Method for vacuum freeze-drying chanterelle through ultrasonic wave and freeze-thawing combined pretreatment assistance

Abstract

The invention relates to the technical field of food processing, and discloses a method for vacuum freeze-drying chanterelle through ultrasonic wave and freeze thawing combined pretreatment. The method comprises the following steps: cleaning chanterelle, putting the cleaned chanterelle into clear water, and carrying out ultrasonic treatment to ensure that the chanterelle is completely immersed in the water; after the ultrasonic treatment is finished, draining off the water of the chanterelle, then freezing the chanterelle, then unfreezing the chanterelle at room temperature, draining off the water of the unfrozen chanterelle, and pre-freezing the chanterelle; and performing vacuum freeze drying on the pre-frozen chanterelle to obtain the dried chanterelle product. The method is short in drying time, the prepared chanterelle dried product has the advantages of being natural in color, loose in tissue, high in antioxidant activity, high in nutrient substance retention rate and the like, particularly, the content of functional components such as total phenols and total flavonoids is remarkably increased, and the content of bitter amino acid is reduced.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a method for vacuum freeze-drying of chanterelle bacteria assisted by a combination of ultrasonic and freeze-thaw pretreatment. Background Technology

[0002] Chanterelle mushrooms ( Cantharellus cibarius Chanterelle (Candidae) is one of the most common wild edible fungi in Yunnan Province, China. It gets its name from its rich nutritional content and chicken fat-like color, and also has a unique apricot aroma; it is also known as apricot fungus or yellow silk fungus. Studies have shown that Chanterelle is rich in various nutrients, such as protein, vitamins A, C, and E, and various minerals. It possesses numerous health benefits, including maintaining normal bodily functions, enhancing immunity, antioxidation, antibacterial properties, antihypertensive effects, immune regulation, anti-inflammation, antiviral properties, anti-hypoxia effects, and inhibition of angiotensin-converting enzyme (ACE).

[0003] However, due to their rapid respiration rate and high moisture content, chanterelles are highly susceptible to rapid aging, browning, and spoilage during storage, leading to quality deterioration. These changes not only affect their appearance but also cause nutrient loss, reducing their edible value. Even under refrigeration, their shelf life is short, and their storage stability is poor, severely limiting their commercial development and industrial application. Therefore, how to safely and effectively extend the shelf life of chanterelle products and ensure their quality has become a research hotspot for academics and deep-processing enterprises.

[0004] Currently, common drying methods for chanterelle mushrooms include natural air drying, hot air drying, and vacuum freeze drying. Hot air drying is simple to operate and inexpensive, but the high temperature and aerobic environment easily cause browning, shrinkage, and significant loss of bioactive substances. In contrast, vacuum freeze drying technology can preserve the color, aroma, flavor, and nutrients of dried products to the maximum extent in a low-temperature vacuum environment, making it one of the best drying methods for quality. However, this process still suffers from long drying cycles, high energy consumption, large equipment investment, and nutrient loss, limiting its widespread application in industrial production.

[0005] This invention innovatively combines ultrasound with freeze-thaw processing in the drying process of chanterelle mushrooms, aiming to effectively shorten the vacuum freeze-drying time, reduce energy consumption, and improve the quality and functional component retention rate of dried products, providing a new approach for the development of high-quality edible mushroom drying technology. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for vacuum freeze-drying of chanterelle bacteria assisted by a combination of ultrasonic and freeze-thaw pretreatment, the specific steps of which are as follows: (1) Clean the chanterelle mushrooms thoroughly, and then put the cleaned chanterelle mushrooms into water for ultrasonic treatment to ensure that the chanterelle mushrooms are completely submerged in water.

[0007] (2) After ultrasonic treatment, drain the water from the chanterelles, then freeze the chanterelles, then thaw them at room temperature, drain the water from the thawed chanterelles, and pre-freeze them.

[0008] (3) The pre-frozen chanterelles are freeze-dried under vacuum to obtain dried chanterelle products.

[0009] Preferably, the parameters for ultrasonic treatment in step (1) are: frequency 20kHz, power 400W, and 5s ultrasonic treatment followed by 5s intermittent cycle treatment for 20min.

[0010] Preferably, the freezing temperature in step (2) is -20°C and the freezing time is 24 hours.

