Mixed lactic acid bacteria fermented pomegranate juice and method for preparing the same

Abstract

The application discloses a kind of mixed lactic acid bacteria fermented sour pomegranate juice and preparation method thereof, belong to food processing technical field.The application uses sour pomegranate juice as raw material, adopts Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum three kinds of lactic acid bacteria according to optimized proportion mixed fermentation, is made into fermented juice after deployment, concentration, sterilization and the like process.The application significantly improves the polyphenol content and antioxidant activity of sour pomegranate juice by specific strain combination and its fermentation process optimization, improves flavor quality, electronic tongue analysis shows that umami is increased by 32%, and alcohol thickness is enhanced by 6%, GC-IMS analysis shows that characteristic aroma components such as hexanal and limonene are increased by 1.95 times and 1.45 times respectively.The application uses erythritol to replace sucrose to prepare low-sugar juice, and the product has bright color, sour and sweet taste, unique aroma, good nutritional value and market application prospect.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a sour pomegranate juice fermented with mixed lactic acid bacteria and its preparation method. Background Technology

[0002] Sour pomegranate (Punica granatum L.) is a specialty fruit of Xinjiang Uygur Autonomous Region, my country. Rich in polyphenols, flavonoids, amino acids, and various minerals, it possesses high nutritional value and health benefits. However, its sour and astringent taste makes it unappealing to eat fresh, resulting in low processing and utilization rates. Most of it is used as animal feed or discarded, leading to resource waste.

[0003] Most existing fruit juice products are high in sugar, typically exceeding 60%. Long-term consumption can increase the risk of metabolic diseases such as obesity and diabetes. In recent years, low-sugar fruit juice has become a consumer trend, but simply reducing sugar content often affects the juice's gelling properties, taste, and shelf life.

[0004] Fermentation is a method to enhance the value of agricultural products and improve their flavor and nutritional properties. Numerous studies have been conducted on pomegranate fermentation. For example, research on pomegranate wine has explored changes in its antioxidant properties and flavor characteristics. Regarding antioxidant properties, total phenolic content and free radical scavenging activity fluctuated slightly during fermentation, but remained at high and stable levels during aging. Glycosides and gallic acid, as the main phenolic components, played a dominant role throughout the fermentation process. In terms of flavor characteristics, the most significant changes occurred in the early stages of fermentation (0–4 days), during which aldehyde and ketone content decreased, while ester and alcohol content increased. Furthermore, researchers found that when pomegranate beverages were fermented with yeast, the total soluble solids (TSS) content decreased after fermentation, ethanol content increased with increasing initial TSS, and titratable acidity also increased. However, there are no reports on the fermentation of acidic pomegranates.

[0005] Lactic acid bacteria play a crucial role in the food industry and human health. Their application in fruit and vegetable juice fermentation not only imparts unique flavors to the products but also enhances their functionality. However, single-strain fermentation has certain limitations, such as low utilization efficiency of reducing sugars and certain bioactive components (e.g., total phenols and flavonoids). Mixed-strain fermentation, on the other hand, leverages the synergistic effects of multiple strains, offering greater advantages in physicochemical properties, bioactivity, flavor, and nutritional value compared to single-strain fermentation, and is therefore considered an ideal fermentation strategy. For example, mixed-strain fermentation of orange juice can significantly improve vitamin C retention and increase the content of flavor compounds such as esters and alcohols, thereby improving the product's taste.

[66] Apple juice fermented with mixed strains also showed significantly enhanced antioxidant activity and flavor.

[0006] Lactic acid bacteria fermentation technology can improve the flavor of fruit and vegetable raw materials and enhance their functional activity. However, most existing fermented juices use a single strain, resulting in limited fermentation efficiency and a single flavor profile. Furthermore, there has been no systematic research on the fermentation process and juice products for sour pomegranates.

[0007] Therefore, developing a mixed-culture fermentation process suitable for sour pomegranates and producing fermented juices with good flavor, strong functional activity, and low sugar content is of significant application value. Summary of the Invention

[0008] The present invention aims to provide a sour pomegranate juice fermented with mixed lactic acid bacteria and its preparation method, so as to solve the problems of low processing utilization rate of sour pomegranate, high sugar content of juice products, and monotonous fermentation flavor.

