Fermentation method of fermented lycium ruthenicum juice with high oxidation resistance, product and application

Abstract

The invention provides a fermentation method of fermented lycium ruthenicum juice with high oxidation resistance, a product and application, and relates to the technical field of food. The fermentation method of the fermented lycium ruthenicum juice with high oxidation resistance comprises the following steps: (1) activating a strain to obtain an activated strain with the viable count of 1.0 * 10 < 9 >-2.0 * 10 < 9 > CFU / mL; the strain is lactobacillus plantarum GH-6; and (2) inoculating the activated strain into the raw material lycium ruthenicum juice according to the inoculation amount of 2.5-3.5%, and performing fermentation treatment at 34-40 DEG C for 3-5 hours to obtain the fermented lycium ruthenicum juice. The preparation of the fermented lycium ruthenicum juice with high oxidation resistance and high sensory evaluation is realized by controlling lactobacillus fermentation process conditions; the obtained fermented lycium ruthenicum juice is high in lactic acid bacterium activity, and the viable count and the stability are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of food technology, specifically relating to the fermentation method, product, and application of fermented black goji berry juice with high antioxidant properties. Background Technology

[0002] Black goji berries (Lycium ruthenicum Murr.) are perennial woody plants belonging to the Solanaceae family (Solanaceae Juss.) and the Lycium genus (Lycium L.). They are named for their dark purple fruit when ripe. Black goji berries are rich in polysaccharides, anthocyanins, polyphenols, minerals, and amino acids, among other bioactive components, and possess anti-inflammatory, anti-aging, anti-radiation, and anti-tumor effects. In the food industry, lactic acid bacteria are widely used in both food processing and biotechnology. The active enzymes, organic acids, and bacteriocins produced by lactic acid bacteria during fermentation have excellent bioactive functions. Lactic acid bacteria can lower cholesterol, regulate intestinal flora, reduce inflammation, and enhance immunity. Studies have shown that lactic acid fermentation not only solves the problems of short shelf life and poor storage of fruits but also provides unique flavors and textures to food.

[0003] Through lactic acid bacteria fermentation, the functional substances in fruits can be effectively preserved. During fermentation, sugars are the primary energy source for lactic acid bacteria, which utilize these sugars and metabolize them into organic acids. These organic acids are the source of the flavor in fermented beverages, and the presence of a large amount of organic acids makes the fermented juice acidic, inhibiting the growth of bacteria that cause fruit spoilage.

[0004] To improve the taste of fruit beverages, Yu Xiaoqing et al., in their article "Process Optimization of Hawthorn Leaf and Guava Leaf Compound Fermentation Beverage," pointed out that a compound beverage can be prepared by lactic acid fermentation of common hawthorn leaves and guava leaves. Using viable bacteria count as the evaluation index, they determined the optimal process for the hawthorn leaf and guava leaf compound beverage through a combination of single-factor and response surface methodology experiments: an initial inoculum of 5% and fermentation at 35℃ for 44 hours. Under these conditions, the resulting compound beverage is refreshing and palatable. However, this fermentation process requires a high inoculum of lactic acid bacteria and a prolonged fermentation time.

[0005] Chinese invention patent CN115474661A discloses a raw liquid for fermented beverage made from black goji berries with lactic acid bacteria and its preparation method, including the following steps: (1) preparing black goji berry slurry using pectinase and cellulase; (2) preparing lactic acid bacteria into a bacterial suspension and mixing it evenly with the goji berry slurry obtained in step (1), fermenting it in a dark and sealed environment to obtain a crude fermented goji berry liquid; wherein the lactic acid bacteria are Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus fermentum, and the Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus fermentum are prepared according to a viable count of 10 6 -10 8 CFU / mL, 107 -10 9 CFU / mL, 10 6 -10 9 The lactic acid bacteria were added at a ratio of CFU / mL, and the total amount added was 1×10⁻⁶. 7 -1×10 9 CFU / mL; (3) Preparation of black goji berry lactic acid bacteria fermented beverage: The crude fermented liquid of goji berries is filtered, and a protective agent is added to the supernatant and then placed in an opaque container, sealed, and sterilized at 95℃ for 15 min to obtain black goji berry lactic acid bacteria fermented beverage; the total amount of the protective agent added is at least 0.2% by mass-volume ratio, and the mass ratio of hesperidin, trehalose, and vanillin in the protective agent is 2:2:1. This method improves the overall taste of the original liquid of black goji berry lactic acid bacteria fermented beverage by deoxygenating and treating the black goji berry pulp with a protective agent, and increases the content of anthocyanins and proanthocyanidins; that is, the key technology of this invention is deoxygenation and the addition of a protective agent, and there is no record of the effect of lactic acid bacteria fermentation process on the sensory and antioxidant effects of the beverage.

