Volatile biomarkers for wild mushrooms species discrimination

Volatile flavor behavior characterization of Hericium erinaceus during postharvest storage using E-nose, HS-GC-IMS, and HS-SPME-GC-MS after treated with electron-beam generated X-ray irradiation

Flavor alteration is a crucial factor affecting the quality of mushrooms during preservation. The dynamic variations of volatile profiles of fresh Hericium erinaceus with electron-beam generated X-ray irradiation were investigated by combining E-nose, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). E-nose analysis achieved rapid discrimination in all treatments over storage time. 65 and 73 volatile organic compounds (VOCs) were identified by HS-GC-IMS and HS-SPME-GC-MS, respectively. Thereinto, 1-octen-3-ol, 1-octen-3-one, and 2-octanone were screened out as the characteristic VOCs, which contents declined during storage. While the contents of (E)-2-octenal, (E)-2-nonenal, and 1-octanol increased. The flavor profile changes from distinct mushroom and floral odor to an intense alcohol and fatty odor. Notably, one-kGy irradiation remained more volatiles and denser mushroom odor after storage. Multivariate analysis further confirmed that 1.0 kGy irradiation contributed to the overall aroma retention during postharvest storage of H. erinaceus.

Impact of Incorporating Shiitake Mushrooms (Lentinula edodes) on Microbial Community and Flavor Volatiles in Traditional Jiuqu

Jiuqu is one of the important raw materials for brewing Chinese rice wine (Huangjiu), often known as the "bone of wine". In this study, the microbial community and flavor substances of Jiuqu made with different amounts of shiitake mushroom (Lentinula edodes) were investigated through high-throughput sequencing technology and headspace gas chromatography-ion migration spectroscopy (HS-GC-IMS), using traditional wheat yeast as a control. The results showed that 1593 genera and 5507 species were identified among the four types of yeast, with Aspergillus and Paecilomyces being the most dominant microorganisms at the genus level. Carbohydrate, coenzyme, and amino acid metabolism may be the main metabolic processes of the dominant microorganisms in Jiuqu. In terms of flavor, a total of 79 volatile substance monomers and some dimers were detected from four types of Jiuqu raw materials, with the main substances being 12 aldehydes, 19 ketones, 13 alcohols, 19 esters, 4 olefins, 1 acid, 3 ethers, 4 furans, 1 pyrazine, 1 pyridine, 1 triethylamine, and 1 thiazole. The correlation results indicate that Aspergillus, Lactobacillus, and Vibrio correlate significantly with the volatile flavor compounds unique to shiitake mushrooms and also have a positive effect on alcohol, esters, and furans. These results could shed light on the selection of Lentinula edodes as a fermentation starter for Huangjiu in the Qinba Mountain area.

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.

Application of spectral image processing with different dimensions combined with large-screen visualization in the identification of boletes species

Boletes are favored by consumers because of their unique flavor, rich nutrition and delicious taste. However, the different nutritional values of each species lead to obvious price differences, so shoddy products appear on the market, which affects food safety. The aim of this study was to find a rapid and effective method for boletes species identification. In this paper, 1,707 samples of eight boletes species were selected as the research objects. The original Mid-Infrared (MIR) spectroscopy data were adopted for support vector machine (SVM) modeling. The 11,949 spectral images belong to seven data sets such as two-dimensional correlation spectroscopy (2DCOS) and three-dimensional correlation spectroscopy (3DCOS) were used to carry out Alexnet and Residual network (Resnet) modeling, thus we established 15 models for the identification of boletes species. The results show that the SVM method needs to process complex feature data, the time cost is more than 11 times of other models, and the accuracy is not high enough, so it is not recommended to be used in data processing with large sample size. From the perspective of datasets, synchronous 2DCOS and synchronous 3DCOS have the best modeling results, while one-dimensional (1D) MIR Spectrum dataset has the worst modeling results. After comprehensive analysis, the modeling effect of Resnet on the synchronous 2DCOS dataset is the best. Moreover, we use large-screen visualization technology to visually display the sample information of this research and obtain their distribution rules in terms of species and geographical location. This research shows that deep learning combined with 2DCOS and 3DCOS spectral images can effectively and accurately identify boletes species, which provides a reference for the identification of other fields, such as food and Chinese herbal medicine.