[0011] Preferably, the pre-freezing temperature in step (2) is -20°C and the pre-freezing time is 12h.

[0012] Preferably, the conditions for vacuum freeze drying in step (3) are: temperature of -62℃ and absolute pressure of 10Pa.

[0013] Compared with the prior art, the present invention provides a method for vacuum freeze-drying of chanterelle bacteria assisted by a combination of ultrasonic and freeze-thaw pretreatment, which has the following beneficial effects: 1. This invention, through a combination of ultrasonic and freeze-thaw pretreatment, can shorten the vacuum freeze-drying time of chanterelles by up to 37.5%, significantly accelerating the dehydration rate, reducing energy consumption, and improving the economic efficiency and industrial sustainability of the drying process.

[0014] 2. This invention reduces color difference and browning degree in dried chanterelle products by combining ultrasonic waves with freeze-thaw pretreatment, making the appearance closer to that of fresh products. It also increases the total phenol content, total flavonoid content, DPPH free radical scavenging ability, and ABTS free radical scavenging ability in dried chanterelle products, and effectively reduces the content of bitter amino acids. Attached Figure Description

[0015] Figure 1 The microstructure diagrams are of the chanterelles prepared in Examples 1-3 and Comparative Examples 1-4. Detailed Implementation

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0018] Example 1 A method for vacuum freeze-drying of chanterelle bacteria using a combination of ultrasonic and freeze-thaw pretreatment includes the following steps: (1) Raw materials: Select fresh and uniformly sized chanterelles as raw materials, and avoid selecting chanterelles with obvious mechanical damage.

[0019] (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the mud, dust and other impurities on the surface.

[0020] (3) Ultrasonic treatment: Place the cleaned chanterelle mushrooms into clean water, ensuring that the chanterelle mushrooms are completely submerged in the water. Place the container containing the chanterelle mushrooms and clean water into an ultrasonic device. The ultrasonic treatment parameters are: 20kHz, power 400W, and use 5s ultrasonic and 5s intermittent cycle treatment for 20min.

[0021] (4) Freeze-thaw treatment: After ultrasonic treatment, drain the water from the chanterelle mushrooms, gently absorb the excess water on the surface of the chanterelle mushrooms with clean gauze, and then put the chanterelle mushrooms into a freezing device for freezing at -20℃ for 24 hours, and then let them thaw at room temperature.

[0022] (5) Pre-freezing: After the freeze-thaw treatment, drain the water from the chanterelle mushrooms, gently pat dry the excess water on the surface of the chanterelle mushrooms with kitchen paper towels, and then put the chanterelle mushrooms into the freezing equipment and pre-freeze them at -20℃ for 12 hours.

[0023] (6) Vacuum freeze drying: The pre-frozen chanterelles were subjected to vacuum freeze drying at -62℃ (cold trap) and 10Pa (absolute pressure) until the moisture content was <0.1g / g and then the drying was stopped.

[0024] (7) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light.

[0025] Example 2 A method for vacuum freeze-drying of chanterelle bacteria using a combination of ultrasonic and freeze-thaw pretreatment includes the following steps: (1) Raw materials: Select fresh and uniformly sized chanterelles as raw materials, and avoid selecting chanterelles with obvious mechanical damage.

[0026] (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the mud, dust and other impurities on the surface.

[0027] (3) Ultrasonic treatment: Place the cleaned chanterelle mushrooms into clean water, ensuring that the chanterelle mushrooms are completely submerged in the water. Place the container containing the chanterelle mushrooms and clean water into the ultrasonic device. The ultrasonic treatment parameters are: 15kHz, power 350W, and use 4s ultrasonic and 4s intermittent cycle treatment for 15min.

[0028] (4) Freeze-thaw treatment: After ultrasonic treatment, drain the water from the chanterelle mushrooms, gently absorb the excess water on the surface of the chanterelle mushrooms with clean gauze, and then put the chanterelle mushrooms into a freezing device for freezing at -15℃ for 22 hours, and then let them thaw at room temperature.

[0029] (5) Pre-freezing: After the freeze-thaw treatment, drain the water from the chanterelle mushrooms, gently pat dry the excess water on the surface of the chanterelle mushrooms with kitchen paper towels, and then put the chanterelle mushrooms into the freezing equipment and pre-freeze them at -15℃ for 12 hours.

