An ultrasonic pretreatment synergistic polyphenol-essential oil balanced compound tea tree mushroom preservation method

Abstract

The application provides a tea tree mushroom preservation method through ultrasonic pretreatment and balanced compounding of polyphenols and essential oils, and relates to the technical field of edible mushroom preservation. The method first performs ultrasonic pretreatment on the tea tree mushroom, realizes enzyme passivation, assists sterilization and forms micropore structures on the epidermis by using cavitation effect; then immerses the tea tree mushroom in a preservation liquid compounded by polyphenols and plant essential oils for 0.5-2 minutes; and finally stores the tea tree mushroom in a vacuum package at 0-4 DEG C. Through deep cooperation of ultrasonic pretreatment and low-dose natural compounding liquid, the application significantly enhances the penetration efficiency and action durability of active ingredients, prolongs the tea tree mushroom preservation period to 28-32 days, and reduces the active ingredient dosage and process cost. The method is process standard, green and safe, and cost controllable, and is suitable for standardized preservation production of tea tree mushrooms.

Description

Technical Field

[0001] This invention relates to the field of edible fungi preservation technology, and in particular to a method for preserving tea tree mushrooms using ultrasonic pretreatment and a balanced compound of polyphenols and essential oils. Background Technology

[0002] Tea tree mushrooms enjoy high market acceptance and strong consumer demand due to their rich protein, polysaccharide, and essential amino acid content, as well as their unique crisp and tender texture and mushroom aroma. However, tea tree mushrooms have extremely vigorous respiration and transpiration after harvesting. Coupled with their high tissue water content and fragile epidermis, they are prone to multiple quality deteriorations during post-harvest storage and transportation, including: enzymatic browning leading to a darker color; wilting and weight loss due to moisture loss; microbial infection (mainly bacteria and molds) leading to spoilage; and physiological aging phenomena such as cap opening and softening. The synergistic effect of these problems means that the commercial shelf life of tea tree mushrooms under conventional low-temperature storage conditions (0-4℃) is usually less than one week, with a post-harvest loss rate as high as 20%-30%, which seriously restricts the healthy development of the tea tree mushroom industry.

[0003] To extend the shelf life of edible fungi, existing technologies have tried various methods, but all have limitations to varying degrees: (1) Chemical preservative treatment: such as sulfites, benzimidazoles, etc., although they can effectively inhibit browning and microbial growth, there is a risk of chemical residues, which does not conform to the current consumption trend of "green, safe and natural", and long-term use may induce microbial resistance, while easily destroying the natural flavor of edible fungi and reducing the commodity value; (2) Low temperature storage: although it can slow down the metabolic rate to a certain extent, it cannot completely inhibit the activity of endogenous enzymes and the reproduction of microorganisms. When used alone, the preservation effect is limited, and long-term low temperature storage is energy-intensive and costly. (3) Single natural preservative treatment: such as tea polyphenols, chitosan, plant essential oils, etc. However, polyphenols have limited water solubility, plant essential oils are highly hydrophobic and volatile, resulting in poor dispersibility in aqueous systems. Furthermore, the dense epidermis of edible fungi forms a wetting barrier, leading to poor permeability and uneven adhesion of active ingredients. Large dosages result in poor batch stability and significant fluctuations in effects. (4) Physical preservation techniques: Physical methods such as ultrasound, ultraviolet light, and plasma have attracted attention due to their "additive-free" characteristics. Among them, ultrasound produces enzyme passivation and sterilization through cavitation effect, but existing applications have significant shortcomings: parameters lack standardization, and the frequency, power, and time vary greatly in different studies, leading to unstable effects; material stacking causes uneven ultrasound penetration; if heat accumulation during cavitation is not controlled, it will accelerate metabolism; and when used alone, the enzyme passivation effect is not lasting.

[0004] Therefore, there is an urgent need to provide a solution to improve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preserving tea tree mushrooms by synergistic ultrasonic pretreatment and polyphenol-essential oil balanced compounding.

[0006] In a first aspect, the present invention provides a method for preserving *Agrocybe aegerita* mushrooms using ultrasonic pretreatment and a balanced blend of polyphenols and essential oils, comprising the following steps:

[0007] (1) Raw material pretreatment: Select fresh, undamaged tea tree mushrooms, remove impurities from the roots, rinse quickly with sterile water 2-3 times, and drain.

