A preparation method of polygonatum sibiricum natural fermentation and lactic acid bacteria mixed treatment and application in rice porridge

Abstract

The invention discloses a preparation method of polygonatum sibiricum natural fermentation and lactic acid bacteria mixed treatment and application in rice porridge, wherein polygonatum sibiricum is subjected to three natural fermentations and then liquid fermentation is continued by lactic acid bacteria, and obvious synergistic effect is produced between the two different fermentation methods, and the flavor and biological activity of the processed product can be fully retained or increased, and high-quality polygonatum sibiricum fermentation product is obtained by optimizing fermentation process parameters. The invention mixes the polygonatum sibiricum fermentation product with rice porridge to obtain a rice porridge food with excellent taste and flavor and rich nutrition.

Description

Technical Field

[0001] The invention relates to the technical field of medicine and food, and in particular to a preparation method of polygonatum sibiricum natural fermentation and lactic acid bacteria mixed treatment and application thereof in rice porridge, and more particularly to a preferred standardized polygonatum sibiricum fermentation process suitable for modern industrial production and application thereof in rice porridge. Background Art

[0002] Polygonatum belongs to the genus Polygonatum of the Liliaceae family. It is divided into three species: Polygonatum sibiricum Red, Polygonatum kingianum Coll. et Hemsl, and Polygonatum cyrtonema Hua. According to their different shapes, they are commonly known as "big polygonatum", "chicken-headed polygonatum", and "ginger-shaped polygonatum". Polygonatum is rich in a variety of biological functional substances, such as polygonatum polysaccharides, steroidal saponins, flavonoids, and amino acids. The Compendium of Materia Medica records that Polygonatum has the effects of replenishing deficiency, stopping cold and heat, and filling essence. Modern research shows that Polygonatum has the effects of regulating immunity, anti-tumor, anti-aging, lowering blood sugar, improving sleep, and preventing and treating nervous system diseases. With the development of society and the improvement of people's health awareness, the development of medicinal and edible resources such as Polygonatum with important physiological functions in the food field has gradually received attention.

[0003] Eating raw Polygonatum sibiricum can cause a numb tongue sensation and has a certain degree of irritation to the throat and esophagus, so the "nine steaming and nine drying" processing process was developed, which promotes the release of effective substances, eliminates irritation, improves the flavor of Polygonatum sibiricum and ensures the stability of its medicinal properties. However, the traditional "nine steaming and nine drying" process is complicated and cumbersome to operate, and according to research, "nine" was a quantifier in ancient times, so whether it must be steamed nine times needs further study.

[0004] Microbial fermentation is a biotransformation method. The fermentation extraction method mainly uses enzymes produced by microorganisms to degrade plant cell walls, so that the active substances in plant cells can be released, thereby achieving the purpose of efficiently extracting plant active substances; at the same time, the toxic components in plants can be effectively degraded or converted into low-toxic substances during the fermentation process; in addition, microbial fermentation is often selected to achieve the synthesis of some active lead compounds, mainly using enzymes produced by secondary metabolism during the growth of microorganisms to modify the structure of substrates, thereby producing new compounds and improving the activity of products.

[0005] Natural fermentation and liquid fermentation are different fermentation methods. Natural fermentation is synergistically acted upon by a variety of beneficial microorganisms. Microorganisms decompose macromolecular compounds such as carbohydrates, proteins, and fats in the raw materials to produce small molecular flavor substances such as alcohols, aldehydes, acids, esters, and phenols. Pure fermentation is a modern technology that uses a single strain or a mixed strain for fermentation under aseptic operation. Because pure fermentation mostly uses a single fermentation strain, the enzyme system involved in the biochemical reaction is relatively small, and the content of the fermentation product is relatively low, modern fermentation technology is widely used in the manufacture of simple ingredients and high purity medicines, industrial fermented foods, and other fields. The biggest advantage of pure fermentation is that the fermentation strain is single and less polluting. Pure fermentation advantage strains can be artificially screened to improve and optimize the process.

[0006] After fermentation, Polygonatum sibiricum can reduce the numbness in the mouth after eating Polygonatum sibiricum, reduce the irritation to the throat, and make the metabolites coordinate with each other, which can improve the flavor of the product and increase the nutritional value of the product. However, there is no mixed fermentation mode using natural fermentation and pure strain fermentation. It is still unknown whether mixed fermentation can utilize the mutual synergy and complementarity between different microorganisms to improve the flavor substances and biological functions of Polygonatum sibiricum.

[0007] The fermented polygonatum sibiricum is added to rice porridge in a certain proportion to prepare a new polygonatum sibiricum rice porridge product with good flavor and nutritional and health functions, in order to promote the development of polygonatum sibiricum in the food field and provide technical reference and theoretical basis for the industrial production of polygonatum sibiricum. Summary of the invention

[0008] The invention aims to provide a method for preparing a rice porridge food with high effective component content and biological activity by natural fermentation of polygonatum and mixed treatment with lactic acid bacteria, and applying the fermentation product to rice porridge to obtain a rice porridge food with excellent taste and flavor and rich nutrition.

[0009] The object of the present invention is achieved in that:

[0010] A method for preparing polygonatum by natural fermentation and mixed treatment with lactic acid bacteria, the method comprising the following steps:

[0011] (1) taking dried polygonatum sibiricum medicinal materials, cleaning and selecting, wherein the cleaning and selecting includes removing impurities, separating the polygonatum sibiricum by size, and washing; then steaming the polygonatum sibiricum, naturally fermenting the steamed polygonatum sibiricum, and then drying it in the sun, and repeating the steaming, natural fermentation, and sun drying process three times;

[0012] (2) mixing the polygonatum treated in step (1) with water in a mass ratio of 1:(8-12), homogenizing, adding acetic acid and baking soda to adjust the pH value to 7-7.8, and then sterilizing in a high-temperature autoclave at a sterilization temperature of 120° C. for 30 min;

[0013] (3) adding the activated microbial strains to the polygonatum treated in step (2) at an inoculum amount of 0.8-1.2% in a sterile operating box, and performing liquid fermentation in a fermentation device at 36-38° C., and monitoring the pH value in the tank in real time during the fermentation process;

[0014] (4) Liquid fermentation endpoint judgment: The liquid fermentation is qualified if both of the following conditions are met:

[0015] A. The pH value of the fermented liquid of Polygonatum sibiricum in the tank decreased by more than 25% within 4 to 6 hours;

[0016] B. Step (3) while adding the activated microbial strain to the polygonatum, dilute the same microbial strain by 10,000 times and place it in MRS solid culture medium, culture it under the same conditions as the liquid fermentation of polygonatum, and determine the number of colonies in the culture medium to be between 80 and 100 by the number of white spots;

[0017] (5) The fermentation liquid that has reached the end point of liquid fermentation is transferred into a constant temperature water bath at 80-90° C. for 5 min to terminate the fermentation, and then placed in a freeze dryer for freeze drying to obtain the fermented polygonatum freeze-dried powder.