[0030] (6) Vacuum freeze drying: The pre-frozen chanterelles were subjected to vacuum freeze drying at -60℃ (cold trap) and 5Pa (absolute pressure) until the moisture content was <0.1g / g and then the drying was stopped.

[0031] (7) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light.

[0032] Example 3 A method for vacuum freeze-drying of chanterelle bacteria using a combination of ultrasonic and freeze-thaw pretreatment includes the following steps: (1) Raw materials: Select fresh and uniformly sized chanterelles as raw materials, and avoid selecting chanterelles with obvious mechanical damage.

[0033] (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the mud, dust and other impurities on the surface.

[0034] (3) Ultrasonic treatment: Place the cleaned chanterelle mushrooms into clean water, ensuring that the chanterelle mushrooms are completely submerged in the water. Place the container containing the chanterelle mushrooms and clean water into the ultrasonic device. The ultrasonic treatment parameters are: 25kHz, power 450W, and use 6s ultrasonic and 6s intermittent cycle treatment for 25min.

[0035] (4) Freeze-thaw treatment: After ultrasonic treatment, drain the water from the chanterelle mushrooms, gently absorb the excess water on the surface of the chanterelle mushrooms with clean gauze, and then put the chanterelle mushrooms into a freezing device for freezing at -25℃ for 26 hours, and then let them thaw at room temperature.

[0036] (5) Pre-freezing: After the freeze-thaw treatment, drain the water from the chanterelle mushrooms, gently pat dry the excess water on the surface of the chanterelle mushrooms with kitchen paper towels, and then put the chanterelle mushrooms into the freezing equipment and pre-freeze them at -25℃ for 12 hours.

[0037] (6) Vacuum freeze drying: The pre-frozen chanterelles were subjected to vacuum freeze drying at -64℃ (cold trap) and 15Pa (absolute pressure) until the moisture content was <0.1g / g and then the drying was stopped.

[0038] (7) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light.

[0039] Comparative Example 1 In comparison, this comparative example differs from Example 1 in that it does not involve ultrasonication and freeze-thaw treatment. The specific steps are as follows: (1) Raw materials: Select fresh and uniformly sized chanterelle mushrooms as raw materials, and avoid selecting chanterelle mushrooms with obvious mechanical damage; (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the surface dirt and dust and other impurities. (3) Pre-freezing: After cleaning, drain the water from the chanterelle mushrooms. You can gently absorb the excess water on the surface of the chanterelle mushrooms with a clean gauze or kitchen paper towel. Then put the chanterelle mushrooms into a freezing device and pre-freeze them at -20℃ for 12 hours. (4) Vacuum freeze drying: The pre-frozen chanterelles were subjected to vacuum freeze drying at -62℃ (cold trap) and 10Pa (absolute pressure) until the moisture content was <0.1g / g and then the drying was stopped. (5) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light; Comparative Example 2 In comparison, this comparative example differs from Example 1 in that no freeze-thaw treatment is performed before vacuum drying. The specific steps are as follows: (1) Raw materials: Select fresh and uniformly sized chanterelles as raw materials, and avoid selecting chanterelles with obvious mechanical damage.

[0040] (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the mud, dust and other impurities on the surface.

[0041] (3) Ultrasonic treatment: Place the cleaned chanterelle mushrooms into clean water, ensuring that the chanterelle mushrooms are completely submerged in the water. Place the container containing the chanterelle mushrooms and clean water into an ultrasonic device. The ultrasonic treatment parameters are: frequency 20kHz, power 400W, and use 5s ultrasonic treatment + 5s intermittent cycle treatment for 20min.

[0042] (4) Pre-freezing: After cleaning, drain the water from the chanterelle mushrooms. You can gently absorb the excess water on the surface of the chanterelle mushrooms with a clean gauze or kitchen paper towel. Then put the chanterelle mushrooms into a freezing device and pre-freeze them at -20℃ for 12 hours. (5) Vacuum freeze drying: After ultrasonic treatment, drain the water from the chanterelle mushrooms, gently absorb the excess water on the surface of the chanterelle mushrooms with clean gauze, and then freeze dry the chanterelle mushrooms in a vacuum at -62℃ (cold trap) and 10Pa (absolute pressure) until the moisture content is <0.1g / g and then stop drying.

[0043] (6) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light.

