Volatile components of white Hypsizygus marmoreus detected by electronic nose and HS-SPME-GC-MS: Influence of four drying methods

Evaluation of aroma characteristics of Penaeus vannamei with different drying methods using HS-SPME-GC-MS, MMSE-GC-MS, and sensory evaluation

The effects of microwave drying (MD), hot air drying (HAD), vacuum hot air drying (VD), and vacuum freeze drying (VFD) on the volatile profiles of Penaeus vannamei were investigated. A total of 89 and 94 volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and monolithic material sorptive extraction gas chromatography-mass spectrometry (MMSE-GC-MS), respectively. Orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable influence on projection (VIP) models were utilized to select characteristic volatiles and key marker compounds (e.g., octanal, 1-octen-3-ol, 2-methyl-butanal, 2-ethyl-furan, and trimethyl-pyrazine) to discriminate among four drying methods. Based on synthesis of odor descriptions and sensory evaluation, it was found that P. vannamei via MD, HAD, and VD greatly reduced the fishy and generated roasted, fatty, and smoked odors. This study systematically analyzed the aroma characteristics of four traditional dried P. vannamei products, which may provide theoretical guidance for industrial production.

GC-IMS-Based Volatile Characteristic Analysis of Hypsizygus marmoreus Dried by Different Methods

Gas chromatography-ion mobility spectroscopy (GC-IMS) was used to analyze the volatile components in dried Hypsizygus marmoreus of different drying methods, including hot air drying (HAD), heat pump drying (HPD), heated freeze-drying (HFD), and unheated freeze-drying (UFD). A total of 116 signal peaks corresponding to 96 volatile compounds were identified, including 25 esters, 24 aldehydes, 23 alcohols, 13 ketones, 10 heterocyclic compounds, 8 carboxylic acids, 7 terpenes, 3 sulfur-containing compounds, 2 nitrogen-containing compounds, and 1 aromatic hydrocarbon. The total content of volatile compounds in H. marmoreus dried by the four methods, from highest to lowest, was as follows: HAD, HPD, HFD, and UFD. The main volatile compounds included carboxylic acids, alcohols, esters, and aldehydes. Comparing the peak intensities of volatile compounds in dried H. marmoreus using different drying methods, it was found that the synthesis of esters, aldehydes, and terpenes increased under hot drying methods such as HAD and HPD, while the synthesis of compounds containing sulfur and nitrogen increased under freeze-drying methods such as HFD and UFD. Nine common key characteristic flavor compounds of dried H. marmoreus were screened using relative odor activity values (ROAV > 1), including ethyl 3-methylbutanoate, acetic acid, 2-methylbutanal, propanal, methyl 2-propenyl sulfate, trimethylamine, 3-octanone, acetaldehide, and thiophene. In the odor description of volatile compounds with ROAV > 0.1, it was found that important flavor components such as trimethylamine, 3-octanone, (E)-2-octenal, and dimethyl disulfide are related to the aroma of seafood. Their ROAV order is HFD > UFD > HPD > HAD, indicating that H. marmoreus using the HFD method have the strongest seafood flavor. The research findings provide theoretical guidance for selecting drying methods and refining the processing of H. marmoreus.

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

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

Comparative evaluation of physical characteristics and volatile flavor components of Bangia fusco-purpurea subjected to hot air drying and vacuum freeze-drying

Bangia fusco-purpurea is an economically important seaweed with Fujian characteristics. Given that its harvest is seasonal, drying is often used to remove moisture, extend storage time, and facilitate further processing. Hence, the current study sought to explore the impact of different drying processes on the quality and volatile fingerprints of Bangia fusco-purpurea. To this end, the effects of hot air drying (HAD) and vacuum freeze drying (VFD) on the drying characteristics, microstructure, rehydration, and volatile components of dried B. fusco-purpurea were investigated. The results showed that the water removal efficiency of HAD was significantly higher than that of VFD. However, VFD better preserved the skeletal structure of B. fusco-purpurea than HAD, with a faster rehydration rate and a more uniform cell structure after rehydration. Using electronic nose and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF MS), significant differences in the volatile profiles of fresh, HAD, and VFD B. fusco-purpurea were assessed. E-nose analysis revealed that both HAD and VFD treatments significantly reduced sulfides, aromatic compounds, and nitrogen oxides in fresh B. fusco-purpurea. However, the alcohol, aldehyde, and ketone contents were lower in the VFD samples compared with HAD and fresh samples, whereas the content of methyl flavor substances was significantly higher. GC × GC-TOF MS analysis revealed that the most abundant volatile categories in HAD and VFD were hydrocarbons, alcohols, and esters. The number of volatile components in the HAD samples was significantly lower than in the VFD and fresh samples. As drying progressed, hydrocarbons and alcohols were formed in dried B. fusco-purpurea due to the thermal degradation of carbohydrates, lipids, amino acids, and the Maillard reaction. There were also significant flavor differences between HAD and VFD B. fusco-purpurea. Thus, although HAD exhibits better drying efficiency, VFD has more significant advantages in terms of product quality.

