylbutanal with isoleucine (R² 0.9284); 2,3-butanedione/2,3-pentanedione with monosaccharides (fructose/glucose derivatives) (R² 0.8543 and 0.8860); 2,5-dimethylpyrazine with alanine (R² 0.8822); and pyrroles (1H-pyrrole, 3-methyl-1H-pyrrole, and 1H-pyrrole-2-carboxaldehyde) with ornithine and alanine derivatives (R² 0.8604). The analytical work-flow provides a solid foundation for a new strategy for hazelnuts quality assessment because aroma potential could be derived from precursors' chemical fingerprints.

Elucidation of hulling-induced changes in the aroma and aroma-active compounds of cv. Uzun pistachio (Pistacia vera)

BACKGROUND

The purpose of this study was to define the effects of the hulling process on the aroma and aroma-active composition of cv. Uzun pistachio. Four different hulling processes, namely wet, wet-dry, dry-dry and brine, were applied. In addition, solvent-assisted flavor evaporation (SAFE), simultaneous distillation/extraction (SDE) and purge and trap (P&T) extraction methods were also tested to obtain the best representative aroma extract.

RESULTS

The results revealed that the dry-dry hulling method was the most prominent according to the aroma and aroma-active compounds, and this was especially the case with terpene compounds. The method increased the content of terpenes, pyrazines and total aroma compounds. By application of aroma extract dilution analysis (AEDA), a total of 18 compounds were detected, of which 11 were identified for the first time in the fruit of pistachio. 2,3-Dimethylpyrazine, trimethylpyrazine and 2-ethyl-3,5-dimethylpyrazine were the compounds that had the highest flavour dilution factors.

CONCLUSION

In general, the results of the present research indicated that the hulling method highly affected the overall aroma structure of pistachios. The dry-dry hulling method is therefore suggested to manufacturers to obtain better pistachios with rich and high-quality aroma. © 2019 Society of Chemical Industry.

Filbertone: A Review

This comprehensive review of filbertone, a principal flavor compound of hazelnut, evaluates the current state of the art of all relevant aspects of the title molecule: its occurrence and properties, laboratory preparation and bulk synthesis, analytical issues regarding stereochemistry and purity, sensory evaluation, and practical uses. Comparisons are made between different synthetic approaches, and a critical assessment of various applications is presented.

Artemisia umbelliformis Lam. and Génépi Liqueur: Volatile Profile as Diagnostic Marker for Geographic Origin and To Predict Liqueur Safety

Artemisia umbelliformis, commonly known as "white génépi", is characterized by a volatile fraction rich in α- and β-thujones, two monoterpenoids; under European Union (EU) regulations these are limited to 35 mg/L in Artemisia-based beverages because of their recognized activity on the human central nervous system. This study reports the results of an investigation to define the geographical origin and thujone content of individual plants of A. umbelliformis from different geographical sites, cultivated experimentally at a single site, and to predict the thujone content in the resulting liqueurs through their volatile fraction. Headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and non-separative HS-SPME-MS were used as analytical platforms to create a database suitable for chemometric description and prediction through linear discriminant analysis (LDA). HS-SPME-MS was applied to shorten analysis time. With both approaches, a diagnostic prediction of (i) plant geographical origin and (ii) thujone content of plant-related liqueurs could be made.

Toward a Molecular Understanding of the Typicality of Chardonnay Wines: Identification of Powerful Aromatic Compounds Reminiscent of Hazelnut

Chardonnay wines impart a unique complex aroma characterized by its buttery, yellow stone fruit, melon, bready, and woody notes. Among the terms used in the sensory analysis of these wines, this study investigated hazelnut-like attributes. Multidimensional gas chromatography coupled to olfactometry identified five pyrroles reminiscent of hazelnut: 1-ethylpyrrole-2-carboxaldehyde, 1H-pyrrole, 2-acetyl-1H-pyrrole (first identification in wine), 1-methylpyrrole-2-carboxaldehyde, and 1H-pyrrole-2-carboxaldehyde. Quantitative analyses demonstrated their significantly higher abundance in Chardonnay wines. However, they proved irrelevant in sensory terms, given the low amounts measured in wine compared to their olfactory detection threshold. Nevertheless, the presence of methanethiol derivatives from these pyrroles was investigated in wine. 1-Methylpyrrole-2-methanethiol and 1-ethylpyrrole-2-methanethiol were identified and exhibited hazelnut-like aroma. These compounds, which have not been observed in natural products to date, are potent volatile compounds with detection thresholds of 0.7 and 1.4 ng/L, respectively, in model wine. These findings open up promising perspectives concerning the interpretation of the typical aromatic nuances of some Chardonnay wines.

Characterisation of minor components in vegetable oil by comprehensive gas chromatography with dual detection

The profile of minor compounds, such as alcohols, sterols, free and alkyl fatty acids, waxes, etc., was investigated in different vegetable oils by a comprehensive gas chromatographic system, coupled with a simultaneous dual detection (flame ionisation detector and mass spectrometer) for quantitative and qualitative purposes. Such a system generated a unique two-dimensional chromatogram to be used as a chemical fingerprint. Multi-level information, due not only to a more "comprehensive" preparation technique, but also thanks to the exploitation of a more powerful and sensitive analytical determination allowed the extrapolation of diagnostic information from the minor components profile of different vegetable oils, along with their characteristic profile. Furthermore, an admixture of an extra virgin olive oil with a low amount of sunflower and palm oils was evaluated, attesting to the powerful diagnostic information provided by the proposed approach.