[0006] Chinese invention patent CN120304512A discloses a lactic acid bacteria that produces high levels of γ-aminobutyric acid (GABA) and its application in fermented wolfberry and other fruit juice products. The method involves using *Lactobacillus plantarum* LP-GB 01-21 to ferment a compound fruit juice containing wolfberry pulp at 35℃-37℃ for 8-12 hours to obtain a fermented broth. The invention clearly states that if other *Lactobacillus plantarum* strains are used instead of this specific strain for fermentation, the GABA content and antioxidant activity in the product significantly decrease. Therefore, the strain specificity of *Lactobacillus plantarum* has a decisive influence on the sensory quality and antioxidant efficacy of fermented wolfberry fruit juice.

[0007] In existing technologies, improving the sensory evaluation, viable count of lactic acid bacteria, and antioxidant properties of fruit juice often requires the addition of deoxidizers or protectants, resulting in prolonged fermentation times. This not only increases processing time but also hinders the development of green, additive-free fruit juice due to the addition of deoxidizers and protectants as additives. Therefore, there is a need for an improved fermentation process that can enhance the sensory evaluation, viable count, and antioxidant properties of lactic acid bacteria fermented fruit juice without the use of additives. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by providing a fermentation method, product, and application for fermented black goji berry juice with high antioxidant properties. Without using additives, fermented black goji berry juice with high antioxidant properties and high sensory evaluation can be prepared by controlling the lactic acid bacteria fermentation process conditions. The resulting fermented black goji berry juice has high lactic acid bacteria activity, significantly improving the number of live bacteria and the stability of live bacteria.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: First, this invention provides a fermentation method for fermented black goji berry juice with high antioxidant properties, comprising the following steps: (1) Activation of the strain to obtain an activated strain; the strain is Lactobacillus plantarum GH-6; (2) Inoculate the activated strain into the raw black goji berry juice at an inoculation rate of 2.5%-3.5% and ferment for 3-5 hours to obtain fermented black goji berry juice.

[0010] Preferably, in step (1), the Lactobacillus plantarum GH-6 has the accession number CGMCC No. 24276, is deposited at the China General Microbiological Culture Collection Center, and is named Lactobacillus plantarum. Lactobacillus plants .

[0011] Preferably, the number of viable bacteria in the activated strain described in step (1) is 1.0 × 10⁻⁶. 9 -2.0×10 9 CFU / mL.

[0012] Preferably, the activation step in step (1) is as follows: streaking the bacterial strain onto MRS solid medium under aseptic conditions, anaerobic culture at 37°C for 48 h, picking single colonies for reactivation, then inoculating single colonies again into MRS liquid medium (volume 5 mL / 15 mL), and culturing at 37°C for 16 h to obtain primary seed culture; subsequently, 0.5 mL is added to new MRS liquid medium (volume 20 mL / 50 mL), and culturing at 37°C for 16 h to obtain secondary seed culture; centrifuging at 5000×g and 4°C for 15 min, discarding the supernatant, washing the bacterial cells twice with sterile physiological saline, then resuspending the bacterial cells in sterile physiological saline to adjust the viable count to 1.0×10⁻⁶. 9 -2.0×10 9 CFU / mL was used to obtain the fermentation seed liquid, which is the activated strain.

[0013] Preferably, in step (2), the preparation method of the raw material black goji berry juice is as follows: S1. Remove bad fruits and impurities from black goji berries; wash them clean, mix them with water, soak them, and juice them to obtain black goji berry pulp. S2. Centrifugal filtration: Centrifuge the black goji berry pulp and take the supernatant A; combine the residues and mix them with water for ultrasonic treatment, then centrifuge again to take the supernatant B; combine supernatant A and supernatant B to obtain a supernatant mixture. S3. Sterilization: Sterilize the supernatant mixture in a water bath and cool it to room temperature for later use.

