Blueberry compound beverage rich in anthocyanin and preparation method thereof

Abstract

The application discloses a blueberry compound beverage rich in anthocyanins and a preparation method thereof. The application takes blueberries as main raw materials, and is matched with coconut juice to realize resource utilization of blueberry processing pomace. The blueberries are first soaked and pretreated, then stored in a frozen state, half-thawed, and then whipped to realize full breakage of the cell walls of the blueberries, inoculated with compound probiotics for fermentation, and the anthocyanins in the waste blueberry pomace are extracted by using coconut juice as an extraction liquid, the extraction liquid is used as a feeding carbon source in the middle period of fermentation to supplement the fermentation substrate; and the fermentation stock solution is sterilized and filled to obtain a finished product. The anthocyanin content of the application is significantly better than that of a traditional fermented blueberry beverage; the product is combined with blueberry fruit aroma, fermented enzyme aroma and coconut aroma three flavors, and has smooth taste without irritating sourness.

Description

Technical Field

[0001] This invention belongs to the field of fermented functional beverage processing technology, specifically relating to a blueberry compound beverage rich in anthocyanins and its preparation method. Background Technology

[0002] Blueberries (Vaccinium corymbosum L.) belong to the genus Vaccinium in the family Ericaceae. Their fruits are rich in anthocyanins, total phenols, and flavonoid polyphenols, possessing various physiological functions such as antioxidation, relieving eye fatigue, and anti-inflammation, making them an excellent raw material for developing functional enzyme drinks. Anthocyanins have extremely strong antioxidant capabilities, able to scavenge free radicals in the body, delay cell aging, protect eyesight, and enhance immunity.

[0003] Anthocyanins are the aglycone structures of anthocyanins, meaning that anthocyanin molecules combine with sugar groups via glycosidic bonds to form anthocyanins. In nature, the polyphenolic pigments naturally present in blueberries mainly exist in the form of anthocyanins, with extremely low levels of free anthocyanin aglycones. Anthocyanins, as precursors to anthocyanins, undergo hydrolysis by gastric acid, intestinal enzymes, and gut microbiota in the human digestive tract, resulting in the cleavage of glycosidic bonds and the release of free anthocyanin aglycones. These aglycones are absorbed into the bloodstream through the intestines, directly exerting antioxidant and free radical scavenging functions. Therefore, the abundant anthocyanins in blueberries serve as a natural carrier and stable form of anthocyanins, exhibiting essential consistency in their functional activities.

[0004] Lactic acid bacteria are recognized as safe microorganisms that play an important role in maintaining human health and improving product flavor. Using blueberries as raw material, fermentation with various lactic acid bacteria can increase the content of blueberry polyphenols and their antioxidant activity.

[0005] Blueberry harvesting is concentrated in summer, so prolonged high-temperature storage easily leads to fruit spoilage. Transforming blueberries into processed products not only extends their shelf life and freshness but also improves the consumer experience, and is an effective utilization of blueberry resources. Current blueberry processing technology faces numerous technical bottlenecks, severely restricting product quality improvement and market promotion. First, prolonged room-temperature fermentation easily causes anthocyanin oxidation and decomposition, resulting in a dull color and a significant decrease in antioxidant activity in the finished product. Anthocyanins are highly susceptible to degradation under high temperature, light, and oxygen conditions, forming colorless or brown degradation products that severely affect the sensory quality and functional properties of the product. Second, blueberries themselves have a low sugar content and a simple polysaccharide structure, leading to insufficient substrate supply during fermentation, inadequate microbial metabolism, and low production of prebiotics and small-molecule active metabolites, resulting in a sharp acidity and a thin taste in the finished product. Furthermore, the pomace left after blueberry processing is usually discarded directly, but the pomace often contains a large amount of unreleased anthocyanins and polyphenols, resulting in low utilization of active substances, significant raw material loss, and poor economic efficiency. Summary of the Invention

[0006] Technical problems to be solved: This invention addresses the pain points of existing blueberry fermentation beverage technologies, such as long fermentation cycles, difficulty in enriching anthocyanins, easy initiation of fermentation with low sugar but incomplete subsequent fermentation, and poor flavor. It uses a natural plant color-protecting and antifreeze system to pre-treat and break down the cell walls of blueberries, shortening the fermentation cycle. It is combined with compound probiotic fermentation and uses coconut juice extraction to recover residual anthocyanins from the fruit residue and use it as a slow-release carbon source for fermentation, thereby enriching anthocyanins and improving flavor.

