Influence of Chewing Rate and Food Composition on in Vivo Aroma Release and Perception of Composite Foods

This study investigated the effects of chewing rate and food composition on in vivo aroma release and perception of composite foods. Bread or sponge cake paired with varying sugar content and viscosity strawberry jams, spiked with citral and limonene, were examined. In-nose release was characterized using Proton-Transfer-Reaction-Time-of-Flight-Mass-Spectrometry (PTR-ToF-MS). Simultaneously, Time-Intensity (TI) profiling assessed citrus aroma perception (n = 8, triplicate) while fast and slow chewing protocols were applied (fast: 1.33 chews/s; slow 0.66 chews/s; each for 25 s). Chewing rate did not significantly impact the area under the curve and maximum intensity of in vivo citral and limonene release and citrus aroma perception. Faster chewing rates significantly decreased the time to reach maximum intensity of aroma release (p < 0.05) and citrus aroma perception (p < 0.001). Faster chewing rates probably accelerated structural breakdown, inducing an earlier aroma release and perception without affecting aroma intensity. Adding carriers to jams significantly (p < 0.05) increased aroma release, while perceived citrus aroma intensity significantly (p < 0.05) decreased regardless of chewing rate. In conclusion, chewing rate affects the temporality of in vivo aroma release and perception without affecting its intensity, and carrier addition increases in vivo aroma release while diminishing aroma perception.

Diel rhythm of volatile emissions from males and females of the olive fruit fly Bactrocera oleae using PTR-ToF and GC-MS

The olive fruit fly Bactrocera oleae, is the major key pest of olive groves worldwide. As an odor-driven species, its intraspecific communication has been thoroughly investigated, yielding a combination of spiroacetals, esters and hydrocarbons. However, its management with pheromone is still restricted to olean, the major pheromone component. Given the crucial role of circadian rhythm and pheromone blends in mediating flies reproductive behavior compared to single compounds, B. oleae headspace chemical profile was carefully examined, through the combination of Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF) and Gas Chromatography coupled with Mass Spectrometry (GC-MS). This novel approach aimed at continuously investigating the temporal scale of volatilome profile of B. oleae individuals, as well as the determination of new candidate sex-borne compounds (particularly those emitted in traces or having low molecular weight), that may be relevant to the fly's chemical communication and were unreported due to limitations of frequently used analytical techniques. Our results describe the dynamics and diversity of B. oleae chemical profile, highlighting the emission of 90 compounds, with clear diel rhythm of release, of known pheromone components of B. oleae (e.g., olean, alpha-pinene and muscalure) and new candidates. In contrast to ammonia, acetaldehyde and muscalure, which were highly emitted during the afternoon by males and mixed groups, olean was mostly released by mature females and mixed groups, with a peak of emission during early-morning and afternoon. This emission of olean around dawn is reported for the first time, suggesting early-morning mating activity in B. oleae. Furthermore, esters, such as methyl tetradecanoate, which had been earlier identified as a pheromone for B. oleae, did not exhibit any discernible release patterns. These findings are the first to demonstrate the emission of chemicals, which are only produced when males and females are close to one another, with an emission peak during the afternoon (mating period), and that may have aphrodisiac properties for B. oleae males. These results emphasize the relevance of compounds with distinct diel rhythm and address their potential function as intraspecific messengers, according to their source and timing of release.

Advances in the Application of Direct Injection Mass Spectrometry Techniques to the Analysis of Grape, Wine and Other Alcoholic Beverages

Direct injection mass spectrometry (DIMS) entails the direct introduction of a gaseous sample into a mass analyser without prior treatment or separation. DIMS techniques offer the opportunity to monitor processes in time, with limits of detection as low as 0.5 parts per trillion in volume (for a 1 s measurement time) while providing results with high informational content. This review provides insight into current and promising future developments of DIMS in the analysis of grape, wine and other alcoholic beverages. Thanks to its unique characteristics, DIMS allows the online monitoring of volatile organic compounds (VOCs) released by grapes during fermentative bioprocesses or by wine directly from the glass headspace or during drinking. A DIMS-based approach can also be adopted to perform quality control and high-throughput analysis, allowing us to characterise the volatile profile of large sample sets rapidly and in a comprehensive fashion. Furthermore, DIMS presents several characteristic elements of green analytical chemistry approaches, catalysing an interest linked to the development of sustainable paths in research and development activities in the field of viticulture and oenology.

A Novel Isoprene Synthase from the Monocot Tree Copernicia prunifera (Arecaceae) Confers Enhanced Drought Tolerance in Transgenic Arabidopsis

The capacity to emit isoprene, among other stresses, protects plants from drought, but the molecular mechanisms underlying this trait are only partly understood. The Arecaceae (palms) constitute a very interesting model system to test the involvement of isoprene in enhancing drought tolerance, as their high isoprene emissions may have contributed to make them hyperdominant in neotropical dry forests, characterized by recurrent and extended periods of drought stress. In this study we isolated and functionally characterized a novel isoprene synthase, the gene responsible for isoprene biosynthesis, from Copernicia prunifera, a palm from seasonally dry tropical forests. When overexpressed in the non-emitter Arabidopsis thaliana, CprISPS conferred significant levels of isoprene emission, together with enhanced tolerance to water limitation throughout plant growth and development, from germination to maturity. CprISPS overexpressors displayed higher germination, cotyledon/leaf greening, water usage efficiency, and survival than WT Arabidopsis under various types of water limitation. This increased drought tolerance was accompanied by a marked transcriptional up-regulation of both ABA-dependent and ABA-independent key drought response genes. Taken together, these results demonstrate the capacity of CprISPS to enhance drought tolerance in Arabidopsis and suggest that isoprene emission could have evolved in Arecaceae as an adaptive mechanism against drought.

