Preparation method of rapidly fermented natural preservative and natural preservative

Abstract

The invention relates to the technical field of fermentation, in particular to a preparation method of a rapidly-fermented natural preservative and the natural preservative. The preparation method comprises the following steps: injecting whey into a fermentation tank, adjusting the pH value to 6.0-7.0, sterilizing for 15-20 minutes to obtain sterilized whey, inoculating a seed solution containing lactic acid bacteria into the sterilized whey, and fermenting at 37-40 DEG C for 24-48 hours to obtain whey fermentation liquor; centrifuging the whey fermentation liquor, filtering supernate obtained by centrifuging, and drying filtrate obtained by filtering, so as to obtain the natural preservative. According to the natural preservative prepared by the method, not only is the production cost effectively reduced, but also the fermentation period can be greatly shortened, so that the production efficiency of the natural fermentation product prepared by fermentation is improved, rapid fermentation is realized, and the natural fermentation product can play a better preservative role when being applied to food as a preservative.

Description

Technical Field

[0001] This application relates to the field of fermentation technology, and particularly to a preparation method of a natural preservative for rapid fermentation and the natural preservative. Background Art

[0002] Fermentation technology plays an important role in the food industry. By converting lactic acid bacteria into natural products with antibacterial and flavoring functions, it provides a new development direction for food processing. With the improvement of consumers' awareness of food safety and health, the demand for natural preservatives is increasing day by day, which puts higher requirements on the technological innovation of the food industry. Natural preservatives can not only replace existing chemical preservatives and reduce potential threats to human health, but also provide important support for the progress of food processing technology. Currently, the common methods for preparing natural preservatives include lactic acid bacteria fermentation method and milk fermentation method. The lactic acid bacteria fermentation method produces substances such as organic acids and antibacterial peptides through the fermentation of specific strains under suitable conditions, involving multiple steps such as strain activation, medium preparation, fermentation condition control, and post-separation and purification. The milk fermentation method uses milk as the raw material and generates the target product through the fermentation of lactic acid bacteria or other microorganisms. The specific operation includes adding colonies and medium into milk, adding carbon source and nitrogen source and stirring well, and then fermenting at 30-35°C for 65-75 hours. Both methods can effectively prepare natural preservatives, but the operation process is complex and the fermentation cycle is long. However, in the prior art, whether it is the lactic acid bacteria fermentation method or the milk fermentation method, there are problems of cumbersome operation and long production cycle, which seriously restricts the large-scale application of natural preservatives. In addition, the milk fermentation method is also limited by high raw material costs and narrow application fields. Summary of the Invention

[0003] In order to reduce production costs while achieving rapid fermentation, shorten the fermentation cycle, improve the production efficiency of natural fermentation products obtained by fermentation, and ensure that the natural fermentation products can play a better anti-corrosion role when applied as preservatives in food, a preparation method of a natural preservative for rapid fermentation and the natural preservative are provided.

[0004] In the first aspect, the present application provides a method for preparing a natural preservative that can be fermented quickly, comprising the following steps: injecting whey into a fermentation tank, adjusting the pH value to 6.0-7.0, sterilizing for 15-20 minutes to obtain sterilized whey, and then inoculating the seed liquid containing lactic acid bacteria into the sterilized whey, and fermenting at a temperature of 37-40°C for 24h-48h to obtain a whey fermentation liquid; then centrifuging the whey fermentation liquid, filtering the supernatant obtained by centrifugation, and drying the filtrate obtained by filtration to obtain a natural preservative. By adopting this technical solution, the processing and fermentation of whey are exquisitely optimized to a highly synergistic and efficient environment. Specifically, the pH value is accurately adjusted to a near-neutral condition of 6.0-7.0, which effectively avoids the potential damage to the activity of the strain by extreme acid-base conditions and ensures the high vitality of the strain, which is the primary prerequisite for successful fermentation. At the same time, with the sterilization treatment for 15-20 minutes, the miscellaneous bacteria in the whey are completely removed, and the interference of external microorganisms is avoided. In a near-neutral sterilization environment with a pH value of 6.0-7.0, the temperature is controlled in a precise temperature-controlled fermentation environment of 37-40°C, so that the lactic acid bacteria can continue to maintain the high vitality of the strain, thereby ensuring the rapid reproduction and efficient metabolism of the lactic acid bacteria, so that it can quickly produce antibacterial substances. Compared with the existing lactic acid bacteria fermentation technology, the lactic acid bacteria of the present application can produce a larger number of antibacterial substances per unit time. It is worth noting that under this specific pH value and temperature combination, the antiseptic effect of the obtained natural preservatives is better, and the fermentation time is accurately controlled within 24-48 hours. This precise time control not only greatly shortens the production cycle and realizes efficient production, but also helps it to efficiently metabolize and produce antibacterial substances, while reducing the accumulation of by-products such as organic acids, and avoiding the possibility of long-term fermentation. Producing some pigments or odorous substances, these substances will affect the appearance and smell of the fermented products.

