Advances in the Role and Mechanisms of Essential Oils and Plant Extracts as Natural Preservatives to Extend the Postharvest Shelf Life of Edible Mushrooms

China has a large variety of edible mushrooms and ranks first in the world in terms of production and variety. Nevertheless, due to their high moisture content and rapid respiration rate, they experience constant quality deterioration, browning of color, loss of moisture, changes in texture, increases in microbial populations, and loss of nutrition and flavor during postharvest storage. Therefore, this paper reviews the effects of essential oils and plant extracts on the preservation of edible mushrooms and summarizes their mechanisms of action to better understand their effects during the storage of mushrooms. The quality degradation process of edible mushrooms is complex and influenced by internal and external factors. Essential oils and plant extracts are considered environmentally friendly preservation methods for better postharvest quality. This review aims to provide a reference for the development of new green and safe preservation and provides research directions for the postharvest processing and product development of edible mushrooms.


Introduction
Edible mushrooms are a delicious and healthy food owing to their richness in protein, amino acids, and polysaccharides [1][2][3]. The global production of edible mushrooms is now largely stable, and with the development of the edible mushroom industry, their world trade is also increasing, contributing widely to human living standards [4]. China is one of the world's largest producers and exporters of wild edible mushrooms [5]. The value of cultivated mushroom production ranks in the top five after grain, vegetable, fruit, and edible oil plantations and is higher than the sugar, cotton, and tobacco industries [6]. However, due to the high water content of edible mushrooms, the respiratory and metabolic rates are fast and the tissue of the seeds is tender and susceptible to mechanical damage and microbial contamination during the storage process, resulting in browning and quality decline [7][8][9][10].
Various preservation strategies are widely used to extend the shelf life of mushrooms. Among these are various physical treatments, including irradiation [11], atmosphere packaging [12][13][14], ultrasonication [11,15], high-voltage electric field treatment [16,17], and pulsed light treatment [18][19][20]. It is well known that operational complexity and energy consumption issues are important factors limiting the industrial application of these traditional physical methods. For instance, radiation treatment places high demands on the operator's technical requirements and safety assessment, while gas conditioning treatment involves high concentrations of CO 2 , with potential CO 2 hazard risks for the operator. Traditional chemical methods (use of preservatives for freshness) [21,22] are gradually creating challenges in terms of consumer acceptance because of their potential negative impact on the environment and human health [23]. To develop safe, environmentally friendly, and effective techniques for maintaining the postharvest quality of edible mushrooms, a great

Respiration Rate
In respiration, O2 levels influence respiratory metabolic processes, and the postharvest storage quality of edible mushrooms depends on the respiration rate [10,39]. The maintenance of a relatively low respiration rate, therefore, plays a vital role in extending the shelf life of edible mushrooms [40][41][42]. The respiration rate of mushrooms is influenced by the storage temperature and time [43]. In general, the higher the storage temperature, the higher the respiration rate of postharvest mushrooms [44]. Edible mushrooms have a high respiration rate  kg·h −1 at 20 °C and 5 °C, respectively) due to their thin and porous epidermal structure [44]. Microbial spoilage increases during postharvest mushroom storage, promoting increased respiration rates, dehydration, browning, and microbial growth due to physiological stress from microbial or pest infestations [45]. In addition, the postharvest storage process is an abiotic stress on mushrooms, leading to the inhibition of electron transfer in the mitochondria and an increase in the production of reactive oxygen species (ROS) [45]. When ROS levels exceed the cell's antioxidant capacity, oxidative stress occurs and causes damage to lipids, membranes, proteins, and DNA, which is mediated by cellular structures (e.g., mitochondria) [40,[46][47][48]. Typically, respiration directly affects changes in mitochondrial membrane enzymes associated with respiratory metabolism, such as cytochrome C oxidase (CCO) and