Preliminary study on the anti-CO2 stress and growth ability of hypsizygus marmoreus mutant strain HY68

BACKGROUND

A high concentration of CO2 will stagnate the development of the newly formed primordia of Hypsizygus marmoreus, hinder the development of the mushroom cap, thereby inhibiting the normal differentiation of the fruiting body. Moreover, in the previous experiment, our research group obtained the mutant strain HY68 of H. marmoreus, which can maintain normal fruiting under the condition of high concentration of CO2. Our study aimed to evaluate the CO2 tolerance ability of the mutant strain HY68, in comparison with the starting strain HY61 and the control strain HY62. We analyzed the mycelial growth of these strains under various conditions, including different temperatures, pH levels, carbon sources, and nitrogen sources, and measured the activity of the cellulose enzyme. Additionally, we identified and predicted β-glucosidase-related genes in HY68 and analyzed their gene and protein structures.

RESULTS

Our results indicate that HY68 showed superior CO2 tolerance compared to the other strains tested, with an optimal growth temperature of 25 °C and pH of 7, and maltose and beef paste as the ideal carbon and nitrogen sources, respectively. Enzyme activity assays revealed a positive correlation between β-glucosidase activity and CO2 tolerance, with Gene14147 identified as the most closely related gene to this activity. Inbred strains of HY68 showed trait segregation for CO2 tolerance.

CONCLUSIONS

Both HY68 and its self-bred offspring could tolerate CO2 stress. The fruiting period of the strains resistant to CO2 stress was shorter than that of the strains not tolerant to CO2 stress. The activity of β-GC and the ability to tolerate CO2 were more closely related to the growth efficiency of fruiting bodies. This study lays the foundation for understanding how CO2 regulates the growth of edible fungi, which is conducive to the innovation of edible fungus breeding methods. The application of the new strain HY68 is beneficial to the research of energy-saving production in factory cultivation.

Evaluation of the nutritional value, umami taste, and volatile organic compounds of Hypsizygus marmoreus by simulated salivary digestion in vitro

Hypsizygus marmoreus is an edible medicinal mushroom species with a high dietary value. The main purpose of this study was to evaluate the nutritional value, umami taste, and volatile organic compounds (VOCs) of H. marmoreus treated with hot water combined with simulated salivary digestion in vitro. Seafood mushroom (Hm3) had the highest content of moisture, soluble polysaccharides, soluble proteins, and total flavonoids while white Hypsizygus marmoreus (Hm1) had the highest total phenolic content. Moreover, Hm1 had a more noticeable equivalent umami concentration (EUC) value, indicating the umami properties of Hm1 as a food or processing ingredient. Results from E-nose and HS-SPME-GC-MS revealed that the VOCs of Hm1 and brown Hypsizygus marmoreus (Hm2) were relatively similar, which differed substantially from Hm3. Among the 134 VOCs, 24 differential metabolites were identified by OPLS-DA analysis, characterized by VIP > 1, p-value < 0.05, and FC > 2 (pairwise comparisons). Furthermore, 10 biomarkers with VIP > 1 and p-value < 0.05 were identified by PLS-DA analysis based on the total differential metabolites to distinguish different strains of H. marmoreus. These results will benefit future research on the chemistry of H. marmoreus and serve as a guide for breeding, introducing, and using the species more effectively.