[0008] (2) Ultrasonic pretreatment: The tea tree mushrooms obtained in step (1) are laid flat on the hollowed-out rack of the ultrasonic treatment tank, and sterile water is added to immerse them for ultrasonic pretreatment. After treatment, they are taken out and drained.

[0009] (3) Preparation of compound preservative solution: Polyphenols and plant essential oils are compounded in a buffer system to obtain compound preservative solution; the compound preservative solution contains antioxidants;

[0010] (4) Treatment with compound preservative solution: Immerse the tea tree mushrooms obtained by ultrasonic pretreatment in step (2) into the compound preservative solution prepared in step (3) for 0.5-2 minutes;

[0011] (5) Post-processing and storage: The tea tree mushrooms obtained by the compound preservative solution in step (4) are drained, vacuum-packed and stored at 0-4℃.

[0012] Optionally, the thickness of the flat layer in step (2) is ≤2cm; the aperture of the hollowed-out shelf is 0.5-1cm.

[0013] Optionally, the ultrasonic pretreatment in step (2) has a frequency of 20-40kHz, a power of 150-250W, a treatment time of 20-60s, and the temperature of the sterile water is controlled to be ≤25℃ during the treatment.

[0014] Optionally, the mass concentration of the polyphenolic substances in step (3) is 0.04%-0.16%; and the mass concentration of the plant essential oil is 0.012%-0.02%.

[0015] Optionally, the polyphenolic substances in step (3) include tea polyphenols and rosemary polyphenols; the mass ratio of tea polyphenols to rosemary polyphenols is (1.2:1)-(1.8:1); the plant essential oil is lemongrass essential oil.

[0016] Optionally, the buffer system described in step (3) is a citrate-sodium citrate buffer solution with a pH of 5.5-6.5.

[0017] Optionally, the compound preservative solution also contains 1%-5% ethanol by volume as a co-solvent.

[0018] Optionally, the antioxidant in step (3) is vitamin C, and the amount added is 0.01%-0.03% of the total mass of the compound preservative solution.

[0019] Optionally, the draining time in step (5) is 5-8 minutes.

[0020] Optionally, the vacuum packaging uses polyethylene preservation bags and is then vacuumed to a vacuum level of 0.06-0.08 MPa.

[0021] Secondly, the present invention provides a tea tree mushroom preservation product prepared by any of the above-mentioned optional methods.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The preservation method provided by the present invention, through the synergistic effect of standardized ultrasonic pretreatment and polyphenol-essential oil balanced compound solution, enables the ultrasonic cavitation effect to form microporous channels on the surface of tea tree mushroom, significantly enhancing the permeability and adhesion uniformity of the active ingredients in the compound solution, achieving a synergistic preservation effect of "1+1>2", extending the preservation period of tea tree mushroom at 0-4℃ from about 8 days in the traditional method to 28-32 days;

[0024] (2) The preservation method provided by the present invention solves the problems of arbitrary parameters, uneven processing and heat accumulation damage caused by material stacking in traditional ultrasonic treatment by precisely limiting ultrasonic parameters (frequency 20-40kHz, power 200W, time 30s, water temperature ≤25℃) and combining it with the hollowed-out rack to lay the material flat. It achieves precise control of enzyme passivation, auxiliary sterilization and micropore generation, ensuring the stability of the treatment effect and batch consistency, and is suitable for standardized industrial production.

[0025] (3) The preservation method provided by the present invention combines tea polyphenols and rosemary polyphenols at a mass ratio of 1.5:1, utilizes the complementary characteristics of their antioxidant spectrum (tea polyphenols strongly inhibit PPO, and rosemary polyphenols have strong thermal stability and long-lasting effect), and combines the broad-spectrum antibacterial properties of lemongrass essential oil with the synergistic antioxidant effect of vitamin C, forming a balanced protection system of "antibacterial-antioxidant-color protection-flavor", which overcomes the defect of single natural preservatives having a single effect;

[0026] (4) The preservation method provided by the present invention significantly enhances the penetration efficiency of the compound solution due to ultrasonic pretreatment, thereby greatly reducing the concentration of tea polyphenols, rosemary polyphenols and lemongrass essential oil required to achieve the same or even better preservation effect. At the same time, the use of 3% low-concentration ethanol to replace the complex emulsification process significantly saves the cost of natural extract raw materials and process equipment. Moreover, the compound preservation solution is composed entirely of natural edible ingredients (tea polyphenols, rosemary polyphenols, lemongrass essential oil, vitamin C, citric acid-sodium citrate buffer and trace amounts of ethanol), with no risk of chemical residues, is environmentally friendly, and conforms to the development direction of green preservation technology.