Flavoromics approach in monitoring changes in volatile compounds of virgin rapeseed oil caused by seed roasting

Two varieties of rapeseed (one high oleic - containing 76% of oleic acid, and the other - containing 62% of oleic acid) were used to produce virgin (pressed) oil. The rapeseeds were roasted at different temperature/time combinations (at 140-180°C, and for 5-15min); subsequently, oil was pressed from the roasted seeds. The roasting improved the flavour and contributed to a substantial increase in the amount of a potent antioxidant-canolol. The changes in volatile compounds related to roasting conditions were monitored using comprehensive gas chromatography-mass spectrometry (GC×GC-ToFMS), and the key odorants for the non-roasted and roasted seeds oils were determined by gas chromatography-olfactometry (GC-O). The most important compounds determining the flavour of oils obtained from the roasted seeds were dimethyl sulphide, dimethyltrisulfide, 2,3-diethyl-5-methylpyrazine, 2,3-butenedione, octanal, 3-isopropyl-2-methoxypyrazine and phenylacetaldehyde. For the oils obtained from the non-roasted seeds, the dominant compounds were dimethylsulfide, hexanal and octanal. Based on GC×GC-ToFMS and principal component analysis (PCA) of the data, several compounds were identified that were associated with roasting at the highest temperatures regardless of the rapeseed variety: these were, among others, methyl ketones (2-hexanone, 2-heptanone and 2-octanone).

Formation of DNA adducts in wild-type and transgenic mice expressing human sulfotransferases 1A1 and 1A2 after oral exposure to furfuryl alcohol

Furfuryl alcohol (FFA) is present in many heat-treated foods as a result of its formation via dehydration of pentoses. It is also used legally as a flavouring agent. In an inhalation study conducted in the National Toxicology Program, FFA showed some evidence of carcinogenic activity in rats and mice. FFA was generally negative in conventional genotoxicity assays, which suggests that it may be a non-genotoxic carcinogen. However, it was recently found that FFA is mutagenic in Salmonella strains expressing appropriate sulfotransferases (SULTs), such as human or mouse SULT1A1. The same DNA adducts that were formed by FFA in these strains, mainly N (2)-((furan-2-yl)methyl)-2'-deoxyguanosine (N (2)-MF-dG), were also detected in tissues of FFA-exposed mice and even in human lung specimens. In the present study, a single oral dose of FFA (250 mg/kg body weight) or saline was administered to FVB/N mice and transgenic mice expressing human SULT1A1/1A2 on the FVB/N background. The transgenic mice were used, since human and mouse SULT1A1 substantially differ in substrate specificity and tissue distribution. DNA adducts were studied in liver, kidney, proximal and distal small intestine as well as colon, using isotope-dilution ultra performance liquid chromatography (UPLC-MS/MS). Surprisingly, low levels of adducts that may represent N (2)-MF-dG were detected even in tissues of untreated mice. FFA exposure enhanced the adduct levels in colon and liver, but not in the remaining investigated tissues of wild-type (wt) mice. The situation was similar in transgenic mice, except that N (2)-MF-dG levels were also strongly enhanced in the proximal small intestine. These different results between wt and transgenic mice may be attributed to the fact that human SULT1A1, but not the orthologous mouse enzyme, is strongly expressed in the small intestine.

Fingerprinting of vegetable oil minor components by multidimensional comprehensive gas chromatography with dual detection

The potentiality of a multidimensional comprehensive gas chromatographic (GC × GC) method, employing a simultaneous dual detection (FID and mass spectrometer), to generate peculiar two-dimensional chromatograms to be used as a chemical fingerprint, was investigated to characterize minor compounds in edible oil, particularly olive oil. The best column combination for this application was investigated comparing two column sets (orthogonal or reverse-type), equivalent in terms of theoretical plate number, but differing in stationary phase combination. The apolar × mid-polar set gave a superior separation power, thus was used for further characterization. Different levels of information were extrapolated from the two-dimensional chromatogram. Using the FID, reliable quantification of the alkyl esters fatty acids and waxes was obtained, comparable to the results obtained using the official method, as required by the European legislation. However, thanks to a slight modification of the sample preparation method, the increased separation power obtained using the GC × GC method, and the support of the mass spectrometer detector, further diagnostic information was extrapolated considering the free sterol and tocopherol fractions. In particular, the profiles of extra virgin olive oil samples were compared with a hazelnut oil sample, highlighting that the latter was characterized by a larger number of compounds, completely absent in the extra virgin olive oil samples, which can be used to detect illegal admixtures.

Comprehensive two-dimensional gas chromatography coupled with static headspace sampling to analyze volatile compounds: application to almonds

The hyphenation of static headspace sampling with comprehensive 2D GC equipped with a modulator based on capillary flow technology and a flame ionization detector was used to separate and identify 43 representative target volatile compounds (light hydrocarbons, carbonyls, pyrazines, alcohols, furans, and benzenes) frequently detected in the roasting process of nuts. Five column combinations with differing degrees of orthogonality (one conventional and four inverted phase sets) were tested in order to obtain the best conditions for analyzing these volatile compounds. Optimization of the working conditions for each of the different column combinations was performed by means of a central composite design. The best results in terms of separation and differentiation among the different chemical groups were achieved with a combination of inverted phase columns (first dimension: highly polar, INNOWax; second dimension: mid-polar, ZB-35). Additionally, a reference template was developed to provide an effective and rapid analysis of the target compounds. Finally, the proposed method was successfully employed to identify volatile compounds in raw and roasted almond samples from the Spanish cultivar Largueta.