Chemical compositions and volatile compounds of Tricholoma matsutake from different geographical areas at different stages of maturity

Volatile compounds and aroma characteristics of mushrooms: a review

Mushrooms are popular due to their rich medicinal and nutritional value. Of the many characteristics of mushrooms, aroma has received extensive attention and research as a key determinant of consumer preference. This paper reviews the production, role and contribution of common volatile compounds (VCs) in wild and cultivated mushrooms, and explores the methods used to characterize them and the factors influencing aroma. To date, more than 347 common VCs have been identified in mushrooms, such as aldehydes, ketones, alcohols and sulfur-containing compounds. Extraction and identification of VCs is a critical step and combining multiple analytical methods is an effective strategy in mushroom aroma studies. In addition, the VCs and the aroma of mushrooms are affected by a variety of factors such as genetics, growing conditions, and processing methods. However, the mechanism of influence is unknown. Further studies on the production mechanisms of VCs, their contribution to aroma, and the factors influencing their formation need to be determined in order to fully elucidate aroma and flavor of mushrooms.

Predictive Modeling Analysis for the Quality Indicators of Matsutake Mushrooms in Different Transport Environments

Matsutake mushrooms, known for their high value, present challenges due to their seasonal availability, difficulties in harvesting, and short shelf life, making it crucial to extend their post-harvest preservation period. In this study, we developed three quality predictive models of Matsutake mushrooms using three different methods. The quality changes of Matsutake mushrooms were experimentally analyzed under two cases (case A: Temperature control and sealing measures; case B: Alteration of gas composition) with various parameters including the hardness, color, odor, pH, soluble solids content (SSC), and moisture content (MC) collected as indicators of quality changes throughout the storage period. Prediction models for Matsutake mushroom quality were developed using three different methods based on the collected data: multiple linear regression (MLR), support vector regression (SVR), and an artificial neural network (ANN). The comparative results reveal that the ANN outperforms MLR and SVR as the optimal model for predicting Matsutake mushroom quality indicators. To further enhance the ANN model's performance, optimization techniques such as the Levenberg-Marquardt, Bayesian regularization, and scaled conjugate gradient backpropagation algorithm techniques were employed. The optimized ANN model achieved impressive results, with an R-Square value of 0.988 and an MSE of 0.099 under case A, and an R-Square of 0.981 and an MSE of 0.164 under case B. These findings provide valuable insights for the development of new preservation methods, contributing to the assurance of a high-quality supply of Matsutake mushrooms in the market.

The flavors of edible mushrooms: A comprehensive review of volatile organic compounds and their analytical methods

Due to their distinctive flavors, edible mushrooms have gained attention in flavor-related research, and the quality of their flavors determines their consumption. The odor is a vital element of food flavor that significantly impacts consumers' perceptions and purchase decisions. The volatile organic compounds (VOCs) of the odorant ingredient is the primary factors affecting scent characteristics. VOCs analysis and identification require technical assistance. The production and use of edible mushrooms can be aided by a broader examination of their volatile constituents. This review discusses the composition of VOCs in edible mushrooms and how they affect flavors. The principles, advantages, and disadvantages of various methods for extraction, isolation, and characterization of the VOCs of edible mushrooms are also highlighted. The numerous VOCs found in edible mushrooms such as primarily C-8 compounds, organic sulfur compounds, aldehydes, ketones, alcohols, and esters are summarized along with their effects on the various characteristics of scent. Combining multiple extraction, isolation, identification, and quantification technologies will facilitate rapid and accurate analysis of VOCs in edible mushrooms as proof of sensory attributes and quality.

Effects of Drying Methods on Taste Components and Flavor Characterization of Cordyceps militaris

The influences of four drying methods (hot air drying (HAD), vacuum freeze drying (VFD), vacuum drying (VD) and intermittent microwave combined with hot air drying (MW-HAD)) on the taste profile and flavor characteristic of Cordyceps militaris were investigated. MW-HAD samples had the highest levels of umami taste 5'-nucleotides, bitter taste amino acids, and equivalent umami concentration (EUC) value. The aroma fingerprints and differences of dried Cordyceps militaris were established by GC-MS with odor activity values (OAVs) and GC-IMS with principal component analysis (PCA). GC-MS data showed that the predominant volatiles of dried samples were aldehydes, alcohols, and ketones. VFD samples had the highest amount of total aroma compounds and C8 compounds. Moreover, 21 aroma-active components (OAVs ≥ 1) were the main contributors to the flavor of dried Cordyceps militaris. The OAVs of 1-octen-3-one and 3-octanone associated with mushroom-like odor in VFD were significantly higher than other samples. Furthermore, a significant difference in flavor compounds of four dried samples was also clearly demonstrated by GC-IMS analysis with PCA. GC-IMS analysis revealed that VFD samples had the most abundant flavor compounds. Overall, MW-HAD was an effective drying method to promote umami taste, and VFD could superiorly preserve volatiles and characteristic aroma compounds in dried Cordyceps militaris.

