Polygonatum sibiricum fresh-keeping method based on lactobacillus fermentation

Abstract

The invention relates to the technical field of food processing and biological preservation, in particular to a rhizoma polygonati preservation method based on lactobacillus fermentation. According to the method, the polygonatum kingianum is pretreated through an optimized lactic acid bacteria fermentation process, so that the fresh-keeping period of the polygonatum kingianum is remarkably prolonged, the polygonatum kingianum can be preserved for 60 hours at 30 DEG C, and the growth of spoilage microorganisms can be effectively inhibited by means of lactic acid generated by fermentation under the condition that no chemical preservative is added, so that the product is free of mildew and peculiar smell, safe and healthy. The method can be used for improving the fresh-keeping performance of the polygonatum sibiricum and enhancing the nutritional value of the polygonatum sibiricum, and has remarkable industrial value. Meanwhile, the method provided by the invention can be used for processing and preserving medicinal and edible foods or traditional Chinese medicine preparations.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing and biological preservation, and particularly to a method for preserving polygonatum sibiricum based on lactic acid bacteria fermentation. Background Art

[0002] Polygonatum sibiricum Delar. ex Redoute is a perennial herb of the family Asparagaceae and the genus Polygonatum. Polygonatum sibiricum has been included in the national catalog of homologous medicines and foods. As a dual-purpose plant of medicine and food, it has been widely used in the field of food R & D. The active ingredients in polygonatum sibiricum include polygonatum polysaccharide, flavonoid, saponin, alkaloid, amino acid, trace element, etc. Its rhizome can be used as medicine, with the effects of nourishing yin and moistening the lung, invigorating the spleen and replenishing qi, and nourishing the kidney and filling essence. At present, the Chinese patent medicines produced with polygonatum sibiricum as the raw material mainly include multiple varieties such as polygonatum sibiricum pills, angelica and polygonatum sibiricum paste, and yiyuan polygonatum sibiricum syrup. Since polygonatum sibiricum has high health care value, various functional products can be developed, including polygonatum sibiricum health wine, polygonatum sibiricum functional yogurt, polygonatum sibiricum health tea, polygonatum sibiricum enzyme oral liquid, polygonatum sibiricum biscuits, polygonatum sibiricum candied fruit, etc. In addition to the related functional foods, polygonatum sibiricum and its active ingredients can also be used in cosmetics, with the effects of anti-aging, antibacterial, whitening, moisturizing, sunscreen, etc.

[0003] However, since polygonatum sibiricum is rich in nutrients such as sugars, proteins, and amino acids, these components are likely to become the culture medium for the growth and reproduction of microorganisms under suitable temperature and humidity conditions, resulting in mildew and rot of polygonatum sibiricum. In addition, polygonatum sibiricum is still a living organism after harvesting, and will carry out physiological activities such as respiration. Over time, quality deterioration phenomena such as degradation of nutrient components, change of color, and softening of texture will occur. In short, the spoilage of polygonatum sibiricum is affected by a variety of factors, including the maturity at the time of harvesting, the post-harvest treatment method, the temperature, humidity, and oxygen content of the storage environment. The storage tolerance of polygonatum sibiricum also varies in different production areas and varieties. Studying the preservation method and spoilage mechanism of polygonatum sibiricum can reduce the loss of polygonatum sibiricum during storage and circulation, improve its commercial value, and reduce the economic loss caused by spoilage, which has important economic significance for polygonatum sibiricum growers, processing enterprises, and distributors.

[0004] The current main preservation methods of Polygonatum sibiricum include: (1) Refrigeration preservation: By suppressing the growth of microorganisms and the activity of enzymes at low temperature (0-4°C), the operation is simple and the cost is low. However, long-term storage is likely to cause water loss, hardening of texture and loss of nutrients in Polygonatum sibiricum; (2) Modified atmosphere preservation: Adjusting the proportion of gases such as oxygen and carbon dioxide to delay the respiration and senescence of Polygonatum sibiricum. However, the investment in equipment is large, and the preservation effect is greatly affected by the gas ratio and packaging materials; (3) Chemical preservation: Using chemical preservatives such as potassium sorbate and sodium benzoate to inhibit the growth of microorganisms, and the preservation effect is remarkable. However, there are potential food safety hazards, which may affect the medicinal value and taste of Polygonatum sibiricum; (4) Irradiation preservation: Using irradiation treatment such as γ-rays to kill microorganisms, and the preservation period is long. However, it may change the chemical composition of Polygonatum sibiricum, produce peculiar smells, and the equipment is expensive and there are radiation safety problems.