[0018] Preferably, in step (1), the steaming conditions are: temperature 60-120° C., first steaming time 10-14 h, second steaming time 5-7 h, and third steaming time 2-4 h.

[0019] Preferably, in step (1), the natural fermentation conditions for each time are: temperature 60-80° C., time 8-12 h.

[0020] Preferably, the microbial strain is P9 plant lactobacillus, the pH value at the end of the liquid fermentation of polygonatum is 3.5-5.0, and the time required is 26-32 hours.

[0021] The activation treatment method of P9 plant lactobacillus is as follows: before starting fermentation, Lactobacillus P9 freeze-dried powder is stored in a -20°C refrigerator, a small amount of bacterial powder is inoculated into MRS broth medium, and activated and cultured in a constant temperature incubator at 37°C and 180r / min for 24 hours. The activated strain is centrifuged to remove the medium, and resuspended in sterile saline to a cell density of 10 5 ~10 7 cfu / mL as a fermentation medium.

[0022] The components of MRS solid culture medium are: peptone 10.0 g / L, beef powder 8.0 g / L, yeast powder 4.0 g / L, glucose 20.0 g / L, sodium acetate 5.0 g / L, dipotassium hydrogen phosphate 2.0 g / L, diammonium hydrogen citrate 2.0 g / L, Tween 80 1.0 g / L, magnesium sulfate 0.2 g / L, manganese sulfate 0.04 g / L, agar 14.0 g / L, pH 6.5±0.2.

[0023] The components of MRS broth medium are: 10.0 g of peptone, 10.0 g of casein peptone, 20.0 g of glucose, 5.0 g of lactic acid, 0.58 g of magnesium sulfate, 0.02 g of citric acid, 0.2 g of potassium chloride, 1.0 g of sodium chloride, 2.0 g of dipotassium hydrogen phosphate, and 0.025 g of neutral red. The balance is supplemented to 1000 mL with water.

[0024] The method provided by the present invention for applying the mixed polygonatum to rice porridge is as follows: adding the fermented polygonatum freeze-dried powder obtained after processing into the rice porridge to obtain the fermented polygonatum rice porridge food, wherein the mass ratio of the fermented polygonatum freeze-dried powder to the rice porridge is (4-6):100.

[0025] The present invention also provides a fermentation device used in the preparation method of the natural fermentation of polygonatum and mixed treatment with lactic acid bacteria, the fermentation device can monitor the pH value in real time, and the fermentation device includes: a drying box, a steam drying box, a fermentation tank, a communicating vessel, a support frame, a conveying device, and a partition, wherein the drying box is connected to the steam drying box as a whole, the drying box and the steam drying box structure are cylindrical structures and hollow inside, the drying box and the steam drying box are separated by a partition in the middle, the support frame is fixed to the bottom of the drying box and the steam drying box, the conveying device is installed inside the drying box and the steam drying box, the conveying device passes through the partition, a communicating vessel is installed on the right side of the steam drying box, a fermentation tank is installed on the right side of the communicating vessel, and the communicating vessel structure is a cylindrical structure.

[0026] Preferably, the drying box includes: a drying box feed inlet, a drying box moisture outlet, and a heating pipe, the drying box feed inlet is arranged on the left side of the drying box, the heating pipe is installed inside the drying box, and the drying box moisture outlet is arranged on the top of the drying box.

[0027] Preferably, the steam drying box comprises: a steam drying box moisture outlet and a steam drying box discharge port, the steam drying box moisture outlet is arranged at the top of the steam drying box, the steam drying box discharge port is arranged on the right side of the steam drying box, and the steam drying box discharge port is connected to the communicating vessel.

[0028] Preferably, the communicating vessel comprises: an opening and closing plate and a discharge port A, wherein the opening and closing plate is installed in the middle of the communicating vessel, and the discharge port A is installed in the lower part of the communicating vessel.

[0029] Preferably, the fermentation tank includes: a fermentation tank cover, a telescopic rod, a support rod, a pH sensor, a display panel, a discharge port B, a slope, and a fermentation tank feed port. The fermentation tank structure is a cylindrical structure. The fermentation tank cover is arranged on the top of the fermentation tank, and a telescopic rod is arranged inside the fermentation tank cover. The lower end of the telescopic rod is connected to the support rod, and the tip of the support rod is provided with a pH sensor. The display panel is arranged on the fermentation tank shell, the bottom of the fermentation tank is provided with a discharge port B, the bottom surface of the fermentation tank is provided with a slope, the fermentation tank feed port is arranged on the upper side surface of the fermentation tank, and the fermentation tank feed port is connected to the communicating vessel.

[0030] Preferably, the partition includes: a fixed plate and a movable plate, the fixed plate is fixed between the drying box and the steam drying box, the fixed plate structure is annular, the movable plate is installed in the fixed plate, the movable plate structure is scissors-shaped, and the movable plate is provided with a notch and a push handle on the top.

[0031] The beneficial effects of the present invention are:

[0032] 1. The present invention subjects polygonatum to three natural fermentations and then uses lactic acid bacteria to continue liquid fermentation. The two different fermentation methods produce an obvious synergistic effect, which can fully retain or increase the flavor and biological activity of the processed product. By optimizing the fermentation process parameters, high-quality polygonatum fermentation products are obtained.

[0033] 2. The present invention mixes the fermented polygonatum with rice porridge to obtain a rice porridge food with excellent taste and flavor and rich nutrition.

[0034] 3. The present invention adopts a specific fermentation device during the liquid fermentation of lactic acid bacteria, which can monitor the pH value of the fermentation liquid in real time and judge the fermentation end point by the pH value, which is simple and easy.