Development of Green Banana Fruit Wines: Chemical Compositions and In Vitro Antioxidative Activities

This study aimed to develop functional fruit wines using whole fruit, pulp, and peels from green bananas. The boiled banana homogenates were mixed with cane sugar before wine fermentation. Quality parameters, phenolic compounds, flavor components, and antioxidative properties of the green banana peel wine (GBPW), green banana pulp wine (GBMW), and whole banana wine (GBW) were determined. High-performance liquid chromatography was used to determine the phytochemical compounds in three wines, and the flavor components were further analyzed using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry. The flavor components and in vitro antioxidant activities were, respectively, determined using the relative odor activity value and the orthogonal projections on latent structure discrimination analysis (OPLS-DA). In vitro antioxidative capacities for these wines were evaluated using antioxidant chemical assays and cell culture methods. The total phenolic and total tannin content of the GBPW, GBMW, and GBW showed reducing trends with increasing fermentation days, whereas the total flavonoid content of the wine samples exhibited downward trends. The antioxidant capacities of the three wine samples were higher than those of the raw fruit samples, except for the metal chelation rate (%). Additionally, the main flavor component in the wine samples was 3-methyl-1-butanol. Its percentages in the GBPW, GBMW, and GBW were 72.02%, 54.04%, and 76.49%, respectively. The OPLS-DA results indicated that the three wines presented significantly different antioxidant activities. The cell-culture-based antioxidant analysis showed that these wine samples had protective effects against the oxidative stress of the 3T3-L1 preadipocytes induced by hydrogen peroxide. This study provided a theoretical basis for defining the antioxidant characteristics of banana wines and expanding novel channels for using banana peels to develop nutraceuticals.

Development of Green Banana Fruit Wines: Chemical Compositions and In Vitro Antioxidative Activities

This study aimed to develop functional fruit wines using whole fruit, pulp, and peels from green bananas. The boiled banana homogenates were mixed with cane sugar before wine fermentation. Quality parameters, phenolic compounds, flavor components, and antioxidative properties of the green banana peel wine (GBPW), green banana pulp wine (GBMW), and whole banana wine (GBW) were determined. High-performance liquid chromatography was used to determine the phytochemical compounds in three wines, and the flavor components were further analyzed using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry. The flavor components and in vitro antioxidant activities were, respectively, determined using the relative odor activity value and the orthogonal projections on latent structure discrimination analysis (OPLS-DA). In vitro antioxidative capacities for these wines were evaluated using antioxidant chemical assays and cell culture methods. The total phenolic and total tannin content of the GBPW, GBMW, and GBW showed reducing trends with increasing fermentation days, whereas the total flavonoid content of the wine samples exhibited downward trends. The antioxidant capacities of the three wine samples were higher than those of the raw fruit samples, except for the metal chelation rate (%). Additionally, the main flavor component in the wine samples was 3-methyl-1-butanol. Its percentages in the GBPW, GBMW, and GBW were 72.02%, 54.04%, and 76.49%, respectively. The OPLS-DA results indicated that the three wines presented significantly different antioxidant activities. The cell-culture-based antioxidant analysis showed that these wine samples had protective effects against the oxidative stress of the 3T3-L1 preadipocytes induced by hydrogen peroxide. This study provided a theoretical basis for defining the antioxidant characteristics of banana wines and expanding novel channels for using banana peels to develop nutraceuticals.

Effects of combined drying methods on physicochemical and rheological properties of instant Tremella fuciformis soup

The textural, rheological and flavor reconstitution behaviors of rehydrated instant Tremella fuciformis soup, treated by combined freeze drying + vacuum drying (FD-VD), freeze drying + far-infrared drying (FD-FIRD) and freeze drying + hot air drying (FD-HAD), were evaluated and compared with fresh soup. Moisture content transfer point (MTP) of 15 ± 2% was selected according to products quality and drying time. Instant soup treated by FD-VD showed lower shrinkage and looser structure compared with that of FD-FIRD and FD-HAD. After rehydration, FD-VD soup showed the best reconstitution behaviors with recovery rate of TSS, soluble protein and polysaccharide content up to 87.61%, 83.52%, 79.08% respectively. Besides, FD-VD rehydrated soup, with the highest polysaccharide content, showed similar rheological properties to the fresh soup. FD-VD soup contained more similar aroma compounds to FD sample measured by GC-MS, while FD-FIRD and FD-HAD generated new aldehydes, ketones and hydrocarbons, leading to unpleasant flavors.