[0005] These three conditions - pH value accurately adjusted to near-neutral conditions of 6.0-7.0, precise temperature control of the fermentation environment at 37-40°C, and fermentation time accurately controlled within 24-48 hours - are closely related and indispensable. Only when these conditions are met at the same time can fermentation be achieved quickly, the accumulation of by-products such as organic acids can be reduced, and the production of some pigments or odorous substances that may be produced by long-term fermentation can be avoided, and finally a natural preservative with good preservative effect can be obtained for use in food.

[0006] In addition, whey generally refers to the by-product generated during the process of producing cheese from milk, which is a green, semi-transparent liquid separated after milk coagulates into curd. As a by-product of cheese production, whey is extremely easy to obtain and has a wide range of sources. It is produced in large quantities due to the huge global cheese production. Its production relies on the widespread supply of milk, achieving efficient utilization of resources. At the same time, processing whey into high-value-added products not only reduces waste emissions but also meets health needs, demonstrating remarkable sustainability. Preferably, the seed liquid containing lactic acid bacteria is prepared by the following method: Inoculate lactic acid bacteria strains into the first medium for activation. After 18h - 24h of activation, the activated strains are obtained. Then inoculate the activated strains into the second medium and culture for 12h - 16h to obtain the seed liquid containing lactic acid bacteria.

[0007] By adopting the above technical solution, first inoculate lactic acid bacteria strains into the first medium for activation, and the activation time is 18h - 24h. During this process, the lactic acid bacteria strains can quickly recover their activity and improve their metabolic ability, thus laying a foundation for the subsequent fermentation process. Then, inoculate the activated strains into the second medium and culture for 12h - 16h to further promote the proliferation of lactic acid bacteria and the accumulation of metabolites. This step-by-step culture method not only improves the activity and concentration of lactic acid bacteria but also effectively shortens the preparation period of the seed liquid, ensuring the efficiency of the fermentation process. Finally, it helps to improve the production efficiency and quality of natural preservatives, and when used in food, it can play a better anti-corrosion role. Preferably, the lactic acid bacteria strains are one or more of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus casei.

[0008] By adopting the above technical solution, select Lactobacillus acidophilus, Lactobacillus plantarum, or Lactobacillus casei as the fermentation strains. These strains can quickly achieve fermentation within 24 - 48 hours after being mixed and fermented with whey under the precise temperature control fermentation environment of 37 - 40°C after sterilization treatment under nearly neutral conditions with a pH value of 6.0 - 7.0, reduce the accumulation of by-products such as organic acids, can efficiently metabolize the nutrients in whey, and produce metabolites with antibacterial activity, and finally obtain a natural preservative with a good anti-corrosion effect when applied to food. Preferably, the activated strains are inoculated into the second medium for culture at an inoculation amount of 1 - 5% (v / v) by volume, and the seed liquid containing lactic acid bacteria is inoculated into the sterilized whey at an inoculation amount of 2 - 10% (v / v) by volume.

