Method for preparing dendrobium officinale full-liquid yoghurt through ultrasonic synergistic composite enzymolysis method

Abstract

The invention relates to a method for preparing dendrobium officinale full-liquid yoghurt by an ultrasonic synergistic composite enzymolysis method. The method comprises the following steps: selecting and treating raw materials; putting the dendrobium officinale stem slurry into an ultrasonic device, and then starting the ultrasonic device to carry out ultrasonic treatment on the dendrobium officinale stem slurry for a certain time; adding a compound enzyme mixture into the dendrobium officinale stem slurry subjected to ultrasonic pretreatment, and carrying out enzymolysis reaction to obtain enzymolysis slurry; terminating the enzymolysis reaction; filtering, centrifuging and collecting supernate to obtain dendrobium officinale whole liquid; performing freeze-drying treatment; adding the dendrobium officinale whole liquid freeze-dried powder into milk to form a mixed solution, and then adding streptococcus thermophilus and lactobacillus bulgaricus into the uniformly stirred mixed solution for fermentation to form the yoghourt. The method has the advantages that the physical wall breaking effect of ultrasonic waves and the biological catalysis effect of the compound enzyme are combined, so that the extraction efficiency of active ingredients such as polysaccharide, anthocyanin and amino acid in the dendrobium officinale stems is improved, and the biological activity of the ingredients is reserved to the maximum extent.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of Dendrobium officinale full-liquid yogurt, and particularly relates to a method for preparing Dendrobium officinale full-liquid yogurt through an ultrasound-assisted composite enzymatic hydrolysis method. Background Art

[0002] In recent years, Dendrobium officinale, a precious medicinal and edible plant, has garnered widespread attention for its unique bioactive ingredients and health benefits. Its main components include polysaccharides, alkaloids, anthocyanins, and amino acids, and possess numerous benefits, including anti-aging, antioxidant properties, immune regulation, and digestive benefits. Currently, market development of Dendrobium officinale's functional properties is primarily focused on health supplements and teas, while products using it as an ingredient in functional yogurt are relatively rare.

[0003] Existing common extraction technologies for Dendrobium officinale include traditional water extraction, enzymatic hydrolysis, and ultrasonic-assisted extraction. However, each of these methods has its own advantages and disadvantages: (1) Water extraction: As the most traditional extraction method, water extraction has the advantages of simple operation and low cost. It can extract a certain amount of polysaccharides and other water-soluble components from Dendrobium officinale by hot water extraction. However, the disadvantages of water extraction are also very obvious. Its extraction rate is low, only reaching about 12.07%. This is because the cell wall of Dendrobium officinale is relatively hard, and water extraction is difficult to efficiently destroy the cell wall, resulting in insufficient release of active ingredients and ultimately limited extraction rate.

[0004] (2) Enzymatic hydrolysis: Enzymatic hydrolysis technology utilizes the biocatalytic action of enzymes to effectively degrade plant cell walls, thereby improving the extraction efficiency of polysaccharides. Studies have shown that the extraction rate of Dendrobium officinale polysaccharides can be increased to 20.84% through the action of cellulase. Although enzymatic hydrolysis has significantly improved the extraction efficiency, due to the complex structure of plant cell walls, the extraction effect still has certain limitations when relying solely on the catalytic action of enzymes. In addition, the extraction time of enzymatic hydrolysis is relatively long (more than 1 hour), and the control of temperature and enzyme activity is required to be high.

[0005] (3) Ultrasonic-assisted extraction: The introduction of ultrasonic technology, through the cavitation effect and mechanical action it produces, can destroy the cell wall structure and promote the release of active substances in the cells. Studies have shown that when ultrasonic extraction technology is used alone, the extraction rate of polysaccharides can reach 18%-25%. However, although ultrasonic technology performs well in breaking down the cell wall, it cannot further decompose large molecular polysaccharides without enzymatic hydrolysis, resulting in low bioavailability of the extracted active ingredients and difficulty for some functional ingredients to be fully absorbed by the human body.