[0044] Comparative Example 3 In comparison, this comparative example differs from Example 1 in that it does not undergo ultrasonic treatment and instead undergoes two freeze-thaw cycles. The specific steps are as follows: (1) Raw materials: Select fresh and uniformly sized chanterelles as raw materials, and avoid selecting chanterelles with obvious mechanical damage.

[0045] (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the mud, dust and other impurities on the surface.

[0046] (3) Freeze-thaw treatment: After cleaning, drain the water from the chanterelle mushrooms and gently absorb the excess water on the surface of the chanterelle mushrooms with a clean gauze. Then, put the chanterelle mushrooms into a freezing device for freezing at -20℃ for 24 hours. Then, let them thaw at room temperature. Continue to put them into the freezing device for freezing at -20℃ for 24 hours. Then, let them thaw at room temperature.

[0047] (4) Pre-freezing: After the freeze-thaw treatment, drain the water from the chanterelle mushrooms, gently pat dry the excess water on the surface of the chanterelle mushrooms with kitchen paper towels, and then put the chanterelle mushrooms into the freezing equipment and pre-freeze them at -20℃ for 12 hours.

[0048] (5) Vacuum freeze drying: The pre-frozen chanterelles were subjected to vacuum freeze drying at -62℃ (cold trap) and 10Pa (absolute pressure) until the moisture content was <0.1g / g and then the drying was stopped.

[0049] (6) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light.

[0050] Comparative Example 4 In comparison, this comparative example differs from Example 1 in that it involves two freeze-thaw treatments, the specific steps of which are as follows: (1) Raw materials: Select fresh and uniformly sized chanterelles as raw materials, and avoid selecting chanterelles with obvious mechanical damage.

[0051] (2) Cleaning: Remove the mud and sand from the roots of the selected chanterelle mushrooms, and then rinse them with running water to remove the mud, dust and other impurities on the surface.

[0052] (3) Ultrasonic treatment: Place the cleaned chanterelle mushrooms into clean water, ensuring that the chanterelle mushrooms are completely submerged in the water. Place the container containing the chanterelle mushrooms and clean water into the ultrasonic device. The ultrasonic treatment parameters are: frequency 20kHz, power 400W, and use 5s ultrasonic + 5s intermittent cycle treatment for 20min.

[0053] (4) Freeze-thaw treatment: After ultrasonic treatment, drain the water from the chanterelle mushrooms, gently absorb the excess water on the surface of the chanterelle mushrooms with clean gauze, and then put the chanterelle mushrooms into a freezing device for freezing at -20℃ for 24 hours. Then let them thaw at room temperature and continue to put them into the freezing device for freezing at -20℃ for 24 hours. Then let them thaw at room temperature.

[0054] (5) Pre-freezing: After the freeze-thaw treatment, drain the water from the chanterelle mushrooms, gently pat dry the excess water on the surface of the chanterelle mushrooms with kitchen paper towels, and then put the chanterelle mushrooms into the freezing equipment and pre-freeze them at -20℃ for 12 hours.

[0055] (6) Vacuum freeze drying: The pre-frozen chanterelles were subjected to vacuum freeze drying at -62℃ (cold trap) and 10Pa (absolute pressure) until the moisture content was <0.1g / g and then the drying was stopped.

[0056] (7) Packaging and storage: The dehydrated chanterelles are packaged with food-grade materials and stored away from light.

[0057] The physicochemical properties of the dried chanterelle products prepared in Examples 1-3 and Comparative Examples 1-4 were determined, and the results are shown in Table 1.

[0058] Table 1 Physicochemical properties of dried chanterelle products As shown in Table 1, the drying time of the chanterelles treated with ultrasound-freeze-thaw pretreatment (Example 1) to a moisture content of less than 0.1 g / g was significantly shorter than other treatment groups, resulting in the highest drying efficiency. Furthermore, the dried product from the ultrasound-freeze-thaw pretreatment group (Example 1) exhibited the highest total phenol and flavonoid content, the strongest free radical scavenging ability, significantly enhanced antioxidant activity, and outstanding nutritional and health benefits. Simultaneously, the ultrasound-freeze-thaw pretreatment group (Example 1) showed the smallest color difference (∆E), reduced browning, and an appearance closer to fresh products; bitter amino acids were significantly reduced, resulting in a significant improvement in flavor. In contrast, while ultrasound treatment alone had some improvement effect, it was not as significant as the combined treatment; and repeated freeze-thaw treatment easily led to excessive damage to cell structure and nutrient loss, which was detrimental to product quality improvement.