Insights into health promoting effects and myochemical profiles of pine mushroom Tricholoma matsutake

Tricholoma matsutake (TM) is a valuable edible mushroom that has attracted increasing attention due to its potential medicinal values and functional uses. However, the chemical composition and molecular mechanisms behinds TM are not specifically summarized yet. Hence, this review aims to systematically analyze the research progress on the characterization of chemical compositions and the reported health effects of TM in the last 20 years. The myochemical profiles of TM consist of proteins with amino acids, fatty acids, nucleic acids with their derivatives, polysaccharides, minerals, volatile components, phenolic compounds, and steroids. The bioactive substances in TM exert their health effects mainly by regulating body immunity and restoring the balance of the redox system. NF-κB signaling pathway and its downstream cytokines such as TNF-α and IL-6 are the key molecular mechanisms. In addition, MAPK, PI3K-Akt, and JAK-STAT are also involved. NF-κB, MAPK, and PI3K-Akt are also highly related to cancer regulation and thus TM has great anticancer potential. Considering that most studies have only investigated the dosage and inhibition rate of TM on cancer cell lines, more extensive studies need to focus on the specific molecular mechanisms behind these anticancer effects in the future.

Relationship between flavor and energy status in shiitake mushroom (Lentinula edodes) harvested at different developmental stages

To understand the relationship between flavor and energy, the flavor, energy, and enzyme activity related to energy metabolism in shiitake mushrooms harvested at different developmental stages were investigated. The results indicated that the adenosine triphosphate level increased significantly in developing mushrooms and was strongly correlated with the fresh weight. The levels of equivalent umami concentration (EUC), total aroma compounds, energy charge, adenosine triphosphatase, cytochrome c oxidase, and succinic dehydrogenase varied with maturity. In addition, a strong correlation was observed between aroma compounds, EUC, and energy status (p < 0.05). Our results suggest that the unique flavor of developing shiitake mushroom is closely related to energy. The findings may provide a new strategy to improve the flavor of mushrooms by regulating their energy levels. PRACTICAL APPLICATION: The unique flavor of shiitake mushroom, which has a significant impact on consumer preferences, is one of its key characteristics. This research paper provides a theoretical foundation for determining the optimal harvest period for shiitake mushrooms with high quality and a new strategy to improve the flavor of mushrooms by regulating their energy levels.

Biotransformation of [U-13C]linoleic acid suggests two independent ketonic- and aldehydic cycles within C8-oxylipin biosynthesis in Cyclocybe aegerita (V. Brig.) Vizzini

Although the typical aroma contributing compounds in fungi of the phylum Basidiomycota are known for decades, their biosynthetic pathways are still unclear. Amongst these volatiles, C8-compounds are probably the most important ones as they function, in addition to their specific perception of fungal odour, as oxylipins. Previous studies focused on C8-oxylipin production either in fruiting bodies or mycelia. However, comparisons of the C8-oxylipin biosynthesis at different developmental stages are scarce, and the biosynthesis in basidiospores was completely neglected. In this study, we addressed this gap and were able to show that the biosynthesis of C8-oxylipins differs strongly between different developmental stages. The comparison of mycelium, primordia, young fruiting bodies, mature fruiting bodies, post sporulation fruiting bodies and basidiospores revealed that the occurance of the two main C8-oxylipins octan-3-one and oct-1-en-3-ol distinguished in different stages. Whereas oct-1-en-3-ol levels peaked in the mycelium and decreased with ongoing maturation, octan-3-one levels increased during maturation. Furthermore, oct-2-en-1-ol, octan-1-ol, oct-2-enal, octan-3-ol, oct-1-en-3-one and octanal contributed to the C8-oxylipins but with drastically lower levels. Biotransformations with [U-13C]linoleic acid revealed that early developmental stages produced various [U-13C]oxylipins, whereas maturated developmental stages like post sporulation fruiting bodies and basidiospores produced predominantly [U-13C]octan-3-one. Based on the distribution of certain C8-oxylipins and biotransformations with putative precursors at different developmental stages, two distinct biosynthetic cycles were deduced with oct-2-enal (aldehydic-cycle) and oct-1-en-3-one (ketonic-cycle) as precursors.