Online monitoring of higher alcohols and esters throughout beer fermentation by commercial Saccharomyces cerevisiae and Saccharomyces pastorianus yeast

Higher alcohols and esters are among the predominant classes of volatile organic compounds (VOCs) that influence the quality of beer. The concentrations of these compounds are determined through a specific yeast strain selection and fermentation conditions. The effect of yeast strains on the formation of higher alcohols and esters throughout fermentations (at 20°C) was investigated. Flavour-relevant esters (ethyl acetate, isoamyl acetate, ethyl hexanoate and ethyl octanoate) and higher alcohols (isoamyl alcohol, isobutyl alcohol and phenylethyl alcohol) were monitored throughout the fermentation using proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) coupled with an automated sampling system for continuous measurements. Compound identification was confirmed by analysis of samples using gas chromatography-mass spectrometry (GC-MS). Results demonstrated the specific time points where variation in higher alcohol and ester generation between yeast strains occurred. In particular, the concentrations of isoamyl acetate, ethyl octanoate and isoamyl alcohol between yeast strains were significantly different over the first 2 days of fermentation; whereas, after Day 3, no significant differences were observed. The two Saccharomyces pastorianus strains produced comparable concentrations of the key higher alcohols and esters. However, the key higher alcohol and ester concentrations varied greatly between the two S. cerevisiae strains. The use of PTR-ToF-MS to rapidly measure multiple yeast strains provides new insights on fermentation for brewers to modify the sensory profile and optimise quality.

In vivo aroma release and perception of composite foods using nose space PTR–ToF–MS analysis with Temporal-Check-All-That-Apply

In vivo aroma release and perception of complex food matrices have been underexplored. The aims of this study were to investigate the effects of (i) fat and sugar content of chocolate-hazelnut spreads on in vivo aroma release and perception and (ii) carrier addition (bread, wafer) on in vivo aroma release and perception of chocolate-hazelnut spread using dynamic nose space analysis (PTR-ToF-MS) and dynamic sensory analysis (TCATA). Carriers were combined with spreads varying in fat and sugar content and were spiked with five volatile organic compounds (benzaldehyde, filbertone, 2-methylpyrazine, delta-dodecalactone, isovaleraldehyde). TCATA profiles from a consumer panel without in vivo nose space analysis (n = 72) and a trained panel performing in vivo nose space analysis (n = 8, triplicate) were compared. TCATA profiles of the spread-carrier combinations obtained by both panels showed similarly that attributes related to the carriers were perceived at the beginning of consumption, whereas attributes related to the spreads were perceived after swallowing. Significant (p < 0.05) and small differences were observed for the attributes cocoa, creamy, milky, sticky and toffee between both panels. In the evaluated reformulation range, fat and sugar content of chocolate-hazelnut spreads had only a limited effect on in vivo aroma release and perception. In contrast, addition of carriers strongly affected in vivo aroma release and perception for all target molecules. The addition of carriers to spreads generally increased aroma release (duration and intensity of aroma release) and decreased aroma perception. The addition of carriers generally reduced the time to reach maximum intensity compared to when spreads were eaten alone for the five volatile organic compounds while perception decreased. We conclude that the strong effect of carrier addition on in vivo aroma release and perception of chocolate-hazelnut spreads highlights the importance of investigating toppings/spreads accompanied with carriers rather than in isolation.

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.

Co-cultivation of Mortierellaceae with Pseudomonas helmanticensis affects both their growth and volatilome

Volatile organic compounds (VOCs) might mediate microbial interactions, especially in spatially structured environments, such as soil. However, the variety and specificity of VOC production are poorly understood. Here, we studied 25 Mortierellaceae strains belonging to the genera Linnemannia and Entomortierella in both pure and co-culture with Pseudomonas helmanticensis under laboratory conditions. We analysed both the fungal growth depending on co-cultivation and the cultures' volatilomes applying proton-transfer-reaction time-of-flight and gas chromatography-mass spectrometry (PTR-ToF-MS and GC-MS). In a strain-specific manner, we found the fungi's radial growth rate and colony morphology affected by the presence of P. helmanticensis. The fungus seemed to generally reduce the bacterial growth. The volatilomes of the fungal and bacterial pure and co-cultures were diverse. While the fungi frequently consumed VOCs, P. helmanticensis produced a higher diversity and amount of VOCs than any fungal strain. Our results support that both the pure and co-culture volatilomes are taxonomically conserved. Taken together, our data supports the relevance of VOCs in Mortierellaceae-P. helmanticensis interaction. We also discuss individual VOCs that appear relevant in the interaction.

Volatilomics of raspberry fruit germplasm by combining chromatographic and direct-injection mass spectrometric techniques

The application of direct-injection mass spectrometric (DI-MS) techniques, like Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF-MS) has been suggested as a reliable phenotyping tool for fruit volatilome assessment in both genetic and quality-related studies. In this study the complexity of raspberry aroma was investigated by a comprehensive untargeted VOC analysis, done by combining SPME-GC-MS and PTR-ToF-MS assessments with multi-block discriminant analysis using the DIABLO mixOmics framework. The aim was to acquire an exhaustive characterization of the raspberry volatilome according to different fruit ripening stages (pink, ripe, and overripe) and genetic variances (50 accessions), as well as to investigate the potential of PTR-ToF-MS as a rapid and high throughput VOC phenotyping tool to address issues related to raspberry fruit quality. Results of this study demonstrated the complementarity between SPME-GC-MS and PTR-ToF-MS techniques to evaluate the raspberry aroma composition. PTR-ToF-MS generates reliable raspberry VOC fingerprints mainly due to a reduced compound fragmentation and precise content estimation. In addition, the high collinearity between isomers of monoterpenes and norisoprenoids, discovered by GC analysis, reduces the main analytic limitation of PTR-ToF-MS of not being able to separate isomeric molecules. The high similarity between the VOC matrices obtained by applying PTR-ToF-MS and SPME-GC-MS confirmed the possibility of using PTR-ToF-MS as a reliable high throughput phenotyping tool for raspberry volatiolome assessment. In addition, results provided by the germplasm collection investigation enabled to distinguish the best performing accessions, based on VOCs composition, to be used as superior parental lines for future breeding programs.