[0005] Lactic acid bacteria (LAB) are a group of Gram-positive bacteria, and their typical characteristic is to produce lactic acid as the main metabolic end product through carbohydrate fermentation. Lactic acid bacteria have been used as a starter culture for more than 5,000 years and are widely used in the preparation of traditional fermented foods such as pickles and soy sauce. They make extremely important contributions to the formation process of the flavor of fermented products. From the perspective of food safety, lactic acid bacteria are traditional fermented microorganisms with a long history and are generally recognized as safe (GRAS) strains.

[0006] With the general enhancement of health awareness, the market demand for Chinese medicinal materials with both medicinal and edible uses continues to grow. As a representative medicinal and edible plant, the application scope of Polygonatum sibiricum is constantly expanding. At present, Polygonatum sibiricum has been widely used in many industrial fields such as functional foods, pharmaceutical preparations and personal care products. However, Polygonatum sibiricum is prone to spoilage and difficult to store for a long time. Therefore, it is urgent to explore green and environmentally friendly preservation methods. Therefore, exploring the fermentation preservation method of Polygonatum sibiricum by lactic acid bacteria has important economic significance. Summary of the Invention

[0007] The purpose of the present invention is to provide a preservation method of Polygonatum sibiricum based on lactic acid bacteria fermentation to solve the problems existing in the above-mentioned prior art. The method provided by the present invention can effectively extend the preservation period of Polygonatum sibiricum.

[0008] To achieve the above purpose, the present invention provides the following scheme:

[0009] The present invention provides a preservation method of Polygonatum sibiricum based on lactic acid bacteria fermentation, including the following steps:

[0010] Mix Polygonatum sibiricum and a culture solution, inoculate lactic acid bacteria, and carry out fermentation culture.

[0011] Preferably, the inoculation amount of the lactic acid bacteria is 0.05% of the mass of the culture solution;

[0012] The lactic acid bacteria is Lactobacillus plantarum.

[0013] Preferably, the mass-volume ratio of the polygonatum sibiricum and the culture solution is 20 g: 200 mL.

[0014] Preferably, the culture solution comprises components with the following concentrations:

[0015] 3 wt% glucose and 0.9 wt% sodium chloride.

[0016] Preferably, the time of the fermentation culture is 60 h and the temperature is 30 °C.

[0017] Preferably, the culture solution is a sterilized culture solution;

[0018] The sterilization conditions are: sterilization at 121 °C for 20 min.

[0019] Preferably, after the fermentation culture, a preservation step is further included.

[0020] Preferably, the temperature of the preservation is 30 °C.

[0021] The present invention provides an application of the above method in inhibiting the spoilage and deterioration of polygonatum sibiricum.

[0022] The present invention provides an application of the above method in prolonging the shelf life of polygonatum sibiricum.

[0023] The present invention discloses the following technical effects:

[0024] The present invention pre-treats polygonatum sibiricum by using an optimized lactic acid bacteria fermentation process. The antibacterial substances (such as lactic acid, bacteriocin, etc.) produced by the metabolism of lactic acid bacteria inhibit pathogenic bacteria and molds, and the advantage of preserving polygonatum sibiricum is obvious. At the same time, the pH value is adjusted and the oxidation degree is reduced; the nutritional components of polygonatum sibiricum can be retained or improved during the fermentation process, and flavor substances are increased, having the dual effects of preservation and quality improvement; and the lactic acid bacteria are probiotics with high safety, meeting the development trend of green foods and natural medicines, and having broad application prospects. The results of specific embodiments of the present invention show that: the method provided by the present invention not only significantly prolongs the shelf life of polygonatum sibiricum, enabling it to be preserved for 60 h under the condition of 30 °C, but also can effectively inhibit the growth of spoilage microorganisms by the lactic acid produced by fermentation without adding any chemical preservatives, ensuring that the product has no mildew, no peculiar smell, and is safe and healthy. The present invention can be applied to improving the preservation performance of polygonatum sibiricum and enhancing its nutritional value, having significant industrial value. At the same time, the method provided by the present invention can be used for the processing and preservation of medicine and food homology, foods or traditional Chinese medicine preparations. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 This is the standard curve graph of the lactic acid mass concentration and absorbance of the present invention: In the graph, the horizontal axis represents the lactic acid mass concentration (unit: g·L -1 ), and the vertical axis represents the absorbance;

[0027] Figure 2 This is the result of the influence of the inoculation amount of lactic acid bacteria on fermentation of the present invention: In the graph, the vertical axis is the lactic acid concentration, and the horizontal axis is the inoculation amount;