Smelling the difference: separation of healthy and infected button mushrooms via microbial volatile organic compounds

In the literature there is a lack of consensus regarding mushroom volatiles; most of the studies identify only a few volatiles. This study deals with button mushrooms, their emitted volatiles, and the main changes during infections (green mould and cobweb disease) in a time series experiment. Emitted volatile profiles were determined using HS-SPME-GC-MS coupled analytical technique. The separation of healthy and infected mushroom samples was done using different multivariate statistical methods (PCA, PLS-DA, HeatMap). The main volatile compounds were also determined. As a result, several compounds were found to successfully distinguish healthy (bisabolene, cymene, myrtenol, d-limonene, etc.) and infected (thujopsene, cedr-8-ene, chamigrene, patchulane, longifolene, etc.), mushroom samples, and an early disease detection was achieved. Results can be used for further investigation of infected mushroom identification in an early stage in packaged mushroom products. Furthermore, these results could help to identify infections in commercially available mushrooms, thus increasing shelf-life in super/hypermarkets.

Influences of Some Aromatic Plants on Volatile Compounds and Bioactivity of Cultivated Pleurotus citrinopileatus and Pleurotus djamor

Two edible Pleurotus species, namely, Pleurotus citrinopileatus and Pleurotus djamor grown in the media of mulberry shavings which were substituted with myrtle, bay laurel, and rosemary leaves were studied. According to volatile profiles, 13 aldehydes, 8 ketones, 7 alcohols, 5 aromatic compounds and 4 terpenes were totally identified. Rosemary leaves were very effective for decreasing the concentrations of some oxidation products in Pleurotus citrinopileatus, but the same impact was not seen in Pleurotus djamor. The high amount of benzaldehyde (41.80 %) detected in bay laurel medium might have played a role in preventing bioactivity. Control Pleurotus citrinopileatus and Pleurotus djamor had a total phenolic content of 4284.89 and 3080.04 mg GAE per kg DM, respectively, and the enrichment of composts with aromatic plant leaves caused significant differences in Pleurotus djamor (p<0.05). Myrtle addition increased total phenolic content and antioxidant activities (by DPPH and FRAP assays) of Pleurotus djamor mushroom as 342.29 mg GAE/kg DM, 0.43 μmol TE/g DM and 2.07 μmol TE/g DM, respectively, when compared to intact one.

Review of Recent Modern Analytical Technology Combined with Chemometrics Approach Researches on Mushroom Discrimination and Evaluation

Mushroom is a macrofungus with precious fruiting body, as a food, a tonic, and a medicine, human have discovered and used mushrooms for thousands of years. Nowadays, mushroom is also a "super food" recommended by the World Health Organization (WHO) and Food and Agriculture Organization (FAO), and favored by consumers. Discrimination of mushroom including species, geographic origin, storage time, etc., is an important prerequisite to ensure their edible safety and commodity quality. Moreover, the effective evaluation of its chemical composition can help us better understand the nutritional properties of mushrooms. Modern analytical technologies such as chromatography, spectroscopy and mass spectrometry, etc., are widely used in the discrimination and evaluation researches of mushrooms, and chemometrics is an effective means of scientifically processing the multidimensional information hidden in these analytical technologies. This review will outline the latest applications of modern analytical technology combined with chemometrics in qualitative and quantitative analysis and quality control of mushrooms in recent years. Briefly describe the basic principles of these technologies, and the analytical processes of common chemometrics in mushroom researches will be summarized. Finally, the limitations and application prospects of chromatography, spectroscopy and mass spectrometry technology are discussed in mushroom quality control and evaluation.