Comparative transcriptome and metabolite survey reveal key pathways involved in the control of the chilling injury disorder superficial scald in two apple cultivars, 'Granny Smith' and 'Ladina'

The low temperature normally applied to prevent fruit decay during the storage of apples, can also triggers the onset of a chilling injury disorder known as superficial scald. In this work, the etiology of this disorder and the mechanism of action of two preventing strategies, such as the application of 1-MCP (1-methylcyclopropene) and storage at low oxygen concentration in 'Granny Smith' and 'Ladina' apple cultivars were investigated. The metabolite assessment highlighted a reorganization of specific metabolites, in particular flavan-3-ols and unsaturated fatty acids, while the genome-wide transcriptomic analysis grouped the DEGs into four functional clusters. The KEGG pathway and GO enrichment analysis, together with the gene-metabolite interactome, showed that the treatment with 1-MCP prevented the development of superficial scald by actively promoting the production of unsaturated fatty acids, especially in 'Granny Smith'. 'Ladina', more susceptible to superficial scald and less responsive to the preventing strategies, was instead characterized by a higher accumulation of very long chain fatty acids. Storage at low oxygen concentration stimulated a higher accumulation of ethanol and acetaldehyde together with the expression of genes involved in anaerobic respiration, such as malate, alcohol dehydrogenase and pyruvate decarboxylase in both cultivars. Low oxygen concentration, likewise 1-MCP, through a direct control on ethylene prevented the onset of superficial scald repressing the expression of PPO, a gene encoding for the polyphenol oxidase enzyme responsible of the oxidation of chlorogenic acid. Moreover, in 'Granny Smith' apple, the expression of three members of the VII subgroups of ERF genes, encoding for elements coordinating the acclimation process to hypoxia in plants was observed. The global RNA-Seq pattern also elucidated a specific transcriptomic signature between the two cultivars, disclosing the effect of the different genetic background in the control of this disorder.

Ethylene Production Affects Blueberry Fruit Texture and Storability

Ethylene, produced endogenously by plants and their organs, can induce a wide array of physiological responses even at very low concentrations. Nevertheless, the role of ethylene in regulating blueberry (Vaccinium spp.) ripening and storability is still unclear although an increase in ethylene production has been observed in several studies during blueberry ripening. To overcome this issue, we evaluated the endogenous ethylene production of a Vaccinium germplasm selection at different fruit ripening stages and after cold storage, considering also textural modifications. Ethylene and texture were further assessed also on a bi-parental full-sib population of 124 accessions obtained by the crossing between "Draper" and "Biloxi", two cultivars characterized by a different chilling requirement and storability performances. Our results were compared with an extensive literature research, carried out to collect all accessible information on published works related to Vaccinium ethylene production and sensitivity. Results of this study illustrate a likely role of ethylene in regulating blueberry shelf life. However, a generalisation valid for all Vaccinium species is not attainable because of the high variability in ethylene production between genotypes, which is strictly genotype-specific. These differences in ethylene production are related with blueberry fruit storage performances based on textural alterations. Specifically, blueberry accessions characterized by the highest ethylene production had a more severe texture decay during storage. Our results support the possibility of tailoring ad hoc preharvest and postharvest strategies to extend blueberry shelf life and quality according with the endogenous ethylene production level of each cultivar.

Studi sui tratti di qualità negativa nelle nuove viti mediamente resistenti alle malattie fungine

The varieties of vines tolerant to the main fungal diseases are the object of growing interest because they require fewer treatments for the production of quality grapes. These varieties are considered qualitatively unsuitable especially for some characteristics such as the foxy aroma, the level of anthocyanin diglucosides and the level of methyl alcohol in wines. In the three-year period 2016-2018, from a population of 74 medium resistant varieties placed in a single collection, in Marlengo (BZ), young leaves were taken for DNA analysis; annually 2 surveys of the OIV 452 453, 455 and 456 descriptors were carried out, and, at 18° Brix, sombunches were collected for the analysis of different metabolites. Nano-vinifications were carried out for 32 genotypes. Genotypes with different levels of stacked loci associated with resistance to downy and powdery mildew were detected, with different resistance behaviors over the years. Only some genotypes have aromas of foxy and only 20% of the genotypes analyzed have levels of anthocyanin diglucosides higher than the levels required by current legislation. Some vinifications showed methanol levels higher than the legal limit set. High percentages of genotypes respected the legal levels of metabolites required by current regulations and only genotypes with the presence of V. labrusca showed the aroma of foxy.

Exploring volatile organic compound emission from thermally modified wood by PTR-ToF-MS

Thermal modification of wood is a well-known industrial process performed to increase durability and dimensional stability or to change the colour of the natural wood. The treatment influences many other...

Does Organic Farming Increase Raspberry Quality, Aroma and Beneficial Bacterial Biodiversity?

Plant-associated microbes can shape plant phenotype, performance, and productivity. Cultivation methods can influence the plant microbiome structure and differences observed in the nutritional quality of differently grown fruits might be due to variations in the microbiome taxonomic and functional composition. Here, the influence of organic and integrated pest management (IPM) cultivation on quality, aroma and microbiome of raspberry (Rubus idaeus L.) fruits was evaluated. Differences in the fruit microbiome of organic and IPM raspberry were examined by next-generation sequencing and bacterial isolates characterization to highlight the potential contribution of the resident-microflora to fruit characteristics and aroma. The cultivation method strongly influenced fruit nutraceutical traits, aroma and epiphytic bacterial biocoenosis. Organic cultivation resulted in smaller fruits with a higher anthocyanidins content and lower titratable acidity content in comparison to IPM berries. Management practices also influenced the amounts of acids, ketones, aldehydes and monoterpenes, emitted by fruits. Our results suggest that the effects on fruit quality could be related to differences in the population of Gluconobacter, Sphingomonas, Rosenbergiella, Brevibacillus and Methylobacterium on fruit. Finally, changes in fruit aroma can be partly explained by volatile organic compounds (VOCs) emitted by key bacterial genera characterizing organic and IPM raspberry fruits.