[0027] (5) The preservation method provided by this invention results in a weight loss rate of ≤3.3%, browning degree ≤0.35, and total bacterial count ≤6.8×10⁻⁶ for tea tree mushrooms after 25 days of storage. 3 CFU / g can effectively maintain the bright color, crisp texture and inherent aroma of tea tree mushrooms, overcoming the problems of browning, wilting and flavor deterioration of tea tree mushrooms in traditional preservation methods, and maintaining high commercial value in the later stages of storage. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0029] This invention provides a method for preserving *Agrocybe aegerita* mushrooms using ultrasonic pretreatment and a balanced blend of polyphenols and essential oils, comprising the following steps:

[0030] (1) Raw material pretreatment: Select fresh, undamaged tea tree mushrooms, remove impurities from the roots, rinse quickly with sterile water 2-3 times, and drain.

[0031] (2) Ultrasonic pretreatment: The tea tree mushrooms obtained in step (1) are laid flat on the hollowed-out rack of the ultrasonic treatment tank, and sterile water is added to immerse them for ultrasonic pretreatment. After treatment, they are taken out and drained.

[0032] (3) Preparation of compound preservative solution: Polyphenols and plant essential oils are compounded in a buffer system to obtain compound preservative solution; the compound preservative solution contains antioxidants;

[0033] (4) Treatment with compound preservative solution: Immerse the tea tree mushrooms obtained by ultrasonic pretreatment in step (2) into the compound preservative solution prepared in step (3) for 0.5-2 minutes;

[0034] (5) Post-processing and storage: The tea tree mushrooms obtained by the compound preservative solution in step (4) are drained, vacuum-packed and stored at 0-4℃.

[0035] In fact, this invention first performs standardized ultrasonic pretreatment on *Agrocybe aegerita* (tea tree mushroom). Through precisely controlled parameters combined with a perforated rack for flat placement, uniform enzyme inactivation, assisted sterilization, and the formation of a microporous structure are achieved. Subsequently, the mushrooms are immersed in a preservative solution composed of polyphenols and plant essential oils. After treatment, the mushrooms are drained, vacuum-packed, and stored at 0-4°C. This invention, through the synergistic effect of ultrasonic pretreatment and the naturally compounded preservative solution, achieves comprehensive regulation of enzyme activity, microorganisms, moisture content, and color in *Agrocybe aegerita*, significantly extending the shelf life to 28-32 days. Simultaneously, due to the reduced concentration of active ingredients in the compound preservative solution and the short ultrasonic treatment time and low energy consumption, the overall cost of this method is significantly reduced.

[0036] In fact, selecting high-quality raw materials in step (1) can reduce the initial microbial load, sterile water rinsing avoids the introduction of contaminants, and rapid rinsing and draining prevent the tea tree mushroom from absorbing too much water and causing tissue softening, laying the foundation for subsequent ultrasonic pretreatment and preservation liquid treatment.

[0037] In some embodiments, in step (2), the tea tree mushrooms obtained from the pretreatment in step (1) are laid flat on the hollowed-out rack of the ultrasonic treatment tank, with a thickness of ≤2cm; the hole diameter of the hollowed-out rack is 0.5-1cm.

[0038] In fact, using a hollowed-out rack to lay the tea tree mushrooms flat, with a hole diameter of 0.5-1cm, can ensure that the ultrasonic waves can penetrate without obstruction, avoiding the problem of insufficient treatment in some areas caused by the stacking of tea tree mushrooms; the flat laying thickness of ≤2cm ensures that each tea tree mushroom can receive ultrasonic treatment evenly, solving the problem of uneven effect caused by material stacking in traditional ultrasonic treatment.

[0039] In some embodiments, the frequency of ultrasonic pretreatment in step (2) is 20-40kHz, the power is 150-250W, the treatment time is 20-60s, and the temperature of sterile water is controlled to be ≤25℃ during the treatment.