Mass spectrometry in food authentication and origin traceability

Food authentication and origin traceability are popular research topics, especially as concerns about food quality continue to increase. Mass spectrometry (MS) plays an indispensable role in food authentication and origin traceability. In this review, the applications of MS in food authentication and origin traceability by analyzing the main components and chemical fingerprints or profiles are summarized. In addition, the characteristic markers for food authentication are also reviewed, and the advantages and disadvantages of MS-based techniques for food authentication, as well as the current trends and challenges, are discussed. The fingerprinting and profiling methods, in combination with multivariate statistical analysis, are more suitable for the authentication of high-value foods, while characteristic marker-based methods are more suitable for adulteration detection. Several new techniques have been introduced to the field, such as proton transfer reaction mass spectrometry, ambient ionization mass spectrometry (AIMS), and ion mobility mass spectrometry, for the determination of food adulteration due to their fast and convenient analysis. As an important trend, the miniaturization of MS offers advantages, such as small and portable instrumentation and fast and nondestructive analysis. Moreover, many applications in food authentication are using AIMS, which can help food authentication in food inspection/field analysis. This review provides a reference and guide for food authentication and traceability based on MS.

Identification of volatile producing enzymes in higher fungi: Combining analytical and bioinformatic methods

Filamentous fungi harbor the genetic potential for the biosynthesis of several secondary metabolites including various volatile organic compounds (VOCs). Nonetheless, under standard laboratory conditions, many of these VOCs are not formed. Furthermore, little is known about enzymes involved in the production of fungal VOCs. To tap these interesting topics, we developed an approach to identify enzymes putatively involved in the fungal VOC biosynthesis. In this chapter, we highlight different fungal cultivation methods and techniques for the extraction of VOCs, including a method that allows the noninvasive analysis of VOCs. In addition using terpene synthases as an example, it is depicted how enzymes putatively involved in VOC synthesis can be identified by means of bioinformatic approaches. Transcriptomic data of chosen genes combined with volatilome data obtained during different developmental stages is demonstrated as a powerful tool to identify enzymes putatively involved in fungal VOC biosynthesis. Especially with regard to subsequent enzyme characterization, this procedure is a target-oriented way to save time and efforts by considering only the most important enzymes.

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.

Rapid spectroscopic method for quantifying gluten concentration as a potential biomarker to test adulteration of green banana flour

The demand for gluten-free banana flour has led manufactures to enforce strict measures for quality control. A need has arisen for the development of more sensitive and reliable methods to test the quality of green banana flour (GBF). The objective of this study was to develop rapid visible to near-infrared (Vis-NIR) based spectroscopic models to detect gluten concentration, as a biomarker to detect wheat flour adulteration in green banana flour (GBF). Spectroscopic data were acquired using a desktop (FOSS®) Vis-NIR spectroscopy ranging from 400 to 2500 nm of the electromagnetic spectrum. The spectral and reference data were submitted to principal component analysis (PCA) and partial least squares regression (PLSR) for the development of gluten adulteration detection models. Calibration models were constructed based on a full cross-validation approach, consisting of 51 samples for the calibration set and 21 samples for the test set. PCA scores plot discriminated gluten adulterated and unadulterated GBF samples with 100% accuracy for the first two principal components (PCs). The optimal prediction model was obtained after a combination of baseline (offset and baseline linear correlation) and standard normal variate (SNV) pre-processing technique. This model showed a 94% coefficient of determination of cross-validation (R²_cv) and prediction (R²_p); root mean square error of cross-validation (RMSECV) of 3.7 mg/kg, root mean square error of prediction (RMSEP) of 3.9 mg/kg; and RPD value of 4. This work has demonstrated that Vis-NIRS method is a robust and feasible technology that may be used to ensure the safety of banana flour and that this product stays gluten-free by providing good and reliable gluten detection and quantification prediction models.