[0009] The present invention provides a method for preparing pomegranate juice fermented with mixed lactic acid bacteria, comprising the following steps:

[0010] (1) Sterilize the sour pomegranate juice to obtain sterilized sour pomegranate juice;

[0011] (2) The activated Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum were mixed in proportion to obtain a mixed bacterial solution;

[0012] (3) The mixed bacterial solution is inoculated into the sterilized acid pomegranate juice for fermentation to obtain fermented acid pomegranate juice;

[0013] (4) Add sugar substitute to the fermented pomegranate juice and mix well to obtain the fermented pomegranate juice with mixed lactic acid bacteria.

[0014] Preferably, the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum in step (2) is (28-32):(30-35):(40-48).

[0015] More preferably, the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus fermentum is 28:31:45.

[0016] Preferably, the inoculation amount of the mixed bacterial solution in step (3) is 1.5-2.5%, the fermentation temperature is 35-38℃, and the fermentation time is 10-12 hours.

[0017] More preferably, the inoculation amount of the mixed bacterial solution is 2%, and the fermentation time is 11 hours.

[0018] Preferably, the sugar substitute mentioned in step (4) is erythritol, and its addition amount is 10-20% of the mass of fermented pomegranate juice.

[0019] Preferably, the sterilization process in step (1) is water bath sterilization at 80-90°C for 20-40 minutes.

[0020] The present invention also provides a mixed lactic acid bacteria fermented pomegranate juice prepared by the above method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This invention uses three strains of Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum in a specific ratio for fermentation. By utilizing the synergistic effect between the strains, the fermentation efficiency is significantly improved. The resulting juice has a suitable total acid content and a polyphenol content of up to 598.33 mg GAE / 100g FW, giving the juice a good sweet and sour taste and antioxidant activity.

[0023] (2) The present invention significantly improves the flavor characteristics of sour pomegranate through mixed bacterial fermentation. Electronic tongue analysis shows that the umami of the juice is increased by 32% and the body is enhanced by 6% after fermentation. GC-IMS analysis shows that the characteristic aroma components such as hexanal and limonene are increased by 1.95 times and 1.45 times, respectively, and the aroma complexity and pleasantness of the juice are significantly improved.

[0024] (3) This invention uses erythritol to replace traditional sucrose, which reduces calorie intake while maintaining a good taste, and produces low-sugar fermented fruit juice that meets the needs of modern healthy diets;

[0025] (4) The fermented pomegranate juice prepared by the present invention has been verified by in vitro digestion experiments. Its functional components such as polyphenols and flavonoids maintain good stability during simulated gastrointestinal digestion, have significant antioxidant activity, and have good nutritional and health value. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] Figure 1 The above are radar images of the fermented pomegranate juice and the unfermented pomegranate juice prepared in Example 1 of this invention, obtained by electronic tongue analysis.

[0028] Figure 2 This is a comparison of the GC-IMS fingerprint spectra of volatile components of fermented pomegranate juice and unfermented pomegranate juice prepared in Example 1 of this invention.

[0029] Figure 3 The effects of different levels of *Lactobacillus fermentum* added to this invention on pomegranate polyphenol content (A), total acid content (B), and soluble solids content (C);

[0030] Figure 4 The effects of different levels of Lactobacillus casei addition on pomegranate polyphenol content (A), total acid content (B), and soluble solids content (C) were investigated in this invention.

[0031] Figure 5 The effects of different levels of *Lactobacillus rhamnosus* added to pomegranate on polyphenol content (A), total acid content (B), and soluble solids (C) were investigated in this invention.

[0032] Figure 6 The effects of different levels of Lactobacillus acidophilus added to pomegranate on polyphenol content (A), total acidity (B), and soluble solids (C) were investigated in this invention.

[0033] Figure 7 The effects of different levels of *Lactobacillus plantarum* added to this invention on pomegranate polyphenol content (A), total acid content (B), and soluble solids (C);

[0034] Figure 8 Radar charts (B) showing the polyphenols, total acid, TSS (A), and sensory scores after 12 h of fermentation with different mixed bacterial ratios according to the present invention.