[0009] By adopting the above technical solutions, specifically, by inoculating the activated strain into the first culture medium at an inoculation amount of 1-5% (v / v), the effective activation of the strain can be achieved within a short time, improving the vitality and metabolic efficiency of the strain. Subsequently, the activated strain is inoculated into the second culture medium at an inoculation amount of 2-10% (v / v) to prepare the seed liquid. This process not only ensures the initial concentration of the strain in the fermentation stage but also promotes the rapid proliferation and metabolism of lactic acid bacteria, thereby promoting the rapid fermentation of whey within 24-48 hours under the precise temperature control fermentation environment at 37-40°C after sterilization treatment under nearly neutral conditions with a pH value of 6.0-7.0, significantly shortening the fermentation cycle, and the final natural preservative has no peculiar smell. Finally, this method can effectively simplify the operation process, reduce the production cost, and at the same time ensure that the prepared natural preservative has no accumulation of many by-products such as organic acids, and the natural preservative applied to food has a good anti-corrosion effect. Preferably, both the first culture medium and the second culture medium are MRS culture medium. By adopting the above technical solutions, selecting MRS culture medium as the first culture medium and the second culture medium can provide rich nutrients for the growth of lactic acid bacteria. MRS culture medium contains carbon sources, nitrogen sources and various trace elements required for the growth of lactic acid bacteria, which is beneficial to the rapid activation and proliferation of lactic acid bacteria strains. During the preparation of the seed liquid, using MRS culture medium can significantly improve the activity and metabolic efficiency of lactic acid bacteria, thus ensuring the stability and high efficiency of the subsequent fermentation process. This optimized culture condition shortens the time for strain activation and cultivation. When in contact with whey, it can promote the rapid and complete fermentation of whey within 24-48 hours under the precise temperature control fermentation environment at 37-40°C after sterilization treatment under nearly neutral conditions with a pH value of 6.0-7.0, and the accumulation of by-products such as organic acids. Using the obtained natural preservative in food can play a better anti-corrosion role, reduce the possibility of food spoilage, and improve the food safety of food.

[0010] Preferably, it is characterized in that the activation temperature of the activation process is set at 35-38°C.

[0011] By adopting the above technical solution, the activation temperature of the sterilized whey is set at 35 - 38 °C. This temperature range is close to the optimal growth temperature of lactic acid bacteria and can effectively promote the metabolic activity of lactic acid bacteria. Within this temperature range, lactic acid bacteria can rapidly proliferate and secrete metabolites such as organic acids and antibacterial peptides, ensuring that the finally prepared natural preservative can play a better anti-corrosion role when used in food. Preferably, the sterilization temperature of the sterilized whey is 115 - 121 °C. By adopting the above technical solution, setting the sterilization temperature at 115 - 121 °C can effectively kill the miscellaneous bacteria in the whey and ensure the purity of the fermentation process. Thus, the sterilized whey can be mixed and fermented with the seed liquid containing lactic acid bacteria, avoiding the generation of some pigments or off-flavor substances that may affect the appearance and smell of the fermentation products, and ensuring that the finally prepared natural preservative can play a better anti-corrosion role when used in food. Preferably, the centrifugation rate of the whey fermentation broth is 4000 - 6000 rpm, and the centrifugation time is 10 min - 15 min. By adopting the above technical solution, the whey fermentation broth is placed under high-speed centrifugation conditions, and after centrifugation for a specific duration of 10 to 15 minutes, the insoluble substances with larger molecular weights are precipitated to the bottom due to gravity, while the supernatant containing the target anti-corrosion components is enriched. This treatment method significantly reduces the interference of impurities such as insoluble protein aggregates, lactic acid bacteria cells and their fragmented fragments, pigments, and off-flavor substances, thus ensuring that the final product can play a better anti-corrosion role when used in food. Preferably, the filtration process uses an ultrafiltration membrane with a molecular weight cut-off of 10 - 30 kDa. By adopting the above technical solution, the supernatant is ultrafiltered through an ultrafiltration membrane with a molecular weight cut-off of 10 - 30 kDa, which can effectively remove the small molecule impurities and residual whey protein fragments in it. This process is based on the selective filtration characteristics of the ultrafiltration membrane. When the molecular weight cut-off is 10 kDa, the small molecule substances with a molecular weight lower than 10 kDa are separated out. When the molecular weight cut-off is 30 kDa, the small molecule substances with a molecular weight lower than 10 kDa are separated out. Since the whey in this application is sterilized under near-neutral conditions with a pH value of 6.0 - 7.0, and after fermentation with the seed liquid containing lactic acid bacteria in a precisely temperature-controlled fermentation environment at 37 - 40 °C, the fermentation time is precisely controlled within 24 - 48 hours. The accumulation of by-products such as organic acids in the lactic acid fermentation broth, and the impurities such as pigments or off-flavor substances are less, and the functional components with antibacterial activity are retained. Therefore, the purity of the supernatant after ultrafiltration treatment with an ultrafiltration membrane with a molecular weight cut-off of 10 - 30 kDa is relatively high, further improving the quality of the natural preservative. Subsequently, the filtrate is dried, and the finally obtained natural preservative not only maintains good antibacterial performance but also can play a better anti-corrosion role when used in food. In the second aspect, this application provides a natural preservative. The mesh number of the natural preservative is 20 - 80 mesh, and the natural preservative is prepared by a preparation method of a rapidly fermented natural preservative.