[0006] In summary, existing water extraction, enzymatic hydrolysis, and ultrasound-assisted extraction methods each have certain advantages, but also significant shortcomings. Water extraction has a low extraction rate, enzymatic hydrolysis takes a long time, and single enzymatic hydrolysis is difficult to completely release the active ingredients. While ultrasonic extraction can improve extraction efficiency, it fails to fully decompose the complex polysaccharide structure. In particular, the existing technology has not yet combined ultrasound with complex enzymatic hydrolysis technology to extract the active ingredients of Dendrobium officinale.

[0007] Therefore, how to overcome the limitations of the cell wall of Dendrobium officinale and improve the extraction rate of active ingredients while maintaining the biological activity of these ingredients is a major challenge faced by the existing technology. To address this problem, the present invention proposes an "ultrasound-synergistic composite enzymatic hydrolysis method" that effectively improves the extraction efficiency of Dendrobium officinale active ingredients and enhances their bioavailability through the synergistic effect of ultrasound and multiple enzymes, thereby overcoming the shortcomings of the existing technology. Summary of the Invention

[0008] Design purpose: To avoid the shortcomings of the background technology, a method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis is designed, comprising the following steps: Step 1: Raw material selection and processing First, fresh Dendrobium officinale stems are selected as raw materials, and then the fresh Dendrobium officinale stems are cleaned to remove impurities, and then the cleaned fresh Dendrobium officinale stems are cut into small segments of 1-2 cm and then the Dendrobium officinale stem slurry is prepared, and the small segments of fresh Dendrobium officinale stems are first mixed with distilled water to form a solid-liquid mixture, and then the solid-liquid mixture is homogenized by a homogenizer to form the Dendrobium officinale stem slurry; Step 2: Ultrasonic pretreatment The prepared Dendrobium officinale stem slurry is placed in an ultrasonic device, and then the ultrasonic device is started to perform ultrasonic treatment on the Dendrobium officinale stem slurry for a certain period of time, wherein the power of the ultrasonic wave generated by the ultrasonic device is 300 W and the frequency range of the ultrasonic wave is 20-40 kHz; Step 3: Compound enzymatic extraction adding the prepared complex enzyme mixture to the ultrasonically pretreated Dendrobium officinale stem slurry for enzymolysis reaction to obtain an enzymolysis slurry, wherein the Dendrobium officinale stem slurry is continuously stirred during the enzymolysis reaction to ensure that the complex enzyme is in full contact with the Dendrobium officinale stem slurry; Step 4: Terminate the enzymatic reaction After the enzymatic hydrolysis was completed, the enzymatic slurry was heated to 100 °C and maintained for 3 minutes to terminate the enzyme activity; Step 5: Filtration and centrifugation The enzymatic hydrolysis slurry after the enzymatic hydrolysis reaction is terminated is filtered to remove insoluble impurities, and then the filtered enzymatic hydrolysis slurry is centrifuged, and after the centrifugation is completed, the supernatant is collected to obtain the Dendrobium officinale liquid; Step 6: Freeze-drying The collected Dendrobium officinale liquid is treated with a vacuum freeze dryer to obtain a freeze-dried powder of the Dendrobium officinale liquid; Step 7: Yogurt fermentation The freeze-dried powder of Dendrobium officinale whole liquid is added to milk to form a mixed liquid, and then the mixed liquid is evenly stirred. Then, thermophilic Streptococcus and Lactobacillus bulgaricus are added to the evenly stirred mixed liquid for fermentation to form yogurt.

[0009] Preferably, the step 8 is also included, seasoning After fermentation is complete, the yogurt is quickly cooled to 4°C and flavored with citrus pectin and wolfberry polysaccharides.

[0010] Preferably, the solid-liquid mass ratio in the solid-liquid mixture is 1:19.