[0035] Figure 9 The polyphenols, total acid, and TSS of the present invention after fermentation for 12 h with different mixed inoculum amounts;

[0036] Figure 10 The effects of different fermentation times on polyphenol content (A), total acid content (B), and soluble solids (C) at a 2% inoculum amount of this invention are investigated.

[0037] Figure 11 This is a PCA score diagram of the pomegranate juice sample from the present invention.

[0038] Figure 12 This is a gallery plot showing the fingerprint of volatile compounds before and after fermentation in this invention.

[0039] Figure 13 The graphs show the PLS-DA scores of the metabolome before and after fermentation (A) and the displacement test graph (B) of this invention. Detailed Implementation

[0040] The present invention will be further explained below with reference to specific implementation schemes, but this explanation does not limit the scope of the invention.

[0041] Screening experiments of fermentation conditions of the present invention

[0042] To determine the optimal combination of lactic acid bacteria strains, mixed culture ratio, inoculum size, and fermentation time, this invention first conducted a series of single-factor and uniform design experiments. All experiments used pomegranate juice as raw material and were conducted at 37°C and a shaker speed of 200 rpm. The specific screening process and results are as follows.

[0043] 1. Screening of fermentation strains:

[0044] Five types of lactic acid bacteria (Lactobacillus fermentum, Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus acidophilus, and Lactobacillus plantarum) were inoculated into sterilized pomegranate juice at inoculation rates of 1%, 2%, 3%, 4%, and 5%, respectively. Fermentation was carried out for 0-16 hours, and the contents of polyphenols, total acid, and soluble solids (TSS) were measured.

[0045] Figures 3 to 7 The following graph shows the effects of different levels of five lactic acid bacteria added according to this invention on the polyphenol, total acid, and soluble solids content of pomegranate juice:

[0046] Figure 3 (Fermented Lactobacillus): The polyphenol content reached its peak at a 3% inoculum size and 12 h of fermentation; the total acid content continued to increase with the extension of fermentation time, and the total acid accumulation was moderate at a 3% inoculum size; the TSS content fluctuated steadily.

[0047] Figure 4 (Lactobacillus casei): Polyphenol content reached its peak at 3% inoculum and 12 h of fermentation; total acid increased with fermentation time; TSS was stable.

[0048] Figure 5 (Lactobacillus rhamnosus): The polyphenol content reached its peak at a 1% inoculum and 12 h of fermentation, but the highest value was lower than that of Lactobacillus fermentum; total acidity increased; TSS remained stable.

[0049] Figure 6 (Lactobacillus acidophilus): Polyphenol content reached its peak at 3% inoculum and 12 h of fermentation; total acidity increased; TSS remained stable.

[0050] Figure 7 (Lactobacillus plantarum): Polyphenol content reached its peak at 3% inoculum and 12 h of fermentation; total acidity increased; TSS remained stable.

[0051] In summary, the polyphenol content was ranked as follows: *Lactobacillus fermentum* > *Lactobacillus plantarum* > *Lactobacillus acidophilus* > *Lactobacillus casei* > *Lactobacillus rhamnosus*. The polyphenol content initially increased and then decreased with fermentation time, reaching a peak around 12 hours. Among these, *Lactobacillus fermentum*, *Lactobacillus plantarum*, and *Lactobacillus acidophilus* had the highest polyphenol content at a 3% inoculum size and 12 hours of fermentation, at 586.2 mg GAE / 100g FW, 572.5 mg GAE / 100g FW, and 561.8 mg GAE / 100g FW, respectively, significantly higher than other strains. < 0.05). The total acid content continuously increased with fermentation time, while the TSS content remained stable. Therefore, this invention selected *Lactobacillus fermentum*, *Lactobacillus plantarum*, and *Lactobacillus acidophilus* as mixed fermentation strains.

[0052] 2. Optimization of mixed bacterial ratio

[0053] A three-factor, eight-level uniform design was adopted (see Table 1). The three strains were mixed in different proportions (the total inoculum was fixed at 2%). After fermentation for 12 h, the polyphenols, total acid, TSS and sensory scores were measured (the sensory evaluation criteria are shown in Table 2).