Microbial Infestations
During the postharvest period, edible mushrooms are exposed to a wide range of microorganisms, such as bacteria and fungi, due to their lack of protective epidermal tissue and high water content, resulting in many changes in enzyme activity [53] (Figure 1). Bacteria such as Pseudomonas tolaasii [54][55][56], Bacillus subtili [57,58], Pseudomonas fluoresens [13,54,[59][60][61], and Listeria monocytogenes [57,58,61,62] are the main bacteria infecting edible mushrooms. Additionally, mold is another microorganism that can cause infection in edible mushrooms [10,57,63,64]. The negative effects of diseases caused by fungi such as Lecanicillium funccola [65], Cladobotryum spp., Mycogone perniciosa, and Trichoderma spp. also limit yields and harvest quality [66]. During physiological stress from microbial or pest infestations, peroxidase (POD) and catalase (CAT) are activated [67][68][69], leading to adverse changes in plant texture, taste, or odor and possibly to browning [44,70,71] (Figure 1). Temperature and relative humidity play an important role in the growth of microorganisms and are also the main factors influencing the browning of mushrooms [72,73]. The various nutrients (polysaccharides, aldehydes, and phenolic compounds), quality characteristics, and microbial reproduction in mushrooms are influenced by temperature [52,73]. Generally, increasing the storage temperature accelerates the aging, browning, weight loss, and texture softening of mushrooms. Low temperatures are recommended for the postharvest storage of mushrooms. The optimum storage temperature for edible mushrooms is generally around 4 • C, but cold damage can occur if the storage temperature is below 0 • C [73,74]. In addition, the temperature can affect the enzyme activity and, thus, the spoilage of mushrooms [73]. For example, the amount of ascorbic acid depends on the intensity of the oxidation process of ascorbate oxidase caused by enzymatic activity, and the spoilage and ripening of the crop is strongly influenced by it, while the ascorbic acid concentration in the plant depends on the storage time, the temperature during storage, and the amount of oxygen in the atmosphere [75] (Figure 1). Relative humidity (RH) significantly affects moisture loss in mushrooms; the lower the RH, the faster the moisture loss. The use of a higher RH under storage conditions helps to minimize postharvest mushroom quality losses [9,14]. A high RH (85%-95%) should be maintained in all cases [9,76] (Figure 1).

Mechanical Damage
Mushrooms do not have a cuticle to protect them from physical or microbial attack and moisture loss [9]. Therefore, they are susceptible to mechanical damage and a reduced shelf life during postharvest handling and various modes of transportation [37]. Mechanical damage caused by postharvest mushroom cutting treatments can disrupt the integrity of the cell membrane and induce the production of excess ROS. Elevated levels of ROS may lead to membrane lipid peroxidation, resulting in a loss of membrane integrity and cellular compartmentalization. Moreover, this allows the PPO in the plastids to mix with the phenols present in the vesicles, which manifests as browning [77] (Figure 1).

Mechanism of Action and Application of EOs and Plant Extracts for the Preservation of Edible Mushrooms
Edible films and coatings are biopolymer-based packaging materials that may be consumed after food application. They are manufactured by homogenizing a composite aqueous solution in the presence of a plasticizer, followed by casting and evaporation of the water. Plant extracts can also be easily incorporated to produce a biologically active form of "active packaging". Moreover, plant extracts are often used in edible films because they are generally safe at low concentrations.
In recent years, with the increasing consumption of edible mushrooms worldwide, the demand for improvements in their quality has led to the widespread use of environmentally and economically friendly methods in the preservation of edible mushrooms. In this regard, the impact of EOs and plant extracts in extending the shelf life of edible mushrooms holds great promise.

Application of EOs in Edible Mushroom Preservation
Plant EOs are commonly found in all parts of plants, including the roots, trunks, bark, stems, leaves, flowers, and fruits. They can be considered as potential alternatives to synthetic agents such as butyl-hydroxytoluene, which is classified as GRAS and approved by the US Food and Drug Administration [78]. EOs may contain terpenes, aldehydes, fatty acids, phenols, ketones, esters, and alcohols with food-preserving effects [79]. They have broad-spectrum antibacterial activity and excellent antioxidant properties; some also have a refreshing aroma [80,81]. Due to their volatility, EOs only last a short time [82], but they can be encapsulated in a slow-release system for their sustained release [79,83] (Figure 2, Table 1). thetic agents such as butyl-hydroxytoluene, which is classified as GRAS and approved by the US Food and Drug Administration [78]. EOs may contain terpenes, aldehydes, fatty acids, phenols, ketones, esters, and alcohols with food-preserving effects [79]. They have broad-spectrum antibacterial activity and excellent antioxidant properties; some also have a refreshing aroma [80,81]. Due to their volatility, EOs only last a short time [82], but they can be encapsulated in a slow-release system for their sustained release [79,83] (Figure 2, Table 1).

Figure 2.
Forms of essential oils applied to the preservation of edible mushrooms ((I) Schematic diagram of the formation of an essential oil slow-release system and its application form in the preservation of edible mushrooms; (II) the main components of essential oils used to preserve edible mushrooms; (III) changes in edible mushroom quality after essential oil treatment. (A) Agaricus bisporus after chitosan/zeaxolysin/lemon essential oil composite film treatment [70]; (B) Agaricus bisporus after treatment with cinnamon essential oil [84]; (C) Agaricus bisporus after starch/cinnamon essential oil composite film treatment [85]. Copyright 2021, Elsevier.) Figure 2A created with Bio-Render.com.