[0012] By adopting the above technical solution, a natural preservative is provided. Its preparation method uses whey as the raw material and obtains the natural preservative through steps such as sterilization, lactic acid bacteria fermentation, centrifugation, filtration, and drying. This method significantly simplifies the preparation process of the natural preservative, shortens the production cycle, reduces the cost, and the finally obtained natural preservative has a better anti-corrosion effect when used in food. The specific effects include: 1. By optimizing the fermentation conditions and controlling the fermentation time within 24h - 48h, the preparation cycle is significantly shortened. 2. By adopting centrifugation and ultrafiltration technologies, the target product is effectively separated, and the purification efficiency and product quality are improved.

[0013] In summary, the present application includes at least one of the following beneficial technical effects: 1. By injecting whey into the fermentation tank and adjusting the pH value to 6.0 - 7.0, after sterilization treatment, inoculating the seed liquid containing lactic acid bacteria, and fermenting at 37 - 40°C for 24h - 48h, the main fermentation process can be completed. Compared with the existing lactic acid bacteria fermentation method, which has multiple complex steps such as multi-step activation of strains (24h - 30h), preparation of culture medium (12h - 18h), control of fermentation conditions (70h - 80h), and later separation and purification (15min - 25min), this method significantly simplifies the operation process. At the same time, the fermentation cycle is shortened to 24h - 48h, greatly improving the production efficiency. With the shortening of the processing time, the energy consumption is further reduced, saving energy and protecting the environment; 2. Using whey as the raw material, it is extremely easy to obtain and has a wide source. Processing whey into high-value-added products not only reduces waste emissions, meets the health needs, but also demonstrates significant sustainability; 3. Using lactic acid bacteria fermentation to generate natural antibacterial substances such as organic acids and antibacterial peptides, these substances avoid the potential health risks that may be brought by chemical preservatives while ensuring the anti-corrosion effect. Through the sterilization treatment under the near-neutral condition with a pH value of 6.0 - 7.0 in the present application, the precise temperature control fermentation environment at 37 - 40°C, the fermentation condition of mixing with whey and fermenting within 24 - 48 hours, and precisely controlling the fermentation temperature and inoculation amount, the safety and effectiveness of the natural preservative are further improved, better meeting the needs of consumers for healthy food. Specific embodiments Examples

[0014] The raw materials are as follows: Lactobacillus casei, manufacturer: Qingdao Nuosen Biotechnology Co., Ltd., product specification: 100 billion CFU / g; Whey powder, manufacturer: Suqian Meinen Biotechnology Co., Ltd., product model: rqdbf1031; MRS culture medium, manufacturer: Beijing Solarbio Science & Technology Co., Ltd., model: M8540 - 2150g.

[0015] Example 1 A natural preservative with a mesh number of 20 - 80 meshes, and preferably 80 - mesh natural preservative in this example.

[0016] The natural preservative is prepared by the following method: Take 3 g of Lactobacillus casei strain and inoculate it into 100 g of the first medium for activation. Control the activation at 37 °C for 16 h, and then transfer it to a 1000 - mL volumetric flask. Add distilled water to make the volumetric flask up to 1000 mL to obtain the activated strain. Inoculate the activated strain into 100 g of the second medium according to an inoculation amount of 5% (v / v). Control the culture temperature at 37 °C and culture for 12 h to obtain a seed liquid containing lactic acid bacteria, and then transfer it to a 1000 - mL volumetric flask and make it up to 1000 mL with distilled water. Among them, both the first medium and the second medium are MRS medium.

[0017] Take 150 g of whey powder and pour it into a 1 - L fermenter. Add distilled water to make it up to 1 L, then add acetic acid to adjust the pH value to 6.0, and perform sterilization treatment at 115 °C. After sterilization for 15 min, cool it to 37 °C to obtain sterilized whey; Inoculate the seed liquid containing lactic acid bacteria into the fermenter according to an inoculation amount of 10% (v / v) and mix - ferment it with the sterilized whey. Maintain the fermentation at 37 °C for 48 h to obtain whey fermentation broth; Put the fermented whey fermentation broth into a centrifuge and centrifuge at 4000 rpm for 15 minutes to collect the supernatant; Ultra - filter the supernatant through an ultra - filtration membrane with a molecular weight cut - off of 30 kDa to collect the filtrate; Dry the filtrate for 15 seconds under the conditions that the inlet air temperature is 120 °C, the outlet air temperature is 150 °C, and the rotation speed of the atomization disk of the spray dryer is 12000 rpm, and then crush it through a crusher to obtain an 80 - mesh natural preservative.