Application of Identification and Evaluation Techniques for Edible Mushrooms: A Review

Edible mushrooms are healthy food with high nutritional value, which is popular with consumers. With the increase of the problem of mushrooms being confused with the real and pollution in the market, people pay more and more attention to food safety. More than 167 articles of edible mushroom published in the past 20 years were reviewed in this paper. The analysis tools and data analysis methods of identification and quality evaluation of edible mushroom species, origin, mineral elements were reviewed. Five techniques for identification and evaluation of edible mushrooms were introduced and summarized. The macroscopic, microscopic and molecular identification techniques can be used to identify species. Chromatography, spectroscopy technology combined with chemometrics can be used for qualitative and quantitative study of mushroom and evaluation of mushroom quality. In addition, multiple supervised pattern-recognition techniques have good classification ability. Deep learning is more and more widely used in edible mushroom, which shows its advantages in image recognition and prediction. These techniques and analytical methods can provide strong support and guarantee for the identification and evaluation of mushroom, which is of great significance to the development and utilization of edible mushroom.

Biosynthetic Mechanism of Key Volatile Biomarkers of Harvested Lentinula edodes Triggered by Spore Release

In this study, headspace solid-phase microextraction-gas chromatography-mass spectrometry, multivariate analyses, and transcriptomics were used to explore the biosynthesis of key volatiles and the formation of spores in Lentinula (L.) edodes. Among the 50 volatiles identified, 1-octen-3-ol, phenethyl alcohol, and several esters were considered key aromas because of their higher odor activity values. Eleven volatiles were screened as biomarkers by orthogonal partial least squares discriminant analysis, and hierarchical cluster analysis showed that these biomarkers could represent all volatiles to distinguish the spore release stage. The activities of lipoxygenase (LOX), hydroperoxide lyase, alcohol dehydrogenase, and alcohol acyltransferase were higher in L. edodes with spore release. Moreover, linolenic acid and phenylalanine metabolism were involved in aroma biosynthesis. One LOX-related gene and five aryl alcohol dehydrogenase-related genes could regulate the biosynthesis of 1-octen-3-ol, phenethyl alcohol, and phenylacetaldehyde. In addition, several key genes were involved in meiosis to regulate sporulation.

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.

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.

VOCs profile of Colletotrichum spp. as a potential tool for quality control of açaí pulp

Colletotrichum has been identified as responsible for the "dried fruit" disease in açaí (Euterpe oleracea). Besides concern for açaí pulp quality control, the characterization of Colletotrichum has been difficult, which has motivated the search for chemical markers in the Volatile Organic Compounds (VOCs) profile for use as a tool in the identification of açaí pulp contaminated by the fungus. Extracted VOCs by Headspace - Solid Phase Micro Extraction (HS-SPME) were identified through gas chromatography mass spectrometry (GC-MS). From GC-MS analyzes 26 VOCs were identified, with a predominance of the terpenoids. Chemometrically, menthol and menthone were assigned as potential markers of the genus. The analysis of VOCs in açaí pulps contaminated by Colletotrichum under different cultivation conditions enabled the detection of menthone. This result illustrated the selectivity of the culture medium and the potential of this tool for use in the quality control of açaí pulp.

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.

Toxic metabolite profiling of Inocybe virosa

Wild mushroom foraging involves a high risk of unintentional consumption of poisonous mushrooms which is a serious health concern. This problem arises due to the close morphological resemblances of toxic mushrooms with edible ones. The genus Inocybe comprises both edible and poisonous species and it is therefore important to differentiate them. Knowledge about their chemical nature will unambiguously determine their edibility and aid in an effective treatment in case of poisonings. In the present study, the presence of volatile toxic metabolites was verified in Inocybe virosa by gas chromatography. Methyl palmitate, phenol, 3,5-bis (1,1-dimethyl ethyl) and phytol were the identified compounds with suspected toxicity. The presence of the toxin muscarine was confirmed by liquid chromatography. The in vitro study showed that there was negligible effect of the digestion process on muscarine content or its toxicity. Therefore, the role of muscarine in the toxicity of Inocybe virosa was studied using a bioassay wherein metameters such as hypersalivation, immobility, excessive defecation, heart rate and micturition were measured. Administration of muscarine resulted in an earlier onset of symptoms and the extract showed a slightly stronger muscarinic effect in comparison to an equivalent dose of muscarine estimated in it. Further, the biological fate of muscarine was studied by pharmacokinetics and gamma scintigraphy in New Zealand white rabbits. Significant amount of the toxin was rapidly and effectively concentrated in the thorax and head region. This study closely explains the early muscarinic response such as miosis and salivation in mice. By the end of 24 h, a relatively major proportion of muscarine administered was accumulated in the liver which stands as an explanation to the hepatotoxicity of Inocybe virosa. This is one of the rare studies that has attempted to understand the toxic potential of muscarine which has previously been explored extensively for its pharmaceutical applications.