[0011] Preferably, the ultrasonic treatment time is 20 minutes, and the power density of the ultrasonic wave is 22.5 W / mL.

[0012] Preferably, the complex enzyme mixture is composed of cellulase, maltogenic amylase, pectinase and neutral protease, and the mass ratio of cellulase, maltogenic amylase, pectinase and neutral protease is 8:5:3:4; the mass concentration of cellulase in the Dendrobium officinale stem slurry to which the complex enzyme mixture is added is 0.8% w / v, the mass concentration of maltogenic amylase is 0.5% w / v, the mass concentration of pectinase is 0.3% w / v, and the mass concentration of neutral protease is 0.4% w / v.

[0013] Preferably, the enzymatic hydrolysis reaction is carried out in a constant temperature water bath at 50° C. and the enzymatic hydrolysis reaction time is 20 minutes.

[0014] Preferably, the filtered enzymatic slurry is heated at 3900× g The centrifugal treatment was carried out at a centrifugal force of 1000 nm and the centrifugal treatment time was 18 minutes.

[0015] Preferably, the treatment process is as follows: the freeze-drying treatment in step six is specifically as follows: first, the whole liquid of Dendrobium officinale is frozen to a solid state at -80°C, then gradually heated to 0°C under vacuum conditions, and moisture is removed to obtain freeze-dried powder of the whole liquid of Dendrobium officinale.

[0016] Preferably, the mass of the freeze-dried powder of Dendrobium officinale accounts for 5%-10% of the total mass of the mixed solution, the thermophilic Streptococcus is inoculated at a bacterial liquid volume of 1% per liter of milk, and the bulgaricus is inoculated at a bacterial liquid volume of 1% per liter of milk. Preferably, the mixed solution is fermented at 42° C. for 6-8 hours until the pH value of the yogurt drops to 4.5 and the yogurt fermentation is completed.

[0017] Compared with the background technology, the present invention has the following advantages: The first is a method for preparing Dendrobium officinale full-liquid yogurt through ultrasound-assisted composite enzymatic hydrolysis. This method combines the physical wall-breaking effect of ultrasound with the biocatalytic action of composite enzymes to improve the extraction efficiency of active ingredients such as polysaccharides, anthocyanins, and amino acids from the stems of Dendrobium officinale (with a sugar extraction rate of 34.5%) while maximally retaining the biological activity of these ingredients (with anthocyanin content as high as 85%). The second is a method for preparing a Dendrobium officinale liquid yogurt using an ultrasound-assisted composite enzymatic hydrolysis method. Through synergistic extraction (ultrasound-assisted composite enzymatic hydrolysis), the utilization rate of the active ingredients is significantly improved (after this treatment, polysaccharides with larger molecular weights are degraded into small molecular weight oligosaccharides and oligosaccharides that are more easily absorbed by the human body. The molecular weight distribution of the polysaccharides was determined using SEC-HPLC technology. Experimental data showed that the molecular weight of the treated polysaccharides was significantly reduced, with most concentrated in the range of 200-300 kDa, which is approximately 50% less than the original high-molecular-weight polysaccharides, demonstrating that this method can effectively improve the bioavailability of polysaccharides and enhance their health benefits); The third is a method for preparing Dendrobium officinale full-liquid yogurt through ultrasound-assisted composite enzymatic hydrolysis. The production of acetic acid, propionic acid, butyric acid and valeric acid through ultrasound-assisted composite enzymatic hydrolysis treatment is significantly higher than other existing methods, especially the production of butyric acid and valeric acid (the production of butyric acid reaches 8 μmol / g, and that of valeric acid is 4 μmol / g), indicating the advantage of this method in promoting the production of beneficial metabolites in the intestine; in addition, in terms of the α diversity of intestinal flora, the ultrasound-assisted composite enzymatic hydrolysis method also performed outstandingly. Through the determination of Chao1 and Shannon indexes, we found that the α diversity of the treatment group was significantly increased (Chao1 index was 363, Shannon index was 5). Since the microbial diversity of the ultrasound-assisted composite enzymatic hydrolysis group was richer and more balanced, it shows that this method can better promote the balance of intestinal microecology and help improve intestinal health.