[0035] 4. The fermentation device of the present invention can facilitate the staff to perform pH liquid detection by setting the telescopic rod, and the staff does not need to open the tank all the time to take liquid samples, thus saving labor costs; at the same time, the four pH sensors arranged in the telescopic rod can monitor the pH value of multiple liquid positions, which is more accurate than the monitoring value of a single sensor, and is more conducive to the staff's control of the pH value of the fermentation tank and the fermentation situation in the tank; this equipment can realize normal assembly line production, and has separate material preparation between equipment, which greatly improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the fermentation device of the present invention;

[0037] Figure 2 It is a structural schematic diagram of a steam drying box and a drying box of a fermentation device of the present invention;

[0038] Figure 3 It is a schematic diagram of the structure of the communicating vessel of the fermentation device of the present invention;

[0039] Figure 4 It is a schematic structural diagram of a fermentation tank of a fermentation device of the present invention;

[0040] Figure 5 It is a structural schematic diagram of a partition of a fermentation device of the present invention;

[0041] Figure 6 2. It is a schematic diagram of the structure of the fermentation device of the present invention with the partition opened;

[0042] Figure 7 Schematic diagram of bacterial colonies cultured simultaneously with Polygonatum cyrtonema fermentation in an embodiment of the present invention;

[0043] Figure 8 It is the weight proportion of the components of the four indicators of the fermented polygonatum in the first test of the present invention;

[0044] Fig. 9 It is the change of pH value at different fermentation time in the second experiment of the present invention;

[0045] Fig.10 is the PCA score graph of the electronic nose in Experiment 2 of the present invention;

[0046] Fig.11 This is a graph showing flavor changes of the electronic tongue in Experiment 2 of the present invention;

[0047] Fig.12 It is a Sankey diagram of the sensory evaluation of Experiment 3 of the present invention.

[0048] Description of reference numerals:

[0049] Figures 1 to 6 In: 1. Drying box; 11. Drying box feed port; 12. Drying box moisture outlet; 13. Heating tube; 2. Steam drying box; 21. Steam drying box moisture outlet; 3. Fermentation tank; 31. Fermentation tank cover; 32. Telescopic rod; 33. Support rod; 34. pH sensor; 35. Display panel; 36. Discharge port B; 37. Slope; 38. Fermentation tank feed port; 4. Connecting vessel; 41. Opening and closing plate; 42. Discharge port A; 5. Support frame; 6. Conveying device; 7. Partition plate; 71. Fixed plate; 72. Movable plate. Implementation

[0050] The present invention is further described below in conjunction with embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that the drawings of the present invention are all in very simplified non-precise proportions, which are only used to facilitate and clearly assist in explaining the present invention.

[0051] Example 1

[0052] This embodiment provides a method for preparing polygonatum by natural fermentation and mixed treatment with lactic acid bacteria, which specifically comprises the following steps:

[0053] (1) taking dried polygonatum sibiricum medicinal material and cleaning it, wherein the cleaning includes removing impurities, separating the large and small pieces, and washing; steaming the cleaned polygonatum sibiricum with 60° C. steam, placing the steamed polygonatum sibiricum in a steamer at 60° C. for 12 hours to carry out natural fermentation, and drying the naturally fermented polygonatum sibiricum in the sun, and repeating the above steaming, natural fermentation, and sun drying processes three times; the first steaming time is 10 hours, the second steaming time is 5 hours, and the third steaming time is 2 hours.

[0054] (2) Mix the polygonatum sibiricum treated in step (1) with water in a mass ratio of 1:8, homogenize, add acetic acid and baking soda to adjust the pH value to 7, and then sterilize in a high-temperature autoclave at a sterilization temperature of 120° C. for 30 min.

[0055] (3) Adding activated P9 plant lactobacillus at a 0.8% inoculum amount to the polygonatum sibiricum treated in step (2) in a sterile operating box, and carrying out liquid fermentation in a fermentation device at 36° C., and monitoring the pH value in the tank in real time during the fermentation process.

[0056] (4) Liquid fermentation endpoint judgment: The liquid fermentation is qualified if both of the following conditions are met:

[0057] A. The pH value of the fermented liquid of Polygonatum sibiricum in the tank decreased by more than 25% within 4 to 6 hours;

[0058] B. Step (3) while adding activated P9 plant lactobacillus to polygonatum, taking an appropriate amount of excess microbial strain bacterial liquid and diluting it 10000 times, placing it in MRS solid culture medium, culturing it under the same conditions as the liquid fermentation of polygonatum, and measuring the number of colonies in the culture medium by the number of white spots to be between 80 and 100;

[0059] In this embodiment, the pH value reaching the end point of liquid fermentation of Polygonatum sibiricum is 5.0, and the time required is 26 hours.

[0060] (5) The fermentation liquid that has reached the end point of liquid fermentation is transferred to a constant temperature water bath at 80° C. and placed for 5 minutes to terminate the fermentation, and then placed in a freeze dryer for freeze drying to obtain fermented polygonatum freeze-dried powder.

[0061] The processed fermented polygonatum freeze-dried powder is added into rice porridge to obtain fermented polygonatum rice porridge food, and the mass ratio of the fermented polygonatum freeze-dried powder to the rice porridge is 4:100.

[0062] The activation treatment method of P9 plant lactobacillus is as follows: before starting fermentation, Lactobacillus P9 freeze-dried powder is stored in a -20°C refrigerator, a small amount of bacterial powder is inoculated into MRS broth medium, and activated and cultured in a constant temperature incubator at 37°C and 180r / min for 24 hours. The activated strain is centrifuged to remove the medium, and resuspended in sterile saline to a cell density of 10 5 ~10 7 cfu / mL as a fermentation medium.

[0063] The components of MRS solid culture medium are: peptone 10.0 g / L, beef powder 8.0 g / L, yeast powder 4.0 g / L, glucose 20.0 g / L, sodium acetate 5.0 g / L, dipotassium hydrogen phosphate 2.0 g / L, diammonium hydrogen citrate 2.0 g / L, Tween 80 1.0 g / L, magnesium sulfate 0.2 g / L, manganese sulfate 0.04 g / L, agar 14.0 g / L, pH 6.5±0.2.

[0064] The components of MRS broth medium are: 10.0 g of peptone, 10.0 g of casein peptone, 20.0 g of glucose, 5.0 g of lactic acid, 0.58 g of magnesium sulfate, 0.02 g of citric acid, 0.2 g of potassium chloride, 1.0 g of sodium chloride, 2.0 g of dipotassium hydrogen phosphate, and 0.025 g of neutral red. The balance is supplemented to 1000 mL with water.

[0065] As attached Figures 1 to 6 As shown, the fermentation device used includes: a drying box 1, a steam drying box 2, a fermentation tank 3, a communicating vessel 4, a support frame 5, a conveying device 6, and a partition 7, wherein the drying box 1 is connected to the steam drying box 2 as a whole, the drying box 1 and the steam drying box 2 are cylindrical structures and hollow inside, the drying box 1 and the steam drying box 2 are separated by a partition 7, the support frame 5 is fixed to the bottom of the drying box 1 and the steam drying box 2, the conveying device 6 is installed inside the drying box 1 and the steam drying box 2, the conveying device 6 passes through the partition 7, the communicating vessel 4 is installed on the right side of the steam drying box 2, the fermentation tank 3 is installed on the right side of the communicating vessel 4, and the communicating vessel 4 is a cylindrical structure.