[0007] Technical solution: A method for preparing a blueberry complex beverage rich in anthocyanins, comprising the following steps: S1. Blueberries are soaked in the soaking solution and then frozen for later use. When using, they are taken out and thawed slowly at room temperature in a sealed container. They are then stirred to prepare blueberry puree. The puree is filtered to obtain blueberry juice and blueberry pulp. S2. Adjust the pH of the coconut juice, add chitosan and stir to dissolve it as a solvent for blueberry pomace extraction, add it to the blueberry pomace, stir to extract, filter and collect the coconut juice extract; S3. Sterilize blueberry juice, adjust pH, inoculate with compound probiotic agent, ferment at constant temperature, add coconut juice extract, continue fermentation, and obtain mixed fermentation liquid after fermentation is completed; S4. Filter the mixed fermentation liquid to obtain compound blueberry juice, add resistant dextrin, homogenize and bottle to obtain blueberry compound beverage.

[0008] Furthermore, in step S1, the soaking solution consists of 2.0-3.0 wt.% trehalose, 0.15-0.25 wt.% ascorbic acid, 0.08-0.12 wt.% grape seed extract, 0.1-0.18 wt.% wheat extract, and the remainder is water.

[0009] Furthermore, in step S1, the soaking time is 30-60 minutes; the mass ratio of blueberries to soaking liquid is 1:(1-2); and the thawing time is 2-3 hours.

[0010] Furthermore, in step S2, the pH is adjusted to 3.5-4.0; the amount of chitosan added is 0.1-0.2 wt.% of coconut juice; the mass ratio of blueberry pomace to coconut juice is 1:(3-5); the stirring and extraction speed is 500-800 rpm, and the time is 3-5 h.

[0011] Furthermore, in step S3, the pH is adjusted to 5.5-7.0; the compound probiotic agent includes Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum, and the viable count of the compound probiotics in the blueberry juice is 1×10⁻⁶. 6 -1×10 7 CFU / g; constant temperature fermentation temperature is 35-38℃, time is 6-8h; the amount of coconut milk extract added is 20-25wt.% of blueberry juice, added for 8-10h; continuous fermentation time is 60-72h.

[0012] Furthermore, the ratio of viable counts of *Lactobacillus plantarum*, *Lactobacillus acidophilus*, and *Bifidobacterium bifidum* is (4-6):(2-4):1.

[0013] Furthermore, in step S4, the amount of resistant dextrin added is 1-3 wt.% of the compound blueberry juice.

[0014] The above-described preparation method yields a blueberry complex beverage rich in anthocyanins. Beneficial effects

[0015] This invention employs a natural plant-based composite protection system of grape seeds and wheat, which combines multiple functions such as anti-oxidation, color enhancement, and cell antifreeze. It can effectively inhibit the oxidative degradation of anthocyanins, significantly release endogenous substrates through freeze-thaw pretreatment, shorten the fermentation cycle, and significantly improve the retention rate of anthocyanins and other active ingredients.

[0016] This invention utilizes mixed-culture fermentation, where endogenous metabolism of the microorganisms generates tannins that degrade in the tannin-degrading system, thus eliminating the inherent bitterness of blueberry fermentation, improving the clarity, color stability, and smoothness of the finished product, and effectively extending its shelf life and quality. The compound probiotic system continuously breaks down the large-molecule polysaccharides of blueberries and coconut milk, and is rich in natural prebiotics and enzyme-active metabolites, regulating intestinal health and possessing both antioxidant and intestinal care functions, distinguishing it from ordinary blended fruit juices.

[0017] This invention utilizes coconut juice extraction to remove traditionally discarded blueberry pomace. Coconut juice is used instead of pure water as the extraction solvent. Coconut juice contains a natural buffer system and soluble polysaccharides, which can improve the dissolution rate of bound anthocyanins. The extract is used as a functional feed liquid, added at a uniform rate during the mid-fermentation stage to replenish the carbon source. Simultaneously, the recovered functional components participate in the post-fermentation again, achieving secondary enrichment of active ingredients. Coconut juice has its own natural antioxidant matrix, which can inhibit the oxidative degradation of anthocyanins during the extraction process. The total anthocyanin retention rate of the finished product is much higher than that of traditional processes.