Phytochemical Characterization of Rhus coriaria L. Extracts by Headspace Solid-Phase Micro Extraction Gas Chromatography, Comprehensive Two-Dimensional Liquid Chromatography, and Antioxidant Activity Evaluation

Rhus coriaria L. (Anacardiaceae), commonly known as sumac, has been used since ancient times for many different applications, and nowadays is used mostly as a spice obtained from its in the Mediterranean and the Middle ground fruits and employed for flavoring and garnishing food, predominantly Eastern regions. Traditionally, sumac has been also used in popular medicine for the treatment of many ailments including hemorrhoids, wound healing, diarrhea, ulcers, and eye inflammation. Sumac drupes are indeed rich in various classes of phytochemicals including organic acids, flavonoids, tannins, and others, which are responsible of their powerful antioxidant capacity, from which treatment of many common diseases such as cardiovascular disease, diabetes, and cancer could benefit. In this work we evaluated the influence of fruit ripeness, conservation, and processing. To this aim, a phytochemical characterization of six different samples of Rhus coriaria L. was carried out. Specifically, headspace solid-phase micro extraction gas chromatography coupled to mass spectrometry and comprehensive two-dimensional liquid chromatography coupled to photodiode array and mass spectrometry detection, were employed. A total of 263 volatile compounds, including terpene hydrocarbons, acids, and aldehydes, as well as 83 polyphenolic compounds, mainly gallic acid derivatives, were positively identified. All samples showed a significant antioxidant activity by means of oxygen radical absorbance capacity, in line with their polyphenolic content and composition. Such findings set a solid ground to support the utilization of this plant as an attractive target for novel nutraceutical approaches and for drug discovery.

Identification techniques and detection methods of edible fungi species

Edible fungi have high nutritional value and great potential. Confusion among edible fungi species, and foodborne diseases due to toadstool poisoning or death induced by inadvertent consumption exist across the world. Therefore, edible fungi must be accurately identified. Based on different substances in edible fungi, there are different detection methods, and the same method can use different identification technology. Sensory identification methods include morphological and odor methods. Instrumental analysis methods based on chemical composition include chromatographic, mass spectrometry and spectral technology. Molecular biology identification methods based on nucleic acids include molecular marker technology, sequencing technology, isothermal amplification technology and endogenous reference gene method. Method is channel, and technology is the means. The principles, advantages, disadvantages and applications of various identification techniques and detection methods were discussed in this work to provide reference for the identification research of edible fungi and technical support for preventing food safety incidents caused by toadstools.

Optimization of combined microwave and hot air drying technology for purple cabbage by Response Surface Methodology (RSM)

Purple cabbage is one of the world's most widely consumed vegetables with high nutritional values containing the antioxidants and anti-inflammatory activity of anthocyanins, vitamins, and minerals. But due to rapid postharvest quality decay, novel processing techniques including drying are required. In order to determine the conditions of combined microwave and hot air drying for purple cabbage, factors affecting the drying process including microwave density, hot air temperature, and the dry base water content at conversion point were investigated using the anthocyanin content, DPPH antioxidant capacity, chewiness, △E, rehydration ratio, and average drying rate as responses. The combined drying conditions were optimized considering three independent variables at three different levels by response surface methodology. The results showed that the processing parameters of purple cabbage with combined microwave and hot air drying technology were microwave density at 2.5 W/g, moisture content of conversion point at 4.0 g/g, and hot air temperature at 55°C. Under these conditions, the anthocyanin content, DPPH antioxidant capacity, chewiness, △E, rehydration ratio, average drying rate, and overall score of the dried purple cabbage were 175.87 mg/100 g, 87.59%, 4,521.468 g, 26.5, 4.3, 0.76 g/min, and 0.785, respectively. Therefore, combined microwave and hot air drying technology is an effective, suitable method for drying purple cabbage.

Volatile Profiling of Pleurotus eryngii and Pleurotus ostreatus Mushrooms Cultivated on Agricultural and Agro-Industrial By-Products

The influence of genetic (species, strain) and environmental (substrate) factors on the volatile profiles of eight strains of Pleurotus eryngii and P. ostreatus mushrooms cultivated on wheat straw or substrates enriched with winery or olive oil by products was investigated by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Selected samples were additionally roasted. More than 50 compounds were determined in fresh mushroom samples, with P. ostreatus presenting higher concentrations but a lower number of volatile compounds compared to P. eryngii. Roasting resulted in partial elimination of volatiles and the formation of pyrazines, Strecker aldehydes and sulfur compounds. Principal component analysis on the data obtained succeeded to discriminate among raw and cooked mushrooms as well as among Pleurotus species and strains, but not among different cultivation substrates. Ketones, alcohols and toluene were mainly responsible for discriminating among P. ostreatus strains while aldehydes and fatty acid methyl esters contributed more at separating P. eryngii strains.