[0018] The fourth method is a method for preparing Dendrobium officinale full-liquid yogurt through ultrasound-assisted composite enzymatic hydrolysis. The extracted Dendrobium officinale full-liquid powder is combined with a yogurt base, retaining components such as polysaccharides, anthocyanins, and amino acids. Through fermentation with lactic acid bacteria, the intestinal regulation, immune regulation, and antioxidant functions of the yogurt are further enhanced. The yogurt product obtained by this preparation method not only has the nutritional value of ordinary yogurt, but also has richer health functions and significant antioxidant activity, meeting consumers' demand for healthy food. Fifth, a method for preparing Dendrobium officinale liquid yogurt through ultrasound-assisted composite enzymatic hydrolysis introduces vacuum freeze-drying technology, which can remove moisture from the Dendrobium officinale liquid under low temperature conditions, maintain the original function of the active ingredients, and significantly extend the shelf life of the product. In addition, the freeze-dried powder is easy to store and transport, improving the processing convenience of the product; The sixth is a Dendrobium officinale full-liquid yogurt prepared by ultrasound-assisted composite enzymatic hydrolysis, which can stabilize the anthocyanins in Dendrobium officinale under mild conditions (the anthocyanin content is as high as 85%), making the yogurt product present a natural pink and purple color. This visual effect not only enhances the sensory experience of the product, but also meets consumers' preference for healthy and natural foods, thereby improving the product's market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a data table showing the effects of different extraction methods on the extraction rate (%) of Dendrobium polysaccharides (comparison of four test data).

[0020] Figure 2 This is a data table showing the effects of different extraction methods on the peak molecular weight of Dendrobium polysaccharides (Component 1 and Component 2 are two types of polysaccharides in Dendrobium).

[0021] Figure 3 This is a data chart showing the effects of different extraction methods on the short-chain fatty acid content (methyl acetate) produced by Dendrobium polysaccharides.

[0022] Figure 4 This is a data chart showing the effects of different extraction methods on the short-chain fatty acid content (methyl propionate) produced by Dendrobium polysaccharides.

[0023] Figure 5 This is a data chart showing the effects of different extraction methods on the short-chain fatty acid content (methyl butyrate) produced by Dendrobium polysaccharides.

[0024] Figure 6 This is a data chart showing the effects of different extraction methods on the short-chain fatty acid content (methyl valerate) produced by Dendrobium polysaccharides.

[0025] Figure 7 This is a data chart showing the effects of different extraction methods on the α-diversity of intestinal flora (Chao1 index).

[0026] Figure 8 This is a data chart showing the effects of different extraction methods on the α-diversity of intestinal flora (Shannon index). DETAILED DESCRIPTION

[0027] Example 1: Refer to the attached Figures 1-8 A method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis comprises the following steps: Step 1: Raw material selection and processing First, fresh Dendrobium officinale stems are selected as raw materials, and then the fresh Dendrobium officinale stems are washed to remove impurities, and then the washed fresh Dendrobium officinale stems are cut into small segments of 1-2 cm (to increase the surface area for subsequent ultrasonic treatment and enzymatic hydrolysis), and then Dendrobium officinale stem slurry is prepared, and the small segments of fresh Dendrobium officinale stems are first mixed with distilled water to form a solid-liquid mixture, and then the solid-liquid mixture is homogenized by a homogenizer to form Dendrobium officinale stem slurry; Step 2: Ultrasonic pretreatment The prepared Dendrobium officinale stem slurry is placed in an ultrasonic device, which is then started to perform ultrasonic treatment on the Dendrobium officinale stem slurry for a certain period of time. The ultrasonic power generated by the ultrasonic device is 300 W and the frequency range of the ultrasonic wave is 20-40 kHz. The ultrasonic wave generates microbubbles in the slurry through its cavitation effect. The high temperature and high pressure formed when these bubbles burst can effectively destroy the structure of the cell wall, thereby promoting the release of active ingredients in the cells.

