Optimization of a multiple headspace sorptive extraction method coupled to gas chromatography-mass spectrometry for the determination of volatile compounds in macroalgae

Development and comprehensive SBSE-GC/Q-TOF-MS analysis optimization, comparison, and evaluation of different mulberry varieties volatile flavor

Optimization of seven parameters of stir bar sorptive extraction (SBSE) on mulberry volatile components for the first time. A total of 347 volatile components were identified and quantified in 14 mulberry varieties, predominantly encompassing esters, aldehydes, terpenoids, hydrocarbons, ketones, alcohols, heterocyclics, acids, and phenols. Hexanal and (E)-2-hexenal were the dominant volatiles. Furthermore, 79 volatile compounds characterized by odor activity values (OAVs) > 1 were identified, making a significant contribution to the distinctive mulberry flavor. "Green" notes were the most intense, followed by "fatty" and "fruity". Utilizing odor ring charts, the volatile flavor characteristics of the 14 mulberry varieties could be intuitively distinguished. This study not only established a viable methodology for differentiating mulberry varieties but also laid a theoretical foundation for the quality evaluation and variety breeding of mulberry flavor.

Identifying markers volatiles in Brazilian virgin oil by multiple headspace solid-phase microextraction, and chemometrics tools

A protocol was optimized to determine the volatile profile from monovarietal virgin olive oil (VOO) by multiple headspace solid-phase microextraction (MHS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analysis. For this, a Plackett-Burman (PB) and central composite rotational designs (CCRD) were used to define the best condition of extraction. Moreover, fatty acids profile and principal component analysis (PCA) was used to identify markers among the cultivars. The amount of 0.1 g of sample was enough to express the volatile composition of the olive oils by MHS-SPME. Volatile compounds [nonanal, (Z)-3-Hexen-1-ol, (Z)-3-Hexenyl Acetate, Hexyl Acetate, 3-Methylbutyl Acetate, (E)-2-Hexen-1-ol, (E)-2-Hexenyl Acetate] and fatty acids [C17:1, C18, C18:1, C18:2] were those reported such as the markers in the varieties of olive oils. The PCA analysis allowed the classification of the most representative volatiles and fatty acids for each cultivar. Through two principal components was possible to obtain 81.9% of explanation of the variance of the compounds. The compounds were quantified using a validated method. The MHS-SPME combined with multivariate analysis showed a promising tool to identify markers and for the discrimination of olive oil varieties.

Sampling Volatile Organic Compound Emissions from Consumer Products: A Review

Volatile organic compounds (VOCs) are common constituents of many consumer products. Although many VOCs are generally considered harmless at low concentrations, some compound classes represent substances of concern in relation to human (inhalation) exposure and can elicit adverse health effects, especially when concentrations build up, such as in indoor settings. Determining VOC emissions from consumer products, such as toys, utensils or decorative articles, is of utmost importance to enable the assessment of inhalation exposure under real-world scenarios with respect to consumer safety. Due to the diverse sizes and shapes of such products, as well as their differing uses, a one-size-fits-all approach for measuring VOC emissions is not possible, thus, sampling procedures must be chosen carefully to best suit the sample under investigation. This review outlines the different sampling approaches for characterizing VOC emissions from consumer products, including headspace and emission test chamber methods. The advantages and disadvantages of each sampling technique are discussed in relation to their time and cost efficiency, as well as their suitability to realistically assess VOC inhalation exposures.

Comparative Evaluation of Secreted Plant Carotenoid Cleavage Dioxygenase 1 (CCD1) Enzymes in Saccharomyces cerevisiae

Enabling technologies in synthetic biology now present the opportunity to engineer wine yeast for enhanced novel aromas. In doing so, improved wine products will increase the desirability of wine for the consumer and add value to the winemaker. The action of the enzyme carotenoid cleavage dioxygenase 1 (CCD1) on β-carotene to produce β-ionone is of interest to improve the aroma and flavour of the wine. Engineering the yeast, Saccharomyces cerevisiae, to produce higher concentrations of CCD1 in grape-must presents an opportunity to increase the levels of this volatile organic compound, thus enhancing the organoleptic properties of wine. To this end, four phylogenetically diverse plant CCD1 genes were synthesised with a secretion signal peptide and transformed into S. cerevisiae. The relative ability of each enzyme secreted into the yeast supernatant to cleave the deep orange C40 β-carotene was determined by spectrophotometry; furthermore, the by-product of such cleavage, the highly aromatic C13 β-ionone, was assessed by head-space solid-phase micro-extraction, with analysis and detection by GCMS. Reduction in β-carotene levels and release of β-ionone from the supernatant were validated by LCMS detection of CCD1. These experiments demonstrated that expression in yeast of the CCD1s derived from Petunia hybrida and Vitis vinifera and their subsequent secretion into the medium provided superior efficacy in both β-carotene reduction and β-ionone liberation. We anticipate this knowledge being of benefit to future winemakers in producing a vinous product with enhanced organoleptic properties.