[0018] Example 2 The difference between Example 2 and Example 1 lies in the process parameters of activation and centrifugation. Specifically: the culture time of the activated strain is 16 h, the inoculation amount of the activated strain is 1% (v / v), the inoculation amount of the seed liquid containing lactic acid bacteria is 2% (v / v), the fermentation time of the whey fermentation broth is 24 h, and the centrifugation speed is 6000 rpm.

[0019] Example 3 The difference between Example 3 and Example 1 lies in the process parameters of activation and centrifugation. Specifically: the culture time of the activated strain is 18 h, the sterilization time of the sterilized whey is 20 min, the fermentation time of the whey fermentation broth is 34 h, and the centrifugation speed is 6000 rpm.

[0020] Example 4 The difference between Example 4 and Example 3 lies in the different fermentation process parameters. Specifically, the pH value of the whey sterilization treatment is 7.0, the sterilization temperature is 121 °C, the fermentation temperature of the whey fermentation broth is 40 °C, and the fermentation time of the whey fermentation broth is 37 h.

[0021] Example 5 The difference between Example 5 and Example 4 lies in the different fermentation process parameters. Specifically, the pH value of the whey sterilization treatment is 6.5, and the fermentation temperature of the whey fermentation broth is 37 °C.

[0022] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 5 is that the pH value is 5.0.

[0023] Comparative Example 2 The difference between Comparative Example 2 and Example 5 is that the pH value is 8.0.

[0024] Comparative Example 3 The difference between Comparative Example 3 and Example 5 is that the fermentation temperature is 30 °C.

[0025] Comparative Example 4 The difference between Comparative Example 4 and Example 5 is that the fermentation temperature is 45 °C.

[0026] Comparative Example 5 The difference between Comparative Example 5 and Example 5 is that: 3 g of Lactobacillus casei strain was inoculated into 100 g of seed medium for cultivation, made up to 1000 mL with distilled water, and cultured at a high liquid level for 36 h; the cultured Lactobacillus casei was inoculated into 100 g of fermentation medium at an inoculation amount of 10% (v / v), then 150 g of whey powder was added, made up to 1000 mL with distilled water and mixed evenly, then the pH was controlled above 6.0 by adding alkali at a rotation speed of 100 rpm, and then anaerobically mixed and fermented at 30 °C for 96 h; after fermentation, the fermentation broth was sterilized at 100 °C for 1 h, and finally spray-dried at an inlet temperature of 165 °C and an outlet temperature of 90 °C to obtain a natural preservative.

[0027] Experimental Example Experimental Example 1 The natural preservatives obtained in Examples 1-5 and Comparative Examples 1-5 were taken. 1 mg of each natural preservative was dissolved in 1 mL of aqueous solution to obtain 10 different natural preservative solutions. Then, the 10 different natural preservative solutions were poured into 10 portions of orange juice to obtain 10 orange juice samples containing different natural preservative solutions. The orange juice without adding the natural preservative solution was used as the blank control group. The blank control group and the orange juice samples were both placed in a sealed environment for 30 days, and these 10 samples were detected separately within these 30 days. The beverages were determined with reference to GB 7101-2022 "National Food Safety Standard Beverages".

[0028] This detection standard refers to GB 4789.2-2010 for detecting the total number of colonies. The standard or specified values require: n = 5, c = 2, m = 10000, M = 100000; among 5 test samples, it is allowed that at most 2 samples have the total number of colonies exceeding 10000 CFU / g (or CFU / mL). If more than 2 samples have the total number of colonies exceeding 10000 CFU / g (or CFU / mL), but the total number of colonies of all samples does not exceed 100000 CFU / g (or CFU / mL), the product is still regarded as qualified; if the total number of colonies of any sample exceeds 100000 CFU / g (or CFU / mL), the product is regarded as unqualified.

[0029] Refer to GB 4789.3-2010 for detecting coliforms. The standard or specified values require: n = 5, c = 2, m = 10, M = 100; among 5 test samples, it is allowed that at most 2 samples have the number of coliforms exceeding 10 MPN / g (or MPN / mL). If more than 2 samples have the number of coliforms exceeding 10 MPN / g (or MPN / mL), but the number of coliforms of all samples does not exceed 100 MPN / g (or MPN / mL), the product is still regarded as qualified; if the number of coliforms of any sample exceeds 100 MPN / g (or MPN / mL), the product is regarded as unqualified.