[0066] Specifically, the drying box 1 includes: a drying box feed inlet 11, a drying box moisture outlet 12, and a heating pipe 13. The drying box feed inlet 11 is arranged on the left side of the drying box 1, the heating pipe 13 is installed inside the drying box 1, and the drying box moisture outlet 12 is arranged on the top of the drying box 1.

[0067] Specifically, the steam drying box 2 includes: a steam drying box moisture outlet 21 and a steam drying box discharge port 22. The steam drying box moisture outlet 21 is arranged on the top of the steam drying box 2, and the steam drying box discharge port 22 is arranged on the right side of the steam drying box 2. The steam drying box discharge port 22 is connected to the communicating vessel 4.

[0068] Specifically, the communicating vessel 4 includes: an opening and closing plate 41 and a discharge port A42 . The opening and closing plate 41 is installed in the middle of the communicating vessel, and the discharge port A42 is installed in the lower part of the communicating vessel 4 .

[0069] Specifically, the fermentation tank 3 includes: a fermentation tank cover 31, a telescopic rod 32, a support rod 33, a pH sensor 34, a display panel 35, a discharge port B36, a slope 37, and a fermentation tank feed port 38. The fermentation tank 3 is a cylindrical structure. The fermentation tank cover 31 is arranged on the top of the fermentation tank 3. A telescopic rod 32 is arranged inside the fermentation tank cover 31. The lower end of the telescopic rod 32 is connected to the support rod 33. The tip of the support rod 33 is provided with a pH sensor 34. The display panel 35 is arranged on the outer shell of the fermentation tank 3. A discharge port B36 is opened at the bottom of the fermentation tank 3. A slope 37 is arranged on the bottom surface of the fermentation tank 3. The fermentation tank feed port 38 is arranged on the upper side surface of the fermentation tank 3, and the fermentation tank feed port 38 is connected to the communicating vessel 4.

[0070] Specifically, the partition 7 includes: a fixed plate 71 and a movable plate 72. The fixed plate 71 is fixed between the drying box 1 and the steam drying box 2. The fixed plate structure is annular. The movable plate 72 is installed in the fixed plate 71. The movable plate 72 structure is scissors-shaped, with a push handle on the top. The movable plate is provided with a notch, and the push handle is connected to the movable plate 72.

[0071] Working principle:

[0072] The fermentation device used comprises: a drying box 1, a steam drying box 2, a fermentation tank 3, a connecting vessel 4, a supporting frame 5, a conveying device 6, and a partition 7. During operation, the material to be evaporated is put into the drying box from the feed port 11, the material is placed on the transmission device 6, the heating tube 13 is turned on, and the material is dried. When the material meets the drying requirements, the movable plate 72 in the partition is pulled by the pusher to open the channel, and the material is transported to the drying box 2 by the conveying device 6. The material will be statically evaporated in the drying box 2, and then the opening and closing plate 41 in the connecting vessel 4 is horizontal. The conveying device 6 transports the material to the connecting vessel 4 and enters the fermentation tank feed port 38 through the opening and closing plate 41. The material enters the fermentation tank 3 for fermentation, and the fermentation tank cover 31 is opened to add the required fermentation material. After completion, the fermentation tank cover 31 is closed and the extension of the telescopic rod 32 is controlled by the display panel 35. After reaching the specified liquid depth, the support rod 33 is controlled to unfold. At this time, the pH sensor contacts the liquid for real-time monitoring, and the values ​​of the four sensors are displayed on the display panel 35. When the fermentation is completed, the material is taken out through the discharge port B36 of the fermentation tank 3;

[0073] At the same time, when only the evaporated material needs to be taken out, the evaporated material can be taken out from the discharge port A42 by rotating the opening and closing plate of the communicating vessel 4 clockwise, so that the material can be taken out separately.

[0074] Example 2

[0075] This embodiment provides a method for preparing polygonatum by natural fermentation and mixed treatment with lactic acid bacteria, which specifically comprises the following steps:

[0076] (1) taking dried polygonatum sibiricum medicinal material and cleaning it, wherein the cleaning includes removing impurities, separating the polygonatum by size, and washing it; steaming the cleaned polygonatum sibiricum with 100° C. steaming the steamed polygonatum sibiricum in a steamer at 70° C. for 10 hours to carry out natural fermentation; drying the naturally fermented polygonatum sibiricum in the sun, and repeating the steaming, natural fermentation, and sun drying processes three times; the first steaming time is 12 hours, the second steaming time is 6 hours, and the third steaming time is 3 hours.

[0077] (2) The polygonatum sibiricum treated in step (1) is mixed with water in a mass ratio of 1:10, homogenized, and then acetic acid and baking soda are added to adjust the pH value to 7.5, and then sterilized in a high-temperature sterilizer.

[0078] (3) Adding the Polygonatum sibiricum treated in step (2) to the activated P9 Lactobacillus plantarum at an inoculum rate of 1.0% in a sterile operating box, and carrying out liquid fermentation in a fermentation device at 37° C., and monitoring the pH value in the tank in real time during the fermentation process.

[0079] (4) The method for determining the end point of liquid fermentation is the same as that in Example 1. In this example, the pH value at the end point of liquid fermentation of Polygonatum cyrtonema is 3.5, the time required is 30 h, and the schematic diagram of the cultured bacterial colonies is shown in Figure 7 .

[0080] (5) The fermentation liquid that has reached the end point of liquid fermentation is transferred to a constant temperature water bath at 85° C. and placed for 5 minutes to terminate the fermentation, and then placed in a freeze dryer for freeze drying to obtain fermented polygonatum freeze-dried powder.

[0081] The processed fermented polygonatum freeze-dried powder is added into rice porridge to obtain fermented polygonatum rice porridge food, and the mass ratio of the fermented polygonatum freeze-dried powder to the rice porridge is 5:100.

[0082] The rest is the same as Example 1.

[0083] Example 3

[0084] This embodiment provides a method for preparing Polygonatum sibiricum by natural fermentation and mixed treatment with lactic acid bacteria, which specifically comprises the following steps:

[0085] (1) Take dried Polygonatum sibiricum and clean it, wherein the cleaning includes removing impurities, separating the large and small pieces, and washing; steam the cleaned Polygonatum sibiricum with 120° C. steam, place the steamed Polygonatum sibiricum in a steamer at 80° C. for 8 h to carry out natural fermentation, and dry the Polygonatum sibiricum after natural fermentation, and repeat the steaming, natural fermentation, and sun drying process three times; the first steaming time is 14 h, the second steaming time is 7 h, and the third steaming time is 4 h.