[0028] Figure 3 This is the result of the influence of the glucose addition amount on fermentation of the present invention: In the graph, the left vertical axis represents the pH value, the right vertical axis represents the lactic acid concentration, and the horizontal axis is the glucose addition amount;

[0029] Figure 4 This is the result of the influence of temperature on fermentation of the present invention: In the graph, the left vertical axis represents the pH value, the right vertical axis represents the lactic acid concentration, and the horizontal axis is the temperature;

[0030] Figure 5 This is the result of the influence of time on fermentation of the present invention: In the graph, the left vertical axis represents the pH value, the right vertical axis represents the lactic acid concentration, and the horizontal axis is the fermentation time;

[0031] Figure 6 This is the comparison data of the mold counts of the unfermented polygonatum sibiricum and the fermented polygonatum sibiricum at different time points (0 - 60h) of the present invention: In the graph, the vertical axis represents the mold count, and the horizontal axis represents the time. Detailed Embodiments

[0032] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0035] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the description of the present invention will be apparent to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0036] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0037] For the sources of the reagents used in this invention, see Table 1 below.

[0038] Table 1 Reagent Sources

[0039]

[0040] Example 1 Pretreatment of Polygonatum sibiricum Redoute of the Present Invention

[0041] (1) Material pretreatment: Weigh 20 g of fresh, non-rotten and non-moldy Polygonatum sibiricum Redoute, wash, dry, and wipe with 75% (V / V) alcohol for standby.

[0042] (2) Prepare the culture medium: Measure 200 mL of distilled water into a fermentation flask, add 0.9 wt% sodium chloride and an appropriate amount of glucose thereto, and mix well.

[0043] (3) Sterilization treatment: Put the fermentation flask containing the culture medium, 1000 μL and 200 μL pipette tips into a high-pressure steam sterilizer, and sterilize at 121 °C for 20 min.

[0044] (4) Filling the tank: Put the treated Polygonatum sibiricum Redoute into the sterilized culture medium; the mass-volume ratio of Polygonatum sibiricum Redoute to the culture medium is 20 g: 200 mL.

[0045] (5) Inoculation: Add Lactobacillus plantarum powder to the above-mentioned fermentation flask.

[0046] (6) Sealing the tank: Seal the fermentation flask with a lid.

[0047] (7) Fermentation: First, preheat the incubator to the set temperature, then number the sealed fermentation bottles and place them in the incubator in an orderly manner, maintaining a constant temperature throughout the process.

[0048] Example 2 Basic conditions of the present invention

[0049] The basic conditions were obtained by referring to the literature and preliminary experiments. The obtained basic conditions are that the inoculation amount of Lactobacillus plantarum is 0.05 wt%, glucose is 3 wt%, sodium chloride is 0.9 wt%, the fermentation temperature is 30 °C, and the fermentation time is 48 h.

[0050] Example 3 Single-factor experimental design of the present invention

[0051] (1) Effect of the inoculation amount of lactic acid bacteria on fermentation: Adjust the experimental conditions for the fermentation of Polygonatum sibiricum by lactic acid bacteria according to the basic conditions. Under the condition that the addition amounts of other raw materials (glucose 3 wt%, sodium chloride 0.9 wt%, and the balance of water) and the experimental conditions remain unchanged (fermentation temperature 30 °C and fermentation time 48 h), the mass fraction ratios of lactic acid bacteria are set to 0%, 0.0125%, 0.025%, 0.05%, and 0.075% for experiments, that is, the inoculation amounts of lactic acid bacteria are 0%, 0.0125%, 0.025%, 0.05%, and 0.075% of the mass of the culture solution. Discuss the effect of the inoculation amount on fermentation based on the pH value and lactic acid concentration. From Figure 2 it can be seen that as the inoculation amount increases, the lactic acid concentration shows a trend of first increasing and then stabilizing, indicating that the inoculation amount has an important regulatory effect on the lactic acid fermentation efficiency. The effect is best when the inoculation amount is between 0.025% and 0.075%.