Evolution of isoprene emission in Arecaceae (palms)

Isoprene synthase (IspS) is the sole enzyme in plants responsible for the yearly emission in the atmosphere of thousands of tonnes of the natural hydrocarbon isoprene worldwide. Species of the monocotyledonous family Arecaceae (palms) are among the highest plant emitters, but to date no IspS gene from this family has been identified. Here, we screened with PTR-ToF-MS 18 genera of the Arecaceae for isoprene emission and found that the majority of the sampled species emits isoprene. Putative IspS genes from six different genera were sequenced and three of them were functionally characterized by heterologous overexpression in Arabidopsis thaliana, demonstrating that they encode functional IspS genes. Site-directed mutagenesis and expression in Arabidopsis demonstrated the functional relevance of a novel IspS diagnostic tetrad from Arecaceae, whose most variable amino acids could not preserve catalytic function when substituted by a putatively dicotyledonous-specific tetrad. In particular, mutation of threonine 479 likely impairs the open-closed transition of the enzyme by altering the network of hydrogen bonds between helices H1α, H, and I. These results shed new light on the evolution of IspS in monocots, suggesting that isoprene emission is an ancestral trait within the Arecaceae family. The identification of IspS from Arecaceae provides promising novel enzymes for the production of isoprene in heterologous systems and allows the screening and selection of commercially relevant palm varieties with lower environmental impact.

Genetic characterization of an almond germplasm collection and volatilome profiling of raw and roasted kernels

Almond is appreciated for its nutraceutical value and for the aromatic profile of the kernels. In this work, an almond collection composed of 96 Sicilian accessions complemented with 10 widely cultivated cultivars was phenotyped for the production of volatile organic compounds using a proton-transfer time-of-flight mass spectrometer and genotyped using the Illumina Infinium^®18 K Peach SNP array. The profiling of the aroma was carried out on fresh and roasted kernels enabling the detection of 150 mass peaks. Sixty eight, for the most related with sulfur compounds, furan containing compounds, and aldehydes formed by Strecker degradation, significantly increased during roasting, while the concentration of fifty-four mass peaks, for the most belonging to alcohols and terpenes, significantly decreased. Four hundred and seventy-one robust SNPs were selected and employed for population genetic studies. Structure analysis detected three subpopulations with the Sicilian accessions characterized by a different genetic stratification compared to those collected in Apulia (South Italy) and the International cultivars. The linkage-disequilibrium (LD) decay across the genome was equal to r² = 0.083. Furthermore, a high level of collinearity (r² = 0.96) between almond and peach was registered confirming the high synteny between the two genomes. A preliminary application of a genome-wide association analysis allowed the detection of significant marker-trait associations for 31 fresh and 33 roasted almond mass peaks respectively. An accurate genetic and phenotypic characterization of novel germplasm can represent a valuable tool for the set-up of marker-assisted selection of novel cultivars with an enhanced aromatic profile.

Arousal influences olfactory abilities in adults with different degree of food neophobia

Food neophobia, i.e., the aversion to novel foods, and olfaction are both factors strongly affecting food choices. Mounting evidence suggests a higher arousal towards food as a key factor underlying the reluctance to eat what is unfamiliar to us. As the role of olfaction behind this phenomenon is poorly understood, we explored the associations between food neophobia and trait anxiety, olfactory functions (odor threshold, discrimination and identification) and retronasal aroma release from a reference food in a healthy cohort of 83 adult volunteers. We grouped participants in Low-Neophobics or neophilics (n = 35), Medium-Neophobics (n = 32) and High-Neophobics (n = 16) according to the widely recognized Food Neophobia Scale. Participants with higher neophobic tendencies were found to have marginally higher trait anxiety levels than neophilics (p = 0.10). A lower global olfactory functioning and odor discrimination abilities characterized High-Neophobics, while Medium-Neophobics showed a higher odor sensitiveness than Low-Neophobics. Lastly, High-Neophobics showed a lower extent of retronasal aroma release, likely due to a shorter duration of oral processing and higher anxiety-related physiological responses (such as breathing rate). In summary, this study supports the assumption that the conflicting relationship that neophobics have with food may be led by higher levels of arousal toward foods, rather than different chemosensory functions.

Rapid Profiling of the Volatilome of Cooked Meat by PTR-ToF-MS: Underlying Latent Explanatory Factors

Volatile organic compounds (VOCs) are important contributors to meat aroma and are variably correlated with each other. To study the sources of variation and the correlations among meat VOCs, meat cuts from five animal species/categories (chicken, turkey, pork, veal, and beef; two animals/species/retailer: 100 meat cuts) were obtained by 10 retailers. Each cut was processed into four burgers, two of which were grilled and two were cooked in a water bath (400 meat burgers). VOCs were detected by Proton-Transfer-Reaction Time-of-Flight Mass-Spectrometry (PTR-ToF-MS). From these, 129 peaks were selected, of which 72 were tentatively identified as relevant VOCs. Pearson correlations revealed a large number of positive and negative relationships among the VOCs. A multivariate statistical analysis revealed that 87% of the matrix covariance was explained by 17 independent Latent Explanatory Factors (LEFs), which have been described and characterized. LEFs identified may be valuable tools for reducing the dimensionality of results from VOC analyses and can be useful for better understanding and interpreting the variation in the meat aroma profile, although further study is required to characterize their sensory meaning.