[0040] Specifically, the optimal standardized design for ultrasonic pretreatment parameters is: ultrasonic frequency 20-40kHz, power 200W, and time 30s. In practice, this parameter range can create a stable cavitation effect, ensuring treatment effectiveness while avoiding excessive damage. Below 20kHz, the cavitation effect is weak, resulting in insufficient enzyme inactivation and sterilization; above 40kHz, the cavitation bubble volume is too small, and the shock wave intensity is insufficient to destroy enzyme structures and microbial cell membranes; power exceeding 200W or time exceeding 30s can lead to cell rupture in *Agrocybe aegerita*, accelerating moisture loss and browning.

[0041] Specifically, during the ultrasonic pretreatment process, the water temperature is controlled at 20-25℃ using a constant temperature circulation device. This avoids the accumulation of instantaneous high temperatures caused by ultrasonic cavitation, preventing heat damage to the *Agrocybe aegerita* (tea tree mushroom) tissue. It also prevents the cavitation effect from being reduced by low temperatures (<20℃), ensuring stable enzyme inactivation and sterilization effects. After ultrasonic pretreatment, the *Agrocybe aegerita* mushrooms are quickly removed and drained of surface moisture. The draining time is ≤2 minutes to prevent excessive moisture from affecting the subsequent soaking effect of the compound solution.

[0042] In fact, the ultrasonic pretreatment has multiple synergistic effects: Enzyme passivation: The instantaneous high pressure (hundreds of atmospheres) and high temperature (thousands of K) generated by the cavitation effect can destroy the spatial structure of polyphenol oxidase (PPO) and peroxidase (POD), leading to the inactivation of the enzyme active center. At the same time, it inhibits the activity of key enzymes in the respiratory chain (succinate dehydrogenase, cytochrome c oxidase), directly inhibiting browning and respiration; Enhanced penetration: The microjets and shock waves accompanying the cavitation effect will form tiny pores on the surface of the tea tree mushroom. These pores can serve as penetration channels for active ingredients (polyphenols, essential oils) in the compound preservative solution, significantly improving the adhesion and penetration depth of the ingredients, allowing the active ingredients to quickly reach the cells and exert their effects; Assisted sterilization: The mechanical force generated by the rupture of cavitation bubbles can directly destroy the cell membranes of surface microorganisms (molds, putrefactive bacteria), leading to microbial death, reducing the initial microbial load, and reducing the risk of spoilage during subsequent storage; Surface cleaning: The microjets can remove residual impurities and some microbial biofilms on the surface of the tea tree mushroom, further reducing the risk of contamination, while making the surface smoother, which is conducive to the uniform adhesion of the compound solution.

[0043] In some embodiments, the mass concentration of the polyphenols used in step (3) is 0.04%-0.16%; the mass concentration of the plant essential oils used is 0.012%-0.02%.

[0044] In some embodiments, the polyphenols used in step (3) include tea polyphenols and rosemary polyphenols; the mass ratio of tea polyphenols to rosemary polyphenols is (1.2:1)-(1.8:1); and the plant essential oil used is lemongrass essential oil.

[0045] In some embodiments, the buffer system used in step (3) is a citrate-sodium citrate buffer solution with a pH of 5.5-6.5.

[0046] In some embodiments, the prepared compound preservative solution also contains 1%-5% ethanol by volume as a co-solvent.

[0047] In some embodiments, the antioxidant used in step (3) is vitamin C, and the amount added is 0.01%-0.03% of the total mass of the compound preservative solution.

[0048] Specifically, tea polyphenols and rosemary polyphenols are preferably mixed at a mass ratio of 1.5:1, and lemongrass essential oil dissolved in ethanol is dispersed together in a citrate-sodium citrate buffer solution with a pH of 5.5-6.5 (ethanol to buffer volume ratio of 3%). After stirring evenly, a compound preservation solution is obtained, wherein the total mass concentration of tea polyphenols and rosemary polyphenols is 0.04%-0.16%, the mass concentration of lemongrass essential oil is 0.012%-0.02%, and 0.01%-0.03% vitamin C is added to the buffer solution.