Multivariate Optimization Procedure for Dynamic Headspace Extractions Coupled to GC(×GC)

Volatile organic compounds (VOCs) are ubiquitous chemicals of great interest in the study of aromas and flavours of foods. Many recent studies present optimized headspace (HS) and dynamic headspace (DHS) methods for specific sample types; however, the literature does not present ­(to the best of our knowledge) a generalized procedure for the thorough optimization of a DHS extraction. This article presents an approach using design of experiments (DoE) for the optimization of DHS extraction parameters. The approach is demonstrated for two different food sample types with diverse populations of VOCs: active sourdough colony as an example with a high moisture content, and sourdough bread as an example with a lower moisture content. Optimized methods are assessed for VOC extraction reproducibility and exhaustiveness; guidelines for DHS optimization are presented.

Characterization of cheesy odor formed during fermentation of soy drink with Agrocybe aegerita

The market for plant protein-based substitutes for cheeses is growing, but the sensory properties are distinctively different from the original products. Hence, natural and vegan cheesy flavors are needed to aromatize the products. A cheesy, sweaty and parmesan-like aroma was produced by fermentation of soy drink with Agrocybe aegerita. Aroma dilution analysis revealed short-chain fatty acids (SCFAs) as main influencing cheesy odorants analyzed by gas chromatography-mass spectrometry-olfactometry. In comparison to the five cheese varieties, the SCFA profile of the fermented soy drink revealed similarities with Parmesan and Emmental cheese. Meanwhile, principal component analysis showed an approximation of the aroma profile after fermentation with A. aegerita to those of cheeses. 3-Methylbutanoic acid was synthesized from the protein fraction, while the oil fraction contributed to the formation of unbranched SCFAs like butanoic acid. Accordingly, the production of these compounds can be increased by addition of the fractions.

Effect of different cooking methods on sea lettuce (Ulva rigida) volatile compounds and sensory properties

BACKGROUND

The effect of different cooking methods (boiling, vacuum and steamed cooking) on the volatile compound content and sensory properties of sea lettuce (Ulva rigida) seaweed was assessed. Sea lettuce was cooked at three different temperatures (50, 70 and 100 °C) for three different lengths of time (5, 10 and 15 min). Various statistical techniques were employed in order to establish any possible changes.

RESULTS

The different cooking methods modified significantly both the volatile compound content and the sensory properties of sea lettuce seaweed. In general, the cooked samples had lower concentrations of several volatile compounds than the control sample, mainly aldehydes. Regarding sensory analysis, the cooked samples exhibited lower values for various aroma descriptors such as seaside and seaweed, whereas descriptor scores such as cooked fish, salty dry fish and crustacean increased. No clear statistical differences were found between different cooking lengths of time and temperature levels with regard to both volatile compounds and sensory properties.

CONCLUSIONS

In the cooking of sea lettuce seaweeds, the main sensory changes and modifications in their volatile content took place during the first minutes of cooking and at medium cooking temperatures. © 2020 Society of Chemical Industry.

Benzene-assisted photoionization positive ion mobility spectrometry coupled with a time-resolved introduction for field detecting dimethyl sulfide in seawater

Biogenic dimethyl sulfide (DMS) has attracted widespread attention over several decades due to its potential role in linking ocean biology and climate. The air-to-sea exchange flux, estimated based on marine DMS concentration, offers useful information for evaluating its contribution to climate change. As such, field observation techniques with the characteristics of fast testing speed, portability and easy operation are in demand to accurately monitor the DMS in seawater. In this paper, we proposed a new strategy for the sensitive field measurement of DMS in seawater based on benzene-assisted photoionization positive ion mobility spectrometry (BAPI-PIMS) coupled with a time-resolved introduction. Benzene was employed as a dopant to improve the selectivity by keeping the other sulfur compounds from being ionized, while the two-dimensional data versus drift time and retention time were obtained via an online separating column to eliminate the adverse impact of environmental moisture. Under the optimization conditions, the LODs (S/N = 3) for two product-ion peaks (PIPs) of DMS decreased to 0.081 nmol L^-1. Finally, the established method was applied to the lab and ship-board analysis of seawater from the Bohai Sea and the North Yellow Sea in the summer of 2019, and DMS in surface seawater was in the range of 0.11-23.90 nmol L^-1 with an average of 9.88 ± 6.96 nmol L^-1, indicating the potential for the field detection of marine DMS.

Characterization and differentiation of seaweeds on the basis of their volatile composition

Thirty one samples from different macroalgae species have been studied to determine the influence of several parameters such as the harvesting season, the geographical origin, the species or a pretreatment procedure on their volatile composition. A Multiple Head Space Sorptive Extraction methodology coupled to Gas Chromatography with Mass Spectrometry Detection (MHSSE-GC-MS) has been used to analyze 44 volatile compounds that can be found in the different samples. Of all the factors, the collection season proved to be the most influential, followed by origin with significantly lower volatile compounds concentrations found in the samples collected in spring and in southern Spain. A Principal Component Analysis showed that beta ionone, benzaldehyde, 6-methyl-5-hepten-2-one, together with some acids were the most strongly affected by the season, with highest values in those samples that had been collected in the autumn. On the other hand, the pretreatment (raw, salting or dehydration) proved to have a low influence.