[0086] (2) The polygonatum sibiricum treated in step (1) is mixed with water in a mass ratio of 1:12, homogenized, and then acetic acid and baking soda are added to adjust the pH value to 7.8, and then sterilized in a high-temperature sterilizer.

[0087] (3) Adding activated P9 plant lactobacillus at a 1.2% inoculum amount to the polygonatum sibiricum treated in step (2) in a sterile operating box, and carrying out liquid fermentation in a fermentation device at 38° C., and monitoring the pH value in the tank in real time during the fermentation process.

[0088] (4) The method for determining the end point of liquid fermentation is the same as that in Example 1. In this example, the pH value reaching the end point of liquid fermentation of Polygonatum cyrtonema is 4.06, and the time required is 32 h.

[0089] (5) The fermentation liquid that has reached the end point of liquid fermentation is transferred to a 90° C. constant temperature water bath for 5 minutes to terminate the fermentation, and then placed in a freeze dryer for freeze drying to obtain fermented polygonatum freeze-dried powder.

[0090] The processed fermented polygonatum freeze-dried powder is added into rice porridge to obtain fermented polygonatum rice porridge food, and the mass ratio of the fermented polygonatum freeze-dried powder to the rice porridge is 6:100.

[0091] The rest is the same as Example 1.

[0092] Experiment 1: Single factor experiment on initial pH, material-liquid ratio, inoculation amount and fermentation temperature during the liquid fermentation of lactobacillus

[0093] Experimental group: Example 2 (fermentation broth obtained after terminating the fermentation).

[0094] Comparative Group 1: In step (2), acetic acid and baking soda were added to adjust the pH value to 6.5, and the rest was the same as in Example 2.

[0095] Comparative Group 2: In step (2), acetic acid and baking soda were added to adjust the pH value to 5.5, and the rest was the same as in Example 2.

[0096] Comparative Group 3: In step (2), acetic acid and baking soda were added to adjust the pH value to 4.5, and the rest was the same as in Example 2.

[0097] Comparative group 4: In step (2), Polygonatum sibiricum and water were mixed in a mass ratio of 1:15, and the rest was the same as in Example 2.

[0098] Comparative group 5: In step (2), Polygonatum sibiricum and water were mixed in a mass ratio of 1:20, and the rest was the same as in Example 2.

[0099] Comparative group 6: In step (2), Polygonatum sibiricum and water were mixed in a mass ratio of 1:25, and the rest was the same as in Example 2.

[0100] Comparative Group 7: In step (3), the inoculation amount of activated P9 plant lactobacillus was 0.5%, and the rest was the same as in Example 2.

[0101] Comparative Group 8: In step (3), the inoculation amount of activated P9 plant lactobacillus was 1.5%, and the rest was the same as in Example 2.

[0102] Comparative Group 9: In step (3), the inoculation amount of activated P9 plant lactobacillus was 2.0%, and the rest was the same as in Example 2.

[0103] Comparative group 10: In step (3), the temperature of liquid fermentation was 31° C., and the rest was the same as in Example 2.

[0104] Comparative group 11: In step (3), the temperature of liquid fermentation was 34°C, and the rest was the same as in Example 2.

[0105] Comparative group 12: In step (3), the temperature of liquid fermentation was 40°C, and the rest was the same as in Example 2.

[0106] The inventors of this application have found in their previous exploratory research that the main chemical components of Polygonatum sibiricum are polysaccharides, saponins, phenols, flavonoid compounds, etc., among which polysaccharides and saponins are the most studied. From the current research status, the research on the pharmacological effects and biological activity mechanisms of Polygonatum sibiricum are still focused on lowering blood sugar and anti-fatigue. Based on this, in this experimental example, total polysaccharides, total polyphenols, total saponins and total flavonoids were selected as comprehensive indicators.

[0107] 1. Determination of the content of total polysaccharides, total polyphenols, total saponins and total flavonoids in fermented polygonatum

[0108] (1) Reference substance: Accurately weigh D-anhydrous glucose, gallic acid, ginsenoside Rb1 and rutin, and quantitatively dissolve them in corresponding solvents to prepare the reference substance solution.

[0109] (2) Test sample:

[0110] Total polysaccharides: Weigh 5.5g of the original homogenate of Polygonatum sibiricum to an accuracy of 0.001g, slowly add 20mL of anhydrous ethanol to the sample, shake and mix, then ultrasonically extract for 30 minutes, centrifuge at 4000r / min for 10min, discard the supernatant, wash the insoluble matter with 10mL of 80% ethanol solution and centrifuge for 10min. Transfer the insoluble matter to a beaker, add 50mL of ultrapure water to dissolve, ultrasonicate for 30min, and repeat twice. Cool, filter, transfer the filtrate to a 100mL volumetric flask, wash the residue 2 to 3 times, and make up to volume with ultrapure water to obtain the test solution. Accurately draw 1mL of the test solution, then add 1.0mL of 5% phenol solution, immediately add 5.0mL of concentrated sulfuric acid, let stand for 10min, mix well, put it in a 30℃ water bath and let stand for 20min to cool, use distilled water as a blank control, and measure the absorbance at 490nm.

[0111] Total polyphenols: Weigh 5.5g of the original homogenate of Polygonatum sibiricum, add 15mL of anhydrous ethanol and mix well. Stir the sample in a 60℃ water bath for two hours, centrifuge and take 7.5mL of the supernatant, dilute to a 10mL volumetric flask with 75% ethanol solution, and store in a refrigerator at 4℃ for later use. Transfer 25uL of sample or standard to a 96-well plate in triplicate, use 25uL of 75% ethanol solution as a blank control, then add 125uL of FCR respectively, shake gently and let stand for 10min, finally add 125uL of 7.5% Na2CO3 solution respectively, seal the plate, let stand for 30min, take 200uL and transfer it to a 96-well plate to measure the absorbance at 765nm.

[0112] Total saponins: Weigh 5.5 g of polygonatum sibiricum original homogenate, add 15 mL of anhydrous ethanol and mix well, centrifuge and take 1.0 mL of supernatant, dilute to 10.0 mL with 75% ethanol, shake well, take 0.25 mL of the dilution into a 5 mL EP tube, use a centrifugal concentrator to evaporate the solvent at 50°C, add 0.1 mL of freshly prepared 5% vanillin glacial acetic acid solution, add 0.4 mL of perchloric acid under ice bath conditions, shake well, and develop color in a 60°C water bath for 15 minutes, cool in an ice bath for 15 minutes, add 2.5 mL of glacial acetic acid, mix well, and measure the absorbance at a wavelength of 540 nm.