Identifying a melanogenesis-related candidate gene by a high-quality genome assembly and population diversity analysis in Hypsizygus marmoreus

Hypsizygus marmoreus is one of the most important edible fungi in Basidiomycete division and includes white and gray strains. However, very limited knowledge is known about the genomic structures and the genetic basis for the white/gray diversity of this mushroom. Here, we report the near-complete high-quality H. marmoreus genome at the chromosomal level. Comparative genomics analysis indicates that chromosome structures were relatively conserved, and variations in collinearity and chromosome number were mainly attributed by chromosome split/fusion events in Aragicales, whereas the fungi genome experienced many genomic chromosome fracture, fusion, and genomic replication events after the split of Aragicales from Basidiomycetes. Resequencing of 57 strains allows us to classify the population into four major groups and associate genetic variations with morphological features, indicating that white strains were not originated independently. We further generated genetic populations and identified a cytochrome P450 as the candidate causal gene for the melanogenesis in H. marmoreus based on bulked segregant analysis (BSA) and comparative transcriptome analysis. The high-quality H. marmoreus genome and diversity data compiled in this study provide new knowledge and resources for the molecular breeding of H. marmoreus as well as the evolution of Basidiomycete.

An unattended HS-SPME-GC-MS/MS combined with a novel sample preparation strategy for the reliable quantitation of C8 volatiles in mushrooms: A sample preparation strategy to fully control the volatile emission

Eight carbon (C8) compounds are the key characteristic flavors of mushrooms. The quantitative analysis of the volatiles in mushrooms is challenging especially with the unattended HS-SPME-GC-MS. An unattended HS-SPME-GC-MS/MS in combination with novel sample preparation of the complete control of volatile emissions was developed for the quantitation of the C8 volatiles in mushrooms. The sample preparation strategy was composed of freeze-drying, rehydration, and the addition of a 15% citric acid solution. With this strategy, the volatile emission from mushroom was fully controlled at a certain time point. This method was found to be highly reliable, sensitive, precise, and accurate. This method was successfully applied to measure the contents of the C8 volatiles in the beech, button, and shiitake mushrooms. 1-Octene-3-ol was the most predominant compound in the mushrooms, representing 62.4, 69.0, and 89.2% of the total C8 volatiles in the beech, button, and shiitake mushrooms, respectively.

Variations of volatile flavour compounds in finger citron (Citrus medica L. var. sarcodactylis) pickling process revealed by E-nose, HS-SPME-GC-MS and HS-GC-IMS

The pickled products of finger citron are famous in southern China for their unique taste and flavor. Although pickling process involves complex treatments including salting, desalting, sugaring, cooking and drying, extended shelf-life up to ten years after pickling can be achieved. In this study, the variations of volatile flavour components in the pickling process of finger citron were investigated by electronic nose (E-nose), headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). HS-SPME-GC-MS identified 85 substances, and HS-GC-IMS identified 81 substances, including terpenoids (21), aromatic hydrocarbons (11), alcohols (11), aldehydes (10), esters (7), phenols (6), acids (5), ethers (2), ketones (2), and other species (10). Linalool, limonene, (E)-3,7-dimethyl-1,3,6-octatriene, myrcene, 3-carene, β-pinene, α-pinene, terpinolene, 1-methyl-4-(1-methylethyl)-1,4-cyclohexadiene, α-terpinene, (S)-β-bisabolene, 1-isopropyl-2-methylbenzene and 1-methyl-4-(1-methylethenyl)-benzene were the stable substances at relatively high contents in finger citron at different pickling process. Salting and drying steps in the pickling process exerted greatest influence on the volatile components of finger citron. Salting promoted the generation of aldehydes, esters and acids, but led to the disappearance of alcohols, while drying promoted the generation of alcohols, phenols, aldehydes and acids at the expense of reduction in terpenoids. Our study revealed that the characteristic volatile compounds of finger citron pickled products was mainly formed by the biological reactions in the salting stage and thermal chemical transformations in the drying stage. This study also validated the suitability of E-nose combined with HS-SPME-GC-MS and HS-GC-IMS in tracking the changes of volatile components in finger citron during the pickling process.