[0014] More preferably, in step S1, the solid-liquid ratio of the soaking is 1g:10-30mL.

[0015] More preferably, in step S1, the soaking process has a solid-liquid ratio of 1g:20mL.

[0016] More preferably, in step S1, the soaking time is 30-90 minutes; even more preferably, in step S1, the soaking time is 60 minutes.

[0017] More preferably, in step S2, the centrifugation is specifically performed at 4000-6000 rpm for 4-8 minutes; more preferably, in step S2, the centrifugation is specifically performed at 5000 rpm for 5 minutes.

[0018] More preferably, in step S2, the solid-liquid ratio of the residue to water is 1g:10-30mL when mixing with water; even more preferably, in step S2, the solid-liquid ratio of the residue to water is 1g:20mL when mixing with water.

[0019] More preferably, in step S2, the ultrasonic treatment time is 10-30 min; even more preferably, in step S2, the ultrasonic treatment time is 20 min.

[0020] More preferably, in step S2, the power of the ultrasonic treatment is 200-400W and the temperature is 30-50℃; even more preferably, in step S2, the power of the ultrasonic treatment is 300W and the temperature is 45±5℃.

[0021] More preferably, in step S2, the supernatant mixture is concentrated until the solid-liquid ratio of black goji berries to liquid is 1g:10-30mL.

[0022] More preferably, in step S2, the supernatant mixture is concentrated until the solid-liquid ratio of black goji berries to liquid is 1g:20mL.

[0023] More preferably, in step S3, the water bath sterilization specifically involves: heating the supernatant mixture in a water bath until the temperature reaches 80-90°C, and continuing this process for 10-30 minutes.

[0024] More preferably, in step S3, the water bath sterilization specifically involves: heating the supernatant mixture in a water bath until the temperature reaches 85°C, and continuing this process for 30 minutes.

[0025] Preferably, in step (2), the inoculation amount is 3%. Preferably, in step (2), the inoculation amount is based on the raw material black goji berry juice, and the unit is v / v.

[0026] In this invention, the inoculation amount is 2.5%-3.5%. Within the range of 2.5%-3.5% described in this invention, the technical effects described in this invention can be achieved. It is not limited to any point value or any range between any two points, namely 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, and 3.5%.

[0027] Preferably, in step (2), the fermentation treatment time is 4 hours.

[0028] Preferably, in step (2), the temperature of the fermentation treatment is 34-40℃; more preferably, in step (2), the temperature of the fermentation treatment is 34-37℃; even more preferably, in step (2), the temperature of the fermentation treatment is 37℃.

[0029] Then, the present invention provides a fermented black goji berry juice, which is prepared by the above-described fermentation method.

[0030] Finally, this invention provides the application of the above-described fermentation method in the preparation of beverages with high sensory evaluation, free radical scavenging function and antioxidant properties.

[0031] Preferably, the beverage used in the application is a fermented beverage or a nutritional supplement beverage.

[0032] Compared with the prior art, the present invention has the following beneficial effects: 1. In the fermentation method of the present invention, by using specific types of lactic acid bacteria, inoculation amount and fermentation time, the color, texture, aroma, flavor and overall acceptability of fermented black goji berry juice are significantly improved, and the sensory score is significantly improved; moreover, the fermented black goji berry juice is rich in strains, and the number of strains is stably preserved.

[0033] 2. The fermented black goji berry juice obtained by the fermentation method of the present invention has high antioxidant properties, and its antioxidant properties are significantly improved compared with the fermented black goji berry juice obtained by conventional methods. Detailed Implementation

[0034] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0035] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention were obtained through conventional commercial channels. Raw materials from different manufacturers do not have a significant impact on the efficacy.