[0018] This invention features a mellow and harmonious flavor with a clear competitive advantage in the market. It eliminates bitterness, and the natural sweetness and milky aroma of coconut milk neutralizes the organic acids in blueberries. It combines the fruity aroma of blueberries, the fermented aroma of enzymes, and the delicate aroma of coconut, resulting in a smooth and mellow taste without any sour or astringent sensation. Attached Figure Description

[0019] Figure 1 Graphs showing anthocyanin content in different embodiments and comparative samples; Figure 2 The graph shows the antioxidant results of different embodiments and comparative examples. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Grape seed extract was purchased from Shifang Jubang Plant Raw Materials Co., Ltd., CAS NO: 84929-27-1; Wheat extract was purchased from Baoji Liupanyun Biotechnology Co., Ltd. Example 1

[0021] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶.6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 2

[0022] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When ready to use, remove the blueberries and thaw them slowly at room temperature in a sealed container for 3 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 3

[0023] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:5, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 4

[0024] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 4:2:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 5

[0025] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 60 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 6

[0026] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 20wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 7

[0027] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 4.5 × 10⁻⁶. 6CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Example 8

[0028] A method for preparing a blueberry complex beverage rich in anthocyanins includes the following steps: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 6 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Comparative Example 1

[0029] The difference between this comparative example and Example 1 is that the blueberries are not soaked before freezing, as detailed below: S1. Frozen blueberries are taken out and slowly thawed at room temperature for 2 hours in a sealed container. They are then blended to prepare blueberry puree. The puree is then filtered to obtain blueberry juice and blueberry pulp. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Comparative Example 2

[0030] The difference between this comparative example and Example 1 is that the blueberries were not subjected to a freeze-thaw process, as detailed below: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then remove and stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Comparative Example 3

[0031] The difference between this comparative example and Example 1 is that coconut milk extract is not added, as detailed below: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice, fermented at 36℃ for 80 hours, and the mixed fermentation liquid was obtained after the fermentation was completed; S3. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Comparative Example 4

[0032] The difference between this comparative example and Example 1 is that the coconut juice is replaced with water, as detailed below: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH to 3.8 with water, add chitosan at a content of 0.15 wt.%, stir to dissolve and use as a solvent for blueberry pomace extraction, add to blueberry pomace, the mass ratio of blueberry pomace to aqueous solution is 1:4, stir at 650 rpm for 4 hours and then filter to collect the extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice, fermented at 36℃ for 8 hours, then the extract was added by adding the extract. The total amount added was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Comparative Example 5

[0033] The difference between this comparative example and Example 1 is that Lactobacillus plantarum fermentation is not added, as detailed below: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container for 2 hours. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus acidophilus and Bifidobacterium bifidum in a live bacteria ratio of 3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Comparative Example 6

[0034] The difference between this comparative example and Example 1 is that the blueberries were completely thawed, as detailed below: S1. Prepare the soaking solution: trehalose 3.0 wt.%, ascorbic acid 0.25 wt.%, grape seed extract 0.12 wt.%, wheat extract 0.18 wt.%, with the remainder being water. Add blueberries to the soaking solution at a mass ratio of 1:2. Soak for 45 minutes, then freeze for later use. When using, remove from the freezer and thaw slowly at room temperature in a sealed container until completely thawed. Stir to prepare blueberry puree. Filter the puree to obtain blueberry juice and blueberry pomace. S2. Adjust the pH of the coconut juice to 3.8, add 0.15 wt.% chitosan from the coconut juice, stir to dissolve and use as the extraction solvent for blueberry pomace, add to the blueberry pomace, the mass ratio of blueberry pomace to coconut juice is 1:4, stir and extract at a constant temperature of 650 rpm for 4 hours, filter and collect the coconut juice extract. S3. Sterilize blueberry juice at 72℃ for 30 seconds, adjust pH to 6.0, and inoculate with a compound probiotic agent composed of Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum in a live bacteria ratio of 5:3:1, controlling the total live bacteria count of the compound probiotic agent to be 9×10⁻⁶. 6 CFU / g blueberry juice was fermented at a constant temperature of 36℃ for 8 hours, followed by the addition of coconut milk extract. The total amount of the added extract was 25wt.% of the blueberry juice, and the total addition time was controlled at 9 hours. Fermentation continued for 72 hours, and the mixed fermentation liquid was obtained after the fermentation was completed. S4. The mixed fermentation broth was filtered through a precision filter to obtain compound blueberry juice. 2 wt.% resistant dextrin was added to the compound blueberry juice and mixed evenly. After being homogenized under high pressure at 20 MPa, it was sterilized at 65°C for 15 min. Finally, it was aseptically filled to obtain a blueberry compound beverage rich in anthocyanins. Performance testing