Figure 2.
Forms of essential oils applied to the preservation of edible mushrooms ((I) Schematic diagram of the formation of an essential oil slow-release system and its application form in the preservation of edible mushrooms; (II) the main components of essential oils used to preserve edible mushrooms; (III) changes in edible mushroom quality after essential oil treatment. (A) Agaricus bisporus after chitosan/zeaxolysin/lemon essential oil composite film treatment [70]; (B) Agaricus bisporus after treatment with cinnamon essential oil [84]; (C) Agaricus bisporus after starch/cinnamon essential oil composite film treatment [85]. Copyright 2021, Elsevier.) Figure 2A created with BioRender.com.  (2) C/Z/L0 (LEO 0% (w/w)) of total solids; C/Z/L-3 (LEO 3%); C/Z/L-6 (LEO 6%); C/Z/L-9 (LEO 9%); C/Z/L-12 (LEO 12%) of total solids 12 d    Storage temperature: LEO is extracted from citrus lemons and is used as a food preservative, flavoring agent, and preservative due to its good antioxidant and antibacterial properties [103]. Wang et al. incorporated various concentrations of LEO into chitosan/zeaxolysin composite membranes (C/Z/L membranes), which had strong antibacterial and antioxidant activities due to inhibiting the respiration rate and microbial growth, to slow down the aging process of Agaricus bisporus and maintain postharvest quality [70]. It was seen that the addition of LEO effectively increased the antioxidant and antimicrobial activities of C/Z films. Throughout the storage period (4 • C, 12 d), mushrooms packed in films with 6% LEO exhibited the lowest browning index and respiration rate, effectively maintained antioxidant capacity, improved tissue hardness, and inhibited the browning process by inhibiting PPO and POD activities. At the same time, inhibition experiments showed that C/Z/L films exhibited good inhibition activity against food-borne pathogenic bacteria (Escherichia coli and Staphylococcus aureus) [70].

Oregano Essential Oil (OEO)
The main component of OEO is carvacrol, which has excellent biological activities, such as antibacterial and antioxidant properties [104][105][106]. Due to its importance in the food, pharmaceutical, and cosmetic industries, the demand for OEO has been growing steadily in the global market [107]. Salgueiro et al. reported that OEO completely inhibited the growth of Candida albicans at a concentration of 0.25 mg/mL and was also fungicidal against S. aureus. In addition, the phenolic hydroxyl group of carvacrol could act as a donor for peroxide radicals during oxidation, preventing lipid peroxidation chain reactions and protecting lipids from oxidation [108,109]. Cui et al. prepared OEO-MSNPs/SA films at different concentrations by embedding OEO into mesoporous silica nanoparticles (MSNPs) and incorporating them into sodium alginate (SA), which exhibited strong intermolecular interactions through hydrogen bonding, resulting in biofilms with excellent mechanical and water resistance properties, as well as antioxidant and antibacterial activities [105]. A recent study by Lu et al. showed that SA membranes with 1.0 wt% OEO-MSNPs had the highest antioxidant capacity in 95% ethanol food simulants, with an oxidation inhibition rate of 75.31%. SA membranes with 1.0 wt% OEO-MSNPs showed significant antibacterial activity against Curvularia lunata. It was seen that the higher the content of OEO-MSNPs, the greater the inhibition of microbial penetration and the better the storage and preservation of edible mushrooms. However, the reduced transparency means a tradeoff with the enhanced UV-blocking properties, and the decreased elasticity may lead to a restricted application scenario [90]. Further testing in this area should still be carried out to assess the suitability of the market packaging.