Triangular Test of Amanita Mushrooms by Using Electronic Nose and Sensory Panel

This work aims to advance understanding of the differentiation of mushroom species through electronic devices that use sensors of various technologies and techniques for pattern recognition, comparing mainly volatile substances that emanate from them. In this first phase, the capacity of human olfaction to differentiate between the smell released by different wild mushrooms of the genus Amanita was analyzed by means of a triangular sensory test, comparing later the data to those obtained for the same samples with an electronic nose in a similar test. The results, still very preliminary, encourage imagining the wide application that these techniques will have and the feedback that this application can suppose for the training of the sense of human olfaction.

Application of chemometric tools for the comparison of volatile profile from raw and roasted regional and foreign almond cultivars (Prunus dulcis)

In almonds, volatile compounds are major contributors to flavour, being scarce the current knowledge about their volatile profile. Hence, this work intended to characterize the volatile profile, using headspace solid-phase microextraction and gas chromatography-mass spectrometry, in raw and roasted almond cultivars (regional cvs. Amendoão, Bonita, Casanova, Molar and Pegarinhos and foreign cvs. Ferragnès and Glorieta). Overall, 35 compounds were identified, with major chemical classes being alcohols and aldehydes. In raw fruits, benzaldehyde and 3-methyl-1-butanol were key compounds, with roasting changing volatile profiles, increasing release of compounds, with predominance of hexanal and benzaldehyde. Cultivars Glorieta and Molar didn't show significant increase in aldehyde content after roasting, which may indicate higher resistance to heat-caused oxidation. The use of linear discriminant analysis and principal components analysis permitted the recognition of patterns in the volatile profiles, that can be useful for cultivars identification. This work allowed the characterization and monitoring changes caused by roasting of volatile components of less studied almond cultivars, identifying some that can withstand roasting procedures with reduced formation of compounds associated with off-flavours.

Elemental composition of selected species of mushrooms based on a chemometric evaluation

The aim of the study was to determine 16 elements by FAAS and ICP-AES in ca. 1500 samples of 22 species of mushrooms collected from different regions of Poland and the area around Umeå in Sweden. Chemometric techniques were applied to differentiate samples with respect to their geographical origin and interspecies differentiation. Samples of Cantharellus cibarius (Fr.), Boletus edulis (Bull.) and Leccinum scabrum (Bull.) Gray from Morąg, Augustów, the Zaborski Landscape Park, Tarnobrzeg and Umeå were discriminated by factor 1 and factor 2. Some species, i.e. Cantharellus cibarius, Boletus edulis, Boletus pinophilus (Pilát & Dermek), Leccinum aurantiacum (Bull.) Gray, Leccinum scabrum and Leccinum versipelle (Fr. & Hök) Snell from one region of Poland (Augustów or Morąg) were discriminated by K, Na, Mg, Ca, Fe, Zn, Cu, Mn and Cd. The results enabled an assessment of the hypothetical percentage realisation of the recommended dietary intake (RDA) for the bio-elements in question and of provisional tolerable weekly intakes (PTWI) of toxic metals from the consumption of 100 g of mushrooms. The most abundant element in all the mushroom samples was K, especially in Gomphidius glutinosus (Schaeff. ex Fr.) (Umeå - Sweden) and Cantharellus cibarius (Poland - Morąg). Lycoperdon perlatum (Pers.) from Poland and Sweden tended to accumulate the highest levels of Mg, Fe, Zn and Cu. The highest percentage of RDA was obtained for K, Mg and Cu. Based on the estimated PTWI, it can be concluded that no health hazard is associated with the consumption of these mushrooms.