Real-Time Monitoring of Volatile Compounds Losses in the Oven during Baking and Toasting of Gluten-Free Bread Doughs: A PTR-MS Evidence

Losses of volatile compounds during baking are expected due to their evaporation at the high temperatures of the oven, which can lead to a decrease in the aroma intensity of the final product, which is crucial for gluten-free breads that are known for their weak aroma. Volatiles from fermentation and lipids oxidation are transferred from crumb to crust, and they flow out to the air together with Maillard and caramelisation compounds from the crust. In this study, the release to the oven of volatile compounds from five gluten-free breads (quinoa, teff and rice flours, and corn and wheat starches) and wheat bread during baking and toasting was measured in real-time using proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS). Baking showed different volatile release patterns that are described by bell-shaped curves, plateaus and exponential growths. Flour-based breads had the higher overall volatile release during baking, but also high ratios in the final bread, while starch-based breads showed high pyrazine releases due to moisture losses. Meanwhile, toasting promoted the release of volatile compounds from the bread matrix, but also the additional generation of volatiles from Maillard reaction and caramelisation. Interestingly, gluten-free breads presented higher losses of volatiles during baking than wheat bread, which could partially explain their weaker aroma.

Unveiling the Molecular Basis of Mascarpone Cheese Aroma: VOCs analysis by SPME-GC/MS and PTR-ToF-MS

Mascarpone, a soft-spread cheese, is an unripened dairy product manufactured by the thermal-acidic coagulation of milk cream. Due to the mild flavor and creamy consistency, it is a base ingredient in industrial, culinary, and homemade preparations (e.g., it is a key constituent of a widely appreciated Italian dessert ‘Tiramisù’). Probably due to this relevance as an ingredient rather than as directly consumed foodstuff, mascarpone has not been often the subject of detailed studies. To the best of our knowledge, no investigation has been carried out on the volatile compounds contributing to the mascarpone cheese aroma profile. In this study, we analyzed the Volatile Organic Compounds (VOCs) in the headspace of different commercial mascarpone cheeses by two different techniques: Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry (HS-SPME GC-MS) and Proton-Transfer Reaction-Mass Spectrometry coupled to a Time of Flight mass analyzer (PTR-ToF-MS). We coupled these two approaches due to the complementarity of the analytical potential—efficient separation and identification of the analytes on the one side (HS-SPME GC-MS), and effective, fast quantitative analysis without any sample preparation on the other (PTR-ToF-MS). A total of 27 VOCs belonging to different chemical classes (9 ketones, 5 alcohols, 4 organic acids, 3 hydrocarbons, 2 furans, 1 ester, 1 lactone, 1 aldehyde, and 1 oxime) have been identified by HS-SPME GC-MS, while PTR-ToF-MS allowed a rapid snapshot of volatile diversity confirming the aptitude to rapid noninvasive quality control and the potential in commercial sample differentiation. Ketones (2-heptanone and 2-pentanone, in particular) are the most abundant compounds in mascarpone headspace, followed by 2-propanone, 2-nonanone, 2-butanone, 1-pentanol, 2-ethyl-1-hexanol, furfural and 2-furanmethanol. The study also provides preliminary information on the differentiation of the aroma of different brands and product types.

Development of a Novel Phenotypic Roadmap to Improve Blueberry Quality and Storability

Improved fruit quality and prolonged storage capability are key breeding traits for blueberry (Vaccinium spp.) fruit. Until now, breeding selection was mostly oriented on the amelioration of agronomic traits, such as flowering time, chilling requirement, or plant structure. Up until now, however, the storage effect on fruit quality has not been extensively studied, mostly because objective and handy phenotyping tools to evaluate quality traits were not available. In this study we are proposing a novel phenotyping protocol to support breeding selection and quality control within the entire blueberry production chain. Volatile organic compounds (VOCs) and texture traits, were measured by Proton Transfer Reaction- Time of Flight- Mass Spectrometry (PTR-ToF-MS) and a texture analyzer respectively, taking into consideration the influence of prolonged storage. The exploitation of the genetic variability existing within the investigated blueberry germplasm collection (including both southern and northern highbush, hybrids, and rabbiteyes) allowed the identification of the best performing cultivars, based on texture and VOCs variability, to be used as superior parental lines for future breeding programs. The comprehensive characterization of blueberry aroma allowed the identification of a wide array of spectrometric features, mostly related to aldehydes, alcohols, terpenoids, and esters, that can be used as putative biomarkers to rapidly evaluate the blueberry aroma variations related to genetic differences and storability. In addition, this study revealed a lack of straightforward relationship between harvest and postharvest quality features, that might be genotype-dependent.

Simultaneous Proton Transfer Reaction-Mass Spectrometry and electronic nose study of the volatile compounds released by Plasmodium falciparum infected red blood cells in vitro

The discovery that Volatile Organic Compounds (VOCs) can be biomarkers for several diseases has led to the conception of their possible application as diagnostic tools. In this study, we aimed at defining of diagnostic signatures for the presence of malaria transmissible stages in infected individuals. To do this, we compared VOCs released by asexual and sexual stage cultures of Plasmodium falciparum, the deadliest species of malaria, with those emitted by uninfected red blood cells (RBCs). VOC analysis was carried out with an innovative set-up, where each sample was simultaneously analysed by proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS) and an electronic nose. PTR-Tof-MS results show that sexual stages are characterized by a larger emission of hexanal, compared with uninfected or asexual stage-infected RBCs, which makes them clearly identifiable. PTR-Tof-MS analysis also detected differences in VOC composition between asexual stages and uninfected RBCs. These results have been substantially replicated by the electronic nose analysis and may open the possibility to develop sensitive and easy-to-use devices able to detect sexual parasite stages in infected individuals. This study also demonstrates that the combination of mass spectrometry with electronic noses is a useful tool to identify markers of diseases and to support the development of optimized sensors.