[0049] In fact, the prepared compound preservative solution contains a combination of two polyphenols: tea polyphenols effectively inhibit polyphenol oxidase, and rosemary polyphenols have strong thermal stability and long-lasting antioxidant effects, which synergistically enhance the color-protecting effect; lemongrass essential oil: containing citral and other components, it has both broad-spectrum antibacterial properties and a natural fragrance, which synergistically enhance the preservative effect and optimize the flavor with polyphenols; ethanol as a solubilizer: the low concentration of 3% ethanol ensures that the essential oil is evenly dispersed, and there is no risk of harmful chemical residues, making it highly safe for consumption; a buffer system: maintaining pH stability, providing a suitable environment for the active ingredients to exert their effects, and the chelating effect of citric acid helps inhibit oxidation; vitamin C: synergistically with polyphenols and essential oils to resist oxidation, prevent the active ingredients from oxidizing themselves, and extend the shelf life of the preservative solution.

[0050] Specifically, in step (4), when treating the tea tree mushrooms obtained by ultrasonic pretreatment with the compound preservative solution, soak them for 1 minute, or spray the emulsion evenly onto the surface of the mushrooms using a spraying method. In fact, the porous structure formed by ultrasonic pretreatment allows the compound solution to penetrate quickly and adhere evenly, achieving the effect of high concentration and long soaking time in the traditional method in just 1 minute, thus avoiding the softening of the tea tree mushrooms by absorbing water.

[0051] In some embodiments, the draining time in step (5) is 5-8 minutes.

[0052] In fact, ventilating and draining removes excess preservative solution from the surface, reducing the growth of microorganisms.

[0053] In some embodiments, vacuum packaging involves packaging in polyethylene food storage bags and then evacuating them to a vacuum level of 0.06-0.08 MPa.

[0054] In fact, the barrier properties of polyethylene food storage bags reduce moisture loss, vacuum packaging lowers oxygen concentration and inhibits respiration, and the low-temperature environment further slows down metabolism and microbial reproduction, forming a comprehensive preservation system in synergy with ultrasonic-compound liquid.

[0055] Secondly, the present invention also provides a tea tree mushroom preservation product prepared using any of the above embodiments.

[0056] Example 1

[0057] This embodiment 1 provides a method for preserving tea tree mushrooms using ultrasonic pretreatment and a balanced blend of polyphenols and essential oils, including the following steps:

[0058] (1) Raw material pretreatment: Select fresh, undamaged tea tree mushrooms, remove impurities, rinse twice with sterile water, and drain.

[0059] (2) Ultrasonic pretreatment: The tea tree mushrooms obtained in step (1) are laid flat in a single layer on a carrier with a hole diameter of 0.8cm and a thickness of 1.5cm. Sterile water is added to immerse the mushrooms, and ultrasonic pretreatment is carried out at 30kHz and 200W for 30s with a water temperature of 22℃. After treatment, the mushrooms are taken out and drained for 1min.

[0060] (3) Preparation of compound preservative solution: Tea polyphenols and rosemary polyphenols were mixed at a mass ratio of 1.5:1 (total concentration of tea polyphenols and rosemary polyphenols was 0.064%), and lemongrass essential oil (0.016%) was dissolved in 3% ethanol and added. The mixture was then dispersed in a pH 6.0 citric acid-sodium citrate buffer solution containing 0.02% vitamin C to obtain the compound preservative solution.

[0061] (4) Treatment with compound preservative solution: Immerse the tea tree mushrooms obtained by ultrasonic pretreatment in step (2) into the compound preservative solution prepared in step (3) for 1 minute;

[0062] (5) Post-processing and storage: The tea tree mushrooms obtained by the compound preservation solution in step (4) are ventilated and drained for 6 minutes, then packed into polyethylene (PE) preservation bags (250g), vacuumed to 0.07MPa, and stored at 2℃.

[0063] Example 2

[0064] This embodiment 2 provides a method for preserving tea tree mushrooms using ultrasonic pretreatment and a balanced blend of polyphenols and essential oils, including the following steps:

[0065] (1) Raw material pretreatment: Select fresh, undamaged tea tree mushrooms, remove impurities, rinse twice with sterile water, and drain.

[0066] (2) Ultrasonic pretreatment: The tea tree mushrooms obtained in step (1) are laid flat in a single layer on a carrier with a hole diameter of 0.8cm and a thickness of 1.5cm. Sterile water is added to immerse the mushrooms, and ultrasonic pretreatment is carried out at 20kHz and 200W for 30s with a water temperature of 20℃. After treatment, the mushrooms are taken out and drained for 1min.