Application of vibrational spectroscopy for classification, authentication and quality analysis of mushroom: A concise review

Chemical compositions of mushrooms are greatly dependent on the geographical region, and also the different parts of the same mushroom have different chemical constitutions. Several chemical methods are employed for quality control of mushrooms. However, these methods are destructive, require skilled personnel and are time consuming. To overcome these limitations researchers are aiming for vibrational spectroscopic techniques. This review is focused on various studies related to the application of vibrational spectroscopy for classification, authentication and quality analysis of mushrooms. It was concluded that vibrational spectroscopy could be efficiently employed for assessing the quality, authenticity and geographical origin of the mushrooms. Fourier-transform infrared (FTIR) and near infrared (NIR) spectroscopy were the most explored, whereas, Raman spectroscopy is the least explored technique in this field. Compact and cost-effective spectrometers based on the selective wavelengths have to be designed and installed at commercial and industrial level for rapid quality control of mushrooms.

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.

Food fingerprints - A valuable tool to monitor food authenticity and safety

In recent years, food frauds and adulterations have increased significantly. This practice is motivated by fast economical gains and has an enormous impact on public health, representing an important issue in food science. In this context, this review has been designed to be a useful guide of potential biomarkers of food authenticity and safety. In terms of food authenticity, we focused our attention on biomarkers reported to specify different botanical or geographical origins, genetic diversity or production systems, while at the food safety level, molecular evidences of food adulteration or spoilage will be highlighted. This report is the first to combine results from recent studies in a format that allows a ready overview of metabolites (<1200 Da) and potentially molecular routes to monitor food authentication and safety. This review has therefore the potential to unveil important aspects in food adulteration and safety, contributing to improve the current regulatory frameworks.

Cyclooxygenases and lipoxygenases are used by the fungus Podospora anserina to repel nematodes

Oxylipins are secondary messengers used universally in the living world for communication and defense. The paradigm is that they are produced enzymatically for the eicosanoids and non-enzymatically for the isoprostanoids. They are supposed to be degraded into volatile organic compounds (VOCs) and to participate in aroma production. Some such chemicals composed of eight carbons are also envisoned as alternatives to fossil fuels. In fungi, oxylipins have been mostly studied in Aspergilli and shown to be involved in signalling asexual versus sexual development, mycotoxin production and interaction with the host for pathogenic species. Through targeted gene deletions of genes encoding oxylipin-producing enzymes and chemical analysis of oxylipins and volatile organic compounds, we show that in the distantly-related ascomycete Podospora anserina, isoprostanoids are likely produced enzymatically. We show the disappearance in the mutants lacking lipoxygenases and cyclooxygenases of the production of 10-hydroxy-octadecadienoic acid and that of 1-octen-3-ol, a common volatile compound. Importantly, this was correlated with the inability of the mutants to repel nematodes as efficiently as the wild type. Overall, our data show that in this fungus, oxylipins are not involved in signalling development but may rather be used directly or as precursors in the production of odors against potential agressors.

SIGNIFICANCE

We analyzse the role in inter-kingdom communication of lipoxygenase (lox) and cyclooxygenase (cox) genes in the model fungus Podospora anserina. Through chemical analysis we define the oxylipins and volatile organic compounds (VOCs)produce by wild type and mutants for cox and lox genes, We show that the COX and LOX genes are required for the production of some eight carbon VOCs. We show that COX and LOX genes are involved in the production of chemicals repelling nematodes. This role is very different from the ones previously evidenced in other fungi.

Aroma-volatile profile of black morel (Morchella importuna) grown in Israel

BACKGROUND

A headspace solid-phase microextraction method with gas chromatography-mass spectrometry was used to profile the aroma volatiles of mature fruiting bodies of Morchella importuna grown in Israel.