[0113] Total flavonoids: Weigh 5.5 g of polygonatum sibiricum homogenate, add 15 mL of anhydrous ethanol, shake and mix, then ultrasonically extract for 30 minutes, centrifuge at 4000 r / min for 10 min, take 1.0 mL of the supernatant and put it into a 15 mL centrifuge tube, add 0.5 mL of 5% sodium nitrite solution, react for 6 min, add 0.5 mL of 5% aluminum nitrate, continue to react for 6 min, then add 4.0 mL of 4% sodium hydroxide solution, and finally add 4.0 mL of 60% ethanol solution, mix, and measure the absorbance at 510 nm after 10 min.

[0114] The results are shown in Table 1 below:

[0115] Table 1 Contents of 4 indicators in each group of Test 1

[0116]

[0117] 2. Coefficient of variation-AHP comprehensive weighted scoring method

[0118] The comprehensive score (OD) of total polysaccharides, total polyphenols, total saponins and total flavonoids was used as the final evaluation index.

[0119] (1) Determine weights using the coefficient of variation method

[0120] The coefficient of variation method directly uses the information contained in each indicator to calculate the weight of the indicator. It is an objective weighting method. The basic approach of this method is: in the evaluation indicator system, the greater the difference in the indicator value, the more difficult it is to achieve, and the better it can reflect the gap between the evaluated units.

[0121] The formula for the coefficient of variation of each indicator is Vi = σi / i (i = 1, 2, 3,…, n), where: Vi is the coefficient of variation of the i-th indicator, that is, the standard deviation coefficient; σi is the standard deviation of the i-th indicator; i is the average of the i-th indicator.

[0122] The weights of each indicator are: According to the relevant results, the weight coefficients of total polysaccharides, total polyphenols, total saponins and total flavonoids were calculated by the coefficient of variation method and were 0.1773, 0.4743, 0.2038 and 0.1446 respectively.

[0123] (2) AHP weight determination

[0124] Polysaccharides are the legal quality control components of medicinal polygonatum and its decoction pieces. Polyphenols, saponins and flavonoids are the main bioactive substances of polygonatum. This study found that the content of saponins in fermented polygonatum is high, and the content of polyphenols and flavonoids is equivalent. Therefore, the importance of each component is set as total polysaccharides>total saponins>total polyphenols=total flavonoids. Then, the priority judgment matrix of each indicator is constructed using AHP software. The random consistency ratio (CR) is calculated to be 0.0618 and λmax is 4.1651. When CR < 0.1, it can be determined that the matrix meets the consistency test and the weight coefficient is valid. The arrangement of the four indicator matrices and the results of each parameter are shown in Table 2, and the weight proportion of the components is shown in Figure 8 .

[0125] Table 2 Pairwise comparison priority judgment matrix and weight coefficients of four indicators of fermented polygonatum in experiment 1

[0126] Total OD value Total saponins Total polyphenols Total flavonoids Total polysaccharides Wi Total saponins 1.0000 5.0000 5.0000 0.2000 0.2293 Total polyphenols 0.2000 1.0000 1.0000 0.1250 0.0610 Total flavonoids 0.2000 1.0000 1.0000 0.1250 0.0610 Total polysaccharides 5.0000 8.0000 8.0000 1.0000 0.6487

[0127] (3) Coefficient of variation method-AHP composite weighted calculation weight

[0128] The composite weight of each indicator is: According to the relevant results, the composite weights of total polysaccharides, total polyphenols, total saponins, and total flavonoids were calculated to be 0.5765, 0.1450, 0.2343, and 0.0442, respectively.

[0129] (4) Comprehensive score

[0130] The comprehensive score (OD value) was used as the final reference index, according to the formula OD = (Wcomposite1 × Y1 / Y1(max) + Wcomposite2 × Y2 / Y2(max) + ... + Wcompositen × Yn / Yn(max)) × 100 (n = 1, 2, 3, ... n), where Wcomposite1, Wcomposite2, ..., Wcompositen are the composite weights of the corresponding indicators of each sample, Y1, Y2, ..., Yn are the contents of the corresponding indicators measured in each sample, and Y1(max), Y2(max), ..., Yn(max) are the maximum measured values ​​of each indicator. The results are shown in Table 3.

[0131] Table 3 Total scores of each group in test 1

[0132]

[0133]

[0134] From the above results, it can be seen that the total polysaccharides, total polyphenols, total saponins and total flavonoids, as the index components of fermented polygonatum, have corresponding changes in the content with the changes in different single factor levels during the fermentation process. When the fermented polygonatum obtained by the processing method of the present invention is used, the content of total polysaccharides, total polyphenols, total saponins and total flavonoids is significantly higher than that of other groups.

[0135] Experiment 2: Single factor experiment of different fermentation times during liquid fermentation of lactobacillus

[0136] Experimental group: Take the fermentation time of 30h in Example 2 (fermented Polygonatum sibiricum freeze-dried powder) as an example.

[0137] Comparative groups 13-20: The fermentation times were 0 h, 6 h, 12 h, 18 h, 24 h, 36 h, 48 h, and 36 h, respectively, and the rest were the same as in Example 2.

[0138] 1. pH monitoring at different fermentation times

[0139] The fermentation device of the present invention is used to monitor the pH value of the fermentation liquid in real time, and the pH value changes at different fermentation times are shown in FIG. Fig. 9 , a sudden change in pH occurred at a specific fermentation time, combined with Figure 7 The colony situation of the present invention indicates that the fermentation end point has been reached and the liquid fermentation of the lactic acid bacteria of the present invention has been successful.

[0140] 2. The method for determining the total polysaccharide, total polyphenol and total saponin content in fermented polygonatum is the same as the above test 1. The results are shown in Table 4.

[0141] Table 4 Contents of four indicators in each group at different fermentation times

[0142]

[0143]

[0144] 3. Coefficient of variation-AHP comprehensive weighted scoring method

[0145] The specific method is shown in Experiment 1, and the comprehensive score results of each group are shown in Table 5.

[0146] Table 5 Total scores of each group at different fermentation times

[0147]

[0148] From the above results, it can be seen that the total polysaccharide, total polyphenol, total saponin and total flavonoids, as the index components of fermented polygonatum, have corresponding changes in content with different fermentation times during the fermentation process. When the fermentation time of the present invention is adopted, the content of total polysaccharide, total polyphenol, total saponin and total flavonoids is significantly higher than that of other groups.