Rapid and noninvasive quality control of anhydrous milk fat by PTR-MS: The effect of storage time and packaging

In this study, proton transfer reaction-mass spectrometry (PTR-MS), coupled with a time-of-flight mass analyzer and a multipurpose automatic sampler, was evaluated as a rapid and nondestructive tool for the quality control of anhydrous milk fat. Anhydrous milk fats packed in cardboard and bag-in-box were compared during refrigerated shelf life at 4°C for 9 months. Anhydrous milk fat samples were taken at 120, 180, and 240 days and measured by PTR-MS during storage at 50°C for 11 days. Univariate and multivariate data analysis were performed in order to classify samples according to the packaging type and compare aromatic profiles. Markers related to both packaging and storage duration were identified, and all stored samples were clearly distinguishable from reference fresh samples. Significant differences in some key butter aroma compounds such as 2-pentanone, 2-heptanone, 2/3-methylbutanal, acetoin, and butanoic acid were observed between different types of packaging. During the refrigerated storage, differences related to packaging are more evident, while during the storage at 50°C, the fat oxidation induced by the high temperature becomes the most relevant phenomenon independently of the packaging type. These results indicate the importance of avoiding anhydrous milk fat storage at 50°C for long times during industrial production processes. All together data demonstrated the viability of PTR-MS as a rapid and high-sensitivity tool in agroindustry quality control program.

In situ riboflavin fortification of different kefir-like cereal-based beverages using selected Andean LAB strains

Cereal-based functional beverages represent social, economic, and environmental sustainable opportunities to cope with emerging trends in food consumption and global nutrition. Here we report, for the first time, the polyphasic characterization of three cereal-based kefir-like riboflavin-enriched beverages, obtained from oat, maize and barley flours, and their comparison with classical milk-based kefir. The four matrices were successfully fermented with commercial starters: i) milk-kefir and ii) water-kefir, proving the potential of cereal ingredients in the formulation of dairy-like fermented beverages with milk-kefir starter behavior better in these matrices. In the light of their potentiality, seven riboflavin-producing Andean Lactic Acid Bacteria (LAB) were tested for tolerance to food stresses commonly encountered during food fermentation. Moreover, the LAB strains investigated were screened for spontaneous riboflavin overproducing derivatives. Lactobacillus plantarum M5MA1-B2 with outstanding response to stress, was selected to improve riboflavin content in an in situ fortification approach. The combination of L. plantarum M5MA1-B2 riboflavin overproducing strain with milk kefir starter in oat, lead to cover, for one serving of 100 g, 11.4% of Recommended Dietary Allowance (RDA). Besides, addition of L. plantarum M5MA1-B2 improved performance of water kefir in oat and maize matrices. Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) analysis provided the on-line Volatile Organic Compounds profiles supporting the best combination of starter, LAB and cereal matrix for novel functional foods development.

The influence of cadmium and essential nanometals on the physiological And biochemical parameters of lettuce plants

Due to the aim the effect of pre-sowing treatment with a nonionic colloidal solution of the mix of copper, zinc, manganese and iron nanoparticles, cadmium ions and their combined action on the physiological and biochemical indices: the content of lipid peroxidation products and balance of photosynthetic pigments in green Lolo and red Lolo Ross varieties of Lactuca sativa L. was investigated. Spectrophotometric methods of investigating the content of peroxides, thiobarbiturate-active products (with use of the modified Kumar and Knowles method), as well as the content of the main photosynthetic pigments (chlorophyll a, b, a/b ratio, and the carotenoid content) with the Wintermans, de Mots calculations application were used. Due to the results, a decrease in the content of peroxides and growth of malonic dialdehyde was observed for most treatment variants of Lolo. The opposite tendency was observed for the Ross variety (the initial growth of these parameters under the nanoparticles influence decreased to the control during the fourteen-day exposure). The decrease of chlorophyll content was observed In the Lolo variety under the essential metal nanoparticles influence, in contrast to the action of cadmium.For the Ross variety, a significant reduction of both chlorophyll and carotenoid contents in all treatment types during exposure was calculated.The a/b-index for Lolo plants has significantly increased in variants of cadmium influence, for Ross plants the divergence of the influence of all treatment variants has been marked. As a result, the treatment with a mixture of essential nanometals showed additive stress-loading functions. It was observed in a growth of the level of lipid peroxidation products and the reduction of the photosynthetic pigment biomarkers in both varieties during the 0,1 mM cadmium exposure. The Lolo Ross variety showed a higher variability of results under different treatment, compared to the Lolo variety.

Diel rhythms in the volatile emission of apple and grape foliage

This study investigated the diel emission of volatile organic compounds (VOCs) from intact apple (Malus x domestica Borkh., cv. Golden Delicious) and grape (Vitis vinifera L., cv. Pinot Noir) foliage. Volatiles were monitored continuously for 48 h by proton transfer reaction - time of flight - mass spectrometry (PTR-ToF-MS). In addition, volatiles were collected by closed-loop-stripping-analysis (CLSA) and characterized by gas chromatography-mass spectrometry (GC-MS) after 1 h and again 24 and 48 h later. Fourteen and ten volatiles were characterized by GC-MS in apple and grape, respectively. The majority of these were terpenes, followed by green leaf volatiles, and aromatic compounds. The PTR-ToF-MS identified 10 additional compounds and established their diel emission rhythms. The most abundant volatiles displaying a diel rhythm included methanol and dimethyl sulfide in both plants, acetone in grape, and mono-, homo- and sesquiterpenes in apple. The majority of volatiles were released from both plants during the photophase; whereas methanol, CO₂, methyl-butenol and benzeneacetaldehyde were released at significantly higher levels during the scotophase. Acetaldehyde, ethanol, and some green leaf volatiles showed distinct emission bursts in both plants following the daily light switch-off. These new results obtained with a combined analytical approach broaden our understanding of the rhythms of constitutive volatile release from two important horticultural crops. In particular, diel emission of sulfur and nitrogen-containing volatiles are reported here for the first time in these two crops.