[0059] The microstructure of the dried chanterelle products prepared in Examples 1-3 and Comparative Examples 1-4 was observed using a Hitachi Regulus 8100 field emission scanning electron microscope. The results are as follows: Figure 1 As shown in the figure, the tissue structure of Comparative Example 1 is intact without obvious pores or cracks, exhibiting a dense tissue structure. Freeze-thaw pretreatment disrupts the fruiting body structure of *Candida albicans*, making it easier for water to be released from the cells, removing most of the water before vacuum freeze-drying and shortening the drying time. However, this pretreatment method causes tissue collapse and shrinkage, resulting in a denser tissue. The more freeze-thaw pretreatments (as in Comparative Examples 3 and 4), the more severe the tissue collapse due to repeated ice crystal formation, leading to a smoother, denser external structure and thus prolonging the drying time. The sample pretreated in Example 2 exhibits small pores, still aiding in water removal, but at a slightly slower rate. After pretreatment in Example 3, a porous structure is induced on the surface of the dried *Candida albicans* tissue, facilitating water removal. Under higher ultrasonic power, the sample forms a denser and smoother surface. This result successfully defines the optimal range for ultrasonic power, demonstrating an upper limit to the power parameter, providing indispensable experimental data support for determining the preferred range of the process described in the claims of this invention. The dried chanterelles pretreated in Example 1 exhibited a significantly larger pore structure. This increased pore size significantly reduced resistance to moisture diffusion, allowing for faster and more efficient moisture migration during the drying process, thereby improving dehydration efficiency and shortening drying time. This confirms the feasibility of a single combined ultrasonic and freeze-thaw treatment.

[0060] In summary, the ultrasonic combined with single-stage freeze-thaw pretreatment process employed in this invention exhibits the best overall performance in improving the drying efficiency of chanterelles, enhancing color, increasing antioxidant capacity, and optimizing flavor quality, demonstrating significant technical advantages. Any other modifications, substitutions, or combinations that do not depart from the basic technical concept and principle of this invention should be considered as falling under the protection of this invention.

Claims

1. A method for vacuum freeze-drying of chanterelle bacteria assisted by a combination of ultrasonic and freeze-thaw pretreatment, characterized in that: Includes the following steps: (1) Clean the chanterelle mushrooms thoroughly, and then put the cleaned chanterelle mushrooms into water for ultrasonic treatment to ensure that the chanterelle mushrooms are completely submerged in water; (2) After ultrasonic treatment, drain the water from the chanterelle mushrooms, then freeze the chanterelle mushrooms, then thaw them at room temperature, drain the water from the thawed chanterelle mushrooms, and then pre-freeze them. (3) The pre-frozen chanterelles are freeze-dried under vacuum to obtain dried chanterelle products.

2. The method for vacuum freeze-drying of chanterelle bacteria assisted by combined ultrasonic and freeze-thaw pretreatment according to claim 1, characterized in that: The parameters for ultrasonic treatment in step (1) are: frequency 15~25kHz, power 350~450W, and ultrasonic treatment for 4~6s, intermittent treatment for 4~6s for 15~25min.

3. The method for vacuum freeze-drying of chanterelle bacteria assisted by combined ultrasonic and freeze-thaw pretreatment according to claim 1, characterized in that: In step (2), the freezing temperature is -15~-25℃ and the freezing time is 22~26h.

4. The method for vacuum freeze-drying of chanterelle bacteria assisted by combined ultrasonic and freeze-thaw pretreatment according to claim 1, characterized in that: In step (2), the pre-freezing temperature is -15~-25℃ and the pre-freezing time is 12h.

5. The method for vacuum freeze-drying of chanterelle bacteria assisted by combined ultrasonic and freeze-thaw pretreatment according to claim 1, characterized in that: The conditions for vacuum freeze drying in step (3) are: temperature -60~-64℃ and absolute pressure 5~15Pa.

6. The method for vacuum freeze-drying of chanterelle bacteria assisted by combined ultrasonic and freeze-thaw pretreatment according to claim 1, characterized in that: In step (3), drying is stopped when the moisture content of the chanterelle is less than 0.1 g / g.

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