[0028] Step 3: Compound enzymatic extraction The pre-prepared complex enzyme mixture is added to the Dendrobium officinale stem slurry that has been pretreated by ultrasound to carry out an enzymatic hydrolysis reaction to obtain an enzymatic hydrolysis slurry. During the enzymatic hydrolysis reaction, the Dendrobium officinale stem slurry is continuously stirred to ensure that the complex enzyme is in full contact with the Dendrobium officinale stem slurry. The complex enzymatic hydrolysis process can further decompose the polysaccharides, proteins and pectin in the Dendrobium officinale stem, thereby releasing more active ingredients.

[0029] Step 4: Terminate the enzymatic reaction After the enzymatic hydrolysis is completed, the enzymatic slurry is heated to 100°C and maintained for 3 minutes to terminate the activity of the enzyme and prevent excessive reaction from affecting the active ingredients.

[0030] Step 5: Filtration and centrifugation The enzymatic hydrolysis slurry after the enzymatic hydrolysis reaction is terminated is filtered to remove insoluble impurities, and then the filtered enzymatic hydrolysis slurry is centrifuged. After the centrifugation is completed, the supernatant is collected to obtain the Dendrobium officinale liquid; the Dendrobium officinale liquid is rich in polysaccharides, anthocyanins, amino acids and other active ingredients.

[0031] Step 6: Freeze-drying The collected Dendrobium officinale whole liquid is processed by a vacuum freeze dryer to obtain a freeze-dried powder of the Dendrobium officinale whole liquid; the powder is easy to store and transport, and can maintain the stability of the active ingredients in the subsequent yogurt production process.

[0032] Step 7: Yogurt fermentation The freeze-dried powder of Dendrobium officinale whole liquid is added to milk to form a mixed liquid, and then the mixed liquid is evenly stirred. Then, thermophilic Streptococcus and Lactobacillus bulgaricus are added to the evenly stirred mixed liquid for fermentation to form yogurt.

[0033] Also includes step eight, seasoning After fermentation, the yogurt is quickly cooled to 4°C and flavored with citrus pectin and wolfberry polysaccharides to enhance its texture and functionality. Once packaged, it is stored and transported using aseptic cold chain technology to maintain product freshness and stability.

[0034] The solid-liquid mass ratio in the solid-liquid mixture is 1:19. The ultrasonic treatment time is 20 minutes, and the power density of the ultrasonic wave is 22.5 W / mL. The complex enzyme mixture is composed of cellulase, maltogenic amylase, pectinase and neutral protease, and the mass ratio between cellulase, maltogenic amylase, pectinase and neutral protease is 8:5:3:4; the Dendrobium officinale stem slurry to which the complex enzyme mixture is added has a cellulase mass concentration of 0.8% w / v, a maltogenic amylase mass concentration of 0.5% w / v, a pectinase mass concentration of 0.3% w / v and a neutral protease mass concentration of 0.4% w / v. The enzymatic hydrolysis reaction is carried out in a constant temperature water bath at 50°C and the enzymatic hydrolysis reaction time is 20 minutes. The filtered enzymatic hydrolysis slurry is heated at 3900× g The centrifugal force is centrifuged and the centrifugal treatment time is 18 minutes. The treatment process is as follows: the freeze-drying treatment in step six is as follows: first, the whole liquid of Dendrobium officinale is frozen to a solid state at -80°C, and then gradually heated to 0°C under vacuum conditions to remove moisture to obtain the freeze-dried powder of Dendrobium officinale whole liquid. The mass of the freeze-dried powder of Dendrobium officinale whole liquid accounts for 5%-10% of the total mass of the mixed liquid, the thermophilic Streptococcus is inoculated with 1% of the bacterial liquid per liter of milk, and the bulgaricus Lactobacillus is inoculated with 1% of the bacterial liquid per liter of milk. The mixed liquid is fermented at 42°C for 6-8 hours until the pH value of the yogurt drops to 4.5 and the yogurt fermentation is completed.