[0030] Refer to GB 4789.4-2010 for detecting Salmonella. The standard or specified values require: n = 5, c = 0, m = 0; it is qualified if no Salmonella is detected in all samples, and it is unqualified as long as Salmonella is detected in one sample.

[0031] Refer to GB 4789.10-2010 for detecting Staphylococcus aureus. The standard or specified values require: n = 5, c = 0, m = 0; it is qualified if no Staphylococcus aureus is detected in all samples, and it is unqualified as long as Staphylococcus aureus is detected in one sample.

[0032] Detect molds and yeasts with reference to GB 4789.15-2016. The standard or specified value requirement for molds and yeasts is ≤ 20 CFU / g; when the detected molds and yeasts exceed 20 CFU / g, it is unqualified. Conduct a food safety test every 3 days. When the test value of any one of the above bacteria in the blank control group, Examples 1-5 and Comparative Examples 1-5 is unqualified, this sample group is recorded as unqualified, and the corresponding number of days is recorded; the qualified samples continue to be tested. When the test days exceed 30 days and no unqualified phenomenon still appears, it is recorded as the number of days greater than 30.

[0033] The above experiments are all carried out 5 times, and the average value is calculated.

[0034] Test results: The test results of various bacteria in the blank control, Examples 1-5, and Comparative Examples 1-5 are shown in Table 1; Table 1 Experimental data of the blank control, Examples 1-5, and Comparative Examples 1-5 From the above Table 1, combined with Examples 1-5 and Comparative Examples 1-5, it can be seen that: The blank control group without adding the natural preservative solution showed unqualified items on the 3rd day of the experiment, indicating that the orange juice added with the natural preservative solution is difficult to maintain stable quality for a long time without the protection of the preservative; Example 1 showed unqualified phenomena on the 24th day. Compared with the blank control group, it was unqualified 21 days later, indicating that the natural preservative prepared in Example 1 can effectively inhibit the growth of various bacteria in orange juice and effectively extend the shelf life of orange juice by at least 21 days; Example 2 showed unqualified phenomena on the 21st day. Compared with the blank control group, it was unqualified 18 days later, indicating that the natural preservative prepared in Example 2 can effectively inhibit the growth of various bacteria in orange juice and effectively extend the shelf life of orange juice by at least 18 days; Both Example 3 and Example 4 showed unqualified phenomena on the 27th day. Compared with the blank control group, it was unqualified 24 days later, indicating that the anti-corrosion effects of the natural preservatives prepared in Example 3 and Example 4 in orange juice are similar, both can effectively inhibit the growth of various bacteria, and effectively extend the shelf life of orange juice by at least 24 days; No unqualified items were found in Example 5 within 30 days of the experiment, indicating that the natural preservative prepared in Example 5 has the best anti-corrosion effect on orange juice and extends the shelf life of orange juice by at least 30 days; On the contrary, it can be seen that the number of unqualified days in Comparative Examples 1-5 does not exceed 15 days, which is generally lower than that in the Example group; among them, compared with Example 5, Comparative Example 1 was unqualified on the 6th day, and Comparative Example 2 was unqualified on the 12th day, indicating that when the pH value of Example 5 is 6.5, the anti-corrosion effect of the natural preservative prepared on orange juice is much better than that of the natural preservative prepared when the pH value is 5 or 8 on orange juice; Comparative Example 3 was unqualified on the 9th day, and Comparative Example 4 was unqualified on the 15th day, indicating that when the fermentation temperature of Example 5 is 37°C, the anti-corrosion effect of the natural preservative prepared on orange juice is much better than that of the natural preservative prepared when the fermentation temperature is 30°C or 45°C on orange juice; Comparative Example 5 was unqualified on the 15th day, indicating that the anti-corrosion effect of the natural preservative prepared according to the process of Example 5 in beverages is far inferior to that of the natural preservative prepared according to the production process in Example 5.