Distinct Compartmentalization of Microbial Community and Potential Metabolic Function in the Fruiting Body of Tricholoma matsutake

The uniquely compartmentalized fruiting body structure of the ectomycorrhizal fungus (EMF) Tricholoma matsutake, is a hotspot of microbial habitation and interaction. However, microbial diversity within this microniche structure of the EMF is rarely investigated. Furthermore, there is limited information concerning microbiomes associated with sporomes belonging to the ubiquitous fungal phylum Basidiomycota, particularly with respect to fungus-EMF interactions. In this study, we conducted high throughput sequencing, using ITS (fungal) and 16S rRNA (bacterial) marker genes to characterize and compare fruiting body microbiomes in the outer (pileipellis and stipitipellis) and inner layers (pileum context, stipe context, and lamellae) of the fruiting body of T. matsutake. Our results show the number of unique bacterial operational taxonomic units (OTUs) among the different compartments ranged from 410 to 499 and was more than double that of the shared/common OTUs (235). Micrococcales, Bacillales, Caulobacter, and Sphingomonas were the primary significant bacterial taxa within the different compartments of the dissected T. matsutake fruiting body. Non-parametric multivariate analysis of variance showed significant compartmental differences for both the bacterial and the fungal community structure within the T. matsutake fruiting body. The metabolic profiling revealed putative metabolisms (of amino acids, carbohydrates, and nucleotides) and the biosynthesis of secondary metabolites to be highly enriched in outer layers; in the inner parts, the metabolisms of energy, cofactors, vitamins, and lipids were significantly higher. This study demonstrates for the first time the distinct compartmentalization of microbial communities and potential metabolic function profiles in the fruiting body of an economically important EMF T. matsutake.

Comparative Mitogenomic Analysis Reveals Dynamics of Intron Within and Between Tricholoma Species and Phylogeny of Basidiomycota

The genus of Tricholoma is a group of important ectomycorrhizal fungi. The overlapping of morphological characteristics often leads to the confusion of Tricholoma species classification. In this study, the mitogenomes of five Tricholoma species were sequenced based on the next-generation sequencing technology, including T. matsutake SCYJ1, T. bakamatsutake, T. terreum, T. flavovirens, and T. saponaceum. These five mitogenomes were all composed of circular DNA molecules, with sizes ranging from 49,480 to 103,090 bp. Intergenic sequences were considered to be the main factor contributing to size variations of Tricholoma mitogenomes. Comparative mitogenomic analysis showed that the introns of the Agaricales mitogenome experienced frequent loss/gain events. In addition, potential gene transfer was detected between the mitochondrial and nuclear genomes of the five species of Tricholoma. Evolutionary analysis showed that the rps3 gene of the Tricholoma species was under positive selection or relaxed selection in the evolutionary process. In addition, large-scale gene rearrangements were detected between some Tricholoma species. Phylogenetic analysis using the Bayesian inference and maximum likelihood methods based on a combined mitochondrial gene set yielded identical and well-supported tree topologies. This study promoted the understanding of the genetics, evolution, and phylogeny of the Tricholoma genus and related species.

Key Odorants from the American Matsutake, Tricholoma magnivelare

The American Matsutake, Tricholoma magnivelare (Peck) Redhead, is an edible wild mushroom with a distinctive aroma described as mushroom and spice with subtle floral and citrus nuances. In this study, a total of 36 odorants were identified from T. magnivelare using solvent-assisted flavor evaporation and aroma extract dilution analysis. Stable isotope dilution assays were performed to quantitate 14 odorants with flavor dilution factors ≥64. Odorants with high odor activity values (OAVs) included 1-octen-3-one (OAV 2125), linalool (OAV 650), (2E,4E)-nona-2,4-dienal (OAV 304), and 1-octen-3-ol (OAV 206). An odor simulation model matched the odor profile of the fresh mushroom. Omission studies showed that linalool, hexanal, (2E,4E)-nona-2,4-dienal, methyl (E)-3-phenylprop-2-enoate, and 1-octen-3-one or 1-octen-3-ol were essential to the aroma of T. magnivelare. Chiral chromatography showed that α-pinene was a scalemic mixture of 34% (R)-(+) to 66% (S)-(-), while 1-octen-3-ol was present as 95% (R)-(-) to 5% (S)-(+), and linalool was 96% (R)-(-) to 4% (S)-(+). These results establish the base for future investigations into the aroma chemistry of other members of the genus Tricholoma.