[0054] Table 1. Uniform design, mixed bacterial ratio, and experimental results.

[0055]

[0056] Table 2 Sensory Evaluation Criteria

[0057]

[0058] like Figure 8 As shown in Figure A (which shows the polyphenol, total acid, and TSS content under different mixed bacterial ratios, and Figure B (which shows the sensory score radar chart)): Figure A shows that the polyphenol content of group 8 (45% Lactobacillus fermentum, 31% Lactobacillus plantarum, and 28% Lactobacillus acidophilus) was the highest, reaching 598.33 mg GAE / 100g FW; the total acid content of group 1 was the highest, but the total acid content of group 8 was within the appropriate range (0.85 g / 100g); there was no significant difference in TSS among the groups.

[0059] Figure B shows that Group 8 had the highest sensory score of 83.6 points, with a sweet and sour taste, bright color, and typical fermented pomegranate aroma; Group 7 (41:32:27) had the lowest sensory score (58.4 points), with a poor taste and obvious layering.

[0060] Therefore, the present invention determines the optimal mixed culture ratio as 45% Lactobacillus fermentum, 31% Lactobacillus plantarum, and 28% Lactobacillus acidophilus (mass ratio, which is an approximate ratio of 28:31:45).

[0061] 3. Screening of mixed inoculum size: Fermentation was carried out for 12 h at inoculum sizes of 1%, 2%, 3%, 4%, and 5% respectively, under the optimal mixed inoculum ratio.

[0062] like Figure 9 As shown in Figure A (polyphenol content), Figure B (total acid), and Figure C (TSS): Figure A shows the highest polyphenol content (598.33 mg GAE / 100g FW) at an inoculum size of 2%, and the lowest at 5%. Figure B shows the highest total acid content (0.85g / 100g) at an inoculum size of 2%, and the lowest at 1%. Figure C shows no significant difference in TSS across different inoculum sizes.

[0063] Therefore, the present invention determines the optimal inoculation amount to be 2% (v / v).

[0064] 4. Screening of mixed-culture fermentation time: Fermentation was conducted for 8, 9, 10, 11, 12, 13, 14, 15, and 16 hours at the optimal mixed-culture ratio and 2% inoculum. Figure 10 As shown in Figure A (polyphenol content, total acid, TSS): In Figure A, the polyphenol content first increases and then decreases, reaching the highest value (598.33 mg GAE / 100g FW) at 11 h.

[0065] Figure B: Total acid content increases with fermentation time, reaching its highest value at 14 h, but at 11 h, the total acid is 0.85 g / 100g, with a suitable taste. Figure C: TSS shows no significant change. Therefore, this invention determines the optimal fermentation time to be 11 hours.

[0066] The screening experiments described above show that the strain combination, mixed strain ratio, inoculum amount and fermentation time determined in this invention can significantly improve the polyphenol content and sensory quality of pomegranate juice, providing optimal process parameters for subsequent juice preparation.

[0067] Example 1

[0068] (1) Raw material pretreatment: Take fresh Xinjiang sour pomegranates, wash, peel and juice them to obtain sour pomegranate juice; sterilize the sour pomegranate juice in an 85℃ water bath for 30 minutes to obtain sterilized sour pomegranate juice;

[0069] (2) Activation of mixed strains: Lactobacillus acidophilus (CICC 6086), Lactobacillus plantarum (CICC 25125), and Lactobacillus fermentum (CICC 25124) were inoculated into MRS liquid medium and cultured at 37°C for 24 hours to obtain activated bacterial suspensions with a viable count ≥1×10⁻⁶. 7 CFU / mL;

[0070] (3) Mixed bacterial fermentation: The activated Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum were mixed in a mass ratio of 28:31:45 to obtain a mixed bacterial solution; the mixed bacterial solution was inoculated into sterilized acid pomegranate juice at an inoculation rate of 2%, and fermented at 37°C and a shaking speed of 200 rpm for 11 hours to obtain fermented acid pomegranate juice.