Cinnamon Essential Oil (CEO)
CEO is a natural volatile oil with strong antibacterial activity and is more widely used to preserve edible mushrooms [85,101,[110][111][112]. Gao et al. demonstrated that the fumigation of mushrooms with appropriate doses of CEO could reduce the rate of cap opening and inhibit the aging of mushrooms [111]. In terms of protein regulation, cinnamaldehyde (a component of CEO) can inhibit the transcription of effector and regulatory proteins [113]. Cinnamaldehyde has excellent antibacterial properties, altering the distribution of lipids in the cell membranes of pathogenic bacteria and disrupting them [114]. It effectively controls the growth of Salmonella typhimurium and inhibits the expression of the ATP synthase alpha chain protein during ATP production [115]. Furthermore, it inhibits the cell division of Bacillus cereus [116]. As EOs are inherently volatile and maintain a relatively short residence time, it is more common to use a slow-release form of CEO (e.g., microencapsulation technology) and then apply it to the preservation of edible mushrooms. In a study by Eliezer Louis et al., CEO microencapsulation was combined with paper-based materials to develop a bioactive paper for the preservation of edible mushrooms. It significantly inhibited the aging process of A. bisporus during cold storage, which was related to the antioxidant capacity of cinnamaldehyde and its antimicrobial capacity by reducing the droplet size to achieve uniform dispersion within the coating [84]. In addition, Shao et al. prepared bioactive packaging materials using starch/CEO microcapsules as a coating, which had good permeability and antibacterial properties, prevented water condensation and spoilage caused by water imbalance, and was successful in extending the shelf life of foods with high water content, such as A. bisporus [85]. Meanwhile, Zhang et al. prepared CEO-MSNP/potato starch films by mixing CEO-MSNPs in a potato starch matrix. The CEO-MSNPs in the films inhibited the pathogenicity of Trichoderma sp. F and Trichoderma annulate C by inducing the accumulation of intracellular reactive oxygen species and disrupting the integrity of the cell membrane [112]. SEM showed that CEO-MSNPs effectively disrupted the mycelial morphology of both molds and interfered with their normal growth. The expression levels of NOx genes in Trichoderma sp. F and Trichoderma annulate C significantly increased after treatment with CEO-MSNP (p < 0.01). One of the mechanisms of inhibition of these organisms by CEO-MSNPs may lie in the upregulation of nox1 and nox2 genes to produce large amounts of ROS [101,112]. Nair et al. prepared maize alcohol-soluble protein/ethyl cellulose hybrid nanofibers in different ratios while encapsulating CEO into electrospun fibers to preserve A. bisporus. This treatment effectively preserved the moisture and antioxidant capacity, enhanced antioxidant enzyme activity, reduced browning enzyme activity, delayed aging, and improved the shelf life of A. bisporus [117]. Pan et al. prepared a cross-linked electrospun polyvinyl alcohol/CEO/βcyclodextrin (CPVA-CEO-β-CD) nanofiber film for the sustained release of antibacterial drugs by encapsulating CEO in PVA-and β-CD-based fibers using electrostatic spinning, which could inhibit Gram-positive and Gram-negative bacteria and effectively extend their shelf life [99].
Whether for the CEO microcapsules of Shao et al. [85] or the CEO-MSNPs of Zhang et al. [112], or the nanoemulsions containing different concentrations of cinnamaldehyde produced by Eliezer et al. [84], the membrane permeability, ROS content, cellular component leakage, cellular component leakage, soluble sugars, and malondialdehyde (MDA) content after the addition of CEO at the lowest inhibitory concentration level were significantly changed. By incorporating cinnamaldehyde nanoemulsions into the coatings, the quality of the mushrooms was significantly improved, reducing the respiration rate, weight loss, PPO activity, and Pseudomonas population, and increasing the retention of the hardness, color, total polyphenols, and antioxidant capacity of the mushrooms-positive effects that may be related to the antioxidant capacity of CIN and improving its antimicrobial capacity by achieving uniform dispersion within the medium, thus significantly extending the shelf life of the mushrooms.

Cumin Essential Oil (CUEO)
Cumin (Cuminum cyminum L.) is an aromatic plant naturally cultivated in many countries, such as Iran, India, China, Japan, Morocco, and Egypt [118]. Cumin is the second most popular spice in the world after black pepper and has many applications in food [119]. CUEO, with its good antibacterial properties, is also used in the preservation of edible mushrooms [93,94,120]. Roghayeh Karimirad et al. prepared CUEO-chitosan nanoparticles (CUEO-CSNPs) using subcellular-sized chitosan trimeric phosphate (CS-TPP) as a controlled-release system to encapsulate EOs, a treatment that induced the synthesis of catalase (CAT), glutathione reductase (GR), and ascorbic acid and slowed down the increase in peroxidase activity [93]. The experimental data showed that the highest CAT and GR activities were observed in the samples containing CUEO-CSNPs after 15 days of storage. In contrast, the POD activity of the control samples peaked at the end of storage. Interestingly, the POD levels of the CUEO-CSNP-treated samples increased by 17.13% after 20 days compared to the initial levels of the enzymes mentioned above. At the end of storage, the levels of ascorbic acid in the CUEO-CSNP-treated samples were significantly higher than those in the control samples. Fumigation of A. bisporus with cumin seed oil extended its shelf life by 15 days with no significant reduction in antioxidant activity. Meanwhile, storage of A. bisporus at 4 • C using chitosan nanoparticles as a cumin oil delivery system reduced the microbial population, facilitated the maintenance of the antioxidant capacity, improved the tissue hardness, and inhibited the formation of brown patches compared to conventional packaging [93,94].

Thyme Essential Oil (TEO)
As a food-grade preparation, TEO has broad-spectrum antibacterial activity against pathogenic bacteria [121]. Zhu et al. evaluated the effects on the postharvest quality and antioxidant enzyme activity of Pholiota nameko mushroom by developing SA-based composite coatings enriched with or without TEO, lactobacillin, and L-cysteine for the preservation of P. nameko. In all experimental groups, the addition of 1% (V/V) TEO, 0.3 g/L cysteine, and 0.4 g/L lactic acid streptococin effectively controlled the senescence, growth of aerobic mesophilic bacteria, and deterioration of quality of P. nameko and they found that the SA-based coating effectively reduced the weight loss, cap opening, browning, MDA content, and total soluble phenol content compared to the untreated control. In addition, the appearance of peak SOD, POD, PPO, and CAT activities was delayed after the coating treatment. During storage, ascorbic acid, soluble sugars, protein, and PAL activities were higher in treated mushrooms than in untreated ones [122]. Thus, this demonstrates the positive effect of TEO on the storage and preservation of edible mushrooms.