[0037] Preservation materials: Lactobacillus plantarum GH-6 ( Lactobacillus plantarum ); Accession number: CGMCC No. 24276; Date of deposit: January 10, 2022; Preservation institution: China General Microbiological Culture Collection Center, China Committee on the Preservation and Management of Microbial Culture Collections; Address: No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0038] Basic Example 1 In a specific embodiment of the present invention, the activated bacterial strain used is *Lactobacillus plantarum* GH-6, containing a viable count of 2.0 × 10⁻⁶. 9 CFU / mL.

[0039] The activation steps were as follows: Under aseptic conditions, the cultures were streaked onto MRS solid medium and anaerobically cultured at 37°C for 48 hours. Single colonies were picked and reactivated for one generation. Then, single colonies were again inoculated into MRS liquid medium (5 mL / 15 mL) and cultured at 37°C for 16 hours to obtain the primary seed culture. Subsequently, 0.5 mL of the secondary seed culture was obtained by adding it to fresh MRS liquid medium (20 mL / 50 mL) and culturing at 37°C for another 16 hours. The culture was then centrifuged at 5000 × g at 4°C for 15 minutes, the supernatant was discarded, and the cells were washed twice with sterile physiological saline. The cells were then resuspended in sterile physiological saline and adjusted to a viable count of 2.0 × 10⁻⁶. 9 CFU / mL was used to obtain the fermentation seed liquid, which is the activated strain.

[0040] Example 1 The fermentation method for fermented black goji berry juice with high antioxidant properties is as follows: (1) The bacterial strain (Lactobacillus plantarum GH-6) was activated to obtain the activated bacterial strain (basic example 1). (2) The activated strain was inoculated into the raw black goji berry juice at an inoculation rate of 3% (v / v) and fermented at 37°C for 4 hours to obtain fermented black goji berry juice. The preparation method of raw material black goji berry juice is as follows: S1. Remove bad fruits and impurities from black goji berries; after cleaning, mix with water at a solid-liquid ratio of 1g:20mL, soak at room temperature for 60 minutes, and juice to obtain black goji berry pulp. S2. Centrifugal filtration: Centrifuge the black goji berry slurry at 5000 rpm for 5 min and collect the supernatant A; combine the residues and mix with water at a solid-liquid ratio of 1 g: 20 mL, sonicate at 45±5℃ and 300W for 20 min, centrifuge again at 5000 rpm for 5 min and collect the supernatant B; combine supernatant A and supernatant B, concentrate until the solid-liquid ratio of black goji berries to liquid is 1 g: 20 mL, and obtain the supernatant mixture; S3. Sterilization: After filling the supernatant mixture, sterilize it in a water bath. When the temperature of the supernatant mixture reaches 85°C, continue heating for 30 minutes, and then cool it to room temperature.

[0041] Example 2 The fermentation method for fermented black goji berry juice with high antioxidant properties is as follows: (1) The bacterial strain (Lactobacillus plantarum GH-6) was activated to obtain the activated bacterial strain (basic example 1). (2) The activated strain was inoculated into the raw black goji berry juice at an inoculation rate of 2.5%, and fermented at 40°C for 5 hours to obtain fermented black goji berry juice; The preparation method of raw material black goji berry juice is as follows: S1. Remove damaged and impurities from black goji berries; after cleaning, mix with water at a solid-liquid ratio of 1g:10mL, soak at room temperature for 90 minutes, and juice to obtain black goji berry pulp. S2. Centrifugal filtration: Centrifuge the black goji berry slurry at 4000 rpm for 8 min and collect the supernatant A; combine the residues and mix with water at a solid-liquid ratio of 1 g: 30 mL, sonicate at 45±5℃ and 300W for 10 min, centrifuge again at 4000 rpm for 8 min and collect the supernatant B; combine supernatant A and supernatant B, concentrate until the solid-liquid ratio of black goji berries to liquid is 1 g: 20 mL, and obtain the supernatant mixture; S3. Sterilization: After filling the supernatant mixture, sterilize it in a water bath. When the temperature of the supernatant mixture reaches 80°C, continue heating for 30 minutes, and then cool it to room temperature.