[0071] (4) Juice preparation: Add 15% of the weight of erythritol to the fermented sour pomegranate juice and stir well to obtain sour pomegranate juice fermented with mixed lactic acid bacteria.

[0072] According to the test results, the fermented pomegranate juice prepared in this embodiment has a polyphenol content of 598.33 mg GAE / 100g FW, a total acid content of 0.85 g / 100g, and a soluble solids content of 8.2%. The product has a bright color, a sweet and sour taste, and a typical fermented pomegranate aroma.

[0073] Verification of the effect of fermentation on the flavor and quality of pomegranate juice: To verify the effect of mixed-culture fermentation of the present invention on improving the flavor of pomegranate juice, the fermented pomegranate juice (before the addition of artificial sweeteners) prepared by the method in Example 1 and the unfermented pomegranate juice were compared and analyzed by electronic tongue, electronic nose, GC-IMS and non-targeted metabolomics. The results are as follows.

[0074] 1. Analysis of electronic tongue and electronic nose

[0075] like Figure 1 As shown in Figure A (electronic tongue radar image, Figure B (electronic nose radar image)): Figure A shows that the fermented sample exhibited a 32% increase in umami, a 6% increase in body, and a significant enhancement in aftertaste A (positive aftertaste); saltiness and astringency were also prominent. In contrast, the unfermented sample showed more pronounced sourness, bitterness, and aftertaste B. This indicates that fermentation increases the content of umami substances (such as amino acids), improving the taste. Figure B shows that the fermented group showed significantly higher responses than the control group in the dimensions of W1C (aromatic components), W2S (alcohols, aldehydes, ketones), W1S (methyl compounds), and W5C (hydrogen-containing compounds), indicating that fermentation promotes the formation of volatile flavor compounds such as alcohols, aldehydes, terpenes, and sulfur-containing compounds.

[0076] 2. GC-IMS Analysis

[0077] like Figure 2 , 11 As shown in Tables 1, 12, and 3: Figure 2 In Figure A (3D spectrum): The fermentation group shows a new red area, indicating the production of new volatile organic compounds (VOCs). In Figure B (2D top view): The fermented sample shows a new red peak in the 800-1000s drift time range, while the unfermented sample shows dense peaks in the 1000-1200s range, indicating that fermentation alters the VOCs distribution. In Figure C (difference graph): The yellow area (unique to or higher in the fermentation group) mainly includes microbial metabolites such as esters and furans, which bring new flavor layers to the juice; the blue area (unique to or higher in the control group) mainly consists of the original background aroma substances.

[0078] Table 3. Changes in volatile flavor compounds before and after fermentation.

[0079]

[0080] Figure 11 (PCA score plot): The control group and the fermentation group were significantly separated on principal component 1 (61%), with a cumulative contribution rate of 83%, indicating that the VOCs of the two groups of samples were significantly different and the model was reliable.

[0081] Figure 12(Gallery plot fingerprinting): The fermentation group showed significant increases in intensity in both region a (common components) and region b (key flavor components, including alcohols and compounds that impart a milky aroma). Referring to Tables 2-4, most VOCs increased in content after fermentation, with acetic acid (D) peak volume increasing by 217.08%, benzaldehyde by 146.15%, 3-hydroxy-2-butanone by 122.96%, limonene (not listed in the table, but known from GC-IMS qualitative results) by 1.45 times, and hexanal by 1.95 times. These substances enhance the fruity, grassy, ​​and mellow acidity, giving the product a unique fermented aroma.

[0082] 3. Non-targeted metabolomics analysis, such as Figure 13 And as shown in Table 4: Figure 13 A (PLS-DA score plot): Significant separation between the control group and the fermentation group (R) 2 Y=0.978, Q 2 =0.786), indicating that fermentation has a significant impact on metabolite composition. Figure B (permutation test) verifies that the model is not overfitting (R² = 0.786). 2 Y=0.9585, Q 2 =-0.0177), the difference is reliable.