[0067] (3) Preparation of compound preservative solution: Tea polyphenols and rosemary polyphenols were mixed at a mass ratio of 1.5:1 (total concentration of tea polyphenols and rosemary polyphenols was 0.04%), and lemongrass essential oil (0.012%) was dissolved in 3% ethanol and added. The mixture was then dispersed in a pH 6.0 citric acid-sodium citrate buffer solution containing 0.01% vitamin C to obtain the compound preservative solution.

[0068] (4) Treatment with compound preservative solution: Immerse the tea tree mushrooms obtained by ultrasonic pretreatment in step (2) into the compound preservative solution prepared in step (3) for 1 minute;

[0069] (5) Post-processing and storage: The tea tree mushrooms obtained by the compound preservation solution in step (4) are ventilated and drained for 5 minutes, then packed into a polyethylene (PE) preservation bag (250g), vacuumed to 0.06MPa, and stored at 0℃.

[0070] Example 3

[0071] This embodiment 3 provides a method for preserving tea tree mushrooms using ultrasonic pretreatment and a balanced blend of polyphenols and essential oils, including the following steps:

[0072] (1) Raw material pretreatment: Select fresh, undamaged tea tree mushrooms, remove impurities, rinse twice with sterile water, and drain.

[0073] (2) Ultrasonic pretreatment: The tea tree mushrooms obtained in step (1) are laid in a single layer on a carrier with a hole diameter of 0.8cm and a thickness of 1.5cm. Sterile water is added to immerse the mushrooms and ultrasonic pretreatment is performed at 40kHz and 200W for 30s at a water temperature of 25℃. After treatment, the mushrooms are taken out and drained for 1min.

[0074] (3) Preparation of compound preservative solution: Tea polyphenols and rosemary polyphenols were mixed at a mass ratio of 1.5:1 (total concentration of tea polyphenols and rosemary polyphenols was 0.16%), and lemongrass essential oil (0.02%) was dissolved in 3% ethanol and added. The mixture was then dispersed in a pH 6.0 citric acid-sodium citrate buffer solution containing 0.03% vitamin C to obtain the compound preservative solution.

[0075] (4) Treatment with compound preservative solution: Immerse the tea tree mushrooms obtained by ultrasonic pretreatment in step (2) into the compound preservative solution prepared in step (3) for 1 minute;

[0076] (5) Post-processing and storage: The tea tree mushrooms obtained by the compound preservation solution in step (4) are ventilated and drained for 8 minutes, then packed into a polyethylene (PE) preservation bag (250g), vacuumed to 0.08MPa, and stored at 4℃.

[0077] Comparative Experiment: To verify the preservation effect of the synergistic solution of the present invention, the following comparative examples were set up:

[0078] Comparative Example 1: Tea tree mushrooms were preserved using traditional low-temperature storage. The difference from Example 1 is that steps (2), (3) and (4) were not performed, while other conditions were the same as in Example 1.

[0079] Comparative Example 2: Ultrasonic pretreatment only, without compound solution treatment. The difference from Example 1 is that steps (3) and (4) are not performed, and other conditions are the same as in Example 1.

[0080] Comparative Example 3: No ultrasonic pretreatment was used; only the compound solution was used. The difference from Example 1 is that step (2) was not performed, and in step (3), when preparing the compound preservative solution, the concentration of the compound solution was 1.25 times that of Example 1 (0.08% polyphenols and 0.02% essential oils), and other conditions were the same as in Example 1.

[0081] Comparative Example 4: The difference from Example 1 is that in step (2), the ultrasound parameters exceeded the standard (power 300W, time 60s), while other conditions were the same as in Example 1.

[0082] Comparative Example 5: The difference from Example 1 is that in step (3), a compound preservative solution was prepared by combining tea polyphenols and rosemary polyphenols (without essential oils), and other conditions were the same as in Example 1.

[0083] Comparative Example 6: The difference from Example 1 is that in step (2) during ultrasonic pretreatment: the tea tree mushrooms obtained from step (1) are laid flat in a single layer on a carrier with a hole diameter of 0.8cm and a thickness of 5cm. Other conditions are the same as in Example 1.