Volatilomes of Cyclocybe aegerita during different stages of monokaryotic and dikaryotic fruiting

Volatile organic compounds (VOC) are characteristic for different fungal species. However, little is known about VOC changes during development and their biological role. Therefore, we established a laboratory cultivation system in modified crystallizing dishes for analyzing VOC during fruiting body development of the dikaryotic strainCyclocybe aegeritaAAE-3 as well as four monokaryotic offspring siblings exhibiting different fruiting phenotypes. From these, VOC were extracted directly from the headspace (HS) and analyzed by means of gas chromatography-mass spectrometry (GC-MS). For all tested strains, alcohols and ketones, including oct-1-en-3-ol, 2-methylbutan-1-ol and cyclopentanone, were the dominant substances in the HS of early developmental stages. In the dikaryon, the composition of the VOC altered with ongoing fruiting body development and, even more drastically, during sporulation. At the latter stage, sesquiterpenes, especially Δ6-protoilludene, α-cubebene and δ-cadinene, were the dominant substances. After sporulation, the amount of sesquiterpenes decreased, while additional VOC, mainly octan-3-one, appeared. In the HS of the monokaryons, less VOC were present of which all were detectable in the HS of the dikaryonC. aegeritaAAE-3. The results of the present study show that the volatilome ofC. aegeritachanges considerably depending on the developmental stage of the fruiting body.

Functional principal component analysis for near-infrared spectral data: a case study on Tricholoma matsutakeis

Tricholoma matsutakeis (TM) is the most expensive edible fungi in China. Given its price and exclusivity, some dishonest merchants will sell adulterated TM by combining it with cheaper fungi in an attempt to earn more profits. This fraudulent behavior has broken food laws and violated consumer trust. Therefore, there is an urgent need to develop a rapid, accurate, and nondestructive tool to discriminate TM from other edible fungi. In this work, a novel detection algorithm combined with near-infrared spectroscopy (NIR) and functional principal component analysis (FPCA) is proposed. Firstly, the raw NIR data were pretreated by locally weighted scatterplot smoothing (LOWESS) and multiplication scatter correction (MSC). Then, FPCA was used to extract valuable information from the preprocessed NIR data. Then, a classifier was designed by using the least-squares support-vector machine (LS-SVM) to distinguish categories of edible fungi. Furthermore, the one-versus-one (OVO) strategy was included and the binary LS-SVM was extended to a multi-class classifier. The 166 samples of four varieties of fungi were used to validate the proposed method. The results show that the proposed method has great capability in near infrared spectra classification, and the average accurate of FPCA-LSSVM is 97.3% which is greater than that of PCA-LSSVM (93.5%).

Identification of the Pol Gene as a Species-Specific Diagnostic Marker for Qualitative and Quantitative PCR Detection of Tricholoma matsutake

Tricholoma matsutake is a rare, precious, and wild edible fungus that could not be cultivated artificially until now. This situation has given way to the introduction of fake T. matsutake commodities to the mushroom market. Among the methods used to detect food adulteration, amplification of species-specific diagnostic marker is particularly important and accurate. In this study, the Pol gene is reported as a species-specific diagnostic marker to identify three T. matsutake varieties and 10 other types of edible mushrooms through qualitative and quantitative PCR. The PCR results did not reveal variations in the amplified region, and the detection limits of qualitative and quantitative PCR were found to be 8 ng and 32 pg, respectively. Southern blot showed that the Pol gene exists as a single copy in the T. matsutake genome. The method that produced the purest DNA of T. matsutake in this study was also determined, and the high-concentration salt precipitation method was confirmed to be the most suitable among the methods tested. The assay proposed in this work is applicable not only to the detection of raw materials but also to the examination of processed products containing T. matsutake.

Prediction of the potential geographic distribution of the ectomycorrhizal mushroom Tricholoma matsutake under multiple climate change scenarios

Effective conservation and utilization strategies for natural biological resources require a clear understanding of the geographic distribution of the target species. Tricholoma matsutake is an ectomycorrhizal (ECM) mushroom with high ecological and economic value. In this study, the potential geographic distribution of T. matsutake under current conditions in China was simulated using MaxEnt software based on species presence data and 24 environmental variables. The future distributions of T. matsutake in the 2050s and 2070s were also projected under the RCP 8.5, RCP 6, RCP 4.5 and RCP 2.6 climate change emission scenarios described in the Special Report on Emissions Scenarios (SRES) by the Intergovernmental Panel on Climate Change (IPCC). The areas of marginally suitable, suitable and highly suitable habitats for T. matsutake in China were approximately 0.22 × 10⁶ km², 0.14 × 10⁶ km², and 0.11 × 10⁶ km², respectively. The model simulations indicated that the area of marginally suitable habitats would undergo a relatively small change under all four climate change scenarios; however, suitable habitats would significantly decrease, and highly suitable habitat would nearly disappear. Our results will be influential in the future ecological conservation and management of T. matsutake and can be used as a reference for studies on other ectomycorrhizal mushroom species.