PTR-ToF-MS Coupled with an Automated Sampling System and Tailored Data Analysis for Food Studies: Bioprocess Monitoring, Screening and Nose-space Analysis

Proton Transfer Reaction (PTR), combined with a Time-of-Flight (ToF) Mass Spectrometer (MS) is an analytical approach based on chemical ionization that belongs to the Direct-Injection Mass Spectrometric (DIMS) technologies. These techniques allow the rapid determination of volatile organic compounds (VOCs), assuring high sensitivity and accuracy. In general, PTR-MS requires neither sample preparation nor sample destruction, allowing real time and non-invasive analysis of samples. PTR-MS are exploited in many fields, from environmental and atmospheric chemistry to medical and biological sciences. More recently, we developed a methodology based on coupling PTR-ToF-MS with an automated sampler and tailored data analysis tools, to increase the degree of automation and, consequently, to enhance the potential of the technique. This approach allowed us to monitor bioprocesses (e.g. enzymatic oxidation, alcoholic fermentation), to screen large sample sets (e.g. different origins, entire germoplasms) and to analyze several experimental modes (e.g. different concentrations of a given ingredient, different intensities of a specific technological parameter) in terms of VOC content. Here, we report the experimental protocols exemplifying different possible applications of our methodology: i.e. the detection of VOCs released during lactic acid fermentation of yogurt (on-line bioprocess monitoring), the monitoring of VOCs associated with different apple cultivars (large-scale screening), and the in vivo study of retronasal VOC release during coffee drinking (nosespace analysis).

Genome-wide association study unravels the genetic control of the apple volatilome and its interplay with fruit texture

Fruit quality represents a fundamental factor guiding consumers' preferences. Among apple quality traits, volatile organic compounds and texture features play a major role. Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS), coupled with an artificial chewing device, was used to profile the entire apple volatilome of 162 apple accessions, while the fruit texture was dissected with a TAXT-AED texture analyzer. The array of volatile compounds was classed into seven major groups and used in a genome-wide association analysis carried out with 9142 single nucleotide polymorphisms (SNPs). Marker-trait associations were identified on seven chromosomes co-locating with important candidate genes for aroma, such as MdAAT1 and MdIGS. The integration of volatilome and fruit texture data conducted with a multiple factor analysis unraveled contrasting behavior, underlying opposite regulation of the two fruit quality aspects. The association analysis using the first two principal components identified two QTLs located on chromosomes 10 and 2, respectively. The distinction of the apple accessions on the basis of the allelic configuration of two functional markers, MdPG1 and MdACO1, shed light on the type of interplay existing between fruit texture and the production of volatile organic compounds.

Non-invasive real time monitoring of yeast volatilome by PTR-ToF-MS

INTRODUCTION

Producing a wide range of volatile secondary metabolites Saccharomyces cerevisiae influences wine, beer, and bread sensory quality and hence selection of strains based on their volatilome becomes pivotal. A rapid on-line method for volatilome assessing of strains growing on standard solid media is still missing.

OBJECTIVES

Methodologically, the aim of this study was to demonstrate the automatic, real-time, direct, and non-invasive monitoring of yeast volatilome in order to rapidly produce a robust large data set encompassing measurements relative to many strains, replicates and time points. The fundamental scope was to differentiate volatilomes of genetically similar strains of oenological relevance during the whole growing process.

METHOD

Six different S. cerevisiae strains (four meiotic segregants of a natural strain and two laboratory strains) inoculated onto a solid medium have been monitored on-line by Proton Transfer Reaction-Time-of-Flight-Mass Spectrometry for 11 days every 4 h (3540 time points). FastGC PTR-ToF-MS was performed during the stationary phase on the 5th day.

RESULTS

More than 300 peaks have been extracted from the average spectra associated to each time point, 70 have been tentatively identified. Univariate and multivariate analyses have been performed on the data matrix (3640 measurements × 70 peaks) highlighting the volatilome evolution and strain-specific features. Laboratory strains with opposite mating type, and meiotic segregants of the same natural strain showed significantly different profiles.

CONCLUSIONS

The described set-up allows the on-line high-throughput screening of yeast volatilome of S. cerevisiae strains and the identification of strain specific features and new metabolic pathways, discriminating also genetically similar strains, thus revealing a novel method for strain phenotyping, identification, and quality control.

Exploring Blueberry Aroma Complexity by Chromatographic and Direct-Injection Spectrometric Techniques

Blueberry (Vaccinium spp.) fruit consumption has increased over the last 5 years, becoming the second most important soft fruit species after strawberry. Despite the possible economic and sensory impact, the blueberry volatile organic compound (VOC) composition has been poorly investigated. Thus, the great impact of the aroma on fruit marketability stimulates the need to step forward in the understanding of this quality trait. Beside the strong effect of ripening, blueberry aroma profile also varies due to the broad genetic differences among Vaccinium species that have been differently introgressed in modern commercial cultivars through breeding activity. In the present study, divided into two different activities, the complexity of blueberry aroma was explored by an exhaustive untargeted VOC analysis, performed by two complementary methods: SPME-GC-MS (solid phase microextraction- gas chromatography-mass spectrometry) and PTR-ToF-MS (proton transfer reaction-time of flight-mass spectrometry). The first experiment was aimed at determining the VOC modifications during blueberry ripening for five commercially representative cultivars ("Biloxi," "Brigitta Blue," "Centurion," "Chandler," and "Ozark Blue") harvested at four ripening stages (green, pink, ripe, and over-ripe) to outline VOCs dynamic during fruit development. The objective of the second experiment was to confirm the analytical capability of PTR-ToF-MS to profile blueberry genotypes and to identify the most characterizing VOCs. In this case, 11 accessions belonging to different Vaccinium species were employed: V. corymbosum L. ("Brigitta," "Chandler," "Liberty," and "Ozark Blue"), V. virgatum Aiton ("Centurion," "Powder Blue," and "Sky Blue"), V. myrtillus L. (three wild genotypes of different mountain locations), and one accession of V. cylindraceum Smith. This comprehensive characterization of blueberry aroma allowed the identification of a wide pull of VOCs, for the most aldehydes, alcohols, terpenoids, and esters that can be used as putative biomarkers to rapidly evaluate the blueberry aroma variations related to ripening and/or senescence as well as to genetic background differences. Moreover, the obtained results demonstrated the complementarity between chromatographic and direct-injection mass spectrometric techniques to study the blueberry aroma.