[0035] The present invention successfully overcomes the shortcomings of the existing technology, such as low extraction efficiency, harsh extraction conditions, and easy degradation of heat-sensitive components, by using ultrasound-assisted enzymatic hydrolysis, significantly improving the extraction rate of active ingredients in Dendrobium officinale while ensuring its biological activity.

[0036] 1. Improved the extraction rate of active ingredients Compared with enzymatic hydrolysis or ultrasonic hydrolysis alone, the ultrasound-assisted composite enzymatic hydrolysis method of the present invention significantly improves the extraction rate of active ingredients such as polysaccharides from Dendrobium officinale. The stem slurry was first ultrasonically pretreated at an ultrasonic power density of 22.5 W / mL for 20 minutes. The ultrasonically treated stem slurry was then subjected to composite enzymatic hydrolysis, resulting in a polysaccharide extraction rate of 34.5%, a significant improvement over ultrasonic extraction alone (18%-25%) and enzymatic extraction alone (20.8%).

[0037] 2. Optimized extraction time and conditions Traditional water extraction (high-temperature extraction) requires long extraction times and high temperature control, which can easily damage heat-sensitive components in Dendrobium officinale, such as polysaccharides and anthocyanins, and reduce the functionality of the extract. This invention utilizes a gentle enzymatic hydrolysis and ultrasound synergistic technology, controlling the temperature at 50°C during the enzymatic hydrolysis process. This reduces the extraction time to 20 minutes, preventing thermal degradation of the active ingredients. After the extraction is complete, the enzymatic hydrolysis reaction is terminated with only a brief high-temperature treatment (100°C for 3 minutes), ensuring that no damage is caused to the active ingredients in the extract.

[0038] Compared to traditional high-temperature extraction processes (such as boiling for one hour), which can cause anthocyanin degradation, this method avoids this. Spectrophotometric determination shows that ultrasound-assisted enzymatic hydrolysis retains up to 85% of anthocyanins, compared to the typical 50%-60% retention rate achieved with high-temperature extraction.

[0039] 3. Enhanced bioavailability and absorbability of the product Traditional methods for extracting Dendrobium officinale yield polysaccharides with complex molecular structures (larger molecular weight polysaccharides), making them difficult for the human body to directly absorb. The present invention optimizes the molecular weight distribution of polysaccharides through ultrasound-assisted enzymatic hydrolysis, effectively reducing their degree of polymerization. This treatment degrades the larger molecular weight polysaccharides into smaller oligosaccharides and oligosaccharides that are more easily absorbed by the human body. The molecular weight distribution of the polysaccharides was determined using SEC-HPLC technology. Experimental data showed that the molecular weight of the treated polysaccharides was significantly reduced, with the majority concentrated in the 200-300 kDa range, a reduction of approximately 50% compared to the original high-molecular-weight polysaccharides. This demonstrates that this method can effectively improve the bioavailability of polysaccharides and enhance their health benefits.

[0040] Fourth, in the experiments of the present invention, we analyzed the effects of different treatment methods on the content of short-chain fatty acids (SCFAs) and concluded that the ultrasound-assisted combined enzymatic hydrolysis group had significantly higher production of acetic acid, propionic acid, butyric acid, and valeric acid than the other treatment groups, especially the production of butyric acid and valeric acid. The specific data are as follows: in the ultrasound-assisted combined enzymatic hydrolysis group, the production of butyric acid reached 8μmol / g and the production of valeric acid was 4μmol / g, which were much higher than those in the traditional water extraction group (butyric acid 5μmol / g, valeric acid 0.6μmol / g), demonstrating the advantages of this method in promoting the production of beneficial metabolites in the intestine. In contrast, the ultrasound treatment group alone and the combined enzymatic hydrolysis group alone did not increase the production of SCFAs as effectively as the synergistic group. Figure 3-Figure 6 In the scatter plot, points without the same lowercase letters indicate significant differences among treatments ( P <0.05).