[0042] Example 3 The fermentation method for fermented black goji berry juice with high antioxidant properties is as follows: (1) The bacterial strain (Lactobacillus plantarum GH-6) was activated to obtain the activated bacterial strain (basic example 1). (2) The activated strain was inoculated into the raw black goji berry juice at an inoculation rate of 3.5%, and fermented at 34°C for 3 hours to obtain fermented black goji berry juice; The preparation method of raw material black goji berry juice is as follows: S1. Remove bad fruits and impurities from black goji berries; after cleaning, mix with water at a solid-liquid ratio of 1g:30mL, soak at room temperature for 30 minutes, and juice to obtain black goji berry pulp. S2. Centrifugal filtration: Centrifuge the black goji berry slurry at 6000 rpm for 4 min and collect the supernatant A; combine the residues and mix with water at a solid-liquid ratio of 1 g: 10 mL, sonicate at 45±5℃ and 300W for 10 min, centrifuge again at 6000 rpm for 4 min and collect the supernatant B; combine supernatant A and supernatant B, concentrate until the solid-liquid ratio of black goji berries to liquid is 1 g: 20 mL, and obtain the supernatant mixture; S3. Sterilization: After filling the supernatant mixture, sterilize it in a water bath. When the temperature of the supernatant mixture reaches 90°C, continue for 10 minutes and then cool to room temperature.

[0043] Comparative Example 1 Unlike Example 1, in step (1), the bacterial strain used was *Lactobacillus plantarum* S10. Replacing *Lactobacillus plantarum* GH-6 with *Lactobacillus plantarum* S10 resulted in an activated bacterial count of 2.0 × 10⁻⁶. 9 CFU / mL.

[0044] Everything else is the same as in Example 1.

[0045] Comparative Example 2 Unlike Example 1, in step (2), the inoculation amount is 2%. Everything else is the same as in Example 1.

[0046] Comparative Example 3 Unlike Example 1, in step (2), the inoculation amount is 5%. Everything else is the same as in Example 1.

[0047] Comparative Example 4 Unlike Example 1, in step (2), the fermentation time is 6 hours. Everything else is the same as in Example 1.

[0048] Comparative Example 5 Unlike Example 1, in step (2), the solid-liquid ratio of black goji berries to liquid in the supernatant mixture of step S2 is 1g:40mL in the preparation method of black goji berry juice. All other steps are the same as in Example 1.

[0049] Experiment 1: Detection of viable lactic acid bacteria count Take 1.0 mL of fermented black goji berry juice and determine the number of live bacteria in the fermented black goji berry juice using the "GB 4789.35-2023 National Food Safety Standard for Microbiological Examination of Food - Lactic Acid Bacteria Examination".

[0050] The results of the detection of viable bacteria count in the fermented black goji berry juice of each embodiment and comparative example are shown in Table 1.

[0051] The percentage increase in viable bacteria count (%) = (number of viable bacteria in fermented black goji berry juice - number of viable bacteria in black goji berry juice before fermentation) / number of viable bacteria in black goji berry juice before fermentation × 100%.

[0052] Table 1

[0053] As can be seen from Table 1, the fermentation method of the present invention can protect the lactic acid bacteria strains from being destroyed; and, in the fermentation and black goji berry juice preparation process described in the present invention, it brings about a significant increase in the number of viable bacteria, and the increase rate of viable bacteria is significantly better than that of the comparative example.

[0054] Experiment 2: Total Acidity Detection of Fermented Black Goji Berry Juice Test method: Take 25 mL of fermented black goji berry juice and determine the total acid (g / L, calculated as lactic acid) in the fermented black goji berry juice using the method specified in GB 12456-2021 National Food Safety Standard - Determination of Total Acid in Food (Third Method: Automatic Potentiometric Titration).

[0055] The results of total acid detection in the fermented black goji berry juice of each embodiment and comparative example are shown in Table 2.

[0056] Table 2

[0057] As can be seen from Table 2, the fermentation method of the present invention can effectively avoid the phenomenon of low or high total acidity, making the sweet and sour balance and overall flavor of the product more friendly and stable, thus having a pleasant taste.

[0058] Experiment 3 Sensory Evaluation A sensory evaluation team composed of 10 food science students and teachers with sensory experience in food was formed to taste and evaluate the fermented black goji berry juice in a clean and odorless environment, and to score it according to the sensory evaluation criteria in Table 3. After tasting each sample, the tasters rinsed their mouths with purified water for at least 30 seconds, and waited at least 30 minutes before evaluating the next set of fermented black goji berry juice samples.