[0083] Table 4 shows that 13 functional metabolites, including triterpenoids (squalene precursor diphosphate, upregulated 2.69-fold), cyclic peptides (butyroalkaloid A, upregulated 2.60-fold), oligopeptides (sphalomycin D, upregulated 2.09-fold), dipeptides (valine-glycine, upregulated 1.88-fold), organic acid derivatives, and coumarins, were significantly upregulated after fermentation (FC>1.5, p<0.05). These substances have potential health benefits such as antioxidant activity, immunomodulation, and flavor enhancement.

[0084] The above flavor and metabolomics analysis results show that the mixed bacterial fermentation method of this invention can significantly improve the sensory quality and functional activity of pomegranate juice. The resulting juice has a complex and unique aroma, a mellow and refreshing taste, and has good market application prospects.

[0085]

[0086] Example 2

[0087] (1) Raw material pretreatment: Same as in Example 1;

[0088] (2) Activation of mixed strains: Same as in Example 1;

[0089] (3) Mixed bacterial fermentation: The activated Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum were mixed in a mass ratio of 30:33:43 to obtain a mixed bacterial solution; the mixed bacterial solution was inoculated into sterilized acid pomegranate juice at an inoculation rate of 2.5%, and fermented at 37°C and a shaking speed of 200 rpm for 12 hours to obtain fermented acid pomegranate juice;

[0090] (4) Juice preparation: Add 12% of the weight of erythritol to the fermented sour pomegranate juice and stir well to obtain sour pomegranate juice fermented with mixed lactic acid bacteria.

[0091] The fermented pomegranate juice prepared in this embodiment has a polyphenol content of 568.42 mg GAE / 100g FW and a total acid content of 0.92 g / 100g, indicating good product quality.

[0092] Comparative Example 1

[0093] The difference from Example 1 is that only *Lactobacillus plantarum* was used for fermentation in step (3), while the other conditions remained the same. The results showed that the polyphenol content of the fruit juice prepared in Comparative Example 1 was 421.36 mg GAE / 100g FW, which was significantly lower than that in Example 1; electronic tongue analysis showed that its umami and body scores were lower than those in Example 1, and the types and contents of aroma components were also significantly reduced.

[0094] Comparative Example 2

[0095] The difference from Example 1 is that an equal amount of sucrose was used instead of erythritol in step (4), while the other conditions remained the same. The results showed that the total sugar content of the juice prepared in Comparative Example 2 was significantly higher than that in Example 1, and it had a higher calorie content and a sweeter taste, which did not meet the requirements for low-sugar healthy foods.

[0096] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0097] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for preparing pomegranate juice fermented with mixed lactic acid bacteria, characterized in that, Includes the following steps: (1) Sterilize the sour pomegranate juice to obtain sterilized sour pomegranate juice; (2) The activated Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum were mixed in proportion to obtain a mixed bacterial solution; (3) The mixed bacterial solution is inoculated into the sterilized acid pomegranate juice for fermentation to obtain fermented acid pomegranate juice.

2. The preparation method according to claim 1, characterized in that, The mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus fermentum in step (2) is (28–32):(30–35):(40–48).

3. The preparation method according to claim 2, characterized in that, The mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus fermentum is 28:31:

45.

4. The preparation method according to claim 1, characterized in that, The inoculation amount of the mixed bacterial solution in step (3) is 1.5–2.5%, the fermentation temperature is 35–38℃, and the fermentation time is 10–12 hours.

5. The preparation method according to claim 4, characterized in that, The inoculation amount of the mixed bacterial solution was 2%, and the fermentation time was 11 hours.

6. The preparation method according to claim 1, characterized in that, The sugar substitute mentioned in step (4) is erythritol, and its addition amount is 10–20% of the mass of fermented pomegranate juice.

7. The preparation method according to claim 1, characterized in that, The thickener mentioned in step (4) is one or more of pectin, sodium alginate or sodium carboxymethyl cellulose, and its addition amount is 0.2–0.6% of the mass of fermented pomegranate juice.

8. The preparation method according to claim 1, characterized in that, The sterilization process described in step (1) is water bath sterilization at 80–90°C for 20–40 minutes.

9. A sour pomegranate juice fermented with mixed lactic acid bacteria, characterized in that, It is prepared by the preparation method according to any one of claims 1–8.

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