Turmeric Essential Oil (TUEO)
Turmeric (Curcuma longa) is a medicinal plant of the Zingiberaceae family and is the most common spice used in cooking and many health products [123,124]. The biological activities of TUEO, including antitumor, antibacterial, anti-inflammatory, and antioxidant properties, have been demonstrated in several studies [125,126]. Valizadeh et al. evaluated the effect of TUEO and TUEO-incorporated chitosan nanoparticles (TUEO-CSNPs) on the shelf life of white mushrooms by inducing an increase in CAT and SOD activities. Mushrooms packed with TUEO-CSNPs and fumigated with TUEO were found to be significantly firmer and showed lower changes in color and microbial counts at day 15 of storage compared to untreated samples. In addition, TUEO-CSNP treatment showed the highest SOD, CAT, total phenolic, and ascorbic acid content and the lowest PPO activity (p < 0.01) [127]. Although the use of nanoparticles in Valizadeh's method would impose an additional cost on the packaging, the extended shelf life, maintenance of mushroom quality, and reduced crop losses can justify this additional cost.

Satureja khuzistanica Essential Oil (SKO)
Satureja khuzistanica is a traditional herb endemic among the nomadic population of Southwestern Iran (including the provinces of Ilam, Lorestan, and Khuzestan) [128,129]. It is used in herbal tea for its analgesic, antiseptic, and anti-inflammatory properties, especially for toothache problems [128]. It also has antispasmodic, antidiarrheal, vasodilatory, hypolipidemic, and antioxidant properties, as well as antifungal, antiviral, and antibacterial properties [130,131]. SKO is commonly used as a natural antioxidant and antimicrobial agent and as an antifungal agent in liquid culture media [132,133]. Nasiri et al. determined the effect of baicalin gum (TG) coatings containing different concentrations (100, 500, and 1000 ppm) of saturated SKO on the storage and preservation of A. bisporus mushrooms to maintain tissue hardness and sensory quality, reduce the number of microorganisms, and decrease the rate of decomposition of phenolic compounds and ascorbic acid to prolong their shelf life [91]. The results indicated that treatment with SKO containing TG (TGSEO) maintained 92.4% tissue hardness and reduced the number of microorganisms such as yeast, molds, and Pseudomonas compared to uncoated samples. In addition, the TGSKO-coated mushrooms showed a 57.1% reduction in the browning index (BI) and significantly higher total phenolic content (85.6%) and ascorbic acid accumulation (71.8%) than the control group, making it more efficient than the TG coating alone [91].

Antibacterial Mechanisms of EOs as Preservatives
The mechanism of action of EOs as preservatives for edible mushrooms is mainly due to their superior antibacterial mechanisms. Essential oils and EO slow-release systems release more ions and disperse them in the environment around the cell walls of pathogenic bacteria, where they effectively modify their pathogenicity. Direct interaction with the cell membrane produces metal ions and disrupts the cell membrane, disrupting the transmission signal to the cell membrane. At the same time, the electron transport chain is inhibited, which disrupts protein function within the bacterium and causes oxidative stress and DNA damage, resulting in the disruption of cell membrane formation [79,134] (Figure 3). In summary, the use of EOs to preserve edible mushrooms is widespread and has good preservation effects. However, the current research is still focused on the effects on preservation, and there is a lack of studies on the mechanisms of EOs as a preservative for different applications in the edible mushroom industry. First, although there have been studies on the microbial inhibition of EOs, the in vitro strains selected for inhibition are In summary, the use of EOs to preserve edible mushrooms is widespread and has good preservation effects. However, the current research is still focused on the effects on preservation, and there is a lack of studies on the mechanisms of EOs as a preservative for different applications in the edible mushroom industry. First, although there have been studies on the microbial inhibition of EOs, the in vitro strains selected for inhibition are still typically Gram-positive (S. aureus) and Gram-negative (E. coli), which may lack specificity. For example, it would be more meaningful to select Listeria monocytogenes, which has a relatively high rate of infestation of Flammulina velutiper and Pleurotus eryngii, for relevant mechanistic studies when conducting research on the inhibition effect and mechanism. Second, there is a lack of investigation of the mechanism of EOs from an energetic point of view. Whether the use of EOs changes the structure of mitochondria and modifies enzymes and related energetic substances in the respiratory chain still needs further investigation in terms of the respiratory effects of edible mushrooms.