Development of Head Space Sorptive Extraction Method for the Determination of Volatile Compounds in Beer and Comparison with Stir Bar Sorptive Extraction

A headspace sorptive extraction method coupled with gas chromatography–mass spectrometry (HSSE–GC–MS) was developed for the determination of 37 volatile compounds in beer. After optimization of the extraction conditions, the best conditions for the analysis were stirring at 1000 rpm for 180 min, using an 8-mL sample with 25% NaCl. The analytical method provided excellent linearity values (R² > 0.99) for the calibration of all the compounds studied, with the detection and quantification limits obtained being low enough for the determination of the compounds in the beers studied. When studying the repeatability of the method, it proved to be quite accurate, since RSD% values lower than 20% were obtained for all the compounds. On the other hand, the recovery study was successfully concluded, resulting in acceptable values for most of the compounds (80–120%). The optimised method was successfully applied to real beer samples of different types (ale, lager, stout and wheat). Finally, an analytical comparison of the optimised HSSE method, with a previously developed and validated stir bar sorptive extraction (SBSE) method was performed, obtaining similar concentration values by both methods for most compounds.

Evolution of volatile compounds and sensory characteristics of edible green seaweed (Ulva rigida) during storage at different temperatures

BACKGROUND

Edible seaweeds are one of the most important resources that currently exist for their multiple uses and applications. Like other food types, during their storage there are significant changes in sensory characteristics associated with loss of freshness and with production and/or degradation of their volatile compounds. In this study, multiple headspace sorptive extraction (MHSSE) coupled with gas chromatography/mass spectrometry (GC/MS) detection has been applied to an edible green seaweed (Ulva rigida) in order to determine the evolution of volatile compounds during storage for 12 days at 4 or 16 °C.

RESULTS

The existing analytical methodology has been updated and validated for 18 additional compounds. At the end, 41 volatile compounds from different chemical families were quantified. Aldehydes, carboxylic acids and esters were the main classes found in U. rigida. Analytical and sensory data were submitted for statistical analysis. During storage, most volatile compounds were only affected by the number of storage days (P < 0.05), with significant decreases as storage time increased. Sensory analysis revealed significant changes in the samples stored for longer times (8, 10 and 12 days), with a clear influence of the boiled vegetable descriptor.

CONCLUSION

In order to get a successful preservation of seaweeds and to maintain their marine character during storage, both temperature and time should be carefully controlled. © 2019 Society of Chemical Industry.

Volatile compounds released by microalgae-water phase from Taihu Lake in China

The spectrum of Volatile Organic Compounds (VOCs) released by the microalgae-water phase of Taihu Lake in China was examined, then release behaviors were studied using non-methane hydrocarbons (NMHC, including a few polar organics) to describe the total amount of the released VOCs. Coupled dynamic headspace sampling with on-line monitoring of methane and NMHC was used to reflect the quasi-realtime release behavior of methane and NMHC by the microalgae-water phase. Alkanes, alkenes, oxygenated VOCs (OVOCs) and volatile sulfide chemicals (VOSCs) were detected. Their relative contents over time varied markedly from the stationary to the apoptosis phase, with their release rates as described by NMHC estimated from 0.02 to 0.59 μgC/(h g). Methane was investigated simultaneously, and its release rate was found to be 0.05-3.96 μgC/(h g). The release rates of both NMHC and methane were found to relate to the culture phase of the microalgae.

Chemical Diversity of Codium bursa (Olivi) C. Agardh Headspace Compounds, Volatiles, Fatty Acids and Insight into Its Antifungal Activity

The focus of present study is on Codium bursa collected from the Adriatic Sea. C. bursa volatiles were identified by gas chromatography and mass spectrometry (GC-FID; GC-MS) after headspace solid-phase microextraction (HS-SPME), hydrodistillation (HD), and supercritical CO₂ extraction (SC-CO₂). The headspace composition of dried (HS-D) and fresh (HS-F) C. bursa was remarkably different. Dimethyl sulfide, the major HS-F compound was present in HS-D only as a minor constituent and heptadecane percentage was raised in HS-D. The distillate of fresh C. bursa contained heptadecane and docosane among the major compounds. After air-drying, a significantly different composition of the volatile oil was obtained with (E)-phytol as the predominant compound. It was also found in SC-CO₂ extract of freeze-dried C. bursa (FD-CB) as the major constituent. Loliolide (3.51%) was only identified in SC-CO₂ extract. Fatty acids were determined from FD-CB after derivatisation as methyl esters by GC-FID. The most dominant acids were palmitic (25.4%), oleic (36.5%), linoleic (11.6%), and stearic (9.0%). FD-CB H₂O extract exhibited better antifungal effects against Fusarium spp., while dimethyl sulfoxide (DMSO) extract was better for the inhibition of Penicillium expansum, Aspergillus flavus, and Rhizophus spp. The extracts showed relatively good antifungal activity, especially against P. expansum (for DMSO extract MIC₅₀ was at 50 µg/mL).