[0052] (2) Effect of the addition amount of glucose on fermentation: Adjust the experimental conditions for the fermentation of Polygonatum sibiricum by lactic acid bacteria according to the experimental steps of "(1) Effect of the inoculation amount of lactic acid bacteria on fermentation". Under the condition that the addition amounts of other raw materials (sodium chloride 0.9 wt% and the balance of water), experimental conditions (fermentation temperature 30 °C and fermentation time 48 h), and inoculation amount (0.05%) remain unchanged, the mass fraction ratios of glucose are set to 1%, 2%, 3%, 4%, and 5% for experiments. Discuss the effect of the inoculation amount on fermentation based on the pH value and lactic acid concentration. As can be seen from Figure 3, as the addition amount of glucose increases, the pH value gradually decreases, while the lactic acid concentration shows an upward trend, indicating that the addition amount of glucose has a significant effect on the production of lactic acid. The lactic acid concentration stabilizes under the condition that the mass fraction ratio of glucose is 3% - 5%.

[0053] (3) Influence of temperature on fermentation: Adjust the experimental conditions for the fermentation of polygonatum sibiricum by lactic acid bacteria according to the experimental steps of "(1) Influence of inoculation amount of lactic acid bacteria on fermentation". Without changing the addition amounts of other raw materials (3 wt% glucose, 0.9 wt% sodium chloride, and the balance of water), experimental conditions (fermentation time of 48 h), and inoculation amount (0.05%), conduct experiments at temperatures of 20 °C, 25 °C, 30 °C, 35 °C, and 40 °C respectively, and discuss the influence of inoculation amount on fermentation based on the pH value and lactic acid concentration. As can be seen from Figure 4 it that at 30 °C, the lactic acid concentration is relatively high, while too high or too low temperature will lead to a decrease in lactic acid production, indicating that temperature is one of the key factors affecting lactic acid fermentation.

[0054] (4) Influence of time on fermentation: Adjust the experimental conditions for the fermentation of polygonatum sibiricum by lactic acid bacteria according to the experimental steps of "(1) Influence of inoculation amount of lactic acid bacteria on fermentation". Without changing the addition amounts of other raw materials (3 wt% glucose, 0.9 wt% sodium chloride, and the balance of water), experimental conditions (fermentation temperature of 30 °C), and inoculation amount (0.05%), conduct experiments at times of 0 h, 12 h, 24 h, 36 h, 48 h, and 60 h respectively, and discuss the influence of inoculation amount on fermentation based on the pH value and lactic acid concentration. As can be seen from Figure 5 it that the lactic acid concentration gradually increases with the prolongation of fermentation time and reaches a peak at about 48 hours, and then tends to be stable, indicating that fermentation time is an important parameter for optimizing lactic acid production efficiency.

[0055] Example 4 Orthogonal experimental design of the present invention

[0056] Based on the results of single-factor experiments, select four key parameters: inoculation amount of bacteria, glucose concentration, fermentation temperature, and time. Each parameter is set at three optimized levels, and L9(3 4 ) orthogonal experimental design is used for process optimization. The specific implementation plan is shown in Table 2. Judge the influence of lactic acid bacteria fermentation on polygonatum sibiricum according to the data obtained from the four factors and three levels as shown in Table 3, so as to obtain the best experimental conditions.

[0057] Table 2 Factor-level table of orthogonal experiment

[0058] Horizontal Bacterial inoculation amount / wt% Glucose amount / wt% Temperature / °C Time / h 1 0.025 3 30 36 2 0.05 4 35 48 3 0.075 5 40 60

[0059] Table 3 Factor-level table of orthogonal experiment

[0060] Number Bacterial inoculation amount / wt% Glucose amount / wt% Temperature / °C Time / h pH 1 0.025 3 30 36 3.65 2 0.025 4 40 48 3.68 3 0.025 5 35 60 3.39 4 0.05 3 40 60 3.43 5 0.05 4 35 36 3.62 6 0.05 5 30 48 3.22 7 0.075 3 35 48 3.47 8 0.075 4 30 60 3.29 9 0.075 5 40 36 3.77 Mean 1 3.573 3.517 3.387 3.680 Mean 2 3.423 3.530 3.627 3.457 Mean 3 3.510 3.460 3.493 3.370 Range 0.150 0.070 0.240 0.310

[0061] Evaluate the pH values of each experimental group through range analysis, and determine that the best fermentation parameter combination is: inoculation amount of bacteria 0.05 wt%; glucose addition amount 5 wt%; temperature 30 °C; time 60 h.

[0062] Example 5 Method for Determining the Physicochemical Properties of the Invention

[0063] (1) Determination of pH: Take 10 mL of the fermentation broth, centrifuge at 4000 rpm for 10 min, collect the supernatant, and directly measure it using a pH meter.