[0149] 4. Antioxidant activity test

[0150] (1) Determination of DPPH free radical scavenging ability

[0151] Reagent preparation: ①Trolox standard solution: accurately weigh 25 mg of Trolox, dissolve it in ethanol solution, dilute to 5 ml, mix well, take 50 μL, and dilute to 1 ml to obtain 1000 umol / L Trolox standard stock solution; dilute multiple times to obtain 500 μmol / L, 250 μmol / L, 125 μmol / L, and 62.5 μmol / L Trolox standard solutions.

[0152] ②350μM DPPH working solution: Accurately weigh 6.9mg of DPPH powder into 25mL of ethanol solution, vortex, and place on a rotator for at least 10min to allow DPPH to completely dissolve. Take 2.5mL of the above solution and dilute to 25mL to obtain 350μM DPPH working solution.

[0153] Experimental steps: Add 200 μL of DPPH working solution to each well of a 96-well plate, add 25 μL of Trolox standard solution or sample solution; add only 225 μL of ethanol to the blank well; add 25 μL of ethanol and 200 μL of DPPH working solution to the control well. Gently rotate and tap to mix, seal with plate sealing tape, then react for 6 hours at room temperature in the dark, and measure its absorbance at 517 nm using an automatic microplate reader. The concentrations of the Trolox standard curve are 62.5, 125, 250, 500, and 1000 μmol / L. The results are given as μmol Trolox / g dry weight (μmol Trolox / g BW) with Trolox as the reference standard. Perform the determination three times in parallel and take the average value.

[0154] Result processing: The DPPH scavenging capacity of the sample is expressed by the number of millimoles of Trolox (mgTE / g DW) required to achieve the same elimination rate (TE: Trolox equivalent). The elimination rate is calculated according to the formula:

[0155]

[0156] Where: Asample is the absorbance of the sample solution plus DPPH reagent mixture, Ablank is the absorbance of the blank solvent ethanol solution, and Acontrol is the absorbance of the reference solution plus DPPH reagent mixture.

[0157] (2) Determination of ABTS free radical scavenging ability

[0158] Reagent preparation: ①Trolox standard solution: accurately weigh 2.5 mg of Trolox, dissolve it in 75% ethanol solution, and make up to 10 ml to obtain 1000 umol / L Trolox standard stock solution; dilute it multiple times to obtain 500 μmol / L, 250 μmol / L, 125 μmol / L, 62.5 μmol / L, and 31.25 μmol / L Trolox standard solutions.

[0159] ②140mmol / L K2S2O8 solution: Accurately weigh 0.3785g potassium persulfate powder, dissolve it in ultrapure water, and make up to 10ml.

[0160] ③ABTS stock solution (7mmol / L): Accurately weigh 0.0384g of ABTS powder, dissolve it in 75% ethanol solution, and dilute to 10ml

[0161] ④ Preparation of ABTS working solution: Absorb 88ul of 140mmol / L K2S2O8 solution and 5ml of ABTS stock solution (7mmol / L) and mix well. Let it stand for 12 to 16 hours to prepare ABTS working solution. Then dilute the ABTS working solution with 75% ethanol solution and measure the absorbance at 734nm to make it 0.7±0.02.

[0162] Experimental steps: First, add 180 μL of ABTS working solution to each well of a 96-well plate, then add 20 μL of Trolox standard solution or sample solution of each concentration to the well, incubate at room temperature for 6 minutes and measure at 734 nm. The measurement results are based on Trolox as the reference standard, and the results are μmol Trolox / g dry weight (μmol Trolox / g). Parallel measurements are performed three times and the average value is taken.

[0163] Result processing:

[0164]

[0165] Wherein: Ai is the absorbance of the sample solution plus ABTS working solution, Aj is the absorbance of the sample solution plus 75% ethanol, and A0 is the absorbance of ABTS working solution plus sample solvent.

[0166] (3)Fe 3+ Reducing power determination

[0167] Reagent preparation: ①FeSO4 standard: accurately weigh 100 mg FeSO4 powder, dissolve it in ultrapure water, and make up to 100 ml to obtain 1 mg / ml FeSO4 solution. Dilute it several times to obtain 500 μg / mL, 250 μg / mL, 125 μg / mL, 62.5 μg / mL, and 31.25 μg / mL FeSO4 solutions.

[0168] ②40mmol / L hydrochloric acid solution: absorb 0.1ml of 12N hydrochloric acid solution and dilute to 30ml with water.

[0169] ③20mmol / L ferric chloride solution: Accurately weigh 0.1623g of ferric chloride powder, dissolve it in ultrapure water, and make up to 50ml.

[0170] ④0.3 mol / L sodium acetate buffer solution: Accurately weigh 0.1203 g of sodium acetate trihydrate powder, measure 0.8 ml of glacial acetic acid, mix and dissolve with ultrapure water, and make up to 50 ml.

[0171] ⑤10mmol / L TPTZ solution: Accurately weigh 31.233mg of TPTZ sample, add hydrochloric acid solution to dissolve, dilute to 10ml, and store in a 4℃ refrigerator for later use.

[0172] ⑥0.04mg / ml FRAP working solution: Mix TPTZ solution, ferric chloride solution and sodium acetate buffer solution in a volume ratio of 1:1:10, shake evenly, and prepare before use.

[0173] Experimental steps: 180ul of FRAP working solution preheated to 37℃ was added to a 96-well plate, followed by 20μL of FeSO4 standard solution of each concentration or 10μL of sample solution. After incubation at 37℃ in the dark for 10min, the measurement was performed at 595nm. The measurement results were based on FeSO4 as the reference standard and the results were expressed as mmol FeSO4 / g dry weight (mmg Fe 2+ / g DW). The results were measured three times in parallel and the average value was taken.

[0174] (4) Results

[0175] According to the above experimental steps (1), (2), and (3) and data processing methods, the clearance rates of the three antioxidant activity methods were obtained, see Table 6.

[0176] Table 6 Antioxidant activity of each group at different fermentation times

[0177]

[0178]

[0179] From the above results, it can be seen that as an important indicator of fermented Polygonatum, the activity of the three different methods changes accordingly with different fermentation times during the fermentation process. When the fermentation time of the present invention is adopted, the antioxidant activity of the three different methods is significantly higher than that of other groups.

[0180] 5. Electronic Nose

[0181] Sample processing: 0.5 g of each freeze-dried powder sample of polygonatum sibiricum with different fermentation times was accurately weighed into a 20 ml injection vial, placed in an electronic nose, and analyzed with an incubation temperature of 50°C, a capture temperature of 40°C, and an injection volume of 2 ml.