Emission of Volatile Compounds from Apple Plants Infested with Pandemis heparana Larvae, Antennal Response of Conspecific Adults, and Preliminary Field Trial

This study investigated the volatile emission from apple (Malus x domestica Borkh., cv. Golden Delicious) foliage that was either intact, mechanically-damaged, or exposed to larval feeding by Pandemis heparana (Denis and Schiffermüller) (Lepidoptera: Tortricidae). Volatiles were collected by closed-loop-stripping-analysis and characterized by gas chromatography-mass spectrometry in three time periods: after 1 h and again 24 and 48 h later. Volatiles for all treatments also were monitored continuously over a 72-h period by the use of proton transfer reaction - time of flight-mass spectrometry (PTR-ToF-MS). In addition, the volatile samples were analyzed by gas chromatography-electroantennographic detection (GC-EAD) using male and female antennae of P. heparana. Twelve compounds were detected from intact foliage compared with 23 from mechanically-damaged, and 30 from P. heparana-infested foliage. Interestingly, six compounds were released only by P. heparana-infested foliage. The emission dynamics of many compounds measured by PTR-ToF-MS showed striking differences according to the timing of herbivory and the circadian cycle. For example, the emission of green leaf volatiles began shortly after the start of herbivory, and increased over time independently from the light-dark cycle. Conversely, the emission of terpenes and aromatic compounds showed a several-hour delay in response to herbivory, and followed a diurnal rhythm. Methanol was the only identified volatile showing a nocturnal rhythm. Consistent GC-EAD responses were found for sixteen compounds, including five aromatic ones. A field trial in Sweden demonstrated that benzyl alcohol, 2-phenylethanol, phenylacetonitrile, and indole lures placed in traps were not attractive to Pandemis spp. adults, but 2-phenylethanol and phenylacetonitrile when used in combination with acetic acid were attractive to both sexes.

Rapid non-invasive quality control of semi-finished products for the food industry by direct injection mass spectrometry headspace analysis: the case of milk powder, whey powder and anhydrous milk fat

In this study, we demonstrated the suitability of direct injection mass spectrometry headspace analysis for rapid non-invasive quality control of semi-finished dairy ingredients, such as skim milk powder (SMP), whole milk powder (WMP), whey powder (WP) and anhydrous milk fat (AMF), which are widely used as ingredients in the food industry. In this work, for the first time, we applied proton transfer reaction-mass spectrometry (PTR-MS) with a time-of-flight (ToF) analyzer for the rapid and non-invasive analysis of volatile compounds in different samples of SMP, WMP, WP and AMF. We selected different dairy ingredients in various concrete situations (e.g. same producer and different expiration times, different producers and same days of storage, different producers) based on their sensory evaluation. PTR-ToF-MS allowed the separation and characterization of different samples based on the volatile organic compound (VOC) profiles. Statistically significant differences in VOC content were generally coherent with differences in sensory evaluation, particularly for SMP, WMP and WP. The good separation of SMP samples from WMP samples suggested the possible application of PTR-ToF-MS to detect possible cases of adulteration of dairy ingredients for the food industry. Our findings demonstrate the efficient and rapid differentiation of dairy ingredients on the basis of the released VOCs via PTR-ToF-MS analysis and suggest this method as a versatile tool (1) for the facilitation/optimization of the selection of dairy ingredients in the food industry and (2) and for the prompt innovation in the production of dairy ingredients. Copyright © 2016 John Wiley & Sons, Ltd.

Monitoring of lactic fermentation driven by different starter cultures via direct injection mass spectrometric analysis of flavour-related volatile compounds

In this work, we used Proton Transfer Reaction-Mass Spectrometry (PTR-ToF-MS), coupled with an automated sampling system, to monitor lactic fermentation driven by different yogurt commercial starter cultures via direct injection mass spectrometric analysis of flavour-related volatile compounds. The aim is the identification of markers for real-time and non-invasive bioprocess control and optimisation as an industrial driver of innovation in food technology and biotechnology. We detected more than 300 mass peaks, tentatively identifying all major yogurt aroma volatiles. Thirteen mass peaks showed statistically significant differences among the four commercial starters. Among these are acetaldehyde, methanethiol, butanoic acid, 2-butanone, diacetyl, acetoin, 2-hydroxy-3-pentanone/pentanoic acid, heptanoic acid and benzaldehyde which play a key role in yogurt flavour. These volatile described the diverse flavour properties claimed by food biotechnological companies and, considering the possible contribution to yogurt flavour, are potential markers for the rapid screening of starter cultures and for the quality design in this fermentation-driven production. The strength of our approach lies in the identification, for the first time, of specific depletion kinetics of four sulphur containing compounds occurring during fermentation (hydrogen sulphide, methanethiol, S-methyl thioacetate/S-ethyl thioformate, pentane-thiol), which suggest a new possible protechnological feature of yogurt starter cultures.