Application of Plant Extracts in the Preservation of Edible Mushrooms
The main causes of edible mushroom decay and spoilage are oxidation reactions and bacterial growth [33,135]. The food industry has attempted to address these issues by incorporating additives into food products or implementing different packaging technologies. Packaging containing plant extracts is a popular direction for research to obtain biopolymeric food packaging. This is unique because it breaks down quickly into organic waste and can be easily infused with plant extracts, which results in active packaging with selective antibacterial and antioxidant food preservation effects that have positive implications for food storage and preservation [136]. According to numerous studies, plant extracts are promising alternatives to active food packaging due to their numerous properties, especially their ability to act as antioxidants and exert antibacterial activity [137,138] ( Table 2).     Optimal processing: Cd + MT-treated group Preservation effect: -Improve the activity of antioxidant enzymes: CAT activity 20,500 U/mg prot, SOD activity 1.75 U/mg prot, POD activity 2.8 U/mg prot, GR activity 0.014 U/mg prot, APX activity 0.18 U/mg prot at 5 days.
-Maintain high nutritional characteristics: Proline concentration 170 µg/g FW, total sugar concentration 9 mg/g FW at 5 days.
-The level of endogenous ROS was significantly reduced: H 2 O 2 content 175 pg/g FW, O 2 content 2.1 pg/g FW at 5 days. [143] Edible coatings are generally composed of polysaccharides, proteins, and lipids, which are generally derived from a variety of agricultural products and food processing wastes and by-products [38]. The polysaccharide coatings most commonly used are chitosan, pectin, carrageenan, gum, alginate, agar, and cellulose, and starch derivatives. Lecithin in lipids is mostly used as an emulsifier to dissolve oil-containing paints [144]. Edible coatings usually retard the shelf life of edible mushrooms by impeding gas exchange properties [145].

Application and Mechanism of Action of Plant Polysaccharides in the Preservation of Edible Mushrooms
Oudemansiella radicata polysaccharide (ORWP) is a natural polysaccharide extracted from the cysts of Oudemannia, a heteropolysaccharide with monosaccharides such as glucose, mannose, and galactose as the main components. Intriguingly, ORWP exhibits a wide range of actions, such as antifungal, antioxidant, and hepatoprotective activities [146,147]. Meanwhile, ORWP is a non-toxic and environmentally friendly compound tested as a coating agent for the preservation and shelf life extension of fresh flat mushrooms. Previous studies have found that it provides an effective barrier to the external environment, resulting in improved weight maintenance, delayed aging, and improved postharvest quality [146]. Liu et al. assessed the extent to which an ORWP coating improved the key quality characteristics of shiitake mushrooms during storage at 4 • C for 18 days and found that the use of the ORWP coating improved the retention of nutrients and flavor components, reduced MDA production, increased antioxidant enzyme activity, and improved the physical structure of shiitake mushrooms. Additionally, the ORWP coating was found to retard the softening of the mushroom due to the inhibition of cell wall hydrolases and, thus, the degradation of cellulose and chitin [142]. Shiitake mushroom polysaccharide (LEP) is a natural polysaccharide extracted from the stem of the shiitake mushroom and consists mainly of glucose [148], and it shows a wide range of actions, such as antioxidant and hypoglycemic effects [149]. It improved the weight retention, delayed the decay, and improved the postharvest quality of shiitake mushrooms by providing an effective external environmental barrier. Guo et al. investigated the effect of a polysaccharide coating on the browning and softening of shiitake mushrooms by showing that LEP increased the activities of POD, CAT, SOD, APX, and PAL and significantly reduced the accumulation of hydrogen peroxide compared to the control [148]. In addition, during storage, LEP treatment maintained the high antioxidant activity of the mushroom and inhibited the activity of browning-related enzymes (polyphenol oxidase and tyrosinase) to reduce browning. Furthermore, it maintained high levels of cellulase, chitinase, and β-1,3 glucanase to improve softening during storage [148]. The mechanism of action of plant polysaccharides in the preservation of edible mushrooms is illustrated in Figure 4.