[0084] Comparative Example 7: The difference from Example 1 is that the water temperature was not controlled during the ultrasonic pretreatment in step (2) (it was naturally heated to 35°C), and the other conditions were the same as in Example 1.

[0085] Storage tests were conducted on the *Agrocybe aegerita* mushrooms of Examples 1-3 and Comparative Examples 1-7, respectively. Sensory quality, weight loss, browning degree, and total colony count were tested periodically. The results are shown in Table 1 below:

[0086] Table 1: Results of the comparative experiment on the quality of *Tea Tree Mushroom* during storage period in Examples 1-3 and Comparative Examples 1-7

[0087]

[0088] As shown in Table 1 above, the preservation effect of Examples 1-3 of the present invention is significantly better than that of the comparative examples: Example 1 has a preservation period of 32 days, which is 24 days longer than traditional low-temperature storage, 17 days longer than single ultrasonic treatment, and 7 days longer than high-concentration compound treatment without ultrasonic treatment; after 25 days of storage, the weight loss rate is ≤3.3%, the browning degree is ≤0.35, and the total bacterial count is ≤6.8×10⁻⁶. 3 CFU / g, sensory quality remains good;

[0089] Comparative Example 4 resulted in cell rupture and a soft, mushy texture due to excessive ultrasound parameters; Comparative Example 5 lacked essential oil components, resulting in insufficient antibacterial effect; Comparative Example 6 suffered from uneven ultrasound treatment due to stacked tea tree mushrooms, leading to severe browning in some areas; and Comparative Example 7 experienced a shortened shelf life due to excessively high water temperature, which accelerated the metabolism of tea tree mushrooms.

[0090] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for preserving *Agrocybe aegerita* mushrooms using ultrasonic pretreatment and a balanced blend of polyphenols and essential oils, characterized in that... Includes the following steps: (1) Raw material pretreatment: Select fresh, undamaged tea tree mushrooms, remove impurities from the roots, rinse quickly with sterile water 2-3 times, and drain. (2) Ultrasonic pretreatment: The tea tree mushrooms obtained in step (1) are laid flat on the hollowed-out rack of the ultrasonic treatment tank, and sterile water is added to immerse them for ultrasonic pretreatment. After treatment, they are taken out and drained. (3) Preparation of compound preservative solution: Polyphenols and plant essential oils are compounded in a buffer system to obtain compound preservative solution; the compound preservative solution contains antioxidants; (4) Treatment with compound preservative solution: Immerse the tea tree mushrooms obtained by ultrasonic pretreatment in step (2) into the compound preservative solution prepared in step (3) for 0.5-2 minutes; (5) Post-processing and storage: The tea tree mushrooms obtained by the compound preservative solution in step (4) are drained, vacuum-packed and stored at 0-4℃.

2. The method according to claim 1, characterized in that, The thickness of the flat layer in step (2) is ≤2cm; the diameter of the hole in the hollow shelf is 0.5-1cm.

3. The method according to claim 1, characterized in that, The ultrasonic pretreatment in step (2) has a frequency of 20-40kHz, a power of 150-250W, a treatment time of 20-60s, and the temperature of the sterile water is controlled to be ≤25℃ during the treatment.

4. The method according to claim 1, characterized in that, The mass concentration of the polyphenols in step (3) is 0.04%-0.16%; the mass concentration of the plant essential oil is 0.012%-0.02%.

5. The method according to claim 1, characterized in that, The polyphenolic substances mentioned in step (3) include tea polyphenols and rosemary polyphenols; the mass ratio of tea polyphenols to rosemary polyphenols is (1.2:1)-(1.8:1); the plant essential oil is lemongrass essential oil.

6. The method according to claim 1, characterized in that, The buffer system mentioned in step (3) is a citrate-sodium citrate buffer solution with a pH of 5.5-6.5; and / or, the compound preservation solution also contains 1%-5% ethanol by volume as a co-solvent.

7. The method according to claim 1, characterized in that, The antioxidant aid mentioned in step (3) is vitamin C, and the amount added is 0.01%-0.03% of the total mass of the compound preservative solution.

8. The method according to claim 1, characterized in that, The draining time in step (5) is 5-8 min; and / or, the vacuum packaging is carried out by vacuuming a polyethylene preservation bag to a vacuum degree of 0.06-0.08 MPa.

9. A preserved tea tree mushroom product prepared by the method described in any one of claims 1-8.

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