[0041] The ultrasound-assisted combined enzymatic hydrolysis method also performed exceptionally well in terms of intestinal microbial alpha diversity. Chao1 and Shannon indices were measured, revealing a significant increase in alpha diversity in this treatment group, with a Chao1 index of 363 and a Shannon index of 5, both significantly higher than those in the other treatment groups. In particular, compared with the traditional water extraction group (Chao1 index of 165 and Shannon index of 1.8), the ultrasound-assisted combined enzymatic hydrolysis group demonstrated a richer and more balanced microbial diversity, demonstrating that this method can better promote a balanced intestinal microbiome and contribute to improved intestinal health. Figure 7-Figure 8 In the scatter plot, points without the same lowercase letters indicate significant differences among treatments ( P <0.05).

[0042] 5. Improved the comprehensive functionality of yogurt products The technical solution of the present invention combines extracted Dendrobium officinale liquid powder with a yogurt base, retaining components such as polysaccharides, anthocyanins, and amino acids. Furthermore, through fermentation with lactic acid bacteria, the intestinal regulation, immune regulation, and antioxidant functions of the yogurt are further enhanced. The resulting yogurt product, while retaining the nutritional value of conventional yogurt, is endowed with enhanced health benefits and significant antioxidant activity, satisfying consumers' demand for healthy foods.

[0043] 6. The introduction of freeze-drying technology improves the storage and processing convenience of products While traditional extraction methods, such as alcohol precipitation, can result in the loss of some active ingredients, the vacuum freeze-drying technology introduced in this invention removes moisture from the Dendrobium officinale liquid at low temperatures, preserving the original functions of the active ingredients and significantly extending the product's shelf life. Furthermore, the freeze-dried powder is easy to store and transport, enhancing the product's processing convenience.

[0044] 7. Enriched product sensory experience and visual appeal The process of the present invention can stabilize the anthocyanins in Dendrobium officinale under mild conditions, so that the yogurt product presents a natural pink and purple color. This visual effect not only enhances the sensory experience of the product, but also meets consumers' preference for healthy and natural food, thereby improving the market competitiveness of the product.

[0045] In summary, the present invention demonstrates significant superiority in solving the problems of low extraction efficiency, poor retention of active ingredients, long extraction time and low bioavailability of traditional extraction technologies. Through the innovative application of ultrasound-assisted composite enzymatic hydrolysis technology, the efficient extraction and retention of active ingredients such as Dendrobium officinale polysaccharides are successfully achieved, providing a new direction and broader market prospects for the development of yogurt products.