Application and Mechanism of Action of Melatonin in the Preservation of Edible Mushrooms
Melatonin (N-acetyl-5-methoxytryptamine; MT) is a pleiotropic molecule commonly found in nature [150]. It plays a multifaceted role not only in humans and animals but also in the growth and development of plants [151]. In plants and bacteria, the best-known function of MT is associated with ameliorating abiotic stresses caused by various factors such as drought, radiation, extreme temperatures, and chemical stress, all of which have been reported to promote the production of ROS [152]. Many studies have shown that MT exhibits important defensive effects against various abiotic stresses in plants and animals [153,154]. Melatonin can mediate selenium-induced tolerance to Cd stress in tomatoes via Cd detoxification and can ameliorate water deficit stress in grapes through antioxidant metabolites [154,155]. Li et al. investigated the effect of MT in delaying aging by regulating electron leakage in postharvest A. bisporus and found that 0.1 mM MT treatment increased the antioxidant system and significantly inhibited electron leakage. Furthermore, MT had a clear and beneficial effect in maintaining higher ATP, cytochrome c oxidase (Cyt C), and energy levels, increasing the oxidative phosphorylation and efficiency of mitochondria, and delaying the senescence process in postharvest white mushrooms [49]. In contrast, Gao et al. focused on enhancing the tolerance of mushrooms to Cd through antioxidant-related metabolites and enzymes to verify the ameliorative effect of MT on Cd-induced oxidative stress. MT can promote the antioxidant activity of Volvariella volvacea via amino acid metabolism, glutathione metabolism, redox processes, detoxification, and cellular oxidant detoxification, suggesting that exogenous MT has a protective effect on Cd-induced oxidative stress in edible mushrooms [143]. Thus, MT contains several active compounds that have a selective effect on the autoxidation and antibacterial pathways in the preservation of edible mushrooms, making it a good choice for the storage and preservation of edible mushrooms [154]. The application and mechanism of action of MT in the preservation of edible mushrooms are shown in Figure 5. tion, delayed the decay, and improved the postharvest quality of shiitake mushrooms by providing an effective external environmental barrier. Guo et al. investigated the effect of a polysaccharide coating on the browning and softening of shiitake mushrooms by showing that LEP increased the activities of POD, CAT, SOD, APX, and PAL and significantly reduced the accumulation of hydrogen peroxide compared to the control [148]. In addition, during storage, LEP treatment maintained the high antioxidant activity of the mushroom and inhibited the activity of browning-related enzymes (polyphenol oxidase and tyrosinase) to reduce browning. Furthermore, it maintained high levels of cellulase, chitinase, and β-1,3 glucanase to improve softening during storage [148]. The mechanism of action of plant polysaccharides in the preservation of edible mushrooms is illustrated in Figure 4.

Application and Mechanism of Action of Melatonin in the Preservation of Edible Mushrooms
Melatonin (N-acetyl-5-methoxytryptamine; MT) is a pleiotropic molecule commonly found in nature [150]. It plays a multifaceted role not only in humans and animals but also in the growth and development of plants [151]. In plants and bacteria, the best-known function of MT is associated with ameliorating abiotic stresses caused by various factors such as drought, radiation, extreme temperatures, and chemical stress, all of which have been reported to promote the production of ROS [152]. Many studies have shown that MT exhibits important defensive effects against various abiotic stresses in plants and animals [153,154]. Melatonin can mediate selenium-induced tolerance to Cd stress in tomatoes via Cd detoxification and can ameliorate water deficit stress in grapes through antioxidant

Application and Mechanism of Action of Exogenous Energy Substances in the Preservation of Edible Mushrooms
Exogenous adenosine triphosphate (ATP) treatment has been used as an innovative method to improve stress, delay senescence, and preserve quality in horticultural crops during postharvest storage [156]. It may be an effective way to reduce electrolyte leakage and MDA accumulation, protect membrane integrity, and facilitate delayed aging. A study by Aghdam et al. demonstrated reduced browning and preservation of quality, increased phenol accumulation, and improved ability to scavenge ·DPPH in ATP-treated shiitake mushrooms. In addition to having higher endogenous phenol and MT accumulation, they showed a lower H 2 O 2 accumulation capacity and could scavenge ROS [140]. The application and mechanism of action of exogenous energy substances in the preservation of edible mushrooms are presented in Figure 6. acid metabolism, glutathione metabolism, redox processes, detoxification, and cellular oxidant detoxification, suggesting that exogenous MT has a protective effect on Cd-induced oxidative stress in edible mushrooms [143]. Thus, MT contains several active compounds that have a selective effect on the autoxidation and antibacterial pathways in the preservation of edible mushrooms, making it a good choice for the storage and preservation of edible mushrooms [154]. The application and mechanism of action of MT in the preservation of edible mushrooms are shown in Figure 5.