[0035] Experimental Example 2 Taking the anti-corrosion effect of the natural preservative on bread as an example, the anti-corrosion effect of the natural preservative prepared by the present invention is verified by adding the natural preservative to the challenging experiment of bread. Refer to GB 7099-2015 "National Food Safety Standard Pastries, Bread" to measure bread, and refer to GB 4789.15-2016 to detect molds and yeasts. The standard or declared value requirement for molds and yeasts is ≤150 CFU / g. The specific experimental process is as follows: 1. When kneading the dough, take the natural preservatives prepared in Examples 1-5 and Comparative Examples 1-5, which are 0.5% of the flour weight, and add them to the flour respectively, and make bread according to the same method. At the same time, use the dough without adding natural preservative as the blank control group, and other experimental conditions are the same.

[0036] 2. After fermentation and baking, slice the two groups of bread, and then place the bread slices in an incubator at 37°C and a humidity of 55% for 10 days.

[0037] Perform food safety tests every 1 day. When the number of molds in the bread of the blank control group, Examples 1-5 and Comparative Examples 1-5 exceeds 150 CFU / g within 5 days, it is recorded as unqualified; the qualified samples continue to be tested. When the test days exceed 10 days, if the number of molds detected still does not exceed 150 CFU / g, it is recorded as qualified.

[0038] The above experiments are all carried out 5 times, and the average value is calculated.

[0039] Results: The mold tests of the blank control, Examples 1-5, and Comparative Examples 1-5 are shown in Table 2.

[0040] Table 2 Number of days when non-conformities occurred in the blank control group, Examples 1-5, and Comparative Examples 1-5 As can be seen from Table 2, the bread in the blank control group without adding natural preservatives and Comparative Examples 1-5 were all recorded as non-conforming after being cultured in an incubator at 37°C and a humidity of 55%. However, in Examples 1-5, no mold exceeded the standard was detected within 10 days of the experiment, and the results were all qualified. This shows that the natural preservatives prepared in Examples 1-5 have good anti-corrosion effects in bread and can extend the shelf life of bread by at least 10 days in an environment of 37°C and a humidity of 55%.

[0041] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A preparation method of a fast-fermenting natural preservative, characterized in that, It includes the following steps: Inject whey into a fermentation tank, adjust the pH value to 6.0 - 7.0, perform sterilization treatment for 15 - 20 min to obtain sterilized whey, then inoculate the seed liquid containing lactic acid bacteria into the sterilized whey, and ferment at a temperature of 37 - 40 °C for 24 h - 48 h to obtain a whey fermentation broth; then perform centrifugation on the whey fermentation broth, filter the supernatant obtained by centrifugation, and dry the filtrate obtained by filtration to obtain a natural preservative.

2. The preparation method of a natural preservative for rapid fermentation according to claim 1, characterized in that, The seed liquid containing lactic acid bacteria is prepared by the following method: Take a lactic acid bacteria strain and inoculate it in a first culture medium for activation. After activation for 18 h - 24 h, an activated strain is obtained; inoculate the activated strain in a second culture medium and culture for 12 h - 16 h to obtain the seed liquid containing lactic acid bacteria.

3. The preparation method of a natural preservative for rapid fermentation according to claim 2, characterized in that, The lactic acid bacteria strain is one or more of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus casei.

4. The preparation method of a natural preservative for rapid fermentation according to claim 2, characterized in that, The activated strain is inoculated in the second culture medium for culture at an inoculation amount of 1 - 5% (v / v) by volume, and the seed liquid containing lactic acid bacteria is inoculated in the sterilized whey at an inoculation amount of 2 - 10% (v / v) by volume.

5. According to the method for preparing a rapidly fermented natural preservative described in claim 2, both the first culture medium and the second culture medium are MRS culture media.

6. The preparation method of a natural preservative for rapid fermentation according to claim 2, characterized in that, The activation temperature during the activation process is set at 35 - 38 °C.

7. The preparation method of a natural preservative for rapid fermentation according to claim 1, characterized in that, The sterilization temperature of the sterilized whey is 115 - 121 °C.

8. The preparation method of a rapidly fermented natural preservative according to claim 1, characterized in that, The centrifugation rate of the whey fermentation broth is 4000 - 6000 rpm, and the centrifugation time is 10 min - 15 min.

9. The preparation method of a natural preservative for rapid fermentation according to claim 1, characterized in that, The filtration process uses an ultrafiltration membrane with a molecular weight cut-off of 10 - 30 kDa.

10. A natural preservative, characterized in that, The mesh number of the natural preservative is 20 - 80 mesh; the natural preservative is prepared by the method for a rapidly fermented natural preservative according to any one of claims 1 - 9.

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