[0059] The sensory evaluation results of the fermented black goji berry juice of each embodiment and comparative example are shown in Table 4.

[0060] Table 3

[0061] Table 4

[0062] As shown in Table 4, the fermentation method of this invention can significantly improve the color of fermented black goji berry juice. The resulting fermented black goji berry juice is uniform, free of sediment and stratification, with a rich fruity aroma, a delicate and harmonious fermentation fragrance, no off-odors, a balanced sweet and sour flavor, a pure and rich fruity taste, and no bitter or astringent off-flavors, resulting in high overall popularity. In contrast, the comparative method, which altered the fermentation process, resulted in a significant decrease in the color, texture, aroma, flavor, and overall acceptability score of the fermented black goji berry juice.

[0063] Experiment 4 Antioxidant properties of fermented black goji berry juice (1) DPPH method: Prepare a 0.1 mmol / L DPPH (2,2-diphenyl-1-picrylhydrazine free radical) ethanol solution and store it in the dark for later use. Dilute the fermented black goji berry juice of each example and each comparative example with 95% ethanol at a volume ratio of 1:9 (10-fold dilution). Take 2 mL of the diluted sample and mix it with 2 mL of DPPH solution. After reacting at room temperature in the dark for 30 min, measure the absorbance at 517 nm using a 1 cm path length cuvette. Establish a standard curve (R²≥0.99) of DPPH inhibition rate versus Trolox concentration using different concentrations of Trolox (concentration range 10–100 µmol / L). Substitute the inhibition rate of the fermented black goji berry juice of each example and each comparative example into the standard curve, convert it to Trolox equivalent concentration (µmol / L), and calculate the antioxidant capacity (TEAC, unit mmolTE / L) of each sample stock solution in combination with the dilution factor. All measurements were repeated in triplicate, and the results are expressed as mean ± standard deviation.

[0064] (2) ABTS method: A 7 mmol / L ABTS solution was prepared using 0.1 mol / L phosphate buffer (PBS, pH 7.4) and mixed with 2.00 mmol / L potassium persulfate solution at a volume ratio of 1:1. The mixture was then allowed to stand in the dark for 16 h to generate an ABTS free radical stock solution. This stock solution was diluted with PBS buffer to an absorbance of approximately 0.700 ± 0.010 at a wavelength of 734 nm, which became the ABTS free radical working solution. Fermented black goji berry juice from each example and comparative example was diluted with PBS buffer at a volume ratio of 1:9 (10-fold dilution). 0.1 mL of the diluted sample was taken and mixed with 3.9 mL of ABTS free radical working solution. After reacting at room temperature in the dark for 6 min, the absorbance was measured at 734 nm using a 1 cm path length cuvette. A standard curve (R² ≥ 0.99) was established using different concentrations of Trolox (concentration range 5-20 µmol / L) to compare the ABTS inhibition rate with the Trolox concentration. The inhibition rates of fermented black goji berry juice from each example and comparative example were substituted into the standard curve and converted to Trolox equivalent concentrations (µmol / L). The antioxidant capacity (TEAC, mmol TE / L) of each sample stock solution was then calculated based on the dilution factor. All measurements were performed in triplicate, and the results are expressed as mean ± standard deviation.

[0065] (3) FRAP method: FRAP working solution was prepared by mixing acetate buffer (300 mmol / L, pH 3.6), TPTZ solution (10 mmol / L, dissolved in 40 mmol / L HCl), and FeCl3 solution (20 mmol / L) at a volume ratio of 10:1:1 and preheating at 37°C for 10 min. Fermented black goji berry juice from each example and comparative example was diluted 1:1 with distilled water. 60 µL of the diluted solution was mixed with 1140 µL of FRAP working solution and reacted at 37°C for 4 min. The absorbance was immediately measured at 593 nm using a 1 cm path length cuvette. A standard curve (R² ≥ 0.99) was established using different concentrations of FeSO4 (concentration range 0.10-1.00 mmol / L). The sample absorbance was converted to mmol Fe². + eq / L represents reducing power. All measurements were performed in triplicate, and results are expressed as mean ± standard deviation.

