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

Novel Post-Harvest Preservation Techniques for Edible Fungi: A Review

Edible fungi are well known for their rich nutrition and unique flavor. However, their post-harvest shelf-life is relatively short, and effective post-harvest preservation techniques are crucial for maintaining their quality. In recent years, many new technologies have been used for the preservation of edible fungi. These technologies include cold plasma treatment, electrostatic field treatment, active packaging, edible coatings, antimicrobial photodynamic therapy, and genetic editing, among others. This paper reviews the new methods for post-harvest preservation of mainstream edible fungi. By comprehensively evaluating the relative advantages and limitations of these new technologies, their potential and challenges in practical applications are inferred. The paper also proposes directions and suggestions for the future development of edible fungi preservation, aiming to provide reference and guidance for improving the quality of edible fungi products and extending their shelf-life.

Metabolomics and HS-SPME-GC-MS-based analysis of quality succession patterns and flavor characteristics changes during the fermentation of Lycium barbarum and Polygonatum cyrtonema compound wine

This work set out to investigate how the physicochemical markers, volatiles, and metabolomic characteristics of mixed fermented the fermentation of Lycium barbarum and Polygonatum cyrtonema compound wine (LPCW) from S. cerevisine RW and D. hansenii AS2.45 changed over the course of fermentation. HS-SPME-GC-MS combined with non-targeted metabolomics was used to follow up and monitor the fermentation process of LPCW. In total, 43 volatile chemical substances, mostly alcohols, esters, acids, carbonyl compounds, etc., were discovered in LPCW. After 30 days of fermentation, phenylethyl alcohol had increased to 3045.83 g/mL, giving off a rose-like fresh scent. The biosynthesis of valine, leucine, and isoleucine as well as the metabolism of alanine, aspartic acid, and glutamic acid were the major routes that led to the identification of 1385 non-volatile components in total. This study offers a theoretical foundation for industrial development and advances our knowledge of the fundamental mechanism underlying flavor generation during LPCW fermentation.

Key components, formation pathways, affecting factors, and emerging analytical strategies for edible mushrooms aroma: A review

Aroma is one of the decisive factors affecting the quality and consumer acceptance of edible mushrooms. This review summarized the key components and formation pathways of edible mushroom aroma. It also elaborated on the affecting factors and emerging analytical strategies of edible mushroom aroma. A total of 1308 volatile organic compounds identified in edible mushrooms, 61 were key components. The formation of these compounds is closely related to fatty acid metabolism, amino acid metabolism, lentinic acid metabolism, and terpenoid metabolism. The aroma profiles of edible mushrooms were affected by genetic background, preharvest factors, and preservation methods. Molecular sensory science and omics techniques are emerging analytical strategies to reveal aroma information of edible mushrooms. This review would provide valuable data and insights for future research on edible mushroom aroma.

Allelopathy and Identification of Volatile Components from the Roots and Aerial Parts of Astragalus mongholicus Bunge

The volatile compounds produced by plants play an important role in plant growth, plant communication, and resistance to biological and abiotic stresses. Astragalus membranaceus var. mongholicus (AM) is a perennial herbaceous plant (Leguminosae) that is widely cultivated in northwest China. The bioactive compounds in its root have shown various pharmacological activities. Root rot disease caused by Fusarium spp. often occurs in AM planting with increasing severity in continuous monoculture. It is currently still unclear what are the effects of the volatile compounds produced by fresh AM on itself, other crops cultivated on the same field after AM, pathogen, and rhizobia. In this study, we found that seed germination and seedling growth of AM, lettuce (Lactuca sativa L.), and wheat (Triticum aestivum L.) could be affected if they were in an enclosed space with fresh AM tissue. Additionally, 90 volatile compounds were identified by SPME-GC-MS from whole AM plant during the vegetative growth, 36 of which were specific to aerial parts of AM (stems and leaves, AMA), 17 to roots (AMR), and 37 were found in both AMA and AMR. To further identify the allelopathic effects of these volatile compounds, five compounds (1-hexanol, (E)-2-hexenal, (E,E)-2,4-decadienal, hexanal, and eugenol) with relatively high content in AM were tested on three receptor plants and two microorganisms. We found that (E,E)-2,4-decadienal and (E)-2-hexenal showed significant inhibitory effects on the growth of AM and lettuce. One-hexanol and hexanal suppressed the growth of wheat, while eugenol showed a similar effect on all three plant species. Moreover, the activities of these compounds were dose dependent. Notably, we discovered that (E)-2-hexenal and eugenol also inhibited the growth of the pathogen Fusarium solani by as high as 100%. Meanwhile, all five compounds tested suppressed the rhizobia Sinorhizobium fredii. In summary, this study furthered our understanding of the comprehensive allelopathic effects of the main volatile components of AM.