[0064] (2) Determination of lactic acid concentration: Prepare standard series solutions of lactic acid at 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, and 5.0 g / L respectively. Take 0.1 mL of each standard solution and react it with 4 mL of 0.2 wt% ferric chloride solution. Shake well to form the ferric(III) lactate complex. Measure the absorbance at a wavelength of 390 nm using a UV-visible spectrophotometer, establish a standard curve for quantitative analysis of the lactic acid content in the sample. The standard curve is as shown in Figure 1 shown. The formula of the standard curve is: Y = 0.1487x - 0.0263, R 2 = 0.993.

[0065] Take 0.1 mL of the fermentation broth sample, add 4 mL of 0.2 wt% ferric chloride solution and mix well. Then, process it according to the standard curve measurement method, and calculate the lactic acid content based on the standard curve.

[0066] Example 6 Method for Judging the Freshness Preservation of Polygonatum sibiricum of the Invention

[0067] After fermentation optimization, ferment Polygonatum sibiricum under the optimized conditions, and then conduct a freshness preservation experiment on the fermented Polygonatum sibiricum and the unfermented Polygonatum sibiricum. Regularly observe and record the odor, color, and moldy situation of Polygonatum sibiricum. The specific steps are as follows:

[0068] (1) Prepare fresh Polygonatum sibiricum, wipe the surface with 75% (V / V) alcohol for disinfection, peel and slice it to obtain Polygonatum sibiricum slices;

[0069] (2) Prepare a culture solution with distilled water, sodium chloride, and glucose. The concentration of glucose in this culture solution is 3 wt%, and the concentration of sodium chloride is 0.9 wt%;

[0070] (3) Sterilize the fermentation broth and other materials at 121 °C for 20 min;

[0071] (4) Put the processed Polygonatum sibiricum into the sterilized culture solution; the mass-volume ratio of Polygonatum sibiricum to the culture solution is 20 g: 200 mL.

[0072] (5) Add the Lactobacillus plantarum powder into the above fermentation flask. The inoculation amount of the Lactobacillus plantarum powder is 0.05% of the mass of the culture solution;

[0073] (6) Seal the fermentation flask with a lid;

[0074] (7) Preheat the incubator to 30°C first, then number the sealed fermentation bottles and place them in the incubator in an orderly manner for fermentation for 60 h, maintaining a constant temperature throughout the process.

[0075] (8) Drain the fermented polygonatum slices, package them and then carry out preservation (storage). The temperature for preservation (storage) is 30°C.

[0076] Regard the appearance of peculiar smell or the appearance of mildew spots or stickiness on the surface of polygonatum as the end point of the shelf life. The results are as Figure 6 shown. It can be directly seen from Figure 6 the change and difference of the number of mildew spots of fermented polygonatum and unfermented polygonatum over time. Under the condition of 30°C, unfermented polygonatum can only be stored for 24 h, and the preservation time of fermented polygonatum can be extended to 60 h.

[0077] At the same time, investigate the pH value and lactic acid concentration of polygonatum after fermentation. The investigation results show that the pH value is 3.2 - 3.7 and the lactic acid concentration is 3.3 - 4.8.

[0078] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A fresh-keeping method for polygonatum sibiricum based on lactic acid bacteria fermentation, characterized in that, It includes the following steps: After mixing polygonatum sibiricum and a culture solution, inoculate lactic acid bacteria and conduct fermentation culture.

2. The polygonatum preservation method according to claim 1, wherein The inoculation amount of the lactic acid bacteria is 0.05% of the mass of the culture solution; The lactic acid bacteria is lactobacillus plantarum.

3. The polygonatum fresh-keeping method according to claim 1, characterized in that The mass-volume ratio of the polygonatum sibiricum to the culture solution is 20 g: 200 mL.

4. The polygonatum preservation method according to claim 1, wherein The culture solution includes components with the following concentrations: 3 wt% glucose and 0.9 wt% sodium chloride.

5. The polygonatum fresh-keeping method according to claim 1, characterized in that, The time of the fermentation culture is 60 h and the temperature is 30 °C.

6. The polygonatum preservation method according to claim 1, wherein The culture solution is a sterilized culture solution; The sterilization conditions are: sterilize at 121 °C for 20 min.

7. The polygonatum fresh-keeping method according to claim 1, characterized in that, After the fermentation culture, it further includes a preservation step.

8. The polygonatum odoratum preservation method according to claim 1, wherein, The temperature of the preservation is 30 °C.

9. Application of the method according to any one of claims 1-8 in inhibiting the spoilage and deterioration of polygonatum sibiricum.

10. Application of the method according to any one of claims 1-8 in extending the shelf life of polygonatum sibiricum.

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