[0066] The antioxidant capacity test results of the fermented black goji berry juice of each embodiment and comparative example are shown in Table 5.

[0067] Table 5

[0068] As can be seen from Table 5, the fermented black goji berry juice obtained by the present invention using specific strains and specific fermentation conditions is significantly higher than that of the comparative samples in terms of three antioxidant evaluation indicators: DPPH free radical scavenging ability, ABTS cationic free radical scavenging ability, and FRAP reducing power.

[0069] Specifically, this manifests as follows: In the DPPH assay, Examples 1 and 3 achieved 26.02±1.10 mmol TE / L and 20.71±0.86 mmol TE / L, respectively, significantly higher than Comparative Examples 1-4. In the ABTS assay, Examples 1 and 3 achieved 50.28±2.51 mmol TE / L and 40.65±2.01 mmol TE / L, respectively, while Example 2 achieved 22.90±1.50 mmol TE / L, significantly higher than Comparative Examples 1-4. In the FRAP assay, Examples 1 and 3 achieved 62.63±3.05 mmol Fe, respectively. 2+ eq / L and 53.69±2.55mmol Fe 2+ E / L, in Example 2, was 34.03 ± 1.68 mmol Fe. 2+ The eq / L ratio was significantly higher than that of comparative examples 1-4.

[0070] In summary, the fermentation method of the present invention significantly and stably improves the antioxidant capacity of fermented black goji berry juice while controlling the number of live bacteria, acidity, and flavor. This technology is superior to the comparative example and has batch stability and can be industrialized.

[0071] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A fermentation method for fermented black goji berry juice with high antioxidant properties, characterized in that, Including the following steps: (1) Activation of the strain to obtain an activated strain; the strain is Lactobacillus plantarum GH-6; (2) Inoculate the activated strain into the raw black goji berry juice at an inoculation rate of 2.5%-3.5% and ferment for 3-5 hours to obtain fermented black goji berry juice.

2. The fermentation method according to claim 1, characterized in that, The activated bacterial strain has a viable count of 1.0 × 10⁻⁶. 9 -2.0×10 9 CFU / mL.

3. The fermentation method according to claim 1, characterized in that, In step (2), the preparation method of the raw material black goji berry juice is as follows: S1. Remove bad fruits and impurities from black goji berries; wash them clean, mix them with water, soak them, and juice them to obtain black goji berry pulp. S2. Centrifugal filtration: Centrifuge the black goji berry pulp and take the supernatant A; combine the residues and mix them with water for ultrasonic treatment, then centrifuge again to take the supernatant B; combine supernatant A and supernatant B to obtain a supernatant mixture. S3. Sterilization: Sterilize the supernatant mixture in a water bath and cool it to room temperature for later use.

4. The fermentation method according to claim 3, characterized in that, In step S1, the soaking process involves a solid-liquid ratio of 1g:10-30mL and a soaking time of 30-90min. In step S2, the centrifugation specifically refers to centrifugation at 4000-6000 rpm for 4-8 minutes.

5. The fermentation method according to claim 3, characterized in that, In step S2, the solid-liquid ratio of the residue to water is 1g:10-30mL when the mixture is mixed with water. In step S2, the ultrasonic treatment time is 10-30 min; the ultrasonic treatment power is 200-400 W, and the temperature is 30-50℃. In step S2, the supernatant mixture is concentrated until the solid-liquid ratio of black goji berries to liquid is 1g:10-30mL.

6. The fermentation method according to claim 3, characterized in that, In step S3, the water bath sterilization specifically involves heating the supernatant mixture in a water bath until the temperature reaches 80-90°C, and then continuing this process for 10-30 minutes.

7. The fermentation method according to claim 1, characterized in that, In step (2), the inoculation amount is 3%.

8. The fermentation method according to claim 1, characterized in that, In step (2), the fermentation treatment time is 4 hours; In step (2), the fermentation temperature is 34-40℃; in step (2), the fermentation temperature is preferably 34-37℃.

9. A fermented black goji berry juice, prepared by the fermentation method according to any one of claims 1-8.

10. The use of the fermentation method according to any one of claims 1-8 in the preparation of beverages with high sensory evaluation, free radical scavenging function and antioxidant properties.

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