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.

Integrated meta-omics approaches reveal Saccharopolyspora as the core functional genus in huangjiu fermentations

Identification of the core functional microorganisms in food fermentations is necessary to understand the ecological and functional processes for making those foods. Wheat qu, which provides liquefaction and saccharifying power, and affects the flavor quality, is a key ingredient in ancient alcoholic huangjiu fermentation, while core microbiota of them still remains indistinct. In this study, metagenomics, metabolomics, microbial isolation and co-fermentation were used to investigate huangjiu. Although Aspergillus is usually regarded as core microorganism in wheat qu to initiate huangjiu fermentations, our metagenomic analysis showed that bacteria Saccharopolyspora are predominant in wheat qu and responsible for breakdown of starch and cellulose. Metabolic network and correlation analysis showed that Saccharopolyspora rectivirgula, Saccharopolyspora erythraea, and Saccharopolyspora hirsuta made the greatest contributions to huangjiu's metabolites, consisting of alcohols (phenylethanol, isoamylol and isobutanol), esters, amino acids (Pro, Arg, Glu and Ala) and organic acids (lactate, tartrate, acetate and citrate). S. hirsuta J2 isolated from wheat qu had the highest amylase, glucoamylase and protease activities. Co-fermentations of S. hirsuta J2 with S. cerevisiae HJ resulted in a higher fermentation rate and alcohol content, and huangjiu flavors were more similar to that of traditional huangjiu compared to co-fermentations of Aspergillus or Lactiplantibacillus with S. cerevisiae HJ. Genome of S. hirsuta J2 contained genes encoding biogenic amine degradation enzymes. By S. hirsuta J2 inoculation, biogenic amine content was reduced by 45%, 43% and 62% in huangjiu, sausage and soy sauce, respectively. These findings show the utility of Saccharopolyspora as a key functional organism in fermented food products.

Expression of terpene synthase-related genes in parents and offspring of Flammulina filiformis based on differences in volatile aroma components

Flammulina filiformis (F. filiformis) is one of the four major edible types of fungus in the world and has been cultivated in China since 800 CE (Anno Domini). Some of the most essential criteria for evaluating the quality of F. filiformis are the types and contents of volatile components present. A focused study on screened the terpene synthase genes involved in the aroma of offspring and compared key terpenoids between parents and offspring, which is helpful for the development and application of F. filiformis. Firstly, the volatile aroma components of parent and offspring F. filiformis were extracted using two pretreatment procedures, and then were semi-quantified by an internal standard. Forty-eight, fifty-eight, and forty-eight volatile compounds were identified in parents and offspring of three different strains, and 15, 22, and 12 aroma compounds (OAVs ≥ 1) were further screened out via calculating their odor activity values (OAVs). Terpenoids, in particular linalool and eucalyptol, which contribute more to the aroma, result in the unique green and grassy aroma of the offspring. At last, the F. filiformis genome was resequenced and the coordinates of genes related to terpenoid synthase were determined. The results showed that Scaffolds, including scaffold3.t874 and scaffold9.t157 were connected to terpenoid synthesis of offspring (No. 61523). The variant genes g269 and g61 were related to terpenoid synthase sequences. This study provides a theoretical foundation for the cultivation of more diverse and unique varieties of F. filiformis.

Biosynthesis, behavior and fate of volatile organic sulfide in Lentinus edodes (Berk.) upon hot-air drying treatment

This study elucidated the biosynthesis and changing behaviors of organic sulfide in shiitake mushrooms upon hot-air drying treatment. The changes of aw, moisture migration, contours of taste and flavor, organic sulfide, and 4 key enzyme activities were monitored throughout three drying procedures (CT/ST1/ST2). Results showed that drying rate was related to the moisture migration. Key enzymes of γ-GTase, ASFase and CS lyase were heat-resistant proteases, while C-Dase exhibited low thermal stability with the activity decreased during treatment. A total of 17 organic sulfides were identified and PLS analyses suggested 6 cyclic polysulfides were formed by C-Dase desulfurization, while 5 thioethers generation were related to the thermal cleavage of direct precursors (straight-chain di/tris/tetrasulfonyl esters) and Maillard reaction. These results indicated that ST2 drying procedures had a positive effect on the formation of cyclic polysulfides at the end of drying pried and the achievement of premium flavor qualities.