[0035] Sensory evaluation Fifteen qualified food sensory evaluation personnel were selected, with a balanced gender ratio and no history of blueberry or coconut allergies. Prior to the evaluation, participants were instructed to abstain from spicy foods and rinse their mouths with warm water. Scores were awarded based on color (30 points), aroma (30 points), and taste (40 points).

[0036] The sensory evaluation results of the blueberry compound beverage are shown in Table 1. In Example 1 of this invention, the color score was 29.2, the aroma score was 28.5, and the taste score was 34.9, with a total sensory score of 92.6. Comparative Examples 3 and 4 did not add coconut milk and had lower sensory scores, indicating that coconut milk had a greater impact on the flavor. Comparative Example 5 lacked Lactobacillus plantarum, and the presence of tannins resulted in a poor taste.

[0037] Table 1 Sensory Evaluation Scores

[0038] 2. Anthocyanin content determination The pH differential method was used to prepare a sodium acetate buffer solution (pH 4.5) and a KCl buffer solution (pH 1.0). 1 mL of the sample was placed in two separate colorimetric tubes. 9 mL of sodium acetate buffer solution and 9 mL of KCl buffer solution were added to each tube, and the mixtures were thoroughly mixed. The tubes were then stored in the dark for 15 minutes. The absorbance at wavelengths of 520 nm and 700 nm was measured using a UV-Vis spectrophotometer. The anthocyanin content was calculated using the following formula:

[0039] In the formula: ρ is the anthocyanin content, mg / L; A520nm and A700nm are the absorbances of anthocyanins at wavelengths of 520nm and 700nm, respectively; Mw is the molar mass of cyanidin-3-O-glucoside, 449.2 g / mol; DF is the dilution factor; ε is the extinction coefficient of cyanidin-3-glucoside (C3G), 26900 L·mol⁻¹. -1 ·cm -1 L represents the optical path length, which is 1 cm.

[0040] The anthocyanin content in each embodiment and comparative example is as follows: Figure 1 As shown, the anthocyanin content of the examples was significantly higher than that of the comparative examples. The initial anthocyanin content of the examples was 335.8 mg / L. Comparison with comparative examples 3 and 4 confirms that extracting fruit pomace with coconut juice and using it as a fermentation feed can improve the anthocyanin extraction rate from the pomace, avoid strong acid hydrolysis of anthocyanins, and increase the anthocyanin content in the beverage.

[0041] 3. Antioxidant properties (1) Determination of DPPH free radical scavenging rate Prepare 1.75×10 with ethanol -4 Take 2 mL of a mol / L DPPH solution, dilute it to a certain concentration to dissolve the analyte, mix thoroughly, and let stand for 30 min. Measure its absorbance at 517 nm.

[0042]

[0043] In the formula: A i The absorbance of 2 mL of DPPH solution and 2 mL of sample solution; A j 2 mL of sample extract The absorbance of 2 mL of DPPH solution with 2 mL of ethanol; Ac is the absorbance of 2 mL of DPPH solution with 2 mL of ethanol.

[0044] Determination of ABTS free radical scavenging rate Take 1 mL of sample solution diluted to a certain concentration, and add 3 mL of ABTS+ solution (7 mM ABTS solution and 2.45 mM K2S2O8). Mix in equal proportions and react overnight (12h-16h) to prepare ABTS stock solution. Adjust the absorbance of the ABTS reaction solution at 734nm to 0.70±0.02; shake for 30s, react at room temperature in the dark for 60min, and then measure the absorbance at 734nm.

[0045]

[0046] In the formula: Acontrol is the absorbance value of the control tube; Atest is the absorbance value of the sample to be tested.

[0047] Antioxidant capacity such as Figure 2 As shown, the DPPH scavenging rate and ABTS scavenging rate of the embodiment are both above 79%, which have significant antioxidant effects, while the comparative ratios are lower than those of the embodiment. This is closely related to the high anthocyanin content of the embodiment.