Nanocomposite-based packaging affected the taste components of white Hypsizygus marmoreus by regulating energy status

The effects of nanocomposite-based packaging material (Nano-PM) on the taste components and mitochondrial energy metabolism of postharvest white Hypsizygus marmoreus (WHM), as well as the underlying influence mechanism were investigated. The results showed that the major taste components, including succinic acid and mannitol, remained at higher level in Nano-PM. The flavor 5'-nucleotides (5'-GMP and 5'-IMP) of WHM in Nano-PM were significantly higher (p < 0.05) compared with that in the normal packaging material (Normal-PM). Principal component analysis indicated that there was a distinction of flavor compounds (6 organic acids, 3 soluble sugars and 5 5'-nucleotides) of WHM between Nano-PM and Normal PM treatments during storage. Moreover, Nano-PM delayed the mitochondrial microstructure breakdown and the reduction of ATPase activity, and it maintained a higher ATP content and higher level of energy charge. Our results demonstrated that Nano-PM could affect the taste components of postharvest WHM partially by regulating the energy metabolism.

Influence of Roasting Condition on Flavor Profile of Sunflower Seeds: A flavoromics approach

Sunflower see/ds (Helianthus annuus L.) were roasted in an electric forced air oven for 15, 30, 45, and 60 min at 125, 135 and 145 °C. The effect of temperature and time on the flavor profile of the samples were evaluated by headspace solid-phase microextraction coupled with gas chromatography-mass spectroscopy (HS-SPME-GC-MS). Unsupervised Principle Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC) multivariate statistical methods were used to visualize, group and classify the samples. 114 volatiles were identified in the roasted sunflower seeds (RSF), with terpenes (α-pinene, β-pinene), heterocyclic compounds (2-ethyl-3-methylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, pyridine), aldehydes (2-methylbutanal, furfural, hexanal, phenylacetaldehyde), hydrocarbons (octane, 2-isobutyl-1,4-dimethylcyclohexane, 6,6-dimethylundecane), alcohol (3-methyl-2-propyl-1-pentanol), and γ-butyrolactone being dominant compounds. The content of most volatile compounds increased with increase in roasting temperature and time, such as esters, terpenes, pyrazines, aldehydes, ketones, and alcohols. 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-3-methylpyrazine, and 2-ethyl-3,5-dimethylpyrazine contributed to be the major role in roast and nutty flavor of the roasted sunflower seeds. Roasting at 125 °C for 45 min was found to be the better condition for roasted sunflower seeds, which gave the lowest off-flavor and burnt tastes.

Characterization of Volatile Profiles of Six Popular Edible Mushrooms Using Headspace-Solid-Phase Microextraction Coupled with Gas Chromatography Combined with Chemometric Analysis

The classification of six mushroom species (white beech, brown beech, button, oyster, king oyster, and enoki mushrooms) was successfully achieved using canonical discriminant analysis (CDA) on volatile metabolite data sets obtained by headspace-solid-phase microextraction gas chromatography (HS-SPME-GC). Twenty-seven major volatile compounds in six edible mushrooms were positively identified by HS-SPME-GC mass spectroscopy. The total volatile content was highest in brown beech mushroom (P < 0.05). Significant difference in volatile profile was observed between brown beach and white beech mushrooms. Button mushroom contained significantly higher contents of benzaldehyde and benzyl alcohol than the other mushrooms (P < 0.05). Oyster mushroom contained 1-octen-3-ol as the most prevalent volatile, representing 67% out of total volatiles. Hexanal (35.0%) and 1-octen-3-ol (22.5%) were the most abundant volatiles found in king oyster. Hexanal (29.1%) was the most prevalent volatile in enoki mushroom only. Several volatile pairs with very high positive correlation in their levels were identified, representing the highest correlation coefficient (r = 0.970) for the pair of t-2-octenal and 2,4-octandienal. CDA was much more efficient than principal component analysis for the differentiation of mushroom species. PRACTICAL APPLICATION: The present study provided the important information on the volatile metabolite profiles of popular six commercial mushroom species. The present data will be useful for the quality control of mushrooms cultivated in farms and mushroom products processed in food industry. The strategy of canonical discriminant analysis in combination with HS-SPME-GC could be expanded for the determining the authentication of mushroom species.