High impacts of cultivar and home-cooking practice on the content of free myo-inositol, a bioavailable health-promoting cyclitol, in sweet potato

Free myo-inositol is a bioavailable form of a cyclitol having various health-promoting activities. The impact of cultivar and home-cooking practice on the content of free myo-inositol in sweet potatoes (12 cultivars grown in 2 different locations) was studied. A GC-MS/MS method following in situ trimethylsilylation was established and validated to determine free myo-inositol. The established analytical method was sensitive, precise, and accurate. It was found that free myo-inositol content in sweet potato varied greatly (sevenfolds) with cultivar, ranging from 377.1 to 2628.3 mg/kg dw. A cultivar Poongwon-mi was found to be an exceptionally rich source of free myo-inositol (2628.3 mg/kg dw). Home-cooking practice markedly increased free myo-inositol content (maximum 240%). Baking showed the highest impact on the increase in free myo-inositol, followed by steaming, microwave cooking, and boiling, in decreasing order. This represents the first report of the remarkably high impact of cultivar and home-cooking practice on the free myo-inositol content in sweet potato. PRACTICAL APPLICATION: The free myo-inositol content in sweet potato varied greatly with the cultivars. Poongwon-mi contained a surprisingly high content of free myo-inositol. Home-cooking dramatically increased the free myo-inositol content.

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 Process on the Volatile and Non-Volatile Flavor Compounds of Lentinula edodes

In this study, fresh Lentinula edodes was dehydrated using freeze-drying (FD), hot-air drying (HAD), and natural drying (ND), and the volatile and non-volatile flavor compounds were analyzed. The drying process changed the contents of eight-carbon compounds and resulted in a weaker “mushroom flavor” for dried L. edodes. HAD mushrooms had higher levels of cyclic sulfur compounds (56.55 μg/g) and showed a stronger typical shiitake mushroom aroma than those of fresh (7.24 μg/g), ND (0.04 μg/g), and FD mushrooms (3.90 μg/g). The levels of 5′-nucleotide increased, whereas the levels of organic acids and free amino acids decreased after the drying process. The dried L. edodes treated with FD had the lowest levels of total free amino acids (29.13 mg/g). However, it had the highest levels of umami taste amino acids (3.97 mg/g), bitter taste amino acids (6.28 mg/g) and equivalent umami concentration (EUC) value (29.88 g monosodium glutamate (MSG) per 100 g). The results indicated that FD was an effective drying method to produce umami flavor in dried mushrooms. Meanwhile, HAD can be used to produce a typical shiitake mushroom aroma. Our results provide a theoretical basis to manufacture L. edodes products with a desirable flavor for daily cuisine or in a processed form.

Research advance in gas detection of volatile organic compounds released in rice quality deterioration process

Rice quality deterioration will cause grievous waste of stored grain and various food safety problems. Gas detection of volatile organic compounds (VOCs) produced by deterioration is a nondestructive detection method to judge rice quality and alleviate rice spoilage. This review discussed the research advance of VOCs detection in terms of nondestructive detection methods of rice quality deterioration, applications of VOCs in grain detection, inspection of characteristic gas produced during rice spoilage, rice deterioration prevention and control, and detection of VOCs released by rice mildew and insect attack. According to the main causes of rice quality deterioration and major sources of VOCs with off-odor generated during rice storage, deterioration can be divided into mold and insect infection. The results of literature manifested that researches mainly focused on the infection of Aspergillus in the mildew process and the attack of certain pests in recent years, thus the research scope was limited. In this paper, the gas detection methods combined with the chemometrics to qualitatively analyze the VOCs, as well as the correlation with the number of colonies and insects were further studied based on the common dominant strains during rice mildew, that is, Aspergillus and Penicillium fungi, and the common pests during storage, that is, Sitophilus oryzae and Rhyzopertha dominica. Furthermore, this paper pointed out that the quantitative determination of characteristic VOCs, the numeration relationship between VOCs and the degree of mildew and insect infestation, the further expansion of detection range, and the application of degraded rice should be the spotlight of future research.

Recent Advances in Sensing Applications of Molecularly Imprinted Photonic Crystals

Photonic crystals (PhCs) with a brightly colored structure are novel materials and are widely used in chemical and biological sensing. Combining PhCs with molecular imprinting technology (MIT), the molecularly imprinted PhC (MIPC) sensors are fabricated, which can specifically recognize the target molecules. Aside from high sensitivity and selectivity, the MIPC sensors could recognize the naked eye detection because of its optical properties. In this review, an overview of recent advances in sensing applications of MIPC sensors including the responsive mechanisms, application in environmental monitoring, and the application to human health were illustrated. The MIPC sensors all responded to the analytes specifically and also showed high sensitivity in real samples, which provided a method to realize the rapid, convenient, naked eye, and real-time detection. Furthermore, the current limitations and potential future directions of MIPC sensors were also discussed.

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.