RESULTS

We tentatively identified 40 aroma compounds and seven unknown volatiles. The M. importuna aroma profile consisted of 14 aldehydes, six alcohols, 10 methyl esters, four heterocyclic/sulfur compounds, 10 carbohydrates and three other compounds (i.e. one acid, one ketone and one butyl ester). The most abundant volatiles were carbohydrates, with a total relative peak area of 29.3%, followed by alcohols (27.7%), aldehydes (21.6%), methyl esters (10.8%), heterocyclic/sulfur compounds (3.1%) and other compounds (5.8%). The 8-carbon (C8) compounds imparting typical mushroom-like aroma were very abundant in M. importuna, accounting for 27.9% of the total peak area and including, amongst others, 1-octen-3-ol (80% of total C8), octanal and 2-octenal (Z- and E-).

CONCLUSION

The aroma volatile profile of morels has much in common with that of other mushrooms, with a few unique characteristics. To our knowledge, this is the first detailed report of the aroma profile of M. importuna. © 2017 Society of Chemical Industry.

Ultraviolet spectroscopy combined with ultra-fast liquid chromatography and multivariate statistical analysis for quality assessment of wild Wolfiporia extensa from different geographical origins

A quality assessment system comprised of a tandem technique of ultraviolet (UV) spectroscopy and ultra-fast liquid chromatography (UFLC) aided by multivariate analysis was presented for the determination of geographic origin of Wolfiporia extensa collected from five regions in Yunnan Province of China. Characteristic UV spectroscopic fingerprints of samples were determined based on its methanol extract. UFLC was applied for the determination of pachymic acid (a biomarker) presented in individual test samples. The spectrum data matrix and the content of pachymic acid were integrated and analyzed by partial least squares discriminant analysis (PLS-DA) and hierarchical cluster analysis (HCA). The results showed that chemical properties of samples were clearly dominated by the epidermis and inner part as well as geographical origins. The relationships among samples obtained from these five regions have been also presented. Moreover, an interesting finding implied that geographical origins had much greater influence on the chemical properties of epidermis compared with that of the inner part. This study demonstrated that a rapid tool for accurate discrimination of W. extensa by UV spectroscopy and UFLC could be available for quality control of complicated medicinal mushrooms.

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

Tricholoma matsutake is a commercially important edible fungus. Volatile compounds, chemical compositions, and nutritional values of fruiting bodies at different stages of maturity from different geographical areas were analyzed. The main volatile compounds in T. matsutake fruiting bodies were (E)-2-octenal, phenylacetaldehyde, 3-octanone, methyl cinnamate, benzaldehyde, and 1- octen-3-ol. Kinds and levels of volatile compounds from different geographical areas varied. As the fruiting bodies aged, levels of methyl cinnamate and 1-octen-3-ol gradually declined. Potassium was the most abundant element in T. matsutake fruiting bodies. Of 17 amino acids detected in fruiting bodies, glutamate was the most abundant. Volatile compounds, chemical compositions, and nutritional values of T. matsutake varied with age and geographical origin and can serve as chemical indicators for classication of T. matsutake from different geographical areas and at different stages of maturity.

Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)

The olive fly, Bactrocera oleae (Rossi), is a monophagous pest that displays an oviposition preference among cultivars of olive (Olea europaea L.). To clarify the oviposition preference, the olive leaf volatiles of three olive cultivars (Cobrançosa, Madural and Verdeal Transmontana) were assessed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) at six different periods of olive fruit maturation and degrees of infestation. A total of 39 volatiles were identified, mainly esters and alcohols, with a minor percentage of aldehydes, ketones and terpenic compounds, including sesquiterpenes. At sampling dates with higher degrees of infestation, cv. Cobrançosa had, simultaneously, significantly lower infestation degrees and higher volatile amounts than the other two cultivars, with a probable deterrent effect for oviposition. The green leaf volatiles (GLVs) (Z)-3-hexen-1-ol and (Z)-3-hexen-1-ol acetate) were the main compounds identified in all cultivars, together with toluene. The abundance of GLVs decreased significantly throughout maturation, without significant differences among cultivars, while toluene showed a general increase and positive correlation with olive fly infestation levels. The results obtained could broaden our understanding of the roles of various types and amounts of olive volatiles in the environment, especially in olive fly host selection and cultivar preference.