[0182] Results: According to the above method, the principal component analysis diagram was obtained, see Fig.10 . The results show that the samples before and after fermentation for 30 hours each gathered in a certain area, with obvious distinction. This shows that the flavor of Polygonatum sibiricum changed significantly before and after fermentation for 30 hours. By analyzing the trend of the change in the odor composition in the samples, it was found that the content of the first 14 aromatic and sweet components such as furfuryl alcohol, n-hexanol, and 3-hydroxy-2-butanone increased after fermentation, and reached the highest in Example 2; the last component, nitrobenzene, has unpleasant tastes such as almonds and spicy, which decreased after fermentation and reached the lowest in Example 2.

[0183] The odor changes are shown in Tables 7-1 and 7-2, and the odor components are shown in Table 8.

[0184] Table 7-1 Changes in the smell of Polygonatum odoriferum at different fermentation times

[0185]

[0186]

[0187] Table 7-2 Changes in the smell of Polygonatum odoriferum at different fermentation times

[0188]

[0189]

[0190] Table 8 Odor components

[0191]

[0192] 6. Electronic tongue

[0193] Sample processing: Accurately weigh 2 g of freeze-dried powder of polygonatum sibiricum with different fermentation times, add 100 mL of super-diluted water, take the supernatant after centrifugation, and evenly distribute it in 2 beakers, and analyze it using TS-5000Z taste analysis system (electronic tongue).

[0194] Results: Samples were injected according to the above method, and the results are shown in Table 9. Because other flavors are near the tasteless point, we mainly discuss sourness, astringency, umami, saltiness, and sweetness, see Fig.11. Before fermentation, the acidity value of Polygonatum sibiricum was slightly higher than the tasteless point, showing a slightly sour taste. Before 30 hours of fermentation, the acidity value was lower than the tasteless point, showing a tasteless taste. After 30 hours, the acidity value increased greatly, showing an increase in sourness. Before fermentation, the astringency value of Polygonatum sibiricum was relatively large, and the astringency value decreased after fermentation, showing a weakened astringency, but as the fermentation time was extended to 30 hours, the astringency began to increase. After fermentation, the umami and sweetness increased, but after 30 hours, the umami and sweetness began to decrease to the tasteless point. Compared with before fermentation, the saltiness increased slightly after fermentation, and as the fermentation time increased, the saltiness weakened, reaching a low value at 30 hours, and then slowly increased. Interestingly, these flavors all changed at 30 hours, indicating that the flavor of Polygonatum sibiricum changed significantly before and after 30 hours of fermentation.

[0195] Table 9 Electronic tongue flavor table

[0196]

[0197] Experiment 3: Experiment on different ratios of fermented polygonatum and rice porridge

[0198] Experimental group: the method of Example 2 was adopted.

[0199] Comparative group 21: The mass ratio of fermented polygonatum freeze-dried powder to rice porridge was 2:100, and the rest was the same as Example 2.

[0200] Comparative group 22: The mass ratio of fermented polygonatum freeze-dried powder to rice porridge was 8:100, and the rest was the same as Example 2.

[0201] Comparative group 23: The mass ratio of fermented polygonatum freeze-dried powder to rice porridge was 11:100, and the rest was the same as Example 2.

[0202] Sensory evaluation:

[0203] Five people with food evaluation experience and similar sensory abilities were randomly selected to conduct subjective evaluation of the selected samples from the aspects of color and sweetness by visual inspection, nose smell and mouth tasting; the color evaluation standard was divided into three levels according to the color depth and glossiness, marked with B1 to 3, and B3 was the best; the aroma evaluation standard was divided into three levels according to olfactory perception, marked with O1 to 3, and O3 was the best; the sweetness evaluation standard was divided into three levels according to taste perception, marked with T1 to 3, and T3 was the best. The results are shown in Tables 10 and Fig.12 .

[0204] Table 10 Sensory evaluation table

[0205]

[0206] From the above results, it can be seen that different proportions of fermented polygonatum freeze-dried powder added to rice porridge will affect the color, aroma and sweetness of rice porridge food. When the addition ratio of the present invention is adopted, its sensory evaluation is comprehensively higher than that of other groups.

[0207] It should be noted that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing polygonatum by natural fermentation and mixed treatment with lactic acid bacteria, characterized in that: The preparation method comprises the following steps: (1) taking dried Polygonatum sibiricum medicinal materials, cleaning and selecting them, and then steaming them, naturally fermenting the steamed Polygonatum sibiricum, and then drying them in the sun, and repeating the steaming, natural fermentation, and sun drying processes three times; (2) mixing the polygonatum sibiricum treated in step (1) with water in a mass ratio of 1:(8-12), homogenizing, adding acetic acid and baking soda to adjust the pH value to 7-7.8, and then sterilizing; (3) adding the activated microbial strains to the polygonatum treated in step (2) at an inoculum rate of 0.8-1.2% in a sterile operating box, and performing liquid fermentation in a fermentation device at 36-38° C., and monitoring the pH value in the tank in real time during the fermentation process; (4) Determination of liquid fermentation endpoint: The following two conditions must be met at the same time: A. The pH value of the fermented liquid of Polygonatum sibiricum in the tank decreased by more than 25% within 4 to 6 hours; B. Step (3) while adding the activated microbial strain to the polygonatum, dilute the same microbial strain by 10,000 times and place it in MRS solid culture medium, and culture it under the same conditions as the liquid fermentation of polygonatum, and measure the number of colonies in the culture medium as the number of white spots to be between 80 and 100; (5) The fermentation liquid that has reached the end point of liquid fermentation is transferred into a constant temperature water bath at 80-90° C. to terminate the fermentation, and then placed in a freeze dryer for freeze drying to obtain fermented polygonatum freeze-dried powder; In step (1), the steaming conditions are: temperature 60-120°C, first steaming time 10-14h, second steaming time 5-7h, third steaming time 2-4h; In step (1), the natural fermentation conditions for each time are: temperature 60-80°C, time 8-12h; The microbial strain is P9 plant lactobacillus, the pH value when the liquid fermentation of polygonatum reaches the end point is 3.5-5.0, and the required time is 26-32 hours.

2. An application of the fermented polygonatum freeze-dried powder obtained by the processing method according to claim 1 in rice porridge, characterized in that: The fermented polygonatum freeze-dried powder obtained after processing is added into rice porridge to obtain a fermented polygonatum rice porridge food, wherein the mass ratio of the fermented polygonatum freeze-dried powder to the rice porridge is (4-6):100.

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