Application and Mechanism of Action of Exogenous Energy Substances in the Preservation of Edible Mushrooms
Exogenous adenosine triphosphate (ATP) treatment has been used as an innovative method to improve stress, delay senescence, and preserve quality in horticultural crops during postharvest storage [156]. It may be an effective way to reduce electrolyte leakage and MDA accumulation, protect membrane integrity, and facilitate delayed aging. A study by Aghdam et al. demonstrated reduced browning and preservation of quality, increased phenol accumulation, and improved ability to scavenge ·DPPH in ATP-treated shiitake mushrooms. In addition to having higher endogenous phenol and MT  accumulation, they showed a lower H2O2 accumulation capacity and could scavenge ROS [140]. The application and mechanism of action of exogenous energy substances in the preservation of edible mushrooms are presented in Figure 6. Gamma-aminobutyric acid (GABA) is a neuroactive inhibitory neurotransmitter molecule with beneficial effects on human health [157,158]. Therefore, GABA has received considerable attention from the food and pharmaceutical industries as a safe and environ-

Application of Other Plant Extracts in the Preservation of Edible Mushrooms
Gamma-aminobutyric acid (GABA) is a neuroactive inhibitory neurotransmitter molecule with beneficial effects on human health [157,158]. Therefore, GABA has received considerable attention from the food and pharmaceutical industries as a safe and environmentally friendly functional bioactive molecule for health promotion, and, as a result, GABA-enriched foods have been commercialized worldwide [159]. GABA is an endogenous signaling molecule that plays an important role in plant growth, pH regulation, nitrogen storage, osmoregulation, ROS scavenging, and defense against abiotic and biotic stresses [160,161]. GABA biosynthesis occurs mainly in the GABA shunt pathway. Glutamic acid decarboxylase (GAD), GABA transaminase (GABA-T), and succinic semialdehyde dehydrogenase (SSADH) are involved in GABA metabolism [162]. It was demonstrated that exogenous GABA increased GAD gene expression, thereby increasing glutamate production from endogenous GABA, improving the antioxidant capacity of mushrooms, and reducing oxidative stress damage in edible mushrooms during storage. The results from the study of Shekari et al. revealed that GABA-treated mushrooms had lower rates of browning and weight loss and maintained their hardness better than untreated mushrooms [139]. GABA treatment maintained membrane integrity and reduced membrane lipid peroxidation. Treated mushrooms exhibited lower electrolyte leakage rates and MDA content. ASA content was higher in GABA-treated mushrooms, while ROS and H 2 O 2 content were lower than in the untreated group. The higher accumulation of total phenolics in the treated mushrooms increased their antioxidant capacity. The treated mushroom strains showed higher PAL activity and gene expression and lower PPO activity [139].
In addition to the above investigations, agricultural waste extracts have also been studied for their application in preserving edible mushrooms. Pistachio shells (PGH) are a cheap and abundant natural source of useful compounds (>104.0 × 10 6 kg) from agricultural waste, and pistachio shells make up 35-45% of the whole fruit [163]. The high phenolic and antioxidant capacity of PGH suggests that it may be a cost-effective source of bioactive compounds with health-protective potential [164][165][166][167]. Its main components are anaerobic acid (31.98 g kg −1 ), fatty acids (15.00 g kg −1 ), and phytosterols (19.20 g kg −1 ). The main phenolic compounds of pistachio green shell (Pistacia vera L., variety Bronte) are gallic acid, 4-hydroxybenzoic acid, protocatechuic acid, naringin, eriodictyol-7-O-glucoside, isorhamnetin 7-O-glucoside, quercetin-3-O-rutinoside, isorhamnetin 3-O-glucoside, and catechins [163]. Fattahifar et al., investigated the inhibitory activity of pistachio husk extract (PGHE) on mushroom tyrosinase and showed that PGHE-treated mushrooms had a lower BI than other samples. Pistachio green hull extract (PGHE) maintained the hardness (13.9% higher than the control) and whiteness of the mushrooms. It kept the organoleptic properties of the mushrooms within an acceptable range throughout storage and they had higher phenolic content (14.4%) and antioxidant activity (4.5%) than the control samples at the end of storage [141]. Pistachio shell extract is a novel natural tyrosinase inhibitor for reducing browning and related enzymatic browning reactions in edible mushrooms, while its cost advantage can distinguish it among the wide range of food preservation methods.

Perspectives and Conclusions
Research related to the preservation of mushrooms by EOs and plant extracts in recent years has shown that, although effective in preserving some of the key quality attributes of edible mushrooms, these preservation techniques have their drawbacks. For example, some essential oil treatments can significantly extend the shelf life of mushrooms; however, they lead to texture changes and discoloration, which affects customer acceptance. The use of nanoparticles for the controlled release of EOs in mushrooms maintains their quality during storage and extends their shelf life but adds additional costs in terms of packaging. This suggests that the area involving the use of EOs and plant extracts for preserving mushrooms still needs to be developed. In the future, it is important to further investigate the mechanisms of quality fission during storage and preservation, such as browning, softening, and lignification, through multi-omics techniques, and to study the potential molecular mechanisms of gene regulation during preservation, so that the problem of the postharvest quality deterioration of edible mushrooms can be addressed at the molecular level. In addition, a combination of new and traditional technologies can be used to improve the postharvest quality of edible mushrooms, combining various technologies at a lower capital cost or shorter processing time to further enhance the postharvest quality of mushrooms.

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.