Olive Volatiles from Portuguese Cultivars Cobrançosa, Madural and Verdeal Transmontana: Role in Oviposition Preference of Bactrocera oleae (Rossi) (Diptera: Tephritidae)

The olive fly, Bactrocera oleae (Rossi), a serious threat to the olive crop worldwide, displays ovipositon preference for some olive cultivars but the causes are still unclear. In the present work, three Portuguese olive cultivars with different susceptibilities to olive fly (Cobrançosa, Madural, and Verdeal Transmontana) were studied, aiming to determine if the olive volatiles are implicated in this interaction. Olive volatiles were assessed by SPME-GC-MS in the three cultivars during maturation process to observe possible correlations with olive fly infestation levels. Overall, 34 volatiles were identified in the olives, from 7 chemical classes (alcohols, aldehydes, aromatic hydrocarbons, esters, ketones, sesquiterpenes, and terpenes). Generally, total volatile amounts decrease during maturation but toluene, the main compound, increased in all cultivars, particularly in those with higher susceptibility to olive fly. Sesquiterpenes also raised, mainly α-copaene. Toluene and α-copaene, recognized oviposition promoters to olive fly, were correlated with the infestation level of cvs. Madural and Verdeal Trasnmontana (intermediate and highly susceptible cultivars respectively), while no correlations were established with cv. Cobrançosa (less susceptible). No volatiles with inverse correlation were observed. Volatile composition of olives may be a decisive factor in the olive fly choice to oviposit and this could be the basis for the development of new control strategies for this pest.

Characteristic Fingerprint Based on Low Polar Constituents for Discrimination of Wolfiporia extensa according to Geographical Origin Using UV Spectroscopy and Chemometrics Methods

The fungus species Wolfiporia extensa has a long history of medicinal usage and has also been commercially used to formulate nutraceuticals and functional foods in certain Asian countries. In the present study, a practical and promising method has been developed to discriminate the dried sclerotium of W. extensa collected from different geographical sites based on UV spectroscopy together with chemometrics methods. Characteristic fingerprint of low polar constituents of sample extracts that originated from chloroform has been obtained in the interval 250-400 nm. Chemometric pattern recognition methods such as partial least squares discriminant analysis (PLS-DA) and hierarchical cluster analysis (HCA) were applied to enhance the authenticity of discrimination of the specimens. The results showed that W. extensa samples were well classified according to their geographical origins. The proposed method can fully utilize diversified fingerprint characteristics of sclerotium of W. extensa and requires low-cost equipment and short-time analysis in comparison with other techniques. Meanwhile, this simple and efficient method may serve as a basis for the authentication of other medicinal fungi.

Validated modeling for German white wine varietal authentication based on headspace solid-phase microextraction online coupled with gas chromatography mass spectrometry fingerprinting

An untargeted analytical approach combined with chemometrics using the volatiles of German white wine was investigated regarding the usefulness for verifying botanical origin. A total of 198 wine samples of Riesling, Müller-Thurgau, Silvaner, Pinot Gris, and Pinot Blanc were examined applying headspace solid-phase microextraction online coupled with gas chromatography mass spectrometry. The resultant three-dimensional raw data were processed by available metabolomics software. After data treatment, a partial least-squares discriminant analysis (PLS-DA) model was validated. External samples were correctly classified for 97% Silvaner, 93% Riesling, 91% Pinot Gris/Blanc, and 80% Müller-Thurgau. This model was related to monoterpenoids, C13-norisoprenoids, and esters. Further, 100% prediction for a two-class model of Riesling versus Pinot Gris/Blanc was confirmed by 74 additional samples measured independently. Hence, the strategy applied was, in particular, reliable and relevant for white wine varietal classification. In addition, the superior classification performance of the Riesling class was revealed.