[0048] 4. Stability All finished products were sealed and stored at 25°C in the dark for 30 days. Anthocyanin retention rates were measured at 0 and 30 days. Anthocyanin retention rate (%) = Anthocyanin content after 30 days of storage / Initial anthocyanin content × 100%; The higher the retention rate, the more stable the color protection system.

[0049] The results are shown in Table 2. The anthocyanin retention rate of Example 1 reached 86.3%, while all comparative examples were below 80%, which was far lower than that of Example 1. Comparative examples 3 and 4 showed a significant increase in anthocyanin degradation rate due to the lack of coconut milk. Secondly, comparative example 1 also showed a greater loss of anthocyanins due to the lack of a protective agent.

[0050] Table 2. Anthocyanin retention rate and probiotic viable count in the samples.

[0051] 5. Live probiotic count The total bacterial count was determined according to GB4789.2—2022, "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Colony Count".

[0052] As shown in Table 2, the viable count in Example 1 was 3.2 × 10⁻⁶. 8 Except for Comparative Example 6, the viable bacterial counts in the other five comparative examples were all concentrated around 10 CFU / mL. 6 The magnitude of the difference is likely due to the absence of coconut milk substrate in comparative samples 3 and 4, which reduces the sugar and carbon source in the fermentation system, limits the proliferation of probiotics, and makes the probiotics in the comparative samples more susceptible to inactivation during processing.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a blueberry complex beverage rich in anthocyanins, characterized in that, Includes the following steps: S1. Blueberries are soaked in the soaking solution and then frozen for later use. When using, they are taken out and thawed slowly at room temperature in a sealed container. They are then stirred to prepare blueberry puree. The puree is filtered to obtain blueberry juice and blueberry pulp. S2. Adjust the pH of the coconut juice, add chitosan and stir to dissolve it as a solvent for blueberry pomace extraction, add it to the blueberry pomace, stir to extract, filter and collect the coconut juice extract; S3. Sterilize blueberry juice, adjust pH, inoculate with compound probiotic agent, ferment at constant temperature, add coconut juice extract, continue fermentation, and obtain mixed fermentation liquid after fermentation is completed; S4. Filter the mixed fermentation liquid to obtain compound blueberry juice, add resistant dextrin, homogenize and bottle to obtain blueberry compound beverage.

2. The method for preparing a blueberry complex beverage rich in anthocyanins according to claim 1, characterized in that: The soaking solution in step S1 consists of 2.0-3.0 wt.% trehalose, 0.15-0.25 wt.% ascorbic acid, 0.08-0.12 wt.% grape seed extract, 0.1-0.18 wt.% wheat extract, and the remainder is water.

3. The method for preparing a blueberry complex beverage rich in anthocyanins according to claim 1, characterized in that: In step S1, the soaking time is 30-60 minutes; the mass ratio of blueberries to soaking liquid is 1:(1-2); and the thawing time is 2-3 hours.

4. The method for preparing a blueberry complex beverage rich in anthocyanins according to claim 1, characterized in that: In step S2, the pH is adjusted to 3.5-4.0; the amount of chitosan added is 0.1-0.2 wt.% of coconut juice; the mass ratio of blueberry pomace to coconut juice is 1:(3-5); the stirring and extraction speed is 500-800 rpm, and the time is 3-5 h.

5. The method for preparing a blueberry complex beverage rich in anthocyanins according to claim 1, characterized in that: In step S3, the pH is adjusted to 5.5-7.0; the compound probiotic agent includes Lactobacillus plantarum, Lactobacillus acidophilus, and Bifidobacterium bifidum, and the viable count of the compound probiotics in the blueberry juice is 1×10⁻⁶. 6 -1×10 7 CFU / g; constant temperature fermentation temperature is 35-38℃, time is 6-8h; the amount of coconut juice extract is 20-25wt.% of blueberry juice, fed in for 8-10h; continuous fermentation time is 60-72h.

6. The method for preparing a blueberry complex beverage rich in anthocyanins according to claim 5, characterized in that: The ratio of viable counts of *Lactobacillus plantarum*, *Lactobacillus acidophilus*, and *Bifidobacterium bifidum* is (4-6):(2-4):

1.

7. The method for preparing a blueberry complex beverage rich in anthocyanins according to claim 1, characterized in that: In step S4, the amount of resistant dextrin added is 1-3 wt.% of the compound blueberry juice.

8. A blueberry complex beverage rich in anthocyanins prepared by the preparation method according to any one of claims 1-7.

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