[0046] It should be understood that although the above embodiments provide a relatively detailed textual description of the design ideas of the present invention, these textual descriptions are only simple textual descriptions of the design ideas of the present invention, rather than limitations on the design ideas of the present invention. Any combination, addition or modification that does not exceed the design ideas of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis, characterized by comprising the following steps: Step 1: Raw material selection and processing First, fresh Dendrobium officinale stems are selected as raw materials, and then the fresh Dendrobium officinale stems are cleaned to remove impurities, and then the cleaned fresh Dendrobium officinale stems are cut into small segments of 1-2 cm and then the Dendrobium officinale stem slurry is prepared, and the small segments of fresh Dendrobium officinale stems are first mixed with distilled water to form a solid-liquid mixture, and then the solid-liquid mixture is homogenized by a homogenizer to form the Dendrobium officinale stem slurry; Step 2: Ultrasonic pretreatment The prepared Dendrobium officinale stem slurry is placed in an ultrasonic device, and then the ultrasonic device is started to perform ultrasonic treatment on the Dendrobium officinale stem slurry for a certain period of time, wherein the power of the ultrasonic wave generated by the ultrasonic device is 300 W and the frequency range of the ultrasonic wave is 20-40 kHz; Step 3: Compound enzymatic extraction adding the prepared complex enzyme mixture to the ultrasonically pretreated Dendrobium officinale stem slurry for enzymolysis reaction to obtain an enzymolysis slurry, wherein the Dendrobium officinale stem slurry is continuously stirred during the enzymolysis reaction to ensure that the complex enzyme is in full contact with the Dendrobium officinale stem slurry; Step 4: Terminate the enzymatic reaction After the enzymatic hydrolysis was completed, the enzymatic slurry was heated to 100 °C and maintained for 3 minutes to terminate the enzyme activity; Step 5: Filtration and centrifugation The enzymatic hydrolysis slurry after the enzymatic hydrolysis reaction is terminated is filtered to remove insoluble impurities, and then the filtered enzymatic hydrolysis slurry is centrifuged, and after the centrifugation is completed, the supernatant is collected to obtain the Dendrobium officinale liquid; Step 6: Freeze-drying The collected Dendrobium officinale liquid is treated with a vacuum freeze dryer to obtain a freeze-dried powder of the Dendrobium officinale liquid; Step 7: Yogurt fermentation The freeze-dried powder of Dendrobium officinale whole liquid is added to milk to form a mixed liquid, and then the mixed liquid is evenly stirred. Then, thermophilic Streptococcus and Lactobacillus bulgaricus are added to the evenly stirred mixed liquid for fermentation to form yogurt.

2. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1, characterized in that: Also includes step eight, seasoning After fermentation is complete, the yogurt is quickly cooled to 4°C and flavored with citrus pectin and wolfberry polysaccharides.

3. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The solid-liquid mass ratio in the solid-liquid mixture is 1:

19.

4. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The ultrasonic treatment time was 20 minutes, and the ultrasonic power density was 22.5 W / mL.

5. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The complex enzyme mixture consists of cellulase, maltogenic amylase, pectinase and neutral protease, and the mass ratio of cellulase, maltogenic amylase, pectinase and neutral protease is 8:5:3:4; the mass concentration of cellulase in the Dendrobium officinale stem slurry added with the complex enzyme mixture is 0.8% w / v, the mass concentration of maltogenic amylase is 0.5% w / v, the mass concentration of pectinase is 0.3% w / v, and the mass concentration of neutral protease is 0.4% w / v.

6. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The enzymatic hydrolysis reaction was carried out in a constant temperature water bath at 50° C. and the enzymatic hydrolysis reaction time was 20 minutes.

7. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The filtered enzymatic slurry was heated at 3900× g The centrifugal treatment was carried out at a centrifugal force of 1000 nm and the centrifugal treatment time was 18 minutes.

8. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The processing process is as follows: The freeze-drying treatment in step six is as follows: first, the whole liquid of Dendrobium officinale is frozen to a solid state at -80°C, and then gradually heated to 0°C under vacuum conditions to remove moisture to obtain freeze-dried powder of Dendrobium officinale whole liquid.

9. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The mass of the freeze-dried powder of Dendrobium officinale accounts for 5%-10% of the total mass of the mixed liquid. The thermophilic Streptococcus is inoculated at a bacterial seed liquid volume of 1% per liter of milk, and the bulgaricus is inoculated at a bacterial seed liquid volume of 1% per liter of milk.

10. The method for preparing Dendrobium officinale full liquid yogurt by ultrasound-assisted composite enzymatic hydrolysis according to claim 1 or 2, characterized in that: The mixed solution is fermented at 42° C. for 6-8 hours until the pH value of the yogurt drops to 4.5, indicating that the yogurt fermentation is complete.

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